Slotted hole for purlins with flange brace

[tristan861]

I was wondering about that for a few days, (Excuse my question if it was kind of stupid or if I'm missing something).

Usually when I brace rafters with flange brace on a FEM, purlins fail due to compression buckling.

Since purlins would buckle easily,Shouldnt the connection of the flange brace or purlins connection to be always with slotted holes from one side to prevent tranfering its axial load to purlins?

Thanks in advance.

 

[Agent666]

My opinion.... If you're not transferring the axial load or more correctly resisting the horizontal component of the brace force being transferred to the purlin.... you're accepting that the top of the brace can slip horizontally.... which in turn means the bottom of the brace cannot restrain the flange from also moving laterally ..... which is the whole point of the fly brace in the first place.

https://engineervsheep.com

 

[KootK]

I second Agent's response. A point brace on wheels isn't much of a brace.

Usually when I brace rafters with flange brace on a FEM, purlins fail due to compression buckling.

Is it accurate to assume that it is your finite element model, under the action of gravity load, that is producing this failure? If so, it may be an instance of your modelling capturing real world behavior in aa way that is both more accurate, and less convenient than a conventional, by-hand design of old. And we may be able to do some things to help rectify that.