06.07: Comparison of Blast Performance of Steel Modular Buildings with Anchored and Sliding Foundations

Abstract

ABSTRACTA two‐module blast‐resistant steel building with overall dimensions of 12 m by 6 m floor plan and 3.4 m height was designed to resisted 80 kPa free field overpressure with 140 microsecond duration. The building was designed to remain within “high damage/response” level when it is anchored to its foundation. The effect of anchored and unanchored or sliding (free‐to‐slide) foundation on blast performance of structural elements on the wall and roof, foundation loads, building sliding, and building total friction and kinetic energy were investigated using nonlinear dynamic finite element analysis tools. The comparison of analyses results revealed that building foundation reactions and maximum deflection demands for structural members can significantly decrease with unanchored foundation. For unanchored foundation, several friction coefficients (i.e., 0.2, 0.5, and 0.8) for the interaction between the building and its foundation were considered. The analyses results show that the maximum relative deflections of the structural members of the building with unanchored foundation to be between 43% and 120% with an average of 80% of that for the building with anchored foundations. The most significant effect of unanchored foundation on blast performance of the building was the significant decrease in the foundation maximum horizontal reaction, which was approximately 15% to 60% of that for the building with anchored foundation. However, the unanchored foundation had negligible effect on building vertical foundation reactions. The computed maximum sliding displacements were approximately 10 m, 2 m and 0.3 m for the building with unanchored foundation for friction coefficient of 0.2, 0.5, and 0.8, respectively. For the building with unanchored and anchored foundations, both friction energy and kinetic energy versus time plots were very similar for initial stages of the blast loading. The overall results show that providing even limited permissible sliding between blast resistant structures and their foundation can significantly reduce their foundation reactions and improve blast performance of structural members. A controlled‐sliding mechanism between blast resistant structures and their foundation with steel cables is recommend to improve blast performance of the structure while limiting maximum sliding within desired permissible limits.