Technical And Economic Index Research On Improving Seismic Ultimate Bearing Capacity Of Steel Spatial Arch Trusses By Increasing Their Seismic Fortification Level

The general design method in china is "two stage design,three levels of fortification"according to current standard,and the "three levels of fortification" is achieved through "two stage design"method. Generally, building seismic design is mainly based on the current seismic design methods. However,The intensity of disaster earthquake is usually higher than that of the fortification,which will cause a large collapse of the building.The damage of building collapse is davastating,once the building collapse it will cause fatal damage to the people or the things in the building.While China is one of the countries which the seismic activity is strongest and the disaster is most serious.Especially,After the earthquake in Wenchuan on May12th,2008. People reallize the importance and urgency of establishing indoor imergency earthquake shelter. In order to minimize the loss of disaster earthquake, we must research the seismic problem.In this paper, the laege-span arch truss structure with higher bearing capacity is designed and researched by the method of improving the fortification level.So as to provide a reference for the study of indoor earthquke shelter.In this paper, the arch truss of120m-span and0.25rise span ratio steel is studied, the paper carried out the following works:Firstly,deciding the arch truss geometry model according to the different arch truss geometric forms.Secondly, according to the various parameters of Taiyuan area and the kown loads,we can design three different arch trusses with different seismic capacity,then analyze their vibration characteristics. Finally, analyzing the response of three different seismic capacity arch truss under three kinds of different seismic wave,and each wave considering three direction input.Through the time-history anaysis of the three kinds of arch truss we can extract various response index of the structure under the earthquake which conclud maximum displacements, elasto-plastic critical acceleration, the deformation of the structure and yield displacement ratio.Thus we can analyze the destruction process of the structure, failure mechanism, and the economic indicators of three different seismic capacity of arch truss. Through calculation and analysis, we can achieve the main conclutions like the following:1The steel arch truss designed by improving the seismic fortification level can baring greater ground motion acceleration when the structure getting into plastic stage and critical failure stage.And the seicmic bearing capacity has been greatly improved.2Three kinds of arch trass designed by increasing the seismic fortification level suggest that the structrues’seismic ability have improved a lot with less increasing of steel.3The unit weight of the structrue increasing nonlinearly with the increasing of the seismic fortification level.4The structural displacement ductility coefficient has no direct contact with the structure seismic fortification level.5The weakness part of three fortification levels of structure are mainly in the cross,support and one forth distance to the cross.