How do we compensate for thermal expansion /contraction in the construction of steel bridges?
Have you ever noticed gaps between sections of steel bridge roadways? They are called expansion joints. See
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for some examples.
To compensate for thermal expansion and contraction in the construction of steel bridges, several techniques are commonly used. The key idea is to allow for the bridge structure to expand and contract freely without causing damage or deformation. Here are the main techniques employed:
1. Expansion Joints: Expansion joints are designed to accommodate the movement of the bridge due to thermal fluctuations. These joints are typically placed at specific locations along the bridge and allow for movement without transmitting excessive stresses to the bridge components. They can be of different types, such as sliding plate joints, roller bearings, or elastomeric pads.
2. Bridge Bearings: Bridge bearings provide support and allow controlled movement between various bridge components. They usually consist of steel plates or neoprene pads placed between bridge elements to absorb or accommodate thermal movements.
3. Longitudinal Movement Allowance: Bridges also have sections that allow longitudinal expansion and contraction. This is achieved by leaving gaps between adjacent segments or using specialized connections that allow controlled movement. These gaps are filled with flexible materials to accommodate the thermal changes efficiently.
4. Thermal Insulation: In some cases, thermal insulation materials such as foams or blankets are used on steel bridge components. Thermal insulation helps reduce the temperature fluctuations experienced by the steel, minimizing thermal expansion and contraction.
It is important to note that the design of steel bridges takes into account factors like the expected temperature range, material properties, and the coefficient of thermal expansion. Special considerations must be made during the design and construction process to ensure that the bridge can safely accommodate thermal fluctuations over its lifespan.