Section 12.3 of ASCE 7 - 22 states that unless a diaphragm can be idealized as either flexible or rigid, structural analysis should explicitly include consideration of the stiffness of the diaphragm (i.e. semirigid modeling). I am publishing an article in a technical magazine in which I describe how I use STAAD to determine seismic shear stresses and lateral deflection in a model based on the deck's gage, span, shear modulus, system of fasteners, and an equivalent steel plate of uniform thickness. I attached a copy of my article to your service request form #CS0525388 and received a response from your viewer that said my "methodology is valid and I should submit this idea to you for enhancing your STAAD software". The need to accurately identify steel deck shear stresses and lateral deflection is critical to the structural design of our projects here at Carollo Engineers, particularly in high seismic areas. I would be happy to review the methodology with your software development engineer, if you wish.
It appears to me that my proposed methodology for designing corrugated roof deck diaphragms, above, could be implemented by your engineers to provide the STAAD design methodology that has been suggested in the other posted idea titled "ADD FLEXIBLE/SEMI RIGID DIAPHRAGM". In general, I believe that you could create tables that allow the design engineer to select the appropriate shear modulus G, modulus of elasticity E, Poisson, Alpha, Damp, Strength Fy, so that it also enables the engineer to quickly identify the thickness of the solid steel plate used in the design model. Therefore, the steel plate of uniform thickness in the model would be precisely equivalent in stiffness/flexibility to the corrugated steel deck selected for final contract drawings. The steel plate would typically be between 3/16" to 3/8" thick. The density of the steel deck would be adjusted to account for miscellaneous weights of roofing materials, insulation, utilities, etc that are part of the roof. Phil Riegel has reviewed my design methodology and agrees it's workable.
Thank you for posting this idea. We have one other posted idea which will be linked here that conceptually suggests providing a method for defining semi-rigid diaphragms. We should clarify if the method proposed here would meet their requirements too.