Current Issue

EFFECT OF SHEAR BANDING ON BRIDGES EQUIPPED WITH SEISMIC ISOLATION PADS

Tse-Shan Hsu

Honorary President, Institute of Mitigation for Earthquake Shear Banding Disasters

Professor, Feng-Chia University, Taichung, Taiwan, R.O.C., This email address is being protected from spambots. You need JavaScript enabled to view it.

Lin-Yao Wang

Director, Bureau of Transportation and Public Works, Yunlin, Taiwan, R.O.C.

Yan-Ming Wang

Director, Institute of Mitigation for Earthquake Shear Banding Disasters, Taiwan, R.O.C.

Abstract

In earthquake-prone regions, engineers frequently install seismic isolation pads between the cap beams and girders of a bridge, or between the box girders and piers, to mitigate the effects of ground vibrations by the increase of the damping ratio and the vibration period. However, ground vibrations are a secondary effect of tectonic earthquakes, contributing less than 10% of the total seismic energy. The primary effect is shear banding, which accounts for more than 90% of the energy during such events. This study identifies three critical findings: (1) Traditional design approaches for bridge isolation pads primarily address the secondary effects of tectonic earthquakes, neglecting the predominant shear banding effect; (2) Isolation pads are prone to failure under shear banding; (3) These pads are suitable only for bridges located in regions with negligible shear banding effects. Consequently, this paper advocates for updated seismic design specifications for bridges that consider both shear banding and ground vibration effects to ensure the integrity of isolation pads during tectonic earthquakes.

Keywords: seismic isolation pads, shear banding, ground vibrations, bridge.