Seismic Performance Study On Intensive Frame For Reinforcement

In 2016,the seismic design code was revised,which greatly improved the design value of seismic action.When the seismic performance of the original structure cannot meet the new requirements,it is necessary to strengthen the original structure.As a kind of universal environmental protection building material,steel has been widely used in the field of structure reinforcement because of its good plasticity and tensile strength,bending resistance,torsion resistance and short installation cycle.At present,the substructure for reinforcement is attached to the original structure which cannot be stressed independently among the numerous methods of adding lateral force resisting system to strengthen the whole frame.Based on this situation,this paper proposed a dense semi-rigid connection steel frame,which is used as an independent whole frame strengthening system.The design concept of this reinforcement system is adding a dense steel frame on both sides of beams in each frame.Defining steel frame for reinforcement on both sides as a group and the maximum section size of the beam and column in each steel frame is not more than 200mm.This two steel frames for reinforcement were connected by side support in each floor and were built on its own foundation to ensure its overall stability and bearing independence.In forms,the dense steel frame's height is equal to the original frame and the density of beam and column across the span and the layer increased,for ensuring the reinforcement system has enough stiffness.In the form of force,the steel frame is subjected to horizontal seismic action from the floor of original structure.At the top,horizontal hinge connections can be set so that it's only subjected to horizontal action rather than bearing vertical load.Joints in dense steel frames adopt endplate connection to ensure the frame has a better ductility performance so that it can work well together with the original framework.Based on the nonlinear analysis results of the joints,a simplified model of dense steel frames for seismic analysis was established and compared with the analysis results of rigid connections under the same parameters,which can verify the feasibility of applying this structure system for seismic vibration reduction.In this paper,the research object is a dense steel frame which was used to strengthen a single span and single layer frame.By using finite element analysis software-Abaqus,firstly,the nonlinear analysis of steel frame joints with semi-rigid connections was carried out,which to study on the effects on ductility,seismic performance,stiffness and stiffness degradation of joints from different parameters such as size and type of beam and column,in different positions include side,mid-side,and corner.Then the joints' size with better seismic performance was selected to establish the whole model of rigid connection and semi-rigid connection frame,comparing and analyzing the seismic performance of concentrated steel frames with two types of rigid connections and semi-rigid connections.Analyzing and prospecting the deficiencies in the study through summarizing the research results,so that we can provide a theoretical basis for the application of dense semi-rigid steel frames with end plate connections in actual seismic strengthening,as an independent reinforcement system.