Assessment of Simplified Linear Dynamic Analysis of a Multispan Skew Bridge on Steel-Reinforced Elastomeric Bearings

Abstract

The dynamic response of a three-span reinforced concrete deck on steel girder skew bridge supported by elastomeric bearings is investigated both experimentally and analytically. The case study presents modal parameter estimates obtained from a large-scale field deployment of accelerometers supported under a wireless sensor network. Through output-only system identification, the natural frequencies, damping ratios, and mode shapes are extracted for the first 20 structural poles. Linear dynamic analysis of the bridge through three-dimensional finite-element analysis is then performed to provide a comparison between the response estimate predicted under the minimum requirements of multimode spectral analysis dictated by the AASHTO design specifications and the in-service dynamic response. Linear elastic bearing stiffness in the compressive, shear, and flexural states is estimated using independent design specifications set forth by AASHTO and Standards Australia, and modeled with idealized fixity. The case study concludes that linear dynamic analysis provides a well-correlated, yet conservative estimate of multimodal displacement for bridges supported by steel-reinforced elastomeric bearings when bearing stiffness is defined by using either design specification.