Investigation of band-beam slabs subjected to close-in blast loading - Experimental and numerical study

Abstract

Band-beam slab" or "slab with a shallow beam" are widely used in contemporary multi-level building construction and are particularly common in lower levels and basements. These slabs are favoured for conserving space and reducing floor-to-floor heights. Consequently, under standing how band-beam slabs perform when exposed to close-range detonations is essential for critical infrastructure projects and has not been previously studied in the literature. With recent terrorism events where portable explosives ranging from 2 kg to 10 kg are more common, a close in detonation can significantly affect the structural integrity of civil infrastructure. Thus, this study aims to examine the behaviour of band-beam slabs when subjected to close-in detonations. The paper presents both experimental results and validated Arbitrary Lagrange-Euler (ALE) nu merical framework to study and assess the damage of the slabs under various loading conditions and slab designs. A total of six band-bean panels are subjected to close-in detonations of Composition-4 (C4) charges. Initially, validation of the numerical modelling is performed where damage in terms of spall crater sizing and crack patterns are observed. It was shown that the numerical modelling technique could predict crater sizes within 15 % of the area, and crack propagation, including patterns, was appropriately captured. Through numerical modelling parametrisations, it was shown that confinement detailing, such as the use of C-hooks, close spacing of shear reinforcement, and additional reinforcement in the beam-to-slab transition zone can drastically improve the performance of the panel in terms of spalling damage and deflections. Finally, it was shown that the spalling, global and local deformation can be minimised with appropriate detailing. Design recommendations for additional reinforcement to control and mitigate spalling, cracking and scabbing were proposed.