Performance Study On Post-earthquake Repair Of Steel Frame-steel Plate Shear Wall With Stiffener

The steel frame-steel shear wall is a disaster-reducing and easy-to-repair structural system with an ideal failure mechanism of “first wall panel,rear frame”,which acts as a fuse in the structure.In the case of moderate earthquakes,the inner steel plate is subjected to buckling deformation,but the frame can still maintain elasticity without residual deformation,and the structure still has a high safety reserve.If you replace or reinforce the "fuse"(internal wall panel)at this time,it will be a convenient and effective way to repair.On the other hand,repairing the damaged structure after the earthquake will help people to quickly resume normal production and life,while avoiding the huge waste caused by the demolition.In the context of this practical significance,this paper will combine the performance characteristics of steel plate shear wall to propose the repairing method of installing steel stiffeners.The combination of theoretical research and finite element numerical simulation is used to study the seismic performance of repaired and non-repaired specimens.The variable-parameter analysis is carried out from the two aspects of repairing and repairing structures;the shear force and axial pressure of frame columns after repairing are explored..The main contents are as follows:(1)In order to ensure the accuracy of the model establishment,firstly use the finite element software ABAQUS to perform numerical simulation verification according to the test.The results show that the development of stress and strain in the finite element calculation results is in good agreement with the experimental phenomena,which can reflect the force mechanism and deformation of the test piece.The hysteresis curves of the two are similar in shape,and the finite element can simulate the pinching phenomenon.The skeletal curve of the two is highly consistent,and the difference of yield load,ultimate load and initial stiffness is small.The finite element model can provide a reliable basis for subsequent research.(2)Proposing the repairing method of anchoring steel stiffeners on both sides of the wallboard,carrying out two-stage quasi-static repeated loading on the three sets of stiffening repair models,simulating the structure once in the loading phase I,and then using the “life and death unit” "Repairing is carried out.In the loading phase II,the structure is subjected to secondary earthquakes,and the seismic performance after structural repair is studied.The non-repaired specimens are compared and analyzed.The results show that the structure enters the elastoplastic working stage after the damage,and the stiffness drops sharply.After repair,the initial stiffness of the structure can be restored to before damage.The stiffener can effectively restrain the out-of-plane deformation of the wallboard and improve the pinching phenomenon of the hysteresis loop.Compared with the non-repair model,the energy consumption performance,yield load and ultimate bearing capacity of the repair model are significantly improved.The repair method also has the advantages of convenient transportation,quick installation,good economy and the like,and is a convenient and effective repair method.(3)Perform parameter analysis of the repair effect,and change the parameters of “stiffening mode” and “to-be repaired structure”.First change the number of stiffeners,the form of the section,and the way it is installed.Determine a better repair method.Further,the high-thickness ratio of the repaired test piece and the internal filler material are changed,and the applicability and repair effect of the repair method are analyzed.The results show that if the number of stiffeners is increased and the area of the wall panel is reduced,the energy consumption performance of the structure after repair is more significant,but the ultimate bearing capacity is limited due to premature failure of the column foot.The repaired structure is contrary to the design concept of “strong frame,weak wall panel”.The column foot is damaged earlier than the wall panel,and the structure does not meet the requirements of “multi-channel fortification”.When the stiffening stiffness of the stiffener reaches the threshold stiffness,the stiffeners with different cross-sections have no significant effect on the repair effect.The welding fixed connection method is equivalent to the bolt anchoring repair effect,and it is not recommended because it is inconvenient to operate and easily damage the wall panel.For specimens with different high-thickness ratios,stiffening repair can improve the seismic performance of the structure.The smaller the high-thickness ratio,the better the energy consumption and initial stiffness improvement effect.In the case of non-energized steel wall with low yield point,the wall panel can yield evenly and fully,and the hysteresis curve is full.Therefore,the stiffener cannot fully exert its improvement effect on the wall panel,and the repair effect is not good.(4)Theoretical analysis of the force of the frame column,and the shear force and axial pressure of the section on the column were extracted by numerical simulation.The changes of the shear force and axial pressure of the frame column before and after stiffening were analyzed.The results show that after the stiffening,the maximum shear force of the column is greatly reduced,and the shear force difference between the top and the bottom of the column is reduced;the maximum axial pressure of the column is increased slightly,and the pressure difference between the top and the bottom of the column is increased.The reason for this change is that the force mechanism of the wallboard changes after the stiffening,the horizontal force of the wallboard to the column will decrease,and the vertical force will increase.For this reason,the concave deformation of the frame column is improved to avoid the hourglass phenomenon.In general,stiffening repair is beneficial to improve the stress of the frame column of this layer.After stiffening and repairing,the shearing force and axial pressure of the column foot will increase greatly due to the increase of the structural bearing capacity and the increase of the overall rigidity.In order to prevent premature failure of the column foot,it is necessary to reinforce the column foot after repair to avoid the concept of “multichannel fortification” against the structure.