Experimental Research On Seismic Behavior Of RAC Reinforced By Hybrid Fiber And Silica Fume

Aiming at the disadvantages of RAC,considering the effect of fiber and silicon powder,the FSR-RAC is made to improve the physical and mechanical properties of RAC.FSR-RAC is a kind of RAC which doped with silicon powder and hybrid fiber to improve the physical and mechanical properties of RAC.It can overcome some shortcomings of RAC beams,columns,joints,frame structures,for example the loose failure of mortar,along the interface of old and new recycled aggregate.Based on the above,the main research work and content of this paper are as follows:(1)Research on the influence of fiber and mineral materials in the RACIn this paper,the mechanical performance test of 234 test cubes in 84 groups was carried out.Three single fiber,a single silicon powder and three FSR were researched,the influence on the morphology and mechanical properties of RAC were analyzed,the main influencing factors and general rules were summarized,and Some conclusions and suggestions are drawn.Mainly include: compared with ordinary RAC,single fiber RAC,adding SF RAC and RAC doped with fiber and silicon powder(FSR-RAC)have many aspects of the upgrade.The cube compressive strength can be increased by about 13.4%,the tensile strength can be increased by about 12.1%,the flexural strength can be increased by about 13.7%,and the elastic modulus can be increased by 24.91%.The stress-strain curves and the relationship curves of the stress-strain curves are fitted and get better incorporation method.When the fiber is mixed with 3:7and the content of Silicon powder is 6~8%,the comprehensive performance of FSR-RAC is better.(2)Test and analysis of the mechanical properties of the FSR-RAC beams and columnsBased on the above experimental results,5 FSR-RAC flexural members and 3FSR-RAC frame column test model are designed.Normal section bearing capacity test and pseudo-static test under low cyclic reversed load are carried out.Under different fiber composite of FSR-RAC,the flexural behavior of beams and the seismic performance of frame columns are studied.For FSR-RAC beam,the curve of FSR content with its cracking moment,internal lever arm coefficient of ultimate moment,short-term stiffness,elastic-plastic resistance moment coefficient are studied;the calculation formula of deflection is established;relative height of compression zone,the maximum and minimum reinforcement ratio are discussed.Draw the following main conclusions: for different content,the cracking moment of the FSR-RAC beam is about1 times higher than that of the ordinary RAC beam,and the yield moment and ultimate moment are increased by about 8%.Meanwhile,the effects of FSR content on the failure mode,the bearing capacity,hysteretic characteristics,stiffness degradation,ductility and energy dissipation of FSR-RAC columns are also studied in this paper.The calculating formula of the bearing capacity of FSR-RAC columns is presented.Test and calculation results show that the yield load of the FSR-RAC column is improved by about 12.5% compared with the ordinary RAC frame column,and the maximum load is about 20%.(3)Test and analysis of the mechanical properties of FSR-RAC jointThrough 3 FSR-RAC frame joints test under low cyclic loading,the failure mode,hysteretic characteristics,ductility,stiffness degradation and energy dissipation capacity of the joint are studied.And corresponding restoring force model is established.Based on this model,the nonlinear finite element analysis of FSR-RAC nodes is carried out by using ABAQUS software.Then,the calculating formula of the shear strength of FSR-RAC joints is established.The results show,under the same conditions,the FSR-RAC joints crack late and the crack width is small,the extension is shorter and the hysteretic curve is full.FSR can effectively improve the anti-cracking ability of RAC,and inhibit the bond slip of the main reinforcement.Compared with the RAC joint,the cracking load,yield load and ultimate load of the FSR-RAC nodes are increased by30%,and the ductility coefficient of the joint core area is increased by about 19%.At the same time,the ductility of the joints is proportional to the amount of the mixture.When the hybrid fiber content Higher than 1%,the ductility of joint is slightly decreased,andthe energy dissipation of the join is also related to the fiber content.(4)Experimental Research on Seismic Performance of Framework Architecture with FSR-RACAbase all,a 1/4 scale,3 span 2 story FSR-RAC frame model was made.With the replacement of 100%,shaking table test of seismic shaking table under various operating conditions were carried out.The seismic performance of FSR-RAC frame in small,medium and large earthquakes were studied.Based on the measured natural frequencies and damping ratios,the calculation method of FSR-RAC frame damage index was proposed,the corresponding damage index curve was fitted and the damage degree of the frame was evaluated in different earthquake.In different destruction state of FSR-RAC framework,the limit value of story drift angle limitation and damage index and structural damage assessment method were put forward.The results show,under frequent earthquake,the FSR-RAC frame beam column and other basic components are basically intact,no visible crack.Under rare earthquake,nodes only have some small cracks,no leakage,and the phenomenon of block and so on.Adding appropriate amount of FSR can effectively inhibit the crack and crack development of the model structure and model is better in seismic bearing capacity and global ductility.The FSR-RAC frame can meet the seismic design requirements of the seismic fortification intensity 8.