What type of bearings are included in the category of 'Movable Bearings'?

Answer: B — Rocker and roller bearings

Movable bearings are designed to accommodate movements caused by thermal expansion, contraction, and other dynamic factors affecting bridge structures. Rocker and roller bearings are specifically categorized as movable because they allow for rotation and translation, enabling the bridge to respond effectively to these movements. Rocker bearings consist of a curved surface that pivots, while roller bearings use cylindrical rollers to facilitate movement. Both types ensure that forces and stresses from the superstructure can be effectively distributed while allowing necessary movements, helping to maintain structural integrity and performance over time. In contrast, other options list types of bearings or components that do not fit the definition of movable bearings, such as fixed and sliding bearings, which are meant to restrict movement to a certain extent, and concrete foundations, which are essential for stability but do not serve the same function in enabling movement.