I’m also having a hard time imagining how it looks like. I already did some searches on the web but I still don’t understand it. Thank you for your time.
In: Engineering
Is this question in relation to UL fireproofing rating for beams?
Found a description here: https://www.promat-india.com/en/about-passive-fire-protection/products-and-application/unrestrained-restrained-beams
Restrained beams are perminently affixed to the surrounding structure, while unrestrained beams have no mechanical fixture to the structure.
Its explained that the importance of this difference comes into play during a fire.
Normally, when metal is heated it expands. So when an unrestrained beam is heated from a fire, it lengthens, which reduces structural integrity and can lead to flexion or breakage. When a restrained beam is heated in a fire, because it’s affixed to the surrounded structure and can’t push the structure away to expand, so as a result it tends to compress instead. While compression isn’t ideal because it’s still altering from its designed condition, it’s a safer and more sound result than expansion.
The material discussed in the article (SFRM – Spray Flame Resistant Material) is a flame retardant that gets sprayed onto a buildings structural members to increase the amount of time before a fire can affect the structure. Since an unrestrained beam has higher potential to fail in a fire, additional SFRM is applied to protect it. Basically, you’re paying for extra fireproofing to save some money on the structural construction.
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