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

摘要

The long-term creep deflections of three wood framed floor systems were measured for a duration of three months. One floor was constructed with No.1 Southern Pine solid-sawn floor joists, which served as a control; two floors were constructed with wood I-joists fabricated with oriented strandboard webs and laminated veneer lumber flanges. All of the floors were sheathed with oriented strand board (OSB) panels, nailed and glued to the top edges of the joists. A sustained load of 0.96 kPa (20 psf), which simulates the dead plus sustained live loads for residential applications in the United States, were applied to each floor for the duration of the three month test. Initial and time-dependent deflections were measured at mid-span of each joist in each floor periodically during the entire three-month period of the test. Temperature and humidity were maintained between 20 and 22 ℃ and between 40 and 60 %, respectively. Creep deflections of the floors equilibrated after 72 days, of sustained loading. Average midspan creep ratios (Total Deflection/Instantaneous deflection) of the joists of the solid-sawn and I-joist floor systems were 1.78 and 1.63 respectively.