Steel Roof Deck as a sub-diaphragm
Steel Roof Deck as a sub-diaphragm
(OP)
Hello Engineers,
So, while steel roof deck is not allowed to count as continuous ties for sub-diapragms across the length of the building, it is my understanding that metal deck is typically considered adequate for tension and compression bracing/anchorage of the sub-diaphragm whereas on a wood roof, plywood is not. Is that correct? Are additional struts required for compression anchorage?
Mike
So, while steel roof deck is not allowed to count as continuous ties for sub-diapragms across the length of the building, it is my understanding that metal deck is typically considered adequate for tension and compression bracing/anchorage of the sub-diaphragm whereas on a wood roof, plywood is not. Is that correct? Are additional struts required for compression anchorage?
Mike






RE: Steel Roof Deck as a sub-diaphragm
RE: Steel Roof Deck as a sub-diaphragm
Thanks for your input. That is a good point on the point load. Could the ledger angle distribute the point load into the metal diaphragm? I suppose it would need to be very stiff to distribute the load evenly to the puddle welds.
If I only go one bay with the nested tubes, then I won't meet the 2.5:1 depth ratio for sub-diaphragms? That is okay?
Mike
RE: Steel Roof Deck as a sub-diaphragm
RE: Steel Roof Deck as a sub-diaphragm
I agree. I think the tubes nested parallel to the roof deck only have to go back far enough to develop the point load.
The overlap welds and deck can take the tension anchorage from there, and the deck can handle the compression anchorage.
Thank you!
Mike
RE: Steel Roof Deck as a sub-diaphragm
RE: Steel Roof Deck as a sub-diaphragm
MotorCity,
For seismic loads, a subdiaphragm anchors a heavy wall (CMU or concrete) to a flexible roof (metal deck or plywood), because the metal deck or plywood alone could not adequately prevent the wall from separating from the roof.
A standard roof diaphragm transfers the seismic (or wind) load from the face of the building (wind) to the exterior walls (or interior walls) perpendicular to the direction of force.
Mike