Dynamic
soil-structure interaction effects on the seismic response of suspension
bridges |
Manish Shrikhande1,
Vinay K. Gupta 2 |
1Department
of Earthquake Engineering, University of Roorkee, Roorkee-247667, India |
Keywords |
suspension bridges; equivalent stationary excitation;
nonstationary seismic response; dynamic soil-structure interaction;
fixed-base modes; coherency function |
Abstract |
A stochastic approach has been formulated for the linear
analysis of suspension bridges subjected to earthquake excitations. The
transfer functions of various responses have been formulated while including
the effects of dynamic Soil-Structure Interaction (SSI) via the use of the
fixed-base modes of the structure. The excitation has been characterized by
the equivalent
stationary
processes corresponding to the free-field motions at each support and by an
assumed coherency function between these motions. The proposed formulation
considers the non-stationarity in the structural response due to sudden
application of excitation by considering (i) the time-dependent frequency
response functions, and (ii) the order statistics formulation for the peak
factors in evolutionary response processes. The formulation has been
illustrated by analysing the seismic response of the Golden Gate Bridge at
San Francisco for two example excitations conforming to USNRC-specified design
spectra. The significance of various governing parameters on the dynamic
soil-structure interaction effects on the seismic response of suspension
bridges has also been studied. It has been found that the contribution of the
vertical component of ground motion to the bridge response increases with
increasing soil compliance. Also, the extent to which the spatial variation
of ground motion affects the bridge response depends on how significant the
SSI effects are. |