Research Of The Cable Force Change Rules And Influence Factors Of Cantilever Cast-in-Place Concrete Cable-Stayed Bridge

Based on engineering example, this paper analyses the change laws of cable force of concrete cable-stayed bridge with slight geometric nonlinearity. The finite element software, MIDAS CIVIL, was usedto establish the bridge simulation model, which was used to analyze the construction stage andservice stage. Change laws of cable force in construction stage and service stage, respectively, are observed in detail. Change laws of cable force in normal construction phase are obtained by means of normal construction analysis and those in cable force adjustment phase are obtained by means of force adjustment analysis. Errors caused by the weight calculation of main girder,installment of template and weight measurement of suspended scaffold are discussed and the sensitivity of cable force by these errors is presented. The risks due to cable break for each position in each condition are compared and the change characteristics of cable force taking into account of the concrete shrinkage and creep from construction stage to service stage are observed through simulation analysis.The result shows that the cable force of concrete cable-stayed bridge increases first and decreases afterwards with the process of balanced cantilever construction, and the decreasing period shows a linear tendency. In cable force adjustment, force change of one certain cable effects other cables in a linear way and the results don’t change from different sequences because the force adjustment is very slight. The cable force is effected significantly by weight errors of girder, less significantly by weight errors of template, and slightly by random errors of template installment. Cable break has a significant influence on the bridge construction, making force increase for cables in the surrounding area and possibly decrease for cables in the distance. When cable replacement is needed during service stage, operation replacing short cables and median cables at the same time should be avoided. Furthermore,Force of cable near bearing becomes lower under the effect of concrete shrinkage and creep, the effect level decreasing with the distance between the bearing and the cable increasing, which is a characteristic whose obvious degree is related to span and section stiffness. The longer the span is and the less the section stiffness is, the more obvious the characteristic will be.