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# Thermal expansion of bridges

### Thermal expansion of bridges

The length of the metal frameworks of bridges change when the temperature changes.

Physics

Keywords

thermal expansion, linear thermal expansion, thermal motion, expansion, shrinkage, heating, bridge, bridge deck, temperature, metal framework, thermodynamics, tied-arch bridge, physics

Related items

### Tied-arch bridge

• bridge deck
• arch
• pier
• abutment
• expansion joint
• roller bearing

### Bridge expansion joint

• expansion gap
• expansion joint

• roller
• sole plate
• pintle pin

### Principle of thermal expansion

• atom - Balls symbolise these. When the temperature increases, the thermal motion of atoms increases, they maintain a greater average separation. This results in an increase in volume.

When the temperature increases, solid bodies expand, while they contract when the temperature decreases. Thermal expansion is the result of a change in the motion of particles. As the temperature increases, the atoms oscillate with greater amplitude and the average distance between them increases.

The thermal expansion of solid bodies is greater when their original volume is greater, and when the change in temperature is greater. Thermal expansion also depends on the physical properties of materials.

### Narration

Due to thermal expansion, the length of bridge support structures changes with changes in temperature. This must be taken into account when a bridge is being designed. The problem can be solved by placing roller bearings on one of the piers, thus permitting the horizontal movement of the superstructure. The expansion joint built into the bridge deck allows for continuous traffic over the bridge even in extreme thermal conditions in summer or winter.

In summer the bridge deck expands due to high temperature, while in winter it contracts. The change in length is directly proportional to the length of the bridge and the change in temperature, usually it is only a few centimetres. Without a roller bearing even these few centimetres would cause huge mechanical tension in the deck, which would result in serious damage to the metal structure of the bridge.

### Related items

#### Chain Bridge (Budapest)

The Széchényi Chain Bridge, named after István Széchenyi, was the first permanent bridge across the Danube between Pest and Buda.

#### Golden Gate Bridge (San Francisco, 1937)

The suspension bridge that stretches above the strait between San Francisco Bay and the Pacific Ocean was opened in 1937.

#### Body-centred cubic lattice

The least tightly packed crystal structure.

#### Face-centred cubic metal lattice

The face-centred cubic metal lattice allows the closest fit of metal atoms.

#### Hexagonal metallic lattice

Metals forming hexagonal metallic lattices are rigid and difficult to machine.

#### Metals

Metal atoms form a regular lattice structure.

#### Thermometers

There are various types of instruments used for measuring temperature.

#### Types of bridges

Types of bridges include beam-, arch-, suspension-, cantilever and truss bridges.

#### Medieval inhabited bridge (London Bridge, 16th century)

In the Tudor Era around 200 buildings were built on the bridge across the River Thames.

#### p-V-T diagram for ideal gases

The relationship between the pressure, volume and temperature of ideal gases is described by the gas laws.