Mechanical behavior of special-shaped CFT stub column under axial compression
Based on the existing triaxial plastic damage constitutive model of concrete and the elastic-plastic constitutive model of steel,a three-dimensional solid fine finite element model of L-shaped,T-shaped and cross shaped CFT stub columns was established.On the basis of existing experimental verification,parameter analysis was conducted to compare the effects of steel tube strength,concrete strength,height to thickness ratio of web and wall thickness of steel tube on the load-displacement curves.The results showed that when the yield strength or wall thickness of the steel tube increased,the ultimate bearing capacity of the column significantly increased,and the ductility was better.When the strength grade of concrete or the height to thickness ratio of the web increased,the ultimate bearing capacity of the column increased,but the ductility decreased.The confined areas and unconfined areas and the corresponding mean values of concrete Mises stress were determined when 3 kinds of stub columns reached the ultimate bearing capacity,and the practical calculation formula of ultimate bearing capacity considering the confinement coefficient was proposed.This constraint coefficient was mainly related to the height to thickness ratio of the web.The comparison of the ultimate bearing capacity calculated by this formula with the experimental values and FE values,proved the accuracy and effectiveness of the formula,which could be used for the bearing capacity calculation of 3 types of special-shaped CFT stub columns under axial compression.
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