Railway bridge near Winchfield/the M3 - brick arch and flat design. Why?

[Lockwood]

I've seen this a few times. Keep wondering about it. Saw it again today. Can't find it on Streetview. I'm sure it was on the right as we were going southbound...

There is a viaduct made up of a few brick spans, then a "plain" metal span for want of a better word.

How come this has such a design?

(I will try and find a picture of what I'm talking about!)

 

[Flange Squeal]

I’m guessing you are referring to Old Potbridge Road - the tallest of the bridges between Winchfield and Hook?

Link to a photo on Trainspots website for nearby Potbridge/Totters Lane bridge (scroll to photo of Class 450): https://www.trainspots.co.uk/locpage.php?ts_number=249

Link to a Flickr photo: https://flic.kr/p/2qNEi7K

 

[Snow1964]

The embankments in the area have slipped many times, and during the construction of M3 (I think this section opened 1972) piled retaining walls were constructed either side of new M3 bridge (as if it had extra long abutments) to help stability.

The bridge you refer to was originally a multi-arch span, but presumably they found it easier to build two brick piers and add a metal span during the quadrupling. I would need to look it up for dates, but I think the section near Fleet and Winchfield was last part of 50 miles from Waterloo through to Worting Junction, and was complete around 1902.

The next bridge along, Totters Lane, also has metal span across the widened to 4 tracks, so I guess that was style used during the widening.

 

[Benjwri]

Looking at historical maps the bridge dates from the four tracking of the SWML in the area in the very early 1900s. Previously the railway passed under in a tunnel.
Looking at the bridge the with of the tracks is greater than that of an arch. In that era it’s likely construction of a brick bridge was cheaper, so my best guess would be the assumption that a metal span was required as a brick arch could not withstand the height and width required.

The bridge you refer to was originally a multi-arch span, but presumably they found it easier to strengthen two piers and add a metal span during the quadrupling.

I’m not sure this is correct? The road didn’t cross the railway by bridge before four tracking. Historical maps from 1897 show this. Four tracking was completed in 1906 I believe, and maps from 1909 show the railway four tracked and now with a bridge. I would be extremely surprised if the bridge was built for any other reason than to replace the tunnel instead of widening it, and therefore it would have been built for 4 tracks from the outset. As above I would suggest given the embankments and instability a larger arch couldn’t be provided and therefore a steel section had to be used.

 

[Lockwood]

Thanks - I was looking for a rail-over-something bridge, and then questioning how I knew it was a rail bridge!
Yeah, that's the one. I guess it jumps out as being an odd design, but other details came into my mind to push that bit out