Metal-plate-connected joint and lumber safety factors and their influence on wood truss safety factors

Abstract

A model that simulates test of metal:-plate-connected wood trusses was developed. The truss test model built on previous research efforts to simulate ultimate failure of structural systems. For years, lumber failure models have used failure equations that were derived from design equations. This approach was applied to the strengths of metal plate connected joints. The model uses actual steel properties data for modelling the strength of the joints, and uses the most current lumber data to model the lumber strength and stiffness properties in the trusses. One of the unique features of the model is the use of basic fundamental engineering properties to predict the strengths of the individual components of the structural systems. These general principles allow the model to be used for many truss configurations. This flexibility differs from several current metal plate connected wood truss models in the literature.

Although the safety factor for lumber is the smallest of all the truss components, many of the simulated truss failures were controlled by plate failures. The metal plate connected joints were the weakest link in the truss system. To improve the overall strength of a truss, the plates would need to be strengthened.

Two different truss configurations were used for the simulations. Both truss simulations performed well, when compared to actual test data.