Who remembers the first bridge that was built by man? May be it was a timber for building bridges, probably when someone decided to put a log over a stream to cross over. Everything was changed by development of railroads: in the 1830s, the rising value of steam powered transportations pushed the engineers to make towering wooden bridges that became synonymous the whole era.
And it was a time when US engineers surprised the world with towering timber trestles: the first railroad technology that wasn’t developed in Europe.
Instead, the Pacific Northwest of the US and British Columbia in Canada took the lead during this race, primarily thanks to the widespread availability of lumber that was readily available from forests near the development sites.
These timber trestles were generally inbuilt two designs with distinct features and functionality.
The most common of the pair was referred to as the Pile Trestle, which consisted of bents spaced 12 to 16 feet apart. Only the hardest kinds of the wood could be used for the constructions of this type.
Usually, each of those bents consisted of some five to seven poles which were pounded straight down the bottom employing a machine. For better stability, the outer posts were usually battered creating an angle outwards.
The top of the posts which were uneven were usually move level with the cap during the development , which successively provided the support for the stringers and planks that held the load of the rail.
For the taller timber trestle, the bent framed was used, the frame bents usually used the timber that was square, unlike pile bents, and sub sills or mud sills often acted because the foundation of the structure.
The scale of the constructions was impressing. These frame bents were usually between ten to fifteen feet high. The giant bridges looked astonishing, but at the same time they were not durable enough. Even massive hard wood could stand long enough and deal with fully loaded steam locomotives.
At the height of the timber bridge construction a complete of a dozen tall timber bridges was built, none of which exist anymore. Ironically, most of those highest wooden bridges were built to enable transportation of logs and were constructed within the Washington state within the US and on Vancouver Island in British Columbia, Canada.
The sad aspect of those bridges was that the logging companies often considered these bridges as a mean of sucking out the timber from a thickly forested region, once the lumber was all transported out the bridges were abandoned with none remorse.
These timber bridges were built from lumber because it was readily available and highly inexpensive as compared to steel, however, the bridges came with variety of drawbacks.
The raised intensity of transportations made these bridges weaker over time and, of course, they were still vulnerable to fire – they were made up of wood, after all. The bridges over time became weak and sometimes the workers were seen hopping off the train once approaching the weak wooden bridges only to run back then ride it after the bridge was crossed.