When is diaphragm action a necessity in floor deck systems
When is diaphragm action a necessity in floor deck systems
(OP)
This one has always been a gray area to me.
You have a steel frame with joists to form a floor structure and you top it with trapezoidal deck and concrete topping.
In a seismic area I would utilize diaphragm action for better load distribution between frames. I would do this by using shear studs. This also gets me some composite action.
When seismic or wind load is not dominant I would simply brace the floor with horizontal bracing and I would ignore studs. The deck will be in place with the simple "nail " kind of fasteners. The braces distributes the load just like a diaphragm would at a lesser cost.
When no lateral load is available and I am relaxed with the stiffnesses of my sway frames and about sure that they have almost proportional sway stiffness, I would ignore bracing.
How do my friends approach this subject?
Regards
IJR
You have a steel frame with joists to form a floor structure and you top it with trapezoidal deck and concrete topping.
In a seismic area I would utilize diaphragm action for better load distribution between frames. I would do this by using shear studs. This also gets me some composite action.
When seismic or wind load is not dominant I would simply brace the floor with horizontal bracing and I would ignore studs. The deck will be in place with the simple "nail " kind of fasteners. The braces distributes the load just like a diaphragm would at a lesser cost.
When no lateral load is available and I am relaxed with the stiffnesses of my sway frames and about sure that they have almost proportional sway stiffness, I would ignore bracing.
How do my friends approach this subject?
Regards
IJR






RE: When is diaphragm action a necessity in floor deck systems
RE: When is diaphragm action a necessity in floor deck systems
The critical issue with flexible diaphragms come at the boundary where the lateral load is passed off to a supporting edge collector. This is usually a fairly brittle connection (the weak/brittle link in the chain) and its very important that you design for a higher load capacity here (in fact: the codes usually require you to do so).
Also, a deck diaphragm without concrete is considered flexible (usually) and additional requirements for attaching load-bearing masonry or concrete walls is prescribed as well.
We almost never use additional bracing in the plane of the diaphragm when using metal deck diaphragms unless we can't get a particularly high shear to work with the deck we specify.