| Steel-concrete composite beam cable-stayed bridge has a strong span capacity.This type of bridge has superior performance,economical and beautiful appearance,and is now the preferred type of long-span bridge.The structure of composite beam cable-stayed bridge is convenient for construction,with small weight and good navigation under the bridge.Therefore,it is widely used in the traffic construction across the river and across the valley.Cantilever construction is the most common construction method of composite beam cable-stayed bridge.System conversion is the key condition in the process of cantilever construction,and also the key and difficult content in construction control.Due to the characteristics of composite beam cable-stayed bridge,such as system conversion is affected by many sensitive factors,elevation adjustment accuracy is required to be high,and internal force and deformation of composite beam are affected by temperature.In order to optimize the construction process of cable-stayed bridge,the system conversion process of composite beam cable-stayed bridge is calculated and studied.The stress and deformation of composite beam section in the process of support system conversion are analyzed.The problems of improper structure stress and mismatching of beam elevation in the process of system conversion are predicted.And the corresponding solutions are given.Based on the engineering background of the Chibi Changjiang River Highway Bridge,this paper conducts structural static analysis for the transformation of the supporting system during the cantilever construction of the main girder.Calculate the loading and lifting time of the temporary support system,the external force action of the system transformation and the influence of temperature change.Completed the main girder support system from the double cantilever construction state,the single cantilever construction state to complete the bridge state transformation.The following research works have been completed in this paper:(1)Based on the stress-free state method and the formal iteration method,the reasonable completion state and construction state of the cable-stayed bridge are expounded.Taking the Chibi Yangtze River Highway Bridge as the background,the reasonable construction condition and construction condition of the composite girder cable-stayed bridge are determined.(2)BDCMS is used to establish the plane bar model of the Chibi Changjiang River Highway Bridge.The static analysis of the maximum double cantilever state,maximum single cantilever state and complete bridge state is carried out.Provides the data basis for the transition between these three system states.Temperature sensitivity analysis of main girder profile under maximum single cantilever condition is carried out.The influence of temperature variation on the maximum single cantilever state system is analyzed.(3)The stress of composite beams during the transformation of three main systems is analyzed.The results show that the stress state of the composite beam in the cantilever construction process is basically good.And the concrete bridge deck mainly bears the axial pressure.The steel beam mainly bears the bending moment.However,in the process of single cantilever construction,the main girder at the top of auxiliary piers is affected by positive bending moment.And the stress of the composite beam is the focus of construction control.(4)For the closure construction process of the main beam passing through the auxiliary pier and side pier,the main beam alignment before and after the system conversion,the support reaction force change of the support system and the important construction process are calculated and analyzed.The results show that in the construction stage of the main beam passing through the auxiliary pier,in order to ensure the structural stress safety,the stress analysis and prediction of the temporary supporting components are carried out.And the temporary structure is adjusted in time.The scheme of lifting and falling of the temporary pier support can ensure the smooth connection between the main beam and the auxiliary pier.(5)In order to achieve the goal of high-precision closure and safety closure of long-span composite beam cable-stayed bridge,the simply supported jacking method is used to adjust the closure state.The sensitivity parameters of the closure,including closure temperature and jacking force of the jacking device,are predicted and calculated.The results show that the change of closure temperature has a significant impact on the closure state.The simply supported jacking closure method can eliminate the temperature error and achieve the purpose of accurate closure of the middle span of the main beam. |
