۱- Introduction

۲- Fault-crossing bridges damaged in past earthquakes

۳- Bridges crossing potentially active fault rupture zones

۴- Experimental studies

۵- Analytical and numerical studies

۶- Seismic design provisions and recommendations

۷- Summary, concluding remarks, and future directions

References

Abstract

Several earthquakes over the past two decades have demonstrated that bridges crossing fault rupture zones may suffer significant damage due to the combined effects of ground shaking and surface rupture. Although it is widely recommended to avoid building a bridge across a fault, it is not always possible to achieve this objective, especially in regions with a dense network of active faults. This review begins by compiling two databases: one of fault-crossing bridges damaged in past earthquakes and another of bridges crossing potentially active fault rupture zones. The article then continues to review findings of experimental, analytical and numerical studies, and to summarize seismic design provisions and recommendations related to fault-crossing bridges. The review ends with suggestions for future research directions in this area.

Introduction

The vulnerability of bridges crossing active fault rupture zones (called “fault-crossing bridges” in this study) has received increasing attention from earthquake engineers over the past two decades. The impetus was provided by the devastating effects of the 1999 Mw 7.4 Kocaeli, 1999 Mw 7.6 Chi-Chi, and 1999 Mw 7.2 Duzce earthquakes on bridge structures traversed by fault rupture zones. Although it is widely recommended to avoid building a bridge across a fault, it is not always possible to achieve this objective, especially in regions with a dense network of active faults. Active faults that break through the ground surface and have the potential to generate significant fault offset in the event of an earthquake have the capacity to impose a severe combination of ground shaking and surface rupture on fault-crossing bridges. In general, the fault offset may vary from a few centimeters to several meters depending on the earthquake magnitude (e.g., [133]). Similar to nonfault-crossing bridges located in the vicinity of a fault, fault-crossing bridges are subjected to near-fault-pulse-like ground motions affected by forward directivity and permanent translation (fling) (e.g., [81]), but now these ground motions vary across the fault rupture. According to Slemmons and dePolo [111], there are three main types of surface rupture associated with faulting (Fig. 1): (1) primary rupture, which occurs along the primary fault where most of the seismic energy is released; (2) secondary rupture, which occurs along a secondary (or branch) fault subordinate to the primary fault; and (3) sympathetic (or triggered) rupture, which occurs along another nearby fault that is disturbed by the strain release along the primary fault or the vibratory ground motion. It is noted that a surface fault rupture should not be viewed as a fault line, but rather as a fault zone with a finite width subjected to ground distortion. In this study, a faultcrossing bridge is defined as a bridge structure traversed by a surface fault rupture zone (primary, secondary or sympathetic) passing beneath any portion of the bridge (span, pier, abutment or approach road) (Fig. 1).