Effect Of Local Reinforcement On Overall Performance Of RC Frame Structure

In actual engineering,the local vertical load increases due to the change of the function of local use(such as placing large equipment).The overall bearing capacity and aseismic capacity of the structure meet the requirements,however,the bearing capacity of local members exceeds the requirements of the code.In the actual structural strengthening design,most designers only reinforce these members,but the study about the effect of local reinforcement on the whole structure is rare.The literature shows that there are many experimental and theoretical studies on the load-bearing capacity and seismic performance of structural strengthening at the member level at home and abroad,and there are few numerical simulations on how local reinforcement affects the overall seismic performance of the structure.Therefore,the finite element analysis of the partially strengthened structure is carried out in order to study the effect of local reinforcement on the seismic behavior of RC frame structure as a whole.The main contents of the study are as follows:(1)A six-story frame model is designed by using PKPM.In order to study the influence of the change of local reinforcement position on the whole frame,four reinforcement schemes are designed,namely,one corner and one end of the structure are strengthened asymmetrically,the four corners and the middle part of the structure are strengthened symmetrically.The reinforcement scheme is finally determined by calculation according to the design and construction regulations of the reinforcement code.(2)The modal analysis of the original model and the reinforcement model is carried out by using SAP2000,and the period and mode shape of the structure before and after strengthening are compared.The results show that the quadrilateral symmetrical reinforcement is helpful to reduce the effect of torsion,and the weak position is easy to be produced in asymmetric reinforcement.(3)The response spectrum analysis of the original model and the reinforcement model is carried out by using SAP2000,and the bottom shear of the column without reinforcement,floor displacement and story drift of the structure before and after strengthening are compared.The results show that The intermediate symmetric reinforcement model has a greater influence on the shear distribution of the columns adjacent to the strengthened position.The asymmetric reinforcement at the ends has a greater influence on the shear distribution of the non reinforced side columns at the farthest distance from the reinforcement.The greater the number of reinforcement layers,the greater the deviation between the rigid center and the centroid of the asymmetric reinforcement model.Symmetrical reinforcement can effectively improve the anti-lateral stiffness of the structure.(4)The original model and reinforcement model are analyzed by pushover with SAP2000,and their target displacements under 7 degree seismic fortification intensity are obtained by using the capacity spectrum method.The shear and vertex displacement curves of the base,the performance points,the floor displacement,the story drift and the distribution of plastic hinge of the structure before and after reinforcement are compared and studied.The seismic behavior of the structure before and after strengthening is evaluated.The results show that the overall stiffness of the asymmetric reinforcement model decreases more rapidly than that of the symmetric reinforcement model,and the lateral floor displacement difference between the two ends of the asymmetric reinforcement model increases with the increase of the number of push steps or the number of strengthened layers.When the structure reaches the performance point,the plastic hinge on the frame column of the asymmetric reinforcement model is more than that on the symmetrical reinforcement model,and on the premise of the same total steps,the plastic hinge appeared for the first time in the end of the frame beam of the asymmetric reinforcement model,and the corresponding number of steps in the case of the plastic hinge at the end of the column of the frame was earlier than that of the symmetrical reinforcement model.Therefore,under rare earthquake,asymmetric reinforced structures have more safety reserves.