Hi there, I may have a somewhat of an odd question. Please consider these two drawings/copper engravings:
https://upload.wikimedia.org/wikipedia/commons/f/f6/Frankfurt_Am_Main-Matthaeus_Merian_der_Aeltere-Ansicht_von_Suedwesten.jpg and https://upload.wikimedia.org/wikipedia/commons/e/e7/Frankfurt_Belagerungsplan_Faber_1552.jpg
Please center your attention on the Old Bridge of Frankfurt/Main. Stream upwards there are what appears to be logs, erected at a sharp angle stream downwards, as well as other smaller logs erected vertically further up stream (only visible in the Merian copper engraving).
The shallow angle ones remind me of "Hemmbalken" used on the Atlantic Wall pre Allied invasion.
What would the purpose be? My initial though is "guard rails" so that ships which float downstream don't impact the bridges, could that be correct? Or just another measure against floating ice so the bridges don't have to rely on their massive icebreakers alone?
Yes, bridge piers and abutments are nearly always protected by fenders or freestanding dolphins, a practice that dates back centuries. Sailing ships and barges can't always be maneuvered precisely, and wooden pilings are much cheaper and easier to replace than bridge components. The idea is that deformation of the timber, or more modern cellular metal structures, will absorb energy and protect the bridge without sinking the vessel.
