Air-Blast Response of Axially Loaded Clay Brick Masonry Walls with and Without Reinforced Concrete Core

Shariq

International Journal of Protective Structures

et al. 2023

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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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Shariq

International Journal of Protective Structures

et al. 2023

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“…The need for realizing the dynamic behaviors of RC structures/components under extreme and impulsive loads with short durations such as blast and impact, has been increased with rising subversive blasts on civil structures and infrastructures in recent years (Anas et al, 2022g, 2022h; Anas and Alam, 2022g; Shariq et al, 2022; Tahzeeb et al, 2022a, 2022b; Ul Ain et al, 2022b). Many studies can be found in the literature investigating the blast performance of RC slabs, beams, piers, and bridge superstructures (Alsendi and Eamon, 2020; Anas et al, 2021; Anas and Alam, 2021; Qu et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Performance of (1) concrete-filled double-skin steel tube with and without core concrete, and (2) concrete-filled steel tubular axially loaded composite columns under close-in blast

International Journal of Protective Structures

Umair

2022

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Composite structural members such as concrete-filled double-skin steel tube (CFDSST) and concrete-filled double steel tubular (CFDST) columns are increasingly being utilized in modern structures owing to their capability to integrate the beneficial properties of constituent materials to carry heavy loads as compared to conventional reinforced concrete columns. Axial compression performance of such composite columns has been extensively investigated and available in the open literature. However, their response under impulsive loadings such as those induced by explosions is not very well studied because not many investigations have been conducted on these columns. Performance of composite compression members under short-duration/high-magnitude blast loading is of considerable interest under the prevailing environment of hi-tech wars, subversive activities, and accidental explosions. The recent devastating accidental Ammonium Nitrate explosion at Beirut port (Lebanon), and the ongoing invasion of Ukraine by Russia raise the concern of researchers and engineers for the safety of structural elements/components. In this study, a 3-D finite element model of axially loaded 2500 mm long CFDSST column of ultra-high-strength concrete (170 MPa) is developed in ABAQUS/Explicit-v.6.15 computer code equipped with Concrete Damage Plasticity (CDP) model, and investigation has been carried out for its blast performance under the 50kg-TNT explosive load at a standoff distance of 1.50 m in free-air. The effects of strain rate on the compressive strength of the concrete are considered as per fib Model Code 2010 (R2010) and UFC-3-340-02 (2008). The non-linear behavior of the steel is also taken into account. Damages in the form of (1) a - concrete crushing on the explosion side of the column and b - concrete cracking on the tension side and their spread over the column length, and (2) yielding of tubes are observed. Computational results are validated with the available experimental observations. To improve the column response, the analysis has been extended to investigate the blast performance of axially loaded CFDSST columns with and without core concrete having an inner steel tube of circular/square cross-section and their response have been compared with the equivalent single skin concrete-filled steel tubular circular/square columns of same axial load capacity.

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Response of Two-Way RCC Slab with Unconventionally Placed Reinforcements Under Contact Blast Loading

Ain

2022

Structural Integrity