Blast Wall Research Articles

Performance of Structural Blast Mitigation Measure for Oil and Gas Industrial Facilities

The response of the bulkhead type of blast wall under deflagration blast pulse was studied using finite element modelling software. The behavior of unstiffened and stiffened panels was analyzed. The study aimed at determining the effect of plate and stiffener thicknesses on energy dissipation and distribution of reaction forces. This was carried out in order to optimize the response of the primary steelwork through typological and geometrical modifications of the local element. Furthermore, novel strategies for the improvement of the blast response were introduced with a focus to use alternative materials and innovative connections. The latter was assessed numerically using a simplified model and its benefits were analyzed by comparing with the traditional approach.

Numerical study of fence type blast walls for blast load mitigation

A new fence type blast wall consisting of steel poles was recently proposed based on the idea that the blast wave-obstacle interaction could generate wave reflection, diffraction and out-of-phase interference to reduce the wave energy. The effectiveness of this kind of new blast wall in mitigating blast loading was investigated through 2D numerical simulations and field blasting tests. In this study, 3D numerical simulations are carried out as an extension of the previous studies for a more comprehensive understanding of the effectiveness of fence blast wall. The simulations are performed by using an explicit dynamic finite element analysis software AUTODYN 3D with validated material models. Responses of a reinforced concrete (RC) wall under blast load are also calculated for comparison. Influences of different parameters of the fence wall, including the cross-sectional shape of the steel poles, spacing between poles, number of fence layers and spacing between layers, on its effectiveness in mitigating the blast loadings are investigated. The peak overpressure, impulse and overpressure-time histories behind the fence and RC blast wall are compared with those in free field for evaluation. It is found that the fence blast wall, if properly arranged, could perform equally or even better than the RC wall in mitigating overpressure and impulse of blast wave. Moreover, fence blast wall is less likely to generate the secondary debris hazards associated with the RC and other solid walls when close-in explosion occurs. Therefore, it is an excellent alternative blast barrier in protecting critical structures in urban areas.

Experimental and numerical investigations on the shock wave attenuation performance of blast walls with a canopy on top

This paper presents experimental and numerical investigations on the performance of various blast wall configurations in attenuating the shock wave. The blast walls are composed of a gabion wall with a canopy made of metal sheets, which is mounted at the top of the gabion wall with different angles of inclination. Three experiments were conducted for each configuration. Numerical models are developed and validated against the experimental data. Due to the small width of blast walls in the experiments, besides the vertical air flow over the top of the wall, the horizontal air flow around the sides of the wall plays a great role in the overpressure distribution behind the wall. The interaction between these air flows causes an overpressure increase at the building facade. In order to prove the design concept of the canopy, the wall width in the forthcoming experiments should be so large that no horizontal air flow occurs. Using the validated numerical models, three observations arisen from the studies of blast walls having infinite width. Firstly, the canopies can further reduce the overpressure and impulse behind the blast wall. Secondly, configuration M3 (canopy arranged 45° facing the charge) shows the best performance in shock wave attenuation among all three configurations. It offers an overpressure (impulse) reduction ranging from 51.7% to 88.0% (from 30.5% to 59.2%) at the gauges employed in the experiments, compared to the free field scenario. Thirdly, the optimal angle of inclination of the canopy, by which the blast wall achieves the best shock wave attenuation performance, lies between 105° and 120° (between 115° and 125°) for the overpressure (impulse) reduction.

A Predictive Model for Damage Assessment and Deformation in Blast Walls Resulted by Hydrocarbon Explosions

In this paper, a new method is developed to find the ductility ratio in blast walls, resulted by hydrocarbon explosions. In this method, only the explosion energy and distance from the centre of explosion are required to find the damage by using simple predictive models in terms of empirical‐type formulas. The explosion model herein is a TNO multiphysic method. This provides the maximum overpressure and pulse duration in terms of the explosion length and distance from explosion centre. Thereafter, the obtained results are combined with the SDOF model of the blast wall to determine the ductility ratio and the damage. By using advanced optimisation techniques, two types of predictive models are found. In the first model, the formula is found in terms of 2 parameters of explosion length and distance from explosion centre. However, the 2nd model has 3 parameters of explosion length, distance, and also the natural period of the blast wall. These predictive models are then used to find explosion damages and ductility ratio. The results are compared with FEM analysis and pressure‐impulse (P‐I) method. It is shown that both types of models fit well with the outputs of the simulation. Moreover, results of both models are close to FEM analysis. The comparison tables provided in this paper show that, in the asymptotic region of P‐I diagrams, results are not accurate. Therefore, this new method is superior to classical pressure‐impulse (P‐I) diagrams in the literature. Advantage of the new method is the easy damage assessment by using simple empirical‐type formulas. Therefore, the researchers can use the method in this paper, for damage assessment in other types of blast resistive structures.

Efficiency of blast walls for protection of soft targets

Abstract The recent trend of terrorist attacks on civilian targets, including transportation systems, resulted in efforts to harden and strengthen these objects which previously were not designed to cope with this kind of threat. The blast mitigation strategies traditionally used in industrial facilities may provide an additional safety. One such solution is a blast wall that could be used for facade systems or for protection of muster areas and evacuation routes of metro and train stations or airports. This paper deals with the assessment of the blast response of protection walls. The typical types of blast walls commonly used in practice in industrial sector are described. The behavior of blast walls is characterized using simple analytical approach and finite element modelling. The advantages and limitations related to each of these characterization techniques are discussed compared with findings of other authors. Furthermore, a parametric study is performed through extrapolation of numerical models. Two common types of panels with both fixed and pinned boundary conditions are subjected to directly defined pressure loads. Their responses are compared in order to evaluate the effects on the primary steelwork. Possible benefits deriving from typological and geometrical modifications of the local element are also presented. Particular emphasis is given to the importance of the estimation of the reaction forces, displacements and energy dissipation.

Dynamic structural response characteristics of new concept blast walls under hydrocarbon explosions

OFFSHORE INSTALLATIONS ACTIVITIES ENTAIL THE HAZARD OF EXPLOSION ACCIDENTS WITH POTENTIALLY SEVERE CONSEQUENCES TO SAFETY OF WORKERS, INTEGRITY OF SYSTEM, POLLUTION OF THE ENVIRONMENT, AND ECONOMIC LOSSES. BLAST WALLS ARE GENERALLY USED FOR THE PURPOSE OF REDUCING THE EXPLOSION CONSEQUENCES. THIS STUDY INTRODUCE A NEW CONCEPT OF BLAST WALL (PERFORATED BLAST WALL) WHICH CAN DISRUPT LOAINDG PRESSURE DURING THE EXPLOSION. A DYNAMIC FINITE ELEMENT ANALYSIS WAS PERFORMED TO INVESTIGATE THE EFFECTS OF THE GEOMETRIC CHARACTERISTICS ON THE PERFORMANCE OF PERFORATED BLAST WALLS. A SERIES OF COMPUTATIONS WERE PERFORMED VARYING WITH OPENING SIZE, PLATE THICKNESS AND OPENING LAYOUT ASSOCIATED WITH BLOCKAGE RATIO. A PROPOSAL FORMULA WAS DERIVED AS A FUNCTION OF THOSE DESIGN PARAMETERS FOR EASILY EXPECTING THE DYNAMIC STRUCTURAL RESPONSE CHARACTERISTICS.

Recommended Finite Element Formulations for the Analysis of Offshore Blast Walls in an Explosion

Abstract This study suggests relevant finite element (FE) formulations for the structural analysis of offshore blast walls subjected to blast loadings due to hydrocarbon explosions. The present blast wall model adopted from HSE (2003) consists of a corrugated panel and supporting members, and was modelled with shell, thick-shell, and solid element combinations in LS-DYNA, an explicit finite element analysis (FEA) solver. Stainless and mild steels were employed as materials for the blast wall model, with consideration of strain rate effect throughout ten (10) pulse pressure load regimes. The obtained FEA results were validated by experimental data from HSE (2003) with decent agreement. In the present study, recommended FE formulations with additional hourglass control functions were widely discussed from the perspectives of solution accuracy and computational cost based on a statistical approach. The obtained outcomes could be used for the structural analysis and design of offshore blast walls in the estimations of maximum and permanent deformations under blast loadings.

The blast alleviation effects of a hybrid barrier system with triple energy absorbers

Blast walls on offshore topsides are designed to protect personnel and critical equipment. The traditional design that relies on the panel as the sole energy absorber is difficult to achieve the code compliances. While studies on dual absorber system such as foam cored sandwich panels overlook the boundary effects. This study investigates the blast alleviation effects of a hybrid barrier system with triple energy absorbers (i.e. panel, foam and springs), in which the foam and springs are placed at the supports to prevent weld rupture. Accordingly, a novel design concept is proposed by using flexible supports filled with polymethacrylimide foam and rotational springs, allowing the wall to slide/rotate a certain distance/angle to release the high stresses at supports and meanwhile dissipate blast energy through material deformations. The panel deflection, energy absorption and weld rupture of the proposed system are the focal points. An analytical model based on beam vibration theory and virtual work theory has been developed, in which the boundary conditions at each support are simplified as a translational spring and a rotational spring. Finite element method has been applied to corroborate the analytical model. In addition, the interaction effects between the three absorbers have been investigated through energy absorption breakdowns. In the end, a numerical comparison study with the traditional design has been presented to demonstrate the privilege of the proposed system in minimising weld rupture risk due to the high stresses being realeased through controlled displacements and rotations at supports.

An empirical formulation to predict maximum deflection of blast wall under explosion

This study proposes an empirical formulation to predict the maximum deformation of offshore blast wall structure that is subjected to impact loading caused by hydrocarbon explosion. The blast wall model is assumed to be supported by a simply-supported boundary condition and corrugated panel is modelled. In total, 1,620 cases of LS-DYNA simulations were conducted to predict the maximum deformation of blast wall, and they were then used as input data for the development of the empirical formulation by regression analysis. Stainless steel was employed as materials and the strain rate effect was also taken into account. For the development of empirical formulation, a wide range of parametric studies were conducted by considering the main design parameters for corrugated panel, such as geometric properties (corrugation angle, breadth, height and thickness) and load profiles (peak pressure and time). In the case of the blast profile, idealised triangular shape is assumed. It is expected that the obtained empirical formulation will be useful for structural designers to predict maximum deformation of blast wall installed in offshore topside structures in the early design stage.

Energy absorption of the ring stiffened tubes and the application in blast wall design

Thin-walled mental tubes under lateral crushing are desirable and reliable energy absorbers against impact or blast loads. However, the early formations of plastic hinges in the thin cylindrical wall limit the energy absorption performance. This study investigates the energy absorption performance of a simple, light and efficient energy absorber called the ring stiffened tube. Due to the increase of section modulus of tube wall and the restraining effect of the T-stiffener flange, key energy absorption parameters (peak crushing force, energy absorption and specific energy absorption) have been significantly improved against the empty tube. Its potential application in the offshore blast wall design has also been investigated. It is proposed to replace the blast wall endplates at the supports with the energy absorption devices that are made up of the ring stiffened tubes and springs. An analytical model based on beam vibration theory and virtual work theory, in which the boundary conditions at each support are simplified as a translational spring and a rotational spring, has been developed to evaluate the blast mitigation effect of the proposed design scheme. Finite element method has been applied to validate the analytical model. Comparisons of key design criterions such as panel deflection and energy absorption against the traditional design demonstrate the effectiveness of the proposed design in blast alleviation.

Dynamic behaviour of unstiffened stainless steel profiled barrier blast walls

ABSTRACTPerforming optimum design, reliable assessment or suitable verification for stainless steel profiled barrier blast wall structures requires dealing with various challenges, stemming from the associated uncertainties in material properties, fabrication, installation, and more importantly variations in the blast load characteristics. In the analysis, assessment, and design of these blast walls, one of the key areas to be appreciated and understood is the dynamic response of these structures. This paper presents a methodology developed for identifying the predominant structural behaviour and characteristics of profiled barrier blast wall structures, using a probabilistic approach. Twenty parametric base models are developed using Ansys and by implementing a Latin hypercube sampling (LHS) approach, the section properties of the models are represented in terms of probability distributions. A number of models are generated stochastically and modal analyses performed to identify the dynamic sensitivity of these models. The corresponding response classification of these structures is evaluated from the load duration and natural periods of the structures. The results of the study confirm that structural response, for the wide range of profiled blast walls analysed, is mainly quasi-static or static, as opposed to dynamic. In fact, dynamic effects are negligible for unstiffened profiled barrier blast walls and structural responses in most cases can be estimated on a static or quasi-static basis. This conclusion would help a competent design engineer to consider a proper dynamic load factor at an early stage of the design, without involving complex advanced nonlinear dynamic analyses.

Field Testing of Fence Type Blast Wall for Blast Load Mitigation

To protect structures from external explosions, solid protective barriers have been demonstrated by experimental and numerical studies to be able to effectively mitigate blast loads on structures behind them. However, to protect against blast loads, barriers normally need to be designed to have high structural resistance and ductility. This often requires bulky and heavy protective barriers which are not only highly costly but also often not appropriate for application in downtown areas as they are not friendly to city planning or appearance. Fence type blast wall consisting of structural columns was recently proposed and its effectiveness in mitigating blast loads was investigated through numerical simulations. It was found that the wave–fence interaction and interference of waves significantly reduced the wave energy when the blast wave passed through the fence blast wall. To further investigate the effectiveness and applicability of fence type blast wall as a highly potential technology for structural protection in an urban area, field tests have been conducted and results are reported in this paper. Columns with circular and triangular cross-sections were adopted to build fence blast walls. In addition, a masonry wall was also constructed as solid barrier for comparison. Hemispherical TNT explosive weighing 1.0 kg with different stand-off distances was detonated on the ground to generate the blast load. Blast overpressures in free air, behind the fence blast wall and behind the masonry wall were recorded by pressure sensors. The effectiveness of the fence blast wall in reducing blast wave and protecting structures was demonstrated by the test data.

Numerical Investigation of Structural Response of Corrugated Blast Wall Depending on Blast Load Pulse Shapes

HYDROCARBON EXPLOSIONS ARE ONE OF MOST HAZARDOUS EVENTS FOR WORKERS ON OFFSHORE PLATFORMS. TO PROTECT STRUCTURES AGAINST EXPLOSION LOADS, CORRUGATED BLAST WALLS ARE TYPICALLY INSTALLED. HOWEVER, THE PROFILES OF REAL EXPLOSION LOADS ARE QUITE DIFFERENT DEPENDING ON THE CONGESTION AND CONFINEMENT OF TOPSIDE STRUC-TURES. AS THE LEVEL OF CONGESTION AND CONFINEMENT INCREASES, THE EXPLOSION LOAD INCREASES BY UP TO 8 BAR, AND THE RISING TIME OF THE LOAD DECREASES. THIS STUDY PRIMARILY AIMS TO INVESTIGATE THE STRUC-TURAL BEHAVIOR CHARACTERISTICS OF CORRUGATED BLAST WALLS UNDER DIFFERENT TYPES OF EXPLOSION LOADINGS. FOUR LOADING SHAPES WERE APPLIED IN THE STRUCTURAL RESPONSE ANALYSIS, WHICH UTILIZED A DY-NAMIC NONLINEAR FINITE ELEMENT METHOD.

Development of a New Fence Type Blast Wall for Blast Protection: Numerical Analysis

Blast wall is considered to be an effective passive measure for blast protection since it can effectively reduce the blast loads and protect the building structures and people behind it. However, the current practice in blast wall design mainly depends on the structural strength and ductility to resist blast loads. These designs often lead to huge solid walls which are not only expensive, but also unsuitable for construction in urban areas, as they are not aesthetically appealing. Moreover, failure of solid blast wall may generate a significant amount of debris, which imposes great threats to people and structures behind the wall. In this paper, a new fence type blast wall, instead of the solid wall, is proposed to resist the blast loads based on the concept of wave interference. The proposed fence wall uses structural columns placed at strategic locations as wave stoppers to generate wave reflection, diffraction and interaction between the reflected and diffracted waves from different columns to result in self-cancellation of wave energy, thus leads to substantial reduction in blast wall size in design. Numerical simulations are carried out to investigate the effectiveness of the fence wall layout with different column geometries, column spacing, column dimensions, and fence layers on blast loads reduction. Based on the results, an effective design of the fence type blast wall is proposed, which can reduce the pressure and impulse of the blast loads behind the wall upto 70%.

Optimal blast wall layout design to mitigate gas dispersion and explosion on a cylindrical FLNG platform

This paper presents a comprehensive safety design of blast wall layout on a cylindrical Floating Liquefied Natural Gas (FLNG) platform. Comparing to the mitigation measure – safety gap investigated previously (Li et al., 2016a, 2016b), blast wall is a better option to be utilized in the congested areas with space limitation. Both of deterministic and probabilistic studies on the cylindrical FLNG platform with and without blast walls subjected to gas dispersion and explosion are conducted. The Computational Fluid Dynamics (CFD) simulation results of more than 120 gas cloud sizes and 16,000 gas explosion overpressures indicate that blast walls are exclusively beneficial for mitigating of flammable gas cloud and explosion overpressure, if the initial gas leak rates are high momentous. A series of different blast wall layouts are designed for the cylindrical FLNG. By taking all uncertainties including different leak rates, leak locations, and gas cloud conditions etc. into account, the optimal blast wall layout with lowest explosion overpressure exceedance frequencies is determined.

Structural Response of Blast Wall to Gas Explosion on Semi-Confined Offshore Plant Topside

Since gas explosion is the most frequent accidental event occurring in the oil and gas industry, all safety-related critical elements on the topside of offshore platforms should retain their integrity against extreme pressure demands. Although considerable effort has been devoted to develop blast-resistant design methods for offshore structures, there remain several issues that require further investigation. The duration of the triangular-shaped blast design pressure curve with a completely positive side is usually determined by the absolute area of each measured transient pressure response, using the flame acceleration simulator (FLACS). The negative phase pressure in a general gas explosion, however, is often quite crucial, unlike gaseous detonation or TNT explosion. The objective of this study is to thoroughly examine the effect of the negative phase pressure on structural behavior. A blast wall for a specific floating production, storage, and offloading (FPSO) topside is considered as an exemplar structure for blast-resistant design to focus only on overpressure because there is no drag pressure in this type of obstacle. Gas dispersion and explosion simulations were carried out using FLACS, while LS-DYNA was used in the nonlinear transient finite element structural analysis.

Quantifying Blast Effects on Constructed Facilities behind Blast Walls

AbstractExplosive attacks on constructed facilities are a significant threat worldwide, producing devastating consequences including loss of life, property damages, and economic losses. This paper ...

Numerical prediction of blast wall effectiveness for structural protection against air blast

This paper presents a prediction method for the effectiveness of various blast wall configurations in providing protection against air blast. Shock wave propagation and its interaction with the blast wall were performed in LS-DYNA in order to calculate the overpressure-time histories behind the blast wall. The peak overpressures and specific impulses were determined. The influence of structural flexibility on the blast wall effectiveness was considered by including a metal sheet (“canopy”) at the top of the wall. Three experiments were conducted to measure the blast loads behind the blast wall. During the planning phase of the experiments, numerical models were developed in order to predict the main blast and response parameters. The experiments can then be used to validate the numerical models. If the numerical models are validated, they are able to predict the performance of other blast walls without further experiments. It was found that certain blast wall configurations can reduce the blast effects on buildings. However, there were also unfavorable configurations, where no reduction in the blast effects was found. These studies serve to understand the behavior of air blast interacting with blast walls and identify the principal parameters for the design of such walls.

Review of Blast Loading Models, Masonry Response, and Mitigation

Different models for prediction of blast loading, response of masonry structure against blast load, and various mitigation strategies are discussed. Variation of peak positive incident pressure with scale distance in free field spherical burst and surface burst scenarios, proposed by different researchers, is presented and compared. The variation is found significant in the region of small scaled distances. Blast wave parameters in urban environment have been found different from the free field scenario. Effects of geometry, boundary conditions, and material properties on response of masonry buildings were found significant. Different mitigation strategies such as blast wall, landscaping, architecture, and retrofitting techniques are presented.

Explosion induced dynamic responses of blast wall on FPSO topside: Blast loading application methods

Topside areas on an offshore oil and gas platform are highly susceptible to explosion. A blast wall on these areas plays an important role in preventing explosion damage and must withstand the expected explosion loads. The uniformly distributed loading condition, predicted by Explosion Risk Analyses (ERAs), has been applied in most of the previous analysis methods. However, analysis methods related to load conditions are inaccurate because the blast overpressure around the wall tends to be of low-level in the open area and high-level in the enclosed area. The main objectives of this paper are to study the effects of applying different load applications and compare the dynamic responses of the blast wall. To do so, various kinds of blast pressures were measured by Computational Fluid Dynamics (CFD) simulations on the target area. Nonlinear finite element analyses of the blast wall under two types of identified dynamic loadings were also conducted.