Photographs taken twenty five years ago of the Ehzer Bridge over the Twente canal in Almen, reinforce the reputation of the performance of a galvanized coating. Originally erected quickly by Canadian troops in 1945, in support of the liberation of the Netherlands, the structure is still sound today. It represents a landmark erection for the Dutch galvanizing industry, despite not being unique in design.
Named after the 13th century country estate, De Ehze, the bridge forms part of a small local road from Almen to Laren and is still being used by local traffic. Although it is just wide enough to allow two cars to pass simultaneously, today it is used predominantly by cyclists and pedestrians, as nearby bridges now take the heavier urban traffic.
On a revisit to the bridge, technical staff at the Dutch Galvanizers Association (SDV) were struck by its appearance.
The bridge’s general appearance is characteristically dull grey with some minimal light brown surface staining. It was noted that some remedial work has been done in the vicinity of the bolted connections and over the course of time youngsters and their spray cans have added their contribution to the appearance of the bridge also.
Most importantly the steel itself has not been affected anywhere, despite a higher level of sulphurous pollution in earlier years. Today, the low sulphur dioxide content of the local atmosphere means that predictions on anticipated lifespan can be extended several times over what was initially foreseen upon installation.
Remaining coating thickness
Coating thickness have been electromagnetically determined in a number of randomly selected areas with an average of 10 readings taken every time. At three diagonal bracing sections (150 x 150 mm) coating thickness of 74 µm, 115 µm and 219 µm were found.
At two other diagonal sections (130 x 130 mm) 69 µm and 82 µm were found. Two connecting plates were found to have 114 µm (19 mm steel thickness) and 86 µm (9 mm steel thickness) of coating remaining. In comparison with the thicknesses of the galvanizing reported in the previous inspection there is no significant reduction of the coating.
Future for the bridge
Will the road where the bridge is located remain a quiet local road or will heavier traffic need to pass over it in due course? Or could the use of the canal change and require a change in bridgespan? Whatever happens, if it is left alone the Ehzer Bridge will remain to witness the changes.