Abstract

Seismic fragility analysis is often conducted to quantify the vulnerability of civil structures under earthquake excitation. In recent years, besides mainshocks, strong aftershocks have been often witnessed to induce structural damage to engineered structures, including bridges. How to accurately and straightforwardly quantify the vulnerability of bridges due to sequential mainshocks and aftershocks is essential for an efficient assessment of bridge performance. While recognizing the limitation of existing methods, this paper proposes a mainshock integrated aftershock fragility function model, which empirically encodes the effects of mainshocks and retains the simple form of traditional fragility curves. A pile foundation-supported bridge system is modeled considering seismic soil-structure interaction to demonstrate the proposed fragility model. Numerical examples show that the resulting fragility curves incorporate the initial value for the probability of collapse of the bridge system due to a mainshock and the effects of the variable aftershocks conditional on the mainshock. Statistical analysis confirms that the proposed model fits the simulated vulnerability data (e.g., seismic intensities of aftershocks and the response demands conditional a select mainshock ground motion) both accurately and robustly.

Highlights

  • Past earthquake events have evidenced that strong aftershocks may follow the mainshocks.On 12 May 2008, an M-7.9 earthquake struck Wenchuan, China, strong aftershocks followed the mainshock, eight of which range from M 6.0 to 6.5 [1,2]

  • A mainshock-integrated aftershock seismic fragility function model is developed in this study mainshock-integrated fragility model (bridge, is developed in this to estimate the probability ofaftershock exceedingseismic a damage statefunction of a structure building, orstudy other to estimate the probability of exceeding damage state of athat structure under mainshock andaaftershock loads are recorded the pastorearthquake structures) under mainshock and aftershock loads that are recorded in the past earthquake events, in which, the probability of collapse is conditional upon mainshock and aftershock intensity

  • A mainshock-integrated aftershock fragility function model is proposed to calculate the probability of exceeding a damage state of a structure subjected to M-A sequences

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Summary

Introduction

Past earthquake events have evidenced that strong aftershocks may follow the mainshocks. On 12 May 2008, an M-7.9 earthquake struck Wenchuan, China, strong aftershocks followed the mainshock, eight of which range from M 6.0 to 6.5 [1,2]. On 26 October 2015, an M-7.5 earthquake occurred in Afghanistan, and an M-4.8 aftershock was recorded only 40 min after the mainshock [4]. These aftershocks have a high potential to lead to more severe damage to civil structures, especially if the structures are damaged or sustain residual deformation during the mainshock. It is meaningful to investigate the effects of mainshock-aftershock (M-A) events on the probability of failure of engineering structures, including buildings, bridges, offshore platforms, or other types of structures

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