Response analysis of a seismic isolated railway bridge under service and earthquake loading

Student: Seokho Jeong
Supervisors: Dr Nicos Makris

ABSTRACT

This thesis investigates the dynamic response of a newly constructed five-span prestressed concrete railway bridge equipped with friction pendulum bearings and fluid dampers, taking advantage of the state of art in the substructural modeling methodology. ΣΓ-12 bridge is currently under construction in the center of Greece between Lianokladi and Domokos.

First, the structural behavior of each substructural component is examined and expressed by a macroscopic force-displacement law. Subsequently, the bridge is modeledwith a simple discrete finite element model that synthesizes the individual behavior of the various substructural elements, including the equivalent beammodel that accounts for the soil-structure interaction. A new element model is implemented that takes into account the axial force dependency, rate dependency and the bi-directional coupling behavior of the friction pendulum bearing. Seismic response analyses for both the non-isolated bridge and the isolated bridge are conducted in the time domain, using OpenSees, to capture the nonlinear behavior of the seismic protective system, accounting for the potential effect of soil-structure interaction. The effect of soil-structure interaction on the seismic response of both the non-isolated bridge and the isolated bridge is identified and discussed.

The study concludes that the seismic isolation brings a significant amount of reduction in the base shear, while the supplemental damping successfully reduces the excessive deformation demand on the isolation devices. Although it is not the case in the response of the non-isolated bridge, the soil-structure interaction seems to be almost always beneficial for the seismic isolated bridge.

You may download a digital version of this MSc dissertation here.