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Robustness of Buildings is explained by an example of a building collapse. The whole building collapsed due a pressure cooker blast on 20th floor.
Early one morning in 1967 a large part of the building (shown in fig.) in north London, collapsed, after an explosion on the 20th floor. The resulting enquiry led to a major developments in the way we think about design. It made designers aware of robustness.
What happened at Ronan Point?
Ronan point is a large panel structure made from precast wall and floor units.
Very early in the morning a gas cooker exploded in a flat on the 19th floor. The result provoked to be catastrophic. The explosion caused the kitchen wall to disintegrate. This led to the collapse of the flat above, since its support had been removed. All the debris from the floors above fell onto the kitchen floor which collapsed and precipitated a domino effect onto the floors below, as shown in the figures below:
Fig.2: 20th floor of the building
Fig.3: collapse of 20th floor due to cooker blast
Fig. 4: Whole building collapse due to collapse of top kitchen floor
Lesson learnt from the Ronan Point:
With regard to the Ronan point disaster, the major concern was that a relatively small and local occurrence, the explosion of a gas cooker, led to the collapse of over 20 storeys.
The was felt to be unacceptable and the requirement was stated that damage should not be disproportionate to the cause. It should not lead to the collapse of the whole building, a result which is entirely out of proportion to the cause.
The concept was developed that any single member should be able to be removed without causing overall collapse. This could be achieved in the Ronan point type of structure by tying together the members.
The connections between all members allow the floors above to remain intact and not collapse onto the floors below, should any member be removed.
More importantly for the basic planning of structures, it was recognized that structures which depend for their support on only one, or a very few key elements should be avoided, such structures are not Robust.