Effect of Blast Load in Nonlinear Dynamic Response of the Buckling Restrained Braces Core

Having profound knowledge about the behavior of systems subjected to the external loads such as earthquake, wind, explosion and etc. can assist us to design more resisting structures. Braces are one of the most common lateral resisting systems and their major weakness in compression is buckling which result in a reduction to their loading capacity. Buckling restrained braces (BRB) are one of the strategies to deal with this problem.  In this paper, using ABAQUS, the nonlinear dynamic response of the buckling restrained brace subjected to the blast loads with different positive phase durations is studied. Results show that the positive phase duration has no effect on the pattern of stress diagram while by increasing the positive phase duration, the maximum value of the compressive stress of the BRB is increased and the maximum value of the tensile stress is decreased. According to the results, when the blast loads are applied, for all positive phase durations, the total displacement is almost the same while the value of the plastic displacement is more for the blast load with larger positive phase duration. However, if the blast load is considered to be as an impact load, the value of the plastic displacement is less than the other types of loading.  For these kinds of loading, more time is spent to reach a persistent plastic displacement. For such impact load and at the beginning of the loading, the total displacement falls sharply. This period of time is less for velocity and acceleration time history diagrams and does not depend on the positive phase duration. In addition, for the blast load with larger positive phase duration, the value of absorbed energy is more in the compression zone.