Simulation of the seismic performance of the Bolu Viaduct subjected to near-fault ground motions

摘要

The seismic performance of the Bolu Viaduct in the Duzce, Turkey, earthquake of November 1999 was studied via a non-linear, time-history analysis of a multi-degree of freedom model. The viaduct had a seismic isolation system consisting of yielding-steel energy dissipation units and sliding pot bearings. The Duzce earthquake caused a surface rupture across the viaduct, which resulted in excessive superstructure movement and widespread failure of the seismic isolation system. The effect of the rupture was modeled by a static, differential ground displacement in the fault-parallel direction across the rupture. The ground motions used in the analysis contain common near-fault features including a directivity pulse in the fault-normal direction and a fling step in the fault-parallel direction. The analysis used a finite element package capable of modeling the mechanical behavior of the seismic isolation system and focused on the structural response of a 10-span module of the viaduct. This analysis showed that the displacement of the superstructure relative to the piers exceeded the capacity of the bearings at an early stage of the earthquake, causing damage to the bearings as well as to the energy dissipation units. The analysis also indicated that shear keys, both longitudinal and transverse, played a critical role in preventing collapse of the deck spans.