Study On Seismic Performance Of Partially-Restrained Steel Frame With High Ductile Fiber Reinforced Concrete Infill Walls Structural System

The high ductile fiber reinforced concrete(HDC)has superior ductility and high damage tolerance,which can improve the concrete toughness obviously and enhance the shear and seismic capacity of structural components.This paper presents a new structural system called Partially-Restrained Steel Frame with HDC infill Walls(SHDCW).Because of the HDC used as infill walls,the shear behavior of the primary structure has significantly improved,and this structural system has greater stiffness,higher carrying capacity and deformability and better seismic performance.The system has good application prospects in engineering.In order to study the mechanical properties of HDC and seismic performance of SHDCW,the experimental research,numerical analysis and theoretical research have been done in this paper.The primary contents and achievements are as follows:(1)Experimental study on the compressive and flexural behavior of HDC.Firstly,the influences of water-cement ratio,fiber fraction,sand-binder ratio and fly ash on the HDC compressive and flexural behavior were analyzed by orthogonal and single factor test,and the results showed that the effect of fiber fraction and water-cement ratio on the toughness and strength of HDC is more obvious.Secondly,the elasticity modulus and Poisson’s ratio of HDC were tested,which showed that the elasticity modulus of HDC is less than half of the RC,and the Poisson’s ratio of HDC is only slightly smaller than that of RC.Finally,the evaluation indexes of HDC flexural performance were studied,and the methods of characteristic point,the modified equivalent bending strength and the equivalent bending toughness were put forward to evaluate the toughness of HDC,which can reflects the great flexural behavior of HDC fully.(2)Experimental study on the seismic performance of SHDCW structural system.Two one-bay and two-story SHDCW specimens on one-third scale were designed,and pseudo static test was conducted.The failure process,failure mode,bearing capacity,deformability,the stiffness and strength degradation,and energy dissipation of SHDCW specimens were studied and compared with the RC infill wall specimens.The shear stiffness and deformation of HDC walls,the deformation of semi-rigid nodes,the slip of framework and the internal force distribution of SHDCW structures were studied.The results showed that the higher toughness of HDC not only can enhance the damage resistance ability and reduce the repair costs after earthquake,but also can control the shear crack development of infill wall and achieve ductile failure mode.The SHDCW has good energy dissipation capacity and deformability,which can control the deformation in minor and moderate earthquake and satisfy the deformation and energy dissipation requirements in major earthquake.(3)Analysis on the structural stiffness and bearing capacity of SHDCW.The lateral deformation of SHDCW structure was analyzed,the formulas for calculating the displacement and lateral stiffness of SHDCW structure were proposed.Assuming that the lateral loads of SHDCW structure is equal to the sum of the horizontal load carried by infill wall and steel frame,the simplified formulas for calculating the yield load,peak load and collapse load of SHDCW structure were proposed.It turned out that the lateral stiffness and capacity calculated by the proposed have good agreement with the experimental results.(4)Finite element analysis of SHDCW structural performance.An entity finite element model was established by ABAQUS,considering the interaction of steel frame and infilled wall.And the influences of seven parameters on the structural bearing capacity,stiffness,displacement and deformation were analyzed,which were the wall thickness,the horizontal distribution reinforcement ratio,the section of steel beams and columns,the joint rotation capacity,the infill wall cross ratio and the spacing of studs.It can be seen that the capacity is mainly affected by infill wall thickness,the horizontal distribution reinforcement ratio,the steel column section,the studs spacing and the infill wall aspect ratio.The studs spacing,infill wall thickness and aspect ratio and the steel column section have obvious influence on the stiffness.What’s more,the displacement and ductility of the structure is primarily affected by the infill wall aspect ratio and the studs spacing.(5)Study on the seismic performance factors of SHDCW structural system.Considering the influence of layers and spans,six SHDCW structures were designed and six finite element analysis models were established by ABAQUS.Static elastic plasticity analysis of SHDCW structures was conducted by pushover analysis method and modified capacity spectrum method.The influences of the span and layer number on the correction coefficient of structural response,super coefficient and displacement amplification coefficient were discussed,and the corresponding recommended values were given.