RELIABILITY OF WOOD JOIST FLOOR SYSTEMS WITH CREEP

Light-frame wood floors are constructed from a number of parallel flex ural members (joists), which provide the primary structural support. S heathing material is attached across the top edges of these joists to form the floor surface. Because the joists are connected in this manne r, load sharing occurs, which enhances the performance of the system a s a whole. Current design procedures focus on the behavior of single m embers with only limited provisions that account for the improved perf ormance of systems. In this study, the reliability of wood joist floor s is investigated considering both strength and serviceability limit s tates. The objective of the system reliability analyses is to determin e appropriate system factors for use in single member load and resista nce factor design checking equations. These factors are included to ac count for the beneficial effects associated with systems, of parallel members. This study considers factors such as lumber species and grade , floor size, and the effects of creep deformations. A stochastic visc oelastic stress-strain relationship is used to model the time-dependen t behavior of wood, and stochastic pulse process models are used to ac count for the temporal variability of the loads. Cumulative damage ana lysis using two common damage accumulation models is used to account f or the time-dependent strength of wood flexural members.