Example of application of response spectrum analysis for seismically isolated curved bridges including soil-foundation effects

This paper presents seismic behaviour of isolated curved bridges in the earthquake prone regions.For the seismic isolation of bridges, double concave friction pendulum bearings are placed between the deck and the piers, and the abutments as isolation devices. A curved bridge is selected to exhibit the application for seismic isolation. The mentioned bridge is a three-span featuring cast-in-place concrete box girder superstructure supported on reinforced concrete columns found on drilled shafts and on integral abutments founded on steel pipe piles. Additionally, the bridge is located on site underlain by a deep deposit of cohesionless material. The drilled shaft-soil system is modelled by equivalent soil springs method and is included in the finite element model. The soil modelled as a series of springs is connected to the drilled shaft at even intervals.The multi mode method of analysis is typically implemented in a computer program capable of performing response spectrum analysis. The response spectrum specified for the analysis is the 5%-damped spectrum modified for the effects of the higher damping. Each isolator is represented by its effective horizontal stiffness with a linear link element.As seen from the results of the outlined analysis, usage of the isolation devices offers some advantages for the internal forces on the deck for the considered curved bridge as per the non-isolated curved bridge.The response spectrum analysis is substantially required to make a decision of the displacement capacity of the double concave friction pendulum bearings used in the study.