Details of Bridge expansion joints

CLIMA bridge expansion joints  are structural components designed to provide smooth passage  over the gap  between adjacent sides of a deck joint, while also permitting relative translation and/or rotation of the two sides of a bridge deck (deck movement joint).

A deck movement joint is generally defined as a structural discontinuity between two elements, at least one of which is a deck element, and is designed to allow relative translations and rotations due to: thermal expansion and contraction of the superstructure, concrete shrinkage or creep, elastic shortening due to pre-stressing, displacement of the structure under load, or any other action the desk is subjected to.

Because expansion joints are installed at a late stage in construction, some of these movements will have at least partly already taken place. Consequently, expansion joints have to facilitate a smaller degree of overall movement than a bearing at the same location.
Agom deck joints are constructed and designed to prevent damage to the deck, bearings, piers, and abutment by water borne chemicals and other foreign materials, either by preventing water leakage  through the joint or by allowing water to drain through the joint in such a way that avoids damaging the deck, bearings, piers, and abutment.