Practice Of Cable Force Optimization And Construction Monitoring For Single-tower Asymmetric Cable-stayed Bridge

Cable-stayed bridge is widely used in bridge construction because of its large span capacity and beautiful structure,especially in some urban areas,it has become the landmark building in the city.The main characteristic of cable-stayed bridge is that the cable force can affect its own internal force and linear state.In the design of cable-stayed bridge,how to determine the cable force becomes part of the key tasks.The construction process of cable-stayed bridge will also have a great impact on the state of the completed bridge.In the construction monitoring of cable-stayed bridge,one of the most important tasks is monitoring cable force.Actual cable force of accurate acquisition is an important prerequisite for the monitoring work.In this paper,with the auxiliary bridge of Suzhou Chang Xu Bridge and the single-tower asymmetric cable-stayed bridge as the engineering background,the finite element software Midas Civil was used to establish a simulation analysis model.Combined with the cable force monitoring of the real bridge,the paper studied how to obtain the reasonable cable force in the completed bridge state and optimize the cable force in the construction process,and explored the influence of temperature on the cable force.The specific work contents are as follows:(1)Various methods of cable force optimization are discussed,and the finite element model of single-tower asymmetric cable-stayed bridge is established.The cable force of bridge is preliminarily determined by the minimum bending energy method,and the optimized cable force is obtained by using the internal force balance method and the influence matrix method.(2)This paper introduces the construction process of cable force optimization method,according to the actual construction process of cable-stayed bridge,completed pour down the method proposed in the early construction of final value,will be completed at the beginning of quasi value generation into the formal model of adjustment and get the final cable force value can meet the requirement of construction process of the linear structure,and according to the completed final value using formal iterative method to obtain the secondary cable force.The upper and lower limits of the intermediate cable force are worked out through the stress analysis of the cable basket in the process of concrete pouring,and the average value is substituted into the model for analysis and adjustment,which can minimize the workload of cable force adjustment.(3)The comprehensive use of frequency method and jack pressure gauge reading comparison correction,the whole construction process of cable force monitoring,can more accurately monitor the cable force changes.Using the correction coefficient correction frequency method formula,combining with the hydraulic jack pressure gauge reading to identify the correction coefficient,using the power function to fit the relationship between the correction coefficient and the stress-free cable length,applied to the subsequent cable force test.The cable with shock absorber has a great influence on the frequency,the energy method is used to deduce the cable force frequency formula with shock absorber on both sides and simplify it.The correction coefficient is also used to correct it.After power function fitting,it is used in cable force monitoring.(4)All-day field test of cable force was carried out in extreme high temperature weather in summer and extreme low temperature weather in winter,and the influence of overall rising and cooling on cable force was simulated by using software.The results show that the cable force decreases with the increase of temperature,and increases with the decrease of temperature.The cable force in the middle of the main span and side span changes relatively little with the temperature,while the cable force on both sides changes relatively large with the temperature.In the construction of cable-stayed bridge,it is necessary to pay attention to the closing temperature of the bridge construction,and try to control it within the range of the design closing temperature,so that the actual force of the bridge is consistent with the design requirements.