The Overall And Local Analysis And Fatigue Life Evaluation Of Through Steel Box Tied Arch Bridge

Steel-box tie-bar arch-bridges have two characteristics of large span capacity and strong adaptability to the foundation. The bridges have great superiority in restricted deck elevation and large clearance under the bridge. However, with the continuous development of the steel structure to be lighter and the wall to be thinner, the analysis of strength, stiffness and stability of the structures becomes more and more important. Furthermore, with the increasing traffic volume, the fatigue problem of welded steel bridges is more and more serious.In this thesis, the Kongli Huaihe River bridge of Huainan City in Anhui Province is analyzed. First, based on the finite element model of the whole bridge, the static and dynamic characteristics are analyzed. Then the multi-scale finite element model of the bridge is built which can simultaneously consider the characteristics of the whole structure and part details, the stress distribution and local stability of arch springing can be gained, moreover, the elasticity buckling and ultimate bearing capacity of the bridge are discussed. Finally, the fatigue life is predicted taking into account of the mean stress effect. The analysis in this thesis has certain theoretical significance and practical engineering value.The main contents and conclusions are as follows:1. Based on the design drawings, the finite element model of the whole bridge is built using the general finite element model software to analyze the stress, deformation and dynamic characteristics of the overall structure.2. As a key sub-structure of the tied arch bridge, the stress of arch foot is very complex, so the multi-scale finite element model of the bridge is built by introducing the multi-scale modeling method. In this paper, the arch foot is simulated using the shell element, and the others are simulated using the beam element and bar element, the master-slave node constraint equation is used for the connection, then the characteristics and stress distribution under various conditions of the local arch spring are well reflected.3. The local and overall buckling mode are obtained through the analysis of elasticity buckling of the bridge, and the influences of the live load and the wind bracing of arch rib on the elasticity stability are discussed. According to the analysis of ultimate bearing capacity on the bridge by considering geometric and material nonlinear, the ultimate bearing capacity and the factor of safety can be obtained.4. Based on the British Standard BS5400, the fatigue lives of critical locations of the bridge are predicted considering the mean stress effect using the Walker equation, the results show that the predicted fatigue lives have a reduction after considering mean stress effect.