Modeling of crashworthy foam mounted braced unreinforced brick masonry wall and prediction of anti-blast performance

Abstract

Explosions are continually occurring in many parts of the world endangering human lives and seriously affecting the health of infrastructures and facilities. Low-rise buildings having a height of fewer than 13 m are load-bearing structures generally made of unreinforced masonry (URM), particularly in semi-urban areas, villages, and war-prone border areas. Many structures of importance including buildings constructed in the pre- and post-independence era of courts, monuments, etc., are masonry load-bearing structures. URM is also used as non–load-bearing partition walls and compound/boundary walls. Such walls are susceptible to out-of-plane blast loading. Under such loadings, these walls fail to survive and thus either get severely damaged or collapsed, jeopardizing the stability of the entire structure. Resistance of masonry walls against blast loading is vital for the safety of the building and its users as injuries sustained and casualties are generally not caused due to explosion, but by the brittle dynamic fracture and fragments of masonry walls, window glass panes shattering, and other secondary objects propelled as missiles by the blasts. In general, buildings are not designed for blast loading. For the safety of the building users, it is imperative that the walls must withstand such short-duration high-magnitude extreme loadings without not only undergoing catastrophic collapse but also not producing deadly fragments which could cause grievous injuries to the users. To protect URM walls from high-intensity blast waves, an out-of-box wall protecting technique using foams of polymer (e.g., polyurethane) and metals namely; aluminum and titanium, is considered on the face of the wall exposed to the blast pressure. This study describes a numerical technique implemented in ABAQUS/Explicit software to predict the overall anti-blast performance of URM wall strengthened externally with the above three different crashworthy foams. For this purpose, a braced URM wall made of clay bricks, with two transverse bracing walls one at each end on the same side, tested experimentally by Badshah et al. in the year 2021 under the chemical explosive loads of 4.34 kg and 7.39 kg-TNT, respectively, at scaled distances 2.19 m/kg1/3 and 1.83 m/kg1/3 is considered as the reference model and is validated against the test observations. Explosion load is modeled with ABAQUS built-in ConWep simulation program to simulate the wall-explosion wave interactions in the free field. Material nonlinearities of the brickwork have been attributed to bricks, joint-mortar, and brick-mortar interfaces through constitutive laws considering strain-rate effects. The foams are modeled using ABAQUS’s inbuilt Crushable Foam Plasticity Hardening model considering foam hardening and rate-dependent schemes. Results show that the higher Young’s modulus and inelastic stiffness of the foams contribute to dissipating more explosion energy and improve the resistance of the walls from savage explosions.

Widely Employed Constitutive Material Models in Abaqus FEA Software Suite for Simulations of Structures and Their Materials: A Brief Review

“…MAT_CDP makes use of tabulated EOS to define the connection between p and 𝜇. A comprehensive and detailed explanation of MAT_CDP is also given in recent publications by the authors [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. CDP parameters details can also be found in [1].…”

“…Open-cell foams are generally employed for fluid-based applications while closed-cell ones are used for load-bearing applications [68]. Manufacturing companies utilize metallic foams in various military vehicles to protect them from landmine blasts [34]. CFPH available in Abaqus for modeling crushable or crashworthy foams is regulated by the Von Mises shear stress (q) and hydrostatic pressure (p) [64,69].…”

Accidental Explosions, Beirut ANFO Blast, Ghana Truck Explosion, Global Terrorism Index 2021-22, and Blast Mitigation: A Review

“…Typically, the extent of harm inflicted upon a building or its various elements as a result of an explosion can range from fixable damages to complete and utter destruction, leading to severe injuries such as traumatic amputation, penetrating trauma, blast lung, angina, intra-abdominal hemorrhage, globe rupture, and even fatalities. The existing structural design codes do not take into account intense strain loadings like blasts or impacts, nor do they provide guidelines to prevent their likelihood during construction or the lifespan of the structure [16][17][18][19][20][21][22][23][24][25]. Blast loading involves the application of intense pressure over a brief period, typically ranging from microseconds to milliseconds.…”