Analysis On Load Bearing Capacities Of Concrete-filled Multicellular Steel Tube Shear Walls With GFRP Tubes Embedded In CFSTs

Shear walls are widely applied in high-rise and ultra-high-rise buildings to carry vertical loads(e.g.,gravity)and horizontal loads(e.g.,seismic and wind loads)of the structure because of their excellent load-bearing capacity and lateral stiffness.However,with the development of high-rise buildings rapidly and the increasing requirements of seismic performance,the development of steel-concrete composite shear walls with excellent performance and convenient construction has become a key research point for scholars at both domestic and overseas.Concrete-filled multicellular steel tubes shear walls are increasingly used in high-rise and ultra-high-rise buildings because of their superior mechanical performance and deformation capacity and other characteristics.In order to further improve the mechanical properties of Concrete-filled multicellular steel tubes shear walls,FRP-confined concrete with good load-bearing capacity and deformation capacity was applied to the concrete-filled steel tubular columns in this composite shear wall,and the concrete-filled multicellular steel tube shear walls with GFRP tubes embedded in CFST columns was proposed.In this paper,the theoretical analysis of load-bearing performance and capacity of the concrete-filled multicellular steel tubes shear walls with GFRP tubes embedded in CFST columns is carried out by combining the results of the experimental research and finite element analysis that have been completed by our research group.The main researches are as follows:(1)Based on the results of the experimental study of the concrete-filled multicellular steel tubes shear walls with GFRP tubes embedded in CFST columns,the effects of the addition of GFRP tubes and the layers of GFRP tubes’ fiber on the damage modes,hysteretic capacity and load carrying capacity of were analyzed.Combining with the results of the finite element analysis study,the influences of concrete strength,steel strength,steel thickness,axial force ratio and depth-span ratio on the load carrying capacity and deformation capacity of the new composite shear walls were analyzed.(2)Based on the failure modes and test results,the strain distributions of composite shear walls in load-bearing capacity ultimate state were analyzed.Using the assumption of plane section and the equivalent stress method of confined concrete,the force and equivalent moment of concrete between steel tube and GFRP tube(SG concrete)and FRP-confined concrete in the boundary column of the compression zone are derived,and the calculation formula of the horizontal ultimate bearing capacity under large eccentric loading of the concrete-filled multicellular steel tubes shear walls with GFRP tubes embedded in CFST columns is established.The calculated values under different parameters are compared and analyzed with the horizontal ultimate bearing capacity obtained from the test results and finite element simulation to verify the accuracy and applicability of the ultimate bearing capacity calculation formula.(3)Combining with MATLAB,the numerical model of the concrete-filled multicellular steel tubes shear walls with GFRP tubes embedded in CFST columns in compression-bending condition was established by fiber model method.The numerical models were verified through experiments,and based on numerical models,the effects of concrete strength,steel strength,steel thickness,height-to-width ratio and the thickness of GFRP tube on the compression-bending performance of the composite shear walls were analyzed.(4)By regression analysis of the results of the numerical model,the calculation formulae of axial compression capacity,pure bending capacity and correlation curve dividing point between large eccentric loading and small eccentric loading of the concrete-filled multicellular steel tubes shear walls with GFRP tubes embedded in CFST columns were established.Finally,the simplified calculation formula of compression-bending bearing capacity of the concrete-filled multicellular steel tubes shear wall with GFRP tubes embedded in CFST columns was established.And the calculation formula is compared with the numerical results and the experimental results of composite shear walls in the literatures with good accuracy.