How Do I Cool Down a Concrete River Bridge?

Possibly a reflective coating might work...we use coolseal on our roofs down south here...

https://www.coolseal.com/

I have no better answer for existing bridges beyond coatings, and I'm definitely NOT an expert on the following, but...

The CTE (Coefficient of Thermal Expansion) of concrete varies considerably. I understand that one of the most significant variables is the kind and size of aggregates used in the concrete. Some research/experimentation before building a new bridge could result in reduced differential between the CTE of the concrete and the CTE of the steel.

In a similar fashion, different alloys of steel have different CTEs. I doubt if it would be economical to choose an alloy of steel according to its CTE, but if it made the bridge last longer, it just might be worth it.

We have a good understanding of CWR (continuously welded rail) on normal foundation, with min/max temperature ranges when welding, stress measurement and subsequent de-stressing. The issue here is the bridge design that is not optimal, and adds to the rail stress as the deck expands & contracts. We've got a university looking at it, curious to see what they'll come up with!

One of my colleagues had a concern with painting the concrete, as it may hide developing defects. Again, we'll need to do some tests. If there is anything interesting from this research, I'll keep the forum posted.

Re: "One of my colleagues had a concern with painting the concrete, as it may hide developing defects."

A concrete sealer, being a product that sinks into the concrete rather than sitting on top of it, would be unlikely to hide cracks (whereas a flexible paint could do). Concrete sealers are available in a range of colours including white.

Cutting the rail joints on an angle, as illustrated by SE will allow the sections to slide past each other to accommodate movement.

Regarding the total bridge structure expansion, sliding pads at contact points on supports would do it, with studs in slots in the mounting plates the to limit the travel.

The end supports are most important as they carry the the main load of the bridge.

They would have to be carefully engineered to respond to the temperature, but it can be done.

Look around at other bridges in the area for ideas..no sense reinventing the wheel.

Run some of the river water through the bridge

Regardless of the bridge length, leaky water pipes serving like drip lines may help address the concrete temperature gradient problem along the bridge length by running a water pump during or when the sensed ambient temperature goes up a preset level...

I've got three possibilities:

One: Use four tapered ends so they can freely slide past each other with the inner probably held solid as the inner width is critical to stability. Like your reversed palms sliding past each other.

Two: Similar to above but one tapered end on top and the other underneath sliding under the top tapered rail like a tectonic plate performing subduction.

Third: If you know the coefficients of expansion for the different parts, insert a length of rail with a on or near the bridge with a different coefficient of expansion to compliment the bridge expansion and hopefully equalize out the problem.

Interested to hear how this works out. Always wanting to learn.

well that is exactly what I was thinking so easy peasy.

Thanks SE.I noticed they have clips instead of nails now(been along time since I hoboed).I also noticed they have a reinforced backing plate behind the solid track to limit the movement. And concrete "Cross ties" instead of creosote beams. That's progress, I guess.

I remember walking with these two hobos down a RR track, and they were quite plastered. One of them said "This is the longest set of stairs I have even seen"

The other one replied "It ain't the stairs that's killin' me, it's this low handrail"

Running water in pipes in sealed loops from very large tanks could begin to reduce the difference from night and peak day temperatures to even out the temperatures over 24 hours. Water has a huge thermal capacity. Could be powered by solar panels also providing a little shade and if power supply is a problem by gravity by pumping to a raised second tank during the day for release at night.

My thought would be to introduce some material which would let the railway tie slide on the surface of the bridge, maybe Teflon, Polypropylene or Nylon sheets attached to the railway ties. As the bridge expands and contracts, this would allow the railroad tie to slide to accommodate the difference in thermal expansion.

As for wear well they line the trays of rear dump trucks with a polymer for make the payload slide out easier without hang ups maybe a similar idea for the 2 contact surfaces.

Not all the replies to the question posed are applicable. The question raised the issue of cooling concrete bridges, not the rails, so all the answers referring to the rails themselves are irrelevant here.
The problem with allowing water into the concrete defeats the object as water that will seep into the concrete and eventually cause rust or ice to develop in the concrete causing cracks to occur and eventually possible replacement of the bridge.
My solution would be to form a "second skin" over the surface, similar to shields used on gas tanker trailers or stationary propane tanks exposed to the sun.

This shield can be highly reflective material or painted white or silver and allow the air to circulate so little to no condensation occurs on the underside. It could also be mounted between the rails so that the amount of concrete actually exposed to the sun would be extremely limited so virtually eliminating the problem. Or one could be clever and use PV to produce electricty at the same time.

Here is an image of a bridge with sliding plates on support columns which will allow lateral movement.

After reading that, I suspect it would be cheapest and simplest to have gaps in the rails on the bridge, and go back to continuous rail on each side.