Experimental study on co-working of inner and outer steel part in concrete-filled steel tube tower frame with inner stiffening parts under tension

To study co-working of inner and outer steel parts in concrete-filled steel tube with inner stiffening parts under non-full-section tension, two kinds of scaled test models of the main component structures with internal reinforcement and internal section steel were designed respectively. Load-strain curve and the stress ratio of inner steel part to outer steel part were analyzed. The results indicate that the inner and outer steel parts can work together under non-full-tension and the stress ratio between them is 1. The numerical analysis by finite element software ABAQUS was presented, and its results were in good agreement with test results.The results of FE model shows that the internal and external steel component's strain development rules are basically consistent. When the truss reaches the ultimate bearing capacity under lateral load, the internal steel components and the external steel tube also meet the yield stress respectively, which means that the internal and external steel components can work together.