EXPANSION OF JOINTS
Bridges and sidewalks:
• Bridges and sidewalks are built in sections.
• There are spaces between the sections called expansion joints.
• Expansion joints allow steel and concrete to expand without cracking.
• The expansion joints narrow when bridge segments expand in hot weather.
• Expansion joints in a bridge separate when the side-by-side segments of a bridge contract in cold weather.
• Railway tracks consist of two parallel metal rails joined together.
• Small gaps, called expansion gaps, are deliberately left between the rails as there is an expansion of the rails in hot weather.
• If we hold a very hot glass tumbler under cold water, it cracks.
• This is because the outer surface of the glass comes in direct contact with cold water and contracts more as compared to the inner surface.