Performance of Bridge Timber Ties under Static and Dynamic Loading

A dramatic increase in railway car axle loads has occurred over the past 50 years. This paper presents the results of an experimental program undertaken at the University of Manitoba to evaluate the structural performance and durability of treated timber bridge ties under different load levels. A portion of a prototype bridge deck, consisting of eight prototype timber ties, was tested under various loading and support configurations using segmented railcar wheels, rails, and tie plates to determine the axle load distribution on the timber ties. Test results were compared to a theoretical model, based on energy principles, used to predict the axle load distribution on the ties for different bridge configurations. The shear strength of the timber ties was determined using nine large-size Z-shaped shear specimens with different shear cross sections machined from the same timber ties. Material properties of timber were obtained using bending tests of full-size treated bridge ties. Serviceability of the treated timber bridge ties is also presented and discussed, based on fatigue testing of prototype timber bridge ties under different load levels.