Effect of Variable Concrete Strength on the Behavior of Buckling Restrained Braced Frames under Blast Load

BRBF (buckling restrained braced frame) is a relatively new lateral force resisting system for building structures.BRBFs are used mostly to resist seismic force due to their high ductility after yielding and the ability to absorb higher strain energy.ASCE (American Society of Civil Engineers) first permits the use of BRBFs as a single seismic force-resisting system by quantifying the seismic parameters such as response modification coefficient (R), over-strength factor (o) and deflection amplification factor (Cd) for a structure built with BRBF, in their 2010 code (ASCE 7-10).But it has not been investigated how a structure built with BRBF, which is primarily designed to resist seismic force, and behaves under sudden occurrence of a blast load.This research investigates the performance of a BRBF subjected to blast loading.In other words, this paper focuses on the effect of blast loading on BRBF.The architype for this investigation is a chevron type braced frame.The frame is subjected to a short duration blast load that lasts only 21.7 mili-second (ms).Blast loading effects on the braced frame are assessed by identifying the weakest plane of failure, deformation characteristics and out of plane bending.The research investigates how the properties of the surrounding concrete, especially compressive strength, affect the overall strength of the BRBF on resisting blast loading.It is observed that the compressive strength of the surrounding concrete plays a significant role in reducing the deformation characteristics, both in-plane and out-of-plane.