Finite Element Analysis Of The Mechanical Behavior Of Box Section Pedestrian Steel Bridge

With the development of modern cities, the traffic of which are becoming more and more crowded. Box section steel pedestrian bridges are thus widely used in order to ease the traffic problem. Unfortunately, most of the existing structures are based on the engineering experiences rather than well-established understanding of the mechanical behavior of this type of structure. Since the bridges are of large dimensions, finite element modeling is a reasonable solution for the analysis of this structure. Based on a model of a real project, this thesis analyzes the finite element model of this bridge and provides several conclusions that may guide the future design of box section steel pedestrian bridges.First, liner elastic analysis of the bridge under design load has been conducted. The results show that the model has a low stress level under design load, the maximum von-mises stress is 88MPa located at the mid-span in the bottom flange.Furthermore, a non-linear plastic analysis is conducted to obtain the failure mode and the ultimate capacity of the bridge. The failure mode is the plastic hinge formed in the bridge surface plate under evenly distributed load, therefore the bridge loses the ability of bearing more load.In the end, on the basis of the understanding of the contribution to capacity and stiffness of each component of the structure, the original bridge is optimized to obtain higher stiffness and ultimate capacity. Also, a non-linear plastic analysis of the optimized structure is conducted to prove the improvement of the stiffness and bearing capacity. The results show a 25% of capacity increase form 5.786 times design load to 7.219 times design load. In addition, the displacement under design load is decreased from 36mm to 30mm, and 150mm to 105mm under 5 times design load, which is a 43% decrease.