I would like to put a trestle on the layout. I want to use wood stringers across between my bents. The gap I want to cross is about 45 scale feet. I have looked at so many pics on the net and in books. I have seen a wood stringer on doubled up bents at each end that is close to that large of a crossing. The number of stringers on that crossing made a solid deck under the ties. The question is what is the longest span I can have using wood stringers on wooden pole bents?
The second question is, are steel plate girder bridges ever supported by wood pole bents at each end?
The typical distance between bents on a wooden trestle would be in the neighborhood of 15 feet. On a mainline railroad for most of the 20th century, there would be something like 4 or 5 8by18-inch stringers set on edge under each rail.
Since the typical girder bridge is much longer than a 15-foot span, the load at the bridge ends would be much greater than on a wooden trestle. Thus, it would be unusual/unwise to support the ends with wooden bents although the issue would be reduced if double bents were used at each end.
A couple of days ago on another thread discussing bridges, I posted a photo of a girder bridge where one end was approached by a wooden trestle, but there were concrete piers at each end of the girder.
