My plate girder bridge is based on photos and some crude drawings of the D&RG plate girder bridge on Mill Creek near Silverton.While the plan is as exact as possible as to overall dimensions there are slight discrepancies in some of the material sizes due to the use of readily available scale structural angles and beams. Also, the actual bridge was fastened with thousands of rivets and, of course, the model does not   show these. The material used in the model is ABS plastic as it is much more durable outdoors in sunlight that the styrene often used for models. It is 50% more rigid as well and bonds easily and quickly.