PREDICTING THE STRENGTH OF WOOD-JOIST FLOORS.
Abstract : This study was intended to explore the relationships between strengths at first rupture predicted by linear and nonlinear models for wood-joist floors of a given configuration but having various combinations of joist material properties. The study produced two ways of altering linear models to account for the nonlinear behavior of nails in floors loaded to failure. The strength at first joist failure of 72 floors was analyzed using linear and nonlinear finite-element models and statistical comparisons. The results of the study are presented in two forms. The first is recommended factors by which the predicted failure loads from the linear analysis can be scaled to give failure loads consistent with the nonlinear analysis. The second is recommended substitute nail stiffness which can be used in a linear analysis to predict floor responses with near-equivalent accuracy as provided by a nonlinear analysis. The results presented are specific to the floor design used in this study, but similar techniques could be used to derive equivalent information for other floor designs.
FEAFLO: A program for the analysis of layered wood systems
Abstract A finite element method for the analysis of planar layered wood systems is described. The method includes the effects of slip between layers due to fastener deformations, orthotropic material properties and gaps in layers. The method was used in developing program FEAFLO (Finite Element Analysis of FLOors). Data computed at each node include the deflection, rotations, fastener forces and for each layer the axial displacements, axial forces, moments, shears and extreme fiber stresses. The method was verified by comparing measured and predicted behavior for T-beams and wood joist floors. A listing of program FEAFLO, written in ANSI FORTRAN IV, is given. The input and output data for an example floor are also given.
Wood Joist Floors: Effects of Joist Variability on Floor Stiffness
Abstract : A theoretical study was conducted of the performance (deflection) of wood-joist floors subjected to distributed loads. Eleven 'benchmark' floors, typical of current construction practice, were analyzed. Results demonstrated that composite action, ignored by current design methods, can be substantial. Performance distributions were calculated for five floors from available joist stiffness data. Results showed that even when the joist stiffnesses are below design values, composite action reduces deflections to less than allowable design levels. The effects of joist variability on floor performance variations were studied by assuming distributions of joist stiffness, and calculating corresponding distributions of floor performance. Results demonstrate how joist variability is reduced when the joists are assembled into complete floor systems. The results of these analyses provide valuable data on the current performance levels of wood-joist floor systems, and the methodologies developed will be of benefit to future efforts in this area. (Author)