Pub Date : 2023-09-01DOI: 10.1177/20414196221104143
S. Anas, Meraj Alam, M. Umair
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.
{"title":"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","authors":"S. Anas, Meraj Alam, M. Umair","doi":"10.1177/20414196221104143","DOIUrl":"https://doi.org/10.1177/20414196221104143","url":null,"abstract":"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.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"14 1","pages":"299 - 334"},"PeriodicalIF":2.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45306871","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 : 2023-08-30DOI: 10.1177/20414196231198259
L. Lomazzi, David Morin, F. Cadini, A. Manes, V. Aune
Blast events within urban areas in recent decades necessitate that protective design is no longer reserved for military installations. Modern civil infrastructure composed of light-weight, flexible materials has introduced the consideration of fluid-structure interaction (FSI) effects in blast-resistant design. While the action of blast loading on massive, rigid structures in military fortifications is well established, assessment of FSI effects is, at present, only possible through computationally expensive coupled simulations. In this study, a data-driven approach is proposed to assist in the identification of the blast-loading scenarios for which FSI effects play a significant role. A series of feed-forward deep neural networks (DNNs) were designed to learn weighted associations between characteristics of uncoupled simulations and a correction factor determined by the out-of-plane displacement arising from FSI effects in corresponding coupled simulations. The DNNs were trained, validated and tested on simulation results of various blast-loading conditions and material parameters for metallic target plates. DNNs exposed to mass-per-unit-area, identified as an influential factor in quantifying FSI effects, generalised well across a range of unseen data. The explainability approach was used to highlight the driving parameters of FSI effect predictions which further evidenced the findings. The ability to provide quick assessments of FSI influence may serve to identify opportunities to exploit FSI effects for improved structural integrity of light-weight protective structures where the use of uncoupled numerical models is currently limited.
{"title":"Deep learning-based analysis to identify fluid-structure interaction effects during the response of blast-loaded plates","authors":"L. Lomazzi, David Morin, F. Cadini, A. Manes, V. Aune","doi":"10.1177/20414196231198259","DOIUrl":"https://doi.org/10.1177/20414196231198259","url":null,"abstract":"Blast events within urban areas in recent decades necessitate that protective design is no longer reserved for military installations. Modern civil infrastructure composed of light-weight, flexible materials has introduced the consideration of fluid-structure interaction (FSI) effects in blast-resistant design. While the action of blast loading on massive, rigid structures in military fortifications is well established, assessment of FSI effects is, at present, only possible through computationally expensive coupled simulations. In this study, a data-driven approach is proposed to assist in the identification of the blast-loading scenarios for which FSI effects play a significant role. A series of feed-forward deep neural networks (DNNs) were designed to learn weighted associations between characteristics of uncoupled simulations and a correction factor determined by the out-of-plane displacement arising from FSI effects in corresponding coupled simulations. The DNNs were trained, validated and tested on simulation results of various blast-loading conditions and material parameters for metallic target plates. DNNs exposed to mass-per-unit-area, identified as an influential factor in quantifying FSI effects, generalised well across a range of unseen data. The explainability approach was used to highlight the driving parameters of FSI effect predictions which further evidenced the findings. The ability to provide quick assessments of FSI influence may serve to identify opportunities to exploit FSI effects for improved structural integrity of light-weight protective structures where the use of uncoupled numerical models is currently limited.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43165266","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 : 2023-08-30DOI: 10.1177/20414196231198128
Hao Qin, M. Stewart
Primary fragmentation from detonation of high-explosive metal-cased munitions imposes significant risks to the safety of related personnel and the public. Barricades or other protective structures are commonly used to stop fragments and reduce casualty risks caused by detonated munitions when a sufficient safety distance cannot be guaranteed. This study aims to provide decision support for the positioning of barricades that can reasonably mitigate primary fragmentation hazards from the detonation of large calibre munitions using a probabilistic risk assessment approach. This approach enables a stochastic characterization of fragment ejections, stacking effects, fragment trajectories, human vulnerability and fragment hazard reduction by barricade. In a case study, the assessments of casualty risks and effectiveness of barricades were conducted for a single and a pallet of 155 mm projectiles. It was found that barricades with heights exceeding the height of munitions can significantly reduce the hazardous fragment densities and casualty risks beyond the barricade. The benefit of increasing the barricade height becomes marginal when it exceeds the height of munitions.
{"title":"Mitigating casualty risks from primary fragmentation hazards","authors":"Hao Qin, M. Stewart","doi":"10.1177/20414196231198128","DOIUrl":"https://doi.org/10.1177/20414196231198128","url":null,"abstract":"Primary fragmentation from detonation of high-explosive metal-cased munitions imposes significant risks to the safety of related personnel and the public. Barricades or other protective structures are commonly used to stop fragments and reduce casualty risks caused by detonated munitions when a sufficient safety distance cannot be guaranteed. This study aims to provide decision support for the positioning of barricades that can reasonably mitigate primary fragmentation hazards from the detonation of large calibre munitions using a probabilistic risk assessment approach. This approach enables a stochastic characterization of fragment ejections, stacking effects, fragment trajectories, human vulnerability and fragment hazard reduction by barricade. In a case study, the assessments of casualty risks and effectiveness of barricades were conducted for a single and a pallet of 155 mm projectiles. It was found that barricades with heights exceeding the height of munitions can significantly reduce the hazardous fragment densities and casualty risks beyond the barricade. The benefit of increasing the barricade height becomes marginal when it exceeds the height of munitions.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46775873","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 : 2023-08-01DOI: 10.1177/20414196231192676
Omar Ghareeb Alshammari, Obed Samuelraj Isaac, S. Clarke, S. Rigby
The mechanics of downstream blast wave attenuation caused by interaction with obstacles arranged into a pre-fractal shape based on the Sierpinski carpet was numerically investigated using a high-fidelity CFD solver. The blast mitigation was qualitatively and quantitatively assessed for four pre-fractal iterations at three different scaled distances ( Z = 1.87, 2.24, 2.99 m/kg1/3). Mitigation was seen to occur in zones associated with the location of destructive wave interference patterns in the downstream region. Crucially, these zones were found to widen spatially with increasing pre-fractal iteration, and strong shock-shock interactions that result in load amplification, commonly encountered in downstream regions of a solitary block-like obstacle, were not observed for the more fractal-like obstacles. The mechanisms of attenuation are explored in terms of wave impedance. It is found that pre-fractals reduce wave transmission in the downstream, increase reflection of the blast wave, and enhance trapping within the confines of the pre-fractal obstacle, dramatically changing the directionality and hence the strength of the transmitted wave. Reductions in peak pressure of up to 60% and peak specific impulse of up to 40% were recorded for the highest iteration pre-fractal, that is, obstacles that most closely represent a true fractal, thereby highlighting the effectiveness of such shapes for protective structure design for improved blast mitigation.
{"title":"Numerical modelling of blast mitigation of pre-fractal obstacles","authors":"Omar Ghareeb Alshammari, Obed Samuelraj Isaac, S. Clarke, S. Rigby","doi":"10.1177/20414196231192676","DOIUrl":"https://doi.org/10.1177/20414196231192676","url":null,"abstract":"The mechanics of downstream blast wave attenuation caused by interaction with obstacles arranged into a pre-fractal shape based on the Sierpinski carpet was numerically investigated using a high-fidelity CFD solver. The blast mitigation was qualitatively and quantitatively assessed for four pre-fractal iterations at three different scaled distances ( Z = 1.87, 2.24, 2.99 m/kg1/3). Mitigation was seen to occur in zones associated with the location of destructive wave interference patterns in the downstream region. Crucially, these zones were found to widen spatially with increasing pre-fractal iteration, and strong shock-shock interactions that result in load amplification, commonly encountered in downstream regions of a solitary block-like obstacle, were not observed for the more fractal-like obstacles. The mechanisms of attenuation are explored in terms of wave impedance. It is found that pre-fractals reduce wave transmission in the downstream, increase reflection of the blast wave, and enhance trapping within the confines of the pre-fractal obstacle, dramatically changing the directionality and hence the strength of the transmitted wave. Reductions in peak pressure of up to 60% and peak specific impulse of up to 40% were recorded for the highest iteration pre-fractal, that is, obstacles that most closely represent a true fractal, thereby highlighting the effectiveness of such shapes for protective structure design for improved blast mitigation.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47529802","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 : 2023-07-14DOI: 10.1177/20414196231184585
S. Jafari, A. Alavi Nia
In this research, the ballistic performance of ceramic-polyurea-aluminum composite targets under the impact of flat-nose projectile was investigated for different thicknesses. The relevant experiments were designed based on the thickness of the layers and the effect of their configuration was explored. Experimental tests were carried out using two types of gas gun devices with different calibers. Residual velocity of the projectile was extracted using ls-dyna software for all targets and compared with the experimental data and after validation, the ballistic limit velocity was extracted. Taguchi method was used to design experiments and optimization and ballistic limit velocity, surface density, and strength-to-weight ratio were considered as objective functions. Moreover, the residual velocity of the projectile, damage mechanism of layers, the diameter of the hole at the back layer, central displacement of the back layer, absorbed energy, and changes in the projectile velocity were also investigated. Based on the numerical results, ceramic had the greatest effect on reducing the velocity of the projectile (approximately between 55 and 65%). Strength-to-weight ratio and armor weight were considered as two objective functions in the optimization. The effect of each of the armor materials on the target functions was investigated. According to the results, ceramic had the greatest effect on increasing the strength-to-weight ratio (about 83.88%), and polyurea had the least effect (about 14.09%) on increasing the total weight of the armor.
{"title":"Investigating the effect of ceramic-polyurea-aluminum layers on ballistic performance of composite target","authors":"S. Jafari, A. Alavi Nia","doi":"10.1177/20414196231184585","DOIUrl":"https://doi.org/10.1177/20414196231184585","url":null,"abstract":"In this research, the ballistic performance of ceramic-polyurea-aluminum composite targets under the impact of flat-nose projectile was investigated for different thicknesses. The relevant experiments were designed based on the thickness of the layers and the effect of their configuration was explored. Experimental tests were carried out using two types of gas gun devices with different calibers. Residual velocity of the projectile was extracted using ls-dyna software for all targets and compared with the experimental data and after validation, the ballistic limit velocity was extracted. Taguchi method was used to design experiments and optimization and ballistic limit velocity, surface density, and strength-to-weight ratio were considered as objective functions. Moreover, the residual velocity of the projectile, damage mechanism of layers, the diameter of the hole at the back layer, central displacement of the back layer, absorbed energy, and changes in the projectile velocity were also investigated. Based on the numerical results, ceramic had the greatest effect on reducing the velocity of the projectile (approximately between 55 and 65%). Strength-to-weight ratio and armor weight were considered as two objective functions in the optimization. The effect of each of the armor materials on the target functions was investigated. According to the results, ceramic had the greatest effect on increasing the strength-to-weight ratio (about 83.88%), and polyurea had the least effect (about 14.09%) on increasing the total weight of the armor.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42998117","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 : 2023-07-04DOI: 10.1177/20414196231187004
A. Praveen Kumar, Ma Quanjin
Light weight cellular structures have gained extensive attention in the impact energy absorption applications owing to their superior specific strength and excellent crashworthiness characteristics. The main objective of the present research work is to utilize this benefit to tailor and to improve the structural design and material type of cellular structures for crashworthiness applications. Cubic structures with four different types of design patterns such as concave, convex, hyperbola, and hexagon were proposed and fabricated through three-dimensional (3D) printing technique. Four polymeric filament materials such as Poly lactic acid (PLA), Acrylonitrile butadiene styrene (ABS), PLA mixed carbon fiber (PLA/CF), and Polyethylene terephthalate glycol (PETG), mixed carbon fiber (PETG/CF) were utilized. Accordingly, the compression tests were performed on the fabricated cellular cubic structures under quasi-static loading to examine the effect of design pattern, and material types on the compressive behavior and energy absorbing characteristics. The results revealed that the convex design pattern of 3D printed PETG/CF cubic structure showed the significant energy absorbing characteristics compared to the other three design patterns. It is emphasized that the proposed 3D printed cubic cellular structures have great prospective to substitute the traditional energy absorbing structures in automotive vehicles and high speed trains.
{"title":"Quasi-static compressive performance of 3D printed polymer composite cellular cubic structures-An experimental study","authors":"A. Praveen Kumar, Ma Quanjin","doi":"10.1177/20414196231187004","DOIUrl":"https://doi.org/10.1177/20414196231187004","url":null,"abstract":"Light weight cellular structures have gained extensive attention in the impact energy absorption applications owing to their superior specific strength and excellent crashworthiness characteristics. The main objective of the present research work is to utilize this benefit to tailor and to improve the structural design and material type of cellular structures for crashworthiness applications. Cubic structures with four different types of design patterns such as concave, convex, hyperbola, and hexagon were proposed and fabricated through three-dimensional (3D) printing technique. Four polymeric filament materials such as Poly lactic acid (PLA), Acrylonitrile butadiene styrene (ABS), PLA mixed carbon fiber (PLA/CF), and Polyethylene terephthalate glycol (PETG), mixed carbon fiber (PETG/CF) were utilized. Accordingly, the compression tests were performed on the fabricated cellular cubic structures under quasi-static loading to examine the effect of design pattern, and material types on the compressive behavior and energy absorbing characteristics. The results revealed that the convex design pattern of 3D printed PETG/CF cubic structure showed the significant energy absorbing characteristics compared to the other three design patterns. It is emphasized that the proposed 3D printed cubic cellular structures have great prospective to substitute the traditional energy absorbing structures in automotive vehicles and high speed trains.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42991636","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 : 2023-06-30DOI: 10.1177/20414196231187003
Vimal Kumar, M. Iqbal, AK Mittal
An experimental and numerical study has been performed to explore the performance of one-way pretensioned concrete plates against impact loading. The impact resistance, experimental results and damage within the pretensioned concrete have been compared with the non-pretensioned concrete. The plate specimens of concrete grades M40 and M60 have been pretensioned to prestress level 10 and 20% of the compressive strength of the concrete. While, all the tendons employed in the non-pretensioned concrete were kept unstressed. The plates were struck at the mid-span by a steel mass (242.85 kg) dropped from 0.5 to 1.0 m heights. The numerical simulations have been executed using explicit finite element code considering the Holmquist–Johnson–Cook (HJC) and the metal plasticity model for concrete and steel, correspondingly. The performance of the plates is governed by the grade of concrete, impact energy and level of the prestress within the concrete. The induced prestress within the concrete enhanced the stiffness and, consequently, the impact resistance of the pretensioned concrete plates. The pretensioned concrete hence witnessed increased impact force and reduced deflection by 18.1% and 11.0%, correspondingly, compared to the non-pretensioned concrete. The splitting and punching crack within the plates became pronounced once the drop height increased from 0.5 m to 1.0 m. The simulations have estimated the peak impact force and reaction within 19.7% and 15.5% deviation, respectively. The displacement and energy absorption have been calculated using an analytical methodology closely correlated with the actual results within 18% and 14% deviation, respectively. Further, the simulations performed on two-way pretensioned concrete have shown improved performance of the plates witnessing no splitting crack and uniform crack distribution compared to one-way pretensioned concrete.
{"title":"Influence of prestressing force on performance of concrete plates under impact loading","authors":"Vimal Kumar, M. Iqbal, AK Mittal","doi":"10.1177/20414196231187003","DOIUrl":"https://doi.org/10.1177/20414196231187003","url":null,"abstract":"An experimental and numerical study has been performed to explore the performance of one-way pretensioned concrete plates against impact loading. The impact resistance, experimental results and damage within the pretensioned concrete have been compared with the non-pretensioned concrete. The plate specimens of concrete grades M40 and M60 have been pretensioned to prestress level 10 and 20% of the compressive strength of the concrete. While, all the tendons employed in the non-pretensioned concrete were kept unstressed. The plates were struck at the mid-span by a steel mass (242.85 kg) dropped from 0.5 to 1.0 m heights. The numerical simulations have been executed using explicit finite element code considering the Holmquist–Johnson–Cook (HJC) and the metal plasticity model for concrete and steel, correspondingly. The performance of the plates is governed by the grade of concrete, impact energy and level of the prestress within the concrete. The induced prestress within the concrete enhanced the stiffness and, consequently, the impact resistance of the pretensioned concrete plates. The pretensioned concrete hence witnessed increased impact force and reduced deflection by 18.1% and 11.0%, correspondingly, compared to the non-pretensioned concrete. The splitting and punching crack within the plates became pronounced once the drop height increased from 0.5 m to 1.0 m. The simulations have estimated the peak impact force and reaction within 19.7% and 15.5% deviation, respectively. The displacement and energy absorption have been calculated using an analytical methodology closely correlated with the actual results within 18% and 14% deviation, respectively. Further, the simulations performed on two-way pretensioned concrete have shown improved performance of the plates witnessing no splitting crack and uniform crack distribution compared to one-way pretensioned concrete.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43426004","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 : 2023-06-29DOI: 10.1177/20414196231183006
G. Gomes, V. Lúcio, C. Cismaşiu
Shock absorbers have been widely used in the automotive and aeronautical industries for many years. Inspired on these devices, the paper presents an analytical and numerical assessment of a high performance protective system for building structures against blast loads, which is composed of a shielding element connected to the main structure, at the floor levels, through ductile Energy Absorbing Connectors (EACs). The EACs exploit the external tube inversion mechanism to absorb a significant part of the imparted kinetic energy from the blast wave. While the system prototype has been developed in laboratory, it was characterized and tested in a full-scale blast testing campaign. A validated finite element model was used next to analyze its performance in a more demanding design scenario. The introduction of EACs notably reduces the peak horizontal loads and the kinetic energy transferred to the protected structure, being expected a significant reduction of the stresses in the supporting vertical elements, in addition to the protection of structural and non-structural members. These results encourage further studies of the presented protective system that can be potentially employed for a large variety of blast threat scenarios, especially when increasing the stand-off is not a possible/viable option and sensitive facilities have to be protected.
{"title":"Development of a high-performance blast energy-absorbing system for building structures","authors":"G. Gomes, V. Lúcio, C. Cismaşiu","doi":"10.1177/20414196231183006","DOIUrl":"https://doi.org/10.1177/20414196231183006","url":null,"abstract":"Shock absorbers have been widely used in the automotive and aeronautical industries for many years. Inspired on these devices, the paper presents an analytical and numerical assessment of a high performance protective system for building structures against blast loads, which is composed of a shielding element connected to the main structure, at the floor levels, through ductile Energy Absorbing Connectors (EACs). The EACs exploit the external tube inversion mechanism to absorb a significant part of the imparted kinetic energy from the blast wave. While the system prototype has been developed in laboratory, it was characterized and tested in a full-scale blast testing campaign. A validated finite element model was used next to analyze its performance in a more demanding design scenario. The introduction of EACs notably reduces the peak horizontal loads and the kinetic energy transferred to the protected structure, being expected a significant reduction of the stresses in the supporting vertical elements, in addition to the protection of structural and non-structural members. These results encourage further studies of the presented protective system that can be potentially employed for a large variety of blast threat scenarios, especially when increasing the stand-off is not a possible/viable option and sensitive facilities have to be protected.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43193124","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 : 2023-06-25DOI: 10.1177/20414196231184581
Matthew R. Kirchner, Shawnasie R Kirchner, Adam A Dennis, S. Rigby
Mathematical analysis of blast pressures has typically involved the empirical fitting of parametric models, which assumes a specific function shape. In reality, the true shape of the blast pressure is unknown and may lack a parametric form, particularly in the negative phase following arrival of the secondary shock. In this work, we develop a non-parametric (NP) representation that makes few assumptions and relies on the observed experimental data to fit a unique and previously unknown model. This differs from traditional approaches by not arbitrarily selecting a single, restrictive class of functions and estimating a minimal set of parameters, but rather estimating the underlying function class for which the blast pressure is generated; learning the model directly from the observed data. The method was applied to experimental blast measurements and the NP estimates matched the experimental data with a high degree of accuracy, both qualitatively and quantitatively. The NP approach was shown to significantly outperform other commonly used approaches, near-perfectly track the entire pressure and specific impulse history and predicting experimental peak specific impulse to within ±0.5% in all cases (compared to ±5.0% for a trained artificial neural network (ANN) and ±7.5% for the UFC semi-empirical approach). The NP approach predicts experimental net specific impulses (positive and negative phases combined) with a maximum variation of 2.7%, compared to maximum variations of −116% and 55% for the UFC and ANN approaches, respectively. Since the framework is probabilistic in nature, it can naturally account for random noise in sensor measurements, which are typically more pronounced in blast experiments than many other machine learning applications.
{"title":"Non-parametric characterization of blast loads","authors":"Matthew R. Kirchner, Shawnasie R Kirchner, Adam A Dennis, S. Rigby","doi":"10.1177/20414196231184581","DOIUrl":"https://doi.org/10.1177/20414196231184581","url":null,"abstract":"Mathematical analysis of blast pressures has typically involved the empirical fitting of parametric models, which assumes a specific function shape. In reality, the true shape of the blast pressure is unknown and may lack a parametric form, particularly in the negative phase following arrival of the secondary shock. In this work, we develop a non-parametric (NP) representation that makes few assumptions and relies on the observed experimental data to fit a unique and previously unknown model. This differs from traditional approaches by not arbitrarily selecting a single, restrictive class of functions and estimating a minimal set of parameters, but rather estimating the underlying function class for which the blast pressure is generated; learning the model directly from the observed data. The method was applied to experimental blast measurements and the NP estimates matched the experimental data with a high degree of accuracy, both qualitatively and quantitatively. The NP approach was shown to significantly outperform other commonly used approaches, near-perfectly track the entire pressure and specific impulse history and predicting experimental peak specific impulse to within ±0.5% in all cases (compared to ±5.0% for a trained artificial neural network (ANN) and ±7.5% for the UFC semi-empirical approach). The NP approach predicts experimental net specific impulses (positive and negative phases combined) with a maximum variation of 2.7%, compared to maximum variations of −116% and 55% for the UFC and ANN approaches, respectively. Since the framework is probabilistic in nature, it can naturally account for random noise in sensor measurements, which are typically more pronounced in blast experiments than many other machine learning applications.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49057913","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 : 2023-06-01DOI: 10.1177/20414196231175979
Hugo Bento Rebelo, Beatriz Assunção, Chiara Bedon, F. Amarante dos Santos
This paper is focused on the study of innovative bi-stable supports to improve the impact performance of point-fixed glass panels, for typical use in facades. To mitigate the effects of impact and reduce potential risk for people, the introduction of innovative, bi-stable, mitigation devices between the fixing system and the primary building structure is addressed. The proposed dissipative system is able to control and minimise the input force which is transmitted to the primary building, controlling the damage around the supports and preventing the detachment of the glass panels. Based on LS-Dyna Finite-Element (FE) models, the proposed protection system is designed to have a snap-through behaviour under impact. The performance of the system is quantified for two different glazing systems, which are numerically investigated under various impact configurations.
{"title":"Exploratory study on the use of bi-stable supports for the impact protection of point-fixed glazing systems","authors":"Hugo Bento Rebelo, Beatriz Assunção, Chiara Bedon, F. Amarante dos Santos","doi":"10.1177/20414196231175979","DOIUrl":"https://doi.org/10.1177/20414196231175979","url":null,"abstract":"This paper is focused on the study of innovative bi-stable supports to improve the impact performance of point-fixed glass panels, for typical use in facades. To mitigate the effects of impact and reduce potential risk for people, the introduction of innovative, bi-stable, mitigation devices between the fixing system and the primary building structure is addressed. The proposed dissipative system is able to control and minimise the input force which is transmitted to the primary building, controlling the damage around the supports and preventing the detachment of the glass panels. Based on LS-Dyna Finite-Element (FE) models, the proposed protection system is designed to have a snap-through behaviour under impact. The performance of the system is quantified for two different glazing systems, which are numerically investigated under various impact configurations.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41427288","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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