Response of 45 storey high rise RCC building under blast load

Abstract

In the recent past, trend has been shifted towards construction of tall and slender buildings to mitigate the scarcity of land in the busy areas. In today’s scenario threat of enemies and terrorist attack is increasing. A bomb explosion within or immediately nearby a building can cause catastrophic failure of the building, loss of life and injuries to occupants (Dharaneepathy et al. in Comput Struct 54:587-595, 1995 [1]). Therefore consideration of blast load in analysis and design of important structures is essential. The study explores three-dimensional nonlinear dynamic responses of typical tall building under blast loading. The 45 storey symmetric reinforced concrete building is designed for dead, live and wind loads. The influence of the variable blast source distance (30, 40, 50 m) and variable blast source height (8th, 23rd, 38th storey at 30 m ground zero distance) on the lateral load response in terms of peak deflections, accelerations, inter-storey drift and hinge formations were investigated. Performance level of building as per FEMA 273 was also checked for each individual case. Structural response predictions were performed with a commercially available three-dimensional finite element analysis programme using non-linear direct integration time history analyses. Results for buildings with variable blast source distance were compared. Similar study is performed for variable blast source height. A detailed study on the response of blast excited building is presented for 500 kg of TNT placed on ground and in the air. The work mainly focuses on the dynamic response and performance level of building under different cases of blast. The calculation of Blast load on building for all cases is carried out by using IS 4991 (1968) criteria for blast resistant design of structures for explosions above ground. The results revealed that for a tall building, effect of blast decreases as standoff distance increases and there is consequent decrease in the non-linear dynamic response. It has been observed that performance level of building is critical for minimum standoff distance. In case of variable blast source height, explosion created at 23rd floor and 30 m ground zero distance is critical because building will be subjected to more blast force above and below the blast level. It has been observed that the dynamic response is random and not maximum at top storey.