Mitigating Seismic Irregularity of Continuous Girder Bridge with Unequal Height Piers Through Differential Design of Shear Key Strength

This study attempts to evaluate the effect of transverse shear keys in mitigating the transverse irregularity of continuous girder bridge with unequal height piers through differential strength design. In the current specifications, widely adopted reinforced concrete shear keys are mostly considered as structural measures, while their role in the transverse seismic system of girder bridges is not defined in detail. To explore the potential of reasonable design of shear keys on mitigating the transverse irregularity of multi-span continuous girder bridge with unequal pier heights under different seismic systems, a systematic study is performed based on OpenSees platform. Parametric analysis of the shear key strength is carried out to meet the expected performance objectives of the bridge under different transverse seismic systems. This study leads to the conclusion that rational differential design of transverse shear key strength on different height piers of mid-span continuous girder bridges balance the total transverse stiffness of piers, thus there would be a reasonable distribution of seismic inertia force transmitted from superstructure. This makes the transverse seismic responses of different height piers consistent and seismic performance requirements would be meet under different transverse seismic system. For mid-span continuous girder bridges with different height piers, ductile seismic system can be adopted when the strength of the shear keys is high, and the difference between strength of the shear keys at different height piers should be small. The seismic reduction and isolation system can be adopted in continuous girder bridge with weaker shear keys, while the strength of the shear keys at high pier should be relatively more smaller than that of shear keys at short pier.