Contribution of higher modes in the dynamic response of reinforced concrete member subjected to blast

Abstract

Response of reinforced concrete structures subjected to blast load of high intensity and short duration is difficult to analyze. P-I (pressure-impulse) curves are one of the approaches for describing structural response against blast load. Design codes also suggest preparing P-I curves based on SDOF for obtaining structural response subjected to blast. Blast load excites higher modes of vibrations. The SDOF analysis does not cover the higher modes effect.The structural dynamic response of RC flexure members under a varying range of explosion scenarios was predicted by carrying out investigations. The linear elastic beam with variable boundary conditions was analyzed using the Modal superposition method based upon Euler-Bernoulli, Rayleigh, Shear, and Timoshenko theories. For various ranges of the blast, Iso-damage (P-I) curves, including the effect of higher modes, were generated, and the types of failure were established. These iso-damage curves differ significantly from those obtained using the SDOF concept for the case of blast in the dynamic and impulsive regime. In the case of near blast, understandably higher modes (both flexure and shear) play a significant role. The present study suggests that the Timoshenko formulation yields an accurate response irrespective of the Flexibility of the structure.