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In this paper, the reliability of a cable-stayed bridge with a span of 640m is investigated and compared in three different scenarios. While both the first and second scenarios assumed a fixed end for the bridge supports used, they differed in terms of material and geometric behavior. Finally, the third scenario differed from the second by incorporating a soil–pile–structure interaction (SPSI) to account for the flexibility of the underlying support. This study accounts for uncertainties in the structure, pile, and soil parameters. The Latin hypercube sampling (LHS) method and dynamic time history analysis were used to estimate the structural responses. Artificial earthquake records at four different risk levels are used for the dynamic time history analysis. Using the machine learning method, several additional results were generated and used in the seismic reliability evaluation. In the case where the SPSI was a simulation, the reliability analysis showed a higher probability of cable failure than other criteria. The element of the tower in the fixed support case also has a high probability of failure. The results of the reliability analysis of the nonlinear models showed a higher probability of failure for a cable-stayed bridge on flexible support than on fixed support.

This paper deals with the stability of the pylons of a cable-stayed bridge under the action of time-dependent loads, due to the vibration of the bridge deck. The stability of such problems of cable-stayed bridges is solved by a technique developed in the Laboratory of Metal Structures and Steel Bridges, of National Technical University of Athens (NTUA), as well as Bolotin's technique for the solution of nonlinear problems of dynamic stability. Three cases are studied: pylons with damping, pylons under forced vibration, and pylons subjected to an arbitrary external dynamic load. Useful relations are established by the aforementioned solution method, examples for a variety of pylons are presented, and interesting results regarding the stability of each case are given in diagrams.

A mathematical model suitable for static and dynamic analyses of curved-in-plane cable-stayed bridges is proposed. By expressing the tensile forces of the cables in relation to the deck and pylon deformations, the problem is reduced to the solution of a beam curved-in-plane that is subjected to the usual permanent and external loads and to the tensile forces of the cables, the latter being functions of the deformation of the beam. The theoretical formulation presented is based on a continuum approach, which is suitable for the three-dimensional (3D) analysis of long span cable-supported bridges. Numerical examples will be analyzed to illustrate the applicability of the proposed approach.

Cable-stayed bridges carrying urban rail transit are often equipped with rail expansion devices (REDs) to avoid possible breaking or buckling of the rails. Such devices not only increase construction and maintenance budgets of the track system, but also endanger ride comfort and safety of the trains. Therefore, the maximum expansion length of cable-stayed bridges without the adoption of RED is investigated and presented in this paper. Finite element models of cable-stayed bridges with various lengths are developed based on design parameters of existing bridges with similar lengths. A friction-spring model is utilized to simulate the nonlinear resistance history of fasteners under various loading cases. Track–bridge interactions are then studied by varying the longitudinal restraint conditions for the cable-stayed bridges. The investigation reveals that the admissible overall rail stress allows a maximum expansion length of about 400m for urban rail transit double-tower cable-stayed bridge paved with the ballastless track and WJ-2 small resistance fasteners. This finding provides theoretical bases and practical guidelines for the saving of REDs for many large-span urban rail transit bridges in future design.

Structural health monitoring (SHM) of cable-stayed bridges requires periodic assessment for the deteriorating stay cables to ensure a long-term service life of the bridge. However, conducting the non-destructive SHM for operating cable-stayed bridges and analyzing the safety statuses of all the working cables are still challenging, due to the lack of in situ cable data for previously constructed bridges. This study developed an innovative framework of health condition assessment for stay cables based on cable vibration frequencies from an interferometric radar (IBIS-FS) using engineering reliability analysis (ERA). Taking a cable-stayed bridge in Victoria, Australia as a target structure for the case study, it shows that the presented framework can remotely monitor the accurate real-time load bearing conditions of stay cables by calculating tension forces, and effectively assess their health conditions. The results show that the natural frequency (up to the fifth mode) of a healthy cable remains constant under different external loadings but varies for damaged cables. The measured reliability index of all the stay cables is higher than the safety threshold factor at ultimate limit states, while one carries tension force higher than the maximum design load (lower than the minimum breaking load) and other three cables need to be monitored regularly due to their low reliability indices. This is attributed to an integrated effect of applied tension force, cable diameters, and minimum breaking loads.

The intensity measures of ground motions are closely related to the damage of bridge structures. However, it is difficult for engineers to select these parameters to predict the potential damage of cable-stayed bridges under earthquakes. This paper investigated the correlation between the intensity measures of far-fault ground motions and the damage of cable-stayed bridges. 322 far-fault ground motions were selected, and 26 available intensity measures in the literatures were chosen to carry out comparative analysis on a cable-stayed bridge with a single pylon. The nonlinear finite element model of this bridge was built, considering the stiffness degradation of concrete and low-cycle fatigue effect of steel. It is concluded in this study that velocity spectral intensity (VSI) is the optimal intensity measure for seismic damage analysis of cable-stayed bridges subjected to far-fault ground motions, followed by spectral acceleration at fundamental period and Housner intensity. Five commonly used intensity measures, namely peak ground acceleration (PGA), the ratio of PGA to peak ground velocity (PGA/PGV), specific energy density (SED), predominant period (T_p) and mean period (T_m), demonstrate low correlations with the bridge damage. In particular, there is very weak correlation between the conventionally used PGA and the seismic damage of cable-stayed bridges.

To investigate the effectiveness of viscous damper on seismic control of single-tower cable-stayed bridges subjected to near-field ground motions, a 1/20-scale full cable-stayed bridge model was designed, constructed and tested on shake tables. A typical far-field ground motion and a near-field one were used to excite the bridge model from low to high intensity. The seismic responses of the bridge model with and without viscous dampers were analyzed and compared. Both numerical and test results revealed that viscous dampers are quite effective in controlling deck displacement of cable-stayed bridges subjected to near-field ground motions. However, due to near-field effects, viscous damper dissipated most energy through one large hysteresis loop, extensively increasing the deformation and damping force demand of the damper. Further study based on numerical analysis reveals that to optimize deck displacement of cable-stayed bridges during an earthquake, a viscous damper with relatively larger damping coefficient should be introduced under near-field ground motions than far-field ones.