CREEP BEHAVIOR OF SOLID-SAWN AND WOOD I-JOIST FLOORS

Abstract

The creep responses of twelve individual I-joists and six wood-framed floor systems were measured for a duration of approximately 120 days. The I-joists and floor systems were divided into two sets, each having six individual I-joists and three floor systems. The study I-joists were fabricated with laminated veneer lumber (LVL) flanges and oriented strand board (OSB) webbing. The floor systems included one floor framed with No. 1 Southern yellow pine floor joists, which served as a control, and two floors constructed with wood I-joists. All floors were sheathed with OSB panels, nailed and glued to the top edges of the joists, and were designed to carry a total dead plus live load of 2.40 kPa (50 psf). A sustained load of 0.96 kPa (20 psf) was applied for the duration of the experiment. Relative humidity and temperature were maintained between 34% and 60% and between 22°C and 26°C (72°F and 79°F), respectively. The overall average creep ratios (total deflection/instantaneous deflection) of the I-joists, I-joist floor systems, and solid-sawn floor systems were 1.66, 1.53, and 1.71, respectively. The creep ratios of the I-joist and solid-sawn floors were not significantly different (p > 0.05). Observed creep ratios of the solid-sawn floors were greater than those reported by prior studies for nailed solid-sawn floors; observed creep ratios for the I-joist floors were lower than those reported by prior research for a similar, but not identical, I-joist floor system.