Pub Date : 2022-05-26DOI: 10.1177/20414196221092475
Y. Vayig, Z. Rosenberg, D. Ornai
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.
{"title":"More on the penetration of spherical-nosed rigid projectiles into metallic targets","authors":"Y. Vayig, Z. Rosenberg, D. Ornai","doi":"10.1177/20414196221092475","DOIUrl":"https://doi.org/10.1177/20414196221092475","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"122 - 131"},"PeriodicalIF":2.0,"publicationDate":"2022-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45997400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-25DOI: 10.1177/20414196221095252
Emily M. Johnson, N. Grahl, M. Langenderfer, David Doucet, Joseph Schott, K. Williams, B. Rutter, Catherine E. Johnson
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.
{"title":"An experimental and simulated investigation into the validity of unrestricted blast wave scaling models when applied to transonic flow in complex tunnel environments","authors":"Emily M. Johnson, N. Grahl, M. Langenderfer, David Doucet, Joseph Schott, K. Williams, B. Rutter, Catherine E. Johnson","doi":"10.1177/20414196221095252","DOIUrl":"https://doi.org/10.1177/20414196221095252","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"165 - 220"},"PeriodicalIF":2.0,"publicationDate":"2022-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41632756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-25DOI: 10.1177/20414196221095249
Gopinath Kanakadandi, V. Narayanamurthy, Y. Rao
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 ( P · ) , score depth and width-to-disc thickness ratio (t 1 /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.
{"title":"Deformation and failure of thin domed-scored metallic disc under impulsive loading","authors":"Gopinath Kanakadandi, V. Narayanamurthy, Y. Rao","doi":"10.1177/20414196221095249","DOIUrl":"https://doi.org/10.1177/20414196221095249","url":null,"abstract":"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 ( P · ) , score depth and width-to-disc thickness ratio (t 1 /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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"185 - 220"},"PeriodicalIF":2.0,"publicationDate":"2022-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45452899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-25DOI: 10.1177/20414196221095250
M. Islam, T. Ahmed, Sheikh Muhammad Najmul Imam, Muhammad Ifaz, H. Islam
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.
钢易受腐蚀，需要大量的混凝土保护层，这会增加自重和成本。因此，需要一种替代传统钢筋的方法。织物增强混凝土（TRC）是一种以织物材料为增强材料，以细粒混凝土为基体的良好复合材料。本研究比较了具有不同织物增强物的不同TRC在弯曲和冲击载荷下的性能。使用了四种类型的纺织品——玻璃（GT）、方形镀锌铁（SGIT）、斜向镀锌铁（DGIT）和碳（CT）。所有四种类型的纺织品都用于制备400 x 50 x12 mm织物增强砂浆（TRM），并测试拉伸强度性能。本研究采用三点弯曲和落锤冲击法对TRC面板和板材样品进行了测试。纺织品的单轴拉伸强度测试表明，CT可以承受比SGIT高约2.3倍的拉伸载荷。然而，在TRM的情况下，它们的拉伸负载能力几乎相似，其中SGIT纺织品显示出约30%的高延展性。TRC面板的弯曲试验表明，随着25 即使在加强层的数量保持不变的情况下，厚度也为mm。随着厚度的增加，SGIT纺织品表现出更好的性能。TRC板的落锤冲击试验表明，对于不同厚度，CT织物板的冲击能量吸收比SGIT板高出两倍。本研究总结了CT显示出比SGIT更好的整体性能。
{"title":"Flexural and impact behavior of textile reinforced concrete panel","authors":"M. Islam, T. Ahmed, Sheikh Muhammad Najmul Imam, Muhammad Ifaz, H. Islam","doi":"10.1177/20414196221095250","DOIUrl":"https://doi.org/10.1177/20414196221095250","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"221 - 241"},"PeriodicalIF":2.0,"publicationDate":"2022-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47985428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-24DOI: 10.1177/20414196221096699
J. J. Pannell, S. Rigby, G. Panoutsos
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.
{"title":"Application of transfer learning for the prediction of blast impulse","authors":"J. J. Pannell, S. Rigby, G. Panoutsos","doi":"10.1177/20414196221096699","DOIUrl":"https://doi.org/10.1177/20414196221096699","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"242 - 262"},"PeriodicalIF":2.0,"publicationDate":"2022-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41721773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-23DOI: 10.1177/20414196221104146
Y. Shi, Shaozeng Liu, Zhongxian Li, Yang Ding
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.
{"title":"Review on quick safety assessment of building structures in complex urban environment after extreme explosion events","authors":"Y. Shi, Shaozeng Liu, Zhongxian Li, Yang Ding","doi":"10.1177/20414196221104146","DOIUrl":"https://doi.org/10.1177/20414196221104146","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"438 - 458"},"PeriodicalIF":2.0,"publicationDate":"2022-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48534615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.1177/20414196221085720
Adam A Dennis, D. Smyl, Chris G. Stirling, S. Rigby
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.
{"title":"A branching algorithm to reduce computational time of batch models: Application for blast analyses","authors":"Adam A Dennis, D. Smyl, Chris G. Stirling, S. Rigby","doi":"10.1177/20414196221085720","DOIUrl":"https://doi.org/10.1177/20414196221085720","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"135 - 167"},"PeriodicalIF":2.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47653716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-11DOI: 10.1177/20414196211062927
Gajewski Tomasz, Peksa Piotr, Studziński Robert, Malendowski Michał, Sumelka Wojciech, Sielicki W Piotr
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.
{"title":"Application verification of blast mitigation through the use of thuja hedges","authors":"Gajewski Tomasz, Peksa Piotr, Studziński Robert, Malendowski Michał, Sumelka Wojciech, Sielicki W Piotr","doi":"10.1177/20414196211062927","DOIUrl":"https://doi.org/10.1177/20414196211062927","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"13 1","pages":"363 - 378"},"PeriodicalIF":2.0,"publicationDate":"2022-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44579734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-11DOI: 10.1177/20414196221095251
S. Anas, M. Shariq, M. Alam, M. Umair
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.
{"title":"Evaluation of critical damage location of contact blast on conventionally reinforced one-way square concrete slab applying CEL-FEM blast modeling technique","authors":"S. Anas, M. Shariq, M. Alam, M. Umair","doi":"10.1177/20414196221095251","DOIUrl":"https://doi.org/10.1177/20414196221095251","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"13 1","pages":"672 - 715"},"PeriodicalIF":2.0,"publicationDate":"2022-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44740615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-03DOI: 10.1177/20414196221095883
Tae Kwang Yoo
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.
{"title":"Study on physical behaviors according to element formulations of ballistic impact simulation models","authors":"Tae Kwang Yoo","doi":"10.1177/20414196221095883","DOIUrl":"https://doi.org/10.1177/20414196221095883","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"13 1","pages":"656 - 671"},"PeriodicalIF":2.0,"publicationDate":"2022-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44512952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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