Numerical study of progressive failure mechanism in steel frames with CFST columns

Progressive failure is developed by expanding a local initial failure from one element to another, which ultimately leads to the collapse of the whole structure or a large part of it. This phenomenon causes local damage in structural elements which can result in massive losses and significant damage. Ductility, continuity, and degree of structural expansion are among the parameters that play an important role in reducing such consequences. In this study, the behaviour of a scaled four-span steel frame, with concrete filled steel tubular columns (CFST), was evaluated under progressive failure by removing the middle column. This work was done using the finite element method in ABAQUS. This work was carried out by examining the effect of reinforced triangular plate, haunch and angle steel reinforcements, reduced section in flange and web as well as post-tensioned FRP cables along with sensitivity analysis. The findings indicated that among the proposed anti-collapse methods, the maximum yield strength, the maximum ultimate strength and ductility ratio belong to angle steel reinforcement with 140.24 KN, reinforced triangular plate with 259.6 KN and RBS with 21.16 method. However, in a comprehensive comparison, the method of adding reinforced triangular plate was the best anti-collapse method since it avoids damage to the columns. Additionally, the change in compressive and tensile strength of the concrete did not have much effect on the frame behaviour in the progressive failure. Moreover, the frame with non-concrete columns has a ductility ratio 3 times higher than SRCT case, although the frame with SRCT columns has a 14 percent higher yield strength.