The Structural Redundancy Evaluation Of Long Span Cable-stayed Bridges

Bridge engineering is an important part of civil engineering and different bridges’bearing capacity and safety are always the keys to keep the fluent of transportation being well.Among all kinds of bridges,the cable-stayed bridges have been widely constructed in the practice of engineering featured with their good economies and practicalities,so the safety evaluation of cable-stayed bridges has also been absolutely critical.Recent years,the research about structural redundancy has grown to be a new hot-spot.There has existed redundancy evaluation of simple structures,such as simply supported girder bridges and continuous bridges,yet no cable-stayed bridges with a great span.So in this dissertation,structural redundancy evaluation of a kind of irregular cable-stayed bridge with long five spans,separate steel box girder,split box towers,four cable planes and a whole floatable system-the Second Wuhu Yangtze River Bridge,is investigated in detail.This method includes several parts such as the bridge performance,ultimate capacity,and damage analysis as well as the results of structural redundancy evaluation can be regarded as a good reference for the same kind of long span cable-stayed bridge.The main contents of this article are:1.The definition and calculation of structural redundancy are discussed in detail.Among these domestic and foreign literatures about structural redundancy and redundancy evaluation,they are all about simple structures,such as simply supported girder bridges and continuous bridges.The structural redundancy analysis of cable-stayed bridges with a great span has not been found,so that has been the purpose of this research.2.The method to calculate the structural redundancy needs the bridge’s ultimate capacity and its loading history curves.Depending on the design material,the FEM of this new bridge has been built.The nonlinear static analysis under four kinds of live load cases have been implemented,which are helpful for the confirmation of live load factors in the four limit states hereinafter.3.To get the results of redundancy evaluation about long span cable-stayed bridges,four limit states have been defined which are member failure states,ultimate capacity states,functionality condition states and damaged condition states respectively.Fifteen damaged scenarios have been set for the overall analysis.Also,the calculation of redundancy based on the method weighted mean has been proposed.4.To consider the characteristics of this cable-stayed bridge,there are four parts of parametrical analysis about this method to evaluate the structural redundancy:the effects of number and spacing of transverse girders;the effects of spacing of main girders;the effects of the stiffness of main girders and transverse girders as well as the effects of capacity of main girders and transverse girders.The results of parametrical analysis not only validate the reliability of this new structural redundancy evaluation method,but also find the main factors for structural redundancy of long cable-stayed bridges.