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Network for supporting the development and application of performance based durability design and assessment of concrete structures

Objective



The present design approach with respect to durability of concrete structures is largely empirical. It is based on deemed-to-satisfy rules (for example minimum cover, maximum water/cement ratio) and the assumption that if these rules are met, the structure will achieve an acceptably long (but unspecified) life. Improved durability results in increased building costs, but current design methods do not permit to demonstrate that future maintenance and repair costs will reduce. The concrete industry is therefore unable to compete on the basis of durability. The Construction Products Directive and ENV 1991 'European Standard for the Basis of Design' state that works shall meet essential requirements for their economically reasonable 'working life'. This introduces a time dependent function into performance specifications which are usually based primarily on testing products 'ex works'. Current design codes do not include working or service life as a design parameter. Owners of concrete structures have required for many years that their structures should have a specified service life, for example the Storm Surge barriers in the Netherlands (200 year), the Great Belt Link in Denmark and the Oresund Link between Denmark and Sweden and the Metro in Copenhagen (100 year), the Eurotunnel (120 year) and the floating offshore structure Troll in Norway (60 year). Essential requirements such as the limit states to be considered and the reliability level have not, however, been specified. Service life requirements are also given in building codes. The Eurocodes have specified d reference period or service life of 50 years. The Dutch Building Decree specifies 15 years or 50 years, depending on the type of structure. BS 5400, Design of Bridges, specifies 120 years. The Swedish concrete code provides the option to design for 50 or for 100 years. But in no case is a method specified for proving these service life requirements. A performance based design and assessment provides the option of objective competition on the basis of durability. It uses realistic models capable of predicting the performance in relation to time. Modern structural codes, such as the Eurocodes, base the structural behaviour already on a performance concept. This offers the advantage of a seamless transition between structural design and durability design. A further advantage is that the methodology can in principle also be applied to other structural materials and even to non-structural building materials. Various initiatives have been taken successfully in Europe to establish a performance and reliability based design approach for concrete [7, 8, 9, 10, 11]. In 1995 the Brite/EuRam project (BE95/1347) 'DuraCrete' has been started to contribute to the development of the performance and reliability based service life design for concrete structures. The main product of this research - a design manual -will be available for the concrete industry. In 1997 CEB Comit‚ Euro-International du Beton) has published a bulletin [12] with the basic framework for service life design. CEB will support this approach and aims at a Model Code for Service Life Design. Looking at this list of initiatives it is clear that the development of the performance based service life design is coming to a stage where it can be used in practice. Given the many initiatives in Europe it is essential to involve more people from the European concrete industry as this will lead to a broader base of support for the approach and its application in practice and effective co-ordination of future efforts. The proposed network DuraNet is intended for supporting this development. Co-ordination, collaboration and consensus with respect to the new developments and applications are urgently needed to maintain this position. Since there are also other initiatives already underway in countries like Australia, North America (ACI and NIST) and Japan and work in ISO, it is imperative for the industry in the EU to keep ahead in the development of performance based durability design as a matter of economic priority. At the same time Europe should try to profit from the useful developments made in these non-European countries. Besides direct industrial interest there is also interest from sustainable building in extending the requirements for service lives. A building with a longer service life will reduce the demands on raw materials and energy. Moreover the public sector is forced to invest in more and larger infrastructures. An important part of the infrastructure will be built under the ground where maintenance and repair is often impossible or extremely expensive. The technical solution to this problem is to ensure a long service life with a high reliability.

Coordinator

NETHERLANDS ORGANISATION FOR APPLIED SCIENTIFIC RESEARCH - TNO
Address
5,Schoemakerstraat, 97
2600 AA Delft
Netherlands

Participants (18)

CHALMERS UNIVERSITY OF TECHNOLOGY
Sweden
Address
8,Sven Hultins Gata 8
412 96 Goeteborg
COWI consult, Consulting Engineers and Planners A/S
Denmark
Address
15,Parallelvej
2800 Lyngby
Centre Scientifique et Technique de la Construction
Belgium
Address
21-23,Rue De La Violette
1000 Bruxelles
Concrete Association of Finland
Finland
Address
Mikonkatu
00100 Helsinki
HYWEL DAVIES CONSULTANCY
United Kingdom
Address
The Furlong 2
MK41 8EE Bedford
Ingenieursbüro - Architekturbür Hergenröder Partnerschaft
Germany
Address
Rosenstrasse
91207 Lauf
Ingenieursbüro Schiessl Raupach Consulting Engineering
Germany
Address
Bergdriesch
52062 Aachen
Instituto Superior Técnico
Portugal
Address
Avenida Rovisco Pais
1096 Lisboa
Instituto Técnico de Materiales y Construcciones SA
Spain
Address
30,Monte Esquinza
28010 Madrid
Linuhönnun hf.
Iceland
Address
4A,sourlandsbraut
1108 Reykjavik
NORWEGIAN DEFENCE CONSTRUCTION SERVICE
Norway
Address
Akershusfestning Oslo Mil / Akershus 58
0015 Oslo
Norwegian Public Roads Administration
Norway
Address

0033 Oslo
Rigas Tehniska Universitate
Latvia
Address
Murjanu Street
10248 Riga
Rijkswaterstaat - Ministerie van Verkeer- en Waterstaat
Netherlands
Address
Herman Gorterhove
2700 AB Zoetermeer
SELMER SKANSKA AS
Norway
Address
25,Olavsgate 25
0166 Oslo
Taywood Engineering Ltd
United Kingdom
Address
Taywood House 345 Ruislip Road
UB1 2QX Southall
Technical University of Budapest
Hungary
Address
2,Bertalan L.u.
1521 Budapest
Verein Deutscher Zementwerke eV
Germany
Address
Tannenstraùe
40476 Düsseldorf