Comparison Study On Girder Type Of Mid-long Span Multi-pylon Cable-stayed Bridges

For mid-long span multi-pylon cable-stayed bridges, how to choose theappropriate type of girder(steel girder or composite girder), is a practical problembridge designers must face in projects.The purpose of this research is to comparatively analyze multi-pyloncable-stayed bridges using steel girder or composite girder, including the impactto the application of these two types of girder in cable-stayed bridges of variousspan and number of pylons. Further summering up how to choose the type ofgirder,so as a referee to help the bridge designers make a decision.In this study, using finite element analysis and comparison study method, bya three-tower cable-stayed bridge (Hong Kong-Zhuhai-Macao Bridge, Jianghaidirect ship Channel Bridge),the real bridge with steel box girder and compositebox girder. And extension analysis carried out on the basis of that, including thedifferent number of pylons (four pylons, five pylons, six pylons) and differentspan (348m,438m,558m). According to comparative analysis, the followingconclusions can be drawn:⑴Multi-pylon cable-stayed bridge with steel box girder has light dead load,the overall force is relatively small.Multi-pylon cable-stayed bridge withcomposite box girder has relatively heavy dead load.if designing with the samedegree of safety conditions, a larger size cable and pylon should be choosed. Buton the other hand, the overall stiffness of composite bridges is much higher, thestress amplitude is small, the anti-wind performance is much better.⑵In general, the change of numbers of pylons have little effect on theperformance of multi-pylon cable-stayed bridge. But the change of spans havegreat effect on the mechanical performance of multi-pylon cable-stayed bridge.However, the ratio of the performance indicator of cable-stayed bridge withcomposite girder to cable-stayed bridge with steel box girder is almost the same,that is to say, the variation of the span has little effect on the relative performanceof multi-pylon cable-stayed bridge with composite girder or steel box girder.Through this study, although cannot directly draw a conclusion that how tochoose steel box girder or composite box girder in a multi-pylon cable-stayed bridge, but some conclusions can still provide help for comparative research anddesign work to select the girder programs and reduce analysis of the workloadand improve work efficiency.This study is only through finite element analysis from the perspective of themechanical properties of multi-tower cable-stayed bridge with steel box girder orcomposite box girder, through comparative analysis method. But the choice of thetype of girder should not only considere the mechanical performance, but alsoneed to consider various factors, including durability, maintainability andeconomy, should be a multi-faceted, comprehensive, integrated technical andeconomic comparison. In this regard, further deepening of research studies can bedone through finer simulation program.