Dynamic Response of Sea-Crossing Rail-cum-Road Cable-Stayed Bridge Influenced by Random Wind–Wave–Undercurrent Coupling

Sea-crossing bridges are affected by random wind–wave–undercurrent coupling loads, due to the complex marine environment. The dynamic response of long-span Rail-cum-Road cable-stayed bridges is particularly severe under their influence, potentially leading to safety problems. In this paper, a fluid–structure separation solution method is implemented using Ansys–Midas co-simulation, in order to solve the above issues effectively while using less computational resources. The feasibility of the method is verified by comparing the tower top displacement response with relevant experimental data. From time and frequency domain perspectives, the displacement and acceleration responses of the sea-crossing Rail-cum-Road cable-stayed bridge influenced by wave-only, wind–wave, and wind–wave–undercurrent coupling are comparatively studied. The results indicate that the displacement and acceleration of the front bearing platform top are more significant than those of the rear bearing platform. The dominant frequency under wind–wave–undercurrent coupling is close to the natural vibration frequencies of several bridge modes,such that wind–wave–undercurrent coupling is more likely to cause a resonance effect in the bridge. Compared with the wave-only and wind–wave coupling, wind–wave–undercurrent coupling can excite bridges to produce larger displacement and acceleration responses: at the middle of the main girder span, compared with the wave-only case, the maximum displacement in the transverse bridge direction increases by 23.58% and 46.95% in the wind–wave and wind–wave–undercurrent coupling cases, respectively;at the tower top, the variation in the amplitude of the displacement and acceleration responses of wind–wave and wind–wave–undercurrent coupling are larger than those in the wave-only case, where the acceleration change amplitude of the tower top is from-0.93 to 0.86 m/s^(2) in the waveonly case, from-2.2 to 2.1 m/s^(2) under wind–wave coupling effect, and from-2.6 to 2.65 m/s^(2) under wind–wave–undercurrent coupling effect, indicating that the tower top is mainly affected by wind loads, but wave and undercurrent loads cannot be neglected.

GPS Dynamic Monitoring Experiment and Result Analysis of Long-Span Cable-Stayed Bridge

For the sake of timely appraising the working con di tion of the bridge, measuring the dynamic characteristics of the bridge structur e is very important and necessary. A GPS dynamic monitoring test was carried out in the Wuhan Baishazhou Bridge, which is one of the longest span cable-stayed bridges having been built in China. This paper introduces the experimental imple menting scheme and data processing method. The vibration characteristics of the middle span of cable-stayed bridge are availably obtained by use of the spectra l analytic approach. The measuring results are very identical to the theoretical designed values. The research demonstrates that, with GPS receiver of the high sampling rate and suitable data processing method, the vibration characteristics of the bridge structure can be determined with high accuracy.

Modeling of cable vibration effects of cable-stayed bridges

The analysis of dynamic responses of cable-stayed bridges subjected to wind and earthquake loads generally considers only the motions of the bridge deck and pylons.The influence of the stay cable vibration on the responses of the bridge is either ignored or considered by approximate procedures.The transverse vibration of the stay cables,which can be significant in some cases,are usually neglected in previous research.In the present study,a new three-node cable element has been developed to model the transverse motions of the cables.The interactions between the cable behavior and the other parts of the bridge superstructure are considered by the concept of dynamic stiffness.The nonlinear effect of the cable caused by its self-weight is included in the formulation.Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed model. The impact of cable vibration behavior on the dynamic characteristics of cable-stayed bridges is discussed.

Typical diseases of a long-span concrete-filled steel tubular arch bridge and their effects on vehicle-induced dynamic response

A long-span concrete-filled steel tubular(CFST)arch bridge suffers severe vehicle-induced dynamic responses during its service life.However,few quantitative studies have been reported on the typical diseases suffered by such bridges and their effects on vehicle-induced dynamic response.Thus,a series of field tests and theoretical analyses were conducted to study the effects of typical diseases on the vehicle-induced dynamic response of a typical CFST arch bridge.The results show that a support void results in a height difference between both sides of the expansion joint,thus increasing the effect of vehicle impact on the main girder and suspenders.The impact factor of the displacement response of the main girder exceeds the design value.The variation of the suspender force is significant,and the diseases are found to have a greater effect on a shorter suspender.The theoretical analysis results also show that the support void causes an obvious longitudinal displacement of the main girder that is almost as large as the vertical displacement.The support void can also cause significant changes in the vehicle-induced acceleration response,particularly when the supports and steel box girder continue to collide with each other under the vehicle load.