Finite Element Model for Predicting Stiffness of Metal-Plate-Connected Tension-Splice and Heel Joints of Wood Trusses

Abstract

A finite element model that predicts axial stiffness of metal-plate-connected (MPC) tension-splice and heel joints of wood trusses is developed. The commercial software ABAQUS was used in developing the model. The model was based on: (1) the assumption that the joints are two-dimensional, (2) plane-strain modeling, and (3) the assumption that the properties of the wood and metal plate are linearly isotropic. The interface between the wood and the teeth of the metal plate is modeled with a finite sliding formulation. Contact surfaces (rather than contact elements) model the slip of the teeth of the metal plate and shear at the wood-tooth interface. The tangential contact properties are set to a specified coefficient of friction while the normal contact properties are set to a "hard" contact formulation, allowing for a possible separation of the nodes after contact is achieved. Model predictions are validated against experimentally measured stiffness values obtained in the literature. The data cover two wood species and three levels of modulus of elasticity (MOE). On the average, the model predicts within 5% of the experimentally measured stiffness values. The unique features of the model include: (1) accounting for friction at the tooth-wood interface, (2) accounting for tooth slip, (3) requiring no empirical factor (such as foundation modulus) in predicting axial stiffness, and (4) using the same methodology in modeling tension-splice and heel joints.