Weak political systems and poor governance in certain developing countries are found to have a war-like environment where structures are being targeted by blasts and bombs. Industrial blasts due to frail know-how and mishandlings are also quite common. Recent accidental explosions like that occurred at the Beirut Port, Lebanon (August 2020); ammunition depot in the outskirt of the Ryazan City of Russia (November 2020) are of concern for the safety of adjacent building infrastructure and their users. Such intense loading events cause damage to certain elements of a structure which may result in disproportionate or progressive collapse. It necessitates a clear understanding of the phenomenon of the blast and extreme loads induced out of it, and response of the target structure under such loadings. In this study, the state of research on air-blast and ground shockwave parameters, shallow underground blasting, and on the ground and buried shallow blast-resistant shelters are presented. The phenomenon of the self-Mach-reflection of the explosion, loading parameters and empirical blast models available in the open literature followed by the damage criteria for the buildings subjected to the underground blasting and available peak particle velocity (PPV) prediction models have been discussed. To make the application of advanced materials such as fibrous concrete, ultra-high performance concrete, FRP composites, etc., it is important to comprehend the existing blast/shock-resistant shelters and their response under such loading. The shelters are primarily designed by incorporating features of the materials like high degree of deformability/ductility, use of the shock-isolation panels and the mechanism for controlling crack formations. Finally, conclusions and recommendations for future studies are summarised. This paper presents prospects to engineers, town planners, researchers, policymakers and members of the core drafting sectional committees to understand the phenomenon of the blast and extreme loads induced out of it.

In general, the blast-induced ground shock excites the foundation of the structure prior to the air-blast pressure because of the obvious reasons of difference in wave propagation velocities. However, the ground shock and air-blast pressure might act simultaneously on the structure for some standoff distance with a particular quantity of the explosive charge and cause severe damage than by air-blast pressure. Therefore, the ground shock and air-blast pressure both should be considered for estimating the structural response by such a near-field detonation. The objective of the present study is to assess the performance of the masonry heritage building under air-blast pressure without and with ground shock generated from on the ground spherical-shaped TNT explosive charge at varying standoff distances. The considered building is a heritage brick masonry structure in lime-surkhi mortar. The time lag between the ground shock and air-blast pressure for different scaled distances is evaluated. Stresses have been computed and are compared with the provisions of the Indian and Australian Standard Codes of Practice for Structural Use of Unreinforced Masonry. Also, the damage assessment has been carried out using the concrete-damaged plasticity (CDP) model available in the ABAQUS finite element program.

A finite element model is developed in ABAQUS/CAE to simulate the behavior of one-way reinforced concrete slabs under air-blast loading. Several published empirical equations have been utilized to model air-blast pressure, P(t), for different combinations of the explosive charges and standoff distances. The values of the peak overpressure have been taken from the field explosion tests conducted on four normal reinforced concrete (NRC) slabs of size 2000 mm x 1000 mm x 100 mm in the School of Civil, Environmental, and Mining Engineering, The University of Adelaide, Australia (2009). The slabs were doubly reinforced with HYSD steel re-bars of diameter 12 mm spaced at 100 mm c/c in the major bending plane (ρ = 1.34%) and 200 mm c/c in the other plane (ρ = 0.74%), where “c/c” is the center-to-center distance between two adjacent re-bars. A plasticity-based damage model for concrete and an explicit solver in ABAQUS/CAE are adopted in the finite element (FE) simulation. The available test results and finite element analysis predictions, including maximum mid-span displacement and damage to the RC slabs, are presented and weighed. The computed results are found in good agreement with the experimental ones. The validated model is used to examine the performance of RC slabs with 25% replacement of the conventional steel re-bars by the FRP re-bars of equivalent strength on the compression face only, remote face only, and both faces of the slab. The replacement has been done for higher strength and ductility. Substituted FRP re-bars are of (1) Aramid fiber-reinforced polymer (AFRP), (2) Basalt fiber-reinforced polymer (BFRP), (3) Carbon fiber-reinforced polymer (CFRP), and (4) Glass fiber-reinforced polymer (GFRP). The results are also compared with those obtained with a 50% replacement of the steel re-bars by the FRP re-bars.

Structural members with low-flexural stiffness, such as slabs, are more susceptible to impulsive loadings induced by falling machines/tools during construction and installation, and also from rolling boulders/rocks triggered by wind/earthquake, especially in mountainous areas. The impact resistance of reinforced concrete (RC) slabs supported on two opposite edges (often called the one-way slab) and on all four edges (i.e., two-way slab) has been adequately studied experimentally as well as computationally, and is available in the literature. However, the slabs supported on three edges have not been studied under low-velocity impact for their impact response. For this purpose, a computational study is performed through finite elements by implementing ABAQUS software on the validated model, resulting in the slab, which is supported on (i) three edges and (ii) two opposite edges, to be subjected to low-velocity impact, induced by dropping a 105 kg non-deformable steel mass from a height of 2500 mm onto the slab centroid. Furthermore, the role of the material strength of the concrete of the slab is investigated via replacing the ultra-high performance concrete (UHPC) for standard or normal-strength concrete (NSC). The impact load is modeled by considering the explicit module of the software. Failure mechanism, stress/strain contour, displacement distribution, and crack pattern of the slabs are compared and discussed.