EFFECT OF BLAST LOADING ON FRAMED STRUCTURES FOUNDED ON PILES

Abstract

Explosion accidents at chemical plants in the last century have claimed many lives and resulted in extensive damage to facilities and equipments. The ri 1• associated with these operations can be quite high owing not only to the probability of an accident but also to the devastating consequences. Terrorist bomb attacks in the Stock Exchange Building, Mumbai, World Trade Centre, New York, Murrah Federal Building, Oklahoma city and many such cases have highlighted the need for studying the blast effects on civilian and industrial structures other than military installations. Reinforced concrete framed structure having pile foundation with specified ductility has been taken for study. Stiffness of frame is computed by conventional method of plane frame analysis. Stiffness of pile group is computed taking account of soil-pile interaction. The system is analyzed as two degree of freedom system -one degree to represent foundation system and second degree the framed structure. Total mass of the system is lumped at the nodes. Blast loads are of very high magnitude and less frequent and transient in nature hence elasto-plastic analysis with tolerable damages has been adopted for economy. The system is first analyzed for two idealized conditions (1) considering the foundation to'be rigid, (2) considering the framed structure to be rigid. Then non-linear analysis of two-degree freedom system is carried out. Effects of various parameters studied are (a) stiffness of system, (b) resisting force of the frame, (c) foundation resistance and (d) structural damping. Lastly, a comparison of bi-linear and tri-linear resistance function for the response of the structure is presented.