Method And Practice Of Construction Control Of Extrodosed Cable-stayed Bridge

With the rapid development of the bridge construction, many new bridge types have been produced constantly, and combined structure system develops rapidly, such as the extradosed cable-stayed bridge which is used widely at home and abroad.Along with bridge technology developing, the safety of construction process, the structural linear and stress meeting the design requirements shall be ensured. So the study to bridge construction control has important practical significance. Taking the Dadu River extrodosed cable-stayed bridge as an example, the mechanical behavior, linear control and stress control in the construction process are studied in detail. In order to understand the influence of design parameter on the construction process control and the behavior of the bridge when completed, the changes in the force and deformation of the structure are studied under the condition of different design parameter values.1The common analysis methods about construction control such as: loading step by step method and inverts loading method and the unstress status method are summarized. This paper introduces the main contents of bridge construction control (including linear control and stress control and so on). The working principle and characteristics of the theoretical methods of construction control which includes open-loop control and close-loop control and self-adaptive control are described in details. The application of least square method in parameter identification is briefly introduced.2A finite element model is established. The stress and deformation of the structure are calculated and analyzed in each construction stage by means of construction process analog simulation, thus the construction scheme is proved to be reasonable and feasible. Calculation and analysis for structural performance under different load and their combination are done, The mechanical characteristic is analyzed and design scheme is rechecked according to the results. Based on the checking results on serviceability limit state, an adjustment proposal of prestressed tendons is proposed.3The control methods of stress and linear are presented in details based on the construction control programme for Dadu River Bridge. The thought of this control method contains the following:Ascertain the influencing parameter in light of the difference between the measuring result and the corresponding theoretic value of the status variable (the reference point displacement、stress of the reference section)in every construetion phase. Predict the error in the sequent construetion phases.Calculate the formwork placing elevation in order to guide construction. Results show that linear meeting requirement and stress are within safety range and the completed structure meets the operational requirements. So that the construction control programme is also proved to be feasible.4Structural rsponse is calculated with the variation of design parameters at main construction stage and completed stage.The main parameters and its impact are determined by the analysis of the structural performance, and some advice about construction control is given. Results show that concrete density, beam rigidity and local temperature gradient are the main influence parameters.