Diaphragm shear strength and stiffness of aluminum roof panel assemblies

• Five full-scale cantilever diaphragm tests are conducted for aluminum roof panels.
• Tests conducted in accordance with AISI Cantilever Test Method for CFS Diaphragms.
• Applicability of Metal Construction Assoc. - Primer on Diaphragm Design is checked.
• The results show very narrow scatter in tested-to-theoretical strength ratios.
• Tested-to-theoretical stiffness ratios compare well supporting proposed use of K.

A diaphragm is an assembly of planar structural elements interconnected to each other to provide in-plane bracing system and transmit in-plane forces. The diaphragm geometry, supporting frame, type of the panel profiles, the way the panels are attached to each other and to the diaphragm frame govern the overall behavior of diaphragm systems. Full scale testing is the best way to understand the overall behavior and determine the strength and stiffness of diaphragm systems.This paper is a result of experimental and analytical studies on aluminum roof panel assemblies. The main purpose is to check the applicability of Metal Construction Association’s (MCA) “Primer on Diaphragm Design” for the strength and stiffness equations when applied over a range of panel depths, thicknesses and profiles. Five full scale cantilever tests were conducted at Virginia Tech, Blacksburg, Virginia. The tests were conducted in accordance with the AISI “Cantilever Test Method for Cold-Formed Steel Diaphragms”.While the diaphragm shear stiffness development is similar for both MCA and Steel Deck Institute’s (SDI) “Diaphragm Design Manual”, the only difference is the panel edge term (K). The results of this study show remarkably narrow scatter in tested-to-calculated strength ratios. The tested-to-calculated stiffness ratios compare very well, supporting the proposed use of panel edge term (K=2/3) for aluminum diaphragms. The results indicate that the panel thickness limit can be raised safely to 1.27 mm (0.050 in.) for MCA procedures. The test data further indicate that the MCA strength and stiffness formulations work well for panels with depths through 101.6 mm (4 in.).