Girder bridges - what is the way to go with a track base?

[RobinofLoxley]

I have acquired a pre-assembled laser cut double width girder bridge. I could simply run track across it, but then It couldnt be ballasted without difficulty. Having never seen a real life example, Im not actually sure what to do as a track base that will support ballast, which I assume is the way to go??

[zarniwhoop]

Would it have had the track "floating" on ballast ?  If you search for photos of railway girder bridges, you might find prototypes. A quick google found two types of bridge - the sort with a big framework above the track (apparently these might more correctly be called 'truss bridges'), and what I think are 'plate girder' (side panels below the track). But some of the images were of models, and might be unrealistic. Wikipedia also found 'lattice girder' which do not look like any kits I've seen!

 

My own searches for Austrian and Swiss narrow-gauge showed that the "base" tended to be a lot of closely-spaced cross-beams, with the track fixed to those and then planking at the sides (and check rails along the bridge).

 

After I found the 'truss bridge description, one of the images showed a Märklin bridge, the base had a similar but smaller 'X' pattern. But they all seem to have had similar planked walkways (except in America) and check rails.

 

edit: after posting I saw a single-track bridge with ballast, https://www.waagnerbiro-bridgesystems.com/engineered-bridges-1

 

There might be others, maybe look for cab-ride videos on youtube ?

 

HTH

 

ĸen

Edited January 20, 2022 by zarniwhoop
found one with ballast

[Lee-H]

What era are you modelling? Current railway bridges usually have a bed of ballast and conventional track but 100 years or so ago you might have had longitudinal timber rail bearers instead of the usual sleepers.

[Enterprisingwestern]

 

I'm currently adapting/bodging an Airfix girder bridge and have been consulting the Bridges for Modellers book, and whilst it doesn't give a specific instance of what would be used, there are many illustrations, both photographs and drawings, of typical deck arrangements.

Rightly or wrongly, as I'm filling in a pre made gap so I'm slightly restricted in my options, I've gone for full length longitudinal timbers with track built from full size basswood sleepers and C&L chairs sat on it.

I'll try for a couple of pics if you like?

 

Mike.

[Miss Prism]

Old-style, with rails on longitudinal baulks, ballasted  planked infill. My guess is the base was transverse metal or wooden baulks.  (Kerne Bridge)

 

 

 

Not sure whether this one (at Redbrook) was ballasted or not:

 

 

Edited January 22, 2022 by Miss Prism
deleted reference to ballast in the Kerne Bridge pic

['CHARD]

This picture of the well-known bridge at Little Petherick could be of assistance:

 

https://images.app.goo.gl/FAMyi8a8jcCvrCjv7

[cheesysmith]

https://www.google.com/url?sa=t&source=web&rct=j&url=https://assets.publishing.service.gov.uk/media/547c9005ed915d4c0d000185/R022010_100203_Stewarton.pdf&ved=2ahUKEwi-wOSO6L_1AhUBilwKHSqoByEQFnoECAcQAQ&usg=AOvVaw3b5gvQ9oauOk45DfoBD6IJ

 

This will take you to a RAIB report on a bridge collapse due to rust. It includes descriptions and drawings of its construction and modifications.

[RobinofLoxley]

57 minutes ago, cheesysmith said:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://assets.publishing.service.gov.uk/media/547c9005ed915d4c0d000185/R022010_100203_Stewarton.pdf&ved=2ahUKEwi-wOSO6L_1AhUBilwKHSqoByEQFnoECAcQAQ&usg=AOvVaw3b5gvQ9oauOk45DfoBD6IJ

 

This will take you to a RAIB report on a bridge collapse due to rust. It includes descriptions and drawings of its construction and modifications.

Loved the report, looks like something I might have written myself. Wonder if anyone lost their job over it.....

 

 

[RobinofLoxley]

8 hours ago, Lee-H said:

What era are you modelling? Current railway bridges usually have a bed of ballast and conventional track but 100 years or so ago you might have had longitudinal timber rail bearers instead of the usual sleepers.

Lol. I bought one (well specified for a christmas present) because I liked the idea of a girder bridge instead of scratchbuilding a GWR brick one built realistically in the 19th century although the trains crossing it are 1950's -60 versions.

 

But my opinion seems to be confirmed that it would be fine to leave the bridge unballasted but if I wanted to be more realsitic I should run two girders inside the track lines - maybe N gauge rail out of a piece of flexi could do it?

[fulton]

1 hour ago, RobinofLoxley said:

Loved the report, looks like something I might have written myself. Wonder if anyone lost their job over it.....

 

 

Really excellent report, good photos and drawings of its construction, timely for me as I am about to start a bridge in 4mm, over Jane's Creek Strood, have seen similar reports into road bridge failures, where the original design was sound but later modifications lead to corrosion and failure. Picture from Google Street View.

[cheesysmith]

Looking at the report, from a modelling point of view, it tells us that before 1935 (ish, no exact date recorded) it was longitudinal beams with the rails placed on these, probably bullhead rail. After this date it was replayed with a flat deck and ballast, probably with flatbottomed rail (the big four were using flatbottom by this time). Then BR added a waterproof layer above it, but that would not have altered what we as modellers would need or see. The photos also show that at one point the centre girder was actually covered with ballast. 

 

As to the accident, it does say that the bridge was supposed to have been repainted after the water proofing had been done, but never happened. This shows how much the BR was under the financial pressure to cut costs and how it had long term consequences. 

[RobinofLoxley]

4 minutes ago, cheesysmith said:

 

 

As to the accident, it does say that the bridge was supposed to have been repainted after the water proofing had been done, but never happened. This shows how much the BR was under the financial pressure to cut costs and how it had long term consequences. 

Havnt read the report in any detail but you cant tell me that having refurbed the bridge, which is where the expense was, that the painting simply never happened. It was either in the original costed plan or it wasnt, not that it was planned and budgeted for then not carried out. Repainting would have been a fraction of the total budget. And it was Network Rail. The flawed relationship between NR and its subcontractors was fatally exposed by Hatfield. Not sure about the dates as to when the enquiry reported and the rules were changed.

[uax6]

4 minutes ago, RobinofLoxley said:

Havnt read the report in any detail but you cant tell me that having refurbed the bridge, which is where the expense was, that the painting simply never happened. It was either in the original costed plan or it wasnt, not that it was planned and budgeted for then not carried out. Repainting would have been a fraction of the total budget. And it was Network Rail. The flawed relationship between NR and its subcontractors was fatally exposed by Hatfield. Not sure about the dates as to when the enquiry reported and the rules were changed.

 

But the bridge wasn't re-furbished in any way, it just had waterproofing added to the deck. Not unusual for painting not to be carried out either.

It was not Network Rail, this was BR. NR only came about after Hatfield, Potters Bar et al.

 

Andy G 

[cheesysmith]

The forensics carried out afterwards state the last time it had been painted (in the difficult locations where the rust occurred) was in the 1960s. It also states that it was due to be repainted when the water proof layer was added by BR but wasn`t. Network rail knew the bridge was in a poor state, but didn`t know how bad, and the reports stating such recommending remedial work were not acted upon as it was due to be replaced in ten days.

 

As for the cost cutting under BR, you would be very surprised as to what went on. There was a crack in lockwood viaduct near huddersfield. The weedkiller and RHTT had to reverse at this point and return to barnsley because only DMUs were allowed to cross it.

[Lee-H]

16 hours ago, cheesysmith said:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://assets.publishing.service.gov.uk/media/547c9005ed915d4c0d000185/R022010_100203_Stewarton.pdf&ved=2ahUKEwi-wOSO6L_1AhUBilwKHSqoByEQFnoECAcQAQ&usg=AOvVaw3b5gvQ9oauOk45DfoBD6IJ

 

This will take you to a RAIB report on a bridge collapse due to rust. It includes descriptions and drawings of its construction and modifications.

Very interesting report. The fault lies with Network Rail’s engineers as they were repeatedly warned of the poor condition of the bridge but failed to act in a timely manner.

[Bomag]

Using waybeams to support track saves mass and ensured the deck is visible for inspections. The problem is that it is structurally stiff and the whole deck is subject to live load strain leading to increased fatigue. Having a bed of ballast reduces fatigue loading on the bridge deck but is heavier and makes inspection for deck condition much more difficult (like post tensioning). Modern steel decks can support the dead weight of ballast and are more durable by reducing live fatigue loads.   Given had bad decks have got with waybeams (my colleague managed to put his foot through the deck of the Tay bridge in the 90's) god knows what state some of the ballasted bridges from the 1960s/70s have got to.

[wasdavetheroad]

I have a copy of Harold Bowtell's book 'Rails Through Lakeland' and there is a chapter on bridges. There are a number of upper and lower Bowstring girder bridges on the line including some with the track curved. They have heavy longitudinal timber baulks beneath the rails, canted in the curved versions with longitudinal heavy planks between. No evidence of ballasting. It is mentioned that the lack of ballast puts more strain on the bridges structure.

[Grovenor]

On 20/01/2022 at 07:19, Miss Prism said:

Old-style, with rails on longitudinal baulks, ballasted. My guess is the base was transverse wooden planks or there was a ballast tray.  (Kerne Bridge)

 

 

 

Not sure whether this one (at Redbrook) was ballasted or not:

 

 

Neither of those would be ballasted, in both cases the baulks would be supported on the cross girders as in the second pic. Then just plank infill for track workers to walk on. Ballast adds a lot of weight needing bigger girders, ballasting over steel bridges is more modern and done to allow higher speeds by eliminating discontinuities in the track.

[Miss Prism]

Thanks Keith, You're right. I misread the Kerne Bridge picture. (I've done a quickie edit to the posting.)

 

Edited January 22, 2022 by Miss Prism