The performance of multi-span steel-concrete composite bridges in recent seismic events has shown that these structures are very sensitive to earthquake loading. Extensive damage may occur not only in the substructures, which are expected to yield, but also in the components of the superstructure involved in transferring the seismic loads. Current codes allow the design of regular bridges by means of linear analysis based on response spectrum reduced by a reduction factor reflecting their structural ductility capacity. In bridges whose superstructure transverse motion is restrained at the abutments the sequential yielding of the piers may cause a substantial change of the stiffness distribution. As a consequence force distribution and displacement demand may notably differ from the predictions provided by linear analysis. The scope of this paper is to assess the influence of piers-deck stiffness ratio and piers-deck strength ratio in the post elastic seismic behavior of continuous composite bridges. Some results concerning a three span continuous slab on girder bridge are presented. The dependence of the response on these parameters is studied by means of incremental nonlinear dynamic analysis. The results are then compared with those obtained by means of a linear dynamic analysis. Main focus is posed on curvature demand of the piers, bending moments acting on the superstructures and reaction forces in correspondence of the piers and the abutments.
Influence of abutment restraints on seismic response of multi-span continuous bridges
DALL'ASTA, Andrea;
2008-01-01
Abstract
The performance of multi-span steel-concrete composite bridges in recent seismic events has shown that these structures are very sensitive to earthquake loading. Extensive damage may occur not only in the substructures, which are expected to yield, but also in the components of the superstructure involved in transferring the seismic loads. Current codes allow the design of regular bridges by means of linear analysis based on response spectrum reduced by a reduction factor reflecting their structural ductility capacity. In bridges whose superstructure transverse motion is restrained at the abutments the sequential yielding of the piers may cause a substantial change of the stiffness distribution. As a consequence force distribution and displacement demand may notably differ from the predictions provided by linear analysis. The scope of this paper is to assess the influence of piers-deck stiffness ratio and piers-deck strength ratio in the post elastic seismic behavior of continuous composite bridges. Some results concerning a three span continuous slab on girder bridge are presented. The dependence of the response on these parameters is studied by means of incremental nonlinear dynamic analysis. The results are then compared with those obtained by means of a linear dynamic analysis. Main focus is posed on curvature demand of the piers, bending moments acting on the superstructures and reaction forces in correspondence of the piers and the abutments.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
