Study Of Mechanics Characteristics Of Cable-stayed Bridge With Polygonal Line Tower Of Prestressed Concrete

The prestressed concrete cable-stayed bridge with fold-line tower is a new structure, for its novel structure and unique shape, it has a good landscape. Fumin Bridge, which Located in Shenyang, is the first and the only prestressed concrete cable-stayed bridge with fold-line tower and a single cable plane in the world. Compared with straight tower and inclined tower cable-stayed bridge, its structure and basic mechanical property changes a lot. Based on the finite element theory and the model test, the behaviors and mechanisms of Fumin Bridge were analyzed.The main tower of the cable-stayed bridge subjected to axial force and bending moment transmitted from the cable. Because of the axial loading transmit direction changed at the fold area, a large amount of tension force generated, and the tower wall bended out-of-plane. Due to the request of the structure, cable-stayed bridge with fold-line tower which has been built abroad all used steel tower to solve the stress concentration at the fold area. Based on the finite element analysis and experimental study, the mechanic properties of the key parts on concrete fold-line tower such as cable, tower anchorage area were analyzed.Optimization method of reasonable cable force in the finished and construction cable-stayed bridge was analyzed, and the advantages and disadvantages of each method were obtained. According to the static balance features of the fold-line tower cable-stayed bridge, the design method of the main component of prestressed concrete cable bridge with fold-line tower was introduced. Moreover, the least bending energy method and stress balance method were adopted to determine the reasonable cable force in the finished cable-stayed bridge. Considering the mechanic property of the concrete fold-line tower under construction stage, pouring order of the tower was determined. Least square method and iterative calculation was adopted to determine the initial cable force.Based on the response spectrum and time history method, the seismic performance of prestressed concrete cable-stayed bridge with straight-line tower and fold-line tower under supporting system and asymmetric system were analyzed. The results showed that the dynamic characteristics of prestressed concrete cable-stayed bridge with straight-line tower and fold-line tower basically agreements. The changes of tower shape have little influence to the dynamic characteristics of cable-stayed bridge. The calculated results show that frequency number and integral rigidity of asymmetric system were larger than supporting system. The differences between tower-top displacement and beam-end displacement of the two systems under seismic load were little. So, a costly large-tonnage bearing could be saved when the asymmetric system was adopted, which also gave advantage to the future maintenance of the bridge.Model tests on the full bridge under construction process and finished stage were carried out, and the controlling section stress and the cable force under various loads of main beam were obtained. The experiment results showed the method to determine the finished and initial cable force could assure the controlling section stress of prestressed concrete cable-stayed bridge, and the measured cable force and theoretical value were good agreements with the codes.