Abstract:

First,based on the calculation framework of the fiber beam element model,a stochastic numericalmethod to analyze the compressive capacity of thin- wall circular steel tubular columns filled with demolished con-crete blocks(DCBs) and fresh concrete(FC) is proposed by introducing the technique of generating random DCBsparticles and subsequently packing them randomly in the cross- sections at integration points of a fiber beam ele-ment.Then,a computer program is accordingly developed,and the validity of the proposed method is initially veri-fied by comparing the numerical results with the published test ones.The comparison shows that the non- uniformdistribution of DCBs in column cross- sections has no significant effect on the initial stiffness of the columns,but hasa certain effect,which increases with the decrease of steel wall thickness,on the compressive softening behavior.Finally,with the help of the proposed method,the compressive capacity of the columns affected by such parametersas the length- to- diameter ratio,the steel wall thickness,the replacement ratio of DCBs and the strength differencebetween the new and the old concrete in the steel tube,is investigated.The results indicate that,when the replace-ment ratio of DCBs varies from 25% to 40% or the strength difference between the new and the old concrete is notlarger than 15 MPa,the influence of the non- uniform distribution of DCBs on the compressive capacity of thecolumns is similar,while the influence increases with the decrease of the steel wall thickness or the length- to- diam-eter ratio at small eccentricity as well as with the decrease of the eccentricity.

Key words: circular steel tube, demolished concrete, fiber beam element, bearing capacity, stochastic analysis, numerical simulation