Experimental Research On Seismic Behavior Of Mid-story Joints In Specially-shaped Column Frame Reinforced By Steel

Since the special-shaped columns structure appears, many countries’ scholars generallythink that the weak part of special-shaped column frame structure is the frame joints and bottomcolumn root, therefore, do a lot of experimental studies and theoretical analysis. This paper putsforward a structure measure, which is that steels would be put in the middle layer exterior jointcore, to improve the seismic performance of special-shaped column frame exterior joint, and dothe experiment of steel reinforced exterior joint seismic performance.Four special-shaped column exterior joint are designed in the experiment. All thespecimens can be divided into two groups. One group with two side joint, where the joints wererespectively put T steel and steel channel in the joint core area as the main object of the testresearch. Another group contains two exterior joint, one of the exterior joints with thepolypropylene fiber in in the joint core area, another joint without using fiber reinforced andsteel reinforced as contrast to use. Through the low cyclic loading test, each joint of the bearingcapacity, displacement ductility, restoring force characteristics, including hysteretic curve andskeleton curve, stiffness degradation and energy dissipation capacity and the longitudinal barand stirrup change rules would be analysed. Contrast the seismic indexes of steel reinforcedexterior joint, fiber reinforced exterior joint, and the common exterior joint. There were someconclusions: Using steel reinforced and polypropylene reinforced can improve the shear of crackdevelopment form, improve the joint cracking load and deformation ability, delay the joint’s laterstiffness degradation, and reduce the stirrup strain, especially in the deformation ability, reducethe stirrup stress strain and delay the joint later stiffness degradation, the advantage of steelreinforced joint were more apparent.Steel reinforced can improve r bearing capacity of the shear of joint core area, which isreflected in two aspects: One is the steel’s constraint effect to core concrete, which indirectlyimprove the shear capacity of the joint; The second is web members, which take direct shear.Contrast common joint, steel reinforced joint increased the shear capacity by over40%.Finally, on three different levels of material, components and structure, the seismic damagemodel is introduced. The cumulative damage mode based on energy dissipation and P-Δhysteretic characteristics was Chosen to calculate the exterior joints cumulative damage index and contrast: Steel reinforced can effectively reduce the specimen later cumulative damagedegree, and polypropylene reinforced effect is not obvious...