Factor of Safety on Macomber Joist
Factor of Safety on Macomber Joist
(OP)
Hi all,
I am looking at an old Macomber joist for some revised loading and I am curious about the published safety factor of 1.65. Does anyone know if this was a code requirement or could this safety factor potentially be reduced with engineering judgement? Appreciate your thoughts and thank you to all those who took the time and effort to make the load tables available online!
waytsh
I am looking at an old Macomber joist for some revised loading and I am curious about the published safety factor of 1.65. Does anyone know if this was a code requirement or could this safety factor potentially be reduced with engineering judgement? Appreciate your thoughts and thank you to all those who took the time and effort to make the load tables available online!
waytsh






RE: Factor of Safety on Macomber Joist
But I think it's a misnomer to call that the factor of safety. The steel very seldom yielded at exactly 36 ksi, usually it had a lot larger yield point. This was the point where the far edge yielded, so there was a lot of member left to yield. There was strain hardening. So the steel has a lot of excess capacity.
I suspect that Macomber did calculations and used a similar design method. If it was good enough for a steel beam, it was good enough for them. But who knows what controlled? It could of been compressive buckling of the top chord. I wouldn't want to eat into that F.S.
My point is, without some inside information on what controls in these joist designs, I wouldn't mess with the F.S.
RE: Factor of Safety on Macomber Joist
RE: Factor of Safety on Macomber Joist
RE: Factor of Safety on Macomber Joist
RE: Factor of Safety on Macomber Joist
thread507-287669: Macomber Joist
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.