Glued laminated timber (glulam) has the dimensional stability, strength, and fastener values that make it an ideal product for railroad bridge components, including ties, stringers, and deck panels.
The Glulam Advantage for Railroads
Dimensional Stability – Glulam is manufactured from kiln-dried lumber and has an average moisture content of approximately 12%. This means that glulam is highly dimensionally stable and that members will remain straight and true in section.
Minimal Checking and Splitting – Because glulam is manufactured at a relatively low moisture content, is has much less tendency to exhibit surface checking and splitting as compared to sawn timbers.
Higher Fastener Values – Another advantage of using a dry wood member such as glulam is that it allows the use of higher fastener design values. And, fasteners have less tendency to work out of the member as may occur with green sawn timbers.
Greater strength – The use of dry lumber combined with the selective positioning of laminations throughout the depth of the member allows the assignment of much higher stresses to glulam as compared to sawn timbers. In addition, the coefficient of variability for glulam is much lower than for sawn lumber products, resulting in highly predictable structural performance. Glulam is well-suited as a structural material to carry the heavy E-90 railroad design loads. As with all wood products, glulam has excellent dynamic performance characteristics and is an ideal material to resist the repetitive dynamic loads induced by railroad train loading.
Widely Available in a Range of Sizes
Glulam beams are widely available in a range of depths and widths. Custom beams for specially designed railroad bridges can be manufactured in virtually any size or shape, including curved beams and very deep beams.