Tests on Mechanical Properties of Concrete-Filled Double-Skin Circular Steel Tubes Connected by Thread Under Axial Compression
A connection method of lengthening the steel tube of concrete-filled double-skin circular steel tube by inner lining tube and threaded connection has been proposed.Taking the length,depth and posi-tion of the thread as the basic parameters,12 concrete-filled double-skin circular steel tube connected by thread through inner lining tube were designed,and the axial compression tests were carried out.By com-paring specimens connected by thread with the ordinary specimens and welded specimens,the axial com-pressive loading-longitudinal compressive displacement curves,axial compressive loading-strain of steel tube curves and failure mode of the specimens were analyzed,and the effects of different parameters on the axial compressive bearing capacity and stiffness of the specimens were studied.The results showed that the axial compressive loading-longitudinal compressive displacement curves of the specimen could be divided into linear elastic stage,elasto-plastic stage,yield-strengthening stage and descending stage within the range of parameters studied.The bearing capacity and stiffness of the specimens connected by thread through inner lining tube were no worse than those of the ordinary specimen or the welded specimens.The bearing capacity and stiffness of the specimens increased with the increase of thread length,and bearing ca-pacity and stiffness of the specimens connected at end section by thread through inner lining tube were high-er than those of the specimens connected at middle section by thread through inner lining tube.The calcula-tion method of the axial compressive bearing capacity of concrete-filled double-skin circular steel tube con-nected by thread through inner lining tube were suggested.
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