Construction Monitoring Of CFST Arch Bridges And Calculation During Erecting Steel Tubular Arch Rib

Since rib-hoisting of concrete-filled steel tubular (CFST) arch bridges is a very complex process, construction monitoring is necessary to satisfy the requirements of design strength and final bridge alignment. Based on the real situation of the Bailu bridge that is under construction in Jian City, Jiangxi Province, the detailed construction scheme is presented, is implemented to determine the rational construction state of a concrete-filled steel tube arch bridge. On the condition that the stability meet the requirement, both deformation and stresses (strains) are monitored where the section deflections of steel tubular arch ribs and the deviation of the arch axis line are key issues. At the same time, the development of stresses (strains) is monitored.There are several shortages on the construction method of cable erection with diagonal fastening and connecting, for example, it requires to adjust the cable forces over and over again, which increases the construction time. The one-off tension method, however, can avoid those troubles and has many advantages. About, the crucial issue of this construction method is to accurately determine the cable forces and the prearranged heights in each phase of erecting arch ribs. In this thesis, a 3-D finite element based optimization method is first established to calculate the cable forces and the prearranged heights during erecting steel tubular arch rib. In this method, the finite element technique is used to model the structure and the optimization theory is applied to the proposed objective function. The cable forces and the prearranged heights in each phase of erecting arch ribs are obtained by the first order optimization method, and the actual construction process of arch rib erection is simulated.In order to facilitate the practical applications, a simplified engineering method is then proposed in this thesis to calculate the prearranged heights in each phase of erecting arch ribs. In this method, the arch rib is considered elastic and the prearranged height is separated two parts: the displacement due to rigid body movement and the displacement due to elastic deformation. The final prearranged height of the arch rib is the sum of two parts. The results of the proposedsimplified engineering method have been compared with those obtained from the 3-D finite element based optimization method. It is demonstrated that the simplified engineering method is feasible. It can be also observed that, and the elastic deformation has the same quantitative level as the displacement due to rigid body movement. Therefore, the rigid body assumption of arch ribs will result in unaccepted error. It can be anticipated that this error will be increased with the increase in the span length of concrete-filled steel tubular arch bridges.In practical applications, the proposed simplified engineering method and 3-D finite element based optimization method can be used complementally. Firstly, the prearranged heights in each phase of erecting arch ribs can be approximately estimated by using the simplified engineering method, and then, the results can be verified again by the more detailed 3-D finite element based optimization method. As a result, the correct cable forces and prearranged heights in each phase of erecting arch ribs can be obtained.