Investigation of the behavior of overburden reinforced concrete bridges under the relative motion of normal fault rupture

The construction of urban infrastructure structures such as bridges, tunnels, etc. located on the fault line is inevitable in many cases. Therefore, various solutions have been proposed to reduce the damage to national vital arteries. In this research, grid caisson foundations have been used for the bridge foundation system to reduce the destructive effects of fault propagation. First, the three-dimensional finite element numerical model was validated using experimental models. By comparing the deformation of the ground surface due to normal fault between the numerical and laboratory models, a maximum difference of 5% was observed, which had a good agreement. Then, a parametric study was performed to influence the parameters such as foundation thickness, foundation stiffness, relative position of the foundation relative to the fault outcrop, and the connection of the bridge slab deck on the overall performance of the bridge. The results of numerical studies showed that mat foundation cannot meet the overall stability of the bridge under normal fault. The grid caisson system had better performance. This system was able to withstand large tectonic deformations. Indeterminate of the structure has caused negative effects on the elements of the structure. While reducing the degrees of structural indetermination, it reduces the stress on the pier members and the deck of the bridge slab. The use of loose sandy soils resulted in more contact of the foundation with the subsoil, and its differential settlement was less than in the case where dense sandy soils were used.