Deflection Induced Moments in Struts BS5950

[countervail]

Does anyone know of any guidance given in BS5950 (or anywhere else) about the level of deflection in struts (say horizontal roof bracing) before I have to add extra moment due to compression in the member acting a distance from the original centreline of the member.

 

[apsix]

Not a direct answer, but the attached shows the reduction of compression capacity with increasing length, for a selection of SHS struts.
It shows that deflection due to self weight is significant for effective lengths between 2 to 4 m, for the SHS sizes shown.
Capacity design was done to AS4100.

 

[SarkTower]

If my memory serves me correctly, the old version of BS5950 did have a clause which gave guidance on this. Compression members with a slenderness greater than 180 were to be checked for deflection due to self weight. If this deflection exceeded length/1000 then the resulting moment due to this eccentricity was to be included in the design. I'm not sure why this clause disappeared in the new edition.

 

[csd72]

You should ALWAYS check this until you have enough experience to know otherwise. It is always amazing how much a little bit of self weight reduces the axial capacity.

 

[countervail]

Thanks all