JournalTOCs

International Journal of Protective Structures
Journal Prestige (SJR): 0.841

Citation Impact (citeScore): 1
Number of Followers: 6

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2041-4196 - ISSN (Online) 2041-420X
Published by Sage Publications

[1099 journals]

Impact damage protection mechanisms for elastomer-coated concrete
- Authors: Chanel Fallon, Graham J McShane
  Abstract: International Journal of Protective Structures, Ahead of Print.
  Cost-efficient strategies for protecting structural elements against the effects of explosive detonations are of interest for vulnerable infrastructure. Dynamic loading due to both blast pressures and impact from fragments are of concern. This investigation focuses on the protection of concrete structural elements against impact damage. A recent experimental study by the authors demonstrated that an elastomer coating can provide a significant impact mitigating effect when applied to the impacted face of a concrete substrate. Preliminary numerical results have indicated that the elastomer serves to alter the details of damage initiation in the concrete, though there remains a limited understanding of the protective effects at play. In this work, a numerical investigation is performed to determine the mechanisms of impact damage initiation exhibited by a concrete circular cylinder of diameter, 100 mm and height, 100 mm when impacted by a 0.1 kg circular cylindrical (i.e. blunt) projectile, travelling at velocities in the range 5–150 m s−1. The influence of applying a 5 mm elastomer coating on these damage mechanisms is assessed. At the lowest impact velocities, the concrete remains undamaged, though the sub-surface stress state is influenced by the polymer coating. At higher impact velocities, two distinct damage initiation mechanisms are observed. Damage Mechanism 1 is characterised by immediate, severe concrete damage initiating under the indenter corner. Damage Mechanism 2 is characterised by more diffuse, sub-surface damage. Adding a polymer coating serves to shift damage initiation from Damage Mechanism 1–2, delaying the onset of severe concrete damage. Simplified 1D and 2D numerical models are employed to interrogate how the elastomer achieves this effect. Two protective effects are identified: (i) a temporal effect causing a reduction in the magnitude of peak acceleration and an increase in contact duration between projectile and target and (ii) a spatial effect where the stress concentration under the indenter corner is removed.
  Citation: International Journal of Protective Structures
  PubDate: 2021-01-19T05:16:17Z
  DOI: 10.1177/2041419620984811
Strong-axis response of steel I-sections subjected to close-in detonations
- Authors: Hezi Y Grisaro, Michael V Seica, Jeffrey A Packer, Wei Li
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The analysis of structural members subjected to close-in detonations involves a complicated dynamic scenario. Since the charge is very close to the structural member, the reflected pressure distribution on the member surface is highly non-uniform. In addition, the level of damage to the structural member may be high because of the large magnitude of the load. Due to these phenomena, the response of a structural member to close-in detonation cannot be accurately modelled by relatively simple methods like single-degree of freedom models, and more complicated models are required. Such models need to include numerical simulation of the detonation process, which produces a non-uniform pressure environment, allowing the pressure to reflect and flow around the member section. The local damage and flow around the section are especially of interest in I-shaped, or wide-flange-section members. Herein, the response of such sections is modelled by numerical simulations using a novel technique, which overcomes the difficulty of computation time, and is validated through various calculations. The model is used to perform a parametric study to investigate the response of I-sections subjected to close-in detonations, in terms of local damage and global behaviour, with scaled distances of 0.15–0.29 m/kg1/3 and loading causing flexure about the strong axis. Various aspects that affect the performance are studied, such as: the effect of scaled distance, the addition of welded stiffening plates between the flanges and web, the effect of boundary conditions and the effect of charge shape. Resulting local damage and residual deformations are assessed for the cases studied.
  Citation: International Journal of Protective Structures
  PubDate: 2020-12-29T10:26:54Z
  DOI: 10.1177/2041419620984487
Multi-performance blast pressure-duration curves of laminated glass panes
- Authors: Mohammadreza Eslami, Khalid M Mosalam, Venkatesh Kodur, Shalva Marjanishvili, Brian Katz, Hussam N Mahmoud
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The current design procedure for blast resistant glass panes is based on dynamic analysis of idealized SDOF models under simplified triangular impulse loads or code-specified pressure-duration (pressure-impulse) curves. In both cases, the main objective is to prevent failure of the pane with no explicit consideration of other limit states to reach higher performance levels. In this study, multi-performance pressure-duration curves of Laminated Glass (LG) panes are estimated by accurate pre-validated Finite Element (FE) models. Multiple performance criteria including initial cracking, PVB-50% (maximum polyvinyl butyral, i.e. PVB, interlayer strain of 50%), PVB-100% (maximum PVB interlayer strain of 100%), and ultimate failure of the pane are considered and pressure-duration curves are estimated for each of these performance levels. Ultimate failure of the pane can be either due to rupture of the PVB interlayer or pull-out of the pane from its frame. Multi-performance pressure-duration curves are obtained for 18 different LG panes with three different layups, two widths, and three aspect ratios. According to the obtained results, the thickness of the glass layers has more pronounced contribution to the blast resistance of the panes in all limit states compared with the PVB thickness. Moreover, the ultimate failure mode of the LG panes with thicker PVB interlayer is observed to be typically pull-out of the pane rather than PVB rupture. Therefore, these panes require frames with deeper bites to develop their full blast resistance. Finally, the blast performance of the LG panes are compared with that of Thermally Tempered Glass (TTG) panes to shed more light on the superior blast resistance of LG panes.
  Citation: International Journal of Protective Structures
  PubDate: 2020-12-02T09:33:00Z
  DOI: 10.1177/2041419620968838
Assessment of confinement’s influence on a concrete target’s ability
to approximate semi-infinite perforation performance
- Authors: Jared L Brown, Isaac L Howard, Andreas O Frank, M. Jason Roth
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The ability to accurately evaluate impact penetration resistance of a structural element in an experimental setting often requires the experimental impact specimen configuration to be as close as possible to a structural element in a fielded protective design scheme. This includes the target’s capability to estimate the semi-infinite response of a structural element such as a wall where inertial confinement is provided by undamaged material surrounding the area damaged by impact. Artificially simulating this confinement in an experimental target can take several forms, including use of a circumferential steel ring as a confining medium. Experimental data gathered from impact tests were utilized to create a representative numerical simulation of a confined target design. This simulation evaluated artificial and inertial confinement on concrete perforation by varying target to projectile diameters with and without artificial confinement. Perforation performance was found to be unaffected by confinement type when the target diameter to projectile diameter ratio was 16. Semi-infinite surface approximation was found to occur when the target diameter to projectile diameter ratio was 64 despite the confinement type at higher impact velocities; however, this ratio could be reduced while maintaining semi-infinite performance for lower velocity impacts.
  Citation: International Journal of Protective Structures
  PubDate: 2020-12-01T07:36:15Z
  DOI: 10.1177/2041419620977519
Failure analysis of steel open dam against an extreme boulder debris flow
- Authors: Toshiyuki Horiguchi, Hiroshi Kokuryo, Nobutaka Ishikawa
  Abstract: International Journal of Protective Structures, Ahead of Print.
  This paper presents a failure analysis for a steel open-type Sabo dam (hereafter, steel open dam) against an extreme boulder debris flow load (hereafter, level II load) by a two-step analysis. The first step analysis is to estimate the level II load against the rigid wall by using the revised distinct element method (DEM). In the second step, the failure mechanism of a steel open dam is examined by using a dynamic elastic plastic analysis, in which the level II load-time relations obtained by the first analysis are multiplied by a reduction factor and then used. For the second step, the effects of the flange joint and dent deformation of the connection between column and beam are considered. Finally, a simple entire uniform load onto the steel open dam is proposed as a level II load model for the safety assessment.
  Citation: International Journal of Protective Structures
  PubDate: 2020-11-21T09:57:29Z
  DOI: 10.1177/2041419620970566
TNT equivalency analysis of specific impulse distribution from close-in
detonations
- Authors: Hezi Y Grisaro, Idan E Edri, Samuel E Rigby
  Abstract: International Journal of Protective Structures, Ahead of Print.
  Detonation of a high explosive close to a structural component results in a blast load that is highly localized and nonuninform in nature. Prediction of structural response and damage due to such loads requires a detailed understanding of both the magnitude and distribution of the load, which in turn are a function of the properties and dimensions of the structure, the standoff from the charge to the structure, and the composition of the explosive. It is common to express an explosive as an equivalent mass of TNT to facilitate the use of existing and well-established semi-empirical methods. This requires calculation of a TNT equivalency factor (EF), that is, the mass ratio between the equivalent mass of TNT and the explosive mass in question, such that a chosen blast parameter will be the same for the same set of input conditions aside from explosive type. In this paper, we derive EF for three common explosives: C4, COMP-B, and ANFO, using an equivalent upper bound kinetic energy approach. A series of numerical simulations are performed, and the resultant magnitudes and distributions of specific impulse are used to derive the theoretical upper bound kinetic energy that would be imparted to a flexible target. Based on the equivalent mass of TNT of each explosive, which is required to impart the same kinetic energy for a given target size and standoff distance as of TNT, the EF is calculated. It is shown that in the near-field, the EFs are non-constant and are dependent on both standoff and target size. The results in the current study are presented in a scaled form and can be used for any practical combination of charge mass, distance from the charge to the target, target size, thickness, and density.
  Citation: International Journal of Protective Structures
  PubDate: 2020-11-13T05:52:18Z
  DOI: 10.1177/2041419620972423
Numerical prediction of damage mechanisms of E-Glass/epoxy composite
material against ballistic impact of 7.62 MS projectile
- Authors: Venkata Ramudu Bodepati, Jayarami Reddy C, Madhu Vemuri
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The fibre reinforced polymer matrix composite materials have acquired more credibility over other materials like metals and ceramics due to their high specific strength. Numerical simulations of ballistic impact of 7.62 mild steel projectile on various thicknesses of plain woven E-Glass/epoxy composite material were performed. Residual velocity and ballistic limit of the composite material were determined numerically and the results are compared with that of experiments published elsewhere. The numerical and experimental results are in good agreement. The numerical results are also compared with Recht-Ipson (R-I) and Gellert et al analytical models and are found to be in good correlation. Various failure mechanisms such as two stage damage mechanism namely dishing in target materials less than 10mm and indentation followed by dishing in target materials greater than 10 mm, delamination, and fibre and matrix failure modes of the composite material were studied and compared with the analytical models and experimental results. The wave propagation mechanisms and the damage phenomena are also studied and correlated.
  Citation: International Journal of Protective Structures
  PubDate: 2020-11-12T05:32:27Z
  DOI: 10.1177/2041419620967023
Prediction of blast loading in an internal environment using artificial
neural networks
- Authors: Adam A Dennis, Jordan J Pannell, Danny J Smyl, Sam E Rigby
  Abstract: International Journal of Protective Structures, Ahead of Print.
  Explosive loading in a confined internal environment is highly complex and is driven by nonlinear physical processes associated with reflection and coalescence of multiple shock fronts. Prediction of this loading is not currently feasible using simple tools, and instead specialist computational software or practical testing is required, which are impractical for situations with a wide range of input variables. There is a need to develop a tool which balances the accuracy of experiments or physics-based numerical schemes with the simplicity and low computational cost of an engineering-level predictive approach. Artificial neural networks (ANNs) are formed of a collection of neurons that process information via a series of connections. When fully trained, ANNs are capable of replicating and generalising multi-parameter, high-complexity problems and are able to generate new predictions for unseen problems (within the bounds of the training variables). This article presents the development and rigorous testing of an ANN to predict blast loading in a confined internal environment. The ANN was trained using validated numerical modelling data, and key parameters relating to formulation of the training data and network structure were critically analysed in order to maximise the predictive capability of the network. The developed network was generally able to predict specific impulses to within 10% of the numerical data: 90% of specific impulses in the unseen testing data, and between 81% and 87% of specific impulses for data from four additional unseen test models, were predicted to this accuracy. The network was highly capable of generalising in areas adjacent to reflecting surfaces and as those close to ambient outflow boundaries. It is shown that ANNs are highly suited to modelling blast loading in a confined internal environment, with significant improvements in accuracy achievable if a robust, well distributed training dataset is used with a network structure that is tailored to the problem being solved.
  Citation: International Journal of Protective Structures
  PubDate: 2020-11-09T06:37:08Z
  DOI: 10.1177/2041419620970570
Evaluating the resistance of metal reinforced multi-layer textile
structure against penetration of sharp objects
- Authors: Forough Amirshirzad, Fatemeh Mousazadegan, Nazanin Ezazshahabi
  Abstract: International Journal of Protective Structures, Ahead of Print.
  One of the common applications of textile protective structures is making barriers against penetration of sharp objects. Multilayer fabrics can absorb energy and are a proper candidate to be used in body armors. In this study, a three-layer textile structure which is reinforced by metal threads has been designed and produced. Metal reinforced layer was woven through a particular weaving system. Force and energy of penetration in each layer and also the three-layer textile structure was measured. The test results revealed that the layer resistance against penetration of sharp objects varied depending on the strucure of each layer. The metal reinforced layer had the highest penetration force and energy. In the three-layer textile structure, the resistance behavior of each layer was observed separately and stepwise. Thus, the force peaks in the three-layer textile structure were related to the peak forces in each layer, and the maximum penetration force of three-layer structure was similar to penetration force of metal-reinforced layer. When putting three layers on each other, the penetration energy has increased, and the designed multi-layer textile structure has performed efficiently in absorbing the penetration energy of sharp objects. Due to the stepwise resistance of three-layered textile structure, its obtained penetration energy, was divided into two energy values of external layer and both middle and inner layers. Thus, accumulation of penetration energy of single external, middle and inner layers was in good agreement with penetration energy of three-layer textile structure.
  Citation: International Journal of Protective Structures
  PubDate: 2020-10-31T07:11:09Z
  DOI: 10.1177/2041419620968843
Evaluation of punching shear design criteria to prevent progressive
collapse of RC flat slabs
- Authors: David Z Yankelevsky, Yuri S Karinski, Alex Brodsky, Vladimir R Feldgun
  Abstract: International Journal of Protective Structures, Ahead of Print.
  This study focuses on a RC building with flat slabs that were designed according to current standards. A scenario of a slab with failed connections that is detached from its supporting columns and is falling downward is considered, and the impact results with the slab underneath are assessed. The suitability of the standards design criteria to provide safe design against impact loading is evaluated. It was found that larger span slabs experience heavier damage. Falling from a floor height and from a quarter floor height are analyzed and the damage results of these impacts are examined. At the lower impact velocity, the concrete slab surrounding the column undergoes major damage and shear deformations; In the case of a relatively short span slab, the rebars undergo large plastic deformations and almost reach the ultimate strain, such that a slightly higher impact velocity would cause rebars fracture and total failure of the slab-column connection. In the case of high impact velocity, the concrete in the slab around the column is fully crashed and the longitudinal and the bent up rebars are ruptured. The yield of the rebars occurs within a few milliseconds. During this extremely short time the impacted slab hardly starts developing its downward displacement. The impacted slab responds like a rigid body with severe damage concentration at the slab-column connection region. Different parameters affecting the slabs dynamic response are examined, and new insight is gained on the complex impact response of flat RC slabs. This study finds that the current design standards that are based on static loading considerations do not provide resilience to flat slab connections that are subjected to impact loading and therefore cannot prevent a progressive collapse scenario.
  Citation: International Journal of Protective Structures
  PubDate: 2020-10-16T09:26:56Z
  DOI: 10.1177/2041419620964221
Blast resistant behaviour of tunnels in sedimentary rocks
- Authors: Mohammad Zaid, Md Rehan Sadique
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The tunnels are being constructed for the faster movement of goods and services from different locations. Therefore, Underground Urban Space (UUS) has evolved as an integral part of metro cities. Critical structures like tunnels have to be designed resistant to the blast due to possible threats and attacks. In the present paper, the efforts are made to analyse and understand the response of rock tunnel for an internal blast loading. The numerical analysis based on the finite element method has been carried out for a 35 m long rock tunnel in a rock mass of longitudinal cross-section 30 m × 30 m. The elastoplastic behaviour of the sedimentary rocks, that is, Sandstone, Mudstone and Silty Sandstone has been incorporated by using a Mohr-Coulomb constitutive material model. The plastic behaviour of the concrete tunnel lining has been incorporated by using concrete damage plasticity model. Moreover, for the Trinitrotoluene (TNT) Jones-Wilkens-Lee (JWL) material model has been considered. Analysis has been performed through the Coupled-Eulerian-Lagrangian (CEL) approach, which incorporates the advantages of both Eulerian and Lagrangian modelling. The present study focuses on the analysis of the tunnels constructed in three different sedimentary rocks, that is, Sandstone, Silty Sandstone and Mudstone. It has been concluded that Mudstone rock is more susceptible to failure due to internal blast load. However, Sandstone rocks were found to be relatively higher blast resistant, hence, may be considered as safer rocks for the construction when compared to other rocks of the present study.
  Citation: International Journal of Protective Structures
  PubDate: 2020-08-20T02:19:59Z
  DOI: 10.1177/2041419620951211
Numerical modeling of confined brick masonry structures with parametric
analysis and energy absorption calculation
- Authors: H Asfandyar Ahmed, Khan Shahzada
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The objective of this paper is to propose a new modeling methodology for numerical analysis of full-scale confined brick masonry structures. Two modeling strategies are used within a single structure, where the in-plane walls are modeled using “simplified micro-modeling” approach and out-of-plane walls are modeled using “macro-modeling” approach. The lateral load capacity is associated with the in-plane shear resistance of masonry elements, therefore more detailed analysis is required for in-plane walls to achieve a comprehensive understanding of the damage mechanism and load transfer. The investigation of the in-plane shear behavior of confined brick masonry structures is of significant importance. Additionally, the proposed hybrid model is validated by comparing the results of experimental studies of confined brick masonry structure. A parametric study is then conducted to investigate the effect of brick and mortar properties on the structural response metrics (e.g. base shear coefficient, effective stiffness, response modification factor, the three performance levels (i.e. Immediate Occupancy, Life Safety and Collapse Prevention limits) and the energy absorption properties). It is observed that these structural response metrics, changed considerably by varying the material properties. Apart from that, the damage behavior and damage pattern are also assessed for the better understanding of effect of these parameters on the response of the structure. The proposed hybrid-modeling approach gives sufficient accuracy in predicting the lateral load behavior as well as the damage mechanism of confined brick masonry structure, subjected to lateral loading.
  Citation: International Journal of Protective Structures
  PubDate: 2020-08-10T11:40:48Z
  DOI: 10.1177/2041419620947730
Experimental–theoretical investigation for damage assessment of a
reinforced concrete slab under consecutive explosions based on
single-degree-of-freedom model
- Authors: Seung-Hun Sung, Hun Ji, Jinwung Chong
  Abstract: International Journal of Protective Structures, Ahead of Print.
  This study performed damage assessment of a reinforced concrete slab subjected to consecutive explosions. To this end, the resistance functions were updated to account for the permanent displacement calculated in the previous step to capture the response of the reinforced concrete slab of the current explosion. In other words, the permanent deformation should be basically evaluated according to the prior explosion. Next, the revised resistance function should be calculated according to damage level. Third, the maximum dynamic responses should be estimated based on the modified single-degree-of-freedom model. Finally, cumulative damages can be evaluated based on the sum of the permanent deformation and the maximum dynamic responses. In order to confirm a feasibility of the proposed single-degree-of-freedom model, a comparative study with the finite element analysis results is carried out under the identical consecutive explosions. Prior to performing the comparative study, the computational model of the target structure is calibrated based on small-scale experimental data to carry out more reliable finite element analysis.
  Citation: International Journal of Protective Structures
  PubDate: 2020-07-24T02:17:48Z
  DOI: 10.1177/2041419620938066
The penetration of limestone targets by rigid projectiles: Revisited
- Authors: Zvi Rosenberg, Yaniv Vayig, Alon Malka-Markovitz, Roman Kositski
  Abstract: International Journal of Protective Structures, Ahead of Print.
  We reanalyze the results from a set of terminal ballistics tests in which large limestone targets were impacted by similarly shaped rigid projectiles having different sizes. Our first goal is to show that the data in terms of penetration depths as a function of impact velocity can be accounted for by a model in which the limestone’s resistance to penetration is constant throughout the penetration process. It turns out that the actual values of this penetration resistance, as derived from the data, decrease with the projectile’s size. This is a clear manifestation of a scaling issue in the terminal ballistics of the limestone rock. In order to account for this issue we assume that it is closely related to the size effect in the compressive strengths of rock specimens. Finally, we offer a simple procedure by which one can define a surrogate material model for the targets in numerical simulations, in order to predict the penetration depths in limestone, and possibly other rock targets, under both normal and oblique impacts.
  Citation: International Journal of Protective Structures
  PubDate: 2020-07-17T02:44:19Z
  DOI: 10.1177/2041419620942260
Peak overpressure and impulse due to diffraction over a cylinder and/or
multi-reflection of a shock wave in structural design- Part I
- Authors: Andreas Hahn, Martin Mensinger, Marcus Rutner
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The design and planning of structural components, such as columns, to resist blast loads is a complex task. Often standard free-field blast loads, specified in design codes or other literature, are used for the analysis of the object. These loads are then further increased or decreased depending on the topology of the surrounding geometry (Mach-Stem), the shape of the impacted object itself, and blast wave reflection. However, most of these research works focus purely on the assessment of the structural components itself, ignoring a complex fluid mechanics phenomenon such as diffraction, which is of particular interest when circular columns are standing next to each other or placed in front of a façade. The article addresses three main topics. First, the article answers the question whether the area behind the column is protected, meaning constituting a shadowed area. We present findings that the close area behind a column is subjected to higher pressure and impulse values as there would be without the column. Hence, the incident pressure sees significant pressure buildup due to diffraction. This pressure buildup is quantified using pressure increase factors and presented together with the accompanying impulse. Second, this pressure buildup is of relevance for realistic design of a façade behind the column, which is not covered in current design codes at all. We discuss relevant parameters in the design process. Third, directly coupled with the assessment of the pressure buildup behind the column due to diffraction is the assessment of pressure and impulse in the area behind the column due to multi-wave reflection at a façade, leading to a significant pressure and impulse scale-up, which might be relevant for design of a column and/or a façade. This article identifies gaps in understanding diffraction and subsequent multi-reflection of blast wave within a structural design framework and provides insights on how to establish safe design accounting for these effects.
  Citation: International Journal of Protective Structures
  PubDate: 2020-07-03T06:06:07Z
  DOI: 10.1177/2041419620918883
High strain rate and low temperature effects on the compressive behaviour
of concrete
- Authors: Thomas J MacLean, Alan Lloyd
  Abstract: International Journal of Protective Structures, Ahead of Print.
  Temperature and strain rate are important factors when considering the mechanical properties of engineering materials, as they can greatly influence the material behaviour. The research presented here is an experimental investigation to determine the effects of low temperatures and high strain rates on the compressive behaviour of concrete. The primary purpose of the research is the development of experimental stress–strain relationships under these conditions, as this is a largely unexplored research topic. Thirty-five 101.6 mm × 203.2 mm concrete cylinders were tested in uniaxial compression at the University of New Brunswick. The specimens were loaded either under static conditions or dynamically with an average strain rate of approximately 1 s−1, while being exposed to temperatures from 20°C to −70°C to simulate extreme climatic temperature and those attainable within industrial storage facilities. The compression strain of the specimens was obtained using digital image correlation. The mechanical properties studied were the compressive strength, strain associated with the peak stress and general stress–strain behaviour due to the increased strain rate and temperature variations.
  Citation: International Journal of Protective Structures
  PubDate: 2020-06-24T06:31:00Z
  DOI: 10.1177/2041419620927418
Response mechanisms of reinforced concrete panels to the combined effect
of close-in blast and fragments: An integrated experimental and numerical
analysis
- Authors: Paolo Del Linz, Tat Ching Fung, Chi King Lee, Werner Riedel
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The effect of cased explosives on reinforced concrete components is important for the design of protective structures, since the interaction between the fragments and blast waves can modify or even amplify the damage caused. This work deals with the development of finite element analysis techniques to simulate the combined loading and to understand this interaction. In this work, an experiment conducted with a cased explosive and further tests from the literature were used together to develop and stepwise validate finite element analysis models of the different loading phases. The casing fragment velocities and spatial distribution were derived from explosive expansion simulations of the hull using the smooth particle hydrodynamics method together with a momentum conserving penalty contact. The blast loading applied on the concrete plate was based on established empirical formulae, acting at the same times as the fragments. Comparing the final damage with the experimental records revealed good agreement for most damage patterns. The model was used to identify the different damage evolution stages, such as shock-induced shear plug formation and subsequent structural dynamic bending with the associated damage. In addition, differential model variants with fragment and blast loading in isolation were simulated to resolve the response and damage of each loading component. The blast load caused predominantly bending deformations and damage, while the fragments caused similar cratering as seen in the combined case. However, the final combined damage was larger than that caused by each phenomenon. In the given situation, the fragments created most damage, but the established modelling approach opens the perspective to study these effects also for other ratios of explosive to casing weight and scaled distances, where the contributions might differ. Establishing a valid modelling approach is thus an important step towards more insight into the interaction of these complex loading types and damage effects.
  Citation: International Journal of Protective Structures
  PubDate: 2020-06-07T05:11:03Z
  DOI: 10.1177/2041419620923129
Stress propagation and debonding effects in impedance-graded
multi-metallic systems under impact loading
- Authors: PLN Fernando, Damith Mohotti, Alex Remennikov, PJ Hazell, H Wang, Ali Amin
  Abstract: International Journal of Protective Structures, Ahead of Print.
  This article investigates the performance of an impedance-graded multi-metallic system. Material combinations of steel–titanium, steel–aluminium and steel–titanium–aluminium are compared against a monolithic steel configuration. The experiments were carried out using a single-stage gas gun, where the target specimens consisted of these material configurations. The targets were subjected to the impact of an aluminium flyer at a velocity of 180 m/s, where elastic waves were expected to propagate through the target. The free surface velocity of the final material in the target was measured and these readings were used to quantify the stresses in the materials. These stress results were compared with the output from two-dimensional axisymmetric numerical models and theoretical equations. The findings of this study indicated that a target configuration with gradual impedance reduction could minimize the magnitudes of both compressive and tensile stresses in the materials, where the latter is critical towards preventing debonding in a multi-material system.
  Citation: International Journal of Protective Structures
  PubDate: 2020-05-12T10:37:50Z
  DOI: 10.1177/2041419620917709
Damage evaluation and protection method of resin pipe for gas conduit
subjected to impact load
- Authors: Hiroki Tamai, Sota Jinkawa, Yoshimi Sonoda
  First page: 423
  Abstract: International Journal of Protective Structures, Ahead of Print.
  Medium-density polyethylene pipe has been widely introduced to low-pressure gas pipes because of its high flexibility and corrosion resistance. However, many third-party damages due to the impact of heavy equipment have been reported during the construction every year, thus, to prevent the third-party damage, materials such as high-density polyethylene and polyamide have been considered as the new gas pipe candidates. However, their impact resistance capacity under the third-party attack has not been clarified. In this study, static and impact loading experiments were conducted to compare load resistance capacities. As a result, it was revealed that the high-density polyethylene pipe and the polyamide pipe had higher static load capacity and impact resistance than the medium-density polyethylene pipe. By comparing the absorbed energy of the static test and the impact test and calculating the pseudo absorbed energy of the impact test, the evaluation formula judging the safer side of whether the penetration occurred was proposed. Furthermore, as one of the methods to protect the gas pipe, the protective effect of winding a sheet made of reinforced fiber and non-woven fabric was clarified.
  Citation: International Journal of Protective Structures
  PubDate: 2020-01-28T11:37:26Z
  DOI: 10.1177/2041419620902791
Effect of explosion source location on tunnel damage
- Authors: Petr Prochazka, Dagmar Jandeková
  First page: 448
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The experimental study, the results of which are presented in this article, focuses on the shock wave behavior in scale models of tunnel structures and their consequences on the damage of tubes simulating tunnel lining. The source of the explosion is located either on the longitudinal axis of the tunnel or it is located near the bottom of the tunnel. The second case is more akin to reality. This article analyzes the consequences of the location of explosion sources and the influence of their brisance. In order to compare the effects of explosions on the tunnel lining, the effect of the charge deposited on the axis of the tunnel is investigated on a 0.5-m-diameter tube, while the effect of the charge deposited outside the tunnel axis is monitored on a 1-m-diameter tube. Thus, the magnitudes of the brisance may be comparable for both cases. The characteristics of the shock waves are described. The mass of the charges is graded so as not to allow a total collapse of the structure, but to manifest its damage.
  Citation: International Journal of Protective Structures
  PubDate: 2020-03-23T02:25:53Z
  DOI: 10.1177/2041419620907924
Approximating a far-field blast environment in an advanced blast simulator
for explosion resistance testing
- Authors: Edward Chern Jinn Gan, Alex Remennikov, David Ritzel, Brian Uy
  First page: 468
  Abstract: International Journal of Protective Structures, Ahead of Print.
  While the current state of blast-resistant design methods is based largely on empirical observations of actual explosive testing or numerical simulations, experimental testing remains the ultimate method for validating blast protection technologies. Field trials for performing systematic experimental studies are exceedingly expensive and inefficient. Conventional blast simulators (shock tubes) enable blast testing to be performed in a safe and controlled laboratory environment but are significantly deficient. The Australian National Facility of Physical Blast Simulation based on the ‘Advanced Blast Simulator’ concept was established to address the shortcomings of conventional blast simulators (shock tubes). The blast simulator at the National Facility of Physical Blast Simulation is a state-of-the-art design having a test section of 1.5 × 2.0 m with dual-mode driver able of operating with either compressed gas or gaseous detonation modes. The simulator is capable of a range of blast-test configurations such as full-reflection wall targets and diffraction model targets. This article aims to demonstrate the ability of the Advanced Blast Simulator in accurately generating a far-field blast environment suitable for high-precision and repeatable explosion testing of various building components. Blast pressure-time histories generated with the Advanced Blast Simulator are validated against equivalent TNT free-field curves reproduced with Conventional Weapons Effects Program. Numerical models based on Computational Fluid Dynamics were developed in ANSYS FLUENT to accurately characterise and visualise the internal flow environment of the National Facility of Physical Blast Simulation Advanced Blast Simulator. The Computational Fluid Dynamics model was also used to explain experimental observations and to determine density and dynamic pressure information for comparisons with free-field explosion conditions.
  Citation: International Journal of Protective Structures
  PubDate: 2020-03-14T05:10:40Z
  DOI: 10.1177/2041419620911133
Design guidelines and optimization of ultra-high-performance
fibre-reinforced concrete blast protection wall panels
- Authors: Mohtady Sherif, Hesham Othman, Hesham Marzouk, Hassan Aoude
  First page: 494
  Abstract: International Journal of Protective Structures, Ahead of Print.
  Ultra-high-performance fibre-reinforced concrete is the latest generation of structural concrete, having outstanding fresh and hardened properties; this includes the ease of placement and consolidation with ultra-high mechanical properties, as well as toughness, volume stability, durability, higher flexural and tensile strength, and ductility. As more research is being focused on it, the material behaviour and characteristics are getting more understood, and the research demand for the special applications of the ultra-high-performance fibre-reinforced concrete is growing higher. One special application that ultra-high-performance fibre-reinforced concrete is thought to have an outstanding performance at is in the field of protective structures, specifically against blast loads. This article presents part of a study that is concerned with the behaviour and response of ultra-high-performance fibre-reinforced concrete wall panels under blast load. Size and shape optimization techniques were combined in this study to optimize the design of a 200-MPa ultra-high-performance fibre-reinforced concrete under blast loads using finite element modelling. This design optimization aims to maximize stiffness and minimize the cost while satisfying both design stresses and construction requirements. The design variable to be optimized for are the thickness ranging from 100 to 300 mm at 25 mm increments, in addition to the reinforcement ratio of 0%, 0.2%, 1% and 3%, and aspect ratio of 1, 1.5 and 2; the boundary condition is four edges fixed and restrained. The numerical simulation has been performed using an explicate finite element software package. The complete behaviour of an ultra-high-performance fibre-reinforced concrete is defined using the concrete damaged plasticity model. The concrete constitutive model has been developed considering the contribution of tensile hardening response, fracture energy and crack-band width approaches to accurately represent the tensile behaviour and guarantee mesh independence of results. The blast load is applied using the Conventional Weapons method of the US Army Corps of Engineers that is readily available in the finite element software. The validity of the numerical model used is verified by comparing numerical results to experimental data.
  Citation: International Journal of Protective Structures
  PubDate: 2020-04-21T07:07:35Z
  DOI: 10.1177/2041419620912751
Constant deceleration approaches for penetration analysis of rigid
projectile into concrete: Revisited
- Authors: David Z Yankelevsky, Vladimir R Feldgun
  First page: 515
  Abstract: International Journal of Protective Structures, Ahead of Print.
  A new approach of constant deceleration penetration into concrete targets has been presented recently. It is based on observations from two-dimensional numerical simulations of penetration into aluminum targets, showing a rather constant deceleration during the tunneling stage, which leads to conjecturing a general simple constant deceleration approach to represent constant resistance during penetration. This approach has been extended to concrete materials despite their entirely different behavior. This article reviews the one-stage constant deceleration approach and compares it with test data and with analytical and numerical models. This study clearly shows that concrete penetration cannot be presented by the proposed constant deceleration approach. The constant deceleration approach assigns constant deceleration to the projectile from its impact with the target and ignores the entrance stage. This study shows that a two-stage simplified approach shows superior results compared to the one-stage approach. Experimental studies with instrumented projectiles show that although at low-strength concrete the deceleration variation with time is moderate, its variation with time at higher strength concrete is significant. The variable deceleration–time records are confirmed by theoretical models using the material constitutive relationships. It has been found that the proposed constant deceleration is merely a calibration constant to the measured penetration depth and does not represent a physical deceleration of the penetrating projectile. It is concluded that there cannot exist a simplified approach with a constant deceleration or even an arbitrarily predefined another shape of the deceleration curve that may properly represent different penetration scenarios in concrete targets.
  Citation: International Journal of Protective Structures
  PubDate: 2020-05-14T06:20:08Z
  DOI: 10.1177/2041419620914646
Development of finite element model for embedded carbon fiber–reinforced
polymer rod in reinforced concrete frame joints
- Authors: Shahnaz Basim, Farzad Hejazi, Raizal Saifulnaz Bin Muhammad Rashid, Milad Hafezolghorani Esfahani
  First page: 533
  Abstract: International Journal of Protective Structures, Ahead of Print.
  The stiffness and strength of joints are the main factors in providing stability and ductility of a structure during dynamic load such as earthquake. In the high-humidity areas, the reinforcement is exposed to corrosion, which commonly occurs in the joints, due to the presence of micro-cracks in the joints, shrinkage or other concrete casting issues. Therefore, one of the main failure mechanisms of building during an earthquake is caused by damage in the joints in humid areas. This is mainly caused by corroded steel reinforcement, which reduces functionality of the frame joints in transferring the loads. This study proposes a new design for reinforced beam–column joints with embedded carbon fiber–reinforced polymer rods, which possesses extremely high strength and resistance against corrosion and high stiffness. The finite element model for embedded carbon fiber–reinforced polymer in the joints was developed in order to evaluate the performance of the proposed joints during earthquake execution. The developed program was verified through an experimental test on reinforced concrete frame subjected to vibration using dynamic actuator. The finite element program was implemented for one-story reinforced concrete frame and two-story frame building with proposed joints and seismic analysis. The results demonstrated a significant improvement in the performance of the frames reinforced with embedded carbon fiber–reinforced polymer in joints in terms of lateral load resistance capacity and failure mechanism.
  Citation: International Journal of Protective Structures
  PubDate: 2020-05-07T05:35:06Z
  DOI: 10.1177/2041419620917689