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.

There is alternate technology for rails exposed to hot weather.

The advent of continuous rail lengths in Australia led to rail deformation due to thermal expansion.

The solution was to introduce tension into the rails before welding together in place. There is a table where knowing the max and min environmental temperatures and the ambient at time of (thermite) welding determines the tension applied to the rails to be joined.

I'm certain that your professional engineers can find the necessary calcs for this situation and determine the optimum settings.

The alternate (fallback) would be to move away from continuous length rail and introduce some joints to accommodate expansion.

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.

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

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"