Seismic response analysis of a double-deck long-span cable-stayed bridge under multi-support excitations

Abstract

In this article, the effect of earthquake ground motions, especially spatially varying motion, on the seismic response of a long-span double-deck cable-stayed bridge is investigated. Static and dynamic response analyses, with the focus on internal forces on web members, are carried out on the Shanghai Minpu Bridge which is the longest long-span double-deck cable-stayed highway bridge. Firstly, a program for the generation of multiground motions has been developed, based on the multivariate stochastic processes of the weighted amplitude wave superposition method in FORTRAN. Secondly, a refined finite element model composed of beam and shell elements and a simplified model using equivalent beam elements to model girders of the bridge are established in ABAQUS. Geometrical nonlinear static analysis is performed to get initial equilibrium configuration of the bridge for both the above models. Modal analysis is carried out on the initial equilibrium configuration and the natures of mode shapes for the refined model are discussed in detail. The dynamic response analyses under two groups of uniform seismic excitation indicate that the two models result in approximately identical results. Thirdly, the effect of nonlinear viscous dampers, located between the tower and the girder, on movement due to seismic excitation is investigated on the simplified model under uniform excitation. Results show that the dampers magnify the shear force and moment on lower tower columns in the longitudinal direction, but have relatively small effect on the upper tower columns. The shear force and moment of the tower base increase with the damping coefficient in a certain range. Finally, the characteristics of internal force for towers, subsidiary piers, and web members (vertical and oblique web members and side oblique chords) under multipoint excitation are examined. It is concluded that the abrupt changes on the shear envelope curves at the intersection of the tower column and the lower transverse beam are aroused due to the eight nonlinear fluid viscous dampers. The lateral moment of the subsidiary piers increases with the distance from the tower to subsidiary piers. The maximum axial forces of web members of side-span vary acutely, especially those of the vertical and oblique members close to the piers. For side oblique chords, the maximum axial force is uniformly distributed with the exception of members at the piers and the mid-span sections. Therefore, attention should be paid to the fluctuation forces of cables in seismic analysis of long-span cable-stayed bridges, since the uplift of girder ends may cause severe damage to bridges.

Seismic Response of Long‐Span Triple‐Tower Suspension Bridge under Random Ground Motion

“…Third, extract the pseudoresponse of structure and calculate PSD of variables and the variance, RMS, and so forth. Figure 7 depicts the flow chart for the procedure of stochastic response calculation with the initial equilibrium state of the structure considered [33].…”

Dynamic Characteristics Analysis of Long-Span Cable-Stayed Bridge with Steel Truss Stiffening Girder

“…Chang et al [7] used the Rayleigh-Ritz method to explore the mode shapes and final seismic actions of continuous girders on high piers. On the basis of the above, Cui [8] discussed the long-span cable-stayed bridge seismic behaviors under the multi-support excitation, and obtained some new features. All of the previous studies have made great contributions to the bridge dynamic analysis, and lay a very solid foundation for the future studies.…”

Seismic Response of Multi-span Suspension Bridge under Multi-Support Excitation

“…The effect of MSE on response of bridges have widely been studied by many authors (Jiao et al 2013;Ateş et al 2018;Chen et al 2019). Abdel-Ghaffar and Rubin (1983) studied the response of the Golden Gate Bridge to multiplesupport seismic excitation and suggested that for long-span structures, uniform ground motion is not a valid assumption as it does not represent the worst possible condition.…”