Verification of a mathematical model for layered T-beams

CER73-74MLK-MEC-JRG-JB-EGT-MDV28.March 1974.Includes bibliographical references.An experimental program and the verification of a mathematical model for layered T-beams, developed assuming small deflection theory and including effects of interlayer slip, are described in this report. This research is a part of an overall program to develop a verified analysis procedure for wood joist floor systems. After a description of the construction and load-testing of 14 two-and three-layered T-beams, a brief discussion on the mechanical properties of the materials used is given. The deflections observed in the loading tests are then compared with the predicted deflections given by the mathematical model, which used a finite element solution technique. These comparisons for the fourteen T-beams, including two and three-layered systems, formed the primary basis for the verification of the mathematical model. Test results provided by a manufacturer of joist systems were also compared to the mathematical model. Good agreement between the observed and theoretical values were obtained for all tests. These favorable results show the validity of this general layered beam theory

Variability simulations of joist floor systems

September, 1974.Includes bibliographical references (pages 56-57).This thesis examines the use of the Monte Carlo method for studying the effects of component variability on the deflection behavior of wood joist floor systems. The study considers random variations in joist modulus of elasticity within a lumber grade and evaluates this effect on floor deflection behavior. Simulation results indicate that there are two basic effects induced on deflection behavior by joist modulus of elasticity variability. These effects are changes in mean maximum floor deflection and maximum floor deflection variability. A means for seeking optimum economic efficiency through restricting component variability to a value that yields the best floor maximum deflection response to component cost relationship can be formulated from floor maximum deflection distributions. The study emphasizes that important roles of structural interaction and component variability on structural performance. For floors in which a deflection criterion governs design, the design calculation is normally based on the deflection behavior of joists with average member stiffness acting alone. This method of design normally does not include the beneficial effects of load sharing and composite action nor the detrimental effects of component variability. Design analysis based upon a joist-acting-alone behavior assumption does not necessarily describe the behavior of floors within the design. The effects of structural interaction and component variability need to be evaluated for floor behavior to be accurately predicted.Final Report to the Engineering Foundation for Grant RC-A-74-6