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Tue, 19 Jan 2021 04:36:48 GMT

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RAM Structural System- Semirigid Diaphragm with untopped metal deck

Ally Goolabsingh — Tue, 19 Jan 2021 20:09:54 GMT

I am currently working on a model with concrete tilt walls and joist girder moment frames (using the virtual joist tables) with an untopped metal deck as my diaphragm. Based on articles I have found on this site (as well as classifications per ASCE7), it is appropriate to analyze this system as a semirigid diaphragm with an effective thickness equal to the deck thickness, Poisson's Ratio of 0.3, and an Elastic Modulus based on G'. I based the calculation for E' on the web page within this forum tilted "Example Calculating Semirigid Diaphragm E'. Based on the latest deck manufacturer's publications, the shear stiffness value G' has increased significantly based on changes to the latest versions of IBC and AISI, as well as an overall increase in Fy of the deck. In addition, the value increases significantly when considering a lapped end vs. a butted end condition. Is it still appropriate to consider the system to have a semirigid diaphragm? The load distribution to the frames when comparing psuedo-flexible to semi rigid are significantly different since the deck stiffness increased. Are there any considerations I may be missing?

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RAM Structural System- Semirigid Diaphragm with untopped metal deck