1974 - Rigid Diaphragm analysis

Rigid diaphragm is mentioned in this NBS report from 1973. Full Scale Test on a Two-Story House Subjected to Lateral Load, Yoke, Tsai, Somes, U. S. Department of Commerce, National Bureau of Standards, March 1973.

The 1976 UBC (Archive.org) contains language regarding (effectively) rigidity being considered in force distribution for seismic loads, see Chapter 23 (General Design Requirements), Sec 2312 (Earthquake regulations), item 4. Distribution of Horizontal Shear. (you need a free account then you can check the book out for an hour and the link will take you to the correct page).

As far as an example calculation - Information on Rigid diaphragm assumption and an example of the analysis by Louis Yaw, Walla Walla University (Washington State).

Rigid Diaphragm analysis, Louis Yaw, January 4, 2022 (revised).

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Developing Diaphragm Analysis, Kennedy, May 2018, Modern Steel Construction

This article gets into the upper and lower bound limits on diaphragm forces for seismic loads (ASCE 7-10). It's based on a seminar at the 2018 North American Steel Construction Conference by the same person. Diaphragm Analysis, Design and Connection Considerations in Steel Seismic Force Resisting Systems [N18]

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