Experimental Study of Hollow Concrete-Filled Circular Steel Tubular Beam Column Connected by Thread through Inside Lining Tube

A type of hollow concrete-filled circular steel tube connected by thread through inside lining tube is proposed. Twelve hollow concrete-filled circular steel tubular beam columns connected by thread through inside lining tube are designed and fabricated using the length of the thread along the axial direction, the working height of the thread, and the position of the thread as parameters. In addition, one nonconnected specimen and two welded specimens also are designed and fabricated to conduct controlled experimental research. The experimental phenomena and specimen failure modes, axial compressive load-longitudinal compression curve, axial compressive load-lateral deflection curve at the mid-section, and axial compressive load-strain in the steel tube curve, as well as the bearing capacity, strength reserve, deflection curve shape, lateral stiffness, ductility, and plane section assumptions, are analyzed. The research results indicate that, within the parameter range studied, the experimental phenomenon of specimens connected by thread is basically consistent with that of contrast specimens and the thread connection through inside lining tube is reliable before tripping. The axial compressive load-longitudinal compression curve and axial compressive load–mid-section lateral deflection curve of all specimens can be approximately divided into elastic stage, elasto-plastic stage, and descending stage. The peak load of all specimens is relatively close, and although specimens have undergone almost the same stress process, the strength reserve of specimens connected by thread is insufficient. The shape of the deflection curve of all specimens is close to the sine half wave curve before the load drops to about 70% peak load, and the lateral stiffness and ductility of all specimens also are relatively close. During the entire loading process, the distribution of longitudinal strain in the steel tube at the mid-section along the height of section basically conforms to the plane section assumption. Finally, the calculation method for the hollow concrete-filled circular steel tubular beam column connected by thread through inside lining tube is suggested. Based on the behavior of the hollow concrete-filled circular steel tubular beam column and considering the comprehensive cost, the hollow concrete-filled circular steel tube connected by thread through the inside lining tube has certain research and application value.