Seismic Performance Of Self-Centering Column Foot Joint Based On SMA Damper

For steel frame structures,due to inadequate seismic fortification or other factors,some buildings may appear residual deformation that will not collapse after an earthquake,and the maintenance cost of these buildings is very high,and may even exceed the cost of reconstruction.In this paper,on the basis of SMA(shape memory alloy,short for SMA)damper,several self-repositioning column foot joints with different shear modes were proposed,including four shear forms,namely,ball in type,long circular hole shear plate type,V-shaped hole shear plate type and tooth type.The SMA damper consists of an SMA bar and a matching energy dissipation wedge.The self-centering column foot joint proposed in this paper can greatly reduce the residual deformation of the building after earthquake and reduce the maintenance cost through the excellent self-centering ability of SMA damper.At the same time,the existence of energy dissipation wedge makes it have excellent energy dissipation capacity.In order to explore the optimal solution and verify the seismic performance of the solution in the overall frame structure,the work carried out in this paper is as follows:1.The structure and mechanical model of self-centering column foot joint based on SMA damper are introduced.Based on the relationship between the lateral force and the restoring force provided by SMA damper,a mechanical equilibrium equation was established for four different shear modes of self-centering column foot joints.The relationship between the lateral force and the restoring force provided by SMA damper,as well as the factors that may affect the bearing capacity of column foot joints were studied.2.For the seismic performance of the new self-centering column foot joints,the finite element analysis was carried out by using the finite element software ABAQUS.Based on the reliability of the SMA damper model,the influences of different parameters on the performance of the new self-centering column foot joints were analyzed.The analysis results show that the performance of column foot joints is different with different shear forms,and the seismic performance is different with different shear forms.Therefore,its application scope is different,but all shear forms have good self-centering ability and a certain energy dissipation ability.At the same time,the increase of axial pressure leads to the increase of internal friction,which brings different effects on column foot joints with different shear forms.Through analysis and comparison,the new self-centering column foot joint with V-hole shear plate has the best performance.3.In order to study the seismic performance of the whole frame with the new self-centering pin joints,the dynamic time-history analysis is performed through the OpenSees program.The analysis results show that the self-centering frame can effectively control the residual inter-layer displacement Angle of the structure and has a good self-centering effect.The comparison with the OpenSees classic example shows that the new frame structure with self-centering column foot joints can effectively reduce the maximum residual inter-story displacement Angle while not increasing the instantaneous maximum inter-story displacement Angle under seismic action.