During recent design and analysis considerations of metal-structures, and for all practical purposes, the fundamentals for the design of stiffened-diaphragms shall be differentiated from that of the "standard" unstiffened-diaphragms. This can mainly be attributed due to the fact that the designed and analyzed project specific bearing-stiffeners act two fold and are intended to resist the "out-of-plane" bending moments, and also are contributing as "load-bearing" stiffeners. This is especially important when considering the relatively narrow widths of the diaphragm- plates, which is utilized to further direct and ultimately transmit the project's required vertical loads to the subject bearings. It needs to be realized, as most of us are aware, that the stiffener plate-panels shall only be designed and analyzed with respect to the required shear transfer and transverse stresses. Through the overall stiffener plate partitioning into smaller, yet refined, sub-plate panels, the secondary stiffeners accomplish their purpose and achieve stabilization. By implementation of a simplified analysis, the in-plane transverse stresses in the diaphragm plate can be determined. Note should be taken that the secondary stiffeners are often neglected and not considered when determining the diaphragm properties and criteria.
Do You consider plate-panel corner stresses, and possible "in-plane" bending stresses, due to Vierendeel action around significantly sized openings, and then add the results to other in-plane stresses, or do you also consider other effects and conditions that you are adding as well?