Uniform Blast Load Research Articles

Dynamic Response of Fiber-Metal Laminates Sandwich Beams under Uniform Blast Loading.

In this work, theoretical and numerical studies of the dynamic response of a fiber-metal laminate (FML) sandwich beam under uniform blast loading are conducted. On the basis of a modified rigid-plastic material model, the analytical solutions for the maximum deflection and the structural response time of FML sandwich beams with metal foam core are obtained. Finite element analysis is carried out by using ABAQUS software, and the numerical simulations corroborate the analytical predictions effectively. The study further examines the impact of the metal volume fraction, the metal strength factor between the metal layer and the composite material layer, the foam strength factor of the metal foam core to the composite material layer, and the foam density factor on the structural response. Findings reveal that these parameters influence the dynamic response of fiber-metal laminate (FML) sandwich beams to varying degrees. The developed analytical model demonstrates its capability to accurately forecast the dynamic behavior of fiber-metal laminate (FML) sandwich beams under uniform blast loading. The theoretical model in this article is a simplified model and cannot consider details such as damage, debonding, and the influence of layer angles in experiments. It is necessary to establish a refined theoretical model that can consider the microstructure and failure of composite materials in the future.

Dynamic plastic response of sandwich structures with graded polyurethane foam cores and metallic face sheets exposed to uniform blast loading: experimental study and numerical simulation

Dynamic plastic response of sandwich structures with graded polyurethane foam cores and metallic face sheets exposed to uniform blast loading: experimental study and numerical simulation

Research on vibrational characteristics of nanocomposite double-variable-edge plates immersed in liquid under the effect of explosive loads

The paper presents the free vibration as well as the nonlinear behaviors of a new plate structure which the authors call double-variable-edge (DVE) plates in contact with fluid under the impacts of uniform time-dependent blast load. The used material is laminated functionally graded graphene-reinforced composite (FG-GRC) described by the extended Halpin-Tsai micromechanical model. Based on the classical plates theory (CPT), the governing motion system of equation is established and then the dynamical behaviors of the system are investigated by solving the ordinary differential equations. The velocity potential function and along with Bernoulli's equation is employed to obtain the hydrodynamic pressure on the plate-fluid interface while the blast load is modeled by Friedlander's equation. The CPT shows the convenience in analyzing the dynamic characteristics of complex shape plates, the results are compared with outcomes of previous articles and the Finite Element Analysis (FEA) to confirm the accuracy and reliability of present works. Some influences of materials, geometrics, temperature environment and fluid are given through numerical and graphical results. The current outcomes have great potential for the application of aerospace, ocean, civil engineering, and military fields such as: submarines, diving equipment, UAV or space exploration equipment.

Repeated uniform blast loading on welded mild steel rectangular plates

The present research paper deals with a combined experimental and numerical assessment of the deformation mode and failure mechanism of welded rectangular plates exposed to three successive uniform blast loading. To perform the experimental study, three different categories of 0 W (a plate without any weld seam), 1 W (a plate with a single weld seam), and 2 W (a plate with double weld seams) were conducted and mounted onto the ballistic pendulum apparatus. The effect of the number of blasts, the number of weld seams, and the explosive charge mass was investigated on the structural dynamic response. Unlike 0 W plates, plates with double weld seams experienced large plastic deformation along with small thinning happening at the long side clamped boundary. Therefore, despite increasing the deformation resistance, the welding lines tended to mitigate the damage tolerance of the tested mild steel plates. To gain more insight into the influence of two other key parameters like the position of the weld seam and its orientation on the dynamic response and energy absorption capacity, numerical simulations were also performed using the ABAQUS/Explicit finite element solver in conjunction with the inbuilt ConWep blast function code. For modeling the amplified blast wave produced by the detonation of the explosive charge, the scaling factor of 4.1 was adopted. Due to the welding process on the tested plates, the material degradation at the Heat-Affected Zone (HAZ) was also incorporated into the simulation by obtaining the knockdown factor from quasi-static tensile tests on unwelded and welded specimens. An excellent agreement between experiments and simulation results was achieved in terms of the impulse of the applied load and central permanent deflection. Furthermore, the present paper provides the primary experimental data and numerical simulation support for the blast resistance design of metallic structures using welded specimens.

Numerical Simulation of Blast Loaded CFRP Retrofitted Steel Plates

This paper reports on the results of a numerical study to simulate the response of carbon fibre reinforced polymer (CFRP) retrofitted steel plates to applied blast loads using finite element software, LS-DYNA. The results of the simulation were validated against plate response and magnitude of deformation obtained from previous experiments. The uniform blast load was generated in the experiment by detonating a cylindrical charge down the end of a square tube. The finite element code LS-DYNA was used to simulate the structural response of the respective blast structures. For the numerical model, the blast load was simulated using the mapping feature available in LS-DYNA for the multi-material arbitrary Lagrangian-Eulerian (MM-ALE) elements which significantly reduced the size of the air domain in the model. The simulations showed a satisfactory correlation with the experiments for the blast results and post-failure deformations that occurred in CFRP retrofitted steel plates.

BEHAVIOR OF STEEL HOLLOW SECTIONS UNDER BLAST LOAD

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.

Study on Anti-Explosion Behavior of High-Strength Reinforced Concrete Beam Under Blast Loading

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.

Numerical analysis of cladding sandwich panels with tubular cores subjected to uniform blast load

This article presents the results of a numerical study on the response of cladding sandwich panels with tubular cores that can be used as blast mitigators. The core of the cladding sandwich panels consisted of empty thin-walled aluminum circular tubes (38 mm in diameter) riveted laterally between the skin plates in different configurations (varying number of tubes and spacing between the tube). The skin of cladding sandwich panels consisted of a “rigid” DOMEX700 steel front plate which was exposed to the blast load and a back plate made of mild steel. The uniform blast load was achieved by detonating varying charge masses of explosive (ranging from 6 g to 50 g) at a stand-off distance of 200 mm down a square mild steel tube. The numerical model, developed in ANSYS AutoDYN 15.0, was validated for average deflection of the front plate and crush mode of the tubular cores using the experimental results that were presented in a previous paper [1]. The results of the simulations provided insights into the transient response of the cladding panels. The effects of the spacing between the tubular cores which also influenced the interaction between the tubular cores were also investigated. The number of plastic hinges formed was increased whilst the rotation angle of plastic hinges decreased with increasing interaction between the tubular cores.

Analysis Method for Reinforcing Circular Openings in Isotropic Homogeneous Plate-Like Structures Subjected to Blast Loading

An analysis method is formulated to predict the peak bending stress concentrations around a small circular opening in an idealized isotropic homogeneous, linear elastic-perfectly plastic plate-like structure subjected to uniform blast loading. The method allows for the determination of corresponding concentrated bending moments adjacent to the opening for the design of reinforcement that can prevent the formation of localized plasticity around the opening during a blast event. The rapid formation and growth of localized plasticity around the opening can lead to a drastic reduction of the plate-like structure’s local and global stability, which could result in catastrophic failure of the structure and destruction of the entity it is protecting. A set of elemental formulas is derived considering one-way and two-way rectangular plate-like structures containing a single small circular opening located where flexure predominates. The derived formulas are applicable for elastic global response to blast loading. Abaqus was employed to conduct numerical verification of the derived formulas considering various design parameters including material properties, plate dimensions, position of opening, and explosive charge size. The formulas demonstrate a good correlation with FEA albeit with a conservative inclination. The derived formulas are intended to be used in tandem with dynamic SDOF analysis of a blast load-structure system for ease of design. Overall, the proposed method has the potential to be applicable for many typical conditions that may be encountered during design.

Damage Assessment of an RC Pier under Noncontact Blast Loading Based on P‐I Curves

Since the 9.11 attacks in New York, terrorist attacks, military strikes, and accidental explosions have caused serious damage to various infrastructures around the world. Accidental traffic explosions in bridge engineering have occurred frequently due to the increasing firework truck on the bridge and heavy fuel oil ships under the bridge. Besides, intentional car bomb explosions in terrorist attacks and military assaults are significant threats to the bridge structure. Bridge pier is a particularly important component of the overall bridge structure due to its vertical support capacity. Therefore, the damage of reinforced concrete (RC) piers under blast loading should be studied. In this paper, the pier is simplified as a single degree of freedom (SDOF) system based on energy equality, and the blast loading distribution on the surface of the pier is simplified as a uniform distribution. Then, the P‐I curves of an RC pier are obtained based on the SDOF system and a uniform distribution blast loading to quickly evaluate the damage extent of an RC pier so that the P‐I curves and fitting formulas for different damage extents can be used for practical engineering. After a numerical simulation verification, the P‐I curves and fitting formulas based on the simplified method can supply a rapid and effective method for engineers to assess the postexplosive damage of an RC pier.

Blast response of cladding sandwich panels with tubular cores

This paper reports on the response of cladding sandwich panels with tubular cores to uniform blast load. The core of the cladding sandwich panels consisted of empty or foam-filled thin-walled circular tubes (38mm in diameter) made from either aluminium 6063-T6 or mild steel riveted laterally between the skin plates at varying spacing arrangements. The tubular cores were arranged to provide four different types of panels. The front plate skin of the panel, exposed to the blast load, was made from DOMEX 700 Steel while the back plate skin was made from mild steel. Three types of polymeric cellular foams, namely self-raising polyurethane, expanded polystyrene and cross-linked polyethylene, were used to fill the circular tubes. The “uniform” blast load was achieved by detonating varying charge masses of explosive (ranging from 6g to 50g) with a prescribed load diameter of 40mm at a stand-off distance of 200mm down a square tube. Energy was dissipated mostly through the plastic deformation of the tubular cores. The foam added extra energy absorbing capacity. The results showed an increase in average deflection with an increase in charge mass/impulse for the different types of panels. The cladding panels with the least interaction between the tubular cores were observed to have the highest energy absorption capabilities for a given charge mass.

Nonlinear dynamic analysis of tapered sandwich plates with multi-layered faces subjected to air blast loading

The nonlinear dynamic behavior of simply supported tapered sandwich plates subjected to air blast loading is investigated theoretically and numerically. The plate is supposed to have both tapered core and tapered laminated face sheets and be subjected to uniform air blast load. The theory is based on a sandwich plate theory, which includes von Karman large deformation effects, in-plane stiffnesses, inertias and shear deformations. The sandwich plate theory for plates with constant thickness which have one-layered face sheets found in the literature is developed to analyze the tapered sandwich plates with multi-layered face sheets. The equations of motion are derived by the use of the virtual work principle. Approximate solution functions are assumed for the space domain and substituted into the equations. The Galerkin method is used to obtain the nonlinear differential equations in the time domain. The finite difference method is applied to solve the system of coupled nonlinear equations. The tapered sandwich plate subjected to air blast load is also modelled by using the finite element method. The displacement–time and strain–time histories are obtained. The theoretical results are compared with finite element results and are found to be in an agreement.

Response of Sandwich Panels with Tubular Cores to Blast Load

This paper reports on the response of cladding sandwich panels with tubular cores to uniform blast load. The panels consist of thin-walled circular tubes (38 mm in diameter) made from aluminium 6063-T6 riveted laterally between the skin plates at varying spacing arrangements to provide four different types of panels. The skin exposed to the blast load is made from DOMEX 700 Steel while the back face skin is made from mild steel. Varying charge masses of explosive (ranging from 5 g to 40 g) with a prescribed load diameter of 40mm is detonated at a stand-off distance of 200 mm to provide a “uniform” blast load to the sandwich panels. Energy is dissipated mostly through the plastic deformation of the tubular cores. The results show an increase in average deflection with an increase in charge mass/impulse for the different types of panels. The cladding panels with the least interaction between the tubular cores are observed to have the highest energy absorption capabilities for a given charge mass.

The response of circular plates to repeated uniform blast loads: An experimental and numerical study

This paper presents the results of an experimental and numerical investigation into the response of circular Domex-700 MC steel plates to repeated uniform blast loads. The Domex 700 steel tests plates of thickness either 2 or 3 mm are mounted onto a ballistic pendulum and subjected to uniform blast load up to five times for repeated loading. In general, the plates show large inelastic global deformation with thinning occurring at the clamped boundary and in some cases tearing. A trend of increasing permanent mid-point deflection is observed for an increase in charge mass and number of witnessed blast loads. The results also show a decrease in the incremental mid-point deflection and an increase in the Vickers hardness of the plate at the boundary and central region with increasing number of witnessed blast loads. Numerical simulations are carried out to gain further insight into the deformation of plates subjected to repeated blast loading using ABAQUS/Explicit v6.10.1 in conjunction with the inbuilt blast function code, ConWep. A scaling factor is adopted to model the amplified blast wave resulting from the detonation of cylindrical charges at one end of a cylindrical tube. Very good correlation is obtained with regards to midpoint deflection and deformation profiles. The plastic strain obtained numerically shows good qualitative correlation with the experimental Vickers hardness tests.

Numerical dynamic analysis of stiffened plates under blast loading

Using the general purpose finite element package Abaqus, an investigation has been carried out to examine the dynamic response of steel stiffened plates subjected to uniform blast loading. The main objective of this study is to determine the dynamic response of the stiffened plates considering the effect of stiffener configurations. Several parameters, such as boundary conditions, mesh dependency and strain rate, have been considered in this study. Special emphasis is focused on the evaluation of midpoint displacements and energy of models. The modeling techniques were described in details. The numerical results provide better insight into the effect of stiffener configurations on the nonlinear dynamic response of the stiffened plates subjected to uniform blast loading.

Study of Pressure-Impulse Diagrams for Reinforced Concrete Columns Using Finite Element Analysis

The failure of reinforced concrete columns when subjected to blast events can be catastrophic to the building as a whole. The choice of the type of lateral confinement may influence the response of columns subjected to blast load much more when compared to the application of traditional loads. The objective of the research reported in this paper is to study the non-linear response of a typical reinforced concrete column with four types of lateral reinforcement subjected to uniform blast loading, using finite element (FE) and single degree of freedom (SDOF) methods. An advanced FE modeling tool, LS-DYNA and a widely used SDOF analysis tool – SBEDS – are used for this purpose. Pressure-Impulse (PI) diagrams for different levels of protection (LOP) are developed using both the methods. The mid height displacement is used to represent the levels of protection. A parametric analysis is used to develop PI diagrams in order to study the effect of confinement on the reduction of displacement at impulsive, dynamic, and quasi-static loading conditions. PI curves developed from the FE methods are compared with the curves from the SDOF methodology. Regression equations are also developed using statistical analysis, to characterize PI diagrams generated from the FE method. Recommendations for analysis, design and detailing of reinforced concrete columns for blast protection based on this research are presented.

A new SDOF method of one-way reinforced concrete slab under non-uniform blast loading

A new effective model for calculation of the equivalent uniform blast load for non-uniform blast load such as close-in explosion of a one-way square and rectangle reinforced concrete slab is proposed in this paper. The model is then validated using single degree of freedom (SDOF) system with the experiments and blast tests for square slabs and rectangle slabs. Test results showed that the model is accurate in predicting the damage level on the tested RC slabs under the given explosive charge weight and stand-off distance especially for close-in blast load. The results are also compared with those obtained by conventional SDOF analysis and finite element (FE) analysis using solid elements. It is shown that the new model is more accurate than the conventional SDOF analysis and is running faster than the FE analysis.

Transverse blast loading of hollow beams with square cross-sections

A model of deformation of a metal hollow section beam under a uniform blast loading is developed in order to reveal the characteristic features of deformation and energy absorption of hollow section beams under such loading. It is established that as a typical structural component a hollow section distinguishes itself from its solid counterpart with two characteristic features of the response. First, a considerably larger kinetic energy is generated in the hollow section beam as the impulsive load is imparted on the upper flange of the beam having a significantly lower mass than the member. Second, a considerable proportion of the blast energy can be absorbed by the local collapse of the section. A two-phase analytical model is proposed. In the first phase, the local collapse of the thin-walled cross-section is determined by using an upper bound approach; and in the subsequent second phase, the global bending of the beam with the distorted section is analyzed by taking into account the effect of axial force. It is demonstrated that mass distribution in the hollow section is an important factor in determining the energy partitioning between the local deformation phase and global bending of the hollow beam. Reasonable agreement is obtained with the experimental data published in the literature [Jama HH, Nurick GN, Bambach MR, Grzebieta RH, Zhao XL, Steel square hollow sections subjected to transverse blast loads, Thin-Walled Structures 2012;53:109–122].

Dynamic response of composites sandwich plates with carbon nanotubes subjected to blast loading

An experimental study of the dynamic response of composite aluminum epoxy resin–CNT sandwich plates subjected to blast load is presented in this paper. The sandwich plates consist of aluminum square plates with a core of epoxy resin matrix and 5% in weight of CNT. For comparison purposes, plates with neat epoxy resin core were also tested. Disc shaped plastic explosive (PE4) is used to impart uniform and localized blast loading to the plates. The mass of the explosive is varied to provide a range of response of the sandwich panels from plastic deformation to complete tearing. It was found that the permanent displacement is larger for the plates with CNTs, as for uniform well as localized blast loading, indicating that the inherent brittleness of epoxy resins was overcome by adding CNTs. On the other hand, once the composite material with CNTs has reached the fracture, it is exhibited better energy dissipation behavior than the neat epoxy specimens. Preliminary results show that the failure load is larger for the specimens with CNTs.

A new non-uniform blast load model for SDOF method of one-way reinforced concrete slab

A new effective model for calculation of the equivalent uniform blast load for non-uniform blast load such as close-in explosion of a one-way square and rectangle reinforced concrete slab is proposed in this paper. The model is then validated using single degree of freedom (SDOF) system with the experiments and blast tests for square slabs and rectangle slabs. Test results showed that the model is accurate in predicting the explosive charge weight and stand-off distance to impose a given damage level on the tested RC slabs especially for close-in blast load. It is shown that the new model is more accurate than the conventional SDOF analysis and is running faster than the FE analysis.