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International Journal of Protective Structures
Journal Prestige (SJR): 0.841
Citation Impact (citeScore): 1
Number of Followers: 4  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2041-4196 - ISSN (Online) 2041-420X
Published by Sage Publications Homepage  [1174 journals]
  • Guest Editorial

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      Authors: Wensu Chen, Thong M Pham, Jingde Li
      Pages: 143 - 143
      Abstract: International Journal of Protective Structures, Volume 13, Issue 2, Page 143-143, June 2022.

      Citation: International Journal of Protective Structures
      PubDate: 2022-05-30T05:28:26Z
      DOI: 10.1177/20414196221097045
      Issue No: Vol. 13, No. 2 (2022)
       
  • Assessing the stab resistive performance of material extruded body armour
           specimens

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      Authors: Umur Ibrahim Cicek, Darren John Southee, Andrew Allan Johnson
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This paper investigates the effect of material extruded body armour specimen size on stab penetration depth and back-face signature (BFS) and establishes the minimum thickness required for a series of material extrusion materials to provide protection against the UK Home Office Scientific Development Branch (HOSDB) body armour KR1-E1 requirements. In stage one, material extruded planar test specimens ranging from 40 × 40 mm to 80 × 80 mm in length and width with 10 mm increments at three different thicknesses, 6, 8 and 10 mm, were stab tested under 24 joules of impact energy using a gravity driven drop test apparatus. In stage two, 50 × 50 mm specimens in six material categories, PC, ABS, PLA, TPLA, PA and TPU, were manufactured at different thicknesses via material extrusion and impacted in accordance with the UK HOSDB KR1-E1 stab impact energy level as they were the optimum size when considering overall stab and BFS performance. The study established the fundamental steps towards the use of material extrusion in future personal protection solutions. Results demonstrated that stab penetration and BFS were dependent on specimen size, thickness and material type, and there was an inverse relationship between stab penetration depth and BFS. Also, a minimum thickness of 5 mm for PC and TPLA, 6 mm for ABS, 7 mm for PLA, 11 mm for PA and 12 mm for TPU, with 100% print density, was required in order to provide protection against the HOSDB KR1-E1 level of 24 J stab impact energy.
      Citation: International Journal of Protective Structures
      PubDate: 2022-06-29T04:50:05Z
      DOI: 10.1177/20414196221112148
       
  • Blast resistance of timber structural elements: A state-of-the-art review

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      Authors: Rodrigo Mourão, Andreia Caçoilo, Filipe Teixeira-Dias, Arturo Montalva, Hollice Stone, Eric Jacques
      Abstract: International Journal of Protective Structures, Ahead of Print.
      The response of structures subject to impulsive loads remains a field of intense research. Whilst traditional construction materials, such as steel and concrete/masonry, have been the focus of most studies, further research on the performance of alternative materials for blast-resistant applications has been driven by their growing use in sustainable construction. Over the last years, engineers have been re-evaluating the use of timber as a prime construction material for a range of building types, from small office to high-rise residential buildings. As a result, there is now a growing need to study the blast resistance of timber structures, as they may become potential targets of terrorist attacks or being placed in the blast-radius of other critical buildings. A review of existing research on the blast resistance of timber structures is presented and key factors on the blast analysis and design of such structures are discussed. Most of the research has been conducted on light-frame wood stud walls, glued- and cross-laminated timber, and addresses material properties under high strain rates, typical failure modes, behaviour of structural connections and retrofitting solutions. Failure modes are reported to be highly dependent on the element layout and manufacturing aspects, and dynamic increase factors for the modulus of elasticity and maximum strength in the ranges of [1.05, 1.43] and [1.14, 1.60], respectively, have been proposed for different timber elements. Mechanical connectors play a significant role in dissipating energy through plastic deformation, as the brittle nature of timber elements compromises the development of their full capacity. Regardless the element type, SDOF models can accurately predict the dynamic response as long as idealised boundary conditions can be considered. Overall, although a good amount of research is available, more extensive research is needed to guide the design and engineering practice and contribute to the development of design codes and testing standards for timber structures under blast loading.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-30T08:11:14Z
      DOI: 10.1177/20414196221092466
       
  • Crashworthiness investigation of draw bead in aluminum tubes under axial
           loading condition

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      Authors: Hamid Nikkhah, Nida Naveed, Roghaiyeh Assaedi Beiragh, Sina Dadashzadeh, Quang-Tri Truong
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This study aims to investigate the effects of the draw beads on the crashworthiness of the aluminum tubes under axial quasi-static loading. Based on this design philosophy, a total of 12 beading tube designs with various configurations were developed. Within each design, the effect of arrangement bead form on the crashworthiness performance was also analyzed. A finite element model, validated using experimental tests, was used to study the crashworthiness performance and progressive deformation of the tubes. Based on the results, a multi-criteria decision-making method known as Technique of Order Preference by Similarity to Ideal Solution was employed to determine the most suitable tube that features high energy absorption and low impact force. The best tube with a high score was selected to investigate the effect of bead formed direction on aluminum tubes. Consequently, the study identified a bead shape tubes configuration that exhibits superior crashworthiness and low impact force. The beading tube design methodology presented in this study allows the exploitation of variable shapes geometries for the development of high-efficiency energy-absorbing structures and their crushing behaviors.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-27T12:32:28Z
      DOI: 10.1177/20414196221090989
       
  • More on the penetration of spherical-nosed rigid projectiles into metallic
           targets

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      Authors: Yaniv Vayig, Zvi Rosenberg, David Ornai
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This work deals with several issues related to the deep penetration of spherically nosed rigid projectiles impacting metallic targets at normal incidence. The most important issues in these processes are the constant resisting stress acting on the projectile beyond the initial entrance phase, the extent of the entrance phase, and the onset of cavitation at impact velocities higher than a certain threshold velocity. In this work, we derive a new relation for the target’s resisting stress in terms of its bulk and shear moduli and we also use a simplified analysis to account for the effect of the entrance phase on the depth of penetration for spherically nosed rigid projectiles. In addition, we highlight the role of cavitation in this process through numerical simulations for targets having very different densities.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-26T12:58:30Z
      DOI: 10.1177/20414196221092475
       
  • An experimental and simulated investigation into the validity of
           unrestricted blast wave scaling models when applied to transonic flow in
           complex tunnel environments

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      Authors: Emily M Johnson, Nick Grahl, Martin J Langenderfer, David P Doucet, Joseph Schott, Kelly Williams, Barbara Rutter, Catherine Johnson
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Since the inception of high explosives as an industrial tool, significant efforts have been made to understand the flow of energy from an explosive into its surroundings to maximize work produced while minimizing damaging effects. Many tools have been developed over the past century, such as the Hopkinson–Cranz (H-C) Scaling Formula, to define blast wave behavior in open air. Despite these efforts, the complexity of wave dynamics has rendered blast wave prediction difficult under confinement, where the wave interacts with reflective surfaces producing complex time-pressure waveforms. This paper implements two methods to better understand blast overpressure propagation in a confined tunnel environment and establish whether scaled tests can be performed comparatively to costly full-scale experiments. Time–pressure waveforms were predicted using both a 1:10 scaled model and three-dimensional air blast simulations conducted in Ansys Autodyn. A comparison of the reduced scale model simulation with a full-scale blast simulation resulted in self-similar overpressure waveforms when employing the H-C scaling model. Experimental overpressure waveforms showed a high level of correlation between the reduced scale model and simulations. Additionally, peak overpressure, duration, and impulse values were found to match within tolerances that are highly promising for applying this methodology in future applications. Using this validated relationship, the simulated model and reduced scale tests were used to predict an overpressure waveform in a full-scale underground mine opening to within 2.12%, 2.91%, and 7.84% for peak overpressure, time of arrival, and impulse, respectively. This paper demonstrates the effectiveness of scaled, blast models when predicting blast wave parameters in a confined environment.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-25T12:52:20Z
      DOI: 10.1177/20414196221095252
       
  • Flexural and impact behavior of textile reinforced concrete panel

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      Authors: Md. Jahidul Islam, Tasnia Ahmed, Sheikh Muhammad Fahad Bin Imam, Muhammad Ifaz, Hamidul Islam
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Steel is susceptible to corrosion and requires a significant concrete cover, which increases self-weight and cost. Therefore, an alternative to traditional reinforcements is needed. Textile reinforced concrete (TRC) is a favorable composite using textile material as reinforcement with a fine-grained concrete matrix. This study represents a comparison between different TRCs having different textile reinforcements subjected to flexural bending and impact loading. Four types of textiles—glass (GT), a square oriented galvanized iron (SGIT), diagonal pattern galvanized iron (DGIT), and carbon (CT) are used. All four types of textiles are used to prepare 400 x 50 x12 mm textile reinforced mortar (TRM) and tested for tensile strength properties. This study tests TRC panel and plate samples by three-point bending and drop-weight impact methods. The uniaxial tensile strength test of the textiles shows that CTs can take around 2.3 times higher tensile load than SGITs. However, their tensile load capacity is almost similar in the case of TRM, where SGIT textile shows about 30% higher extension. The flexural bending test of the TRC panels shows that the load-carrying ability increases nearly two times with the increase of 25 mm in thickness even when the number of reinforcement layers remains the same. With the increase in thickness, SGIT textile shows better performance. Drop-weight impact test of the TRC plates shows that the impact energy absorption in CT textile plates is up to two times higher than SGIT plates for various thicknesses. This study summarizes that CT shows overall better performance than SGIT.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-25T12:51:20Z
      DOI: 10.1177/20414196221095250
       
  • Deformation and failure of thin domed-scored metallic disc under impulsive
           loading

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      Authors: Gopinath Kanakadandi, Vijayabaskar Narayanamurthy, Y V Daseswara Rao
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This paper presents the structural deformation and failure of a thin domed-scored metallic disc (SMD) applied at the bottom of a pressurized rocket silo which needs to withstand a storage pressure and undergo instantaneous rupture under an impulsive pressure. Initially, the large deformation and rupture of a flat-thin SMD subjected to a pressure impulse is numerically studied and validated with experimental results. Subsequently, the behavior of a domed-thin SMD is investigated for the aforementioned loadings in the rocket silo. The influence of loading rates [math], score depth and width-to-disc thickness ratio (t1/t and b/t), diameter-to-disc thickness ratio (D/t), dome height-to-disc diameter ratio (H/D), score length-to-disc radius ratio (l/R), score pattern, and score geometry on the deformation and failure response of the domed-thin SMD is investigated. The studies demonstrate that (1) the failure initiation point shifts from 1/4th radius to the disc center for loading rates> 10 MPa/s; (2) under impulse loading, the responses are (i) sensitive to the loading rates up to 100 MPa/s, (ii) sensitive to score’s depth, only up to half the disc thickness and insensitive to score’s width, (iii) unaffected for number of scores N> 6, (iv) stabilized for l/R> 0.4, and (vii) almost the same for semi-circular, rectangular and triangular score geometries; (3) the failure do not initiate and propagate along all scores for N> 10 in the disc; and (4) behavior of the domed SMD approaches to that of a spherical dome for H/D> 0.3.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-25T12:51:04Z
      DOI: 10.1177/20414196221095249
       
  • Application of transfer learning for the prediction of blast impulse

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      Authors: Jordan J Pannell, Sam E Rigby, George Panoutsos
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Transfer learning offers the potential to increase the utility of obtained data and improve predictive model performance in a new domain, particularly useful in an environment where data is expensive to obtain such as in a blast engineering context. A successful application in this respect will improve existing surrogate modelling approaches to allow for holistic and efficient strategies to protect people and structures subjected to the effects of an explosion. This paper presents a novel application of transfer learning for the prediction of peak specific impulse where we demonstrate that previous knowledge learned when modelling spherical charges can be transferred to provide a performance benefit when modelling cylindrical charges. To evaluate the influence of transfer learning, two artificial neural network architectures were stress tested for three levels of random data removal: the first model (NN) did not implement transfer learning whilst the second model (TNN) did by including a bolt-on network to a previously published NN model trained on the spherical dataset. It is shown the TNN consistently outperforms the NN, with this out-performance increasing as the proportion of data removed increases and showing statistically significant results for the low and high threshold with less variability in all cases. This paper indicates transfer learning applications can be used successfully with considerable benefit with respect to surrogate modelling in a blast engineering context.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-24T08:59:40Z
      DOI: 10.1177/20414196221096699
       
  • 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

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      Authors: S.M. Anas, Mehtab Alam, Mohammad Umair
      Abstract: International Journal of Protective Structures, Ahead of Print.
      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.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-24T06:04:49Z
      DOI: 10.1177/20414196221104143
       
  • Review on quick safety assessment of building structures in complex urban
           environment after extreme explosion events

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      Authors: Yanchao Shi, Shaozeng Liu, Zhongxian Li, Yang Ding
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Extreme explosion events result in demands for emergency rescue service. From the civil engineering perspective, a quick safety assessment of building structures in the explosion’s vicinity will provide the emergency rescue committee with concrete support to make scientific decisions. In this paper, three primary issues, namely, inverse analysis of explosive characteristics, blast wave propagation in complex urban areas and blast-induced damage identification, are reviewed. These are often performed stepwise and form a multi-step whole to assist the emergency rescue service. The paper begins by introducing the inverse analysis of explosives based on craters, building damages and seismic or acoustic records. In this step, explosive characteristics, for example, charge type, original time, yield and location, could be produced and input into blast load calculation in the next step. Then, the existing literature on blast wave propagation and blast load determination is presented with close attention to complex urban environments. It shows that the current study remains in its infancy and relies on advancement in computational fluid dynamics (CFD). Besides, pressure–impulse (P-I) diagrams which predict the structural damage based on the calculated blast loads are illustrated. Onsite damage detection techniques, such as visual inspection, non-destructive testing (NDT) and vibration-based methods, are also discussed. The paper ends with a discussion of the shortcomings of previous work and the outlooks of further work.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-23T10:21:48Z
      DOI: 10.1177/20414196221104146
       
  • A branching algorithm to reduce computational time of batch models:
           Application for blast analyses

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      Authors: Adam A Dennis, Danny J Smyl, Chris G Stirling, Samuel E Rigby
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Numerical analysis is increasingly used for batch modelling runs, with each individual model possessing a unique combination of input parameters sampled from a range of potential values. Whilst such an approach can help to develop a comprehensive understanding of the inherent unpredictability and variability of explosive events, or populate training/validation data sets for machine learning approaches, the associated computational expense is relatively high. Furthermore, any given model may share a number of common solution steps with other models in the batch, and simulating all models from birth to termination may result in large amounts of repetition. This paper presents a new branching algorithm that ensures calculation steps are only computed once by identifying when the parameter fields of each model in the batch becomes unique. This enables informed data mapping to take place, leading to a reduction in the required computation time. The branching algorithm is explained using a conceptual walk-through for a batch of 9 models, featuring a blast load acting on a structural panel in 2D. By eliminating repeat steps, approximately 50% of the run time can be saved. This is followed by the development and use of the algorithm in 3D for a practical application involving 20 complex containment structure models. In this instance, a ∼20% reduction in computational costs is achieved.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-17T04:28:54Z
      DOI: 10.1177/20414196221085720
       
  • Evaluation of critical damage location of contact blast on conventionally
           reinforced one-way square concrete slab applying CEL-FEM blast modeling
           technique

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      Authors: S.M. Anas, Mohd Shariq, Mehtab Alam, Mohammad Umair
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Nowadays, accidental explosions in residential and factory buildings are common owing to poor maintenance and mishandling of fuel gas and chemical explosive appliances leading to grievous injuries and infrastructure damages. Contact blast on slabs using explosives is noticed as a simpler act of subversion as compared to other components of the building and is more damaging than a close-in blast. In general, damage caused by contact blast is localized in the form of concrete cratering, scabbing, and rupture of the reinforcement. A recently published state-of-the-art review on the performance of reinforced concrete (RC) slabs under contact and close-in explosion loading scenario by the authors (Anas et al., 2021b) reveals the common perception for the location of contact blast to cause maximum damage is the centroid of the slab. It develops a curiosity with sufficient interest to investigate the effect of the location of contact explosive charge on the damage response of the slab. Several numerical techniques such as empirical, ConWEP (semi-empirical), Smooth Particle Hydrodynamics (mesh-free method), and Coupled-Eulerian-Lagrangian (CEL) are in use for simulation of blast loading on structures. Current literature reveals that the CEL is the most advanced and realistic blast modeling technique. This study applies Coupled-Eulerian–Lagrangian (CEL) formulation with finite element method (FEM) using the dynamic computer code ABAQUS/Explicit-v.6.15 to investigate the performance of singly reinforced one-way spanning concrete slab subjected to concentric contact blast loading. The numerical model is validated with the experiment results in the open literature. The validated model is then employed to investigate whether or not the maximum damage is really caused by the central location of the contact blast. For this purpose, one-quarter of the slab with nine symmetrical points (or locations) of contact blast of explosive charge, which reflect the coverage of the entire slab, in contact with the top face of the slab is considered in the study. Two constitutive material models, Concrete Damage Plasticity and Johnson–Cook, with strain rate effects are used to simulate the non-linear behavior of the concrete and steel, respectively. The results reveal that the most critical location of maximum damage to the slab is along the line of symmetry parallel to the supports at an eccentricity of B/4 from the centroid of the slab, where “B” is the width of the one-way slab.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-11T11:01:57Z
      DOI: 10.1177/20414196221095251
       
  • Study on physical behaviors according to element formulations of ballistic
           impact simulation models

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      Authors: Tae Kwang Yoo
      Abstract: International Journal of Protective Structures, Ahead of Print.
      During modeling ballistic impact, physical behaviors were investigated according to element formulations. In order to conduct the investigation, a simple ballistic impact simulation model was used. Several case studies consisting of FEM (Finite Element Method) and SPH (Smoothed Particle Hydrodynamics) models were conducted using the LS-DYNA research/commercial code. As a result, these case studies suggest that the SPH formulation is effective to simulate interactions among particles after failures so that the penetration phenomenon of the projectile were well described. In addition, some parameters relating to the SPH formulation such as particle spacing and smoothing length constant were investigated. Finally, for the verification, 20 mm fragment simulating projectile tests to verify the protection performance of K9 Thunder grill louver were compared with the simulations applying the FEM and SPH formulations.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-03T05:57:23Z
      DOI: 10.1177/20414196221095883
       
  • A recovery mechanism for flap system of large aircraft with actuator
           failure

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      Authors: XC Zhou, P Xue, YB Luo, JG Lu, C Zhang
      Abstract: International Journal of Protective Structures, Ahead of Print.
      High-lift devices of transport aircraft reshape the wing in order to increase the lift of the aircraft during certain portions of flight. In order to increase its reliability, large transport aircrafts usually install the inter connection strut (ICS) as security devices. However, there are very limited publications on how to design the ICS, and how it works. There is a strong motivation for modeling and simulating the behavior of high-lift devices with ICS once failure happens and resulting design parameters. In this study, based on rigid-flexible coupling multi-body modeling technique, and dynamic response analysis of flap system under normal operation and failure state, a design method of ICS is proposed and the key parameters, that is, freely moving range and the mean crushing load of the energy absorber, are identified. The mitigation effect of ICS for actuator failure of flap system is clarified by analyzing the dynamic response of flap system with ICS. The results show that the ICS can reduce the peak driving torque of drive strut by 45.3%, and the unexpected rotation of the flap decreases by 66.2% after actuator failure happened.
      Citation: International Journal of Protective Structures
      PubDate: 2022-04-25T06:57:42Z
      DOI: 10.1177/20414196221087338
       
  • Dynamic response characteristics of adjacent tunnel lining under blasting
           impact in subway connecting passage

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      Authors: Linghao Xiong, Nan Jiang, Chuanbo Zhou, Haibo Li
      Abstract: International Journal of Protective Structures, Ahead of Print.
      The connecting passage between two adjacent tunnels is conducive to the rescue and evacuation of subway tunnels when disasters occur. The blasting method is usually used in the construction of connecting passage. The vibration caused by blasting construction may endanger the safety of subway tunnel structure. As a result, the influence of blasting pressure on the stability of subway tunnel lining structure during the excavation of connecting passage is studied, and the safe blasting construction distance is proposed, which is crucial to the safety of adjacent subway tunnel lining. This study takes the connecting passage of Wuhan Metro Line 8 as an example. Using Finite element software ANSYS/LS-DYNA, an accurate numerical calculation model of construction site is established. The nonlinear elastoplastic mechanical characteristics of soil, rock, and tunnel lining are simulated by Drucker Prager, Plastic Kinematic, and Johnson Holmquist Concrete constitutive material models, respectively. The credibility of the three-dimensional numerical calculation model and material constitutive model was proved by contrasting the field measured data of the connecting passage with the numerical calculated results. Analysis of numerical results, the axial and radial PPV, frequency, and Von Mises stress of subway tunnel lining are obtained. The influence of subway tunnel lining under adjacent blasting can be obtained by analyzing the distribution law of PPV and Von Mises stress. Non-static tensile strength is needed considering the high pressure and high strain rate process of concrete during blasting. By fitting the relationship between PPV and dynamic tensile stress, and referring to DIF parameters, the safety range of PPV in subway tunnel lining blasting is determined. The critical safety distance between blasting construction and tunnel lining is obtained by Sadovsky vibration velocity attenuation formula, which is used to guide the subsequent blasting excavation of continuous tunnels.
      Citation: International Journal of Protective Structures
      PubDate: 2022-04-22T11:27:43Z
      DOI: 10.1177/20414196221083687
       
  • Physics-informed regularisation procedure in neural networks: An
           application in blast protection engineering

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      Authors: Jordan J Pannell, Sam E Rigby, George Panoutsos
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Machine learning offers the potential to enable probabilistic-based approaches to engineering design and risk mitigation. Application of such approaches in the field of blast protection engineering would allow for holistic and efficient strategies to protect people and structures subjected to the effects of an explosion. To achieve this, fast-running engineering models that provide accurate predictions of blast loading are required. This paper presents a novel application of a physics-guided regularisation procedure that enhances the generalisation ability of a neural network (PGNN) by implementing monotonic loss constraints to the objective function due to specialist prior knowledge of the problem domain. The PGNN is developed for prediction of specific impulse loading distributions on a rigid target following close-in detonation of a spherical mass of high explosive. The results are compared to those from a traditional neural network (NN) architecture and stress-tested through various data holdout approaches to evaluate its generalisation ability. In total the results show five statistically significant performance premiums, with four of these being achieved by the PGNN. This indicates that the proposed methodology can be used to improve the accuracy and physical consistency of machine learning approaches for blast load prediction.
      Citation: International Journal of Protective Structures
      PubDate: 2022-04-13T09:44:06Z
      DOI: 10.1177/20414196211073501
       
  • Experimental investigation of 3D-printed auxetic core sandwich structures
           under quasi-static and dynamic compression and bending loads

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      Authors: İ.Kürşad Türkoğlu, Hasan Kasım, Murat Yazıcı
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Auxiliary metamaterials designed according to the Negative Poisson’s Ratio (NPR) property are exciting structures due to their high impact strength, impact energy absorption abilities, and different damage mechanisms. These good mechanical features are suitable for aviation, automotive, and protective construction applications. These structures, whose most significant disadvantages are production difficulties, have become easier to produce with the development of 3D production technology and have been the subject of many studies in recent years. In this presented study, two conventional core geometries and three different auxetic geometries, commonly used in sandwich structures, were designed and produced with 3D printer technology. The strength and energy absorption capabilities of prototype sandwich structures investigated experimentally under bending loads with static and dynamic compression. Except for the re-entrant (RE) type core, the auxetic core foam sandwich structures demonstrate higher rigidity and load-carrying capacity than classical sinusoidal corrugated (SC) core and honeycomb (HC) core sandwich structures under both quasi-static and impact-loaded compression and three-point bending experiments. Double arrowhead (DAH) and tetrachiral (TC) auxetic cores outperformed honeycomb core in terms of specific quasi-static and impact load-bearing performance under compression by 1.5 ± 0.25 times. In three-point bending experiments under both quasi-static and impact loading conditions, the load-carrying capacity of the double arrowhead and tetrachiral auxetic cores was found to be more than 1,86 ± 0.38 times that of the honeycomb core sandwich panels.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-27T10:01:08Z
      DOI: 10.1177/20414196221079366
       
  • Progressive damage in pretensioned and reinforced concrete plates against
           repeated impacts

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      Authors: Vimal Kumar, Mohd. Ashraf Iqbal, Achal Kumar Mittal
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This study is planned to explore the performance of pretensioned concrete (PC) plates under multiple impacts. A detailed investigation has been carried out on pretensioned concrete plates (0.8 × 0.8 m2) against drop impact. The plates prepared using Mix-40 and Mix-60 grade concrete have been induced with two different levels of initial prestress, that is, 1/10 and 1/5 (i.e. level-1 and level-2) times the strength of the concrete. The PC plates have been impacted by a falling impactor (2382 N) dropped from 0.5 m height. The response of those plates has been obtained and compared with the reference RC plates. The post-impact performance of the damaged plates has been further discovered by subsequently dropping the impactor multiple times from the identical height. The FE simulations of the problem have been carried out using Johnson-Holmquist-2 and metal-plasticity constitutive models for concrete and steel, respectively. The models have been initially verified with the experimental results available in literature, and subsequently the simulations for drop impact have been carried out. The simulation results are also compared with the results of drop impact experimentations performed. In general, both the pretensioned and reinforced concrete have witnessed flexural cracks at the beginning, such that pretensioned concrete witnessed lesser cracks compared to reinforced concrete. As the number of drops increased, one major splitting crack developed only in pretensioned concrete, whereas the reinforced concrete exhibited additional punching cracks. For a given concrete grade, the pretensioned concrete level-2 witnessed the smallest damage, minimal cracks, and also minimal spalling followed by the pretensioned concrete level-1 and reinforced concrete. The reinforced concrete absorbed the minimal impact energy followed by the pretensioned concrete level-1 and level-2 under the multiple impacts. The FE simulations predicted the impact force and reaction within 11.9 and 9.9% variation, respectively, with the corresponding experimental results.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-27T09:04:42Z
      DOI: 10.1177/20414196221078025
       
  • Modelling the response regimes of elastomer-coated concrete slabs
           subjected to blast pressure loading

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      Authors: Chanel Fallon, Graham J. McShane
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Elastomer coatings have been found to offer protection to structural components when subjected to dynamic load cases, such as impact and blast. One such application of interest is the protection of concrete structures. Elastomer coatings have the potential to provide a cost effective and practical protective solution. The dynamic response of quasi-brittle concrete structures to blast loading is complex, with a range of dynamic response regimes. It remains to be identified in which regimes of response an elastomer coating can offer a protective benefit. Numerical and analytical modelling of thin, one-way reinforced concrete slabs subjected to varying intensities of simulated blast loading is carried out, in order to ascertain the protective effect of an elastomeric coating. Three configurations are considered: uncoated, coated with elastomer on the blast-receiving face and coated with elastomer on the non-blast-receiving face. It is found that the slab is relatively insensitive to the elastomer coating during response regimes where concrete damage is minimal. At higher load intensities, where the slab exhibits severe damage, the numerical results indicate a substantial reduction in slab deflections may be achieved by coating on the non-blast-receiving face. At the highest loading intensities, a shift in failure mechanism is observed to one dominated by transverse shear at the supports. An analytical model quantitatively predicts a substantial coating benefit in protecting against this failure mechanism.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-27T04:21:48Z
      DOI: 10.1177/20414196221075821
       
  • Shock qualification of low-cost blast resistant wheels by in field tests

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      Authors: Silvestri Paolo, Naselli Giovanna Adele, Cepolina Emanuela Elisa, Zoppi Matteo
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This paper presents the results obtained during an experimental campaign on blast resistant wheels designed for a low-cost demining machine, derived from an agricultural tractor. Such wheels must fulfil two requirements: first, they have to be able to retain their mechanical integrity in case of blast and still work after one or more explosions, in order to be able to drive the machine out of the minefield without human intervention; second, they must reduce as much as possible the amount of energy transferred to the vehicle, to protect the on-board equipment from the effect of the detonation of a landmine. One of the goals of the experimental activity was to compare two wheels characterized by different designs. Mechanical performance and capacity of the wheels to reduce the energy transferred to the vehicle have been assessed to verify whether the wheels were suitable for the task and to identify which wheel performs best. Physical integrity of both wheels was assessed by visual inspection after each explosion. To evaluate the energy transferred to the vehicle, a measurement of the potential energy transferred, by means of a ballistic pendulum, equipped with an encoder, was performed together with a triaxial acceleration measurement in correspondence of the wheel hub. The triaxial accelerometer measurement was then also used to assess the behaviour of the wheels mounted on the vehicle after tests on the ballistic pendulum. Wheel performances have been quantified using specific features and frequency domain functions, related to the damage induced by the vibration at the interface between the hub and the demining machine. The obtained results suggest that the heaviest wheel performs better both in terms of mechanical integrity and of shock response.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-03T01:32:26Z
      DOI: 10.1177/20414196221075823
       
  • Dynamic mechanical properties of hybrid fiber reinforced concrete

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      Authors: Yong Zhang, Li Chen, Dong-lei Zhou
      Abstract: International Journal of Protective Structures, Ahead of Print.
      In this study, the dynamic mechanical properties of hybrid fiber reinforced concrete (HFRC) are analyzed with respect to failure mode, dynamic increase factor (DIF), and peak strain by means of a SHPB testing apparatus. The factors that influence the dynamic mechanical properties include fiber type and fiber content. It is concluded that the best dynamic mechanical properties of fibers are CS-PHFRC at medium and low strain rates and AS-PHFRC at a high strain rate. Within a certain range, the higher the fiber content is, the larger the DIF of the corresponding HFRC and the more obvious the increase in dynamic compressive strength. AS-CSHFRC improves the dynamic compressive deformability of the HFRC. The polypropylene fiber causes plasticity, as shown in the failure mode of concrete. The Ottosen nonlinear elastic model, modified by introducing the damage factor, can better describe the dynamic mechanical properties of HFRC.
      Citation: International Journal of Protective Structures
      PubDate: 2022-01-07T05:59:47Z
      DOI: 10.1177/20414196211065480
       
  • Fragment response of unreinforced concrete masonry walls subjected to
           blast loading

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      Authors: John E Hatfield, Genevieve L Pezzola, Robert E Walker, Catherine S Stephens, James S Davidson
      First page: 161
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Very few methods are available for predicting the secondary fragment velocity and secondary fragment production of ungrouted and nonreinforced concrete masonry unit (UGNR CMU) walls when subjected to blast loading. Existing approaches often require large computational resources or fail to predict secondary fragment velocity accurately. This paper presents an engineering-level analysis methodology that can be rapidly implemented to predict the velocity of fragments from UGNR CMU walls subjected to blast loading. The theoretical background and need for the methodology are discussed. Results from the analytical methodology are compared to results from two full-scale experiments and four quarter-scale experiments. A strong correlation is demonstrated between the experimental results and the analytical methodology.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-26T08:28:26Z
      DOI: 10.1177/20414196221080482
       
  • The development of specialised modular protective structure on continuous
           miners against coal burst hazards

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      Authors: Alex Remennikov, Dulara M Kalubadanage, Xiaohan Yang, Ting Ren
      First page: 182
      Abstract: International Journal of Protective Structures, Ahead of Print.
      As mining progresses into deep ore deposits in Australia, geo-hazards such as coal burst and outbursts are becoming a major concern for mine workers. The occurrence of geo-hazards involved the ejection of coal lumps and sometimes large volumes of hazardous gases such as methane and carbon dioxide. Whilst it is extremely important to de-stress and de-gas the seam and adjacent strata before roadway development and install competent support systems such as steel mesh and bolt, the last line of protection will be the installation of a protective canopy on the Continuous Miner (CM), which is typically used for roadway developments, to shield mine workers from these deadly dynamic impacts of coal and rock resulting from a burst or outburst. This paper aims to introduce the design, manufacture and testing of an innovative modular protective structure on the CM in underground coal mines. The developed protective system can be easily assembled in the underground mining environment and provide a high level of protection against flying debris hazards in the event of a coal burst. The extensive experimental program and numerical simulations have confirmed the high performance of the protective system against high-speed impact loading by single and multiple coal rocks and projectiles.
      Citation: International Journal of Protective Structures
      PubDate: 2022-02-10T02:19:12Z
      DOI: 10.1177/20414196211069574
       
  • Blast retrofit of one-way reinforced concrete members using externally
           bonded FRP and FRP anchorage

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      Authors: Christopher M. Jackson, Eric Jacques, Murat Saatcioglu
      First page: 209
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This paper presents the results of nine as-built and carbon fiber reinforced polymer (CFRP) retrofitted reinforced concrete panels subjected to simulated blast loading using a pneumatically operated shock tube. The objective of the study was to characterize the blast response of CFRP retrofitted reinforced concrete panels, with and without supplemental mechanical anchorage applied to the CFRP. The results indicate that retrofitting can significantly increase the strength and stiffness of reinforced concrete flexure members and greatly enhance the displacement time-history response over non-retrofitted members. Debonding of the externally bonded CFRP was the failure mode for all retrofitted members. FRP anchors, designed to prevent or delay debonding failures through mechanical end-anchorage, were found to substantially enhance the performance of panels experiencing critical diagonal crack debonding. However, the FRP anchors were found to have no substantial effect on retrofit performance for the case plate-end interfacial debonding failures. In addition, the displacement time-histories for as-built and FRP retrofitted panel obtained through detail single degree of freedom analysis were found correlate well with those obtained experimentally. Finally, a discussion on the practical considerations of using externally bonded FRP retrofits to resist blast loads and recommendations for protective design are presented.
      Citation: International Journal of Protective Structures
      PubDate: 2022-04-15T08:39:41Z
      DOI: 10.1177/20414196221087347
       
  • Mitigation of blast effects through novel energy-dissipating connectors

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      Authors: Michael V Seica, Jeffrey A Packer, Martin G Walker, Matthew I Gow
      First page: 236
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Explosions generate overpressures that can cause irreparable damage to structures. For many buildings, especially critical infrastructure, continued operation after an explosive attack is essential. The use of energy-dissipating methods will enable the protection of a structure and occupants from a blast and permit the timely repair and re-occupation of the building after an event.The concept behind the system presented is the creation of panels that can be used as cladding for structures. The panels are connected to the main structure using energy-dissipating component assemblies around the panel edge. When subjected to a blast load the panels transfer the blast pressure through the assemblies, thereby reducing the forces transmitted to the underlying structure. After an event, the panels and energy-dissipating component assemblies can be replaced quickly and easily, allowing the building to be reoccupied in a short time after an attack.This study focuses on the characterization of energy-dissipating component assemblies using static and dynamic laboratory testing. A predictive theory, supported by a single degree of freedom model, is developed and a general evaluation method proposed. Further laboratory testing expands the characterization of behaviour of the assemblies through experiments, with a blast generator in tension tests and in simulated blast panel tests. The time histories developed from tension tests are then compared to examine the effect of loading rate. The investigations on blast panels also include a comparison with predictions to determine whether the latter can describe the global behaviour of the system. Lastly, the response of the energy-dissipating component assemblies is evaluated in full-scale field blast tests on cladding panels.
      Citation: International Journal of Protective Structures
      PubDate: 2022-04-09T03:11:24Z
      DOI: 10.1177/20414196221074058
       
  • Innovative impact testing machine for enhancing impact related research in
           Australia

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      Authors: Mohammad Asad, Tatheer Zahra, David P Thambiratnam, Tommy HT Chan, Xuemei Liu, Yan Zhuge, Mark Hayne, Anthony Morris, Christina Nguyen
      First page: 273
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This paper summarises the development of a state-of-art impact testing machine for simulating impacts such as vehicular crashes or debris impacts onto structures. The machine has a 200 kg pneumatically powered projectile which can travel horizontally within the barrel of the machine with a maximum velocity of 50 m/s to impact the target structure. The maximum kinetic energy that can be generated by the projectile is 125 kJ by using different combinations of mass and velocity. The diameter of the projectile is 214 mm, and its impacting face can be changed to different shapes, such as flat circle, flat square or an elliptical nose to suit different impact scenarios. An innovative braking mechanism incorporating a crush tube is attached within the barrel to ensure safety when the projectile fails to be restrained by the impact. The crush tube can absorb the maximum imparted by the moving projectile. An advanced data acquisition system is installed to collect quantitative and qualitative test data during a period of 50 ms to 1 s. Two high-speed digital image correlation (DIC) cameras are attached and synchronised with the operation of the impact testing machine to record the images at the rate of 50,000 frames per second. Outputs in terms of strains, deformations, accelerations of the target structure with a record of damage history can be analysed using this 3D DIC technique. The paper also briefly presents the first application of this machine for impact testing masonry wall structures.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-04T06:56:42Z
      DOI: 10.1177/20414196211073502
       
  • Recent advances in auxetics: Applications in cementitious composites

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      Authors: Zihong Gan, Yan Zhuge, David P Thambiratnam, Tommy HT Chan, Tatheer Zahra, Mohammad Asad
      First page: 295
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Auxetic materials, possessing negative Poisson’s ratios (NPRs), have the ability to shrink (or expand) in the lateral direction under an axial compressive (or tensile) force respectively. Due to this unique feature, an auxetic material is found to sustain high energy absorption capacity, fracture toughness and shear resistance and thus regarded as one of the future materials in the field of impact protection. However, civil engineering applications of auxetic structures or materials are minimal due to miscellaneous restrictions on NPR effects. Accumulative developments in auxetics have facilitated their applications in cementitious materials in recent years. This paper presents an overview of recent advances in the development of auxetic cementitious composites and analyses and summarises their mechanical properties under different loading conditions. Prior to extensive finite element simulations, more attention has been given to the limited experimental results. Particular attention is paid to the expansionary feasibility of the parent material to introduce auxetic behaviour, with precise identification of the limitations, innovative composition methods and facilitation of auxetic features. Finally, the paper outlines the limitations of the current research and envisages few future research opportunities in auxetic cementitious composites.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-18T04:17:25Z
      DOI: 10.1177/20414196211062620
       
  • Local failure resistance of polypropylene fiber reinforced concrete plates
           subjected to projectile impact

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      Authors: Masuhiro Beppu, Koki Mori, Hiroyoshi Ichino, Yoichiro Muroga
      First page: 317
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This study investigated local failure characteristics of polypropylene fiber reinforced concrete (PPFRC) plates subjected to projectile impact. Flexural and compression tests for two types of PPFRC specimens (PPFRC1 and PPFRC2) were conducted to examine mechanical properties of the PPFRC. The average flexural strength of PPFRC1 and PPFRC2 at a strain rate of 10−1/s were 12.2 N/mm2 and 10.4 N/mm2, respectively. The average compressive strength of PPFRC1 and PPFRC2 at a strain rate of 100/s were 58 N/mm2 and 74.9 N/mm2, respectively. Projectile impact tests for 60 mm- and 80 mm-thick PPFRC plates were conducted by using a 50 g-mass projectile collided at velocities corresponding to 193–423 m/s. Experimental results exhibited that the PPFRC plate had a higher effect of suppressing local failure than a plain concrete plate. Comparison of the tests results with the modified NDRC formula revealed that the limit scabbing thickness was 15–20% smaller than that of a plain concrete plate.
      Citation: International Journal of Protective Structures
      PubDate: 2022-04-04T05:28:08Z
      DOI: 10.1177/20414196221078607
       
  • Impact resistance of porosity-free fiber-reinforced concrete (PFFRC) beams
           under low-velocity impact loading

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      Authors: Norimitsu Kishi, Masato Komuro, Katsuya Kono, Tomoki Kawarai
      First page: 344
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Ultrahigh-performance fiber-reinforced concrete (UHPFRC) is an advanced cement-based composite material. Its ultrahigh compressive strength and high ductility can enable the downsizing of structural members, with special application to high-rise buildings. These excellent mechanical properties also allow its application in protective structures to resist high-speed penetration, low-velocity impact, and blast loading. UHPFRC with a compressive strength of approximately 150–200 MPa has traditionally been used to investigate the impact resistance of structural members under low-velocity impact loading. Recently, however, porosity-free concrete of the 400 MPa class of compressive strength has been developed. In this paper, to investigate the effects of the concrete strength and the steel fiber volume fraction on the impact resistance of porosity-free fiber-reinforced concrete (PFFRC) members, static and drop-weight impact loading tests were conducted on PFFRC beams by varying the volume fraction of steel fiber from 1 to 3.5%. As reference beams, 90 MPa high-strength fiber-reinforced concrete (HSFRC) beams with a 2% fiber volume fraction and normal-strength concrete (NSC) beams without stirrups and steel fibers were also tested. The results obtained from this study were as follows: (1) the static load-carrying capacity of a PFFRC beam can be enhanced by more than two and three times that of an NSC beam by adding 1 and 3.5% volume fractions of steel fiber, respectively; (2) a PFFRC beam with 3.5% fiber had the greatest impact resistance of all the beams considered in this study, and the beam with 2% fiber volume had the second-greatest performance, but the difference was small; (3) even though an HSFRC beam with 2% fiber had a smaller static load-carrying capacity than a PFFRC beam with 1% fiber, the former exhibited a slightly greater impact resistance than the latter because the bridging effect of the steel fibers has a greater influence under impact loading than under static loading.
      Citation: International Journal of Protective Structures
      PubDate: 2022-02-21T12:16:07Z
      DOI: 10.1177/20414196211069573
       
  • Application verification of blast mitigation through the use of thuja
           hedges

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      Authors: Gajewski Tomasz, Peksa Piotr, Studziński Robert, Malendowski Michał, Sumelka Wojciech, Sielicki W Piotr
      First page: 363
      Abstract: International Journal of Protective Structures, Ahead of Print.
      Nowadays, large gatherings of people, such as open-air concerts, outdoor-sport events, trade fairs, etc., are often attracted by the terrorists. Recently, an interesting passive alternative way of securing such events against terrorist threats appeared in the scientific literature, in which the tree hedges mitigation potential against blast waves were studied. Despite comprehensive studies regarding selected species of hedge trees, the real application outlines were reported to be still missing for those barriers. Our study verified the mitigation potential of thuja in field tests for (i) several distances behind the hedge and for (ii) several positions along the hedge wall. The explosives of 5 kg trinitrotoluene with a rectangular shape were used in four detonations. Six pressure pencil gauges were registering the overpressure histories. A high-speed camera was recording the in-plane deformation of the hedge wall, the motion of selected points on the height of the wall was plotted. For each position, the reduction of overpressure peak and overpressure impulse were obtained in reference to their counterparts for the position without a hedge. The maximal overpressure peak reductions obtained were 14% for case (i) (differing distances from the explosive) and 22% for case (ii) (differing positions along the hedge wall). The experiments' outcomes showed the safest position behind the thuja wall and the actual benefit from using them in the public application if the terrorist acts would happen.
      Citation: International Journal of Protective Structures
      PubDate: 2022-05-11T11:44:46Z
      DOI: 10.1177/20414196211062927
       
  • Time of arrival as a diagnostic for far-field high explosive blast waves

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      Authors: Dain G. Farrimond, Sam E. Rigby, Sam D. Clarke, Andy Tyas
      First page: 379
      Abstract: International Journal of Protective Structures, Ahead of Print.
      The ability to accurately determine blast loading parameters will enable more fundamental studies on the sources of blast parameter variability and their influence on the magnitude and form of the loading itself. This will ultimately lead to a better fundamental understanding of blast wave behaviour, and will result in more efficient and effective protective systems and enhanced resilience of critical infrastructure. This article presents a study on time of arrival as a diagnostic for far-field high explosive blasts, and makes use of the results from a large number of historic tests and newly performed experiments where the propagating shock front was filmed using a high-speed video (HSV) camera. A new method for optical shock tracking of far-field blast tests is developed and validated, and full-field arrival time results are compared against those determined from the historic data recorded using traditional pressure gauges. Arrival time variability is shown to be considerably lower than peak pressure and peak specific impulse, and is shown to decrease exponentially with increasing scaled distance. Further, the method presented in this article using HSV cameras to determine arrival time yields further reductions in variability. Finally, it is demonstrated that the method can be used to accurately determine far-field TNT equivalence of high explosives.
      Citation: International Journal of Protective Structures
      PubDate: 2022-04-01T03:12:42Z
      DOI: 10.1177/20414196211062923
       
  • Experimental and numerical study on static and dynamic axial crushing of
           square aluminum tubes: Effects of cutouts

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      Authors: Tan-Trung Bui, Dhafar Al Galib, Abdelkrim Bennani, Ali Limam
      First page: 403
      Abstract: International Journal of Protective Structures, Ahead of Print.
      The collapse of tubes under axial load is an important subject from the safety point of view, particularly in the design of energy absorbing devices used in many engineering applications. In this study, quasi-static and dynamic experiments were carried out on square thin-walled aluminum extrusions to investigate the effects of circular holes. Cutouts were introduced in the four corners of the square-section tube, not far from the end boundary of the tube, in order both to decrease the first peak load on the load-displacement characteristic and to control the collapse mode. Different aspects, such as the buckling modes and the energy absorption in quasi-static axial crushing tests, as well as dynamic effects and material rheology contributions in dynamic crushing tests, have been examined. For the dynamic tests, the parameters were the impacting mass and its velocity. The results showed a drop in the first peak function of the openings’ radius and the tube’s energy absorption capacity was kept. A comparison between static and dynamic tests results was carried out and the interpretation of the results in terms of deformation mechanism and energy absorption was discussed. Numerical simulations with the finite element code ABAQUS were conducted to confirm the experimental findings. The results of different numerical models, implicit and explicit calculations, that contribute to a basic understanding of the buckling and prediction of the crash behavior of the aluminum components without and with the cutouts are presented.
      Citation: International Journal of Protective Structures
      PubDate: 2022-01-15T03:28:13Z
      DOI: 10.1177/20414196211065477
       
  • From impact of RC flat slabs in a building to its progressive collapse

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      Authors: David Z. Yankelevsky, Yuri S Karinski, Dina Tsemakh, Vladimir R. Feldgun
      First page: 439
      Abstract: International Journal of Protective Structures, Ahead of Print.
      This paper presents a realistic model for the simulation of a progressive collapse scenario in a typical low-rise building that is constructed from RC flat slabs and supported by columns. The progressive collapse scenario starts after failure of the top slab connections, where the slab is falling downward and impacts with the slab below. This impact event is analyzed, and the dynamic failure of the impacted slab’s connections starts the progressive collapse event. Two different scenarios are identified, depending on the first slab damage condition prior to impact. The first scenario refers to an undamaged impacting slab where an elastic collision occurs with the slab below; in the second scenario, the first slab is damaged, and its collision with the slab below is plastic. In the first scenario, the impacting slab velocity drops to zero while its velocity is fully imparted to the impacted slab. In the second scenario, both slabs continue their motion jointly at a common velocity. In the subsequent impacts, the impacting slabs are a-priori damaged, hence plastic collisions occur. These impact occurrences are analyzed separately, depending on the number of impacting slabs involved, damage characteristics, and impact velocity. Due to the nature of the first impact, the first scenario is characterized by separate motion of the first impacting slab which is falling behind the other slabs. This slab gains speed until it meets the other falling slabs below at a certain altitude, and an intermediate collision occurs, not necessarily at a floor level. In the analyzed five-story building, the intermediate impact occurs after the third impact event, where the slabs are located slightly above the first story level. The intermediate impact elevates the velocity of the impacted slabs such that their impact with the first level slab is more severe and its motion toward hitting the ground level is faster.
      Citation: International Journal of Protective Structures
      PubDate: 2022-03-28T05:03:51Z
      DOI: 10.1177/20414196221078024
       
 
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