Structural performance of wood-based stair stringers

A study was conducted to investigate the structural performance of wood-based stair systems. OSB Rimboard specimens (32 by 302 mm [1-1/4 by 11-7/8 in.]) were evaluated as stair stringers. Nominal 2 by 10 solid sawn Douglas-fir lumber stringers were also evaluated for benchmark comparisons. The bending modulus of elasticity of individual stringer specimens was measured. Full-scale stair systems were built and loaded to design load level. The deflections of the various stair systems were measured. The stairs were also tested for their creep response with up to 19 hours of sustained loading. Some of the stair systems were also proof loaded with a 910-kg (2,000-lb.) steel plate at mid-span. A commercial finite element package (ANSYS) was used to model a stair system and gain further insights on its structural response. Such methods can be used to evaluate different material and stair designs in place of expensive experimental studies. The test results show that a simple beam model (SBM) is overly conservative for stair stringer deflection predictions. In a three-stringer stair system, the loads are almost equally distributed among the stringers. Finally, experimental results show that OSB Rimboard performed well as a stair stringer material.