Breakage response of glass panels subject to long-duration blast

Abstract

Glass windows are vulnerable building components and, in the event of a blast, give rise to a large damage radius. Many older buildings contain annealed glass which shatters instantly into angular shards, lacerating the skin on impact and causing significant injury. Up to 80% of injuries in an urban blast are caused by glass failure. In the far-field of large explosions, long-duration blast environments occur, typically defined by a positive phase duration greater than 40ms. Resulting impulses can cause window failure several kilometres away from the point of detonation. Data from long-duration blast events indicate window failure is highly dependent on glazing aspect ratio, area and other structural parameters. Inconsistency in window response has been attributed to material strength variation which can be in excess of ±25%. The Glazing Hazard Guide, the current UK design standard, indicates windows with matching dimensions respond consistently to blast loading, incorporates no extrapolation method to other glazing dimensions and has been demonstrated to be overly conservative.

In this thesis, influence of glazing aspect ratio, support conditions, material strength and the blast environment on window failure was investigated. Four phases of experimental testing and a comprehensively benchmarked parametric study enabled quantification of the influence of these parameters. Full-scale experimental testing of glazing response to long-duration blast was undertaken in the air blast tunnel (ABT) at MOD Shoeburyness, UK. Glazing response was dependent on complex interactions between structural and blast parameters. Experimental repeats importantly indicated significant data spread, demonstrating that glazing response should be measured as a probability of failure. Damage probability curves and pressure-impulse charts with contours of failure probability were produced for each parameter and were proposed as a new design method. These charts capture true glazing behaviour, are easy to interpret and highlight to the user that window response should be treated statistically. Findings indicated variation in material strength due to distribution of flaws produced the largest spread in failure pressure.

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Identifiers

ORCID for Sarah Monk: orcid.org/0000-0002-0407-1493

ORCID for Simon Clubley: orcid.org/0000-0003-3779-242X

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