Study On The Tension Behaviors Of Stiffened Concrete Filled Steel Tubular Members In Tower Structures

The stiffened concrete-filled steel tube is made up of concrete filled with inner rebar,steel tube,section steel and other stiffening parts.It has high bearing capacity,good ductility and high rigidity.So far,the stiffened concrete-filled steel tube has been extensively studied in axial compression,bending and fire resistance,but it has not been studied systematically for its tensile properties and the common working performance of steel structures inside and outside.In this paper,concrete filled steel tube with internal rebar and internal section steel is studied as the object,and its tensile performance,load transfer mechanism and common working performance of internal and external steel structure in the tower structure are discussed.The details are as follows:The tensile properties of the inner and outer steel structures of the main structural members in the crossing tower under lateral load are studied based on the scale test.Taking the Sutong Yangtze River crossing transmission tower as the engineering background,two kinds of scale test models of the main component stuctures with internal reinforcement and internal section steel are designed respectively.The loading is carried out by the column top,and the tensile and common working performance of the steel structure inside and outside when the load coming from the web is transmitted between the inner and outer steel structure are studied.The experimental results show that the internal and external steel structures of the two main structural members can work well together,and the inner and outer connection methods are effective.The stress ratio of inner and outer steel structure is approximately equal to one.Study on bond-slip behavior of concrete-filled steel tubes interface by adhesion test of internal and external concrete-filled steel tubes is carried.The bond strength and the average bond stress-slip curve of concrete filled steel tube under tension and compression are obtained by drawing and pushing test of inner and outer concrete-filled steel tubes respectively.Based on the characteristics of the experimental bond-slip curves,a traction-separation bond-slip constitutive model based on surface contact is proposed.The constitutive model is applied to the finite element software ABAQUS and the internal and external bond tests are compared,which provides the necessary preparation for the finite element numerical simulation of the tower.The numerical simulation of concrete filled steel tube trusses with internal reinforcement and internal section steel was carried out.Based on the steel truss of concrete-filled steel tube with internal reinforcement and internal section steel,the load transfer mechanism between internal and external steel structure without inner and outer connection measures is simulated by using finite element software ABAQUS,and the transfer mechanism shows that the load transfers between inside and outside steel structure from top to bottom,from outside to inside.And the analysis of the tensile properties of internal and external steel structure with or without the internal and external connection measures shows that internal and external connections can make the internal steel structure with full force effectively.Finally,based on the load transfer mechanism proposed in this paper,the theoretical calculation method of the non-full-section tensile capacity of the stiffened concrete-filled steel tube in the tower structure is given.