How are protective features related to the importance of a structure?

It acted as a safety net in case the structure collapse.

Explanation:

When building public infrastructures, a collapse in the structure could potentially resulted in large number of deaths.  This is why architects added protective features to the crucial components of the structure.

The protective features were designed to minimize the damage when there is some sort of problems in the crucial components of the structure.

When creating bridge for example, protective features often added to the foundation to ensure that the bridge wouldn't collapse completely in case one of the foundations is destroyed,

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Explanation:

erosion.