Study of Control Techniques for Closure of Long-Span Continuous Rigid-Frame Bridge with High-Rise Piers by Pushing

Long-span continuous rigid-frame bridges are usually constructed by cantilever casting method,which brings great challenges to the control of closure.A continuous rigid-frame bridge on the Tongchuan to Huangling Highway in Shaanxi Province which belongs to part of the Baotou-Maoming National Highway(G65)was taken as the background to study the control techniques for the closure of the bridge of this type by pushing.Combined with the key construction procedure and demands of the closure carried out by pushing,the finite element software was used to build the finite element model of the bridge,so as to calculate the law of pier top displacement along the bridge length under the effect of concrete shrinkage and creep and high-temperature closure as well as the influential law of the pier shaft stiffness and constraint condition on the pushing force.It is concluded that concrete shrinkage and creep and high-temperature closure can result in the girder shortening and pier top displacement along the bridge length,and the pushing of the main girder carried out before the closure can effectively solve the problem.The pushing force should be strictly controlled because it is heavily dictated by pier shaft stiffness and constraint condition and is possible to lead to large structural response.According to the results of the analysis and the related experience,the rational pushing force and closure control parameters are determined.The results of the control indicate that the way of closure carried out by pushing effectively compensates the longitudinal displacement caused by concrete shrinkage and creep and high-temperature closure,and the final closure error suits the requirements and the control precision is high.