Light-gauge cold-formed steel studs are commonly used in the construction industry as interior drywall studs for partition walls, ceilings and soffits. These partition walls consist of cold-formed steel studs, spaced at 12, 16 or 24-inches on-center, with different thicknesses and grades of drywall attached to each face of the stud. The steel stud and drywall assembly performs as a composite system to resist the interior pressures that develop within a building. In addition to variable design pressures, building designers can specify tighter deflection tolerances to reduce the effect of deflections on connecting systems. While the system is non-load bearing (i.e. does not contribute to the structural system) failure of the system is unsightly and can be avoided.
To increase the practice of specifying these types of assemblies, code agencies and steel stud manufacturers have developed test criteria to determine the maximum limiting wall heights that a given cold-formed steel stud and drywall framing system can attain. When a manufacturer develops a new cold-formed steel stud profile, a test program is initiated to determine these limiting heights. Representative assemblies are tested and used to determine the limiting heights for a range of stud depth, stud spacing, deflection limit and interior pressure combinations.
CTLGroup engineers analyzed wall assembly test data provided by the client to determine the limiting wall heights for cold-formed steel stud and drywall assemblies. The analysis was performed according to ICC-ES Acceptance Criteria AC86, following versions from 1995, 2008 and 2010. The different versions were used to evaluate the impact of evolving criteria on the calculated limiting height. The analysis included interpolation of limiting heights for intermediate stud depths and stud spacing, since testing of each representative assembly is both time and cost prohibitive.
The results of the analysis produced limiting height tables, which the client provides to designers and engineers to increase the use of their products. The analysis also highlighted the differences in acceptance criteria, specifically the more restrictive 2008 criteria which included a larger factor of safety for the test results.