Design charts and polynomials for air-blast parameters

The protective design of civilian structures generally requires the prediction of air-blast loadings. The scaled-distance charts developed by Kingery and Bulmash, as implemented in US government manuals such as UFC 3-340-02, are typically used to estimate values of incident and reflected overpressures and impulses for protective design. The Kingery-Bulmash charts reasonably predict these design parameters in the far field but not in the near field, close to the face of the charge, and inside the fireball. This paper presents predictive equations and scaled-distance charts for incident and reflected overpressures and impulses, arrival time, and positive phase duration based on numerical studies of free-air detonations of spherical charges of TNT.

Journal of Structural Engineering, 2014

Air-blast parameters, including incident and reflected peak overpressures and impulses, and shock-front arrival times, are typically estimated for protective design using charts developed by Kingery and Bulmash. The charts underpredict incident and normally reflected peak overpressures and incident impulse near the face of the charge. Numerical analyses of detonations of spherical charges of trinitrotoluene in free air are performed using a verified and validated computational fluid dynamics (CFD) code to understand the shortcomings of current approaches for calculating incident and normally reflected overpressures and impulses, and for shock-front arrival time. New equations and design charts are proposed based on CFD calculations.

Structures Congress 2014, 2014

Charts in the UFC-3-340-2 design manual are used to compute peak incident overpressures and impulse generated by a detonation of an explosive as a function of scaled distance and angle of incidence. These charts assume either a spherical or hemi-spherical charge and do not account for the variation in charge shape, charge orientation and the point of detonation within the charge. A numerical study was performed using AUTODYN to study the influence of charge shape, charge orientation and point of detonation within the charge on the free-field overpressure distributions and the response of an A992 Grade 50 W14 × 257 column. A set of analyses was performed with cylindrical charges with different aspect ratios. Results were compared with those involving a baseline analysis of a spherical charge. The resulting peak incident overpressure and impulses, and the pressure contours were compared in the near-, mid-and far-fields. In the near-field, the overpressure distributions are influenced significantly by charge shape and the point of detonation in the charge. The influence of these variables diminishes with distance. The loading and subsequent response of the W14 × 257 column to a near-field detonation showed significant dependence on the charge shape and charge orientation and clearly demonstrated that SDOF assumptions are inappropriate for blast-resistant design against detonations of improvised explosive devices at small standoff distances.

KSCE Journal of Civil Engineering, 2017

The single-degree-of-freedom (SDOF) analysis with elastic-plastic resistance is often used for design of protective structures subjected to blast loads. Several documents such as UFC 3-340-02 present design charts for the maximum responses of the elasticplastic SDOF system. The SDOF design charts are available for far-field detonations but seldom for near-field detonations of high explosive in free air, noting that the focus of security design is the near-field. Further, the assumption of uniformly distributed load for the SDOF analysis may not be appropriate for the near-field detonations where blast pressure distribution varies significantly with distance and angle of incidence. In this paper, to resolve these issues, updated SDOF design charts including the response to the nearfield detonations are suggested based on numerical calculations. These generated charts are verified with comparison to UFC 3-340-02 predictions and finite element analysis results of steel components. The recommendations and limitations for the utility of the SDOF design charts for blast assessment of steel components are provided with an emphasis on the near-field detonations.

International Journal of Protective Structures, 2010

A AB BS ST TR RA AC CT T Although the distributions of peak incident overpressure and impulse generated from spherical charges and cylindrical charges of the same weight can differ greatly close to the point of detonation, spherical charges are assumed for nearly all explosive-effects computations per modern standards for blast-resistant design such as UFC-3-340-02 and the soon-to-be published ASCE Standard for the Blast Protection of Buildings. A blast-testing program was performed using a reinforced concrete slab as the target to investigate the reflected peak overpressure and impulse distributions as a function of charge shape, orientation, and scaled distance. The charge shapes were cylindrical and spherical, and the charge mass varied from 0.24 to 8.0 kg. Nine pressure transducers were installed on the surface of the slab to record the distribution of pressure histories over the face of the target. A finite element model of the explosive and the target was validated using the experimental data. The validated model was then used to undertake a parametric analysis to more broadly study the effects of detonation point, ratio of charge length to charge diameter, charge orientation and standoff distance on the distribution of reflected overpressure. Numerical results are compared with predictions of UFC-3-340-02. For cylindrical charges, the ratio of charge length (L) to diameter (D), the orientation of the longitudinal axis of the charge, and detonation point within the charge affected the distributions of reflected peak overpressure and impulse in the immediate vicinity of the explosive. The UFC-3-340-02 underpredicts substantially the reflected peak overpressure and impulse on a target aligned with the vertical axis of a cylindrical charge with an aspect ratio of 1.0.

In the near field, the incident peak overpressure and impulse generated from spherical charges are significantly different from those generated from cylindrical charges of the same mass. However, modern standards for blast-resistant design such as UFC-3-340-02 and the soon-to-be published ASCE standard for the blast protection of buildings assume that the charge is spherical and ignore the effect of charge shape. Further, the ratio of charge length (L) to diameter (D) affects the pressure distribution and impulse in the immediate vicinity of the explosive: for large values of L/D, most of the energy is directed in the radial direction whereas for small values of L/D, most of the energy is directed in the axial direction. A series of blast tests were conducted on a 2000×1000×100 mm reinforced concrete slab to investigate the effects of charge shape, orientation, and scaled distance on the overpressure distribution and impulse on the slab. Nine pressure transducers were installed on the surface of the slab to record pressure histories. The charge shape was cylindrical or spherical and the charge mass varied from 0.24 to 8.0 kg. For the cylindrical charges, the axis was orientated either horizontally or vertically; in the horizontal orientation, the axis of the charge was parallel with the long axis of the slab. The experimental studies showed that the UFC overestimates the reflected overpressure for both the spherical charge and the horizontally oriented cylindrical charge but underestimates the reflected overpressure for the vertically oriented cylindrical charges.

Applied Sciences, 2022

This paper presents the issue of determining the blast load on an engineering structure. In cases of industrial accidents or terrorist attacks, in many cases it is necessary to determine the necessary explosion parameters to determine the response of the structure, preferably in a simple and time-saving manner. In such a way, the empirical relationships can be used to estimate the selected parameters of the explosion load. Many empirical relationships have been derived in the past, but not all are suitable for different types of explosions. This article compares and validates experimentally determined selected explosion parameters for the chosen explosive with empirical relationships. For comparison, three already verified and frequently used calculation procedures (Kingery, Kinney, Henrych) and one newly derived procedure (PECH) were used. As part of the experimental measurements, blast wave explosion parameters for small charges were determined for near-field explosions. The gener...

International Journal of Protective Structures, 2020

While the current state of blast-resistant design methods is based largely on empirical observations of actual explosive testing or numerical simulations, experimental testing remains the ultimate method for validating blast protection technologies. Field trials for performing systematic experimental studies are exceedingly expensive and inefficient. Conventional blast simulators (shock tubes) enable blast testing to be performed in a safe and controlled laboratory environment but are significantly deficient. The Australian National Facility of Physical Blast Simulation based on the 'Advanced Blast Simulator' concept was established to address the shortcomings of conventional blast simulators (shock tubes). The blast simulator at the National Facility of Physical Blast Simulation is a state-of-the-art design having a test section of 1.5 × 2.0 m with dual-mode driver able of operating with either compressed gas or gaseous detonation modes. The simulator is capable of a range of blast-test configurations such as full-reflection wall targets and diffraction model targets. This article aims to demonstrate the ability of the Advanced Blast Simulator in accurately generating a far-field blast environment suitable for high-precision and repeatable explosion testing of various building components. Blast pressure-time histories generated with the Advanced Blast Simulator are validated against equivalent TNT free-field curves reproduced with Conventional Weapons Effects Program. Numerical models based on Computational Fluid Dynamics were developed in ANSYS FLUENT to accurately characterise and visualise the internal flow environment of the National Facility of Physical Blast Simulation Advanced Blast Simulator. The Computational Fluid Dynamics model was also used to explain experimental observations and to determine density and dynamic pressure information for comparisons with free-field explosion conditions.

International Journal of Protective Structures

Equivalency is often used to enable calculations of overpressures and impulses for explosives other than TNT. Equivalent mass factors are available for far field detonations but none are available for near field detonations. These reported factors are associated with incident overpressure and impulse and assumed appropriate for reflected overpressure and impulse. Numerical studies of TNT-equivalent mass factors for four high explosives (PETN, Composition B, Pentolite and Tetryl) for incident and normally reflected peak overpressure and impulse are presented for a wide range of scaled distance 0.06 ≤ Z ≤ 40 m/kg 1/3. Emphasis is placed on near-field detonations for which no reliable factors are currently available.