High water kept me from getting much while I was here.
Photo taken by Dylan VanAntwerp in June 2013
BH Photo #269772
Actually, it's Dylan and I am not the one who took the construction photos, but thanks for your response!
You were lucky because you actually got to see the pre-stressed box beams before they were installed... you can see in your photos how they are hollow inside (hence the "box" designation). You can also see in your photos that before they are erected, they are individual beams, although if they are lined up on the bridge right beside each other (called Adjacent Box Beams) they have the appearance of a slab after being erected. This type of bridge is often called a Pre-Stressed Concrete Adjacent Box Beam (or girder) bridge. In dealing with historic bridges as those seen on this website, "concrete slab" typically refers to a traditional reinforced concrete structure with rebar inside, which is a poured concrete slab, rather than precast beams arranged to form a slab-like structure.
What is the correct terminology for the precast concrete structure that replaced the west approach trestle on this bridge? I have seen these referred to as concrete box girders. Is this the correct designation? What is the difference between these and a concrete slab bridge or a concrete stringer?
I drove past once but didn't stop. Looks like you can just park along the shoulder and get out.
is one able to park along the new highway? It certainly would seem to make getting this bridge easier.
This bridge is now much more accessible with the completion of Highway 100/Collins Road.
The stone pier that used to rest under the old north approach trestle used to support a fourth TPG span. A derailment in the 1970's on the CRIP destroyed the TPG span and severely damaged the pier. The CRIP replaced the TPG span with a open deck pile trestle that they tied into an existing approach trestle that also received some damage in the derailment. I have a copy of the newspaper article on the derailment somewhere, if I find it I will try to post it.
The damage from the derailment and the hasty construction of the replacement trestle resulted in significant settlement problems with the timber trestle, so the IANR replaced the north approach trestle with a BNSF/UP joint standard precast concrete trestle. To satisfy the DNR hydraulic requirements, the stone pier was removed when the trestle was reconstructed.
I think the unused stone pier under the approach is from the flood of 1960 (when the girder was built), as that flood created problems in southern Minnesota and northern Iowa. Just a guess.