Experimental Investigation And Numerical Simulation On Concrete-filled Stainless Steel Tubular (CFSST) Columns Subjected To Blast Loading

Combining the advantages of concrete-filled steel tube（CFST）and stainless steel,concrete-filled stainless steel tube（CFSST）has the advantages of high bearing capacity,good ductility,corrosion resistance,beautiful appearance,etc.It has a wide range of application prospects in engineering structures.Structures of CFSST may be subjected to blast loading from accidental explosion accidents,terrorist explosion attacks and military strikes during their entire life-cycle,Therefore,it has important theoretical significance and engineering value to do research on the anti-blast performance of CFSST structures or members.In this paper,the dynamic mechanical properties of stainless steel S30408 and S31608,which are commonly used in civil engineering structures,have been studied.The anti-blast performance of CFSST columns of S30408 stainless steel has been studied by experimental investigation and numerical simulation.The main work and conclusions are as follows:（1）The rapid tensile tests of S30408 and S31608 austenitic stainless steels were carried out.Combined with the results at the previous stage of the project,the strain rate effect of strength and plasticity of two austenitic stainless steels were analyzed and compared.The parameters of the Cowper-Symonds and Johnson-Cook constitutive model were obtained by curve fitting,and the results can be applied to similar stainless steel materials.（2）The anti-blast tests of 8 CFSST columns were carried out.The parameters of section form（circular and square）and the proportional distance(0.172～0.569 m/kg^1/3)were mainly discussed,and the failure modes,residual deformation,surface overpressure and acceleration time history of the columns were obtained.Deformation mode of CFSST columns under blast loading were analyzed.The results show that as the proportional distance decreases,the degree of damage of the CFSST columns changes from no obvious damage to bending damage or even fracture.The deformation modes and surface overpressure of the two cross-sectional shapes are different,and the circular cross-section column has better anti-blast performance.The anti-blast performance of CFSST columns can be improved by concrete filling and local damage of stainless steel tube can be avoid effectively.（3）Based on the ANSYS/LS-DYNA software,the finite element model of the dynamic response of CFSST columns under blast loading was established and verified by experiment data.Based on the verified finite element model,the surface overpressure distribution and dynamic response of circular and square CFSST columns were analyzed.The results show that the form of section has influence on the surface overpressure of the column.On the front face of explosion,the surface overpressure in the axial direction of both columns shows"W"distribution,but the surface overpressure of the square section is greater than that of the circular section.On the back face of explosion,the overpressure of the square section is smaller than that of the circular section,and the negative pressure is larger;The surface overpressure of square section column in the axial direction is approximately uniformly distributed,while the circular section shows"W"shaped.The section form has little influence on the whole response mode of the column,but it has great influence on the local failure mode of the column.In the elastic-plastic response,the whole response mode of both circular and square sections of CFSST columns shows bending failure,but the mid-span local steel tubes show"D"-shaped failure and"Gold Ingot"-shaped failure,respectively.