By Luke Stevens
With modifications often as simple as adding an extra bead of structural silicone, or a few tek screws; can you afford to lose clients by not building blast resilience into your development?
Blast engineering is often a requirement which is thrust onto developers at a late stage at the insistence of government, tech or blue-chip clients. In the past we have seen these clients specify their own buildings and manage their own historical estates. However, this model fails to match the agility of modern working where Companies prefer floors of multi-tenanted spec developments or even secure co-working across London, New York and EMEA.
Almost all modern speculative office developments use a reinforced concrete or a steel framed structure and a curtain walling facade system. Happily, in the UK the post Ronan Point building regulations concerning disproportionate collapse, reduce the likelihood of structural collapse, but a façade failure may cause significant harm to those working within the building.
Below is a video of a window system under a test blast which has not been properly secured into the frame. It fails as a result of an “unbalanced blast design”.
Next is a much more successful test of a Windowgard façade. It shows how the glass and laminate interlayers can transmit the force exerted onto the framing which deflects and transmits it onwards to the test structure.
Happily, the difference between a pass or a failure of these types of tests can be as simple as a change in the gasket material or a slight increase in rebate which completely changes the level of performance. This change is achievable at minimal cost to developers whilst satisfying their clients/tenants.
Modern façades mostly use aluminium mullions, and as designs become both larger, more sustainable and more transparent there are often unforeseen negative consequences for the blast performance because systems then suffer brittle rather than ductile failures.
Commonly unbalanced design is a failure where the façade structure, the mullions and connections to the wider structure fail before the glass itself fails and it’s a dangerous condition which in a modern office can lead to a wall of glass being ejected across a floorplate as shown in the first video.
Early engagement with blast engineers can massively increase the resilience of glazing to required levels for minimal costs as the recently tested commercial facades from suppliers like Schüco, showed with their FWS 50 façade system. There the enhancements needed only minor changes such as additional screws in the mullion to transom connections which would add as little as 7 – 15 % to a façade cost and may reduce the need for costly bollards; saving money overall.
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