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Explosions caused by standoff charges near buildings have drastic effects on the internal and external structural elements which can cause loss of life and fatal injuries in case of failure or collapse of the structural element. Providing structural elements with blast resistance is therefore gaining increasing importance. This paper presents numerical investigation of RC columns with different reinforcement detailing subjected to near-field explosions. Detailed finite element models are made using LS-DYNA software package for several columns having seismic and conventional reinforcement detailing which were previously tested under blast loads. The numerical results show agreement with the published experimental results regarding displacements and damage pattern. Seismic detailing of columns enhances the failure shape of the column and decrease the displacement values compared to columns with conventional reinforcement detailing. Further, the effect of several modeling parameters are studied such as mesh sensitivity analysis, inclusion of air medium and erosion values on the displacements and damage pattern. The results show that decreasing the mesh size, increasing erosion value and inclusion of air region provide results that are very close to experimental results. Additionally, application is made on a slab-column multistory building provided with protective walls having different connection details subjected to blast loads. The results of this study are presented and discussed. Use of a top and bottom floor slab connection of protective RC walls are better than using the full connection at the four sides to the adjacent columns and slabs. This leads to minimizing the distortion and failure of column, and therefore it increases the chance of saving the building from collapse and saving human lives. Doi: 10.28991/cej-2021-03091733 Full Text: PDF

Considerable research has been carried out to establish a rational assessment method for nuclear power plants against external projectile impact. Most of the empirical formulas have been proposed to quantitatively investigate local damage to reinforced concrete (RC) structures caused by rigid projectile impact. These formulas were derived based on impact tests performed normal to the target structure, while only a few impact tests oblique to the target structure were studied. This work aims to propose a new formula for evaluating local damage to RC structures caused by oblique impact based on experimental and simulation results. At present, we have validated an analytical method via comparison with experimental results and have conducted simulation analyses of oblique impact assessments on RC slabs using projectile with flat nose shape. In this study, the same analytical method will be used to investigate perforation damage to RC slabs subjected to oblique impact by projectiles with hemispherical nose shape. The effect of projectile nose shape on perforation damage to RC slabs, the residual velocity of projectiles and the time history of energy transmission will be discussed.

Relevance. By its nature, seismic action is represented by the accelerogram a pronounced multidimensional random process, generally containing six components. The calculation in the deterministic formulation does not always allow to adequately assess the reaction of the system. While the calculation in the probabilistic formulation more adequately reflects the work of the system and makes it possible to evaluate its seismic resistance with a given security. The aim of the work is to assess the actual load-carrying capacity safety margin and the taken when designing coefficient K1, taking into account the permissible damage to buildings and structures for the steel spatial frame when calculating on the seismic action. Methods. In the article, the steel spatial frame was calculated for two sets of accelerograms, with dominant frequencies close to the main frequencies of the frame's natural vibrations. Each set was synthesized as a family of unsteady random seismic impact implementations. The calculation was carried out on two-component seismic action in nonlinear dynamic formulation in the software complex LS-DYNA. Previously, the frame was designed in accordance with national standard SP 14.13330.2014 “Construction in seismic areas on the seismic action” of the design earthquake level in the software complex PC LIRA 10.8. According to the developed probabilistic method for each set the actual load-carrying capacity safety margins were obtained and the coefficients K1 were estimated. Results . An analysis of the results shows that the steel frame under consideration has a sufficiently large margin of load-carrying capacity, and the coefficient K1 is taken in norms excessively conservatively. The developed technique allows to correct the value of the accepted coefficient K1 for buildings and structures of certain structural schemes. That in its turn will increase the economic efficiency of construction in seismic areas and ensure the reliability of the designed buildings and structures.

The protection of critical infrastructure, including government buildings, airports, religious buildings, military buildings and military vehicles, which are at risk to blast loads, has become important due to increasing terrorist activities in recent years. Sacrificial cladding systems based on negative Poisson’s ratio core topologies have recently received more attention as a protective technology due to its excellent energy absorption capability. In this study, field blast tests were performed on metallic re-entrant honeycomb-cored sacrificial cladding systems as protective structures for steel plate structures. This study focused on the near-field blast loading conditions where liquid Nitromethane (NM) spherical charges were detonated in close proximity to the main structure. Two 6 mm thick mild steel plates and two steel plates protected with re-entrant honeycomb-cored sacrificial cladding systems were among the specimens tested. The proposed auxetic cladding system was fabricated from aluminium sheets using a novel in-house built folding machine. Numerical simulations were conducted utilising LS-DYNA software and the Blast Impact Impulse Model (BIIM). The results obtained from the numerical simulations are in good agreement with the experimental results. It was found that the deformation pattern of the sacrificial auxetic cladding system varies with the intensity of the blast loading, and there is a limit at which the proposed protective system ceases to effectively absorb the applied blast loading. The variation of negative Poisson’s ratio of the system with blast loading was studied. It was found that the auxetic cladding system could become a solid projectile leading to damage amplification for very close-range blast loads due to rapid densification of the auxetic core. The proposed cladding systems with narrow re-entrant angles performed well under blast loads due to relatively low stiffness of the panels. Finally, the optimisation study was performed for the protective system. Overall, the experimental and numerical results assure that auxetic-based cladding systems are suitable for applications requiring blast protection such as armoured vehicles and critical physical infrastructure but need to be carefully designed for the given blast threat to prevent overloading of the protected structures.

Composite sandwich panels are commonly considered as lightweight materials for structural design in many applications including automotive, aerospace and defence systems. These panels must be devel...

Composite materials are being widely used in automobile industry in order to meet the ever increasing demand to achieve significant weight reduction by maintaining the performance levels. Additiona...

One of the biggest challenges associated with modelling the behaviour of reinforced concrete is the difficulty of incorporating realistic material models that can represent the observable behaviour of the physical system. Experiments for relevant loading rates and pressures reveal that steel and concrete exhibits a complicated nonlinear behavior that is difficult to capture in a single constitutive model. LS-DYNA provides several material models to simulate the structural behaviour of reinforced concrete. To provide some guidance in selecting the proper one for users who have limited experience on numerical simulation of steel and concrete, this paper reviews the background theory and evaluates performance of different material models to predicting the response of reinforced concrete structures to dynamic loads as well as advantageous and disadvantageous of models. Comparisons of several widely available concrete constitutive models are presented pertaining to their ability to reproduce basic laboratory data for concrete and steel as well as predict the response of structures subjected to shock and impact loadings. The performance of these models was assessed by comparison of finite element analysis model and experimental results of reinforced concrete structures to insure that the overall behaviour prediction is qualitatively acceptable, even if the exact parameter fit or material characterization is not available. The authors concluded that the accuracy of the finite element results relied on the selection of material model as well as the input parameter values. The material model assessment presented in this study can be used in the numerical simulation to generate appropriate models for concrete and steel.

Composite sandwich structures under ballistic impact loading can be a key point in the design for defense applications. This paper presents new armor designs consist of two composite plates with honeycomb core subjected to ballistic impact via 0.3-caliber Armor-Piercing projectile APM2. The numerical modeling of composite materials poses high challenges in simulating their anisotropic behavior under impact loading. Optimizing the failure criteria and examining the influence of changing the materials on ballistic response and energy absorption are considered. An enhanced composite constitutive model for composite plates and Johnson–Cook constitutive model for metallic honeycomb core are employed to permit the simulation of dynamic plastic deformations with the failure mechanisms during impact loading in LS-DYNA. A three-dimensional simulation is employed as highly efficient through the back-analysis of laboratory tests. The results of the numerical simulations are found to be in good agreement with the experimental results. Numerical studies are performed to assess the effects of different composite materials and various aluminum alloys for honeycomb core with different impact velocities on the behavior of hybrid composite sandwich armor. The proposed armor design can introduce a significant influence on enhancing the new armors generations and achieving good sturdiness and lightweight armors for defense applications.

Steel hollow section (SHS) tubular members have been widely used in the construction, infrastructure, onshore, offshore, mining, protective and security industries. Thus, strengthening of steel hollow tubular members is required to safely carry the dynamic loads to increase the security demands when the accidents, intentional impact, or explosive events occurred. In this paper, a finite element analysis tool, LS-DYNA is utilized to study the behaviors of (SHS) beam under a uniform transverse blast load. The explosive loads were sufficient in magnitude to cause plastic deformation of the cross-section (local deformation) and plastic flexural deformation of the overall member (global deformation). Different parameters were studied to investigate the effects of beam depth (H), beam width (B), support condition and axial load on the failure mode. The obtained displacement-time history from each simulation was recorded and compared. A numerical method for deriving pressure–impulse (P–I) diagrams for (SHS) beam, which subjected to transient loads are described in this paper, which can be applied in the preliminary design of protective structures to establish safe response limits based on the given blast-loading. The proposed model of (P–I) diagrams exhibited a good accuracy in predicting the pressure–impulse diagram to design the (SHS) beam under the extreme loads.

This paper presents the development and implementation of a user-defined material (UMAT) model for NiTi Shape-Memory Alloy (SMA) wires for use in LS-DYNA commercial explicit finite-element analysis software. The UMAT focusses on the Shape-Memory Effect (SME), which could be used for actuation of aerostructural components. The actuation of a fundamental structure consisting of an SMA wire connected in series with a linear spring was studied first. The SMA thermomechanical behaviour obtained from the finite-element simulation was compared with that obtained from the analytical solution in MATLAB. A further comparison is presented for an SMA-actuated cantilever beam, showing excellent agreement in terms of the SMA stress and strain as well as the tip deflection of the cantilever beam. A mesh sensitivity study on the SMA wire indicated that one beam element was adequate to accurately predict the SMA thermomechanical behaviour. An analysis of several key parameters showed that, to achieve a high recovery strain, the stiffness of the actuated structure should be minimised while the cross-sectional area of the SMA wire should be maximised. The actuation of an SMA wire under a constant stress/load was also analysed. The SMA material model was finally applied to the design of morphing aluminium and composite aerofoils consisting of corrugated sections, resulting in the prediction of reasonably large trailing-edge deflections (7.8–65.9 mm).

In this study, the energy absorption capacity of a front body of a bus during a frontal crash was investigated. The strength of the bus structure was examined by considering the ECE-R29 European regulation requirements. The nonlinear explicit finite element code LS-DYNA was used for the crash analyses. First, the baseline bus structures without any improvements were analyzed and the weak parts of the front end structure of the bus body were examined. Experimental tests are conducted to validate the finite element model. In the second stage, the bus structure was redesigned in order to strengthen the frontal body. Finally, the redesigned bus structure was compared with the baseline model to meet the requirements for ECE-R29. In addition to the redesign performed on the body, energy absorption capacity was increased by additional energy absorbers employed in the front of bus structure. This study experimentally and numerically investigated the energy absorption characteristics of a steering wheel armature in contact with a deformable mannequin during a crash. Variations in the location of impact on the armature, armature orientation, and mannequin were investigated to determine the effects of the energy absorption characteristics of the two contacting entities.

Reinforced concretes (RC) have been widely used in constructions. In construction, one of the critical elements carrying a high percentage of the weight is columns which were not used to design to absorb large dynamic load like surface bursts. This study focuses on investigating blast load parameters to design of RC columns to withstand blast detonation. The numerical model is based on finite element analysis using LS-DYNA. Numerical results are validated against blast field tests available in the literature. Couples of simulations are performed with changing blast parameters to study effects of various scaled distances on the nonlinear behavior of RC columns. According to simulation results, the scaled distance has a substantial influence on the blast response of RC columns. With lower scaled distance, higher peak pressure and larger pressure impulse are applied on the RC column. Eventually, keeping the scaled distance unchanged, increasing the charge weight or shorter standoff distance cause more damage to the RC column. Intensive studies are carried out to investigate the effects of scaled distance and charge weight on the damage degree and residual axial load carrying capacity of RC columns with various column width, longitudinal reinforcement ratio and concrete strength. Results of this research will be used to assessment the effect of an explosion on the dynamic behavior of RC columns.

Detonation of an anti-tank (AT) mine or improvised explosive device (IED) yields a shock wave, which can result in a severe damage to a vehicle and its personnel. Blast mitigation techniques play i...

The analysis aimed to assess the passive safety of supporting masts for road signs in accordance with EN 12767. Experimental tests were carried out based on the requirements of the standard for the smallest and the largest constructions within the product family. Numerical models of crash tests were prepared for whole product family using the Finite Element Method in the LS-Dyna environment. Based on the comparison of the experimental tests and the numerical calculations, the usefulness of the numerical model for estimating the actual value of the Acceleration Severity Index (ASI) and the Theoretical Head Impact Velocity (THIV) was assessed. With the use of these relationships the values of ASI and THIV for masts not tested experimentally were estimated. It was confirmed that the analyzed masts met the requirements for the passive safety of structures set out in the standard EN 12767. It was possible since as a result of the impact, the mast column detached from the base, allowing the vehicle to continue moving. The behavior of the masts was primarily influenced by the destruction of the safety connectors. The paper presents the most important elements from the point of view of designing such solutions.

The application of a simplified approach with the introduction of K1 to take into account the nonlinear behaviour of buildings and structures of some structural layouts when designing buildings and structures in seismically hazardous areas can result in a lack of seismic resistance. The use of nonlinear dynamic methods that allow the combined performance of reinforcement and concrete using finite solid elements to be explicitly considered can provide for more reliable results. The work evaluates the value of the allowable damage accounting factor K1 and assesses the actual level of seismic resistance of a 5-storey reinforced concrete cross-wall building given a seismic impact with an intensity of 9 points on the MSK-64 scale.

In this paper, advanced finite element (FE) methods are developed to investigate the effect of deceleration on the crash dummy test complied with British Standard Engineering (BS EN 1789). These techniques, which are related to material modelling, joints and contacts, offer an advanced numerical model representing an infant incubator with all complex boundary conditions and design contents. It is shown that the response of an infant incubator is a function of the ratchet straps, the tension on the belts, the belt type and the distance of the belts from the edges of the incubator, which can significantly affect the experienced acceleration, by the infant. The validation process is performed against experimental studies and various case parameters such as crash dummy mass and negative acceleration impulse are discussed in detail. The developed numerical model is capable to predict the behaviour of the crash dummy and the incubator in terms of acceleration, trajectory and kinematics by less than 8% error.

The paper presents design process and numerical simulations of safety tests of the operator's protective structure of earth-moving machinery. It is connected with international code requirements according to design the protective structure of machines in the case of working environment with a danger of falling objects or situation of rolling-over. The discrete finite element numerical models and results of numerical simulation of codes required tests are presented. All finite element simulations were done using LS-DYNA software.

This paper presents the development and application of comprehensive numerical modelling techniques to simulate the blast response of cable supported facades (CSFs) and compares the responses of cable truss and cable net facades which are two popular types. The results of the comparative analysis are used to evaluate the influence of the facade type on the key response parameters and hence their effective performance under blast loads. Modelling approaches, material models and constraint types used are presented along with the validation of the procedure. Results from numerical models created in LS DYNA are compared with existing numerical and experimental results from literature to validate the modelling techniques. Behaviour of cable net and cable truss facades under a credible blast event are then compared by analysing the effects of cable and panel configurations. The findings of the comparative analysis, show that cable truss facades (in general) have reduced deflections and higher energy absorption capacities, but with larger cable forces. This information can be used in the design of either facade type to obtain the desired blast response. The numerical modelling techniques developed in this paper deliver important information on the blast response and failure assessment of cable supported facades and the comparative analysis will provide guidance in future research and investigation to enable safer designs.

In order to study on the vibration effect of the blasting in the upper and lower cross tunnels, depress the impact of blasting vibration on existing adjacent tunnel and acquire the sound way of tunnel blasting construction, the finite element software LS-DYNA was adopted to calculate what vibration effect of existing tunnel would be generated by the different detonation modes (simultaneous initiation and hole-by-hole initiation) and the different cut modes (parallel cut and oblique cut). In general, the results of numerical simulation compared with the results measured in real, they are generally consistent. Results show that the vibration velocity of hole-by-hole initiation of digital electronic detonator is 40% lower than ordinary simultaneous initiation of millisecond detonator, and the vibration acceleration is reduced by 24%. As regards vibration displacement, the distinction between the two detonation modes is small. The rule of velocity decay with increasing distance from the initiating position is similar in this two cases. Meanwhile, the vibration velocity of oblique cut is lower than parallel cut. But, for the vibration acceleration, the oblique cut is 15% higher than parallel cut. For oblique cut, the seismic waves show a pronounced periodicity and the energy is relatively concentrated. The fact is quite opposite when the parallel cut applied. In the case of explosion of hard rock strata, the effect of oblique cut is better than parallel cut.

Existing research on the widely used concrete-filled steel tubes is mainly focused on static or cyclic loading, and the studies on effects of high strain rate are relatively rare. In this article, seven stub concrete-filled steel tubular columns with square section were tested under both static and impact loads, using a large-capacity drop-weight testing machine. The research parameters were variable height of the drop-weight and different load types. The experimental results show that the failure modes of the concrete-filled steel tube columns from the impact tests are similar with those under static load, characterized by the local buckling of the steel tube. The time history curves of impact force and steel strain were investigated. The results indicate that with increasing impact energy, the concrete-filled steel tube stub columns had a stronger impact-resistant behavior. The dynamic analysis software LS-DYNA was employed to simulate the impact behaviors of the concrete-filled steel tube specimens, and the finite element results were reasonable compared with the test results. The parameter analysis on the impact behavior of concrete-filled steel tube columns was performed using the finite element model as well. A simple method was proposed to calculate the impact strength of square concrete-filled steel tube columns and compared favorably with experimental results.

A physically representative bird modeling approach is presented to highlight its significance over traditional substitute bird modeling. To give better representation of a real bird, in this study, the bird was modeled as a fluid body while impacting the rigid and deformable structures. For this, an elastic plastic hydrodynamic material model in conjunction with polynomial equation of state is utilized to model the bird behavior. In addition, smoothed particle hydrodynamics (SPH)-based meshless technique was implemented to build real bird model instead of using finite element-based classical mesh technique in order to avoid mesh connectivity and tangling problems. The numerical scheme was validated by comparing the deformation and pressure profile of the impact on rigid and deformable targets with the available experimental data. The results showed that the physically representative bird impacting the rigid and deformable target give correct values of pressure peak than that of substitute bird. The study also revealed that, the bird impacting the target from bottom direction resulted higher magnitude of pressure shock than head, tail or wing direction. In addition, the instantaneous peak impulse during bottom side impact is more detrimental to impacting structure than other impact directions. Finally, after quantifying the effect of bird impact directions, the work was further extended to establish a full-scale numerical model of a military aircraft windshield–canopy structure to determine its dynamic response against similar impact scenarios. The results showed that the bird impacting from bottom side requires relatively less velocity to initiate failure in the windshield than other impact directions. Thus, the bird impacting from its bottom side was recognized as the most dangerous impact condition for structural integrity of windshield.

This article studies the feasibility of using geodesic domes as expeditionary protective structures, since they are fast-assembly lightweight structures and are able to withstand very heavy loads due to their specific geometry. A 6-m standard International Orginization for Standardization container is used as a benchmark structure for the study, which is developed using the nonlinear explicit code LS-DYNA. The blast simulations were performed with the Load Blast Enhanced option, using the phenomenological Johnson–Cook constitutive model to reproduce the behaviour of steel subjected to a large range of strain rates. The performance assessment of the protective structures under blast loading was based on the evaluation of the associated safety zones inside the protective shelter as well as on the characterization of the potential structural damage. With the additional insights provided by this article, it is possible to identify some of the competitive advantages shown by this type of structures which will hopefully foster new advances in the field.

This paper presents a finite element (FE) modelling to predict the behaviour of ultra-high performance concrete (UHPC) members under static flexural loading. A plasticity-based constitutive model for concrete and an implicit solver in LS-DYNA were adopted in the numerical simulation. Experimental data for 21 UHPC specimens tested in the present study and in previous works were used to calibrate and validate the proposed FE model and modelling technique. The simulation was able to accurately predict the experimentally obtained ultimate strength, stiffness, and hardening and softening behaviours of the specimens. This demonstrates the effectiveness and adequacy of the developed FE model and modelling technique.

In the automobile industry, accurate prediction of crashworthiness indicators is important in designing energy absorbing tubes for the protection of occupants. However, the deformation behavior of these tubes was found to be affected by the prior manufacturing (forming) process. Hence, it is necessary to incorporate these forming effects in the crash simulation model to improve the accuracy of the simulation results. Therefore the interactive computational approach was used in this research article to account for the forming and crash response of the proposed capped cylindrical tubes. In this procedure, the design of forming tools based on the computer-aided automated computing system is performed first and the results are considered in the multi-stage deep drawing process. Then, the influences of forming parameters of a multi-stage deep drawing process on the axial crushing response of thin-walled capped cylindrical tubes were numerically examined using LS-DYNA follow-on simulations. The residual forming history such as effective plastic strain, thickness variation, and residual stress was mapped to crash simulation models in order to understand the interaction between the forming process and subsequent crash performance of the proposed tubular structures. The capped cylindrical tubes of shell element with a constant thickness of 1.63 mm were also simulated for comparison purpose. The finite element crash model included with forming simulation results caused an increase in the initial peak crushing force by 15–30% over constant thickness tubes. In order to validate the numerical simulation results, experiments were performed. The application of a constitutive crash simulation model considering these forming parameters when studying the axial crushing characteristics of the tubular structures that have experienced earlier forming processes is strongly recommended.

This work investigates the response of a blast loaded reinforced slab with different constructive characteristics. This topic has been well covered during the last years, but there are a reduce number of them that presents blast test at realistic scale. Seven different slabs were tested: three at a scaled distance of 0.79 m/kg1/3, one at 0.41 m/kg1/3 and four with 0.20 m/kg1/3. The three tests with high-scaled distance, used as calibration tests, have been characterized with pressure gauges and accelerometers. These reinforced slabs are the same as the one of low-scaled distance and one of high-scaled distance. Finally, the two tests of low-scaled distance have different reinforcement: steel or polypropylene fibres. The blast effects over the slabs has been characterized with a non-destructive methodology based on the Schmidt hammer. The methodology consists on the evaluation of a statistically significant difference of six rebound values before and six after a blast event for each evaluation point, having 19 evaluation point for each slab face. based on each individual damage value, damage maps have been created using an interpolation tool. This methodology is very useful to quantify the non-visual damage of a structural element and to validate numerical modelling results. In this case, a 3D lagrangian simulation using the lS-DYNA code with the blast load routine called cONWEP was done. The results in the developed model are affected by the scaled distance and by the construction patterns. The blast resistance of the slabs were better when using steel or polypropylene fibres, especially under tensile stresses (bottom part of the slabs).

Prestressed concrete sleepers are the most commonly used type of railway sleepers in ballasted railway track. They have a strong influence on track performance, track stiffness and railway safety. Reportedly in many railway lines (especially in heavy-rail networks), many prestressed concrete sleepers have failed due to rail seat abrasion (RSA). RSA is a wear deterioration of the concrete underneath the rail that results in various problems such as loss of fastening toe load, gauge variation, improper rail cant, and eventually loss of rail fastening. In addition, the RSA will directly decrease the capacity of worn concrete sleepers. However, to the best of authors' knowledge, there were very few studies that quantitatively examined the effects of RSA on the structural capacity of the prestressed concrete sleepers. In this paper, a numerical study is executed to evaluate the load-carrying capacity of a prestressed concrete sleeper using LS-DYNA. The nonlinear model was validated firstly based on both theoretical analyses and experimental results in accordance with Australian Standard. Using the validated finite element model, the influences of different wear depth of RSA are investigated; and different compression strength and tensile strength of concrete and the prestress losses are highlighted. The outcomes of this study lead to better insight into the influences of RSA more clearly and improve track maintenance and inspection criteria.

The purpose of this research was to investigate the possibility of blood flow modelling in LS-DYNA using its SPH solver and SPH-FEM coupling. SPH and FEM methods are both based on the continuum mechanics, and SPH uses Lagrangian material framework, while FEM can use both Lagrangian for solid, and Eulerian formulation for fluid analysis. SPH implementation is mesh-free giving it the capability to model very large deformations without mesh distortions. However, this comes at a high computational price, so the number of SPH particles needs to be significantly lower in comparison to the number of FEM elements in the Eulerian analysis of the same fluid domain. In the case of combined SPH-FEM analysis, the blood vessel wall is modelled with FEM shell elements, while the blood inside is modelled with SPH particles. The contact between the two is done using nodes to surface algorithm, while if we use the SPH only, there is no need for the specific contact definition. The Lagrangian framework of the SPH method means that we need to generate particles at one end, and to destroy them on the other, in order to generate a continuous fluid flow. To do this we used activation and deactivation planes, which is a solution implemented in the commercial LS-Dyna SPH solver. In the results section of the paper, the velocity field of blood obtained by implementation of described modelling methodology is shown. SPH-FEM coupling offers greater possibilities to study the effects of wall deformations, tracking of movement of solid particle inclusion, or mixing two different fluids, but it requires elaborate contact definition, and prolonged analysis time in comparison to the FEM CFD analysis.

This paper takes a finite element model of a 12-meter bus as an example. Based on the HyperWorks and LS-DYNA joint collision simulation analysis method, frontal collision simulations with different initial speeds are carried out respectively, and the deformation, speed and acceleration changes of the bus under different collision speeds are analyzed. Summarize the development law of the mechanical characteristics of bus frontal collision.

Characterizing structural resiliency after severe damage to a few load-carrying members is challenging. Engineers use various computational approaches to assess the vulnerability of structu...

In order to reduce the damage caused by vehicle-bridge collision and provide theoretical basis for the design of anti-collision device, this paper establishes vehicle-facility-pier dynamic model, proposes stiffness matching method, analyzes the impact of anti-collision facility stiffness, and establishes simulation models of 38t vehicles, round piers and anti-collision devices by using dynamic simulation software, and studies the protective effects of vehicles hitting bare piers and piers with anti-collision devices at different speeds and angles. The results show that the impact force decreases non-linearly with the increase of the stiffness of anti-collision facilities. After adding anti-collision devices, the positive impact force of vehicles decreases by 52% and the impact time prolongs by 9%. The side impact force is reduced by 91%, and the impact time is prolonged by 59%. Energy-consuming elements in side impact anti-collision facilities not only have compression deformation but also torsion deformation, thus reducing energy exchange during collision, effectively reducing impact damage, and providing basis for the design and application of bridge pier anti-collision device.

Critical civilian facilities and military infrastructure in India have been a target of several terrorist attacks in the last few decades. In order to address the risk of explosion threats, it has become critical to design and construct blast-resistant structures to save lives and protect infrastructure. The focus of this paper is to develop performance-based guidelines for the blast-resistant design of reinforced concrete (RC) columns. Columns are the most vulnerable component of a structure and are at a high risk under a detonation scenario. The paper presents a comprehensive review of the blast-resistant design procedures followed by different design documents. The gaps and challenges in the blast resistance of RC columns were identified and addressed. Specific issues in the axial, flexure, and shear design of columns are highlighted. A performance-based analysis and design approach for blast-resistant design of RC column were developed and is presented in the paper. The design approach was verified using high-fidelity numerical simulations. The performances of the design columns was assessed using nonlinear FE models developed in LS-DYNA. The ultimate capacities of the columns subject to blast loads were obtained. The numerical simulations assist in verifying the proposed design procedures and provide critical information on the failure modes, safety margin, and other parameters for blast-resistant design of RC columns. Recommendations on safe and efficient design of RC members are also provided.

Shortening delays for immediate access to essential public infrastructures when subjected to rare extreme loadings are critical to promptly normalize socioeconomic activities. Public infras...

Brain injury resulting from improved explosives devices (IEDs) is identified as a challenge for force securities to improve protection equipment. This paper focuses on the mechanical response of explosive ordnance disposal (EOD) helmet under different blast loadings. Limited published studies on this type of helmet are available in the scientific literature. The results obtained show the blast performance of the EOD helmet because a decrease in the maximum values in the measured damage parameters is found. Therefore, an EOD helmet minimizes the risks of the severity of injuries on the user showing a low probability of injury. The authors acknowledge the Ministry of Economy and Competitiveness of Spain and FEDER program under the Project DPI2017-88166-R for the financial support of the work, and Marcos Rodríguez-Millán thanks the Spanish Ministry of Education, Culture and Sports for the professor’s mobility program José Castillejo’s 2018 grant (CAS18/00292).

The aim of this research is to study the behavior of human head during the event of impact while wearing a helmet with and without locking the chinstrap. While many accidents are reported due to the negligence of wearing a helmet, there are also a few cases where not locking the chinstrap of the helmet led to major loss of lives. There is no much information about the threat level caused due to negligence of locking the chinstrap while wearing a helmet. This paper investigates the significance of locking the chinstrap, and compares the results of impact on head in both cases. The dimensions of a commercially available helmet are considered, and a head is designed to fit into the helmet. Numerical simulation, i.e., Impact test is carried out with the presence of chinstrap and in the absence of chinstrap using computer-aided engineering simulation solver LS-Dyna. The FEA model preparation and meshing is carried out using Hypermesh. Finally, comparisons are made on the impact of injured head. Results are plotted using Hyperview software. The impact forces during drop test of the helmeted form with a chinstrap were found to be minimal when compared to the forces without a chinstrap. The stresses on the chin region were major in case 2 in contrast with case 1 stresses. Energy plots were similar in both the scenarios, which ensure that drop test behavior is proper. The significance of chinstrap of helmet is immense while driving a two-wheeler. Numerical simulation also proves the importance of the chinstrap. Wearing a helmet with locked chinstrap results in minimal injuries to the victim rather than long-term diseases and death.

Recently, blast and impact have gained more importance in research work owing to the fact that these high-intensity events can completely destroy any structure, causing tremendous casualties and property loss. Therefore, for any structure to withstand such extreme events, it is important to consider the effect of blast and impact loading in their design. Research works on response and damage analysis of reinforced concrete structural components such as slabs, columns, beams and walls subjected to blast and impact are limited in the literature and are essential for assessing its vulnerability. The current work investigates the performance of two-way reinforced concrete (RC) slabs subjected to blast loading. To simulate the field blast tests on different slabs, initially, a numerical model is established in a finite element preprocessor (HyperMesh). Later on, with the help of a commercial simulation software package (LS-DYNA), the numerical analysis is carried out. The developed numerical model is validated with the results of an experimental work done on an RC slab subjected to air blast from previous research. The results of the developed model are found in close agreement with actual experimental results. The numerical parameters of the validated model are used to develop a probabilistic model to investigate the blast response of the slab designed in current work. The probabilistic model developed in this research is able to capture the damage phenomena and also capable enough to reproduce the dynamic response.

This study employed C4 explosives to evaluate the overpressure response in steel tunnels subjected to external explosions. The explosive scaled distance of the C4 charge from 2.15 to 3.26 m/kg1/3 was evaluated by experiments and the hydrodynamic finite element code LS-DYNA. The numerical results are in agreement with the experimental results. A simple way to estimate the overpressure in steel tunnels was proposed in this paper. The proposed methodology is both useful and efficient and can be further developed for designing protection for military structures and other facilities against explosion.

Aircraft bird strikes are a major threat to human life and systems that are immune to birds striking need to be built. This paper addresses the numerical simulation of the bird attack on a composite wing leading edge of the aluminium–silicon carbide (Al-SiC) metal matrix using LS-Dyna tools. The base material of the metal matrix chosen is made of aluminium 85% and silicon carbide 15%. The impact strength of the material is high in this composition, which means it is more resistant to impacts suited for the wing leading edge because it is subject to events like bird strike. CATIA-V5 with skin thickness of 2 mm was designed for the wing-facing portion. The ribs and the spar were both designed to produce improved performance. For bird hitting, a hemisphere cylinder configuration is used and has a length 196 mm with a diameter of 98 mm in the LS Pre-Post V4.7.7. The leading wing layout has been imported into LS Pre-Post and is correctly calibrated for bird strike research. The birdstrike analysis is done by the Lagrangian method. The required keyword input data, such as border identification, power, identification of touch, bird and wing edge property and bird speed, are specified according to the research requirements. The test has been performed at various speeds from 50 to 150 m per second. In this study, the efficacy of the wing leading edge with Al-SiC material in contrast to the conventional Al 7075T6 material was improved by about 100 MPa. In the wing segment with Al-SiC material, the pressure distribution over the wing leading edge surface would also be smoother. The wing part has increased energy absorption. The overall strength of the Al-SiC flange leading section is increased as compared to the Al 7075T6 material for the flange leading edge section.