Finite Element Analysis(FEA) On Seismic Behavior Of Concrete-filled Double-skin Round-ended Stainless-steel Bridge Piers

Concrete-filled round-end double-skin stainless steel tube（CFSST-D）bridge piers combine the advantages of the outstanding corrosion resistance of the outer stainless-steel tube and the composite action in concrete-filled steel tube（CFST）system.However,detailed investigations on these types of structures are currently very limited and seismic performance analyses of double-skin CFSST-D bridge piers are scanty.Therefore,this thesis aimed at numerically simulating the seismic behavior of concrete-filled double-skin round-ended outer stainless-steel and inner steel tube bridge piers subjected to cyclic lateral loading.Experimental specimens of the concrete-filled round-end double-skin stainless-steel tube bridge piers were selected from literature.Finite element analysis（FEA）was established using ABAQUS 6.13 and the model was verified by comparing the finite element analysis results with the test results.FEA duplicated the experimental conditions retrieved from the literature.Based on the validated finite element model,parametric analysis was conducted to consider a wide range of geometric and material properties.The varying parameters under the investigation include:the outer stainless-steel tube yield strength,and diameter to thickness ratio;and the inner steel tube yield strength,and diameter-thickness ratio.In addition to these parameters,effect of the axial compression ratio（n）and hollow ratio were also considered.The main findings and conclusions drawn from the current investigation include:1)the horizontal bearing capacity for the nominal yield strength of steel pipe with 300MPa,345MPa,and 420MPa increased by 13.60%,25.50%and 43.40%,respectively compared with 235MPa.However,for the same condition,yield strength of internal steel tube recorded only 1.20%,1.60%and 4.60%increase;2)with an increase in Do/to the by varying four Do/to ratios of 30.00,36.36,57.14 and 80.00,and with the corresponding thickness values of outer steel tube to 26mm,22mm,14mm and 10mm,thickness of external stainless-steel tubes become thinner and vulnerable to local buckling;and 3)when the hollow ratio is 0.00,0.50 and 0.75,the horizontal bearing capacity increases by 8.90%and 6.90%,this is because of the increase in the area of inner steel pipe and the distance from neutral axis.The horizontal bearing capacity of the CFSST-D bridge piers dramatically enhanced with increasing yield strength(f_yo)and decreasing diameter to thickness ratio（D_o/t_o）of outer stainless-steel tube and axial compression ratio（n）has obvious influence on the horizontal bearing capacity and ultimate displacement of the specimen.However,the effect of increasing yield strength(f_yi),and decreasing diameter-thickness ratio of inner carbon steel tube（D_i/t_i）displayed little influence on the horizontal bearing capacity of the specimens.Finally,a hysteretic model was proposed to predict the P-Δ relationship of double-skin round-ended CFSST bridge piers under the cyclic...