Study On Stability Performance Of Steel Box Arch Rib Of Half-Through Tied Arch Bridge

The half-through steel box arch bridge with simple structure and graceful shape is popular among urban bridges.However,the steel box arch rib is a thin-walled member mainly under compression.With the increase of span,the local stability and the local and global dependent stability become the main controlling factors of structural design.It is of great significance to study the stability of the half-through steel box arch bridge for its development to a large span.In this paper,a steel box arch bridge with a main span of 200 m was taken as the engineering background.Based on the general finite element software ANSYS,the whole bridge frame model was established.According to whether the geometrical nonlinearity and material nonlinearity were considered,four kinds of overall ultimate bearing capacity analysis were carried out,and the failure process and internal force change of steel box arch rib were analyzed.The results showed that the main factor determining the ultimate bearing capacity of the bridge was the reduction of section stiffness caused by material nonlinearity,which was less affected by geometric nonlinearity.Then the theoretical basis and design method of local stability in China's current highway steel bridge specifications were researched,and the local stability of steel box arch ribs was checked.The results showed that the specification was too strict on local stability reduction of stiffened plates with flexible stiffeners.And the requirements of rigid stiffeners should be meet as far as possible in the design of steel box arch rib.Finally,a multi-scale finite element model was established to analyze the local and global stability of the steel box arch ribs.Compared with the analysis results of the frame model,it can be concluded that the frame model which failed to consider the interaction between local and global stability will overestimate the ultimate bearing capacity of the steel box arch rib.After the vault segment of the frame model being replaced with a shell element,the live load coefficient was reduced by 17.5% when the structure reached the ultimate bearing capacity.Through the parameter analysis of the number of transverse diaphragm and roof stiffeners in the section of shell element,it can be obtained that when the spacing of the diaphragm is too large,the stiffening plate between the diaphragms will be warped and unstable,which will result in the reduction of the ultimate bearing capacity of the steel box arch ribs.When the spacing of diaphragm reaches a certain value,the improvement of the ultimate bearing capacity of the structure is less by reducing the spacing of diaphragms.The effect of longitudinal stiffeners spacing on the ultimate bearing capacity of steel box arch ribs has the same rule.