Effect Of Blast Loading Research Articles

Experimental Validation and Numerical Analysis of a High-Performance Blast Energy-Absorbing System for Building Structures

The paper presents a full-scale blast testing experimental campaign conducted on an energyabsorbing connector comprising thin-walled inversion tubes as kernel elements mounted in a façade protective panel. LS-DYNA finite element predictions of the global and local deformation/inversion of the panel/connectors compared reasonably well with the experimental observations. After validation, the numerical model was used to analyze the response of a simple idealized reinforced concrete structure under three blast-loading scenarios: the first two scenarios produce, approximately, the same impulse but are significantly different in terms of load duration and overpressures, and represent a far-field and a near-field scenario (1600 kg TNT at 20 m (i) and 150 kg TNT at 5 m (ii), respectively); the third scenario is more demanding, and consists in a half standoff distance of the second (150 kg TNT at 2.5 m (iii)). These numerical simulations allow to assess the effect of standoff distance and blast loading on the effectiveness of the protective system. One may conclude that the introduction of EACs strongly limits the forces imparted to the protected structure, reducing significantly the corresponding energy absorption demand. Comparing the energy absorbed by the structure in different scenarios, with and without the protective system (8 × ϕ64 × 2 mm), one can see that these reductions can reach, respectively 67%, 72% and 68% in the far-field, near-field and very near-field explosions.

The Influence of Adiabatic Heat and Combined Blast Load and Fire Loading on the Response of Mild Steel Plates

This paper study the influence of adiabatic heat and fire loading on the behaviour of unstiffened mild steel plates subjected to close-in blast loads using finite element (FE) analysis. A quarter-symmetry 3D FE model consists of the steel plate, clamps and bolts was developed using Abaqus/CAE. Classical plasticity model was used as the material model in the steel plate and bolts. The clamps were assumed as an elastic material. Temperature-material properties relationship according to Eurocode 3 and Masui model was assigned to the steel plate. Conwep function was used to simulate the blast loads. The influence of strain rates was considered in the steel plate using the Cowper-Symonds equation. The FE model of the unstiffened plates was verified and validated against experimental data from literature, where a good agreement was achieved. The results suggest the adiabatic heat in the steel plates does not significantly influence the behaviour of the steel plates in both temperature-material properties models. The study then investigated the effect of combined blast loads and fire loading on the response of steel plates. The fire loading was applied by increasing the temperature in the steel from 200 °C to 1000 °C. Excessive deformation and thinning of the plate at the central area of the plate was observed. The thinning at the central area is pronounce than the thinning of the plate at the boundary between the clamp and the steel plate. Hence, the FE analysis suggests that the failure might occur at the central area of the plate, which could suggest a tearing type of failure. This type of failure is common in plates subjected to close-in blast loads. Therefore, this study has shown that the effect of adiabatic heat is insignificant, and the combined blast-fire loading might cause a similar type of failure as in plates subjected to blast loads only.

Performance of thin blast-loaded steel plates after ballistic impact from small-arms projectiles

It is known from real blast-load events that the combined effect of fragment impact and blast loading is more severe than the effect of the blast loading alone. The present study investigates this effect by comparing the blast response of thin steel plates pre-damaged by either ballistic impacts or idealized pre-cut circular holes under similar blast loading conditions. The ballistic impacts were performed with a rifle, firing 7.62 mm APM2 projectiles, and the subsequent blast loading was applied in a shock tube facility. During the blast tests, pressure measurements and two high-speed cameras were used to record the dynamic response of the target plates and allowed for a reliable experimental procedure. To investigate the strength-ductility trade-off dilemma of the material during extreme loading, three different steels with different levels of strength and ductility were used in the tests. Numerical simulations were conducted in an attempt to obtain more insight into the fracture characteristics of the plates.For similar loading conditions and material, the target plates exposed to ballistic impact showed a reduced resistance to fracture during blast loading compared with target plates containing pre-formed circular holes. As for the effect of material strength and ductility, the global deformation decreased, while the localization of plasticity increased, with an increased material strength. The fracture resistance was also observed to decrease with increased material strength. The numerical models were able to capture the main trends observed in the physical tests, i.e., a decrease in fracture resistance with initial ballistic impact, and a reduction in fracture resistance with increased material strength. The numerically predicted crack paths also showed a strong dependence upon the initial cracks caused by the petals from the ballistic impacts.

Study on the liquefaction characteristics of saturated sands by millisecond delay blasting

The liquefaction in saturated sands under blast loading is an important research topic in geotechnical engineering. The effect of blast loading on the liquefaction characteristics of saturated sands was studied through a large-scale millisecond delay blasting (MDB) liquefaction field test. Based on the field test, a numerical model was established by the LS-DYNA finite element program to study the propagation of blast waves and the effects of explosive mass, scaled distance, and blast delay on the liquefaction characteristics of saturated sands. The results show that there was a significant sand boiling phenomenon in saturated sands under blast loading, and high values of the excess pore water pressure ratio were observed at monitoring points during the field test. The numerical simulation results show that the scaled distance and the blast delay significantly affected the excess pore water pressure. While the blast delay increased from 110 ms to 330 ms, the excess pore water pressure of the central area can increase by more than 18%. Based on the field and numerical tests, an empirical equation is established that can take into account both the scaled distance and blast delay, which provides a theoretical basis for future large-scale liquefaction sites by MDB.

Performance of Shape Memory Alloy Lead Rubber Bearing (SMA-LRB) Isolated Building Under Blast-Induced Ground Motion Considering Parametric Uncertainty

Blast-induced ground motions (BIGM) can cause significant damage to the structure, leading to loss of life and economy. Previous studies proposed the use of base isolation system to prevent such adverse effects of blast loading on the structures. This study explores the effect of parametric uncertainty on the performance of shape memory alloy-assisted lead rubber bearing (SMA-LRB) isolator for the vibration control of building, under the BIGM. Nonlinear time-history analyses are performed to estimation responses, and compared them with the LRB isolated building. The building is modeled as a linear system, and nonlinear force–displacement behavior of LRB and SMA has been modeled via Bouc–Wen model and thermo-mechanical material model. To identify the critical design parameters and study the effect of parameter uncertainty, sensitivity analysis and Monte Carlo (MC) simulation are performed. Study results reveal that, compared to LRB, SMA-LRB reduces the peak floor acceleration by 20% with an added benefit of 35% and 67% reduction in peak and residual isolator displacement. Parametric uncertainty causes noticeable increase in mean responses of LRB isolated system than deterministic case, which get diminishes for SMA-LRB isolation system. This increase in the mean value of peak floor acceleration, peak, and residual isolator displacement are 64%, 68%, and 60% less for SMA-LRB than LRB isolated building. Further, compare to the LRB, SMA-LRB reduces standard deviation by 77% for the peak floor acceleration and peak isolator displacement, and 85% for the isolator residual displacement. Thus, conjunction of SMA with the LRB isolator enhances the performance and provides robust control effect under parameter uncertainty.

Influence of EBR on the structural resistance of RC slabs under quasi-static and blast loading: Experimental testing and numerical analysis

Flexural strengthening of reinforced concrete (RC) structures with externally bonded reinforcement (EBR) using carbon fibre-reinforced polymers (CFRP) has in recent years received increased interest from specialists, particularly when dealing with protective structures against terrorist or accidental blast loading. Although a significant number of studies have been conducted on the failure modes of the bonded interface for quasi-static conditions, there is still limited published research on the effects of blast loading. In this paper, RC slabs externally strengthened with CFRP are tested in three-point bending as well as subjected to blast loading. The behaviour of the tested specimens under both loading regimes is evaluated with special focus on the mechanisms that lead to the disruption of the CFRP. It was found that the debonding of the CFRP was caused, in both cases, by the fracture and separation of a thin layer of concrete in the near vicinity of the bonded interface. However, the mechanisms that lead to this failure differ. A numerical model was developed and simulations performed using the finite element (FE) code LS-DYNA to investigate the validity of commonly used simplifications on the modelling of the interface in both cases. It was found that although the modelling technique used to represent the disruption of CFRP under quasi-static conditions provide accurate results, it does not return accurate predictions of the debonding of CFRP under blast loading.

Blast loading effects on UHPFRC structural elements: a review

Blast loading effects on UHPFRC structural elements: a review

Effect of Blasting During Tunnel Excavation on an Existing Adjacent Tunnel

In recent decades, the effects of blast loads on existing structures have gained considerable attention due to the increase in threat from various activities. Site-specific empirical relationships for calculation of blast-induced vibration parameters like Peak Particle Velocity (PPV), Peak Particle Acceleration (PPA), and Peak Particle Displacement (PPD) are commonly used for the estimation of the impact of blasting vibration on an existing adjacent tunnel. However, these relationships are not able to consider the variation in rock parameters and uncertainty of in situ conditions such as modern rock mass classifications (i.e., RMR, Q-system, RQD)... In this paper, a published blast data of various researchers in different rock sites at Croix-Rousse tunnel in France have been collected and used to propose a generalized regression model for PPV by considering the effects of rock parameters like Rock Mass Rating (RMR) system, damping ratio “”, Dynamic Young’s modulus “Ed”. By using the numerical analysis method, the proposed regression model of PPV (Empirical Formula) function of a variable and multivariate can be directly used in the prediction of blast-induced vibrations in rocks.

Blast-Loading Effects on Structural Redundancy of Long-Span Suspension Bridge Using a Simplified Approach

Long-span suspension bridges are typically designed against wind and earthquake loadings without considering blast loads because existing blast-resistant design guidelines for bridges are limited and in fact not detailed enough to fully explicate the consequences of a blast event. This study performed detailed dynamic analysis of a long-span suspension bridge to parametrically evaluate its structural redundancy under small to large blasts detonated at different locations. To accomplish this, the blast-structure interaction problem was solved by a simplified approach whereby the blast aspect was modeled as nodal loads by simulating the pressure contour area on the deck surface caused by the explosion; the structural aspect was modeled as a three-dimensional fishbone skeleton finite-element model. In particular, major attention was paid to the blast load effects on the main cable and hangers designed at safety factors of 2.2 and 2.5, respectively. This study concluded that the main cable and hangers show sufficient and insufficient structural redundancies, respectively under small to medium blasts, whereas a large blast was proven to be detrimental to both the main cable and hangers, which may further trigger progressive collapse of the entire suspension bridge.

BLAST LOADING EFFECT ON CHEVRON TYPE BUCKLING RESTRAINED BRACED FRAMES

Buckling Restrained Braced Frames (BRBF) are being used all over the world as a seismic force resisting system in building structures. BRBFs are used due to their high ductility after yielding and the ability to absorb energy. Currently, American Society of Civil Engineers (ASCE) permits the use of BRBFs as a single seismic force-resisting system by quantifying the seismic parameters such as Response Modification Coefficient (R), Over-strength Factor (Ωo) and Deflection Amplification Factor (Cd) in their latest code ASCE 7-16. The purpose of this research is to investigate how a structure built with BRBF to resist seismic forces behaves when subjected to blast loading. In other words, this paper focuses on the effect of blast loading on Buckling Restrained Braced Frames. The investigation is carried out on a Chevron type braced frame. The frame is subjected to a short duration blast loading that lasts only 21.7 mili-second (ms). Blast loading effects on the braced frame are assessed by identifying the weakest plane of failure, deformation characteristics and out of plane bending. The research also investigates the effect of brace core thickness on resisting blast loading. It is observed that the brace core thickness plays a significant role in reducing the deformation characteristics.

BLAST LOADING EFFECT ON CHEVRON TYPE BUCKLING RESTRAINED BRACED FRAMES

Buckling Restrained Braced Frames (BRBF) are being used all over the world as a seismic force resisting system in building structures. BRBFs are used due to their high ductility after yielding and the ability to absorb energy. Currently, American Society of Civil Engineers (ASCE) permits the use of BRBFs as a single seismic force-resisting system by quantifying the seismic parameters such as Response Modification Coefficient (R), Over-strength Factor (Ωo) and Deflection Amplification Factor (Cd) in their latest code ASCE 7-16. The purpose of this research is to investigate how a structure built with BRBF to resist seismic forces behaves when subjected to blast loading. In other words, this paper focuses on the effect of blast loading on Buckling Restrained Braced Frames. The investigation is carried out on a Chevron type braced frame. The frame is subjected to a short duration blast loading that lasts only 21.7 mili-second (ms). Blast loading effects on the braced frame are assessed by identifying the weakest plane of failure, deformation characteristics and out of plane bending. The research also investigates the effect of brace core thickness on resisting blast loading. It is observed that the brace core thickness plays a significant role in reducing the deformation characteristics.

Blast induced lateral earth pressures on retaining structures with sand backfill

An experimental study was conducted to investigate the effects of blast loads on the behaviour of reinforced concrete retaining wall (RCRW) with sand as a backfill material. The soil-RW model was subjected to a simulated blast load using a shock tube. The influence of the backfill relative density, backfill saturation, blast load intensity, and live load surcharge on the behaviour of RCRW with sand backfill was studied. Based on the results, it was noted that the maximum dynamic earth pressures were recorded at a time greater than the positive period regardless of the backfill condition. The total earth pressure distribution along the height of the wall showed that the magnitude of total earth pressure for loose and medium backfill at the mid-height of the wall slightly exceeded the dense backfill. In addition, the lateral earth pressures increased with the increase of the blast load intensities. Relationships between the dynamic earth pressure coefficient (ΔKbd) and accelerations of the wall and the backfill were determined. The maximum dynamic resistance function was reached when high-intensity pressure is applied. Yield was not reached, and intensities of the shots were below the design capacity of the section. The findings of this research will provide valuable information that can be used to evaluate the vulnerability of transportation structures to surface blast events and the development of guidelines for their design.

Response Behavior of Buildings under the Simultaneous Actions of Surface Blast and Progressive Collapse

Due to the near blast condition, columns on the front face of the building may snap off in the blast load’s initial state, leading to a condition of the blast load and progressive collapse effects occurring simultaneously. Herein, the damages caused in the building produced due to progressive collapse under blast loading scenario are investigated. A nonlinear time history analysis of the three-dimensional (3D) model of a six-story building is performed for the progressive collapse following General Services Administration (GSA) guidelines. The surface blast effect is included using simulated air pressure and ground motion produced due to the blast. The progressive collapse analysis is performed for two cases, namely, (1) considering blast effect due to surface blast; and (2) neglecting the effects of the blast wave, and the results of the two cases are compared. The study results show that the effect of the duration of the transient loading used for the progressive collapse analysis has a significant influence on the response quantities of interest. Further, all response quantities of interest are considerably increased when the blast effect is considered compared to the case when the same is neglected.

Numerical Modeling of Rock Panels Subjected to Blast Loadings

In rock engineering problems, the rock is usually subjected to dynamic loads induced by drill, blast and rockburst. Therefore, understanding the dynamic response of rock benefit the safety and productivity of excavation activities. In this study, the response of rock panels under blast loadings is numerically investigated. The uniaxial and triaxial compression tests are firstly conducted in the laboratory to obtain the material property of four types of rocks, including Chuanshan limestone, Gaolishan sandstone, Mineralized limestone and Xixia limestone. Then, a total of 16 numerical simulations are carried out in which each type of rock panel is subjected to TNT blast loadings with four scaled distances, i.e., 0.15 m/kg1/3, 0.30 m/kg1/3, 0.60 m/kg1/3, 1.20 m/kg1/3. The damage distribution, which is characterized by the effective plastic strain, within the rock panels is quantitatively and qualitatively analyzed. The modelling results demonstrate that the effect of blast loading on the rock is material dependent. For a given scaled distance, the Gaolishan sandstone damages most severely, followed by Xixia limestone, Chuanshan limestone, and mineralized limestone. A critical scaled distance is observed on the limestone panels. When the scaled distance is smaller than the critical value, the damage of limestone panels increases with increasing the scaled distance. Once exceeding the critical value, the damage of limestone panels decreases with the increase of scaled distance. However, such a transitional scaled distance is not observed in the sandstone panels, of which damage decreases gradually with the increases of scaled distance.

Blast Loading and Its Effects on Building

Abstract: Terrorist assaults have become more common in recent years. Their main purpose is to destroy important structures such as areas of defense, hospitals, schools, buildings. Due to the explosion, high pressure is generated and the blast time is also very short, but it can damage the structure from outside and inside. Which can cause a lot of damage to human life. There has an influence on the nation's economy. Like the earthquake and wind load, the blast load should also be designed, keeping in mind the important structures that have to be avoided from the explosion. In this research paper, six story R.C.C. Structures exposed to explosion loads are analyzed. We study the effect on the building by changing the weight of the explosive and the distance between the explosion source and the building. The IS 4991-1968 code has been used to calculate the parameters of the explosion pressure waves. The program ETabs 2019 has been used to analyze the effect of blast load. The structure has been modified by providing shear walls to reduce excessive displacement due to blast loading on the building. The results of the analysis are compared after adding the shear wall with the general building model. The result was that after the addition of the shear wall, the effect of blast loading is greatly reduced. Keywords: Blast phenomena, Standoff distance, detonation charge weight (TNT), Front face pressure, Side face pressure, ETABS, RCC, Blast waves, explosive effects, Story Displacement, Storey Drift, Overturning Moment, Shear wall.

Study on the influence of transient unloading on surrounding rock deformation in expanding excavation blasting

The tensile stress generated by the transient unloading of the in-situ stress may cause deformation, damage or even destruction of the surrounding rock. Based on the equivalent load method and the deleted element method, the influence of blast loading and transient unloading on the surrounding rock deformation is studied in the present study. The field blast vibration tests in the BaiHeTan hydropower station were carried to verify the numerical results. The results shown that the deformation simulated by the LS-DYNA agrees well with that measured in the field tests only if the coupling effect of blast loading and transient unloading are considered. In expansive excavation blasting, the convergent deformation caused by transient unloading is about 4 to 6 times greater than that caused by blast loading, and the deformed rock mass area caused by transient unloading is about 2 to 3 times larger than that caused by blast loading. However, plastic zone induced by the blast loading is much wider (about 2.1 times) than that induced by transient unloading. The results show that blast loading tends to cause more damage of surrounding rock, while transient unloading tends to cause larger deformation.

Behaviour of Smart Steel Column‐Beam Connection Under Blast Loading

AbstractThe generated damages in steel structures due to terrorist attack explosion has attracted structural engineering communities, because the effect of blast loading is extremely sever and destructive. The behavior of Superelastic Nickle Titanium Shape Memory Alloy (NiTi SMA) beam‐column connection was infrequently studied under the effect of blast loading. The present study develops smart steel beam‐column connection under the effect of blast loading. The performance of the proposed connection configuration is evaluated numerically to make better understanding of the conceptual design of NiTi SMA‐based smart bolted connections. NiTi SMA‐based smart connection stiffness and strength is determined based on Eurocode steel joint design procedures. Analytically, Simplified Kingery Airblast Calculations approach is used to generate time history blast reflected overpressure parameters. The austenite effect of NiTi‐SMA is introduced to the global 2D frame model by moment rotation capacity curves. The structural components are verified in Ultimate Limit State (ULS) by using the results of global 2D model. The outputs from the 2D global model is introduced in sub‐numerical models. The sub‐models examined by finite element software code. The result shows that the hysteresis flag‐shaped loop of NiTi‐SMA is well expressed by the sub‐models' numerical solutions. As a result, the proposed connection configuration can highlight the efficiency of NiTi‐SMA in terms of energy dissipation capacity under blast loading successfully.

Effect of Blast Loading on Seismically Detailed RC Columns and Buildings

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

Effect of blast loading on the risk of rib fractures: a preliminary 3D numerical investigation

Blast is a complex phenomenon which needs to be understood, especially in a military framework, where this kind of loading can have severe consequences on the human body. Indeed, the literature lists a number of studies which try to investigate the dangerousness of such a phenomenon, both at experimental and numerical level, and the injuries that could occur when the fighters or police officers are stroke by blast wave. When focusing on primary blast effect, this paper analyses the effect of this loading on the occurrence of rib fracture, using previously developed injury risk curves.

Effects of lattice stiffeners and blast load on nonlinear dynamic response and vibration of auxetic honeycomb plates

In this paper, the effects of lattice stiffeners and blast load on nonlinear dynamic response and vibration of auxetic sandwich honeycomb plates on Pasternak elastic foundations are considered. The remarkable point of this study is that the outer surfaces of the system reinforced by lattice stiffeners (including orthogonal stiffeners and oblique stiffeners) are made of functionally graded materials. Based on the analytical solution, the Reddy’s FSDT, the Airy’s stress functions, the Galerkin and the fourth-order Runge-Kutta methods, fundamental frequency, dynamic response and frequency–amplitude curves of the plates reinforced by lattice stiffeners under blast and mechanical loads are determined. Then, the result analyses the effect of lattice stiffeners, blast and mechanical loads, elastic foundations on nonlinear dynamic response and vibration of auxetic honeycomb plates. The optimal angle of oblique stiffeners which maximizes natural frequency and contemporaneously minimizes amplitude when changing geometrical parameters of auxetic honeycomb is also determined.