Triaxial shake table testing and finite element modeling of a modular prefabricated bridge-like specimen with restrained rocking piers

This study presents the triaxial shake table testing and finite element (FE) modeling of a modular prefabricated concrete bridge-like specimen with restrained (controlled) rocking piers. Rocking (uplift) of the piers works as a fuse and as a form of seismic isolation for bridges. The tested specimen comprised four equal-height cylindrical reinforced concrete (RC) piers capped with a RC deck. The piers were connected to the deck with unbonded tendons stiff enough to provide positive post-uplift stiffness. The tendons were connected at the top of the deck and at the base of the piers. This configuration reduces the forces transmitted to the foundation, thereby reducing its size and cost. Sliding restrainers prevented the piers from sliding out of position. The specimen was subjected to 184 triaxial shake table tests, to enable statistical validation of numerical models. Subsequently, a detailed three-dimensional FE model of the specimen was developed. The FE model explicitly modeled the structural members, as well as the nonlinearities, the friction and the separation of the surfaces during rocking. Results showed that after 184 design-level shake table tests the system was exceptionally resilient since the specimen showed zero damage and zero residual displacements. In all tests, the peak displacements and tendon forces (TFs) were moderate (below 200 mm in model scale) and the deck torsion was low. The proposed FE model accurately captured the statistical distribution of the experimental tests. The described system could be an alternative to the existing seismic isolation methodologies for bridges.