> Its laid it's in tension by hydraulically stretching it before cutting to length and welding to the previous length. Sufficient tension is applied to achieve a 'Stress Free Temperature' (SFT) of 27 degrees C (i.e to relieve the tension by expansion the rail would need to be heated by the sun to 27C, whereupon it would neither be in tension or compression).
Apparently they lay it "hot" and so normally when it is cooler than that it is actually "pulling" on itself trying to shrink, and when it gets hotter than that it begins to compress.
If it can't compress it buckles, if it can't shrink then the tension grows, but steel has incredible tensile strength.
> Its laid it's in tension by hydraulically stretching it before cutting to length and welding to the previous length. Sufficient tension is applied to achieve a 'Stress Free Temperature' (SFT) of 27 degrees C (i.e to relieve the tension by expansion the rail would need to be heated by the sun to 27C, whereupon it would neither be in tension or compression).
Apparently they lay it "hot" and so normally when it is cooler than that it is actually "pulling" on itself trying to shrink, and when it gets hotter than that it begins to compress.
If it can't compress it buckles, if it can't shrink then the tension grows, but steel has incredible tensile strength.