Thought that this might be interesting to some of the members here.

Here's how we are 'restoring' bridges down in Australia now.
If it's within 2 foot of the ground it's concrete, so no rot or termites.
Above that it's steel, with a used rail deck.

There is still timber curbing fitting on the outside of the deck (not shown below) which helps with the asthetics, but at 20-30% of the cost for a replacement bridge built of timber, this is the future for us anyway. They have been certified for 24ton axle loads which is great as our track is only good for 18ton.....

Then there is also the time aspect. The concrete work for a typical 7 or 8 span bridge (11 to 15 ft spans) takes around 1 to 2 months depending on volunteer availability. We dig down to where the original driven timber piles are still solid, cap them with a 3' by 3' concrete 'pile' to just below ground level. Then a 2' thick pad is poured on the top of the piles, which is what the steel work bolts to.

Errecting the steel work takes a day. The steel is cut/welded/predrilled by an offsite contractor and delivered as a kit. Adding the rail deck is around 5 days work.

If you were setup and ready to go, you could get from ground breaking to laying track in under 2 months if you really pushed it. At the Yarra Valley Railway in Victoria, we have 20 bridges on the line. 4 already restored in timber. 2 are concrete and steel already (older design built by the government railway), 1 is going to become a culvert and the remaining 13 have to be completed in the next 2 years! (deadline on the federal government grant we got.)
1 bridge has been completed and concrete work for 9 others is done, all in 15 months.

IMG_2332 by thunda666, on Flickr

Thanks for posting, I did find this interesting and it looks like some quality work is being done, but it's hard to call a "rebuild" a "restoration."

Bob H

I followed what you are doing until you go to the deck. How is it constructed?

The deck is made up from lengths of used 94lb rail.
They are cut to span either 3, 4 or 5 piers, and then drilled so that there is a bolt between each rail and the crosshead it is sitting on. That has been changed for the other bridges as we realised bolting every contact point was a bit over the top. So each rail will now only be secured at each outer end with bolts, and only the outer most rails will be bolted at every crosshead.
When we lay and then ballast the track, we use smaller ballast than normal, around 1", which allows it to fall between the heads of the rails making up the deck. Once tamped and a bit of traffic has gone over, this means all of the gaps between the rails are packed with ballast forming a very solid assembly that transfers the load very effectively.

If the existing pilings were unusable, could it be built without any wood for pilings, and instead use concrete piers down to a tested density and accomplish the same?

I'm thinking about how the same type bridge would be built on new ground, that had no old pilings and had not been built upon prior.

It would really depend on the ground conditions, we are dealing with very deep river silt/clays on a floodplain.
Some of the original piles that we are capping with concrete now, were orignially driven 120ft into the clay without 'hitting bottom'. They just kept banging them in until the 'that'll do' point was reached.
You could probably drive/drill new concrete into the ground to achieve the same effect if building a new bridge without any old foundations. We just have the benefit of 125 year old timbers in as new condition just 6-10ft under the surface.

http://s1184.photobucket.com/user/trest ... t=9&page=1

Above are some further pics taken by another volunteer showing some of the process from demolishing the old bridge to beginning to lay the new deck.