The Control Research On Construction Of Prestressed Concrete Continuous Beam

With the rapid development of cantilever construction method and prestresstechnology, the use of prestressed concrete continuous beam is becoming wider andwider. Many problems, meanwhile, have been exposed during the highly complexconstruction process of prestressed continuous beam cantilever, such as closuredifficulties, bad bridge line shape and structural instability caused by unreasonableconstruction monitoring. The construction monitoring, therefore, becomes of vitalimportance during the construction of prestressed concrete continuous beam. Therecent years have witnessed China’s rapid development of high-speed railwayconstruction, while ballastless tracks have been used widely in newly-built expressrailways, thus requiring stronger control of bridge deck deformation. For this reason,great emphasis should be laid upon the construction monitoring during bridgeconstruction.Taking the prestressed concrete continuous beam (48+80+48) m bridging overthe Shun-an river in the Ning-an railway as a case study, the thesis studies theconstruction control of prestressed concrete continuous beam of express railway’sballastless tracks, and aims to complete the following tasks:1. Combined with the construction characteristics of the bridge, the thesiselaborates on the main principles and methods of the bridge construction, andanalyzes the key factors affecting the construction control. These factors were alsotaken into account in the process of construction simulation.2. Considering the effect of shrinkage and creep of concrete, the thesis conductssimulation analysis of the designed proposal by a series of special FEM software forbridge structure. In this thesis, the internal force of the structure is achieved by theemployment of Dr-Bridge, and analog simulation of construction process is executedby MIDAS/Civil which is the special FEM software for bridge structure. Throughthese steps, pre-camber, deflection of the construction stage and theoretical value ofstress are achieved, thus providing theoretical foundations for construction control.3. The thesis proposes the methods of predicting and adjusting the line shape ofthe bridge, by which each construction stage’s formwork placing elevation could becontrolled reasonably. The line shape of the bridge, therefore, can be kept well whichmeets the requirements of design. 4. By establishing monitoring system, the author of the thesis executes the fieldmonitoring of deflection and stress during the construction stage. Through aComparison between the measured value and the theoretical value, the thesis analyzesthe error and its reasons. The result shows that the deflection and internal force are allat a reasonable level, and the completed bridge has an excellent closure and a prefectline shape.