Seismic Response Analysis Of A Long-span Double-arch-support Steel Structure Under Multi-dimensional And Multi-support Earthquake Excitations

In long-span spatial structures, the seismic motion of the bearings on the ground are unsynchronized, so it is necessary to consider the spatial variation effect of the seismic motion. Chinese and European norms have put provisions on the span of conventional long-span spatial structures which need to consider the spatial characteristics. As a long-span double-arch-support steel structure was a new type of spatial structures, seismic response analysis under multi-dimensional and multi-support earthquake excitations was infrequent. It is necessary to analyze multi-dimensional and multi-support seismic response. In this paper, the finite element software ANSYS is applied to analyze the seismic response of a long-span double-arch-support steel structure under multi-dimensional and multi-support excitations. The main works of this paper is as follows:Firstly, in this paper, the analysis theories about the seismic response of a long-span double-arch-support steel structure under multi-dimensional and multi-support excitations are introduced systematically, including the multi-dimensional and multi-support seismic analysis methods, analysis models and seismic motion parameters. Also, introducing the implementation of bearing large-mass method in ANSYS, then carrying out the subsequent research works.Secondly, taking a stadium project which is a long-span double-arch-support steel structure into consideration to study the differences among the multi-dimensional and multi-support seismic response, single-dimensional and multi-dimensional seismic response in single-support under three seismic wave. The results shows that there is a great difference between the multi-support and single-support seismic response under multi-dimension excitation, when the wave velocity was less than800m/s. It suggested that the multi-dimensional excitation should be taken into consideration when designing this project. Otherwise, this structure must have sufficient safety margin if designed on the basis of single-support excitation.Thirdly, taking the span of plane double-arch-support steel structure which is100m,150m,200m,250m and300m respectively to analyze multi-dimensional and multi-support seismic response. The results show that multi-support seismic response is equivalent to single-support seismic response, when wave velocity was more than800m/s. With the decrease of the wave velocity, not the larger span, wave passage effect is more. The span of double-arch-support steel structure is more than200m, wave passage effect to the axial force of the double-arch both have very deep influence.Fourthly, the influence of the direction of seismic wave to multi-support seismic response of double-arch-support steel structure is not obvious, so a horizontal seismic response may represent a multi-dimensional seismic response.Fifthly, the members’ stress ratio as a benchmark, studying on multi-support seismic response under three seismic wave, when the three span of double-arch-support steel structure is200m,250m,300m respectively. The results shows that the most unfavorable seismic wave of different span under multi-support excitation is different, associated with the structural layout and wave velocity. In addition, the weakest position of double-arch-support steel structure is top chords’ arch.Sixthly, based on multi-dimensional and multi-support seismic response analysis of double-arch-support steel structure, optimizing the double arch. It may reduce the influence of wave passage effect and give full play to seismic performance advantage of double-arch-support steel structure under multi-support excitation to improve coordination between the double arch through the rational allocation of the double arch stiffnessThe conclusion of this thesis is valuable for similar engineering.