Effective Properties for Stair Tread Diaphragm

[sauce_man]

Hello,

Working on a vibration study for stair structure. I am wondering if anyone has seen documentation or has any logical methods for determining the effective diaphragm stiffness properties for stair treads. I also want to explore a box type structure, since the fabricator wants to build in segments, in which case there would be a bottom plate and tread plate attached to the stringers. I am also thinking about how to model such a box element in a two-stringer model.

Cheers,

 

[driftLimiter]

Have you looked into AISC Design Guide 34? There are some brief references to tread plate landings being treated like steel plate shear walls. There may also be some other useful considerations in DG 34 regarding modeling etc.