Failure Mechanism Of Steel Arch Truss With Different Substructure Sujected To Strong Earthquake

With the development of the building construction technology and the improvement of the building functional requirements, large span structure construction was developed rapidly and applied widely. The steel arch trusses was used widely as a long span spatial structures for its graceful sculpt, reasonable force, light weight and adequate stiffness.But the steel tubue arch truss was more instability under dynamic loads for its special performance, and now the dynamic stability study is still in its infancy for the steel pipe arch truss, especially for the arch truss with the substructure. Therefore, the non-linear dynamic stability study under seismic action of the structures is necessary to continue in-depth research.According to the actual project three different substructure arch truss with60m and0.25rise-span was designed:direct landing arch truss structure, lattice column landing structure and H-type steel column landing structure, and analyze there vibration characteristics.Than,Three kinds of seismic waves were choiced for the time history analysis of the structure, through the analysis of the different performance indicators of the structure response to study the seismic performance and buckling modes and failure mechanisms of the different substructure arch truss. Last, H-type steel column landing arch truss structure was choosed to study the seismic performance and buckling modes by changing the stiffness of the H-type steel column. By the calculation and analysis, the following conclusions were reached:1) The different substructure arch trusses were optimized by using the SAP2000software, and the internal forces and displacements of the structures were obtained in the elastic stage. The results showed that:the largest internal forces of the bar in the elastic stage is the lattice column landing arch truss structure and the direct landing arch truss structure internal force minimum; Under the gravity load representative value, the maximum vertical displacement is the H-type steel column arch truss structure, the minimum vertical displacement is the direct landingarch truss structure.2) Through the analysis of the structure vibration characteristics, the maximum horizontal stiffness of the three different substructure structures is direct landing arch truss structure, and the minimum is the lattice column landing structure.The horizontal stiffness is less than the vertical stiffness of the three kinds of structural; the most vibration of the structure is the horizontal vibration, and emerge the complex vibration in the higher modes.3) Three kinds of seismic waves was input in three different substructure arch truss, the time history analysis results showed that:the different structural response caused by different theseismic waves, the Rgb wave input by the horizontal caused the maximum structural response; the Lwd wave input by the vertical caused the minimum structural response. The earthquake seismic capacity of the three different substructure arch trusses is controlled by level waves. 4)The direct landing and the H-type steel column landing arch truss are damaged for strength under the horizontal waves and are damaged for dynamic instability under the vertical waves; The lattice column landing arch truss is damaged for strength under the horizontal and the vertical waves. The direct landing and the lattice column landing arch truss structure are damaged began to1/4of the arch truss under the earthquake, the H-type steel column landing arch truss is damaged began to1/4or1/8of the arch truss. The reason of the dynamic instability of the structure is the structure experiences large plastic deformation, and because of the part of the bar to reach the ultimate strength and stiffness degradation, so that the structure can not maintain the original shape and occure the dynamic instability damage.5) The horizontal deformation capacity and the consumption of seismic energy capacity of the three structure is better than its vertical,that is the delay of the horizontal waves is better and able to absorb more seismic energy.6) By changing the height of the H-type steel column section to change the stiffness of the substructure, then selection the Rgb wave input the structure. The results show that:the overall stiffness of the H-type steel column landing structure increase with the increase of the lower structural stiffness; the seismic capacity under the horizontal waves is weaken with increase of the lower structural stiffness, the seismic capacity under the vertical waves is increase with increase of the lower structural stiffness. The horizontal displacement ductility factor is gradually increasing with the increase of the lower part of the stiffness of the structure, but change of the vertical displacement ductility factor is more complex, first increases and then decreases of the vertical displacement ductility factor as the increase of stiffness of the substructure.