Most modern railroad use continuous welded rail, so there are no joints like what you're talking about. This is both stronger and quieter, but it can lead to problems when the temperature is too high or too load, because of thermal expansion.
"There are a number of ways to increase the resistance of rail to buckling. The first and most common is the use of rail anchors to limit the longitudinal expansion of the rail. Anchors come in a variety of designs, but they all apply several thousand pounds of clamping force on the base of the rail. When applied properly against each side of the crossties, the anchors prevent expansion of the rail in the longitudinal direction." - http://www.interfacejournal.com/features/03-05/track_bucklin...
"There are a number of ways to increase the resistance of rail to buckling. The first and most common is the use of rail anchors to limit the longitudinal expansion of the rail. Anchors come in a variety of designs, but they all apply several thousand pounds of clamping force on the base of the rail. When applied properly against each side of the crossties, the anchors prevent expansion of the rail in the longitudinal direction." - http://www.interfacejournal.com/features/03-05/track_bucklin...
For more, and pictures, see http://en.wikipedia.org/wiki/Rail_stressing .
The UK had problems this summer because of buckling: http://www.dailyecho.co.uk/news/10549015.Rail_delays_as_trac... .