Construction Control Technology Of Continuous Beam Bridge With Variable Section And Its Application

Since the reform and opening up,China’s bridge construction technology has achieved rapid development.With the development of technology,the span of Bridges is also increasing.Among them,the emergence of Bridges across the Changjiang River,the Huanghe River and the sea is constantly refreshing the world record.However,with the continuous increase of bridge span,the problem of large mid-span deflection after completion of bridge operation has been increasingly concerned by researchers.Based on the Baoding Nanjuma River Bridge of Rongwu Expressway,the linear form and internal force changes of the main girder during the construction process and after the completion of the bridge are analyzed in detail,in order to make the linear form and internal force of the main girder meet the design requirements through the construction monitoring technology.The main contents and conclusions of this study are as follows:(1)In order to study the shrinkage and creep effect of the main girder,the strength and elastic modulus of concrete were tested in the laboratory of the working area.Based on the experimental data and materials collected in the field,the shrinkage and creep effects of the main girder under different shrinkage and creep modes and different influencing factors are analyzed and studied by using the finite element software Madis civil.The results show that fly ash has a great influence on the creep of girder after completion of bridge.The Chinese JTG 3362-2018 prediction model takes the influence of fly ash into account to simulate the shrinkage and creep of the main girder,and the calculation result is more reasonable.In addition,environmental humidity and loading age also have different effects on the shrinkage and creep of the main girder.The shrinkage and creep simulation of the main girder is carried out by selecting the parameters which are in accordance with the reality,and the result is more reasonable.(2)In order to reduce the influence of various errors on the girder alignment and internal force in the construction process,the variation of the girder alignment and internal force in the construction process is closer to the theoretical value.Therefore,during the construction of the main girder,we collect the changes of the linear shape and internal force before and after casting and stretching of the main girder,apply the grey theory to predict the errors of the main girder after casting and stretching,and then make on-site correction to reduce the errors.In addition,in the parameter sensitivity analysis,we introduce the grey correlation theory to the main beam sensitivity analysis.(3)Using the finite element software Madis civil,the finite element model of the bridge is established after fully considering the shrinkage and creep effect of concrete.According to the changes of girder alignment and internal force in each construction stage,the alignment and internal force of girder in the construction process are monitored.Grey theory is used to predict the error between the measured value and the theoretical value in the monitoring process to reduce the error and make the bridge develop towards the design direction.After the bridge is closed,the linear profile of the main girder and the stress of the key section are monitored,and the monitoring results are compared with the theoretical values.The following conclusions can be drawn: the error between the measured and theoretical values of the stress at the key sections is small,which meets the requirements of the code;After the closure of the main girder line to meet the design requirements.