Abstract:In order to improve the behavior of double-tube buckling restrained braces (BRBs), it is proposed to set contact rings between inner tube and outer tube of the brace. As a result, they can provide lateral constraint for the inner tube; this is the improved buckling restrained braces (IBRBs). In this paper, a program was edited by the language of MATLAB based on theoretical model formulation of IBRBs and applied to the calculation of overall stability strength capacity. Finite element models of IBRBs were carried out and both load displacement curves and strength capacity were obtained. Tests on IBRBs were also conducted. The results of numerical simulation agreed with the ones of the program and tests. It indicated that the program was reasonable so it could provide a basis for the analysis of overall stability strength capacity of these kinds of IBRBs.

The H-shaped steel PEC columns with concrete poured between flanges are different from the traditional steel-encased concrete columns. In this paper, the behaviors of H-shaped steel PEC columns with different parameters under axial loading and cycling loading have been simulated by using commercial software ANSYS. The results show: The fracture of the columns under axial loading and cycling loading mainly lies in the crush of concrete at the bottom of the columns. Because of the confined effect of steel, the stress distribution of specimens under axial loading display a V-shape. With the increment of the width of flanges, the confined effect becomes more obvious. Compared with H section steel columns, the bearing capacity has been increased. With the increment of axial compression ratio, the capacity has declined. The behaviors of the ductility and the energy dissipation capacity of H section steel PEC columns are good and dropped with the increment of axial compression ratio. At the initial stage, the average stiffness degenerates slowly. However, at the later stage, the average stiffness degenerates rapidly. Moreover, the degeneration becomes faster with the increment of compression ratio. The elastic stage, elastic-plastic stage and plastic stage are included in the skeleton curves. This study on the H-shaped steel PEC columns has important practical implications to the engineering.