Study Of Construction Control And Crack For Xinyang Harbor Low Tower Cable-stayed Bridge

With the rapid development of China’s economy, more and more large infrastructure is being in construction, such as highways and bridges. As a new type of bridge, short tower cable stayed bridges are more and more acceptable and applied for its relatively less cost and good landscape earnings. Setting in the construction of short tower cable stayed bridge in Xinyang harbor, systematic study is conducted on the control of girder’s datum mark and stress in construction and reasons of cracks’ occurrence for box girder 0# are investigated. As a result, construction tips for preventing cracks’ rising are brought, which can provide reference for the construction of similar bridges. Main studying work is as follows:(1) Based on software Midas/Civil, finite element model is established of Xinyang Harbor Bridge using beam element. Construction schemes is divided in detail, and stress of girder in maximum cantilever state is analyzed, which can provided theoretical foundation for the construction monitoring in late stage.(2) Combined with the construction monitoring scheme of Xinyang Harbor Bridge, based on the finite element model of bridge, get the actual values of parameters measured by the construction site, carry on the comparative analysis of the theoretical value and the actual value; revise elastic modulus and bulk density of two parameters by using adaptive control method in the construction monitoring process; the results show that the adaptive control theory based on least squares method can be a good guide of construction work, there is little deviation between theoretical model and the actual structure, measured results show that construction monitoring receive desired effect.(3) Considering the block 0 of the box girders as main component which transfer and bear load, its stress is great and complex distributed. Based on software ANSYS, the finite element model of block 0 is established by using solid elements, which take the role of ordinary steel bars and pre-stressed steel strands in concrete into consideration. By applying the displacement boundary conditions of the whole finite element model, we simulate the stress state of block 0 in maximum cantilever load. The analysis result shows that the block 0 is basically in a state of compression in the force of transverse pre-stressing, longitudinal pre-stressing and maximum cantilever condition. The compressive stress value satisfy the design value and the concrete storage reasonable pre-load. By comparing the stress analysis results and crack distribution, we figure out that the load of maximum cantilever condition can provides the tensile stress for the crack growth but not the main factor of the box girder cracking.(4) This paper introduces temperature field finite element theory of concrete and the method for determining temperature field parameters. Based on software ANSYS, the finite element model is established by thermal element SOLID70 and structural element SOLID65.This paper simulates the stress state of block 0 under the loads of hydration heat, shrinkage and sunshine. According to the value and distribution of stress, we infer that the temperature shrinkage effect are the main causes of cracks. The parameter analysis of stress of upper plate is conducted by adjusting interval age, last layer thickness and linear expansion. The research results show that the temperature crack can be reduced or avoided by adjusting construction parameters. The research results of this paper can provide theoretical references for other similar projects.