Disproportionate collapse is the term applied to a catastrophic type of building failure in which the loss of one component leads to the progressive failure of many others, often with devastating consequences.
The Domino Effect of Disproportionate Collapse
The emotive terms ‘pancake collapse’, ‘house of cards’ and ‘domino effect’ are often used when describing the results of disproportionate collapse, which is so named because the eventual damage can be so much worse than the event which triggers it. The destruction of the twin towers of the World Trade Centre in 2011 after terrorist attacks is an obvious example; the collapse of the upper floors triggered a chain reaction lower down, causing the complete loss of both buildings.
The Ronan Point Block Collapse
In Britain, the best-known example is probably the 22 storey Ronan Point block in East London which partially collapsed in May 1968, after a natural gas explosion removed a load-bearing wall. The danger of progressive collapse, particularly in tall buildings, is nowadays much better understood, and is covered by legislation in all jurisdictions; the England and Wales Building Regulations (2004) state:
“The building shall be constructed so that in the event of an accident the building will not suffer collapse to an extent disproportionate to the cause.”
How can the risk of disproportionate collapse be mitigated?
The theoretical resistance of a building to progressive collapse is usually modelled by calculating the effect of removing one or more supporting columns. In this scenario, it is the tensile strength of the floor sections which is crucial to maintaining the integrity of the building. The ability of flooring slabs to span in two directions greatly reduces the risk of collapse after the partial failure of supports, which is why biaxial prestressed concrete, such as Flood’s, is favoured in areas prone to earthquakes.
More on Disproportionate Collapse
Flood Super Wideslab® Precast Concrete Flooring is ideal solution for dealing with disproportionate collapse or progressive collapse design because it spans in two directions. For more information contact our team at info@floodprecast.co.uk
