Bridges today are no longer built solely to fulfill a function, they also have artistic aspirations. The stresses to which road or rail bridges are exposed are many and various. Besides temperature variations, one of the major impacts to be considered is traffic load, which has increased in recent years and will continue to grow in future.

Bridges are subjected to a variety of deformation phenomena resulting from many different actions, especially movements. Bridge movements are largely absorbed by efficient bearing systems, while the variable gaps between supported structures are compensated for by expansion joints - which are usually under traffic load.