Parametric Investigation of Three Adjacent Multi-Degree-of-Freedom Systems Under Surface Blast Action

The main purpose of the present study is to investigate the various parameters and three adjacent MDOF system under surface blast action like gap distance, blast distance, gap element multiplies and position of buildings for surface blast direction. Very few studies are reported under surface blast action under pounding of three adjacent MDOF systems. So here the attempt is done to address this issue.

In the present study, three nearby real three dimensional structure is considered, these are converted into a lumped mass model as per the rules of structural dynamics. These structures are considered for fix base and SSI base conditions. SSI calculations are done as per FEMA Guidelines. However the surface blast load calculations are done as per the paper from Goel et al. (2012). In the entire time domain analysis only the left structure experiences the surface blast load. However, the effect will also propagate in middle and right structure due to insufficient gap distance under pounding actions.

There are four cases to present the results. Case I (Gap element multiplies) in this case the gap element multiplier 4 for AE/L have produce the good results. Case II (Gap distance) shows that up to 0.01 m gap distance the results of pounding forces and displacements are severe. Case III (Blast distance) shows that up to 30 m blast distance have produce severe pounding response in all three adjacent MDOF systems. Case IV (Building positions for surface blast directions) shows that the combinations of buildings (flexible-moderate stiff-stiff building) have experiences maximum floor displacements.

From the results of parametric investigations, it is noted that gap element stiffness multiplier close to 4 produces severe pounding forces. The soil structure interaction amplifies the displacement in the structure but reduces the base shear values in the structure compared to fix based systems. Flexible building-Moderate stiff building-Stiff building placed at the location of left-middle-right positions has produces maximum top floor displacement response during surface blast loading. On the other hand, the building placed in combination as moderate-stiffer-flexible at left-middle-right positions has induced less base shear values than other building positions combinations.