A tilting nib (Dutch: kantelnok) is a structural device used in fire compartmentation. It is a nib (a projecting part) welded to a bracket on the fire wall, on which a beam rests. In a fire, if the beam deflects or fails, it can tilt freely about this pivot point without dragging down or damaging the fire wall.
Why a tilting nib?
In a fire, steel heats up and expands; eventually a beam may deflect and fail. If that beam is rigidly connected to a fire wall, there is a risk that it drags the wall down or pushes it over as it fails. This could allow the fire to break through into the next fire compartment. The tilting nib prevents this by giving the beam a hinged pivot point:
- The beam can tilt freely about the nib
- The fire wall stays intact and keeps its separating function
- The adjacent compartment stays protected
For it to work properly, the bracket, the nib, the so-called nib recess on the underside of the beam, and the beam itself must be detailed so that this free tilting is possible.
Application
The tilting nib is used in steel structures where beams connect to, or rest against, fire-separating walls. It is a simple, structurally clear solution to the problem of fire walls being dragged down.
Related solutions
For the same purpose — decoupling structural parts in a fire — there are other devices too, such as the shear pin (breaking bolt) and the fusible anchor, which fail at a certain temperature or load and release the connection.
Related terms
- Fire wall
- Fire compartment
- Fire resistance
- Breaking bolt
- Bearing
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