Seismic Reinforcement On Single-span Frame Primary And Secondary Schools

Single-span frame structure has been widely used in primary and secondary school buildings.With the lack of redundant constraints and the degree of statical indeterminacy,single-span frame structure is a weak seismic system and easily to collapse in the earthquake.Since the wenchun earthquake of May2008,The Standard for Classification of Seismic Protection of Buildings Constructions have proposed that school buildings are raised to B fortification.The Code for Seismic Design ot Buildings(GB50011-2010)have proposed that frame structure is not appropriate for single-span frame.And seismic reinforcement measures have been applied to the existing primary and secondary schools buildings which belongs to single-span frame.This paper introduces the status of the middle and primary school buildings which belongs to single-span frame.Combined with our previous earthquake disaster situation, single-span frame structure of school building s major damage forms are summarized, and analyses the cause of damage.It is simply introduce the reinforcement method for the existing framework.Single-span frame structure with cantilever were respectively added frame columns.shear walls and isolation bearing to reinforce.Sap2000finite element analysis software is used to analyze single-span frame structure and the strengthened structure with the modal analysis and the nonlinear time history analysis.The results of the study show that under seldomly occurred earthquake the inter-story displacement of the single-span frame structure with cantilever in single span direction is larger than the inter-story displacement in multiple cross-direction,close to the limitation in code and easily to collapse.Lateral stiffness of the multiple frame structure is improved.Compared with the inter-story displacement of single-span frame structure, seismic resistant property of the multiple frame structure is better.If the shear wall is one-way layout,the inter-story displacement decreases along the shear wall direction,seismic response intensifies perpendicular to the direction of shear wall,it should be considered a two-way layout.Adopt base-isolated structure with LRB to reinforce the single-span frame.Under frequently occurred earthquake,the lateral inter-story displacement of the isolation structure is reduced by45%at most, the longitudinal inter-story displacement of the isolation structure is reduced by50%at most. Under seldomly occurred earthquake,the lateral inter-story displacement of the isolation structure is reduced by50%at most.The longitudinal inter-story displacement of the isolation structure is reduced by64%at most.Compare the inter-story relative displacement,we find that the seismic performance of the strengthened structure is improved.Adapt base seismic isolated technology to reinforce buildings represent better damping effect.