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This paper presents the nonlinear vibration analysis of a sandwich shallow shell with a honeycomb core and functionally graded graphene-reinforced skins (HCFG-GRCF) under blast load, where the core layer is composed of negative Poisson’s ratio material and the three kinds of graphene distribution patterns are considered for structural face layer. First, the material properties of functionally graded graphene platelet reinforced composite (FG-GRC) are calculated using the extended Halpin–Tsai model. Based on the First-order shear deformation theory (FSDT) along with von-Karman nonlinearity, the energy function of the shallow shells is derived. Then the direct iterative method and Newton–Raphson method are, respectively, adopted to solve the nonlinear free vibration and dynamic response in the temporal domain. The applicability and accuracy of the proposed dynamic model are verified by comparing the present results with literature solutions and Finite Element Method (FEM) results. In addition, the effects of temperature, graphene fraction, thickness ratio of core to face thickness, honeycomb cell inclined angle and boundary conditions on the dynamic response of the shallow shells are systematically analyzed. [ABSTRACT FROM AUTHOR]

The current work provides the comparative study based on nonlinear dynamic responses and damping performance of the viscoelastic core-based sandwich (SW) plates subjected to blast load. The 0–3 viscoelastic composite (VEC), pure/conventional viscoelastic material (VEM), and viscoelastic particulate composite (VEPC) are taken individually as the viscoelastic core within SW plate. The governing equation of motion (GEM) of the overall SW plate is formulated by following layer wise theory and fraction order derivative viscoelastic model in finite element framework. The numerical solutions are obtained by solving the GEM with the conjunction of Newmark time integration scheme and direct iteration method. The effect of various boundary conditions, geometric parameters of 0–3 VEC, particulate volume fraction in VEPC are considered on dynamic responses and damping performance of SW plate. The numerical solutions disclose that 0–3 VEC and VEPC provide the significant damping compared to conventional VEM for passive damping control of SW plates subjected blast loads. [ABSTRACT FROM AUTHOR]

The safety of civilian and military infrastructure is a concern due to an increase in explosive risks, which has led to a demand for high-strength civil infrastructure with improved energy absorption capacity. In this study, a Finite Element (FE) numerical model was developed to determine the effect of hybrid Fibre Reinforced Polymer (FRP) as a strengthening material on full-scale Reinforced Concrete (RC) slabs. The reinforcing materials under consideration were Carbon (CFRP) and Glass (GFRP) fibres, which were subjected to blast loads to determine the structural response. A laminated composite fabric material model was utilized to model the failure of composite, which facilitates the consideration of strain rate effects. The damaged area of the laminate is determined in the FE model, and it is in good agreement with the corresponding experimental results in the literature. Models containing different stacking sequences were built to demonstrate their efficiency in resisting blast loads. In general, the damaged area was reduced when a hybrid reinforcement with CFRP as the top layer was used. [ABSTRACT FROM AUTHOR]

The explosion products, such as shock waves, fragments and heat energy formed by explosion, act on the plate structure, which may cause structural damage, material failure and even phase transformation of material. In this paper, the damage mechanism and protective effect of near-field blast load on sandwich structure based on foam-nickel core material were studied. Firstly, the near-field explosion test was conducted to investigate the blast response of the foam-nickel sandwich structure subjected to blast shock from 8701 explosive at near-field position. The deformation characteristics and stress history of the sandwich structure on the acting location of blast load were carefully investigated via experimental methods. A finite element model of near-field explosion was established for effective numerical modelling of the dynamic behaviour of the sandwich structure using the explicit dynamics software ANSYS/LS-DYNA for more comprehensive investigations of the blast shock response of the sandwich structure. The finite element model is reasonable and validated by mesh independence verification and comparing the simulated response behaviour to that from the experimental results for the sandwich structure subjected to near-field blast load. On this basis, the damage mechanism and protection effect of the near-field explosion impact on foam-nickel cores with different density and porosity are simulated more systematically. The investigated results from the experiments and a series of numerical simulations show the large deformation effect due to the extensive energy absorption, which suggests that the sandwich structure based on foam-nickel core material may be expected to become a new choice of protective structure under near-field blast load. [ABSTRACT FROM AUTHOR]

The experience of recent military missions clearly shows the importance of protecting vehicles and the people they carry from mines and IEDs. This protection can be achieved in many ways, using both active and passive solutions. One of the most popular solutions is using energy deflectors, which, thanks to their appropriately selected shape, can dissipate the energy from the detonation of an explosive charge, thus reducing the blast wave loading on the protected structure. The article presents the research results on two innovative groups of deflectors—double-bend and semi-spherical, characterized by a better ability to disperse energy than traditionally used V-shaped deflectors. Several possible geometric shapes differing in critical dimensions were selected, and both experimental studies and numerical analyses were carried out. A ballistic pendulum was used to measure individual deflectors' performances. The tests proved the tested solutions' increased effectiveness compared with V-shaped deflectors. [ABSTRACT FROM AUTHOR]

With the increasing number of violent terrorist attacks around the world, it is quite a common to improve the anti-blast performance of structures by reinforcing the exterior of the structure. In order to explore the dynamic performance of polyurea reinforced concrete arch structures, a three-dimensional finite element model was established by LS-DYNA software in this paper. Under the condition of ensuring the validity of the simulation model, the dynamic response of the arch structure under the blast load is investigated. Deflection and vibration of the structure under different reinforcement models are discussed. The optimum thickness of reinforcement (approximately 5 mm) and the strengthening method for the model were found by deformation analysis. The vibration analysis shows that the vibration damping effect of the sandwich arch structure is relatively excellent, but increasing the thickness and number of layers of the polyurea does not necessarily achieve a better vibration damping function for the structure. By reasonable design of the polyurea reinforcement layer and concrete arch structure, a protective structure with excellent performance of anti-blast and vibration damping can be created. Polyurea can be used as a new form of reinforcement in practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is the first work for studying the equipment damage caused by HBNG explosions. • ALE algorithm and fluid–structure coupling theory are used to simulate the explosion. • The effects of the HBNG explosion chain on equipment are analyzed in tank areas. • The response of tanks exposed to HBNG explosions under various parameters is analyzed. • Guidance for the design of tanks to resist HBNG explosions is provided. Hydrogen is a renewable and clean energy and obtains increasing attention all around the world. Blending hydrogen into natural gas can promote hydrogen development and storage tank farms play an essential role in the storage of hydrogen-blended natural gas (HBNG). However, upon leakage from the tank, HBNG accumulates to create a vapor cloud and may explode, resulting in more severe consequences than natural gas. Furthermore, the explosion has the potential to trigger the domino effect in the spherical tank storage area, leading to multiple explosions. But little attention has been paid on this research issue. This article analyzes the dynamic response of the spherical tank exposed to HBNG explosions. The fluid–structure interaction theory is adopted to establish the whole finite element model. Meanwhile, the advanced Arbitrary Lagrangian-Eulerian (ALE) method can reduce mesh distortion and enhance computational accuracy, and the process of explosion is analyzed through the coupling of the Lagrangian mesh for the structure and the Eulerian mesh for the vapor cloud. Then, the algorithm is employed that couples shell elements with solid elements by utilizing a penalty function. Besides, the dynamic response of the spherical tank and pillar surfaces is analyzed in the trends of effective stress, displacement, velocity, and structural damage under various parameters, evaluating the energy absorbed by the spherical tank and pillar. Accordingly, the equipment damage caused by HBNG explosions considering possible damage caused by secondary explosions can be obtained. Then, the effects of the HBNG explosion chain on equipment are analyzed in tank areas. The dynamic response of structures in the explosion is closely related to the different hydrogen blended ratios, distances, and structural thickness, which significantly impact the effective stress of the spherical tank and pillar. Moreover, the damage caused by the HBNG explosion is more serious for pillars than the spherical tank, making the role of pillars crucial in supporting the spherical tank. The results obtained in this study can be used to support the design and safety operation of HBNG storage areas. [ABSTRACT FROM AUTHOR]

The experience of recent military missions clearly shows the importance of protecting vehicles and the people they carry from mines and IEDs. This protection can be achieved in many ways, using both active and passive solutions. One of the most popular solutions is using energy deflectors, which, thanks to their appropriately selected shape, can dissipate the energy from the detonation of an explosive charge, thus reducing the blast wave loading on the protected structure. The article presents the research results on two innovative groups of deflectors—double-bend and semi-spherical, characterized by a better ability to disperse energy than traditionally used V-shaped deflectors. Several possible geometric shapes differing in critical dimensions were selected, and both experimental studies and numerical analyses were carried out. A ballistic pendulum was used to measure individual deflectors’ performances. The tests proved the tested solutions’ increased effectiveness compared with V-shaped deflectors.

Laminated insulating glass units (IGUs), commonly used in modern buildings, are prone to shattering from explosive loads, causing significant damage and loss. Existing research on IGUs is constrained by a lack of experimental validation and comprehensive numerical analyses, as large-scale explosion tests are rarely reported due to safety and cost concerns. Furthermore, previous modeling efforts often oversimplify critical factors such as the supporting structure, component interactions, strain rate effects, hourglass energy, and failure criteria, leading to an inadequate representation of glass behavior under explosive loads. This paper addresses these gaps by conducting large-scale explosive test on glass system and utilizing sophisticated nonlinear dynamic analysis with LS-DYNA for simulation. The research considers the influence of the support system and incorporates detailed considerations of component interactions, constitutive relationships, and strain rate effects in the numerical simulations. The results confirm that the proposed model successfully replicates the crack patterns and damage observed in experimental test. Also, it accurately predicts the trajectory, quantity, and size distribution of glass fragments. The proposed modeling approach offers a more informed assessment of damage and improves the evaluation of glass safety in practical applications. • A full-scale explosive testing of laminated insulated glass units (IGUs) provides valuable data for simulation model development. • An advanced finite element model is provided for accurate assessments of glass blast resistance. • The Johnson-Holmquist 2 material model is validated for accurately simulating glass behavior under high-speed impacts. • Explosion-proof performance levels of insulating laminated glass are quantified under large explosion conditions as per related standards. [ABSTRACT FROM AUTHOR]

Expensive mitigation measures are generally adapted for structures that are vulnerable to blast loading. But, literature shows that a building with seismic design and detailing has some inherent capacity to resist blast loading. As such, a nonlinear three-dimensional finite element model is developed using finite element software ABAQUS to study the performance of a reinforced concrete (RC) column designed and detailed with three levels of seismic detailing under blast loading as per Bangladesh National Building Code 2020, which is similar to ACI 318-08. The vulnerability of damage due to blasting is determined according to the residual capacity of the column. The nonlinear behavior of concrete is simulated in ABAQUS using the concrete damage plasticity (CDP) model. Blast pressure is applied on the front face of the column using the built-in CONWEP module. The results show that closely spaced lateral reinforcements significantly reduce the damage and blast vulnerability of the RC column under blast loading. In addition, favorable effects on the blast resistance of the RC column are found with a lower charge mass, larger size of columns, increased height of the blast, and higher axial load ratio. [ABSTRACT FROM AUTHOR]

The structural performance of perforated steel columns (PSCs) is significantly more complex than the one of solid web I-shaped elements under the diversity of blast loading scenarios. The damage criterion of PSCs is not only related to initial deformation response during the blast but also the residual axial load capacity and it can be considered as a reliable index after the blast effects. Therefore, the PSCs damages will be studied in two stages; direct and post blast effects. In the present study, the dynamic response of PSCs was numerically evaluated under different levels of blast threats using LS-DYNA software. Extensive explicit finite element (FE) analyses are carried out to investigate the effect of various parameters, such as web opening shapes, boundary conditions and strengthening details on the damage index and toughness of the PSCs compared to the parent steel sections. The results of the comparative study show that the damage and toughness decrease when the support condition changes from pinned to fixed ends through the two stages of loadings. PSCs give high toughness compared to its parent sections during blast shock stage while, a remarkable decrease in toughness is observed during the application of axial gravity after blast shock. Furthermore, the web opening shapes have slight effects on the global dynamic behavior of PSCs, particularly in terms of residual capacity. On the contrary, the retrofitting strategy using both closed holes at end and vertical stiffeners have an effective enhancement to get higher toughness in case of the extreme blasts. [ABSTRACT FROM AUTHOR]

A finite element model of steel frame joints is established using finite element analysis software ANSYS/LS-DYNA. The ideal triangular impact load is used to numerically analyze the dynamic response of steel frame welded joints under blast loading, the main factors affecting this response, and the failure modes of three types of joints, so as to provide reference for the antiexplosive design of steel frame joints. The results show that steel frame joints vibrate violently in the explosive blast direction. Due to the strain rate effect, the strength of steel increases, the material enters the plastic strengthening stage, and there is a certain residual displacement. In addition, displacement and stress caused by blast action in the joint area are large, and the flange shear failure of the beam and column is prone to occur in the joint. Increasing the flange width of the beam and the column cannot improve the antiexplosive performance of the joints, while increasing their thickness can. Furthermore, bolted and welded joints have the highest stiffness and best antiexplosion performance, followed by welded joints, while the antiexplosion performance of bolted joints was the worst. [ABSTRACT FROM AUTHOR]

• Predicting dynamic responses of MEE composite plates resting on visco-Pasternak foundation in hygro-thermal environment subjected to blast load is developed. • The variation of electric and magnetic potentials is determined according to electromagnetic boundary conditions and the Maxwell equation. • Effects of electric and magnetic loads, geometrical and foundation parameters on dynamic responses of MEE composite plates are investigated as new numerical results. • Elastic foundation, viscoelasticity, temperature, and moisture have been demonstrated to contribute considerably to the reduction of structural vibration. This is the first endeavor to present a finite element approach to predict free oscillation and transient characteristics of magneto-electro-elastic (MEE) composite rectangular and elliptical plates resting on the visco-Pasternak medium in a hygro-thermal environment subjected to blast load. The variation of electric and magnetic potentials along the thickness direction of the MEE plate is determined via the Maxwell equation and magneto-electric boundary condition. The governing equations of motion for the MEE plate are obtained using refined higher-order shear plate theory and Hamilton's principle. Stiffness matrices, mass matrices, damping matrices, and force vectors of the plate are derived using a four-node quadrilateral element with eight degrees of freedom per node approximated using C1-order non-conforming Hermite and Lagrange functions. In addition, the Navier close-form solutions for rectangular plates with simply supported boundary conditions are used as a useful comparison tool for the numerical solutions. Dynamic response results of plates were obtained using Newmark's direct integration written by Matlab's programming. The accuracy of the method is verified through numerical comparison with confidence statements. The results show that the applied magnetic and electric potential highly inspires the transient responses. These results can be used in vibration control studies of structures and structures subjected to explosive or low-velocity impact loads. [ABSTRACT FROM AUTHOR]

The main aim of present work is to investigate structural behavior of one-way reinforced concrete slabs retrofitted with fiber reinforced plastic. Retrofitting is done to enhance bending and shear strength, to increase confinement and to repair damages caused by corrosion and cracking. In retrofitting RC slabs FRP is often used to enhance bending strength by putting it on the tensile side of the slab in the region with maximum anchor, which leads to significant increase in slab’s energy absorption capacity. Finite Element Method (FEM) is widely used in different fields for structural, electrical, heat, and mechanical engineering. In the case of blast analysis, due to excessive cost, the danger of experiments and extremely short duration of the test, numerical simulation is more attractive. Explicit dynamics analysis procedure based on the implementation of an explicit integration rule together with the use of diagonal (“lumped”) element mass matrices is used, which is computationally efficient for the analysis of large models with relatively short dynamic response and for the analysis of extremely discontinuous events or processes. Computer code ABAQUS is used for the analysis and the results are compared with available experimental results in the literature and good agreement has been observed. Also it can be concluded that numerical method used in this study has good agreement with experimental work. Influence of different geometrical parameters including number of layers, orientation of the fibers and the aspect ratio of slab has been investigated. Upon comparison with available experimental results, it is shown that modeling techniques have good accuracy. It is found that regardless of the orientation of the fibers, displacement of the center of slab would be reduced significantly. When fibers orientation angle with respect to the main load bearing direction of the slab is [–20°, 20°], the blast strength of the slab is maximum. For slabs with low aspect ratio, the more the number of layers, the higher the blast strength. For slabs with high aspect ratio, there is no significant difference between different fiber arrangements and increasing number of layers has no significant effect on blast strength of slabs.

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. [ABSTRACT FROM AUTHOR]

Nonlinear air blast response of basalt composite plates is analysed by using a generalized differential quadrature (GDQ) method, which requires less solution time and decreases the complexity compared to finite element method. A test environment that contains a shock tube is designed and set to experiment on the transient response of blast loaded laminated plates. Experimental and numerical results show a good agreement in terms of displacement, strain, and acceleration versus time. The responses of glass/epoxy, Kevlar/epoxy, and carbon/epoxy composite plates are also investigated by using GDQ method and the results are compared with the basalt/epoxy composite plate and discussed. [ABSTRACT FROM AUTHOR]

The need for building protection against blast loads is a crucial issue nowadays due to the escalating threat of terrorist attacks, which affect people's lives and critical structures. Consequently, design of protective panels to segregate building façades from the effect of a nearby explosion is required. Such design mainly depends on the ability of protective panels to mitigate and diffract the blast wave before reaching building façades. Five protective panel models with different designs, referred to as the Combined Protection System (CPS), are introduced in this paper. The main objective of this research was to achieve a design that could sustain a blast load with minimum plastic deformations. The introduced CPS designs included two steel plates linked by connector plates. The CPS dimensions were 3 m × 3 m × 0.35 m, representing length, width, and height, respectively. After that, the successful panel design was supported by placing these panels onto a masonry wall in different configurations. The protective panels were tested against 50 kg of trinitrotoluene (TNT) with a standoff distance of one meter. The final run of the optimum model was carried out using a blast load equivalent to 500 kg of TNT. The air–structure interactions were simulated using finite element analysis software called "ANSYS AUTODYN", where the deformation of the panel was the governing parameter to evaluate the behavior of different designs. The analysis showed minimum deformation of the CPS design with vertical and horizontal connecting plates in a masonry wall distanced at 500 mm from the panel. However, the other designs showed promising results, which could make them suitable for critical structural protection on different scales. [ABSTRACT FROM AUTHOR]

• The feasibility of Monte Carlo analyzing the blast load variability was verified. • A simpler probabilistic modeling method was presented. • Probabilistic models of blast load from 1 m/kg1/3 to 40 m/kg1/3 were developed. • The equation for calculating the reliability-dependent blast load factor was given. Explosive blast loads are subject to variability and uncertainty, but most current studies of building blast resistance are deterministic. To quantitatively assess the safety and reliability of a structure under explosion, the variability of the blast load needs to be quantified. A probabilistic analysis method of blast loads based on the finite element model and Monte Carlo simulation was proposed, and the applicability of this method was verified. The blast load probability model was developed for the scaled distances range from 1 m/kg1/3 to 40 m/kg1/3. The effect of the mass safety factor of 20 % on the probability of exceeding the design blast load was assessed. At last, based on the established probabilistic model for the blast loads, the expression for calculating the load factor of any reliability level at any location was presented. [ABSTRACT FROM AUTHOR]

To investigate the anti-explosion behavior of high-strength reinforced concrete (RC) beam subjected to blast load, the ANSYS/LS-DYNA finite element analysis software was applied. Based on anti-explosion test results, the effects of reinforcement strength grade, reinforcement ratio and stirrup ratio on dynamic response, failure mode, resistance curve and ductility of RC beams under uniform blast load were studied. The anti-explosion performance of RC beam can be effectively improved by increasing the strength grade of the high-strength reinforcement. When the shear capacity is high enough, the ultimate capacity of high-strength RC beam can be significantly enhanced by increasing its reinforcement ratio. Anti-explosion performance may deteriorate due to the change of failure modes when the reinforcement ratio is increased to a certain extent. Increasing stirrup ratio can improve the shear capacity of high-strength RC beam to guarantee the full utilization of the advantage of high flexural capacity. For high-strength RC beam with sufficiently shear capacity, the further increase of stirrup ratio has a slight effect on the anti-explosion ability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The damage and responses of two asphalt pavements under blast loads are simulated. • The proposed simulation methodology is validated based on a real blast test. • A reinforced concrete layer is added to improve the anti-blasting performance. • The proposed anti-blasting pavement structure reduces the damage area by up to 20%. The explosion accidents are threatening the service functionality of pavement structures, which puts forward new requirements such as multi-hazard resistance and resilience. Although the widely used asphalt pavement structure is vulnerable to blast loads, its dynamic behaviors under blast loads are still unclear. This research mainly focused on the damage and responses of two asphalt pavement structures, one of which was conventional asphalt pavement, and the other was the anti-blasting asphalt pavement structure with the reinforced concrete layer. The numerical simulation method, which was validated based on a real blast test, was proposed using Abaqus code with appropriate material models and simulation procedures. The finite element models of two pavement structures were built. Under various blast loads, the damage contours and dynamic responses of different pavement structure components were investigated. It was found that the total damage areas of two asphalt pavement structures were grew by 2.26 and 3.19 times, respectively, as the blast loads increased from 100 kg TNT to 2000 kg TNT. The slope of pavement structure was extremely sensitive to the changes in blast load. The proposed anti-blasting pavement structure could reduce the damage area by up to 20 %, but it would be invalidated under particularly destructive blast loads. These findings could be helpful for the further design of an anti-blasting pavement structure. [ABSTRACT FROM AUTHOR]

This study proposes a blast load model that generates multiple impulse curves with appropriate shapes depending on the scaled distance and, thus, precisely calculates the blast load distribution over the structure surface. The suitability of the proposed model is examined by using the finite element simulation of a blast test with steel plates and comparing the predicted deflections with the measurements. The results reveal that the proposed model accurately calculates the blast load distribution over the structure surface. The predicted deflection profiles of the steel plates are closer to the measured deflection profiles when the proposed model is employed, as compared to the existing models, which produce only a single impulse curve. [ABSTRACT FROM AUTHOR]

In order to prevent structural collapse by terrorist attacks, the column behavior is highlighted since when a column is damaged consequently losing its load bearing capacity, failure will spread to the rest of the structure resulting in the collapse of the entire structure. In this paper, using the reliability theory and taking into account the uncertainties associated with blast loading and material properties, a methodology is improved for determining the damage probability of a steel column under various blast scenarios. Damage is determined according to damage index based on axial load-bearing capacity. The Monte Carlo simulation method is utilized using an explicit finite element method to obtain the failure probability. The results are described in terms of damage probability, effects of boundary conditions, effect of type of probability density function and sensitivity analyses. The results show the importance of considering the uncertainties in assessing the damage index of the columns against explosion. Also, it is found that in the flexural mode the probability of damage decreases as the support condition changes from pinned to fixed ends. Furthermore, the safe protective distances are estimated based on the concept of damage probability. Likewise, results for log-normal random variables are relatively identical with truncated normal random variables. The results of the sensitivity analyses show that damage index has the highest sensitivity to peak reflected pressure. [ABSTRACT FROM AUTHOR]

The objective of the current work is to model a stainless steel (SA 316L) autoclave explosion and rupture that occurred during a research laboratory experiment designed to study the thermal decomposition of ammonium tetrathiomolybdate in the presence of dimethylsulfoxide (DSMO) in the autoclave. A finite element analysis is conducted to better understand the cause of failure of the autoclave and with the objective to investigate whether the incident was caused by static overpressure or an internal blast load. The empirical CONWEP blast loading model is used to model the internal blast load. The constitutive behavior of the autoclave material is modelled using the Johnson-Cook (JC) plasticity and material failure model, which both account for the effect of strain rate and temperature. By conducting uniaxial tensile tests and tests on notched ring specimens cut from the autoclave, the true stress-strain curve and the ductile failure locus of the autoclave material are established, respectively, which are used to obtain the constants of the JC plasticity and failure model, respectively. The result of the finite element analysis revealed that a blast load from an equivalent TNT charge of 0.042 kg, which resulted from the decomposition of DMSO at high temperature, predicted markedly well the structural response and subsequent failure of the autoclave observed in the post-incident investigation. [ABSTRACT FROM AUTHOR]

The main aim of present work is to investigate structural behavior of one-way reinforced concrete slabs retrofitted with fiber reinforced plastic. Retrofitting is done to enhance bending and shear strength, to increase confinement and to repair damages caused by corrosion and cracking. In retrofitting RC slabs FRP is often used to enhance bending strength by putting it on the tensile side of the slab in the region with maximum anchor, which leads to significant increase in slab’s energy absorption capacity. Finite Element Method (FEM) is widely used in different fields for structural, electrical, heat, and mechanical engineering. In the case of blast analysis, due to excessive cost, the danger of experiments and extremely short duration of the test, numerical simulation is more attractive. Explicit dynamics analysis procedure based on the implementation of an explicit integration rule together with the use of diagonal (“lumped”) element mass matrices is used, which is computationally efficient for the analysis of large models with relatively short dynamic response and for the analysis of extremely discontinuous events or processes. Computer code ABAQUS is used for the analysis and the results are compared with available experimental results in the literature and good agreement has been observed. Also it can be concluded that numerical method used in this study has good agreement with experimental work. Influence of different geometrical parameters including number of layers, orientation of the fibers and the aspect ratio of slab has been investigated. Upon comparison with available experimental results, it is shown that modeling techniques have good accuracy. It is found that regardless of the orientation of the fibers, displacement of the center of slab would be reduced significantly. When fibers orientation angle with respect to the main load bearing direction of the slab is [-20°, 20°], the blast strength of the slab is maximum. For slabs with low aspect ratio, the more the number of layers, the higher the blast strength. For slabs with high aspect ratio, there is no significant difference between different fiber arrangements and increasing number of layers has no significant effect on blast strength of slabs. [ABSTRACT FROM AUTHOR]

In recent years, frequent terror and military attack by explosion and impact have occurred all over the world. Particularly, World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001 and Fukushima nuclear power plant accident due to Northeast earthquake tsunami on the coast of Japan on Mar. 11 of 2011 resulted in devastating human casualties and structural collapses. These terrors and accidents raised public concerns and anxiety of potential structural collapse of major infrastructures and structures. In order to better combat these problems, the extreme loading resistant structural studies are initiated. Among numerous types of target structures, one of the most important structural types is prestressed concrete (PSC), which is widely used for construction of nuclear containment vessel and gas storage tank. In this study, to evaluate the blast resistance and protective capacity of bi-directional PSC member, blast tests were carried out on 1400 × 1000 × 300 mm reinforced concrete (RC), prestressed concrete without rebar (PSC), prestressed concrete with rebar (PSRC) specimens. The applied blast load was generated by detonating 25 kg ANFO explosive charge at 1.0 m standoff distance. The data acquisitions included blast waves of incident pressure, reflected pressure, and impulse as well as behavioral displacements of deflection, acceleration, and strains of concrete, rebar, and PS tendon. Then, the blast test results are used to calibrate finite element simulation model. Once the simulation model is calibrated, it is used to perform parametric study on bi-directional prestressed concrete specimens to further evaluate the blast resistance of the panels. The study results are discussed in detail in the paper. [ABSTRACT FROM AUTHOR]

• Field blast tests and axial compression tests reveal a significant decrease in the axial bearing capacity of the shallow-buried RC tunnel subjected to blast loads. • Numerical simulation algorithms and material models are verified by field blast test and post-blast axial compression test results. • The shallow-buried RC tunnel exhibits different damage modes under different blast scenarios. • The damage degree of a shallow-buried tunnel is sensitive to the explosive weight and detonation point. • The blast vulnerability of a shallow-buried tunnel under blast load is investigated. The purpose of this investigation is to analyze the failure probability of a blast in a shallow RC tunnel. The field blast tests are carried out, and a refined finite element model (FEM) is established based on LS-DYNA. To account for blast uncertainty, the Monte Carlo method is used to determine 150 blast conditions. A failure evaluation method based on a mechanical performance index is proposed. The probabilistic blast demand model (PBDM) and the probabilistic blast capacity model (PBCM) are established. Finally, a probability assessment framework based on the structural performance index and the vulnerability curve for shallow tunnels are established. According to the findings, when the mass of TNT in the tunnel exceeds 300 kg, the tunnel is in danger of collapsing. At this moment, it is suggested that people enter the tunnel cautiously. The vulnerability curve predicts the failure probability of a tunnel under various blast loads. At the same time, it could assess its structural performance after the disaster. [ABSTRACT FROM AUTHOR]

This paper presents a new approach – using analytical solution to investigate nonlinear dynamic response and vibration of imperfect functionally graded carbon nanotube reinforced composite (FG-CNTRC) double curved shallow shells. The double curved shallow shells are reinforced by single-walled carbon nanotubes (SWCNTs) which vary according to the linear functions of the shell thickness. The shells are resting on elastic foundations and subjected to blast load and temperature. The shell's effective material properties are assumed to depend on temperature and estimated through the rule of mixture. By applying higher order shear theory, Galerkin method and fourth-order Runge–Kutta method and the Airy stress function, nonlinear dynamic response and natural frequency for thick imperfect FG-CNTRC double curved shallow shells are determined. In numerical results, the influences of geometrical parameters, elastic foundations, initial imperfection, temperature increment and nanotube volume fraction on the nonlinear vibration of the FG-CNTRC double curved shallow shells are investigated. The proposed results are validated by comparing with those of other authors. [ABSTRACT FROM AUTHOR]

To study the effect of blast pressure on structural resistance against progressive collapse under column removal scenario induced by contact detonation, and to investigate the development of catenary action within ultra-fast dynamic regime, a physics-based finite element model is developed in this paper. The model is first validated by a quasi-static test series on reinforced concrete sub-assemblages under middle column loss assumption and a blast test series using the same structural configurations. The sub-assemblage included a two-span beam, a middle column stub and two column stubs at both sides. Besides validations with sub-structure tests, some pull-out tests are also performed to verify the numerical models. After the verifications, parametric studies are conducted to investigate the influence of important dynamic and structural factors such as the boundary stiffness, damping ratio, and charge weight attached to the middle column. The study shows that under actual blast conditions, catenary action in sub-assemblages can be mobilised to prevent a structure from collapse even when the bottom longitudinal reinforcement in the bridging beam has already fractured. Moreover, stiffness of horizontal restraints plays an important role to mitigate disproportionate collapse in both static and blast conditions. A comparison is also made between nonlinear dynamic procedure and nonlinear static analysis incorporating simplified energy method for dynamic assessment. It is concluded that the simplified static approach in lieu of dynamic analysis can be considered as a conservative method for practical design purpose. Nonetheless, this method may over-estimate structural resistance if the localised damage is induced by a contact-detonation event. [ABSTRACT FROM AUTHOR]

Mitigation of blast effects caused by accidental explosions is one of the major challenges in structural engineering. Fiberreinforced polymer (FRP) sandwich panels offer promising systems for blast mitigation applications due to their considerable energy absorption compared to other materials with similar density. The FRP sandwich panels can have different inner core configurations that can be filled with other materials whenever needed. This paper numerically evaluates the effectiveness of new FRP honeycomb sandwich panels in resisting blast loads. A numerical model has been created using nonlinear explicit finite element simulation. Then, the model has been validated using the experimental field tests in the literature. Twelve FRP panels with different inner core configurations have been proposed to enhance the panels' performance by reducing their peak deformation and increasing their energy dissipation. The paper also investigates the effect of filling the FRP sandwich panels with sand on the panels' blast resistance. The analyses have shown that the FRP panels utilizing the new core configurations are able to dissipate more than twice the energy compared to the experimental panels with even less deformations. It has been found that using sand as a filling material provides a damping medium that enhances the panels' behavior under blast effect. [ABSTRACT FROM AUTHOR]

• The nonlinear blast response of one-way arching masonry walls is studied. • A combined methodology of laboratory testing and nonlinear modeling is presented. • The dynamic arching force is experimentally quantified. • Comparisons between the model and the test results show a good agreement. • The effect of the boundary conditions on the dynamic response is explored. This paper studies the nonlinear dynamic response of arching masonry walls to blast load. The methodology combines laboratory blast testing and nonlinear dynamic modeling of arching one-way masonry walls and their response to blast load. The paper aims at enhancing the understanding of the dynamic and nonlinear physical response of the structural system. The experimental phase focuses on a one-way arching masonry wall tested in a blast simulator. The test is designed to explore global and local measures of the response of such walls. New experimental data that contributes to the understanding of the blast response and for validating theoretical and numerical models is presented. The theoretical phase develops a nonlinear, dynamic, continuous beam-type model that considers the deformability of the mortar joints and the masonry units. The model combines inertial effects with geometrical and material nonlinearities and uses the finite element method for the numerical solution. The model is examined and evaluated against the experimental benchmark, and then it is used to explore the impact of the boundary conditions and the blast intensity on the dynamic response. The combined investigation highlights, explores, and quantifies the unique aspects of the complex dynamic response of such walls to blast loading. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to use the combination of the edge-based smoothed finite element method (ES-FEM) and mixed interpolation of tensorial components triangular (MITC3) element. As a result, the so-called ES-MITC3 element is proposed for the dynamic analysis of sandwich plates with a functionally graded porous (FGP) core subjected to blast load. Sandwich plates include a bottom layer made of homogeneous metal, an all-ceramic top layer and a FGP core layer with uneven porosity distribution. The ES-MITC3 element is created to enhance the accuracy and convergence of the MITC3 element as well as the traditional triangular element. Employing Hamilton's principle, governing equations of sandwich plates are inferred. Then, solving linear differential equations is conducted by using the Newmark-beta approach. A few studies are conducted to confirm the performance of the current method. Finally, the new numerical results on the vibration characteristic of sandwich plates are provided. [ABSTRACT FROM AUTHOR]

Nonlinear response of laminated composite plates and cylindrical panels subjected to a parabolically distributed blast load is studied here using a shear deformable finite element method. The nonlinear finite element equations of motion are solved in the time domain by an energy and momentum conserving time integration technique. The state-of-stress inside the laminated panels is calculated at each time-step to predict the occurrence of damage using Tsai-Wu quadratic failure criterion. The effects of span-to-thickness ratio, radius-to-span ratio and peak pressure on the nonlinear dynamic response of laminated composite plates and curved panels are investigated. [ABSTRACT FROM AUTHOR]

Significant research efforts have been invested on studying the response and damage of structures subjected to blast loads for better life and property protections. The single-degree-of-freedom (SDOF) approach has been widely adopted to simplify the structural response analysis for engineering design purpose. However, such an approach under certain circumstances oversimplifies the structural behavior and might not give reliable predictions of structural responses to blast loads. On the other hand, although detailed high fidelity finite element (FE) approach is able to give relatively accurate predictions of structural response, it is unfortunately not straightforward for application and very time-consuming, which impedes its application among engineers. Therefore, a method that can assure not only reliability but also efficiency is highly needed for design practice. In the present study, mode approximation method with Pressure-Impulse (P-I) diagrams is applied to analyze response and damage of RC slab due to blast load. Slab under analysis is assumed rigid-plastic and simply supported. Shear failure, bending failure and combined failure modes are considered based on different failure modes. Critical equations for structural shear and bending failures are derived respectively with appropriate failure criteria. P-I diagrams are then developed for quick damage assessments. The analytical results are verified by comparing with high fidelity numerical simulations. The reliability and efficiency of using this approach for design and analyzing RC slab response under blast loads are demonstrated. [ABSTRACT FROM AUTHOR]

A novel multilayer façade system, which consisted of a water steel tank integrated with a layer of energy absorbing aluminum foam panel and a stiffened steel panel, was developed to resist blast loading. The blast resistance and response behavior of the proposed façade system were investigated using nonlinear finite element method. The accuracy of the numerical model was verified by comparing the predicted results with the test results. The analyses showed that the energy absorbing aluminum foam layer was capable of reducing the blast load acting on the façade panel and building. The blast resistance of the multilayer façade system could be further enhanced by increasing the aluminum foam layer thickness. An analytical model considering Dynamic Increase Factor (DIF) and coupled deflection mode shapes was developed to predict the displacement response of the façade system subjected to blast loading. The accuracy of the analytical model was validated by comparing the predicted results with the numerical results. It was found that the analytical model with varying DIF could provide better prediction of the displacement response of the multilayer water façade system as compared to the method using a constant DIF. [ABSTRACT FROM AUTHOR]

Increase of terrorist attack in the present time detects necessity of retrofitting of existent structures or design of new structures which can resist blast loads. In this research, a shear concrete wall subjected to explosive load will be analytically investigated. CFRP sheets will be applied for retrofitting the wall, and its performance in strengthening of the wall will be studied. Also a kind of shear composite wall is modeled and analyzed under the blast load. Results are compared, and advantages and disadvantages of these types of walls will be represented. Validation of analytical simulation is done by modeling of two experimental tests and good agreements have been obtained. Results show that pasting every other CFRP layers in vertical manner will increase performance of the wall as well as warping the entire wall by CFRP sheets. External reinforcement by CFRP will significantly improve energy absorption of the wall comparing use of steel sheets. Also, increase of number of layers causes consideration improve in energy damping and negligible effect on wall displacement. [ABSTRACT FROM AUTHOR]

Three different human head models in a free space are exposed to blast waves coming from four different directions. The four head–neck–body models composed ofmodel a,with the neck free in space;model b,with neck fixed at the bottom; andmodel c,with the neck attached to the body. The results show that the effect of the body can be ignored for the first milliseconds of the head–blast wave interactions. Also one can see that although most biomechanical responses of the brain have similar patterns in all models, the shear stresses are heavily increased after a few milliseconds inmodel bin which the head motion is obstructed by the fixed-neck boundary conditions. The free-floating head model results are closer to the attached-body model. [ABSTRACT FROM PUBLISHER]

This article presents the experimental and numerical study carried out to capture the response of metallic sandwich plate when subjected to air blast loads. A full scale field test is carried out on a sandwich panel with tetrahedral truss core, subjected to the action of pressure waves originating from the detonation of high explosive charges. The time history of acceleration and blast overpressure at the centre of the plate is recorded. An explicit finite element analysis is performed on the sandwich panel with identical geometry. Blast loading is applied usingCONWEPcode. Very good agreement has been observed between the numerical and experimental results. A systematic parametric study is conducted by varying the geometrical and loading parameters of the panel. Performance of panel under blast load is judged on the basis of sandwich panel efficiency. It is observed that geometrical parameters have significant effects on the panel response for varying load. For a fixed core cross section and face sheet thickness, highest panel efficiency is obtained corresponding to a core height of 140 mm. [ABSTRACT FROM AUTHOR]

Problems involving forced transverse vibrations of beam-columns have many applications in different fields of engineering. This paper presents an analytical procedure allowing the prediction of the blast dynamic response of a beam-column to a combined action of axial and transverse loads. The solution is based on the continuous formulation and the Euler–Bernoulli beam theory. The response of the beam-column in the quasi-static, dynamic and impulsive regimes is analysed using the developed analytical model. The analysis shows that the number of modes of vibration needed to produce an accurate estimate of the beam-column behaviour may vary depending on the loading regime. Various types of spatial load distributions and time histories of transverse loads commonly used in engineering practice for modelling of extreme loads are discussed. The significance of the axial force and the shape of the transverse load time history for the beam-column response is shown using the response spectrum and pressure–impulse diagram methods. The initial imperfections in the beam-column geometry and applied loads are introduced into the analysis and their effects are also examined. The results obtained by the analytical model are compared to the results of a nonlinear finite element analysis performed in ABAQUS. Certain discrepancies between the beam-column response yielded by the analytical solution and the finite element model were observed at high levels of axial force and quasi-static transverse loading conditions. [ABSTRACT FROM AUTHOR]