| The carbon fiber-reinforced polymer(CFRP)-confined concrete-filled stainless steel tubular(CFRP-CFSST)column has the superiority in outstanding mechanical properties,corrosion resistance,and low maintenance cost needed throughout its life cycle,and therefore it has a wide application prospect.In order to study the axial compression behavior of CFRP-CFSST stub column,a total of 12 specimens were tested.It is found that the typical failure mode of CFRP-CFSST specimen is the sudden fracture of CFRP material and the typical load-compression curve can be divided into four stages:elastic stage,secondary ascending stage,repeated fracture stage and post-fracture stage.Compared with CFSST stub column,CFRP material can significantly improve the axial compression performance of CFSST stub column,and greatly improve the ultimate bearing capacity and energy absorption capacity of specimens.The strain hardening effect of stainless steel tube is more obvious under the restriction of CFRP.The experimental results show that when the wall thickness of stainless steel tube ts is constant,the ultimate bearing capacity of CFRP-CFSST stub column increases linearly with the increase of the number of CFRP confinement layers.When the number of CFRP confinement layers is the same and the constraint effect coefficient of stainless steel ξs increases,the increase in capacity of CFRP-CFSST shows a downward trend.According to the positive linear relationship between the ratio of ξcf/ξs and the ultimate bearing capacity improvement index ηcap of CFRP-CFSST,a simplified theory of ultimate bearing capacity of CFRP-CFSST is proposed.Based on the experimental study,a finite element model of CFRP-CFSST stub column is established,and the accuracy of the model is verified by comparing the ultimate load,longitudinal-circumferential strain curve and typical failure mode of the model with the experimental results.Based on the finite element model,the axial compression performance of CFRP-CFSST is further explored and analyzed.The relationship between the stress response of various materials and the typical load-compression curve of CFRP-CFSST short column under axial compression is analyzed;The factors that affect the contact stress of the core concrete and the distribution of the axial stress on the core concrete;On this basis,the axial compression performance of CFRP-CFSST is analyzed by extended parameter analysis.It is found that the elastic modulus and hardening index of stainless steel have no effect on the axial compression performance of CFRP-CFSST.Increasing the nominal yield strength of stainless steel can improve the elastic stiffness and bearing capacity of specimens,but has little effect on the ductility of specimens;Increasing the compressive strength of concrete has a negative impact on the ductility of specimens;However,increasing the tensile strength of CFRP material can comprehensively improve the axial compression performance of CFRP-CFSST;The contribution of CFRP to the bearing capacity improvement of CFRP-CFSST will be weakened when the diameter to thickness ratio of specimens decreases.Considering the strain hardening effect of stainless steel in the loading process,the continuous strength method(CSM)was used to calculate the strength enhancement of stainless steel caused by the strain hardening effect.Based on the limit equilibrium method,a new formula for calculating the ultimate bearing capacity of CFRP-CFSST short columns was deduced.The accuracy of the ultimate bearing capacity predicting formula was verified by the experimental data,finite element results and relevant literature data.The mean value and standard deviation of Nu,pre/Nu,the ratio of the predicted bearing capacity to the actual bearing capacity,are 0.9748 and 0.0683 respectively. |
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