Fragility analysis of high-span aqueduct structure under near-fault and far-field ground motions

Abstract

Previous studies have shown that due to the notable characteristics of near-fault pulse-type (NFP) ground motions, such as large velocity pulse, narrow velocity-sensitive region and long period effect, there are significant differences in the seismic response of building structures caused by NFP ground motions and far-field (FF) ground motions. At present, the effect of NFP ground motions on the damage evolution characteristics of the aqueduct is still lacking. In addition, the current seismic design codes do not provide design recommendations for the dynamic response of aqueduct structures under NFP ground motions. The focus of this manuscript is to quantitatively evaluate the fragility of a high-span aqueduct system under NFP and FF ground motions. For this purpose, 10 as-recorded NFP and FF ground motions are considered, and the aqueduct bearing displacements and pier offset ratios are selected as performance evaluation indices. Then, the copula functions are introduced to establish the fragility curve of the high-span aqueduct system considering the seismic demand correlation of the aqueduct bearing and pier components. The results indicate that under same ground motion intensity conditions, the fragility probability of the aqueduct bearings is significantly larger than that of the trough pier under different performance levels, and should be considered in seismic design. In addition, the fragility probability curve of a single aqueduct component is used to describe the fragility probability of the aqueduct system, which overestimates its seismic performance. The fragility probability of a high-span aqueduct system under NFP ground motions is significantly greater than that under FF ground motions. Therefore, seismic safety assessments and seismic designs for the aqueducts should take into account the influence of NFP ground motions.