Analysis On Ultimate Load Capacity Of The Heavy Support Bridge

As a member in the assembly steel truss style of military bridges, heavy support bridge stands out in the new generation bridges for its rational design, simply fabrication and quick transportation. Its components are light and can be exchanged easily. On the premise of realizing the security and practicability of bridges, it requires the heavy support bridge has small segments and greater load capacity under the demands of the quick and automotive transportation. So the high strength steel material is adopted commonly. But in the working process, because of the structure's special constitution and possible overload, it reaches to ultimate load capacity to lose the supporting capacity with the damages of the material and buckling of the structure. Eventually it causes collapse of the structure. Based on the above reasons, calculating ultimate carrying capacity and determining the safety stock of the structure have important practical significances for the heavy support bridge.From the practical significance, this paper, generalizing the former experience, utilizes the numerical computation and the general FEM program (ANSYS) to simulate the heavy support bridge. At first, the possible most dangerous status during the process of establishment and application is calculated by using the finite element method on the basis of linear elastic theory. Then the status in which the stress of the structure is the largest is chosen to be analyzed. Generally speaking, when the external load approaches to or surpasses ultimate carrying capacity, two non-linear relations that contain the non-linear relation between stress and strain structure and the large deformation of structure occurs. Therefore when analyzing ultimate carrying capacities, the material and geometric non-linearity need considering together, namely adopting non-linear finite element method in entire course.Because the structure contains ultimate load capacities of material and buckling that are both independent and mutual influential, these two ultimate load capacities are computed respectively and compared in this paper. Then the following conclusions are obtained. (1) The limited carrying capacity of heavy support bridge is controlled by the material strength. Before the occurrence of strength damage, this balance is stable. (2) Both the linear method and the one only considering the geometric non-linearity evaluate the limited carrying capacity higher than the real. If the carrying capacity need appraising accurately, both the material and geometric non-linearity should be considered together. (3) By analyzing the limited carrying capacity of material strength damage under the two different load situations, the relevant variable load factors are confirmed. Meanwhile, angled at the most unfavorable situation, the whole limited carrying capacity can be enhanced by enlarging separate bars' rigidity.