Abstract
Multiframe PC box-girder bridge with intermediate hinges is a kind of bridge having complex structural characters, which is very quintessential in California. In this study, a typical bridge was adopted to establish a nonlinear dynamic model through OpenSees platform. Intermediate hinge and inhibiting devices in it were elaborately simulated. Meanwhile, pushover analysis was used to reinstate a specimen of column test, which has the similar ratio of reinforcement to the typical bridge, and the hysteretic model parameters of the longitudinal steels inside columns were obtained. The damage indexes of column and hinge, which are primary components, under different limit states were acquired by moment-curvature analysis. Taking into account the uncertainty, nonlinear time-history analysis of the bridge was carried out through a suite of synthetic ground motions. Subsequently, a probabilistic seismic demand model was developed, and fragility curves were further focused on. According to fragility assessment, the conclusion shows that columns and hinge restrainers exhibit high fragility, and bridge system fragility is gradually determined by column fragility along with aggravating of the damage state. Unseating of girder can hardly occur at abutments and intermediate hinges. Moderate limit state could be exceeded in the positions of plug-type concrete structures in intermediate hinges, which tends to create transverse and vertical cracks, furthermore causing reinforcements yield. It indicates that it would severely underestimate the seismic fragility of intermediate hinges without considering the elaborate simulation of hinges.
Highlights
California, where the prestressed concrete viaducts were generally designed to the form of column-girder consolidation, is located in the San Andreas fault [1, 2], which is the part of the Circum-Pacific seismic belt
Considering the limitation of previous works, this study focuses on a multiframe prestressed concrete box-girder bridge with eight spans and double intermediate hinges
In order to estimate the damage to structure during earthquake, fragility analysis has been investigated to represent the probability that the seismic response (D) of an engineering demand parameter (EDP) reaches or exceeds a certain limit state (LS) under the ground motion with a given intensity index (IM)
Summary
California, where the prestressed concrete viaducts were generally designed to the form of column-girder consolidation, is located in the San Andreas fault [1, 2], which is the part of the Circum-Pacific seismic belt. Is type of bridge, called multiframe prestressed concrete box-girder bridge, has been widely used in California and even throughout the United States, due to its perfect integrity and large spanning ability. E previously mentioned simplification tended to ignore the potential damage at the point of hinge, which may have a considerable impact on fragility analysis and risk assessment of the bridges. E previously mentioned findings collectively demonstrate that the multiframe prestressed concrete box-girder bridge has complex characteristics combined with consolidation of girder and column and frame structure. Considering the limitation of previous works, this study focuses on a multiframe prestressed concrete box-girder bridge with eight spans and double intermediate hinges. Elaborate nonlinear analytical models of this bridge, serving as a template of simulation to the similar type of bridge, which accounts for the nonlinear behavior of girders, plug-type hinges, columns, bearings, and abutments, are developed in the OpenSees platform. Fragility curves of bridge components and bridge system are developed, while seismic damage exceedance probabilities are acquired. e study can provide data reference and theoretical basis for seismic damage assessment and preearthquake protection of the same type of bridges
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