The influence of initial stress on the behavior of concrete filled steel tubular dumbbell shaped long columns

An experiment for studying concrete filled steel tubular(CFST) dumbbell-shaped long columns by axial load with initial stress is carried out.Based on the testing,finite element analyses on CFST dumbbell-shaped columns are performed considering slenderness ratio,eccentric ratio and initial stress degree as parameters.Influence of mechanical behaviors and calculation of ultimate load-carrying capacity on CFST dumbbell-shaped columns by initial stress are analyzed.The results indicate that the mechanical behavior of CFST dumbbell shaped columns is similar with that of CFST single tube ones,initial stress makes elastic-plastic phase appear ahead and decreases the tangent rigid and elastic ultimate load.However,the initial stress has almost no influence on the ultimate load-carrying capacity for the member of a little slenderness ratio.Initial stress will decrease stable ultimate capacity while the slenderness ratio is great.Finally,the method for calculateing the load carrying capacity of CFST dumbbell-shaped columns with initial stress is presented.The theoretical value agrees well with experimental results,it can be used in practical engineering.