Against a bomb blast, standard annealed glass is likely to shatter even 100m away and flying shards of glass can lead to many casualties. Whilst the majority of buildings will not be direct targets, the vulnerability of glass at such a large distance demands that building owners managers give serious consideration to glass containment in the event of a blast.
The building is unlikely to be a direct target, but if it has commercial or public use, there exists a duty of care and glass should be protected.
Conventional secondary windows glazed with 6.8mm class 'A' laminated glass will provide an effective barrier against a vehicle bomb detonated 40-45m away. The laminate glass incorporates a thin plastic (pvb) sheet which will stretch under the blast load and hold the glass together. Protection offered by secondary glazing is particularly relevant for small pane windows or leaded lights.
The building is unlikely to be a direct target, but is close to more sensitive buildings.
The secondary windows can still incorporate 6.8mm laminated glass, but the frames, locks and fixings will be more robust and offer protection from a vehicle bomb at a distance of 30-33m.
The building is a potential direct target on account of usage or ownership.
These buildings may require a number of protective strategies in addition to enhancement of the glazing. The laminate glass will have a minimum 1.5mm thick pvb interlayer and 7.5mm, 9.5mm or 11.5mm glass are commonly specified. This thicker material stretches further before tearing and can withstand a vehicle bomb detonating 20-25m away.
The secondary window frames and locks need special features to cope with the blast loads. Glazing rebates will vary between 20mm and 35mm and in some cases the glass will be bonded to the frame. Secure anchors are needed to tie the frame back to the building structure and, in cases where the wall is unable to take the blast loads, supporting steel frames will have to be introduced spanning the floors.
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