Many studies have been conducted to investigate the seismic fragility of regular girder bridges, whereas only a few studies have focused on irregular cable-stayed bridges. In this study, the performance of a medium-span concrete cable-stayed (MSCCS) bridge is investigated by developing its component and system fragility functions. Structural analysis software is used to build the finite-element model of the case study bridge, and the ground-motion bin is assembled to match the practical site condition. The spectral acceleration at the geometric mean of the two periods of both longitudinal and transverse directions is applied to develop the component fragility functions. Analyses show that the bearings and transverse retainers are the most fragile components, whereas the failure probabilities of the concrete towers are relatively lower. This study proposes a user-friendly and efficient framework for establishing the system fragility functions on the basis of serial system assumption. Moreover, the ...

This paper proposes an alternative time-dependent seismic fragility assessment framework considering the variable correlation of structural random parameters for aging highway bridges subject to non-uniform chloride-induced corrosion attacks. The proposed systematic framework is implemented to perform a probabilistic time-dependent seismic fragility assessment for a typical multi-span reinforced concrete continuous girder (MSRCCG) bridge. Effects of non-uniform chloride-induced deterioration on the time-evolving seismic capacity, seismic demand of reinforced concrete (RC) columns, and the time-dependent seismic fragility of the case-study bridge are investigated using nonlinear sectional moment-curvature and nonlinear time history analysis. Furthermore, this paper performs comparative studies to investigate the influence of variable correlation of structural random parameters on the time-variant seismic capacity, seismic demand of RC columns, and time-dependent seismic fragility of the case-study bridge. The results indicate the following conclusions: (1) Non-uniform chloride-induced corrosion may change the vulnerable position and the damage mechanisms of RC columns; (2) Due to non-uniform chloride-induced deterioration, the flexural capacity and curvature ductility of RC columns may exhibit a nonlinear reduction, while there is a nonlinear accelerated growth of time-dependent seismic fragility for aging highway bridges along their service lives; (3) The time-variant seismic capacity (i.e., the flexural capacity and curvature ductility) and seismic demand of RC columns tends to have a certain reduction and increase by ignoring the variable correlation of structural random parameters, respectively; and (4) The time-dependent seismic vulnerabilities of aging highway bridges may be overestimated by ignoring the variable correlation of structural random parameters.

The huge axial force in the main girder challenges the design of superspan cable-stayed bridges. To reduce the self-weight of the girder, the conventional orthotropic steel deck (OSD) system is widely adopted due to its high strength-to-weight ratio, which may generate fatigue problems. In this paper, the optimum combination of different bridge and deck systems was studied by designing a cable-stayed bridge with main span of 1,480 m. Two different bridge systems were investigated: the conventional cable-stayed bridge system and a partial ground-anchored cable-stayed bridge system with crossing stay cables (the new bridge system). Additionally, in each bridge system, three different deck systems were studied: the OSD system, a composite deck system composed of the OSD system and an ultrahigh-performance concrete (UHPC) layer, and an UHPC waffle deck panel system. Finite-element (FE) models of the six plans were developed and analyzed. The static, dynamic, and economic performances of the six plans were compared. Model tests of the composite and UHPC waffle panel systems were performed to ensure the feasibility of the design. Compared to the conventional bridge system, the new bridge system has a much smaller axial force in the main girder, greater longitudinal stiffness, and economic advantages. Under the traffic load, a much lower stress amplitude is developed in the girder with the UHPC waffle deck panel system than in girders with the other two deck systems. Compared to the OSD system, the composite and UHPC waffle panel systems are advantageous in terms of lifecycle cost. Therefore, the combination of the new bridge system and the UHPC waffle deck panel system is recommended as the optimal design plan.