Thermal expansion significantly impacts both bridges and railways because materials like steel and concrete expand and contract with temperature changes. Here’s how it affects each:
Bridges:
- Expansion and Contraction: As temperatures rise, the materials in a bridge expand; when temperatures drop, they contract.
- Stress and Damage: Without proper accommodation, this expansion/contraction can cause stress, leading to cracks, warping, or structural damage.
- Expansion Joints: To handle this, bridges are designed with expansion joints—gaps or flexible components—that allow sections of the bridge to expand and contract without causing damage.
- Support Bearings: Bearings under bridge spans also allow controlled movement.
Railways:
- Track Buckling: Rails expand in hot weather and can buckle if they don’t have room to expand, causing dangerous derailments.
- Expansion Gaps: Traditionally, small gaps were left between rail segments to allow expansion, but gaps can be noisy and bumpy.
- Continuous Welded Rail (CWR): Modern railways often use CWR with rails welded together continuously. The rails are pre-stressed and anchored firmly, which reduces gaps and bumps but requires careful temperature management.
- Temperature Monitoring: Railways monitor temperature and may impose speed restrictions or take other safety measures during extreme heat.