Thermal Expansion Coefficients

sprinkles

I am currently working on the design of a steel structure in Columbia and while most of the steelwork is enclosed there are a few beam that are exposed. They are quite long - 144m on average and which means I'm looking at quite large expansion joints at the end. Using a change in temp value of 37deg I have come up with a movement of approx 62mm - which is less than the 90mm required for seismic so it's not governing.... yet.

I remember reading somewhere that there is a direct sunlight effect as the steel will heat up far more when exposed to direct sunlight than the change in ambient temp. I can't find a figure for this on the net anywhere, there are various answers I have seen figures ranging from 2.5 times the final value (gives me 158mm) to adding 30 deg onto the ambient temp (gives me 115mm). Does anyone have any knowledge of this?

Dan

jomo99

Have you contacted the ESB. They would have knowledge, due to haveing very long lines hanging in sunlight for many years.

John

merengueca

Taking a length of rail as an example all rail is stressed to 27deg regardless of site conditions, with the obvious exception of tunnels (greater than 42m).

Rail in a North - South cutting will only receive limited exposure to direct sunlight, unlike track lying on East - West embankment. The main focus is actually on ensuring the lateral stability of the track structure to resist buckling.

Maybe review thermal stressing practice for rail in countries with a less forgiving climate, the Permanent Way Institute may be able to assist.

(NB I actually have a video clip of track buckling from a test site carried out by BR research, one hell of an eye opener)