Loosening bolt shear connections

[capablanca]

Sirs:
This is a typical problem that presents in telecom
towers.I am refering to standard shear connections such
as between diagonals and goussets.These connections are
not slip critical and get loosened by the tower vibrations.
Eventually the bolts fall down.My interest is to knoww
an easy solution to this problem.In our case we detected
that in one year the bolts are loose.Thanks!

Capablanca

 

[Ron]

Just because a connection is not slip critical, doesn't mean that it wouldn't benefit from proper bolt tensioning. (Lots of negatives there...read it twice!). Even though not slip critical, consider tightening the bolts to a consistent tension, even if not to the level of a slip critical connection. Remember, towers are subjected to repetitive, reversing loads so fatigue and the loosening associated with such can be critical.

Another consideration is to use lock washers.

 

[RalphChristie]

Lock-washers or lock-nuts (use more than one nut on a bolt)

Regards

Ralph

 

[MikeDB]

The use of lock nuts or lock washers along with proper tensioning of the bolts will help. However, they do not do anything to reduce the vibration. Some slender tower members are prone to aeolian vibration which can lead to fatigue failures. If your towers have severe vibration, you should look into that. Members with larger l/r values or the addition of dampers may be warranted.