Experimental Study On The Performance Of Multi-cell Cfst Mega-columns And Mega-frame

According to a super high-rise mega-frame structure, the compressive behavior of themulti-cell CFST mega-column and the seismic behavior of the mega-frame with multi-cellCFST columns have been researched. The main contributions are listed as follows:1. Six1/12scaled multi-cell CFST mega-column models were tested under verticalmonotone repeated loading. The specimens were invided into two parts, one part had steelreinforcement cage inside, and the other part had no steel reinforcement cage inside thecolumn. The concrete strength grade was C30or C40. Three of the models were testedunder axial compression, two were tested under large eccentric compression, and one wastested under small eccentric compression. The load-bearing capacity, stiffness and itsdegeneration, ductility and failure characteristic of models have been compared andanalyzed. The discipline of force to deformance was achieved, and the force mechanismwas revealed.2. The test on one1/25scaled mega-frame with mega-columns was carried out underhorizontal low cyclic loading. The load-bearing capacity, stiffness and its degeneration, andfailure characteristics of the specimen have been analyzed based on the above experiment.3. A simplified calculation formula for load-bearing capacity of multi-cell CFSTmega-column was established. Nonlinear finite element analysis on the mega-frame withmulti-cell CFST columns was carried out, the damage and yield failure process wasrevealed as well. The results obtained from the calculation and those from experiment are ingood agreement.The research results show that:1. Due to the composite constraint effect of each multiple cavity steel tube, thecompressive strength and stiffness of the multi-cell CFST mega-column is improved. It canbe applied in the structural design of super high-rise mega-columns.2. The compressive strength and stiffness of the inside concrete is improved a lot bysetting the steel reinforcement cage inside the multi-cell CFST mega-column.3. The braces in mega-frame-brace structure with multi-cell CFST columns work asthe first seismic defense line and they can improve the load bearing capacity and stiffness ofthe structure. Preventing braces from instability is very important in the seismic design.