Study On Seismic Performance Of Concrete Filled Double-steel-plate Composite Shear Walls With Encased Steel Braces

Concrete filled double-steel-plate(CFDSP)composite shear walls can simultaneously take the advantages of high lateral rigidity of concrete structure and good ductility of steel plate.Thus CFDSP walls have a good prospect of application in high-rise building structures.The key to the design and application of CFDSP walls is to delay the occurrence of local buckling of external steel plates and to improve the load-carrying capacity and deformation capacity of the corners of the wall(the edge columns and the corners of the middle part of the wall).On the other hand,previous studies have shown that the lateral force performance of the reinforced concrete(RC)shear walls can be significantly improved by setting encased inclined bracing composed of steel bars or profile steel elements.On this basis,a new type of concrete filled double-steel-plate composite shear wall with encased steel braces is proposed in this paper.By setting inclined braces,the lateral rigidity and bearing capacity of the wall and the local buckling performance of the external steel plates are supposed to be improved,so that the seismic performance of the shear wall is enhanced too.The cyclic loading tests,numerical simulation and theoretical analysis were conducted to study the seismic performance of the proposed concrete filled double-steel-plate composite shear wall.The main contents and study results are as follows.(1)The cyclic loading tests on four concrete filled double-steel-plate composite shear wall specimens with encased steel braces were carried out.The variables included whether to set the encased braces,and the lateral stiffness ratio of the braces and the edge columns by changing the width of the flanges of the profile steel.Through the experimental study,the basic seismic behaviors of the specimens were obtained,such as the failure machansim,load-carrying capacity,deformation capacity,stiffness and load-carrying capacity degradation,energy dissipation capacity and strain distribution characteristic.(2)The finite element models for the concrete filled double-steel-plate composite shear walls with encased steel braces were established through the ABAQUS.Four specimens and twenty-seven additional models were analyzed to study the mechanism of force transfer and deformation distribution of the proposed CFDSP shear walls with encased steel braces.The internal force distributions and development of strain between the steel plates and infilled concrete,the failure sequence,the contribution of loading capacity of each component,as well as the influence of axial force ratio,shear-to-span ratio,material strength and steel ratio on the load-carrying capacity and stiffness,were investigated.According to the experimental results,compared with the traditional CFDSP walls,the load-carrying capacity,deformation capacity,ductility coefficient,stiffness degradation,stress degradation and energy dissipation capacity of the novel CFDSP walls with encased braces were significantly improved.(3)Based on the superposition principle of the linear elastic system,the equations for calculating initial stiffness of CFDSP walls with encased steel braces were put forward.According to plastic stress distribution method,the equations for calculating normal section load-carrying capacity were obtained.Through the Chinese Code for structure design,the simplified design equations for the shear capacity of the CFDSP walls with encased steel braces were established.The comparison with the predicted results and the experimental and finite element calculation results showed that the theoretical equations can provide a reasonable assessment.In addition,According to the experimental phenomenon and theoretical analysis,the suggestions of some constrction and design details were proposed,such as the location of welding seam between the flange of braces and the steel plate,and the appropriate limitation for distance-thickness ratio of the steel stiffeners was also suggested.