FEA Analysis For Ultimate Load-carrying Capicity Of Double-deck Highway Steel Truss Bridge

Double-deck Bridge could consider of railways, highways and all kinds of transportation needs, give full play to the bridge site of interest, reducing floor space, save investment. As a bridge structure, steel truss bridge is the most common form of Double-deck Bridge, it have been widely used at home and abroad. The traffic is increasing as China's economic development, phenomenon of overload increasingly serious, stability and ultimate load-carrying capacity problems of double-deck steel truss bridge become more and more concerned about. Now the study for ultimate load-carrying capacity of steel bridge mainly concentrated in steel arch bridge, cable-stayed and suspension bridges, but for steel truss bridge is still insufficient. This paper analyses the stability and the ultimate load-carrying capacity of the Dongjiang Bridge, a double-deck highway bridge, with the universal FEM program. The main results and conclusions are following:(1) Through the analysis of elasticity buckling on the whole bridge, known the main bucking modals of this bridge, and compared the influences of the wind load and the live load to the elasticity stability. The results show that the structure has high stability safety factor. The structural stability is in the most unfavorable state as the dead load, live load and lateral wind load act on the structure simultaneously.(2) The results of geometric nonlinear buckling analysis show that the structural instability is lateral overturning of portal frame. Based on the results of double nonlinear buckling analysis, the integral deformation is small when structure destroyed, and the ultimate load coefficient is far below the results of geometric nonlinear buckling analysis. It shows the carrying capacity of the bridge is controlled primarily by material nonlinearity.(3) Through the double nonlinear analysis for ultimate load-carrying capacity of the bridge, known its overload capacity for live load. Based on the results, study its lapse path tracked and its lapse mechanism, reveal the essential of the lapsing of this bridge and its weakness.(4) The analysis on the factors of the structural carrying capacity shows:â‘ Rigid stiffening chord is the key factor to determine the carrying capacity of the structure, it has great influence on the deformation of the structure;â‘¡Internal force adjustment have certain effect on the carrying capacity of the structure, and the influence on structural force and deformation are favorable;â‘¢Horizontal wind load has little effect on force and deformation of the structure.Conclusions of this paper can provide some reference to the design of the same kind bridge in the future.