The Influence Of Truss Support Stiffness On Seismic Performance Of Hybrid Structure Of Gymnasium

Civil Engineers usually separate mixed structure which has steel truss up and reinforced concrete frame down to design them in practical. But in recent years, the research shows that separated method can not consider the coordination of deformation capacity accurately for each other,compared with the whole modeling analysis, the result of earthquake is quite different.Whether the separated design method or the whole modeling analysis, it is reasonable to consider the bearing stiffness.But in the current engineering design, there is no reliable reference for the value of the grid bearing stiffness, especially the influence of the stiffness variation of the grid bearing on the seismic performance of the overall structure is not clear.In this paper, three kinds of typical gymnasiums structure designed according to the 7degree of earthquake resistance were selected,then established the whole models by considering the truss support stiffness.Then modal analysis, static analysis and dynamic elastic plastic time history analysis were performed,to research the influence of truss support on the seismic performance of the whole structure in minor,moderate and major earthquake under 7 degree fortification.The static analysis of steel plate bearing which usually used in small and medium span steel truss was carried out in this paper.The change law and value of the stiffness of were obtained. Choose three different stiffness of steel plate bearing, establish the overall models in SAP2000 software, then modal analysis, static elastic plastic analysis and dynamic elastic plastic time history analysis were performed,to research the influence of steel plate bearing stiffness of the overall structure on the self vibration characteristics, the PUSHOVER curve,performance point, truss force, inter story displacement, base shear and plastic hinge development.Change the truss support to rubber bearings and lead rubber bearing,then modal analysis and the elastic plastic time history analysis were performed on the overall structure,to research the influence of truss support stiffness on the seismic performance.Through the above analysis: It was concluded that the lateral stiffness were in the rangeof 247.14kN/mm ~ 489.45kN/mm.The change of steel plate bearing stiffness has little influence on the pushover curve, performance point and the plastic hinge of the gymnasiums according to the static elastic plastic analysis.The change of steel plate bearing stiffness has mush influence on axial force of truss,but has little influence on concrete frame column displacement, base shear, interlayer displacement angle, plastic hinge development according to El Centro wave dynamic elastic-plastic time history analysis.The gymnasiums structures by using the separated design method can meet the requirements of the standard, but in the large earthquake, the local bars are damaged seriously and the displacement is larger.The seismic performance of single open type gymnasium structure is weaker than the mixed structure with the subsidiary frame and the mixed structure of multilayer frame structure with sports classroom in the top.The stiffness change of rubber bearing and lead rubber bearings have much effects on axial force of truss,but has little influence on plastic hinge development.Overall,the ordinary rubber bearing and lead rubber bearing, has the better seismic performance than steel plate support.