Experimental Study On A New Type Of Joint Between CFRT Column And Steel Beam

As one of new composite structures in the field of Civil Engineering, concrete-filled rectangular steel tubular (CFRT) structure has high capacity, large energy absorption capacity, and high ductility, also it has regular shape which is easy to connect between columns and beams, convenient fire-control measure, and short construction time. Therefore CFRT structure will become popular in medium-high rise residential construction. At present time, however, critical factors for which extensive applications of CFRT structure will be influenced is joint detail scheme. Thus investigation on joints between CFRT columns and steel beams in medium-high rise residential construction has significant theoretical and applied value ,so has research on reasonable and effectivejoint detail scheme.According to analysis on existing joints, this paper presents a new joint with angle-stiffener. Based on experimental research and theoretical analysis, investigations on the new type of joint are made systematically, the main contents and results include the following items.1 Four specimens of new joints between CFRT columns and steel beams are designed. By low-cyclic reversed load test, skeleton curves of new joints and shearing deformation in joint core area are studied, the influence of parameters, such as concrete cores, length of stiffener, and relative dimensions of column and beam, is discussed. Experimental results show that the new CFRT-column to steel-beam joints proposed in this paper possess good earthquake resistant capacity. The infilled concrete benefit to restrain the buckling deformation of column webs, increase the strength and stiffness of the joint. The lengthened stiffener can transfer much more beam moment, make the strength of the joint increased.2 Based on experimental results and finite elements analysis of new joint, the stress transfer mechanism of the new joint is analyzed. There are two stress transfer patterns about the new joint, one is for rectangular steel tubular column joint, its stress transfer pattern is that beam moment is transferred to column webs mainly by stiffeners, the other is for CRFT column joint, its stress transfer pattern is that part of beam moment is transferred from stiffeners to column webs, another part of beam moment is transferred to infilled concrete by column flange. Based on stress transfer mechanism of joint, calculation methods about bending strength and shearing strength are presented, and calculated bending strength agreed with the measured one.3 According to analysis on the reason for failure of joints, improved measures for new joints are presented, the following phases are included, improved butt welding design, improved technology and welding sequence for butt welding seam, intensive strength checking for butt welding seam, intensive quality inspection for butt welding seam. By borrowing ideas from relative codes, design propositions for new joint are presented.