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RESEARCH PAPERS

Development of an Improved Methodology for Predicting Airblast Pressure Relief on a Directly Loaded Wall

[+] Author and Article Information
Denis D. Rickman

 US Army Engineer Research & Development Center, CEERD-GM-I, 3909 Halls Ferry Road, Vicksburg, MS 39180Denis.D.Rickman@erdc.usace.army.mil

Donald W. Murrell

 Northwind, Inc., CEERD-GM-I, 3909 Halls Ferry Road, Vicksburg, MS 39180Donald.W.Murrell@erdc.usace.army.mil

J. Pressure Vessel Technol 129(1), 195-204 (May 24, 2006) (10 pages) doi:10.1115/1.2409317 History: Received February 02, 2006; Revised May 24, 2006

The interaction of an airblast wave with a structure, and the blast wave propagation around and over the structure is of significant importance. In order to protect a structure from the airblast produced by such explosive threats as terrorist bombs, a facility designer must possess an adequate knowledge of the expected blast wave loading. Of greatest importance are pressures and impulses on the directly loaded face of the structure, since it is typically subjected to the highest (reflected) pressures. It has long been recognized that reflected pressure time histories can be strongly influenced by pressure relief from the free edges of the loaded wall. The relief wave can significantly reduce the magnitude of the late-time portion of the positive reflected pressure phase, resulting in a substantial decrease in the peak impulse load. Most current predictive methodologies attempt to account for the relief wave and its effect on impulse. Unfortunately, these methods tend to be rather inaccurate because the exact manner in which the relief wave is manifested is not accurately defined. The US Army Engineer Research and Development Center has developed an improved methodology to predict the effect of pressure relief. This paper presents the basis for the methodology and its practical application.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Typical representation of pressure relief using triangular pulses

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Figure 2

Face-on view of a directly loaded wall

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Figure 3

Small-scale experiment concept

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Figure 4

Variation of peak reflected pressure impulse with charge-to-structure distance

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Figure 5

Reflected pressure measurement and CONWEP normally reflected pressure, 4.116m charge-to-structure distance, small structure

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Figure 6

Reflected pressure measurement and CONWEP normally reflected pressure, 2.776m charge-to-structure distance, large structure

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Figure 7

Comparison of CONWEP LOS predicted peak reflected impulse versus charge-to-structure distance

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Figure 8

Ratio of peak impulse values predicted by CONWEP LOS to measured values. The ratios are for the smaller model structure and at the lowest measurement location along the structure centerline.

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Figure 9

Measured reflected pressure wave form and various CONWEP predicted airblast wave forms for the large model structure located at a distance of 2.766m from a 72.7g C-4 explosive charge

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Figure 10

Measured and predicted wave forms for Experiment PP2-FF-7

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Figure 11

Relief function for large and small structures at a standoff distance of 1.646m. A smoothed curve fit to the relief functions is also shown.

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Figure 12

Smoothed curve fits approximating the relief function at the 1.646m, 2.776m, and 4.116m standoff distances

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Figure 13

Relief function curve fits for standoff distances of 1.646m, 2.766m, and 4.116m

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Figure 14

Curve fit coefficients a and b versus scaled standoff distance

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Figure 15

Calculated relief wave for a structure standoff distance of 2.766m. The measured and CONWEP -calculated reflected pressure wave forms are also shown.

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Figure 16

Measurement locations for add-on experiments. All dimensions are in millimeters.

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Figure 17

Reflected pressure measurements across the face of the structure for add-on Experiment 1

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Figure 18

Relief wave transit times

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Figure 19

Average relief wave velocities for various standoff distances versus distance from structure edge

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Figure 20

Application of the pressure relief function for measurement location RP1 on the large structure at a standoff of 4.116m

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Figure 21

Comparison of peak reflected impulse across the large structure face for a 4.116m standoff distance

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Figure 22

Comparison of the measured reflected pressure from a full-scale experiment versus the predicted wave form utilizing the new methodology

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Figure 23

Comparison of the measured reflected pressure impulse from a full-scale experiment versus the predicted wave form utilizing the new methodology

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