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Structurally informed Design of Masonry Assemblages Composed of Interlocking Blocks

Periodic Reporting for period 1 - SiDMACIB (Structurally informed Design of Masonry Assemblages Composed of Interlocking Blocks)

Reporting period: 2018-07-01 to 2020-06-30

SiDMACIB has developed a computer aided design (CAD) tool that analyses if an interlocking assemblage of blocks is structurally valid, and if not, it automatically adjusts the shape of interlocking joints to make the assemblage structurally sound. The project develops a new analytical method to assess the structural feasibility of the joints with non-isotropic sliding resistance. It formulates the structural behaviour of an assemblage as a function of the interlocking joint geometric parameters. SiDMACIB also develops a method to analyze if the designed interlocking shapes can let the blocks to be assembled/disassembled.

Finding the structurally optimal shape for interlocking joints is of a great interest to e.g. architects and civil, mechanical, and industrial engineers. Specifically, advanced digital tools may allow design and fabrication of complex models with the maximum structural and environmental performances. On the other hand, interlocking assemblages have significant contributions in the everyday life of society, and can be observed e.g. in the form of Lego bricks and the IKEA furniture. Their most important advantage is that they can easily be assembled and disassembled by the user. Following this concept, SiDMACIB open source plugin enables the users (who can be non-experts) to design and manufacture their desired interlocking assemblages.
Objectives, results and works performed

An interlocking block with corrugated faces, can be seen as a main body with some projections on its faces called locks. These blocks may slide with respect to each other in one direction, when the joint frictional resistance is not enough. Also, if the locks and the main body are rigid enough, the block can fail in another direction, when the locks lose their connection with the main body. I.e. the mechanical behaviour of an interlocking joint not only depends on the frictional properties of the contacts between two blocks, but also on the mechanical properties of the assumed cohesive contact between each lock and the main body.

- First, SiDMACIB studied these mechanical properties and recorded the ultimate torsion-shear resistances of the contact subjected to the tangential force with different eccentricities with respect to the contact centroid, using numerical, analytical and experimental approaches. The analytical approach is an extension to the concave, convex and corrected concave formulations. The numerical approach is based on the discrete element method using 3DEC. The experimental investigation is a novel physical test to study the torsion-shear behaviour of interlocking joints as an alternative to the European Standard test.

- Then, the static problem of limit analysis (one of the main classical methods to analyse masonry structures) was extended to the interlocking joints with orthotropic sliding behaviour and validated using discrete element method. In this approach, the assemblage stress state is abstracted to the internal forces at some contact points distributed on interlocking joints. Several point distributions were tested to find the most realistic option.

- Reformulating the static problem, a method was developed to measure the infeasibility of a model due to the sliding valid range violation (sliding infeasibility). The method identifies the internal forces within and outside the mechanical valid ranges and takes their value to measure the sliding infeasibility in a model.

- A shape optimization was developed that first measures the sliding infeasibility of an interlocking model, and then automatically changes the designated geometric parameters of interlocking joints to minimize the measured infeasibility and find the structurally valid assemblage.

- An assemblability method was developed to check if the designed interlocking blocks can be assembled on the other blocks in contact. Choosing the wrong shape for the interlocking joints can immobilize a block in all directions. Adopting the Non-Directional Blocking Graph (NDBG), a simplified geometric analysis was formulated to check if the designed joints are assemblable.

- An open source Rhino-Grasshopper plugin was developed to model interlocking single layer shells with arbitrary shapes, with stacked or running bond pattern and with the possibility of modelling openings inside the shell. The plugin checks structural validity of the model, measures its infeasibility, and finds the optimal joint shape minimizing the infeasibility.

Dissemination and exploitation

SiDMACIB has been disseminated by nine peer reviewed journal and conference papers in the field of Structural Engineering and Computational Design. It was also presented in eight international conferences and workshops, with access to the experts both from academia and industry. All the papers, posters, and presentations are available on the Zenodo repository.
The SiDMACIB open-source GH plugin is available on the GitHub and Zenodo repository.
Furthermore, SiDMACIB concepts were introduced to the non-expert audiences in several outreach events held in Naples, a Radio interview, SiDMACIB official webpage and a Facebook page. The related flyers, videos and posters are available on the Zenodo repository.
While the 20th century construction industry encouraged the use of strong materials, the evolution in architectural design and construction in the digital age facilitates the implementation of weaker materials including masonry with the strong complex shapes. This stimulates the sustainable design through the use of the local and/or environmentally/friendly materials. Following the same concept, SiDMACIB proposed a digital design method to model structurally optimal interlocking masonry assemblages.
This research falls into the joint treatment studies including finding the proper shape and material for the joints. The topic is highly interdisciplinary and of significant interest to, e.g. architects and industrial designers, as well as civil, mechanical and industrial engineers in micro and macro scales, both in academia and industry.
Numerous studies in materials and mechanical engineering applications focused on surface treatments, finding the composition of different materials constituting the joints.
DESIGNING the proper joint interlocking SHAPES, to enhance the mechanical properties, is rather a novel topic, and recently, several works have addressed its relation with different, yet limited, geometric parameters of the modular interlocking blocks. However, so far, very few works have been focused on DESIGNING the shape of each individual interlocking joint to maximize the load bearing capacity of an assemblage. SiDMACIB is one of the first efforts to design structurally sound interlocking blocks with finite shear and friction, which, however, remains limited to corrugated interlocking faces.
Joint shape optimization to minimize the sliding infeasibility
Torsion-shear resistances of the contact between the lock and the main body of interlocking blocks
Static problem extension to the corrugated joints and sliding infeasibility measurement