Experimental Analysis On Seismic Performance Of Existing RC Frames Structures Retrofitted By Precast ULICC Plates

There are a large number of existing RC frame structures in China.The low carbonization and seismic performance improvement of a large number of existing RC frame structures is an urgent problem to be solved.Infills in RC frame structure were designed as non-structural components.The characteristics of the infills exhibited in the actual earthquake damage were not fully considered in the design.Adding anti-seismic line and improving the seismic resilience of the structure will be achieved by infills retrofit according to the mechanical characteristics.In addition,thermal insulation of existing RC frames are unsatisfactory.In order to improve the thermal insulation performance and seismic performance of the existing RC frame structure currently and rapidly,precast ULICC plates are used to retrofit the infilled walls,based on UltraLightweight Insulate composite cementitious prepared in the previous research.Low frequency cyclic loading tests were carried out.The main work contents are as follows:(1)Three 1:2.5 scaled RC frames with infills were designed,including RC frame with full-filled infills(MRC-0),RC frame retrofitted by narrow ULICC plates with rotable connectors(RMRC-1),RC frame retrofitted by wider ULICC plates with fixed connectors(RMRC-2),The process of construction,material property tests and measurement methods were introduced.(2)In order to investigate seismic behaviors of retrofitted RC frame,low frequency cyclic loading tests were carried out.Damage process,hysteretic characteristics,skeleton curve,stiffness degradation,energy dissipation capacity and displacement ductility of three specimens were compared and analyzed.Experimental results show that,compared to the un-retrofitted specimen,shear cracks on columns were reduced,Hysteretic energy dissipation capacity,initial stiffness carry capacity,and ductility,of the structures were improved after retrofit.Seismic performance was improved after retrofit by precast ULICC plates.RC frame retrofitted by wider ULICC plates with fixed connectors performed better seismic behavior.(3)The internal forces of the bonding frame members were studied by experimented data.Flexural moment and shear force of columns,base shear distribution,flexural moment of beams,the strain of cast-in-place slab reinforcement and the effective slab width were analyzed.The results show that the inflection point of columns moved downward.The column shear force decreased,which indicates that the retorfit method can reduce the strut effect on the columns.The inflection point of beams and the effective slab width were affected after retrofit.(4)The finite element analysis(FEA)models were established by ABAQUS.FEA results and tests data were compared.Analysis results show that FEA result fit the test resulits well.The finite element model established according to this method has high reliability.The results of FEA showed that the wire mesh in ULICC plates exhibited a low degree of participation.According to the Mises cloud charts,the compression strut effect was more obvious and the multi-compression strut formed,which had a greater impact on the frame beam while a smaller impact on the frame columns.Shear failure of columns can be avoid after retrofit.Thus,better seismic performance achieved.