Pub Date : 2024-01-08DOI: 10.1177/20414196241226725
Qian Wang, Emre Palta, H. Fang
Cable barriers are flexible barrier systems that are commonly used as median barriers in the United States for their general effectiveness and low installation and maintenance costs. The current cable median barrier (CMB) adopted by the North Carolina Department of Transportation was previously evaluated on flat terrain and found to satisfy the requirements of the National Cooperative Highway Research Program Report 350. Under in-service conditions (i.e., on a sloped median), the current CMB failed to stop small passenger cars in many incidents. The new roadside safety standard, Manual for Assessing Safety Hardware (MASH), recommends that CMBs be tested and/or evaluated on sloped medians. However, conducting full-scale crash tests on sloped median is extremely difficult and few experimental studies exist. In this study, finite element simulations were used to evaluate the performance of the current CMB design on a 6H:1V sloped median under MASH Test Level 3 conditions. To address the issue of vehicle underriding on the current CMB, two retrofit designs were developed and also evaluated on the sloped median. Two MASH compliant vehicles, a 1996 Dodge Neon and a 2006 Ford F250, were used to evaluate all three CMBs from both frontside and backside and with two initial impact points. The MASH exit-box criterion, MASH Evaluation criteria A, D, and F, vehicular responses, exit angles, and residual velocities were used to evaluate the CMB performance for structural adequacy, occupant risk, and post-impact trajectories. The simulation results showed that one of the retrofit designs could improve the CMB performance on a sloped median at MASH Test Level 3 conditions.
{"title":"Numerical modeling and simulation of cable barriers under vehicular impacts on a sloped median","authors":"Qian Wang, Emre Palta, H. Fang","doi":"10.1177/20414196241226725","DOIUrl":"https://doi.org/10.1177/20414196241226725","url":null,"abstract":"Cable barriers are flexible barrier systems that are commonly used as median barriers in the United States for their general effectiveness and low installation and maintenance costs. The current cable median barrier (CMB) adopted by the North Carolina Department of Transportation was previously evaluated on flat terrain and found to satisfy the requirements of the National Cooperative Highway Research Program Report 350. Under in-service conditions (i.e., on a sloped median), the current CMB failed to stop small passenger cars in many incidents. The new roadside safety standard, Manual for Assessing Safety Hardware (MASH), recommends that CMBs be tested and/or evaluated on sloped medians. However, conducting full-scale crash tests on sloped median is extremely difficult and few experimental studies exist. In this study, finite element simulations were used to evaluate the performance of the current CMB design on a 6H:1V sloped median under MASH Test Level 3 conditions. To address the issue of vehicle underriding on the current CMB, two retrofit designs were developed and also evaluated on the sloped median. Two MASH compliant vehicles, a 1996 Dodge Neon and a 2006 Ford F250, were used to evaluate all three CMBs from both frontside and backside and with two initial impact points. The MASH exit-box criterion, MASH Evaluation criteria A, D, and F, vehicular responses, exit angles, and residual velocities were used to evaluate the CMB performance for structural adequacy, occupant risk, and post-impact trajectories. The simulation results showed that one of the retrofit designs could improve the CMB performance on a sloped median at MASH Test Level 3 conditions.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"46 5","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446204","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 : 2024-01-04DOI: 10.1177/20414196231225812
M. Hajizadeh, Mojtaba Yazdani, Hosein Khodarahmi
This study examined the behavior and energy absorption of open-cell aluminum foam under different loading conditions. The foam was made by infiltration, a low-cost method that produced a uniform pore distribution. The foam was compressed using two machines with varying impact velocities and weights. The stress–strain and energy absorption curves of the foam were measured and analyzed. The results showed that the strain rate and the impact weight affected the compressive properties and energy absorption of the foam. The strain rate up to 264 s−1 with constant mass did not affect the plateau stress, which was the constant stress in the plastic region. However, at 264 s−1, increasing the impact weight increased the plateau stress and the energy absorption of the foam, which showed that the strain rate sensitivity depended on the impact inertia. The study revealed the dynamic characteristics of open-cell aluminum foam made by infiltration and provided insights for its use in impact protection. The study also showed that infiltration was a reliable and consistent method for making open-cell aluminum foam. The study highlighted the important roles of plateau stress and hardening effect in influencing the energy absorption of the foam under dynamic loading. The study suggested that future studies should consider the impact inertia as a parameter that affects the strain rate sensitivity of the foam.
{"title":"Experimental study of the low-velocity impact behavior of open-cell aluminum foam made by the infiltration method","authors":"M. Hajizadeh, Mojtaba Yazdani, Hosein Khodarahmi","doi":"10.1177/20414196231225812","DOIUrl":"https://doi.org/10.1177/20414196231225812","url":null,"abstract":"This study examined the behavior and energy absorption of open-cell aluminum foam under different loading conditions. The foam was made by infiltration, a low-cost method that produced a uniform pore distribution. The foam was compressed using two machines with varying impact velocities and weights. The stress–strain and energy absorption curves of the foam were measured and analyzed. The results showed that the strain rate and the impact weight affected the compressive properties and energy absorption of the foam. The strain rate up to 264 s−1 with constant mass did not affect the plateau stress, which was the constant stress in the plastic region. However, at 264 s−1, increasing the impact weight increased the plateau stress and the energy absorption of the foam, which showed that the strain rate sensitivity depended on the impact inertia. The study revealed the dynamic characteristics of open-cell aluminum foam made by infiltration and provided insights for its use in impact protection. The study also showed that infiltration was a reliable and consistent method for making open-cell aluminum foam. The study highlighted the important roles of plateau stress and hardening effect in influencing the energy absorption of the foam under dynamic loading. The study suggested that future studies should consider the impact inertia as a parameter that affects the strain rate sensitivity of the foam.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"58 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384895","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 : 2024-01-03DOI: 10.1177/20414196231226240
Pengzhi Yan, Yu Wang, Pengxian Fan, Mingyang Wang
The reliability of the absorbing layer is crucial for realizing protective engineering’s protection function. However, the typical wave-absorbing material, sand, is unable to fulfill its intended wave-absorbing function in areas with seasonally frozen soil. This is because the internal pores of the material become filled with ice and the particles freeze. To address this issue, alumina thin-walled hollow particles were chosen as a new wave-absorbing material. These particles can introduce the gas phase into the absorbing layer which is essential for attenuating the stress waves and its wave-absorbing capacity under freezing conditions was investigated by the split Hopkinson bar (SHPB) test. According to the test data, the alumina thin-walled hollow particles are less dense than sand and have a lower wave impedance, allowing them to reflect more incident energy. Moreover, these particles have a better capacity for dissipating the absorbed energy, as compared to sand. Under freezing circumstances, the average transmittance coefficient of alumina thin-walled hollow particles is only 21.95% to 49.30% of ordinary sand. Additionally, the particle size positively correlates with the capacity for wave-absorption. The capacity of alumina thin-walled hollow particles to shatter and release the gas phase under impact stress significantly increases the compressibility of the absorbing layer under freezing conditions, which accounts for their enhanced wave-absorbing effectiveness. The stress-strain curve specifically manifests as a smoother curve and a longer stage of plastic energy dissipation. Other than that, the dynamic deformation modulus of the material and peak stress is lower, while the peak strain is larger. The findings of this study provide a low-cost, high-reliability solution to the problem of frost damage in the absorbing layer in regions with seasonal freezing.
{"title":"Wave-absorbing performance of alumina thin-walled hollow particles under freezing condition","authors":"Pengzhi Yan, Yu Wang, Pengxian Fan, Mingyang Wang","doi":"10.1177/20414196231226240","DOIUrl":"https://doi.org/10.1177/20414196231226240","url":null,"abstract":"The reliability of the absorbing layer is crucial for realizing protective engineering’s protection function. However, the typical wave-absorbing material, sand, is unable to fulfill its intended wave-absorbing function in areas with seasonally frozen soil. This is because the internal pores of the material become filled with ice and the particles freeze. To address this issue, alumina thin-walled hollow particles were chosen as a new wave-absorbing material. These particles can introduce the gas phase into the absorbing layer which is essential for attenuating the stress waves and its wave-absorbing capacity under freezing conditions was investigated by the split Hopkinson bar (SHPB) test. According to the test data, the alumina thin-walled hollow particles are less dense than sand and have a lower wave impedance, allowing them to reflect more incident energy. Moreover, these particles have a better capacity for dissipating the absorbed energy, as compared to sand. Under freezing circumstances, the average transmittance coefficient of alumina thin-walled hollow particles is only 21.95% to 49.30% of ordinary sand. Additionally, the particle size positively correlates with the capacity for wave-absorption. The capacity of alumina thin-walled hollow particles to shatter and release the gas phase under impact stress significantly increases the compressibility of the absorbing layer under freezing conditions, which accounts for their enhanced wave-absorbing effectiveness. The stress-strain curve specifically manifests as a smoother curve and a longer stage of plastic energy dissipation. Other than that, the dynamic deformation modulus of the material and peak stress is lower, while the peak strain is larger. The findings of this study provide a low-cost, high-reliability solution to the problem of frost damage in the absorbing layer in regions with seasonal freezing.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"132 19","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387565","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 : 2024-01-02DOI: 10.1177/20414196231225813
Z. Rosenberg, Y. Vayig
We present an empirical relation for the penetration depths of rigid spheres impacting metallic targets at ordnance velocities. This relation was derived through 2D numerical simulations for various sphere/target pairs, that followed their penetration depths in terms of the impact velocity, the sphere/target density ratio, and the dynamic strength of the target. The numerically derived empirical relation is shown to account for test data from several publications.
{"title":"On the penetration of rigid spheres in metallic targets","authors":"Z. Rosenberg, Y. Vayig","doi":"10.1177/20414196231225813","DOIUrl":"https://doi.org/10.1177/20414196231225813","url":null,"abstract":"We present an empirical relation for the penetration depths of rigid spheres impacting metallic targets at ordnance velocities. This relation was derived through 2D numerical simulations for various sphere/target pairs, that followed their penetration depths in terms of the impact velocity, the sphere/target density ratio, and the dynamic strength of the target. The numerically derived empirical relation is shown to account for test data from several publications.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"114 4","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139391616","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 : 2023-12-11DOI: 10.1177/20414196231216751
C. Sauer, Jan Burtsche, Andreas Heine, Christoph Roller, Werner Riedel
In this work, we aim at improved characterization of target damage occurring as the result of projectile impact against ultra-high-performance concrete (UHPC). For this purpose, we present the results of high-velocity impact experiments with spherical steel projectiles and finite-thickness UHPC targets of approximately 115 MPa compressive cylinder strength in the impact velocity range from approximately 600 m/s to 1500 m/s. The data set obtained from these experiments includes residual projectile velocities as well as qualitative and quantitative information on damage. Quantitative damage information is mainly extracted from digital 3D post mortem targets, which are produced by 3D-scanning. For all damage quantities, a dependence on the impact velocity and the target thickness is discussed and used to provide possible explanations for the origin of the particular type of damage. The large data set presented in this work can constitute the basis for a comprehensive and quantitative verification and validation of analytical, empirical, and numerical models that describe the perforation of UHPC targets in the investigated impact velocity range.
{"title":"High-velocity impact experiments and quantitative damage evaluation for finite ultra-high-performance concrete targets","authors":"C. Sauer, Jan Burtsche, Andreas Heine, Christoph Roller, Werner Riedel","doi":"10.1177/20414196231216751","DOIUrl":"https://doi.org/10.1177/20414196231216751","url":null,"abstract":"In this work, we aim at improved characterization of target damage occurring as the result of projectile impact against ultra-high-performance concrete (UHPC). For this purpose, we present the results of high-velocity impact experiments with spherical steel projectiles and finite-thickness UHPC targets of approximately 115 MPa compressive cylinder strength in the impact velocity range from approximately 600 m/s to 1500 m/s. The data set obtained from these experiments includes residual projectile velocities as well as qualitative and quantitative information on damage. Quantitative damage information is mainly extracted from digital 3D post mortem targets, which are produced by 3D-scanning. For all damage quantities, a dependence on the impact velocity and the target thickness is discussed and used to provide possible explanations for the origin of the particular type of damage. The large data set presented in this work can constitute the basis for a comprehensive and quantitative verification and validation of analytical, empirical, and numerical models that describe the perforation of UHPC targets in the investigated impact velocity range.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"20 21-22","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138980284","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 : 2023-11-08DOI: 10.1177/20414196231212511
Masoud Abedini, Chunwei Zhang
Ultra-high performance fiber reinforced concrete (UHPFRC) is a cement-based composite material mixing with reactive powder and steel fibers. It is characterized by its high strength, high ductility, and high toughness and such characteristics enable its great potential in protective engineering against severe dynamic loads. In the current research, the dynamic performance of the concrete panel made with ultra-high performance fiber subjected to explosive loading was investigated. For this purpose, several concrete panel samples were considered and modeled in ABAQUS finite element software. The accuracy of the numerical model is verified by comparing the numerical simulation results with available testing data. First, the considered panel was modeled with normal concrete then it was modeled with UHPFRC concrete, and the effect of using this type of concrete on the behavior of concrete panels was investigated. After analyzing and examining the models, their behavior such as the degree of vulnerability, more vulnerable points and changes in the locations that occurred in each of the models were obtained and compared. The results demonstrate that the use of UHPFRC significantly improves the blast performance of RC panels by reducing maximum and residual displacements, enhancing damage tolerance, and increasing energy absorption. The results also indicate that the increase in the intensity of explosion has increased the base reaction force in all panels.
{"title":"Dynamic performance of ultra-high performance fiber-reinforced concrete panel exposed to explosive loading","authors":"Masoud Abedini, Chunwei Zhang","doi":"10.1177/20414196231212511","DOIUrl":"https://doi.org/10.1177/20414196231212511","url":null,"abstract":"Ultra-high performance fiber reinforced concrete (UHPFRC) is a cement-based composite material mixing with reactive powder and steel fibers. It is characterized by its high strength, high ductility, and high toughness and such characteristics enable its great potential in protective engineering against severe dynamic loads. In the current research, the dynamic performance of the concrete panel made with ultra-high performance fiber subjected to explosive loading was investigated. For this purpose, several concrete panel samples were considered and modeled in ABAQUS finite element software. The accuracy of the numerical model is verified by comparing the numerical simulation results with available testing data. First, the considered panel was modeled with normal concrete then it was modeled with UHPFRC concrete, and the effect of using this type of concrete on the behavior of concrete panels was investigated. After analyzing and examining the models, their behavior such as the degree of vulnerability, more vulnerable points and changes in the locations that occurred in each of the models were obtained and compared. The results demonstrate that the use of UHPFRC significantly improves the blast performance of RC panels by reducing maximum and residual displacements, enhancing damage tolerance, and increasing energy absorption. The results also indicate that the increase in the intensity of explosion has increased the base reaction force in all panels.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"26 40","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135390302","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 : 2023-09-27DOI: 10.1177/20414196231203402
Viet-Chinh Mai, Ngoc Quang Vu, Van Tu Nguyen, Xuan Dai Nguyen
Underground structures hold great significance in the infrastructure of modern society. With the rapid construction of such facilities, the possibility of explosions occurring inside these structures due to unforeseen accidents or deliberate acts cannot be ignored. Past catastrophic events have demonstrated the necessity of implementing anti-blast design for underground structures, particularly in vulnerable locations. This promotes investigations into the behavior of underground structures subjected to internal explosions. For the first time, a thorough simulation model is developed using the multi-material Coupled Eulerian–Lagrangian approach to examine a full-scale precast ultra-high performance concrete (UHPC) tunnel under internal explosion. The precast tunnel structure closely resembles real construction configurations. The simulation model takes into account the simultaneous interaction between the tunnel and the surrounding soil. The accuracy of the suggested simulation model is validated against experimental results. For various explosive charge weights, tunnel lining thicknesses, materials, and tunnel shapes, extensive parametric simulations are conducted. Results obtained highlighted UHPC's superiority as a substitute for conventional concrete due to its strong blast-resistant capacity. The findings from this research also shed light on the precast UHPC tunnel's structural response to an interior explosion, that can assist designers and managers choose the best design for blast protection.
{"title":"Dynamic analysis of precast ultra-high performance concrete tunnel under internal explosion","authors":"Viet-Chinh Mai, Ngoc Quang Vu, Van Tu Nguyen, Xuan Dai Nguyen","doi":"10.1177/20414196231203402","DOIUrl":"https://doi.org/10.1177/20414196231203402","url":null,"abstract":"Underground structures hold great significance in the infrastructure of modern society. With the rapid construction of such facilities, the possibility of explosions occurring inside these structures due to unforeseen accidents or deliberate acts cannot be ignored. Past catastrophic events have demonstrated the necessity of implementing anti-blast design for underground structures, particularly in vulnerable locations. This promotes investigations into the behavior of underground structures subjected to internal explosions. For the first time, a thorough simulation model is developed using the multi-material Coupled Eulerian–Lagrangian approach to examine a full-scale precast ultra-high performance concrete (UHPC) tunnel under internal explosion. The precast tunnel structure closely resembles real construction configurations. The simulation model takes into account the simultaneous interaction between the tunnel and the surrounding soil. The accuracy of the suggested simulation model is validated against experimental results. For various explosive charge weights, tunnel lining thicknesses, materials, and tunnel shapes, extensive parametric simulations are conducted. Results obtained highlighted UHPC's superiority as a substitute for conventional concrete due to its strong blast-resistant capacity. The findings from this research also shed light on the precast UHPC tunnel's structural response to an interior explosion, that can assist designers and managers choose the best design for blast protection.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135536147","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 : 2023-09-21DOI: 10.1177/20414196231197701
Andreia Caçoilo, Rodrigo Mourão, David Lecompte, Filipe Teixeira-Dias
The safety of both military personnel and equipment in unstable regions has for a long time been a major issue and concern. Protective shelters with multiple configurations have been widely used to meet safety requirements. Since military compounds are subjected to different types of threats, such as the detonation of improvised explosive devices (IED), a good understanding of the response of such shielding structures to blast waves is critical. A three-dimensional finite element (FE) model of a corner-entry ISO 20 ft container HESCO-Bastion survival shelter is developed, validated and tested under the external detonation of explosive charges. The FE model is validated against experimental data and used to investigate the protective performance of the shelter by considering several design-related parameters, such as charge location, roof extension, interior corridor dimensions and the effect of venting and its location. Results are discussed in terms of peak overpressure and maximum impulse at discrete locations around the container, and it is found that the shelter is the least efficient in mitigating the blast load propagation when the explosive material is at an angle of 45° to the entrance. Also, while the protective roof at the entrance plays a significant role in protecting the container from air-borne threats, it is observed that it contributes to higher pressure and impulse data within the shelter, for detonations at ground level, with impulse amplifications as high as 94% when fully covering the entrance area. Contrarily, varying the distance between the container and the HESCO-Bastions is found to have minimal impact on the impulse, while naturally decreasing the peak pressure for increasing distances. Venting (through openings) can lead to up to 95% reduction in the peak pressure, whilst not affecting the impulse.
{"title":"Layout considerations on compound survival shelters for blast mitigation: A finite-element approach","authors":"Andreia Caçoilo, Rodrigo Mourão, David Lecompte, Filipe Teixeira-Dias","doi":"10.1177/20414196231197701","DOIUrl":"https://doi.org/10.1177/20414196231197701","url":null,"abstract":"The safety of both military personnel and equipment in unstable regions has for a long time been a major issue and concern. Protective shelters with multiple configurations have been widely used to meet safety requirements. Since military compounds are subjected to different types of threats, such as the detonation of improvised explosive devices (IED), a good understanding of the response of such shielding structures to blast waves is critical. A three-dimensional finite element (FE) model of a corner-entry ISO 20 ft container HESCO-Bastion survival shelter is developed, validated and tested under the external detonation of explosive charges. The FE model is validated against experimental data and used to investigate the protective performance of the shelter by considering several design-related parameters, such as charge location, roof extension, interior corridor dimensions and the effect of venting and its location. Results are discussed in terms of peak overpressure and maximum impulse at discrete locations around the container, and it is found that the shelter is the least efficient in mitigating the blast load propagation when the explosive material is at an angle of 45° to the entrance. Also, while the protective roof at the entrance plays a significant role in protecting the container from air-borne threats, it is observed that it contributes to higher pressure and impulse data within the shelter, for detonations at ground level, with impulse amplifications as high as 94% when fully covering the entrance area. Contrarily, varying the distance between the container and the HESCO-Bastions is found to have minimal impact on the impulse, while naturally decreasing the peak pressure for increasing distances. Venting (through openings) can lead to up to 95% reduction in the peak pressure, whilst not affecting the impulse.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136129250","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 : 2023-09-08DOI: 10.1177/20414196231192680
Majid Noorian-Bidgoli, Behnam Behnia
When an engineering structure regarding a rock is affected by dynamic loads (due to the occurrence of natural hazards, such as earthquakes and landslides, or man-made hazards, such as explosions or impacts), correct prediction of changes in the strength behavior and deformability of the rock relative to its static state is necessary for reducing the damages and costs. On the other hand, rocks are always influenced by environmental conditions, such as temperature changes due to fire and weather during their lifetime, which should be considered when using them. In these cases, the mechanical behavior of the rock can usually be determined under different loading and environmental conditions using stress–strain curves. This study investigates rocks’ dynamic strength and deformability behavior at different loading rates and temperatures. For this purpose, 30 travertine rock samples from the Torshab mine, located in the Markazi province of Iran, were first heated up to 100°C, 200°C, 400°C, 800°C, and 1000°C (six temperatures), and then subjected under the impact pressure with different loading rates from (five) 11 m/s to 15 m/s using the split Hopkinson pressure bar test. Comparing the obtained dynamic stress–strain curve shows that at a constant loading rate, increasing the temperature, especially at higher temperatures, reduces the dynamic strength and increases the rock’s deformability. Moreover, in all cases, at a constant temperature, increasing the loading rate, especially at higher rates, increases the rock’s dynamic strength and deformability.
{"title":"Experimental evaluation of the thermal effect on dynamic behavior of travertine rock","authors":"Majid Noorian-Bidgoli, Behnam Behnia","doi":"10.1177/20414196231192680","DOIUrl":"https://doi.org/10.1177/20414196231192680","url":null,"abstract":"When an engineering structure regarding a rock is affected by dynamic loads (due to the occurrence of natural hazards, such as earthquakes and landslides, or man-made hazards, such as explosions or impacts), correct prediction of changes in the strength behavior and deformability of the rock relative to its static state is necessary for reducing the damages and costs. On the other hand, rocks are always influenced by environmental conditions, such as temperature changes due to fire and weather during their lifetime, which should be considered when using them. In these cases, the mechanical behavior of the rock can usually be determined under different loading and environmental conditions using stress–strain curves. This study investigates rocks’ dynamic strength and deformability behavior at different loading rates and temperatures. For this purpose, 30 travertine rock samples from the Torshab mine, located in the Markazi province of Iran, were first heated up to 100°C, 200°C, 400°C, 800°C, and 1000°C (six temperatures), and then subjected under the impact pressure with different loading rates from (five) 11 m/s to 15 m/s using the split Hopkinson pressure bar test. Comparing the obtained dynamic stress–strain curve shows that at a constant loading rate, increasing the temperature, especially at higher temperatures, reduces the dynamic strength and increases the rock’s deformability. Moreover, in all cases, at a constant temperature, increasing the loading rate, especially at higher rates, increases the rock’s dynamic strength and deformability.","PeriodicalId":46272,"journal":{"name":"International Journal of Protective Structures","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45400798","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 : 2023-09-04DOI: 10.1177/20414196231197702
Christian Jenni, Tim Altorfer, Sven Düzel, Mirco Ganz, David Denzler, F. Tillenkamp, André Zahnd, Lorenz Brenner
Traditional protective structures are usually equipped with ventilation systems. Main components of the latter are passive air blast safety valves. Their purpose in case of an explosive event outside the structure is to significantly reduce the blast pressure leakage into the structure in order to protect human individuals as well as technical installations. Until now, the performance determination of such valves is mostly realized by means of experimental tests in a shock tube. Considering industrial and modern civil protection applications with their practical implementation, additional methods are required to gain further insights into the behaviour of different valve closing mechanisms and to support novel developments as well as error analysis. For this reason, a practice-oriented procedure is presented, with the aim to extend the assessment of the closing behaviour and blast pressure leakage of passive air blast safety valves and the structural behaviour by numerical simulations. In a first preliminary step, potential software solutions have been evaluated based on literature research and expert knowledge. After evaluation of the obtained results, two different software pairs (fluid dynamic as well as structural dynamic tools) have been tested by carrying out indirectly coupled numerical simulations. The software pair APOLLO Blastsimulator & LS-DYNA achieved satisfactory results with the indirect coupling, so that direct fully coupled FSI simulations were additionally performed. To cover a broad range of blast safety valve applications, two different suitable test cases have been considered. In comparison to the experimental results, good agreement was achieved when analysing the pressure–time history of the blast pressure leakage and the closing time of the safety valve. Furthermore, the latter was confirmed by high-speed camera registrations during blast loading.
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