Blast “Proof” or Blast “Resistant” Engineering
Summary: Recently, the Victorian Police Minister announced the development of a new “blast-proof” and “ram raid-proof” tower in Melbourne CBD which will house 2,500 police over 39 storeys.....
The question is whether any building can be engineered to be truly blast and ram raid-proof.
A Rolex may be waterproof to 150 metres, but it is not truly 100 per cent waterproof.
We know politicians are well known to use poetic license and use language to catch the headlines.
Instead of calling a building "blast-proof" or "ram raid-proof," the more accurate terminology is “blast-resistant” or “ram raid-resistant” construction.
As part of the design process, structural engineers, blast consultants and other related professionals need to engage with each other and the architect. This needs to be a coordinated and collaborative effort. Firstly, there needs to be established a threat level and a performance (blast and ram) level for the structure to withstand.
The most effective defence for blast defence is to establish a safe perimeter that deploys systems to thwart the attackers' approach. A distance of just three metres can substantially reduce the effect of an explosion.
Further, the slab and framing must account for a change in pressure caused by an explosion inside the building. An internal blast will first push up the slab above, which will then rebound. This requires engineering to account for these added loads upon the structural members of the building.
The blast effect upon exterior and interior columns is a significant consideration. In some instances, the external column is eliminated altogether due to its accessibility, with an alternative solution of more extensive and robust internal reinforcement of columns and beams.
Masonry construction walls are another important aspect of engineering design, with bearing wall structures requiring special attention in the case of a front bearing wall being destroyed. Cantilevering designs may be utilised in such instances. Floors and roofs must be capable of resisting failure.
Windows as well as other building elements may need to be designed to withstand wind loads by a factor of 10 above normal wind loads. Specialist material suppliers who can provide tailored materials and building components will need to be engaged.
It is essential that oversized elements are properly assessed during initial design to avoid costly redesigns, contractual disputes, potential delays and damages claims during the construction period.
A properly engineered and designed building will save lives and reduce the risk of injury. Notwithstanding these significant advantages, there can be no guarantee from complete loss and damage.
It is an unfortunate aspect of our times that we must take account of terrorists and unbalanced violent individuals.
However, on the positive side we can take away the comfort that governments are acting to ensure that the built environment is a safer place for our predominately law abiding community.