out of plane seismic forces in diaphragm or subdiaphragms
out of plane seismic forces in diaphragm or subdiaphragms
(OP)
How do I figure out if a flexible metal deck can handle the compressive out of plane forces needed seismic design, parallel to the direction of the deck span.
I have a building assigned to design category C. The force is calculated from 12.11.2.1 ASCE 7-05. I would like to use the deck as the continuous ties parallel to the deck span. 12.11.2.2.4 does not apply, I will be using my joist chords in that direction. I am concerned that the deck may buckle under the compressive force. Joists are spaced at 6.25 feet. I'm using 1.5 type B 22 ga deck.
Any ideas?
I have a building assigned to design category C. The force is calculated from 12.11.2.1 ASCE 7-05. I would like to use the deck as the continuous ties parallel to the deck span. 12.11.2.2.4 does not apply, I will be using my joist chords in that direction. I am concerned that the deck may buckle under the compressive force. Joists are spaced at 6.25 feet. I'm using 1.5 type B 22 ga deck.
Any ideas?






RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
Never, but never question engineer's judgement
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
What you have suggested is very good for the 5' spacing. However, I am surprised to see it (5' spacing) is the normal practice in these days. I used to place the first joist as colose to wall as possible, 1'-2' clear from wall face.
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
Never, but never question engineer's judgement
RE: out of plane seismic forces in diaphragm or subdiaphragms
The end Joist is same as the others. It is there to stiffen the edge.
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
I think every big retail box store I have ever been in with load bearing walls has a typical joist space between the first joist and the wall. You are saying the standard where you are is to provide a joist right up against the bearing wall?
RE: out of plane seismic forces in diaphragm or subdiaphragms
You made me feel anxitious on my old designs. Now I feel the urge to go back have a peek to make sure the roofs still there.:)
Yes, that's the way been done through my hand. Reasons include, but not limited to, to better handle snow drift, provide strong edges, thus improve stability at the cost of one extra joist, maybe.
RE: out of plane seismic forces in diaphragm or subdiaphragms
This might put stress on the deck to wall connection screws or welds - you could check it by looking at the midspan joist deflection of a typical joist, and seeing what sort of rotation results in the deck. From this deck bending rotation, you would be able to see what sort of bending stresses are in the deck - also what sort of prying action on the fastener might be induced.
It may not be a serious problem, but most designers I know don't put it close - and certainly don't use X-bridging or diagonal kickers between the joist and wall.
I think SJI even discusses this in their spec or somewhere - not sure.
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
RE: out of plane seismic forces in diaphragm or subdiaphragms
thanks for your suggestion of calling the deck manufacturer for compressive axial load. I will do that.
I have heard of the suggestion of putting the angles as a horizontal truss as well. I am hoping the deck will take it.
thanks everyone for your input.