1. What are expansion joints, and why are they used?
http://en.wikipedia.org/wiki/Expansion_joint
Expansion joints, also known as movement joints, are designed to accommodate the movement of different building materials caused by temperature, moisture, seismic activity, or other factors. They are used to allow for the expansion and contraction of construction materials due to temperature changes, avoiding potential damage or failure.
Expansion joints are particularly important in large structures, such as buildings, bridges, and highways, where the materials used (like concrete, steel, or asphalt) may expand or contract with changes in temperature. These joints provide flexibility, allowing the materials to expand or contract without imposing excessive stress on the structure.
The key purpose of expansion joints is to prevent cracks, fractures, or displacement of the materials used in construction. Without expansion joints, the materials would exert pressure on each other, leading to tensile stresses, which can cause permanent damage, compromise the structural integrity, or shorten the lifespan of the structure. Expansion joints act as a buffer, absorbing the movement and minimizing the potential for damage.
By allowing controlled movement, expansion joints help ensure the longevity, safety, and functionality of structures, while also improving their overall appearance by minimizing the occurrence of unsightly cracks.