flexible diaphragm
flexible diaphragm
(OP)
I need some interpretation of section 12.3.1.1 Flexible Diaphragm Conditions per ASCE 7-05 page 124, quoting:
"...in which the vertical elements are steel or composite steel and concrete braced frames, or concrete, masonry, steel, or composite shear walls."
When the section refers to vertical elements are steel,.... do they mean only braced frames or they refer to ordinary and special moment frames?
I have a 2 story special moment frame with plywood floor over TJI. The plan checker is asking me to provide calculations to check whether the diaphragm is rigid or flexible. Am I missing something in the code?
Please help.
"...in which the vertical elements are steel or composite steel and concrete braced frames, or concrete, masonry, steel, or composite shear walls."
When the section refers to vertical elements are steel,.... do they mean only braced frames or they refer to ordinary and special moment frames?
I have a 2 story special moment frame with plywood floor over TJI. The plan checker is asking me to provide calculations to check whether the diaphragm is rigid or flexible. Am I missing something in the code?
Please help.






RE: flexible diaphragm
OMF/SMF are also frames. Basically it just refers to the lateral force resisting system.
RE: flexible diaphragm
RE: flexible diaphragm
I hate plan checker like this. They think we have an endless amount of time budgeted to keep working on one project.
RE: flexible diaphragm
Similarly in the second phrase, you are not suggesting that ANY construction of concrete or masonry or steel would qualify without the qualifier "shear wall", are you?
RE: flexible diaphragm
RE: flexible diaphragm
It should be read "...in which the vertical elements are steel (or composite steel and concrete) braced frames, or concrete, masonry, steel, or composite shear walls."
It's meant to be a no brainer clause to help us avoid calculation. For moment frames, it's not necessarily a no brainer and a calc is necessary.
RE: flexible diaphragm
Plywood is semi-rigid; otherwise you couldn't get a cantilevered diaphragm to work.
RE: flexible diaphragm
RE: flexible diaphragm
Yes.. you may assume they are flexible; but form an equilibrium standpoint, you MUST assume them rigid in order to design a cantilevered diaphragm. Hence, semi-rigid. (Same applies to metal deck roof as well)
RE: flexible diaphragm
NDS has a whole booklet on diaphragms in their wood design package BTW that does a good job spelling it out.