Safe Scaled Distance for Masonry Infilled RC Frame Structures Subjected to Airblast Loads

Abstract

Terrorist bombing and accidental explosion may generate extreme loading conditions on nearby structures, resulting in damage and even collapse of structures. The degree of damage to a structure depends on the capacity of the detonation and its location as well as structural conditions. Some guidelines are available to assess the safety of unstrengthened buildings to airblast loads. These guidelines are usually given in terms of the safe scaled distance between explosion center and structure, whereas the structure conditions, which also affect its performance, are not explicitly defined. The safe scaled distance is obtained primarily from field blasting tests and experiences of structure damage to blast loads. These guidelines can be used for a quick safety assessment of structures, but do not provide clear damage scenarios of the structures. In a previous paper, damages of low-rise masonry infilled reinforced concrete (RC) structures to surface explosion of different scaled distances are numerically simulated. It was found that RC frame would collapse when the scaled distance was less than 1.82 m/kg 1/3 ; and the front masonry wall would suffer excessive damage when the scaled distance was less than about 4.5 m/kg 1/3 . The present paper is an extension of the latter work. It employs a more detailed RC model with distinctive definitions of concrete and reinforcement material performance. More thorough analyses are carried out to find the correlation between the scaled distance and the damage level of low-rise and medium-rise masonry infilled RC frames. The different failure mechanisms between the low-rise and medium-rise structures to blast loads are also observed and discussed. The computer program LS-DYNA3D with user defined RC and homogenized masonry material models is used in numerical calculations. The numerical results are also compared with the safe scaled distance recommended in the United Stated Department of Defense's regulations, ASCE guidelines, and those derived in the previous paper.