By their nature, with many degrees of freedom and the possibility of sliding between blocks, multi-block structures have good seismic performance. However, the advent of large multi-block buildings means that particular care needs to be taken to increase their seismic stability properties. In this work, the shape of the blocks of multi-block structures is studied to improve the seismic stability of these structures. This study is carried out using the Level-Set Discrete Element Method (LS-DEM). A multi-block structure is modelled and submitted to various ground velocities representing seismic excitations. Different block shapes are studied and then improved with a simplified five-block structure to isolate the seismic stability properties of the different block shapes, both for sinusoidal ground motions and for real earthquakes.
On the one hand, blocks with different curvatures are studied and compared, for different friction coefficients. The increase in contact area combined with the ease of sliding showed a reduction in the maximum displacements and rotations for a slight curvature of the blocks. On the other hand, changes in the support condition are applied and show a clear improvement in the seismic stability of multi-block structures. The frequency of oscillation is increased, while the amplitude of displacements and rotations is reduced. This leads to major considerations in improving the stability of multi-block structures and, in particular, in those that are used for gravitational energy storage for instance as developed by the Energy Vault company. The design of block shapes is proving to be an effective and low-cost solution for increasing the seismic stability of multi-block structures.
In addition, a theoretical validation of the LS-DEM software developed by the COSYMO laboratory at Caltech is carried out for the first time in the context of multi-block towers, validating its relevance and the various results observed in this thesis.