Final Report Summary - MODCONS (DEVELOPMENT OF MODULAR CONSTRUCTION FOR SUSTAINABLE DESIGN, STABILITY AND SEISMIC APPLICATIONS)
Executive Summary:
MODCONS is a research project funded by the European Commission under the Framework Programme 7 (FP7) to support small and medium sized enterprises (SMEs). The project is aimed at developing and extending the use of modular construction systems in the residential building sector in the participating countries of Spain, Finland, Portugal and the UK. The work involves the preparation of design guidance in accordance with European standards and Eurocodes that will be supported by physical testing, structural modelling, and will lead to building designs for a variety of medium and high density applications.
Modular construction is used in housing and residential buildings because it is fast to construct and of high quality. The purpose of the MODCONS project was to provide the research necessary to extend two types of modular building systems into higher rise building applications where means of providing stability and in some areas, seismic resistance are very important. In addition, the project has led to quantification of the sustainability benefits and acoustic performance, which affect the use of modular construction in the residential building sector. The overall project objective is the development of new and innovative products to enter the market in a short to medium term.
With the information gained, it was possible to develop design guidance to support the use of these modular systems and to create new markets in high-rise and mixed use buildings. The research involved full-scale physical tests on modules and on elements of modules, which is supported by finite element analyses as well as on-site measurements of performance. The research covered the basic structural performance of the modules and their connections and in particular, their robustness to removal of supports. This also simulated the loss of support and tying action in seismic events.
The project partners are SCI, who is Coordinator of the project, FutureForm/Renascent, HTA Design, NEAPO, Technical University of Tampere, Tecnalia, AST, IA3, CoolHaven and University of Coimbra. The project started in January 2013 and was completed in November 2015.
The project was divided into seven work packages.
• WP1: Design and Physical Tests on Modular Systems. This work package concentrated on the preparation of application rules for design in modular construction using steel technologies, which takes account of the nature and practicality of the construction system.
• WP2: Emerging Themes and Building Typologies for Multi-storey Modular Buildings. This work package developed a diverse range of innovative typologies for modular residential buildings. An important task was to understand future demands and therefore to create building typologies that respond to these needs.
• WP3: Seismic Design of Modular Buildings. In this work package, various scenarios and intensities of seismic events are considered which are modelled statically by progressive ‘failure’ of the connections between the modules. Strategies to prevent collapse of modular buildings in severe seismic events are evaluated.
• WP4: Sustainable Design of Modular Buildings. The scope of work was divided into four parts; i) Quantification of the sustainability benefits of the construction process, ii) Quantification of the operational energy benefits of modular construction, iii) Effective integration of renewable energy technologies in modular construction, iv) Life cycle assessment (LCA) and embodied carbon analysis.
• WP5: Acoustic Design of Modular Buildings. The objective was to improve the acoustic characteristics of the modular systems in compliance with basic regulatory requirements, and then to achieve 3 and 5 dB improvements in acoustic insulation based on the double layer nature of modular systems.
• WP6: Dissemination and Exploitation Tasks. The objective of the dissemination task was to publicise the information obtained from the project and to manage the exploitation of the results.
• WP7: Management Tasks. The objective of WP7 was to facilitate achievement of the overall project objectives with regard to cost, quality and time.
The results of the project show that there is considerable scope for increased use of modular construction in high-rise buildings. Modular systems can be designed to satisfy all the required Regulatory requirements and have significant sustainability advantages.
Project Context and Objectives:
The purpose of the MODCONS project was to provide the research necessary to extend two types of modular building systems into higher rise building applications where means of providing stability and in some areas, seismic resistance are very important. In addition, the project has led to quantification of the sustainability benefits and acoustic performance, which affect the use of modular construction in the residential building sector. The overall project objective is the development of new and innovative products to enter the market in a short to medium term.
The current market for modular construction is relatively small but the potential market is much higher. In the UK, for example, 8000 modules are manufactured in the residential sector as a whole which includes student residences, hotels and military accommodation. Approximately 2,000 modules per year are manufactured directly for the private and social housing and residential markets and a large proportion of this output is in apartments. Typically two modules create an apartment of 60 m2 floor area. Therefore the 2000 modules create 1000 individual apartments which is approximately 1% of the current UK house building market. However, modular construction has achieved a penetration of over 30% in the student residence and out of town hotel markets, indicating that the underlying economics are strong when the speed of construction is taken into account.
In Japan, the market for modular housing reached 100,000 modules per year and this was focussed on high quality housing with a high degree of customisation. Seismic design is very important and most modules are constructed with welded frames so that they are rigid under seismic actions. The modular systems that were developed in the MODCONS research also possess a high level of resistance to horizontal actions due to their nature of construction.
It is considered that the economic use of modular construction is strongest where the economic imperative is to build quickly and to a high level of environmental performance. Government initiatives to reduce operational carbon in buildings will add to this imperative.
The housing market across Europe has fallen to 50% of what it was in 2007, but social housing was less affected by the economic recession. In social housing, clients are most receptive to the benefits offered by modular construction. In particular, the high-rise social housing sector is one where the benefits of modular construction can be realised. It is estimated that approximately 50% of all building in the residential sector is for buildings of more than 3 storeys and therefore a 10% market share would correspond to a 5% overall market. The current EU housing market is close to 1 million houses per year, but it is estimated that the underlying demand for housing is close to 20 million because of an ageing population, more single people, and poor quality housing in many regions.
Since the start of the MODCONS project, the housing sector has started to expand following the recession. Therefore, the potential market for the developed modular systems in during the MODCONS project is expected to grow. Importantly there are opportunities to expand the use of modular construction in countries participating in MODCONS but also other EU countries such as Italy, Poland and France, and to license the technology in the Far East and India.
The as-built cost of a module is around ~1,000 Euros per m2 floor area and so a 25 m2 module has a delivered cost of around 25,000 Euros, when installed, serviced and clad the completed cost of the building is about 15,000 Euros/m2. The potential new markets for modular construction arising from this research could be up to 30 million Euros per year for the SME partners. The route to market is based on a greater realisation of clients of the benefits of modular construction and the ability of the modular industry to deliver a range of solutions using standardised components.
The project was divided into seven work packages each with their own individual objects which when combined with each other enable the overall project objectives to be achieved.
Work Package 1: Design and Physical Tests on Modular Systems for High-Rise Buildings in Accordance with EN 1993.
The main objective of WP1 was to concentrate on the preparation of application rules for design in modular construction using steel technologies, which takes account of the nature and practicality of the construction system. The design guidance is based on the principles of Eurocode 3 for steel structures, Eurocode 1 for loading (actions) and EN1090-2: Execution of steel structures. The output guidance is based on physical tests and with supporting finite element analyses (FEA) of the tested systems.
Work Package 2: Emerging Themes and Building Typologies for Multi-storey Modular Buildings.
The objective of WP2 was to develop a diverse range of innovative typologies for modular residential buildings. An important task was to understand future demands and therefore to create building typologies that respond to these needs. The building typologies also take into account of the structural characteristics investigated in WP1. This Work Package has involved close participation of architectural practices experienced in modular construction.
The scope of work will develop residential building typologies using modular construction, which takes account of the construction system, spatial requirements, Regulations and planning standards in various countries, such as fire safety, circulation space and disabled access.
Work Package 3: Seismic Design of Modular Buildings.
The objective of WP3 was to consider various scenarios and intensities of seismic events which have been modelled statically by progressive ‘failure’ of the connections between the modules. Dynamic models will be performed to establish the natural frequency of the assembly of modules taking account of the ‘spring’ connections. The compatibility of equivalent static and dynamic models was investigated in order to develop design rules for the stability of modular buildings in seismic action.
Strategies to prevent collapse of modular buildings in severe seismic events were evaluated, such as by enhancing the resistance of the connections or by connecting the modules to intermediate ‘strong’ points via a separate structural frame. In high–rise buildings, it is sometimes necessary to introduce stiff braced floors, so that progressive failure of a large number of modules is prevented. This strategy is dependent on the precise building form.
Work Package 4: Sustainable Design of Modular Buildings.
The objectives of WP4 were divided into four parts:
• Quantification of the sustainability benefits of the construction process, based on measures such as; site impacts and disruption to the neighbourhood, safety, transport, waste reduction and recycling, use of recycled materials etc.
• Quantification of the operational energy benefits of modular construction and particularly comparison of design versus as–built operational energy use and other performance measures, such as over-heating and effective ventilation.
• Effective integration of renewable energy technologies in modular construction, which may be part of the module or attached to the modules.
• Environmentally conscious design solutions for modular buildings in terms of architecture.
Work Package 5: Acoustic Design of Modular Buildings.
The objective was to improve the acoustic characteristics of the modular systems in compliance with basic regulatory requirements, and then to achieve 3 and 5 dB improvements in acoustic insulation based on the double layer nature of modular systems, as follows;
• Examine the details of the modular systems in terms of control of airborne and impact sound transfer, taking into account the module to module connections
• Develop an adapted prediction method for the acoustic design of modular buildings
• Carry out laboratory measurements of the acoustic performance of modules relative to adjacent modules
• Evaluate the field performances of modular buildings in relation to laboratory measurements, and investigate any significant differences
Work Package 6: Dissemination and Exploitation Tasks.
The objective of WP6 is the dissemination task and is to publicise the information obtained from the project in terms of:
• Architectural information describing the building typologies and details for high-rise and mixed use buildings
• Structural design guidance on high-rise and mixed use buildings to Eurocode 3
• Seminars to present the results of the project
• Case studies on buildings using the developed technologies
• Sustainability guidance on modular construction
It was also necessary to manage the exploitation of the results of the project through a specific task, and to publicise the work at appropriate stages of the project and on completion.
Work Package 7: Management Tasks
The objective of WP7 is to enable the project to achieve the overall project objectives (development of new and innovative products to enter the market in a short to medium term) with regard to cost, quality and time, the management tasks required:
• Organizing the activities of the project partners and solving potential conflicts to carry out the project activities in due time according to the project programme.
• Acting as the interface between the project participants and the European Commission.
• Performing the coordination and organization of the intellectual property of the results.
• Coordinating and contributing to the technological transfer of the results.
The results of the project show that there is considerable scope for increased use of modular construction in high-rise buildings. Modular systems can be designed to satisfy all the required Regulatory requirements and have significant sustainability advantages.
Project Results:
The final results of the project will enable the companies involved to develop their products and produce innovative solutions within the modular construction sector. All work packages have resulted in improved design methods or levels of information that can be used by SMEs on future construction projects. The solutions adopted for each construction project is selected on an individual basis and tailored to suit the specific needs of the client and location. The work undertaken during MODCONS will enable solutions for future projects to be more accurately designed in terms of their structural resistance, seismic design, acoustic insulation, sustainability benefits and architectural form.
Work Package 1
The scope of work in WP1 was divided into the following tasks: Finite element analyses of modules under various actions and support conditions. Tests on light steel walls in modular construction in compression and shear. Module connection tests. Full-scale module tests and analysis. Structural guidance for modular systems.
Some of the main results and conclusions from WP1 are: The loss of a corner support is the critical case, especially where there are significant openings in the side walls. Modules can redistribute actions and remain stable (with significant distortion) when the corner support is removed. Lining materials (boards) provide a significant enhancement (20% to 40%) to the module stiffness. Plasterboard attached to light steel sections can improve compression resistance by up to a factor of two. With appropriate horizontal bracing, significant tie forces can be transferred by connection details (i.e. at the module corners). Eurocode 3 with supporting test data (which is system specific) can be used for the structural design of modular systems and buildings.
The final deliverable of WP1 is D1.6 which presents structural design guidance for modular buildings. The guidance is based on the findings and conclusions from the preceding activities of Work Package 1 of the MODCONS project in addition to generic design guidance from the Eurocodes. The guidance is presented so that it is directly applicable to high to medium rise modular buildings.
The design guidance addresses the key structural considerations required for a modular building including; loading, structural robustness, connection design, member design, resistance to uplift and lateral stability.
The structural design of the light steel modules is carried out by the modular manufacturers or their consulting engineers. They have the experience of their own particular systems and have developed many local details, including connections between the modules, connections to foundations, and local strengthening at lifting points. Thus, the role of the client's consulting engineer will often be confined only to site-specific items such as foundations and the co-ordination of the complete structural package.
The arrangement of the modules in plan and elevation also influences the load paths and many alternative configurations are possible without compromising structural efficiency.
The following types of modules may be used in the design of buildings using either fully modular construction or mixed forms of steel construction:
• 4-sided modules – designed to transfer loads continuously through their longitudinal walls, usually with closely spaced wall studs.
• Partially open-sided modules – 4-sided modules designed with partially open sides by introduction of corner and intermediate posts.
• Open-sided (corner supported) modules – designed to provide fully open sides by transfer of loads to the corner posts.
• Non-load bearing modules – similar form to fully modular units, but not designed to resist external loads, other than their own weight and the forces exerted during lifting (e.g. bathroom pod).
• Mixed modules and planar floor cassettes – floor cassettes span between load-bearing modules.
The modular systems studied during the MODCONS project are 4-sided modules with load bearing longitudinal walls, with closely spaced wall studs. Therefore, the guidance in D1.6 is primarily aimed at this type of construction.
From a series of tests carried out during MODCONS to determine the shear parameters for the FutureForm modules, the characteristic shear resistance of a bare steel panel and characteristic shear resistance of a plaster-boarded panel have been determined. The resistance values are not provided here as they are confidential. A partial factor of 1.25 should be used to obtain the design resistances of these panels. In order to allow for long terms effects, it is also recommended that the contribution of the plasterboard to the design resistance does not exceed 50% of that of the bare steel panel, so that the bare steel panel can resist serviceability loads if the plasterboard is damaged or removed for some reason during the life of the building.
The values determined are for panels without openings. The shear resistance and shear stiffness values for panels with openings will be significantly lower than those for solid panels. In all cases where plasterboard is used to provide restraint, stability, strength or stiffness to a light steel structure an accidental limit state check should be carried out on the basis that the plasterboard is not able to provide any enhancement to the light steel frame. This will ensure that in a situation where plasterboard is damaged or removed then the light steel structure will still be able to resist the loads from an the accidental limit state condition.
Similar calculations have been carried out to determine resistances for Cool Haven wall panels. However, in the Cool Haven system, OSB sheathing board is utilised. Tests were carried out during MODCONS to determine the shear strength of the connection between the steel profiles and the OSB by self-drilling screws. A numerical model was produced, which was calibrated against the experimental results. The numerical model was in close agreement with the test data and can be used to determine the performance of steel to OSB board screwed connection.
Light steel wall studs are used in conjunction with plasterboard, and often sheathing boards, to form a load-bearing wall panel. The presence of the boards provides a degree of lateral restraint to the studs, which may be utilized when calculating their buckling resistance. However, the level of restraint must be verified by testing, as was carried out during the MODCONS project. Testing of the FutureForm system has shown that a reduced buckling length may be used for boarded walls due to the presence of the boards and the fixity from wall stud connections to the floor joists.
Light steel sections are susceptible to torsional-flexural buckling, in addition to pure flexural buckling. If torsional-flexural buckling occurs at a lower magnitude of load than flexural buckling, this mode of failure will govern the resistance of the member. This is reflected in the design rules, in which the elastic critical buckling load used for design is taken to be the smallest of the elastic critical buckling loads for flexural buckling, torsional buckling and torsional-flexural buckling.
It has been shown by testing that the design procedure of EN 1993-1-3 by be used with the following modifications for the FutureForm system. Effective length factors may be applied to minor axis buckling of the C sections in the wall frames. The effective length factors derived for the system in MODCONS are confidential and therefore they are not published here. There are values for a bare steel frame and another factor for frames with plasterboard fixed internally.
The effective length factors are applicable for wall stud size of 70 x 1.2 mm thick. The design method may be used for other design cases, provided that the stiffness of the floor joists is increased in proportion to that of the C sections in the walls. The fixity of wall elements to floor and ceiling elements also enable the wall deflections to consider a reduction over the theoretical method for a nominally pin ended element.
The tests on the NEAPO system looked at the use of an innovative all-metal sandwich panel. The panels are used to fabricate modules for residential and other types of buildings. The modules are fully equipped with all their finishes and with mechanical systems (HVAC) needed in the building. The modules were fabricated by Neapo Oy.
The main goal was to search the design rules for these kinds of new panels mainly for European markets. In this study the design rules for heavily compressed and lightly loaded with bending moment (wall panels) was one main topic. Another scope was to define the design values for typical panels in shear loading used for stabilising buildings as diagraphs against lateral loads originating from imperfections, wind and seismic actions. The goal was to define the stiffening effects of boards (gypsum and OSB) screwed on the surfaces of the panels. The stiffening effects deal with the increase of the resistance and stiffness of the panels against axial and shear loads. The goal with stiffening is to enlarge the usability of the panels for higher buildings than today.
The rules in present standards do not cover the structural design of the panels. Tests were planned to validate the developed design rules. Tests were performed and the design rules were developed for practicing engineers to be used in building projects. One main principle in this study was, that the existing European standards, Eurocodes, are the reference standards and the new design rules should be in accordance with those standards. This strategy enables the further development of Eurocodes for these structures, and designers understand the design philosophy, enabling rapid implementation in practice.
The new design method for the interaction of high axial compressive force and small bending moments was developed. The safety level was shown to be as required in Eurocodes using the material safety factor for yielding and for flexural buckling of 1.0 as is recommended in Eurocodes and used in most countries in Europe. The loading case is typical for wall panels. The design method includes the resistances of bare all-metal sandwich panels, and panels stiffened with boards on compressed side or on both sides. The safety factor was shown to be smaller than 0.95 in all cases. The tests and the validations were done for extremely thin-walled wall panels (nominal thickness 0.7 mm), and for medium thin-walled panels (1.0 mm).
The same panels were tested for shear loads in the specific test frame made for these tests. The goal was to define the characteristic shear loads for the panels to be used in stabilising the buildings against lateral loads. The safety level was adjusted applying the standard EN 1993-1-3, Annex A, for the use in European markets. The design values are presented for two types of panels (nominal thickness 0.7 and 1.0 mm) without stiffening boards, including stiffening boards on one side and stiffening boards on both sides of the panel.
The tests showed high potential of the panels to resist axial and shear loads. Also the ductility of the panels in these loading cases was high. It is a desire of the authors that the results mean better competition ability of modular buildings made of these panels in the building sector.
Work Package 2
The scope of work in WP2 was divided into the following tasks: Modular system for European residential market. Building typologies and apartment arrangements using modular construction. Building typologies for high-rise buildings. Building typologies for mixed-use buildings, and finally; Architectural guidance on the developed systems.
Some of the main results and conclusions from WP2 are: Modules must be of an appropriate size for transportation, and a practical limit is 4.3m wide. Modules can be used effectively for modification of existing buildings e.g. roof top extensions. Modular systems can be used for all types of residential building, and 75% of all buildings in Europe are used for domestic purposes. With inventive architectural design, modular construction is extremely versatile and satisfies all the requirements of modern buildings.
Functional considerations have strong influence on the architectural design of modular buildings and especially residential and mixed use buildings. Functional requirements may be separated into those influenced by:
• Regulatory requirements for loading, thermal and acoustic insulation and fire safety.
• Performance and spatial requirements of the client, based on the use of the buildings, and influenced by mixed uses of the space.
• Site related constraints that influence the building layout, access, means of escape, as well as the means of construction.
The assembly of modules into complete buildings brings with it issues of stability, robustness, services distribution, attachment of cladding, access and circulation space, means of escape etc., which are the responsibility of the client’s architect.
The architecture of the building is directly related to the repetitive use of essentially similar 3-D components. Therefore, the following architectural aspects should be addressed in the concept stage of design and in planning, and require dialogue with the chosen modular supplier. These aspects should follow through into Regulation approvals and requirements for structural design and servicing distribution.
The following sections describe the Regulatory requirements and other issues that influence the design of buildings using modular construction, and cover:
• Energy efficiency.
• Acoustic insulation.
• Fire safety.
• Services distribution.
• Transportation.
The servicing strategy is also linked to the choice of the plan form, as although the modules are fully serviced in manufacture, the horizontal and vertical routing of services has to be considered carefully. In this respect, corridors provide zones for horizontal service distribution and access for maintenance.
In D2.2 detailed information is provided relating the regulatory requirements in different countries across Europe. Requirements considered include: energy efficiency, air-tightness, fire safety, means of escape, transportation limits.
Countries included are: UK, Finland, Sweden, France, Germany, Spain, Belgium, Italy Netherlands, Denmark and Portugal.
The report D2.4 presents an investigation into the architectural use of modules for mixed use residential and commercial buildings. Architect HTA Design has designed typical modules for various apartment types and sizes that have been used within the dimensional requirements of mixed use buildings. A number of standardised types that are chosen to meet many spatial and regulatory standards in the EU. Typical dimensions are shown based on a 300 mm grid.
Some of the general design requirements are:
• Modules are generally 3.6 m wide internally (and nominally on a 3.9 m grid, allowing for the wall dimensions and gaps between the modules). In practice, the FutureForm module are 3.85m wide when allowing for gaps. Module sizes are suitable for transportation without additional escort.
• Module lengths are variable, and range from 6 to 16 m, dependent mainly on transportation (and particularly turning into local roads). Modules may be manufactured with a central corridor.
• Load bearing side walls of modules align vertically and modules are supported by beams at the podium level.
• Internal wall heights are taken as 2.4 m, but can be varied. Externally, the module height is taken as 0.45 m plus the internal height, i.e. 2.85 m, allowing for the combined floor and ceiling depth.
• Open ends to the modules can be created by inclusion of a rigid steel ‘picture frame’ using Rectangular Hollow Sections. A nominal 100 mm ‘return’ is allowed on the end walls at doors and window openings. Large widows may be created depending on the stability strategy for the modules.
• Service connections are made generally at the corners of the modules and may be accessed from the corridors or other suitable spaces for maintenance. The vertical service routes are made through the module floor and ceiling at these locations.
• Any form of roof may be used, which may be supported either by the load bearing side walls or by the façade walls.
• The self-weight of a fitted out module is typically 8 to 10 tonnes, which is suitable for lifting by a 200 Tonne crane with a long boom for high rise buildings.
For the mixed use buildings with car parking at basement level, the columns are located on a grid, which is suitable for three car parking spaces between the columns. The building width is suitable for modules located either side of a corridor and also for car parking with a central aisle.
Intermediate levels may be used for office or retail space with columns at 5 m, 7 m and 5 m spacing across the building, or alternatively, the construction of a 17 m clear span leads to maximum efficient use of the space below. However, the column-free podium structure is more expensive than the structure with internal columns and would only be considered for high-value projects.
The commercial level is accessed from ground level and so does not require a lift. If additional floors of office space are required, then an additional independent access to the residential levels should be included, which may require a separate core. This type of solution is practical for buildings with 4 to 8 levels of residential space above 2 to 3 levels of commercial space. The optimum is likely to be 4 to 6 levels of residential space above to avoid excessive loads on the podium structure.
The following estimated member sizes may be used as guidance for the supporting steel podium structure:
• For a 6.5 m internal beam span at the podium level, an IPE 450 beam or 457 x 191 x 98 kg/m UB in S355 steel may be used to resist the applied moment from 6 floors of modules above when acting compositely with the floor slab. For a 5 m span, a lighter beam of the same depth may be used.
• For the 7.8 m span primary beams that are parallel to the façade and support adjacent 5 m and 6.5 m beam spans, an IPE 600 beam or 610 x 229 x 140 kg/m UB in S355 steel may be used when acting compositely with the floor slab.
• For the long span solution, with the car parking below, the spans may be reduced to about 12 m next to the braced core and could therefore be lighter.
• For a 16.5 m beam span, a 914 x 305 x 258 kg/m UB or an IPE 800 beam fabricated into a 1000 mm deep cellular beam with regular 450 mm deep openings may be used when acting compositely with the floor slab.
• For the long span solution, a 7.8 m span primary beam along the perimeter of the building supporting the 16 m span beam an IPE 800 or 762 x 267 x 173 kg/m UB beam may be used at the perimeter of the building when acting compositely with the floor slab.
Deliverable D2.5 is the dissemination of architectural guidance. This was the preparation of typical architectural arrangements of modules in various medium- and high-rise building forms, and their associated design details. This information will be used to support the practical use of the developed modular systems in new residential markets. In addition, D2.5 is the output which focuses on presenting guidance for architects on the building typologies obtained from the earlier tasks in WP2 that can be used in the planning of modular buildings.
The results include:
• Preparation of illustrations of the optimised design of apartments based on standard module sizes, and adaptation of these layouts for various building shapes.
• Preparation of illustrations of arrangements of modules in high-rise buildings, taking account of the circulation space in and around the building core.
• Preparation of illustrations of modular residential buildings over commercial space and car parks taking account of the access to the residential levels, car parking, means of escape in fire etc.
The architectural guidance document will be printed and disseminated to architectural practices and other groups who may consider the use of modular systems for building solutions.
Work Package 3
The scope of work in WP3 was divided into the following tasks: Finite element analyses (FEA) to Eurocode 8 and dynamic modelling of modular buildings. Finite element modelling of mixed use buildings. Strategies for seismic design of modular buildings.
Some of the main results and conclusions from WP3 are: Structures with modules supported on a podium structure perform well in seismic events, even if one column of the podium is assumed to be ineffective. High rise buildings generally require a separate bracing system or concrete core, which changes the load transfer between the modules. Pre-stressed bolted connections between modules can be twice as effective for energy absorption during seismic loading. Modules with structural hollow section rigid frames perform well in seismic events.
Report D3.1 of MODCONS addresses the behaviour of the FutureForm modular system under lateral loading and seismic actions. The analysis is based on a finite element model using the program, ANSYS, in which 4 and 8 storey building using 3 dimensional modules were analysed under various loading scenarios. The 3D modelling of a single module is presented in WP1.1 and the same model was used to analyse medium-rise modular buildings consisting of:
• A horizontal group of 4 modules of 3.6 m width x 7.6 m length.
• 4 and 8 storey buildings using the same group of 4 modules on plan.
• Bare steel and boarded modules using bracings to represent the stiffening effect of the boards.
• Loss of support to one corner of the 4 storey group of modules to represent damage after a seismic event.
No central corridor was included in these analyses as a single block of modules represents the worst case of design in which the modules are accessed by an external walkway. The cases analysed were for performed both for bare steel modules using 1.2 mm thick C sections for the vertical load-bearing elements, and modules with bracing representing the stiffening effect of the internal boards. It was found that the lateral deflection of the boarded modules was reduced by 30 to 50% relative to the bare steel modules.
A response spectrum analysis of the seismic forces was carried out to Eurocode 8 in order to determine the horizontal forces for the case of 20% ground acceleration. These seismic forces are compared to the case of wind loading in order to determine the effect of seismic design on the forces in the connections between the modules. It was found that the horizontal and vertical ties forces may be taken as not less than 25% of the factored vertical loading applied to one module.
Based on the results of the finite element analyses of the FutureForm modular system subject to lateral loading and seismic actions, the following conclusions are made:
• The boarded modules are about 30% stiffer than bare steel modules in terms of horizontal actions.
• A group of 4 modules is sufficiently stable for a 4 storey building, but it is recommended that the group of modules is increased to a minimum of 6 for an 8 storey building. No corridor is required for buildings up to 8 storeys high and subject to wind loading up to 1 kN/m2, as the single modules are stable in their long sides.
• The natural frequency of a 4 storey building was 2.2 Hz for boarded modules and this reduced to 1 Hz for an 8 storey building. From the response spectrum method, the base shear for the 4 storey building was 325 kN and 402 kN for the 8 storey building. The difference was relatively small because the stiffer 4 storey building attracted higher seismic forces.
• Connection forces in the ties between the modules were simulated by considering loss of a support after a seismic event. It was shown that the tying forces may be taken as not less than 25% of the factored vertical load acting on a module with a minimum value of 25 kN.
In many parts of Europe, it is required to design buildings for resistance to seismic actions, as presented in EN 1998-1-1: Eurocode 8, according to two methods:
• Response factor method based on the natural frequency of the structure as influenced by the ground conditions.
• Time history method based on an actual seismic event.
The response factor method results in equivalent horizontal forces which can be expressed as a proportion of self-weight of the building. Generally 5% equivalent horizontal load represents a modest seismic event and 10 to 20% equivalent horizontal load represents a more severe event. The first part of WP3 defines the magnitude of these forces for design to EC8 and seismic codes worldwide. Modular structures are stiff but their connections are relatively weak. Therefore, the forces attracted to the connections are crucially important to the stability of modular buildings.
Based on the results of finite element analyses of the FutureForm modular system, constructed from a ground floor podium structure, the following conclusions are made:
• Four or six storeys of modules can be supported on a steel framed podium structure arranged on a column grid of 8.8 m / 7.6 m x 7.2 m in which the side walls of the modules are supported by secondary beams. It is shown that the deflections of the frame are about 30 % lower than the theoretical deflections due to the line loads applied to the beams. This is because of the in-plane stiffness of the walls of the modules.
• This podium structure is stable even after loss of one column due to damage in a seismic event.
• The shorter secondary beams may be replaced by 16.4 m span cellular beams, but in this case, loss of a column leads to much higher displacements.
• The 6 storey podium structure may be stiffened by attaching the corridor between the modules to a concrete core, and it was found that the maximum tie force at this connection was 55 kN, when the modules are subject to seismic actions.
• Modules with rigid end frames using Structural Hollow Sections can be designed up to 8-storeys high, and it was found that the horizontal deflections due to seismic actions are not excessive provided the number of modules in a horizontal group is not less than the number of storeys.
• Mixed modular and steel framed systems were found to be efficient structurally and can be used to create more usable space.
Part of WP3 was to describe the modal spectrum analysis performed on an assembly of 12x4 single line of modules, representing a high-rise modular building, in order to validate the design of the proposed system in accordance with appropriate structural design codes (Eurocode 8).
The results indicate that the following conclusions can be made:
• The steel structure performs properly under the tested range of load conditions. The allowable design limits are not exceeded.
• The results given in the analysis of the influence of the stiffness of the joints show that the variation of the spring constant values does not affect the results of Von Mises stress nor the displacements. This proves that the stability of the modular structure will not be affected when the seismic loads are applied. Therefore the torsional stiffness is not considered a critical factor.
• The results of the buckling analysis of the module show that the loads leading to collapse are very high. Therefore it can be considered that the boards included in the interior and exterior walls as well as floor and ceiling significantly contribute to the bracing of the module.
• The results obtained including the concrete core (see section 5.5.4: “Modular assembly attached to a concrete core”) show improvements with respect to the models analysed without the core. Although the maximum displacement seems to be greater in this case (with the concrete core), it only occurs in specific areas. The total displacements registered on the assembly (that includes the effect of concrete core in the model) are lower in general than those obtained previously. Also, the steel structure performs properly under the indicated load conditions.
• The results obtained in the present analysis allow ensuring the suitable behaviour of the studied structures, according to Eurocode 8 requirements.
A podium structure is often used to support 4 to 8 storeys of modules above. The podium may be designed in steel or concrete. In a steel framed scheme, the beams are placed so that they align with the walls of the modules. In a concrete scheme using a deep flat slab, the modules may be placed in a random pattern on the slab. The relative economy of the two possible schemes was assessed. The economic comparison of the design of the podium structure was based on the following data:
• Columns placed on a 7.5 m square grid below the podium.
• 6 storeys of light steel modules placed on the podium.
The results of this cost comparison study showed that the weight if the steel solution was significantly lighter per floor area at 345 kg/m2 compared to 1335 kg/m2 for the concrete scheme. The steel scheme was also significantly less costly at € 188 /m2 compared to € 240 /m2 for the concrete scheme.
D3.3 extends the principles of seismic design to high-rise modular buildings using a concrete or braced steel core in which the dynamic response is dependent on both the modular and core parts of the building. This is important when considering the ability of the separate stabilising structure to transfer forces in seismic conditions and potentially to relieve the modular components of the high seismic actions. The characterization of connections in terms of energy absorption during a seismic event were defined. A seismic analysis was carried out and a modified pushover analysis repeated the same initial seismic analysis by progressively removing the most stressed connections to the stiffening core until failure.
After reviewing the results, the following conclusions can be made:
• The prestressed connections are more dissipative in terms of energy absorption, doubling the absorption when compared to same connections with non-prestressed bolts.
• Channels are far more dissipative than double angles.
• The steel structure performs properly under the load conditions for the seismic event that was selected for study.
• The results given in D3.3 show that the structure will not collapse until step 13, where 12 supports or connections between the modules have failed.
• Again, the results obtained in the analysis ensure the suitable behaviour of the studied structures, according to Eurocode 8 requirements.
Work Package 4
The scope of work in WP4 was divided into the following tasks: Sustainability benefits of modular construction. Energy performance of modular buildings. LCA embodied carbon and use of renewable energy technologies.
Some of the main results and conclusions from WP4 are: Modular construction is significantly different to traditional construction and therefore it is important that the main contractor on the project is experienced with modular construction. The sustainability benefits of modular construction are: Increased speed of construction (50% faster than concrete frame construction). Reduced site management cost. Improved safety (5 times safer than fully on-site construction). Reduced waste and landfill charges, and more opportunities for recycling. Higher productivity (fewer personnel on site). Reduced disruption to the locality by noise and traffic with fewer deliveries of materials. Renewable energy systems can be integrated into the modules during manufacture.
Report D4.1 presents on–site and factory data during manufacture, installation and construction of a modular residential building compared to site-intensive construction such as a concrete frame with blockwork infill walls. This data is determined for real modular projects and from existing studies. The broad conclusions on the sustainability and economic benefits of modular construction are:
• Cost - modular construction is most economic for larger projects when economy of scale in production and when the benefits of speed of construction are taken into account. For a residential building, financial savings can be 0.5% per month early completion, increasing to 1% for a time-dependent business like a hotel. This equates to a saving of 3 to 6% of the build cost for a 6 month reduction in construction period. The client’s design consultant costs are reduced by up to 2% of the total project cost as the detailed design is done by the modular supplier. Site repairs due to snagging are also reduced considerably. Hence, overall savings of 5 to 9% are possible in modular construction.
• Labour and productivity - the on -site labour in modular construction projects is reduced by up to 50% relative to site-intensive construction and the labour in a modular project is required for cladding and services and the non-modular parts of the building. Combined with the speed of construction, on-site productivity is increased by a factor of 3 to 4 in modular construction.
• Health & safety- safety data suggests that off-site manufacturing is 2 times safer than on -site construction per 100,000 hours. Taking into account the speed of manufacture, off-site manufacturing is therefore 3 to 4 times safer than on -site construction per unit area.
• Speed of construction - the reduction in construction period depends on the proportion of off-site manufacture in the project. For a fully modular building, the reduction in construction period can be 55 to 65% relative to site-intensive construction, such as concrete frame. For mixed construction, such as modules placed on a concrete podium, the reduction in construction period is 35 to 45%.
• Waste generation - various studies have shown that on site waste is reduced by 60 to 95% in modular construction relative to site-intensive construction, where 10 to 15% of materials are wasted by damage and over-ordering. Site waste is mainly due to the non-modular parts of the building, and so wastage rates of 1 to 4% may be taken as being typical in modular construction. The waste in manufacturing is small (1 to 2%) due to efficient ordering of materials, elimination of damage and better working conditions and all factory waste can be segregated and recycled.
• Environmental impacts -the environmental impact of the construction process is directly in proportion to the site activities and the traffic associated with it. Deliveries and personnel on site are reduced by 60% and these activities occur over a shorter construction period, so the overall site impact is reduced by a factor of 3 relative to fully on-site construction. The self-weight of modular construction is about one-third of that of concrete construction and the embodied carbon is 10 to 20% less. Modular buildings have better and more reliable thermal performance and lead to lower operational energy use. Furthermore, modular buildings are fully demountable and their asset value is retained if they are re-used.
• Social responsibility- modular manufacture gives more job security, better working conditions and training in parts of the country where employment is lower than in urban areas, where the modules are installed. This reduces pressure on the availability of local craft skills which is important particularly in London. Disturbance to the neighbourhood during construction is minimised and transport of modules to site can be timed in prior agreement with the police and neighbours.
The objective of WP4.2 of MODCONS was to evaluate the performance of a light steel modular housing scheme and to learn from the building construction and operation and from resident feedback, to inform future projects of a similar type and scale. The results and foreground are summaries below.
The Birchway Eco-Community scheme, which is in Hayes, Middlesex, UK comprises 24 apartments in five two storey blocks. The type of tenure is affordable rent. The buildings were designed achieve Code for Sustainable Homes Level 5, which was relatively advanced at that time.
The buildings were constructed to high thermal insulation and air-tightness standards. In addition, the scheme includes a wood-pellet fired, biomass boiler supplying all apartments on the development, photovoltaic (PV) panels on all five buildings and mechanical ventilation and heat recovery (MVHR) units in all apartments. The buildings have green (sedum) roofs and incorporate rainwater harvesting for flushing toilets.
The buildings were monitored over the winter to determine their total energy use. Meetings were held with the owner, Paradigm Housing Association, the architect, and FutureForm to understand how this project was designed and lessons to be learnt.
It was found that the total heating demand was 99 kWh/m2/year as an average across the 24 dwellings, although the variation was -90% to +90%, indicating that the user pattern has a major effect on the energy use. Of this, the space heating demand was on average 42 kWh/m2/year, which is only 11% higher than the design prediction in the SAP assessment. The energy generation from the photovoltaic panels was in-line with the design prediction and amounted to about 3500 kWh per year for each building, which greatly exceeded the energy required for communal lighting.
The measured air-tightness of all the buildings was 5.26 m3/m2/hr at 50 Pa pressure which is 15% better than the design requirement. The airborne sound reduction was on average 9 dB higher (better) than the Building Regulations Part E which is excellent. The impact sound transmission was on average 12 dB less (better) than the Building Regulations.
The percentage of hours over 27oC in the living room was only 3% and in the bedrooms was only 2%, which shows that over-heating was a low risk over the monitoring period.
Problems were experienced with the operation of the biomass boiler used for the communal heating, which was not part of the modular construction ‘package’ and with the perceived air quality due to the MVHR system that was specified. Overall the satisfaction of the residents with the buildings was good, particularly in relation to the living space of the modular system.
Lessons and recommendations relating to the design and construction based on the experience of this project include:
• Chose a contractor with appropriate experience of the modular construction system and the renewable energy and sustainable technologies to be employed.
• Avoid late design changes wherever possible; this is particularly true for offsite methods of construction, such as modular systems.
• Provide clear demarcation of responsibility between contractors and between parties within the design team particularly with respect to interfaces such as heating systems and air-tightness boundaries.
Assessment of the building fabric of the Birchway dwellings included:
• Air-tightness testing – undertaken for Part L compliance
• Thermal imaging survey
• Acoustic testing – undertaken for Part E compliance.
The target air tightness for the dwellings in this development was an air leakage index (ALI) of 6 m3h 1m 2 at 50 Pa The average air-tightness achieved for the 10 (of 24) dwellings tested was 5.26 m3h-1m-2; ranging from 2.75 m3h-1m-2 to 6.88 m3h-1m-2.
No obvious correlation between floor area and airtightness was observed although the performance of flats in the (larger) Type A buildings appears to be better than those in the Type B buildings. The measured air-tightness results were slightly higher than similar modular projects probably due to poor onsite on-site realignment of some windows by the main contractor.
The thermal imaging survey was undertaken in the winter. This survey showed the good thermal performance of the modules with no serious thermal bridging but identified areas of possible thermal bridging in the non-modular areas, notably at the eaves. Heat lost from the loft areas, which house the hot water storage tanks, was clearly identified.
The results of the airborne sound insulation tests of the walls meet the requirements of Approved Document E and the Code requirements to achieve the maximum four credits under the sound insulation criteria (Hea 2). The test results for the floors also met the requirements of Approved Document E and, with the exception of the floors between two flats, the Code requirements to achieve the maximum additional four credits.
The results of the impact sound insulation tests of the floors meet the requirements of Approved Document E and the Code requirements to achieve the maximum four credits.
Results and conclusions relating to the renewable energy and sustainable technologies are:
• The biomass boiler was a key component of the strategy to achieve CSH Level 5 on this development. Since handover, there have been problems with the biomass boiler and the communal heating system. Water ingress to the pellet store caused problems with the feed and combustion of the pellets.
• The PV systems installed appear to performing relatively well, i.e. in line with the design predictions. Nevertheless, problems have been identified in particular with the inverters.
• The MVHR system installed in the dwellings was a whole house central mechanical supply and extract unit with heat exchanger. It is clear from the residents’ feedback that the ventilation solution was not working as well as might be hoped.
In D4.3 a comparison of the embodied carbon in the building fabric was made between a typical modular residential building using a light steel framework and an equivalent reinforced concrete frame with blockwork infill walls. The study was made for a notional 6 storey building of 13.5 m depth and with a 1.5 m wide central corridor in which the modules were 3.5 m wide. The same grid was considered for a concrete structure of 7.0 m x 7.5 m / 6.0 m grid.
The embodied carbon comparison includes the main components of the building fabric, which are the primary structure in steel or concrete, the walls, plasterboards and other boards, insulation, etc. but does not include windows, services and finishes. The same external cladding was assumed on both buildings, i.e. brickwork for the first four storeys and insulated render above. The impact of the foundations was also assessed.
The results showed that the embodied carbon content of the modular structure is 182 kg CO2e per m2 floor area, and that of the concrete structure with blockwork infill walls is 229 kg CO2e per . This shows that the light steel modular system has a 20% lower embodied carbon and also is only 30% of the total weight of the structure of the concrete frame.
Also included was an investigation into the use of renewable energy technologies attached to or built into the modules in a typical residential building. The technologies investigated are Photovoltaic panels connected to the modules and the use of in-built ducts with embedded Phase Change Materials to reduce over-heating and hence demand for cooling. This application is best suited to modular roofing systems.
Work Package 5
The scope of work in WP5 was divided into the following tasks: Defining the requirements for acoustic design of a modular building. Laboratory measurements of acoustic performances of lightweight elements. Acoustic design of junctions between elements by tests on module junctions. Field tests on real buildings for acoustic performance of modular buildings.
Some of the main results and conclusions from WP5 are: Different parts of Europe demand different levels of sound insulation between rooms. Modular construction systems provide the required level of acoustic performance by at least 5dB. Flanking sound at junctions is reduced by the discontinuous nature of the connections in modular construction. The number, type and thickness of boards used for wall and ceiling linings contribute significantly to the level of sound insulation achieved. The modular system studied achieved excellent acoustic performance in laboratory testing and demonstrated by field testing of completed buildings.
Acoustic regulatory requirements applicable in European countries are expressed in terms of acoustic descriptors considering in situ situations. This implies the need for a preliminary design to meet the acoustic performance of the building systems once implemented in the building. This is the reason why acoustic prediction models are required for the building design in relation to their acoustic performance. There is currently no approved prediction model, validated and included in international regulatory systems for the acoustic performance of lightweight constructions.
Sound insulation is potentially one of the weaknesses of lightweight building systems. It is therefore necessary to conduct a theoretical and experimental study of these systems through a series of constructive simulations, experimental measurements and later by laboratory and field tests. Report D5.1 summarizes the main acoustic requirements for the countries involved in the consortium of this project.
The acoustic insulation provided by a series of typical light steel floor constructions is presented in Table 3 of D5.1. A resilient layer beneath the floor finish reduces both airborne and impact sound transmission. Generally, mineral fibre of 70 to 100 kg/m3 density provides sufficient stiffness to prevent local deflections, but is soft enough to function as a vibration isolator. Mineral wool placed within the depth of the floor and ceiling helps to absorb sound in the cavity between the C sections. Thicker layers of fire resistant plasterboard have higher mass than ordinary plasterboard, thus reducing sound transmission.
Flanking transmissions can add 3 to 7 dB to the sound transfer measured in buildings in comparison to those tested acoustically in the laboratory. To reduce flanking transmission, it is important to prevent the floor boarding from touching the wall studs by including a resilient strip between the wall and floor boarding. Furthermore, in modular construction, the mineral wool insulation and sheathing boards help to reduce flanking transmission.
D 5.2 describes acoustic laboratory tests carried out on the FutureForm system (two walls and two floors), taking into account not only improving acoustic performances, but also optimizing width and costs of the system and preserving other characteristics: e.g. Fire protection, thermal performances, etc.
The alternatives in the floor design have focused on the improvement of impact sound insulation, which also leads to a better airborne sound insulation. It was agreed that the elastic effect of a rubber layer between modules would be tested as its elimination would involve reduction of costs.
It was also decided to test a typical double steel frame wall with two plasterboards on each side and the same with one plasterboard on each side.
The test results and foreground show, the effect of rubber layer does not improve acoustic insulation (airborne and impact) of combined ceiling and floor, as individual element.
By further consideration of the laboratory acoustic results, it can be concluded:
• The wall with 2 plasterboards on each side could be used in the UK, Spain, France and Finland in dwellings separations.
• The wall with 1 plasterboard on each side is considerably less insulating than the other one. This wall would not be enough in dwellings separations for UK and France. For Spanish requirements it is in the limit, it will depend on flanking transmissions. For Finland it would be enough.
• The floors are valid for Spain, UK and France in dwellings separations. Impact sound insulation results are on the limit for Finish requirements.
Results from WP5.3 lead to the following conclusions:
• When designing acoustically modular systems that constitute two enclosures, both the direct path and the flanking paths generated at the junctions have to be studied. The latest can reduce significantly the overall insulation between two rooms.
• In this phase of the project, the flanking transmissions that occur in the junctions of the modular mixed system has been analysed in detail in mock-ups made with 4 steel structure modules.
• From the measurement campaign it has been set that there is a sufficient attenuation in all the junctions analysed. The fact to have multilayer elements, gypsum boards finishes, and so on is positive to assure the discontinuity between modules.
The D5.4 results conclude that the airborne and impact sound insulation measurement results of a modular detached house in Madrid, are found suitable to fulfil noise requirements in Spain.
Standard procedures of new standard ISO 16283 parts 1 and 2 has been compared to low frequency procedure:
• From the airborne sound insulation test between two rooms vertically (one above the other), the low frequency method gives higher result in the spectra for low frequencies and the overall index turns out to be two more decibels for low frequency method.
• From the airborne sound insulation test between two rooms s horizontally (side by side), no difference between the two test methods were observed. This may be because the result has a higher insulation value, and the test method is not having influence in the result.
• From the impact noise insulation test in rooms oriented horizontally (side by side), higher values of impact noise level is obtained by the method of low frequency and the global impact insulation index for 50 Hz is also penalized with the low frequency method
• From the impact noise insulation test in rooms oriented vertically (one above the other), a higher level of impact noise is obtained by the method of low frequency; however, the overall index for both methods is not modified.
Alternative impact sound sources have also been studied in order to study the influence of characterization methods in the lower frequencies.
A series of on-site tests was performed for a modular residential project in west London using the same system as was tested in the laboratory in WP5.2. The results for the 10 floor-ceiling tests and the 10 separating wall tests between different rooms constructed from modules were analysed and the variation in the measured results was found to be small. The airborne sound reduction index Dntw was on average 63dB for floors and 59dB for walls, and in both cases, the low frequency correction factor, Ctr was -11dB. The impact sound transmission of the floors was 49dB. All of these results are significantly better than national regulations. Building design using lightweight modular construction solutions has been shown to comply with acoustic requirements.
Deliverables
A comprehensive set of deliverables have been produced which included detailed scientific and technical data relating the activities carried out and their results and foreground. The deliverables produced in the scientific and technical work packages are:
D1.1 - Report on finite element analyses of modules under various actions and support conditions.
D1.2 - Report on tests on light steel walls in modular construction.
D1.3 - Report on module connection tests.
D1.4 - Report on full-scale module tests for Module type 1.
D1.5 - Report on full-scale module tests for Module type 2.
D1.6 - Dissemination of structural guidance.
D2.1 - Report on modular systems for European residential market.
D2.2 - Report on building typologies and apartment arrangements using modular construction.
D2.3 - Report on building typologies for high-rise buildings.
D2.4 - Report on building typologies for mixed us e buildings.
D2.5 - Dissemination of architectural guidance.
D3.1 - Report on finite element analyses to Eurocode 8 and dynamic modelling.
D3.2 - Report on finite element modelling of mixed use buildings.
D3.3 - Report describing strategies for seismic de sign of modular buildings.
D4.1 - Report on sustainability benefits of modular construction.
D4.2 - Report on the energy performance of modular buildings.
D4.3 - Report on LCA and use of renewable energy technologies.
D5.1 - Definition of requirement s for acoustic design of a modular building.
D5.2 - Acoustic design of lightweight elements. Laboratory acoustic performances of elements.
D5.3 - Acoustic design of junctions between floor elements. Tests on modules and of junctions.
D5.4 - Acoustic performance of modular buildings. Field tests on real buildings.
Potential Impact:
The final results of the project will enable the companies involved to develop their products and produce innovative solutions within the modular construction sector. All work packages have resulted in improved design methods or levels of information that can be used by SMEs on future construction projects. The solutions adopted for each construction project is selected on an individual basis and tailored to suit the specific needs of the client and location. The work undertaken during MODCONS will enable solutions for future projects to be more accurately designed in terms of their structural resistance, seismic design, acoustic insulation, sustainability benefits and architectural form.
The impact of the tasks completed during the dissemination work package (WP6) are: 1) Publicising the information created during MODCONS. 2) Spreading knowledge about the advantages of modular construction e.g. sustainability benefits and architectural options. 3) Promoting the use and possibilities of high-rise modular construction. 4) Making information available on modular buildings through case studies and other information available from the MODCONS website (www.modconsresearch.eu). 5) Informing the construction industry about modular construction and the research that has taken place during MODCONS through speaking at industry events and seminars.
The use and dissemination of the foreground information produced during MODCONS has assisted in achieving the objectives of MODCONS by the promotion of modular systems and the product development of the specific systems researched. The project has produced a large amount of foreground information, which is being disseminated in a variety of methods (e.g. seminars, websites, articles, shows, technical papers, presentations etc.) and being used to the advantage of the project partners. These advantages of modular construction systems will spread to other parts of construction industry as the specialist consultancy knowledge obtained by the partners is used for new clients and customers.
The responses form the dissemination activities have been extremely positive and encouraging for the increased adoption of modular construction. Audiences have been enthusiastic and supportive of the information presented. At several of the events audiences have included representatives from clients and policy making authorities. There are good reasons for an optimistic view on increased use of modular systems to address construction needs in the future.
Since the start of the MODCONS project, the housing sector has started to expand following the recession. Therefore, the potential market for the developed modular systems in during the MODCONS project is expected to grow. Importantly there are opportunities to expand the use of modular construction in countries participating in MODCONS but also other EU countries such as Italy, Poland and France, and to license the technology in the Far East and India.
The potential new markets for modular construction arising from this research could be up to 30 million Euros per year for the SME partners. The route to market is based on a greater realisation of clients of the benefits of modular construction and the ability of the modular industry to deliver a range of solutions using standardised components.
The impact of the technical research work packages (RTD) of MODCONS is summarised below. All work packages have resulted in improved design methods or levels of information that can be used by SMEs on future construction projects. The solutions adopted for each construction project is selected on an individual basis and tailored to suit the specific needs of the client and location.
The work undertaken during MODCONS will enable solutions for future projects to be more accurately designed in terms of their structural resistance, seismic design, acoustic insulation, sustainability benefits and architectural form.
WP1 - Structural design developments for modular systems:
• Improved racking (shear) resistance for walls.
• Design resistances in accordance with Eurocodes.
• Improved compression resistance of wall panels.
• Improved understanding of structural behaviour of modules.
• Improved design solutions for structural robustness.
• Improved solution for distribution of connection forces.
• Design guidance for compliance with Eurocodes.
WP2 - Architectural design developments for modular systems:
• Architectural building typologies for medium-rise buildings.
• Architectural building typologies for high-rise buildings.
• Architectural building typologies for mixed-use buildings.
• Architectural guidance for modular solutions.
WP3 - Seismic design developments for modular systems:
• Guidance on seismic modelling of modular buildings.
• Performance of modular buildings on podium structures in seismic scenarios.
• Performance of modules with rigid steel end frames.
• Performance results of various modular buildings in seismic scenarios.
• Guidance on dissipative systems.
• Strategies for seismic design of modular buildings.
WP4 - Sustainability design developments for modular systems:
• Quantified sustainability benefits of modular construction.
• Case study data for sustainability of modular building projects.
• Sustainability messages for modular construction.
• Energy performance / usage monitoring data for modular building.
• Practical considerations for energy usage in modular buildings.
• Thermal performance data at junctions for modular systems.
• Air-tightness data for modular systems.
• Life Cycle Analysis (LCA) information for modular buildings.
• Embodied carbon comparison for modular and traditional construction.
• Options for incorporation of renewable energy technologies with modular construction.
WP5 - Acoustic design developments for modular systems:
• Acoustic requirements for modular buildings across Europe.
• Guidance on principles of acoustic insulation.
• Laboratory test data for walls and floors of modular systems.
• Improved acoustic design of junctions and interfaces.
• Site based acoustic test data for modular systems.
The dissemination activities that have taken place are reported in detail in the deliverables from Work Package 6. The most relevant deliverables are:
• D6.1 Exploitation management.
• D6.2 Elaboration of diffusion material.
• D6.3 Seminars to promote development of modular systems.
• D6.4 Case studies on modular construction.
• D6.5 Participation in sectorial fairs.
• D6.6 Website report.
• D6.7 Video clip report.
• D6.8 Report on Wikipedia page.
• D6.9 Report on conformity with Regulations.
A list of the dissemination activities and the areas they address is provided in Table 3.1 of Deliverable D7.2 “Final Plan For Dissemination and Use of the Foreground”.
The original dissemination plan included 3 seminars. However, instead of 3 standard seminars, it was considered to be more appropriate and more effective to present at a range of seminars or events with presentation material tailored to suit different types of audience. It was considered that this would be more appropriate for communicating the messages that were required about the development of modular construction systems.
In some cases, presentations were given at existing construction industry events rather than at new events specifically setup to disseminate the information from the MODCONS project. This decision was taken as it was believed that this would enable a larger audiences to be reached at more events in a more cost effective way.
The dissemination activities have been extensive and have included electronic dissemination (e.g. websites, emails and webinars), oral presentations (e.g. at conferences, workshops, exhibitions etc.) and printed dissemination (e.g. magazine articles, project brochures and guidance documents).
The research (RTD) performers of MODCONS; SCI, Tecnalia and Technical University of Tampere and Coimbra University, envisage long term partnership roles with modular system suppliers in the UK, Spain, Finland and Portugal respectively. The foreground research developed during MODCONS will be re-invested in the form of industry guidance, product development and system approvals. This is particularly relevant for aspects of robustness, seismic design and acoustic performance, which could lead to specialist consultancy for the RTD performers and SME consultancy partners.
Each of the technical work packages of MODCONS were aimed at investigating different aspects of the performance of the modular systems. The information gained through each of these work packages will enable the modular manufacturers to obtain more in depth knowledge about how their systems behave under different scenarios.
The module manufacturers will implement this information by making improvements to their systems and their design procedures. These improvements will either be aimed at superior performance or increased efficiency of design, manufacture and construction. Module manufacturers will disseminate these product developments through their own company literature and contractual discussions. The details of many of the findings of the project research are commercially sensitive, and therefore, public release of all the details is not possible. However, many public dissemination activities have taken place during the MODCONS project. The specialist consultancy companies involved in the MODCONS project will also benefit from the knowledge gain during MODCONS. Exploitation of results will enable consultants to assist other companies involved in the modular construction sector with their increased knowledge and experience which has been gained as a direct result of the project. These skills include: Computational modelling of structures, Acoustic performance analysis and prediction, Expertise on modular systems, Structural design and analysis skills, Finite element modelling and Sustainability performance guidance.
List of Websites:
MODCONS website is www.modcons-research.eu
SCI (Project coordinator) Tel: +44 1344636525
Other relevant contact details are provided on the website.
MODCONS is a research project funded by the European Commission under the Framework Programme 7 (FP7) to support small and medium sized enterprises (SMEs). The project is aimed at developing and extending the use of modular construction systems in the residential building sector in the participating countries of Spain, Finland, Portugal and the UK. The work involves the preparation of design guidance in accordance with European standards and Eurocodes that will be supported by physical testing, structural modelling, and will lead to building designs for a variety of medium and high density applications.
Modular construction is used in housing and residential buildings because it is fast to construct and of high quality. The purpose of the MODCONS project was to provide the research necessary to extend two types of modular building systems into higher rise building applications where means of providing stability and in some areas, seismic resistance are very important. In addition, the project has led to quantification of the sustainability benefits and acoustic performance, which affect the use of modular construction in the residential building sector. The overall project objective is the development of new and innovative products to enter the market in a short to medium term.
With the information gained, it was possible to develop design guidance to support the use of these modular systems and to create new markets in high-rise and mixed use buildings. The research involved full-scale physical tests on modules and on elements of modules, which is supported by finite element analyses as well as on-site measurements of performance. The research covered the basic structural performance of the modules and their connections and in particular, their robustness to removal of supports. This also simulated the loss of support and tying action in seismic events.
The project partners are SCI, who is Coordinator of the project, FutureForm/Renascent, HTA Design, NEAPO, Technical University of Tampere, Tecnalia, AST, IA3, CoolHaven and University of Coimbra. The project started in January 2013 and was completed in November 2015.
The project was divided into seven work packages.
• WP1: Design and Physical Tests on Modular Systems. This work package concentrated on the preparation of application rules for design in modular construction using steel technologies, which takes account of the nature and practicality of the construction system.
• WP2: Emerging Themes and Building Typologies for Multi-storey Modular Buildings. This work package developed a diverse range of innovative typologies for modular residential buildings. An important task was to understand future demands and therefore to create building typologies that respond to these needs.
• WP3: Seismic Design of Modular Buildings. In this work package, various scenarios and intensities of seismic events are considered which are modelled statically by progressive ‘failure’ of the connections between the modules. Strategies to prevent collapse of modular buildings in severe seismic events are evaluated.
• WP4: Sustainable Design of Modular Buildings. The scope of work was divided into four parts; i) Quantification of the sustainability benefits of the construction process, ii) Quantification of the operational energy benefits of modular construction, iii) Effective integration of renewable energy technologies in modular construction, iv) Life cycle assessment (LCA) and embodied carbon analysis.
• WP5: Acoustic Design of Modular Buildings. The objective was to improve the acoustic characteristics of the modular systems in compliance with basic regulatory requirements, and then to achieve 3 and 5 dB improvements in acoustic insulation based on the double layer nature of modular systems.
• WP6: Dissemination and Exploitation Tasks. The objective of the dissemination task was to publicise the information obtained from the project and to manage the exploitation of the results.
• WP7: Management Tasks. The objective of WP7 was to facilitate achievement of the overall project objectives with regard to cost, quality and time.
The results of the project show that there is considerable scope for increased use of modular construction in high-rise buildings. Modular systems can be designed to satisfy all the required Regulatory requirements and have significant sustainability advantages.
Project Context and Objectives:
The purpose of the MODCONS project was to provide the research necessary to extend two types of modular building systems into higher rise building applications where means of providing stability and in some areas, seismic resistance are very important. In addition, the project has led to quantification of the sustainability benefits and acoustic performance, which affect the use of modular construction in the residential building sector. The overall project objective is the development of new and innovative products to enter the market in a short to medium term.
The current market for modular construction is relatively small but the potential market is much higher. In the UK, for example, 8000 modules are manufactured in the residential sector as a whole which includes student residences, hotels and military accommodation. Approximately 2,000 modules per year are manufactured directly for the private and social housing and residential markets and a large proportion of this output is in apartments. Typically two modules create an apartment of 60 m2 floor area. Therefore the 2000 modules create 1000 individual apartments which is approximately 1% of the current UK house building market. However, modular construction has achieved a penetration of over 30% in the student residence and out of town hotel markets, indicating that the underlying economics are strong when the speed of construction is taken into account.
In Japan, the market for modular housing reached 100,000 modules per year and this was focussed on high quality housing with a high degree of customisation. Seismic design is very important and most modules are constructed with welded frames so that they are rigid under seismic actions. The modular systems that were developed in the MODCONS research also possess a high level of resistance to horizontal actions due to their nature of construction.
It is considered that the economic use of modular construction is strongest where the economic imperative is to build quickly and to a high level of environmental performance. Government initiatives to reduce operational carbon in buildings will add to this imperative.
The housing market across Europe has fallen to 50% of what it was in 2007, but social housing was less affected by the economic recession. In social housing, clients are most receptive to the benefits offered by modular construction. In particular, the high-rise social housing sector is one where the benefits of modular construction can be realised. It is estimated that approximately 50% of all building in the residential sector is for buildings of more than 3 storeys and therefore a 10% market share would correspond to a 5% overall market. The current EU housing market is close to 1 million houses per year, but it is estimated that the underlying demand for housing is close to 20 million because of an ageing population, more single people, and poor quality housing in many regions.
Since the start of the MODCONS project, the housing sector has started to expand following the recession. Therefore, the potential market for the developed modular systems in during the MODCONS project is expected to grow. Importantly there are opportunities to expand the use of modular construction in countries participating in MODCONS but also other EU countries such as Italy, Poland and France, and to license the technology in the Far East and India.
The as-built cost of a module is around ~1,000 Euros per m2 floor area and so a 25 m2 module has a delivered cost of around 25,000 Euros, when installed, serviced and clad the completed cost of the building is about 15,000 Euros/m2. The potential new markets for modular construction arising from this research could be up to 30 million Euros per year for the SME partners. The route to market is based on a greater realisation of clients of the benefits of modular construction and the ability of the modular industry to deliver a range of solutions using standardised components.
The project was divided into seven work packages each with their own individual objects which when combined with each other enable the overall project objectives to be achieved.
Work Package 1: Design and Physical Tests on Modular Systems for High-Rise Buildings in Accordance with EN 1993.
The main objective of WP1 was to concentrate on the preparation of application rules for design in modular construction using steel technologies, which takes account of the nature and practicality of the construction system. The design guidance is based on the principles of Eurocode 3 for steel structures, Eurocode 1 for loading (actions) and EN1090-2: Execution of steel structures. The output guidance is based on physical tests and with supporting finite element analyses (FEA) of the tested systems.
Work Package 2: Emerging Themes and Building Typologies for Multi-storey Modular Buildings.
The objective of WP2 was to develop a diverse range of innovative typologies for modular residential buildings. An important task was to understand future demands and therefore to create building typologies that respond to these needs. The building typologies also take into account of the structural characteristics investigated in WP1. This Work Package has involved close participation of architectural practices experienced in modular construction.
The scope of work will develop residential building typologies using modular construction, which takes account of the construction system, spatial requirements, Regulations and planning standards in various countries, such as fire safety, circulation space and disabled access.
Work Package 3: Seismic Design of Modular Buildings.
The objective of WP3 was to consider various scenarios and intensities of seismic events which have been modelled statically by progressive ‘failure’ of the connections between the modules. Dynamic models will be performed to establish the natural frequency of the assembly of modules taking account of the ‘spring’ connections. The compatibility of equivalent static and dynamic models was investigated in order to develop design rules for the stability of modular buildings in seismic action.
Strategies to prevent collapse of modular buildings in severe seismic events were evaluated, such as by enhancing the resistance of the connections or by connecting the modules to intermediate ‘strong’ points via a separate structural frame. In high–rise buildings, it is sometimes necessary to introduce stiff braced floors, so that progressive failure of a large number of modules is prevented. This strategy is dependent on the precise building form.
Work Package 4: Sustainable Design of Modular Buildings.
The objectives of WP4 were divided into four parts:
• Quantification of the sustainability benefits of the construction process, based on measures such as; site impacts and disruption to the neighbourhood, safety, transport, waste reduction and recycling, use of recycled materials etc.
• Quantification of the operational energy benefits of modular construction and particularly comparison of design versus as–built operational energy use and other performance measures, such as over-heating and effective ventilation.
• Effective integration of renewable energy technologies in modular construction, which may be part of the module or attached to the modules.
• Environmentally conscious design solutions for modular buildings in terms of architecture.
Work Package 5: Acoustic Design of Modular Buildings.
The objective was to improve the acoustic characteristics of the modular systems in compliance with basic regulatory requirements, and then to achieve 3 and 5 dB improvements in acoustic insulation based on the double layer nature of modular systems, as follows;
• Examine the details of the modular systems in terms of control of airborne and impact sound transfer, taking into account the module to module connections
• Develop an adapted prediction method for the acoustic design of modular buildings
• Carry out laboratory measurements of the acoustic performance of modules relative to adjacent modules
• Evaluate the field performances of modular buildings in relation to laboratory measurements, and investigate any significant differences
Work Package 6: Dissemination and Exploitation Tasks.
The objective of WP6 is the dissemination task and is to publicise the information obtained from the project in terms of:
• Architectural information describing the building typologies and details for high-rise and mixed use buildings
• Structural design guidance on high-rise and mixed use buildings to Eurocode 3
• Seminars to present the results of the project
• Case studies on buildings using the developed technologies
• Sustainability guidance on modular construction
It was also necessary to manage the exploitation of the results of the project through a specific task, and to publicise the work at appropriate stages of the project and on completion.
Work Package 7: Management Tasks
The objective of WP7 is to enable the project to achieve the overall project objectives (development of new and innovative products to enter the market in a short to medium term) with regard to cost, quality and time, the management tasks required:
• Organizing the activities of the project partners and solving potential conflicts to carry out the project activities in due time according to the project programme.
• Acting as the interface between the project participants and the European Commission.
• Performing the coordination and organization of the intellectual property of the results.
• Coordinating and contributing to the technological transfer of the results.
The results of the project show that there is considerable scope for increased use of modular construction in high-rise buildings. Modular systems can be designed to satisfy all the required Regulatory requirements and have significant sustainability advantages.
Project Results:
The final results of the project will enable the companies involved to develop their products and produce innovative solutions within the modular construction sector. All work packages have resulted in improved design methods or levels of information that can be used by SMEs on future construction projects. The solutions adopted for each construction project is selected on an individual basis and tailored to suit the specific needs of the client and location. The work undertaken during MODCONS will enable solutions for future projects to be more accurately designed in terms of their structural resistance, seismic design, acoustic insulation, sustainability benefits and architectural form.
Work Package 1
The scope of work in WP1 was divided into the following tasks: Finite element analyses of modules under various actions and support conditions. Tests on light steel walls in modular construction in compression and shear. Module connection tests. Full-scale module tests and analysis. Structural guidance for modular systems.
Some of the main results and conclusions from WP1 are: The loss of a corner support is the critical case, especially where there are significant openings in the side walls. Modules can redistribute actions and remain stable (with significant distortion) when the corner support is removed. Lining materials (boards) provide a significant enhancement (20% to 40%) to the module stiffness. Plasterboard attached to light steel sections can improve compression resistance by up to a factor of two. With appropriate horizontal bracing, significant tie forces can be transferred by connection details (i.e. at the module corners). Eurocode 3 with supporting test data (which is system specific) can be used for the structural design of modular systems and buildings.
The final deliverable of WP1 is D1.6 which presents structural design guidance for modular buildings. The guidance is based on the findings and conclusions from the preceding activities of Work Package 1 of the MODCONS project in addition to generic design guidance from the Eurocodes. The guidance is presented so that it is directly applicable to high to medium rise modular buildings.
The design guidance addresses the key structural considerations required for a modular building including; loading, structural robustness, connection design, member design, resistance to uplift and lateral stability.
The structural design of the light steel modules is carried out by the modular manufacturers or their consulting engineers. They have the experience of their own particular systems and have developed many local details, including connections between the modules, connections to foundations, and local strengthening at lifting points. Thus, the role of the client's consulting engineer will often be confined only to site-specific items such as foundations and the co-ordination of the complete structural package.
The arrangement of the modules in plan and elevation also influences the load paths and many alternative configurations are possible without compromising structural efficiency.
The following types of modules may be used in the design of buildings using either fully modular construction or mixed forms of steel construction:
• 4-sided modules – designed to transfer loads continuously through their longitudinal walls, usually with closely spaced wall studs.
• Partially open-sided modules – 4-sided modules designed with partially open sides by introduction of corner and intermediate posts.
• Open-sided (corner supported) modules – designed to provide fully open sides by transfer of loads to the corner posts.
• Non-load bearing modules – similar form to fully modular units, but not designed to resist external loads, other than their own weight and the forces exerted during lifting (e.g. bathroom pod).
• Mixed modules and planar floor cassettes – floor cassettes span between load-bearing modules.
The modular systems studied during the MODCONS project are 4-sided modules with load bearing longitudinal walls, with closely spaced wall studs. Therefore, the guidance in D1.6 is primarily aimed at this type of construction.
From a series of tests carried out during MODCONS to determine the shear parameters for the FutureForm modules, the characteristic shear resistance of a bare steel panel and characteristic shear resistance of a plaster-boarded panel have been determined. The resistance values are not provided here as they are confidential. A partial factor of 1.25 should be used to obtain the design resistances of these panels. In order to allow for long terms effects, it is also recommended that the contribution of the plasterboard to the design resistance does not exceed 50% of that of the bare steel panel, so that the bare steel panel can resist serviceability loads if the plasterboard is damaged or removed for some reason during the life of the building.
The values determined are for panels without openings. The shear resistance and shear stiffness values for panels with openings will be significantly lower than those for solid panels. In all cases where plasterboard is used to provide restraint, stability, strength or stiffness to a light steel structure an accidental limit state check should be carried out on the basis that the plasterboard is not able to provide any enhancement to the light steel frame. This will ensure that in a situation where plasterboard is damaged or removed then the light steel structure will still be able to resist the loads from an the accidental limit state condition.
Similar calculations have been carried out to determine resistances for Cool Haven wall panels. However, in the Cool Haven system, OSB sheathing board is utilised. Tests were carried out during MODCONS to determine the shear strength of the connection between the steel profiles and the OSB by self-drilling screws. A numerical model was produced, which was calibrated against the experimental results. The numerical model was in close agreement with the test data and can be used to determine the performance of steel to OSB board screwed connection.
Light steel wall studs are used in conjunction with plasterboard, and often sheathing boards, to form a load-bearing wall panel. The presence of the boards provides a degree of lateral restraint to the studs, which may be utilized when calculating their buckling resistance. However, the level of restraint must be verified by testing, as was carried out during the MODCONS project. Testing of the FutureForm system has shown that a reduced buckling length may be used for boarded walls due to the presence of the boards and the fixity from wall stud connections to the floor joists.
Light steel sections are susceptible to torsional-flexural buckling, in addition to pure flexural buckling. If torsional-flexural buckling occurs at a lower magnitude of load than flexural buckling, this mode of failure will govern the resistance of the member. This is reflected in the design rules, in which the elastic critical buckling load used for design is taken to be the smallest of the elastic critical buckling loads for flexural buckling, torsional buckling and torsional-flexural buckling.
It has been shown by testing that the design procedure of EN 1993-1-3 by be used with the following modifications for the FutureForm system. Effective length factors may be applied to minor axis buckling of the C sections in the wall frames. The effective length factors derived for the system in MODCONS are confidential and therefore they are not published here. There are values for a bare steel frame and another factor for frames with plasterboard fixed internally.
The effective length factors are applicable for wall stud size of 70 x 1.2 mm thick. The design method may be used for other design cases, provided that the stiffness of the floor joists is increased in proportion to that of the C sections in the walls. The fixity of wall elements to floor and ceiling elements also enable the wall deflections to consider a reduction over the theoretical method for a nominally pin ended element.
The tests on the NEAPO system looked at the use of an innovative all-metal sandwich panel. The panels are used to fabricate modules for residential and other types of buildings. The modules are fully equipped with all their finishes and with mechanical systems (HVAC) needed in the building. The modules were fabricated by Neapo Oy.
The main goal was to search the design rules for these kinds of new panels mainly for European markets. In this study the design rules for heavily compressed and lightly loaded with bending moment (wall panels) was one main topic. Another scope was to define the design values for typical panels in shear loading used for stabilising buildings as diagraphs against lateral loads originating from imperfections, wind and seismic actions. The goal was to define the stiffening effects of boards (gypsum and OSB) screwed on the surfaces of the panels. The stiffening effects deal with the increase of the resistance and stiffness of the panels against axial and shear loads. The goal with stiffening is to enlarge the usability of the panels for higher buildings than today.
The rules in present standards do not cover the structural design of the panels. Tests were planned to validate the developed design rules. Tests were performed and the design rules were developed for practicing engineers to be used in building projects. One main principle in this study was, that the existing European standards, Eurocodes, are the reference standards and the new design rules should be in accordance with those standards. This strategy enables the further development of Eurocodes for these structures, and designers understand the design philosophy, enabling rapid implementation in practice.
The new design method for the interaction of high axial compressive force and small bending moments was developed. The safety level was shown to be as required in Eurocodes using the material safety factor for yielding and for flexural buckling of 1.0 as is recommended in Eurocodes and used in most countries in Europe. The loading case is typical for wall panels. The design method includes the resistances of bare all-metal sandwich panels, and panels stiffened with boards on compressed side or on both sides. The safety factor was shown to be smaller than 0.95 in all cases. The tests and the validations were done for extremely thin-walled wall panels (nominal thickness 0.7 mm), and for medium thin-walled panels (1.0 mm).
The same panels were tested for shear loads in the specific test frame made for these tests. The goal was to define the characteristic shear loads for the panels to be used in stabilising the buildings against lateral loads. The safety level was adjusted applying the standard EN 1993-1-3, Annex A, for the use in European markets. The design values are presented for two types of panels (nominal thickness 0.7 and 1.0 mm) without stiffening boards, including stiffening boards on one side and stiffening boards on both sides of the panel.
The tests showed high potential of the panels to resist axial and shear loads. Also the ductility of the panels in these loading cases was high. It is a desire of the authors that the results mean better competition ability of modular buildings made of these panels in the building sector.
Work Package 2
The scope of work in WP2 was divided into the following tasks: Modular system for European residential market. Building typologies and apartment arrangements using modular construction. Building typologies for high-rise buildings. Building typologies for mixed-use buildings, and finally; Architectural guidance on the developed systems.
Some of the main results and conclusions from WP2 are: Modules must be of an appropriate size for transportation, and a practical limit is 4.3m wide. Modules can be used effectively for modification of existing buildings e.g. roof top extensions. Modular systems can be used for all types of residential building, and 75% of all buildings in Europe are used for domestic purposes. With inventive architectural design, modular construction is extremely versatile and satisfies all the requirements of modern buildings.
Functional considerations have strong influence on the architectural design of modular buildings and especially residential and mixed use buildings. Functional requirements may be separated into those influenced by:
• Regulatory requirements for loading, thermal and acoustic insulation and fire safety.
• Performance and spatial requirements of the client, based on the use of the buildings, and influenced by mixed uses of the space.
• Site related constraints that influence the building layout, access, means of escape, as well as the means of construction.
The assembly of modules into complete buildings brings with it issues of stability, robustness, services distribution, attachment of cladding, access and circulation space, means of escape etc., which are the responsibility of the client’s architect.
The architecture of the building is directly related to the repetitive use of essentially similar 3-D components. Therefore, the following architectural aspects should be addressed in the concept stage of design and in planning, and require dialogue with the chosen modular supplier. These aspects should follow through into Regulation approvals and requirements for structural design and servicing distribution.
The following sections describe the Regulatory requirements and other issues that influence the design of buildings using modular construction, and cover:
• Energy efficiency.
• Acoustic insulation.
• Fire safety.
• Services distribution.
• Transportation.
The servicing strategy is also linked to the choice of the plan form, as although the modules are fully serviced in manufacture, the horizontal and vertical routing of services has to be considered carefully. In this respect, corridors provide zones for horizontal service distribution and access for maintenance.
In D2.2 detailed information is provided relating the regulatory requirements in different countries across Europe. Requirements considered include: energy efficiency, air-tightness, fire safety, means of escape, transportation limits.
Countries included are: UK, Finland, Sweden, France, Germany, Spain, Belgium, Italy Netherlands, Denmark and Portugal.
The report D2.4 presents an investigation into the architectural use of modules for mixed use residential and commercial buildings. Architect HTA Design has designed typical modules for various apartment types and sizes that have been used within the dimensional requirements of mixed use buildings. A number of standardised types that are chosen to meet many spatial and regulatory standards in the EU. Typical dimensions are shown based on a 300 mm grid.
Some of the general design requirements are:
• Modules are generally 3.6 m wide internally (and nominally on a 3.9 m grid, allowing for the wall dimensions and gaps between the modules). In practice, the FutureForm module are 3.85m wide when allowing for gaps. Module sizes are suitable for transportation without additional escort.
• Module lengths are variable, and range from 6 to 16 m, dependent mainly on transportation (and particularly turning into local roads). Modules may be manufactured with a central corridor.
• Load bearing side walls of modules align vertically and modules are supported by beams at the podium level.
• Internal wall heights are taken as 2.4 m, but can be varied. Externally, the module height is taken as 0.45 m plus the internal height, i.e. 2.85 m, allowing for the combined floor and ceiling depth.
• Open ends to the modules can be created by inclusion of a rigid steel ‘picture frame’ using Rectangular Hollow Sections. A nominal 100 mm ‘return’ is allowed on the end walls at doors and window openings. Large widows may be created depending on the stability strategy for the modules.
• Service connections are made generally at the corners of the modules and may be accessed from the corridors or other suitable spaces for maintenance. The vertical service routes are made through the module floor and ceiling at these locations.
• Any form of roof may be used, which may be supported either by the load bearing side walls or by the façade walls.
• The self-weight of a fitted out module is typically 8 to 10 tonnes, which is suitable for lifting by a 200 Tonne crane with a long boom for high rise buildings.
For the mixed use buildings with car parking at basement level, the columns are located on a grid, which is suitable for three car parking spaces between the columns. The building width is suitable for modules located either side of a corridor and also for car parking with a central aisle.
Intermediate levels may be used for office or retail space with columns at 5 m, 7 m and 5 m spacing across the building, or alternatively, the construction of a 17 m clear span leads to maximum efficient use of the space below. However, the column-free podium structure is more expensive than the structure with internal columns and would only be considered for high-value projects.
The commercial level is accessed from ground level and so does not require a lift. If additional floors of office space are required, then an additional independent access to the residential levels should be included, which may require a separate core. This type of solution is practical for buildings with 4 to 8 levels of residential space above 2 to 3 levels of commercial space. The optimum is likely to be 4 to 6 levels of residential space above to avoid excessive loads on the podium structure.
The following estimated member sizes may be used as guidance for the supporting steel podium structure:
• For a 6.5 m internal beam span at the podium level, an IPE 450 beam or 457 x 191 x 98 kg/m UB in S355 steel may be used to resist the applied moment from 6 floors of modules above when acting compositely with the floor slab. For a 5 m span, a lighter beam of the same depth may be used.
• For the 7.8 m span primary beams that are parallel to the façade and support adjacent 5 m and 6.5 m beam spans, an IPE 600 beam or 610 x 229 x 140 kg/m UB in S355 steel may be used when acting compositely with the floor slab.
• For the long span solution, with the car parking below, the spans may be reduced to about 12 m next to the braced core and could therefore be lighter.
• For a 16.5 m beam span, a 914 x 305 x 258 kg/m UB or an IPE 800 beam fabricated into a 1000 mm deep cellular beam with regular 450 mm deep openings may be used when acting compositely with the floor slab.
• For the long span solution, a 7.8 m span primary beam along the perimeter of the building supporting the 16 m span beam an IPE 800 or 762 x 267 x 173 kg/m UB beam may be used at the perimeter of the building when acting compositely with the floor slab.
Deliverable D2.5 is the dissemination of architectural guidance. This was the preparation of typical architectural arrangements of modules in various medium- and high-rise building forms, and their associated design details. This information will be used to support the practical use of the developed modular systems in new residential markets. In addition, D2.5 is the output which focuses on presenting guidance for architects on the building typologies obtained from the earlier tasks in WP2 that can be used in the planning of modular buildings.
The results include:
• Preparation of illustrations of the optimised design of apartments based on standard module sizes, and adaptation of these layouts for various building shapes.
• Preparation of illustrations of arrangements of modules in high-rise buildings, taking account of the circulation space in and around the building core.
• Preparation of illustrations of modular residential buildings over commercial space and car parks taking account of the access to the residential levels, car parking, means of escape in fire etc.
The architectural guidance document will be printed and disseminated to architectural practices and other groups who may consider the use of modular systems for building solutions.
Work Package 3
The scope of work in WP3 was divided into the following tasks: Finite element analyses (FEA) to Eurocode 8 and dynamic modelling of modular buildings. Finite element modelling of mixed use buildings. Strategies for seismic design of modular buildings.
Some of the main results and conclusions from WP3 are: Structures with modules supported on a podium structure perform well in seismic events, even if one column of the podium is assumed to be ineffective. High rise buildings generally require a separate bracing system or concrete core, which changes the load transfer between the modules. Pre-stressed bolted connections between modules can be twice as effective for energy absorption during seismic loading. Modules with structural hollow section rigid frames perform well in seismic events.
Report D3.1 of MODCONS addresses the behaviour of the FutureForm modular system under lateral loading and seismic actions. The analysis is based on a finite element model using the program, ANSYS, in which 4 and 8 storey building using 3 dimensional modules were analysed under various loading scenarios. The 3D modelling of a single module is presented in WP1.1 and the same model was used to analyse medium-rise modular buildings consisting of:
• A horizontal group of 4 modules of 3.6 m width x 7.6 m length.
• 4 and 8 storey buildings using the same group of 4 modules on plan.
• Bare steel and boarded modules using bracings to represent the stiffening effect of the boards.
• Loss of support to one corner of the 4 storey group of modules to represent damage after a seismic event.
No central corridor was included in these analyses as a single block of modules represents the worst case of design in which the modules are accessed by an external walkway. The cases analysed were for performed both for bare steel modules using 1.2 mm thick C sections for the vertical load-bearing elements, and modules with bracing representing the stiffening effect of the internal boards. It was found that the lateral deflection of the boarded modules was reduced by 30 to 50% relative to the bare steel modules.
A response spectrum analysis of the seismic forces was carried out to Eurocode 8 in order to determine the horizontal forces for the case of 20% ground acceleration. These seismic forces are compared to the case of wind loading in order to determine the effect of seismic design on the forces in the connections between the modules. It was found that the horizontal and vertical ties forces may be taken as not less than 25% of the factored vertical loading applied to one module.
Based on the results of the finite element analyses of the FutureForm modular system subject to lateral loading and seismic actions, the following conclusions are made:
• The boarded modules are about 30% stiffer than bare steel modules in terms of horizontal actions.
• A group of 4 modules is sufficiently stable for a 4 storey building, but it is recommended that the group of modules is increased to a minimum of 6 for an 8 storey building. No corridor is required for buildings up to 8 storeys high and subject to wind loading up to 1 kN/m2, as the single modules are stable in their long sides.
• The natural frequency of a 4 storey building was 2.2 Hz for boarded modules and this reduced to 1 Hz for an 8 storey building. From the response spectrum method, the base shear for the 4 storey building was 325 kN and 402 kN for the 8 storey building. The difference was relatively small because the stiffer 4 storey building attracted higher seismic forces.
• Connection forces in the ties between the modules were simulated by considering loss of a support after a seismic event. It was shown that the tying forces may be taken as not less than 25% of the factored vertical load acting on a module with a minimum value of 25 kN.
In many parts of Europe, it is required to design buildings for resistance to seismic actions, as presented in EN 1998-1-1: Eurocode 8, according to two methods:
• Response factor method based on the natural frequency of the structure as influenced by the ground conditions.
• Time history method based on an actual seismic event.
The response factor method results in equivalent horizontal forces which can be expressed as a proportion of self-weight of the building. Generally 5% equivalent horizontal load represents a modest seismic event and 10 to 20% equivalent horizontal load represents a more severe event. The first part of WP3 defines the magnitude of these forces for design to EC8 and seismic codes worldwide. Modular structures are stiff but their connections are relatively weak. Therefore, the forces attracted to the connections are crucially important to the stability of modular buildings.
Based on the results of finite element analyses of the FutureForm modular system, constructed from a ground floor podium structure, the following conclusions are made:
• Four or six storeys of modules can be supported on a steel framed podium structure arranged on a column grid of 8.8 m / 7.6 m x 7.2 m in which the side walls of the modules are supported by secondary beams. It is shown that the deflections of the frame are about 30 % lower than the theoretical deflections due to the line loads applied to the beams. This is because of the in-plane stiffness of the walls of the modules.
• This podium structure is stable even after loss of one column due to damage in a seismic event.
• The shorter secondary beams may be replaced by 16.4 m span cellular beams, but in this case, loss of a column leads to much higher displacements.
• The 6 storey podium structure may be stiffened by attaching the corridor between the modules to a concrete core, and it was found that the maximum tie force at this connection was 55 kN, when the modules are subject to seismic actions.
• Modules with rigid end frames using Structural Hollow Sections can be designed up to 8-storeys high, and it was found that the horizontal deflections due to seismic actions are not excessive provided the number of modules in a horizontal group is not less than the number of storeys.
• Mixed modular and steel framed systems were found to be efficient structurally and can be used to create more usable space.
Part of WP3 was to describe the modal spectrum analysis performed on an assembly of 12x4 single line of modules, representing a high-rise modular building, in order to validate the design of the proposed system in accordance with appropriate structural design codes (Eurocode 8).
The results indicate that the following conclusions can be made:
• The steel structure performs properly under the tested range of load conditions. The allowable design limits are not exceeded.
• The results given in the analysis of the influence of the stiffness of the joints show that the variation of the spring constant values does not affect the results of Von Mises stress nor the displacements. This proves that the stability of the modular structure will not be affected when the seismic loads are applied. Therefore the torsional stiffness is not considered a critical factor.
• The results of the buckling analysis of the module show that the loads leading to collapse are very high. Therefore it can be considered that the boards included in the interior and exterior walls as well as floor and ceiling significantly contribute to the bracing of the module.
• The results obtained including the concrete core (see section 5.5.4: “Modular assembly attached to a concrete core”) show improvements with respect to the models analysed without the core. Although the maximum displacement seems to be greater in this case (with the concrete core), it only occurs in specific areas. The total displacements registered on the assembly (that includes the effect of concrete core in the model) are lower in general than those obtained previously. Also, the steel structure performs properly under the indicated load conditions.
• The results obtained in the present analysis allow ensuring the suitable behaviour of the studied structures, according to Eurocode 8 requirements.
A podium structure is often used to support 4 to 8 storeys of modules above. The podium may be designed in steel or concrete. In a steel framed scheme, the beams are placed so that they align with the walls of the modules. In a concrete scheme using a deep flat slab, the modules may be placed in a random pattern on the slab. The relative economy of the two possible schemes was assessed. The economic comparison of the design of the podium structure was based on the following data:
• Columns placed on a 7.5 m square grid below the podium.
• 6 storeys of light steel modules placed on the podium.
The results of this cost comparison study showed that the weight if the steel solution was significantly lighter per floor area at 345 kg/m2 compared to 1335 kg/m2 for the concrete scheme. The steel scheme was also significantly less costly at € 188 /m2 compared to € 240 /m2 for the concrete scheme.
D3.3 extends the principles of seismic design to high-rise modular buildings using a concrete or braced steel core in which the dynamic response is dependent on both the modular and core parts of the building. This is important when considering the ability of the separate stabilising structure to transfer forces in seismic conditions and potentially to relieve the modular components of the high seismic actions. The characterization of connections in terms of energy absorption during a seismic event were defined. A seismic analysis was carried out and a modified pushover analysis repeated the same initial seismic analysis by progressively removing the most stressed connections to the stiffening core until failure.
After reviewing the results, the following conclusions can be made:
• The prestressed connections are more dissipative in terms of energy absorption, doubling the absorption when compared to same connections with non-prestressed bolts.
• Channels are far more dissipative than double angles.
• The steel structure performs properly under the load conditions for the seismic event that was selected for study.
• The results given in D3.3 show that the structure will not collapse until step 13, where 12 supports or connections between the modules have failed.
• Again, the results obtained in the analysis ensure the suitable behaviour of the studied structures, according to Eurocode 8 requirements.
Work Package 4
The scope of work in WP4 was divided into the following tasks: Sustainability benefits of modular construction. Energy performance of modular buildings. LCA embodied carbon and use of renewable energy technologies.
Some of the main results and conclusions from WP4 are: Modular construction is significantly different to traditional construction and therefore it is important that the main contractor on the project is experienced with modular construction. The sustainability benefits of modular construction are: Increased speed of construction (50% faster than concrete frame construction). Reduced site management cost. Improved safety (5 times safer than fully on-site construction). Reduced waste and landfill charges, and more opportunities for recycling. Higher productivity (fewer personnel on site). Reduced disruption to the locality by noise and traffic with fewer deliveries of materials. Renewable energy systems can be integrated into the modules during manufacture.
Report D4.1 presents on–site and factory data during manufacture, installation and construction of a modular residential building compared to site-intensive construction such as a concrete frame with blockwork infill walls. This data is determined for real modular projects and from existing studies. The broad conclusions on the sustainability and economic benefits of modular construction are:
• Cost - modular construction is most economic for larger projects when economy of scale in production and when the benefits of speed of construction are taken into account. For a residential building, financial savings can be 0.5% per month early completion, increasing to 1% for a time-dependent business like a hotel. This equates to a saving of 3 to 6% of the build cost for a 6 month reduction in construction period. The client’s design consultant costs are reduced by up to 2% of the total project cost as the detailed design is done by the modular supplier. Site repairs due to snagging are also reduced considerably. Hence, overall savings of 5 to 9% are possible in modular construction.
• Labour and productivity - the on -site labour in modular construction projects is reduced by up to 50% relative to site-intensive construction and the labour in a modular project is required for cladding and services and the non-modular parts of the building. Combined with the speed of construction, on-site productivity is increased by a factor of 3 to 4 in modular construction.
• Health & safety- safety data suggests that off-site manufacturing is 2 times safer than on -site construction per 100,000 hours. Taking into account the speed of manufacture, off-site manufacturing is therefore 3 to 4 times safer than on -site construction per unit area.
• Speed of construction - the reduction in construction period depends on the proportion of off-site manufacture in the project. For a fully modular building, the reduction in construction period can be 55 to 65% relative to site-intensive construction, such as concrete frame. For mixed construction, such as modules placed on a concrete podium, the reduction in construction period is 35 to 45%.
• Waste generation - various studies have shown that on site waste is reduced by 60 to 95% in modular construction relative to site-intensive construction, where 10 to 15% of materials are wasted by damage and over-ordering. Site waste is mainly due to the non-modular parts of the building, and so wastage rates of 1 to 4% may be taken as being typical in modular construction. The waste in manufacturing is small (1 to 2%) due to efficient ordering of materials, elimination of damage and better working conditions and all factory waste can be segregated and recycled.
• Environmental impacts -the environmental impact of the construction process is directly in proportion to the site activities and the traffic associated with it. Deliveries and personnel on site are reduced by 60% and these activities occur over a shorter construction period, so the overall site impact is reduced by a factor of 3 relative to fully on-site construction. The self-weight of modular construction is about one-third of that of concrete construction and the embodied carbon is 10 to 20% less. Modular buildings have better and more reliable thermal performance and lead to lower operational energy use. Furthermore, modular buildings are fully demountable and their asset value is retained if they are re-used.
• Social responsibility- modular manufacture gives more job security, better working conditions and training in parts of the country where employment is lower than in urban areas, where the modules are installed. This reduces pressure on the availability of local craft skills which is important particularly in London. Disturbance to the neighbourhood during construction is minimised and transport of modules to site can be timed in prior agreement with the police and neighbours.
The objective of WP4.2 of MODCONS was to evaluate the performance of a light steel modular housing scheme and to learn from the building construction and operation and from resident feedback, to inform future projects of a similar type and scale. The results and foreground are summaries below.
The Birchway Eco-Community scheme, which is in Hayes, Middlesex, UK comprises 24 apartments in five two storey blocks. The type of tenure is affordable rent. The buildings were designed achieve Code for Sustainable Homes Level 5, which was relatively advanced at that time.
The buildings were constructed to high thermal insulation and air-tightness standards. In addition, the scheme includes a wood-pellet fired, biomass boiler supplying all apartments on the development, photovoltaic (PV) panels on all five buildings and mechanical ventilation and heat recovery (MVHR) units in all apartments. The buildings have green (sedum) roofs and incorporate rainwater harvesting for flushing toilets.
The buildings were monitored over the winter to determine their total energy use. Meetings were held with the owner, Paradigm Housing Association, the architect, and FutureForm to understand how this project was designed and lessons to be learnt.
It was found that the total heating demand was 99 kWh/m2/year as an average across the 24 dwellings, although the variation was -90% to +90%, indicating that the user pattern has a major effect on the energy use. Of this, the space heating demand was on average 42 kWh/m2/year, which is only 11% higher than the design prediction in the SAP assessment. The energy generation from the photovoltaic panels was in-line with the design prediction and amounted to about 3500 kWh per year for each building, which greatly exceeded the energy required for communal lighting.
The measured air-tightness of all the buildings was 5.26 m3/m2/hr at 50 Pa pressure which is 15% better than the design requirement. The airborne sound reduction was on average 9 dB higher (better) than the Building Regulations Part E which is excellent. The impact sound transmission was on average 12 dB less (better) than the Building Regulations.
The percentage of hours over 27oC in the living room was only 3% and in the bedrooms was only 2%, which shows that over-heating was a low risk over the monitoring period.
Problems were experienced with the operation of the biomass boiler used for the communal heating, which was not part of the modular construction ‘package’ and with the perceived air quality due to the MVHR system that was specified. Overall the satisfaction of the residents with the buildings was good, particularly in relation to the living space of the modular system.
Lessons and recommendations relating to the design and construction based on the experience of this project include:
• Chose a contractor with appropriate experience of the modular construction system and the renewable energy and sustainable technologies to be employed.
• Avoid late design changes wherever possible; this is particularly true for offsite methods of construction, such as modular systems.
• Provide clear demarcation of responsibility between contractors and between parties within the design team particularly with respect to interfaces such as heating systems and air-tightness boundaries.
Assessment of the building fabric of the Birchway dwellings included:
• Air-tightness testing – undertaken for Part L compliance
• Thermal imaging survey
• Acoustic testing – undertaken for Part E compliance.
The target air tightness for the dwellings in this development was an air leakage index (ALI) of 6 m3h 1m 2 at 50 Pa The average air-tightness achieved for the 10 (of 24) dwellings tested was 5.26 m3h-1m-2; ranging from 2.75 m3h-1m-2 to 6.88 m3h-1m-2.
No obvious correlation between floor area and airtightness was observed although the performance of flats in the (larger) Type A buildings appears to be better than those in the Type B buildings. The measured air-tightness results were slightly higher than similar modular projects probably due to poor onsite on-site realignment of some windows by the main contractor.
The thermal imaging survey was undertaken in the winter. This survey showed the good thermal performance of the modules with no serious thermal bridging but identified areas of possible thermal bridging in the non-modular areas, notably at the eaves. Heat lost from the loft areas, which house the hot water storage tanks, was clearly identified.
The results of the airborne sound insulation tests of the walls meet the requirements of Approved Document E and the Code requirements to achieve the maximum four credits under the sound insulation criteria (Hea 2). The test results for the floors also met the requirements of Approved Document E and, with the exception of the floors between two flats, the Code requirements to achieve the maximum additional four credits.
The results of the impact sound insulation tests of the floors meet the requirements of Approved Document E and the Code requirements to achieve the maximum four credits.
Results and conclusions relating to the renewable energy and sustainable technologies are:
• The biomass boiler was a key component of the strategy to achieve CSH Level 5 on this development. Since handover, there have been problems with the biomass boiler and the communal heating system. Water ingress to the pellet store caused problems with the feed and combustion of the pellets.
• The PV systems installed appear to performing relatively well, i.e. in line with the design predictions. Nevertheless, problems have been identified in particular with the inverters.
• The MVHR system installed in the dwellings was a whole house central mechanical supply and extract unit with heat exchanger. It is clear from the residents’ feedback that the ventilation solution was not working as well as might be hoped.
In D4.3 a comparison of the embodied carbon in the building fabric was made between a typical modular residential building using a light steel framework and an equivalent reinforced concrete frame with blockwork infill walls. The study was made for a notional 6 storey building of 13.5 m depth and with a 1.5 m wide central corridor in which the modules were 3.5 m wide. The same grid was considered for a concrete structure of 7.0 m x 7.5 m / 6.0 m grid.
The embodied carbon comparison includes the main components of the building fabric, which are the primary structure in steel or concrete, the walls, plasterboards and other boards, insulation, etc. but does not include windows, services and finishes. The same external cladding was assumed on both buildings, i.e. brickwork for the first four storeys and insulated render above. The impact of the foundations was also assessed.
The results showed that the embodied carbon content of the modular structure is 182 kg CO2e per m2 floor area, and that of the concrete structure with blockwork infill walls is 229 kg CO2e per . This shows that the light steel modular system has a 20% lower embodied carbon and also is only 30% of the total weight of the structure of the concrete frame.
Also included was an investigation into the use of renewable energy technologies attached to or built into the modules in a typical residential building. The technologies investigated are Photovoltaic panels connected to the modules and the use of in-built ducts with embedded Phase Change Materials to reduce over-heating and hence demand for cooling. This application is best suited to modular roofing systems.
Work Package 5
The scope of work in WP5 was divided into the following tasks: Defining the requirements for acoustic design of a modular building. Laboratory measurements of acoustic performances of lightweight elements. Acoustic design of junctions between elements by tests on module junctions. Field tests on real buildings for acoustic performance of modular buildings.
Some of the main results and conclusions from WP5 are: Different parts of Europe demand different levels of sound insulation between rooms. Modular construction systems provide the required level of acoustic performance by at least 5dB. Flanking sound at junctions is reduced by the discontinuous nature of the connections in modular construction. The number, type and thickness of boards used for wall and ceiling linings contribute significantly to the level of sound insulation achieved. The modular system studied achieved excellent acoustic performance in laboratory testing and demonstrated by field testing of completed buildings.
Acoustic regulatory requirements applicable in European countries are expressed in terms of acoustic descriptors considering in situ situations. This implies the need for a preliminary design to meet the acoustic performance of the building systems once implemented in the building. This is the reason why acoustic prediction models are required for the building design in relation to their acoustic performance. There is currently no approved prediction model, validated and included in international regulatory systems for the acoustic performance of lightweight constructions.
Sound insulation is potentially one of the weaknesses of lightweight building systems. It is therefore necessary to conduct a theoretical and experimental study of these systems through a series of constructive simulations, experimental measurements and later by laboratory and field tests. Report D5.1 summarizes the main acoustic requirements for the countries involved in the consortium of this project.
The acoustic insulation provided by a series of typical light steel floor constructions is presented in Table 3 of D5.1. A resilient layer beneath the floor finish reduces both airborne and impact sound transmission. Generally, mineral fibre of 70 to 100 kg/m3 density provides sufficient stiffness to prevent local deflections, but is soft enough to function as a vibration isolator. Mineral wool placed within the depth of the floor and ceiling helps to absorb sound in the cavity between the C sections. Thicker layers of fire resistant plasterboard have higher mass than ordinary plasterboard, thus reducing sound transmission.
Flanking transmissions can add 3 to 7 dB to the sound transfer measured in buildings in comparison to those tested acoustically in the laboratory. To reduce flanking transmission, it is important to prevent the floor boarding from touching the wall studs by including a resilient strip between the wall and floor boarding. Furthermore, in modular construction, the mineral wool insulation and sheathing boards help to reduce flanking transmission.
D 5.2 describes acoustic laboratory tests carried out on the FutureForm system (two walls and two floors), taking into account not only improving acoustic performances, but also optimizing width and costs of the system and preserving other characteristics: e.g. Fire protection, thermal performances, etc.
The alternatives in the floor design have focused on the improvement of impact sound insulation, which also leads to a better airborne sound insulation. It was agreed that the elastic effect of a rubber layer between modules would be tested as its elimination would involve reduction of costs.
It was also decided to test a typical double steel frame wall with two plasterboards on each side and the same with one plasterboard on each side.
The test results and foreground show, the effect of rubber layer does not improve acoustic insulation (airborne and impact) of combined ceiling and floor, as individual element.
By further consideration of the laboratory acoustic results, it can be concluded:
• The wall with 2 plasterboards on each side could be used in the UK, Spain, France and Finland in dwellings separations.
• The wall with 1 plasterboard on each side is considerably less insulating than the other one. This wall would not be enough in dwellings separations for UK and France. For Spanish requirements it is in the limit, it will depend on flanking transmissions. For Finland it would be enough.
• The floors are valid for Spain, UK and France in dwellings separations. Impact sound insulation results are on the limit for Finish requirements.
Results from WP5.3 lead to the following conclusions:
• When designing acoustically modular systems that constitute two enclosures, both the direct path and the flanking paths generated at the junctions have to be studied. The latest can reduce significantly the overall insulation between two rooms.
• In this phase of the project, the flanking transmissions that occur in the junctions of the modular mixed system has been analysed in detail in mock-ups made with 4 steel structure modules.
• From the measurement campaign it has been set that there is a sufficient attenuation in all the junctions analysed. The fact to have multilayer elements, gypsum boards finishes, and so on is positive to assure the discontinuity between modules.
The D5.4 results conclude that the airborne and impact sound insulation measurement results of a modular detached house in Madrid, are found suitable to fulfil noise requirements in Spain.
Standard procedures of new standard ISO 16283 parts 1 and 2 has been compared to low frequency procedure:
• From the airborne sound insulation test between two rooms vertically (one above the other), the low frequency method gives higher result in the spectra for low frequencies and the overall index turns out to be two more decibels for low frequency method.
• From the airborne sound insulation test between two rooms s horizontally (side by side), no difference between the two test methods were observed. This may be because the result has a higher insulation value, and the test method is not having influence in the result.
• From the impact noise insulation test in rooms oriented horizontally (side by side), higher values of impact noise level is obtained by the method of low frequency and the global impact insulation index for 50 Hz is also penalized with the low frequency method
• From the impact noise insulation test in rooms oriented vertically (one above the other), a higher level of impact noise is obtained by the method of low frequency; however, the overall index for both methods is not modified.
Alternative impact sound sources have also been studied in order to study the influence of characterization methods in the lower frequencies.
A series of on-site tests was performed for a modular residential project in west London using the same system as was tested in the laboratory in WP5.2. The results for the 10 floor-ceiling tests and the 10 separating wall tests between different rooms constructed from modules were analysed and the variation in the measured results was found to be small. The airborne sound reduction index Dntw was on average 63dB for floors and 59dB for walls, and in both cases, the low frequency correction factor, Ctr was -11dB. The impact sound transmission of the floors was 49dB. All of these results are significantly better than national regulations. Building design using lightweight modular construction solutions has been shown to comply with acoustic requirements.
Deliverables
A comprehensive set of deliverables have been produced which included detailed scientific and technical data relating the activities carried out and their results and foreground. The deliverables produced in the scientific and technical work packages are:
D1.1 - Report on finite element analyses of modules under various actions and support conditions.
D1.2 - Report on tests on light steel walls in modular construction.
D1.3 - Report on module connection tests.
D1.4 - Report on full-scale module tests for Module type 1.
D1.5 - Report on full-scale module tests for Module type 2.
D1.6 - Dissemination of structural guidance.
D2.1 - Report on modular systems for European residential market.
D2.2 - Report on building typologies and apartment arrangements using modular construction.
D2.3 - Report on building typologies for high-rise buildings.
D2.4 - Report on building typologies for mixed us e buildings.
D2.5 - Dissemination of architectural guidance.
D3.1 - Report on finite element analyses to Eurocode 8 and dynamic modelling.
D3.2 - Report on finite element modelling of mixed use buildings.
D3.3 - Report describing strategies for seismic de sign of modular buildings.
D4.1 - Report on sustainability benefits of modular construction.
D4.2 - Report on the energy performance of modular buildings.
D4.3 - Report on LCA and use of renewable energy technologies.
D5.1 - Definition of requirement s for acoustic design of a modular building.
D5.2 - Acoustic design of lightweight elements. Laboratory acoustic performances of elements.
D5.3 - Acoustic design of junctions between floor elements. Tests on modules and of junctions.
D5.4 - Acoustic performance of modular buildings. Field tests on real buildings.
Potential Impact:
The final results of the project will enable the companies involved to develop their products and produce innovative solutions within the modular construction sector. All work packages have resulted in improved design methods or levels of information that can be used by SMEs on future construction projects. The solutions adopted for each construction project is selected on an individual basis and tailored to suit the specific needs of the client and location. The work undertaken during MODCONS will enable solutions for future projects to be more accurately designed in terms of their structural resistance, seismic design, acoustic insulation, sustainability benefits and architectural form.
The impact of the tasks completed during the dissemination work package (WP6) are: 1) Publicising the information created during MODCONS. 2) Spreading knowledge about the advantages of modular construction e.g. sustainability benefits and architectural options. 3) Promoting the use and possibilities of high-rise modular construction. 4) Making information available on modular buildings through case studies and other information available from the MODCONS website (www.modconsresearch.eu). 5) Informing the construction industry about modular construction and the research that has taken place during MODCONS through speaking at industry events and seminars.
The use and dissemination of the foreground information produced during MODCONS has assisted in achieving the objectives of MODCONS by the promotion of modular systems and the product development of the specific systems researched. The project has produced a large amount of foreground information, which is being disseminated in a variety of methods (e.g. seminars, websites, articles, shows, technical papers, presentations etc.) and being used to the advantage of the project partners. These advantages of modular construction systems will spread to other parts of construction industry as the specialist consultancy knowledge obtained by the partners is used for new clients and customers.
The responses form the dissemination activities have been extremely positive and encouraging for the increased adoption of modular construction. Audiences have been enthusiastic and supportive of the information presented. At several of the events audiences have included representatives from clients and policy making authorities. There are good reasons for an optimistic view on increased use of modular systems to address construction needs in the future.
Since the start of the MODCONS project, the housing sector has started to expand following the recession. Therefore, the potential market for the developed modular systems in during the MODCONS project is expected to grow. Importantly there are opportunities to expand the use of modular construction in countries participating in MODCONS but also other EU countries such as Italy, Poland and France, and to license the technology in the Far East and India.
The potential new markets for modular construction arising from this research could be up to 30 million Euros per year for the SME partners. The route to market is based on a greater realisation of clients of the benefits of modular construction and the ability of the modular industry to deliver a range of solutions using standardised components.
The impact of the technical research work packages (RTD) of MODCONS is summarised below. All work packages have resulted in improved design methods or levels of information that can be used by SMEs on future construction projects. The solutions adopted for each construction project is selected on an individual basis and tailored to suit the specific needs of the client and location.
The work undertaken during MODCONS will enable solutions for future projects to be more accurately designed in terms of their structural resistance, seismic design, acoustic insulation, sustainability benefits and architectural form.
WP1 - Structural design developments for modular systems:
• Improved racking (shear) resistance for walls.
• Design resistances in accordance with Eurocodes.
• Improved compression resistance of wall panels.
• Improved understanding of structural behaviour of modules.
• Improved design solutions for structural robustness.
• Improved solution for distribution of connection forces.
• Design guidance for compliance with Eurocodes.
WP2 - Architectural design developments for modular systems:
• Architectural building typologies for medium-rise buildings.
• Architectural building typologies for high-rise buildings.
• Architectural building typologies for mixed-use buildings.
• Architectural guidance for modular solutions.
WP3 - Seismic design developments for modular systems:
• Guidance on seismic modelling of modular buildings.
• Performance of modular buildings on podium structures in seismic scenarios.
• Performance of modules with rigid steel end frames.
• Performance results of various modular buildings in seismic scenarios.
• Guidance on dissipative systems.
• Strategies for seismic design of modular buildings.
WP4 - Sustainability design developments for modular systems:
• Quantified sustainability benefits of modular construction.
• Case study data for sustainability of modular building projects.
• Sustainability messages for modular construction.
• Energy performance / usage monitoring data for modular building.
• Practical considerations for energy usage in modular buildings.
• Thermal performance data at junctions for modular systems.
• Air-tightness data for modular systems.
• Life Cycle Analysis (LCA) information for modular buildings.
• Embodied carbon comparison for modular and traditional construction.
• Options for incorporation of renewable energy technologies with modular construction.
WP5 - Acoustic design developments for modular systems:
• Acoustic requirements for modular buildings across Europe.
• Guidance on principles of acoustic insulation.
• Laboratory test data for walls and floors of modular systems.
• Improved acoustic design of junctions and interfaces.
• Site based acoustic test data for modular systems.
The dissemination activities that have taken place are reported in detail in the deliverables from Work Package 6. The most relevant deliverables are:
• D6.1 Exploitation management.
• D6.2 Elaboration of diffusion material.
• D6.3 Seminars to promote development of modular systems.
• D6.4 Case studies on modular construction.
• D6.5 Participation in sectorial fairs.
• D6.6 Website report.
• D6.7 Video clip report.
• D6.8 Report on Wikipedia page.
• D6.9 Report on conformity with Regulations.
A list of the dissemination activities and the areas they address is provided in Table 3.1 of Deliverable D7.2 “Final Plan For Dissemination and Use of the Foreground”.
The original dissemination plan included 3 seminars. However, instead of 3 standard seminars, it was considered to be more appropriate and more effective to present at a range of seminars or events with presentation material tailored to suit different types of audience. It was considered that this would be more appropriate for communicating the messages that were required about the development of modular construction systems.
In some cases, presentations were given at existing construction industry events rather than at new events specifically setup to disseminate the information from the MODCONS project. This decision was taken as it was believed that this would enable a larger audiences to be reached at more events in a more cost effective way.
The dissemination activities have been extensive and have included electronic dissemination (e.g. websites, emails and webinars), oral presentations (e.g. at conferences, workshops, exhibitions etc.) and printed dissemination (e.g. magazine articles, project brochures and guidance documents).
The research (RTD) performers of MODCONS; SCI, Tecnalia and Technical University of Tampere and Coimbra University, envisage long term partnership roles with modular system suppliers in the UK, Spain, Finland and Portugal respectively. The foreground research developed during MODCONS will be re-invested in the form of industry guidance, product development and system approvals. This is particularly relevant for aspects of robustness, seismic design and acoustic performance, which could lead to specialist consultancy for the RTD performers and SME consultancy partners.
Each of the technical work packages of MODCONS were aimed at investigating different aspects of the performance of the modular systems. The information gained through each of these work packages will enable the modular manufacturers to obtain more in depth knowledge about how their systems behave under different scenarios.
The module manufacturers will implement this information by making improvements to their systems and their design procedures. These improvements will either be aimed at superior performance or increased efficiency of design, manufacture and construction. Module manufacturers will disseminate these product developments through their own company literature and contractual discussions. The details of many of the findings of the project research are commercially sensitive, and therefore, public release of all the details is not possible. However, many public dissemination activities have taken place during the MODCONS project. The specialist consultancy companies involved in the MODCONS project will also benefit from the knowledge gain during MODCONS. Exploitation of results will enable consultants to assist other companies involved in the modular construction sector with their increased knowledge and experience which has been gained as a direct result of the project. These skills include: Computational modelling of structures, Acoustic performance analysis and prediction, Expertise on modular systems, Structural design and analysis skills, Finite element modelling and Sustainability performance guidance.
List of Websites:
MODCONS website is www.modcons-research.eu
SCI (Project coordinator) Tel: +44 1344636525
Other relevant contact details are provided on the website.
