Deflection Design
Deflection Design
(OP)
I am designing steel roof members for a church. The roof is full of gables and also some flat areas. The gables are framed with light gauge steel trusses while the flat areas are framed with precast plank. In certain areas, the trusses and the plank are both supported by a single steel beam. My maximum span is around 30' and the ceiling structure is suspended acoustical tiles.
I am curious to see what people would use for deflection limits based on IBC. Are there reasons to put an absolute limit on deflection of a beam supporting plank?
I am curious to see what people would use for deflection limits based on IBC. Are there reasons to put an absolute limit on deflection of a beam supporting plank?






RE: Deflection Design
In the case of a roof deflecting you have to consider the consequences of deflection. the L/360 limit, if I remember correctly, was to prevent the cracking of ceiling plaster (or GWB). I have seen structures where the rotation of beams at the support ends cracked finishes. As long as the deflection is not causing roof ponding or damaging some precious architectural finish your probably okay. The ponding senario (water and/or ice) can be progressive, ie more deflection, more weight, more deflection etc.
RE: Deflection Design
RE: Deflection Design
RE: Deflection Design
RE: Deflection Design
www.SlideRuleEra.net
RE: Deflection Design
RE: Deflection Design
RE: Deflection Design
If during a heavy snow your roof deflects a lot, the occupants will become alarmed and you will get a call from them. Even if the roof framing has plenty of strength, they will be spooked and worry that their building will fall down. We are looking at such a case right now (designed by others).
RE: Deflection Design
Stanhoc
RE: Deflection Design
Stanhoc
RE: Deflection Design