Torsional Response of Reinforced Concrete Frame Buildings Subjected to Blast Loading

This study is intended to contribute to the understanding of the torsional behaviour of buildings subjected to blast loading. The scope of the investigation involves a 10-storey symmetrical reinforced concrete frame structure designed in accordance with CSA Standard A23.3 (2004), and the provisions of the National Building Code of Canada (2005). The building was analyzed under different magnitudes of explosions, triggered at different distances and location such that the building would be subjected to lateral impulsive forces causing torsion. Elastic dynamic time-history analyses were conducted using software ETABS under impulsive forcing functions caused by the detonations of 100 kg, 200 kg, 300 kg, 500 kg, and 1000 kg TNT at distances of 5 m, 10 m, and 20 m from the building, at three different eccentricities within the plane of building floor to create torsional eccentricities relative to the centre of rigidity. The performance of structure was evaluated by considering interstorey drift, floor rotations, lateral displacements, and P-M capacity/demand ratios for columns. The results indicate that the perimeter columns, especially the corner columns are affected most when the building is subjected to blast loadings. The torsional building response increases with the amount of TNT. It is related to the location of the explosion relative to the building, and increases with torsional eccentricity. On the other hand, the torsional response decreases with distance from explosion to building. Maximum interstorey drifts are closely related to the eccentricity of blast loads. This effect can be neglected in practical applications for small size charges and distant explosions. For example, an explosion caused by less than 500 kg TNT at distances of 20 m and longer would produce very small interstorey drifts and the effects of the eccentricity of blast loads could be neglected in such buildings.