Effect of Vertical Setbacks of Space Frame Structure under Seismic and Blast Loads using Applied Element Method

Abstract

Structures, when subjected to nonlinear dynamic loading, drastically affect the structure’s physical properties. The structural failure occurred at the critical points of weakness during the earthquake. These structural weaknesses observed in irregular structures are mainly due to the improper distribution of mass, geometry and stiffness. Architects usually prefer irregular buildings for the aesthetics point of view. These irregular structures are more vulnerable to dynamic loading. On the other hand, the devastating failure due to bomb blast is also the concern for the study as many vital structures collapsed because of the terrorist attack. Such failures need to be checked by studying the performance of building under the earthquake and blast loading. The objectives of this paper are to compare the peak responses at each storey level of mass irregular space frame structure to the dynamic effect. Firstly, Time History of the Northridge earthquake spectra with Peak Ground Acceleration (P.G.A.) =8.660 m/s2 = 0.883g at 9.82 seconds considered and analysed. Secondly, blast material [1] composed of two different charge weights [2] 1000 kg TNT and 2500 kg TNT at a distance of 10m was considered. For responses to the structure, the most advanced numerical tool viz., Applied Element Method (AEM) has been used. It is concluded that the amplitude of Northridge earthquake’s maximum x-displacement at the terrace level is closer to maximum x-displacement for the blast load of 2500kg TNT but the time of occurrence was changed abruptly, i.e., Northridge earthquake maximum displacement occurs at the duration of nearly 10 sec, but the maximum displacement of blast load of 2500kg TNT is occurring almost at 0.2 sec, i.e., 50 times quicker in occurrence.