Structural redundancy in architecture is the ability of structures to redistribute over the elements that support less, the loads of the elements that support them at higher demand. If we transfer this concept to a building, structural redundancy relates to the number of columns and stiffening elements (concrete walls, block walls, brick walls) that cooperate against destabilising forces.
However, errors in the layout, in the execution, deficient or deteriorated materials due to the passing of time, lack of maintenance, etc., can result in the structure being less resistant than it was designed to be. To avoid these risks, structures in architecture must have a certain redundancy.
However, determining the value of structural redundancy analytically is very difficult and costly. A qualitative criterion is often used to determine the balance between a conservative structural calculation and a reasonable economic cost.
A clear example of a lack of structural redundancy is the design of the Morandi Bridge, which collapsed in Genoa, Italy, in 2018. It was a cable-stayed bridge, with only one cable-stay in each span of the bridge. The collapse of one of these stays was enough to cause the entire structure to collapse. On the other hand, if it had incorporated many more, thinner stay cables, the failure of just one of them would not have caused the structure to fail. The load supported by that brace would have been absorbed by the rest, provided they had sufficient capacity to do so.
In contrast, examples of structures with structural redundancy can be found in Roman architecture, whose buildings had many columns and large buttresses. This is why many of them are still standing today.
By Alberto López, Senior Structural Engineer in the Architectural Department of Amusement Logic
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