What is an expansion joint?
As a moving ‘living’ structure, a bridge is continuously affected by vehicle load, wind conditions and temperature, which in turn contribute to its life span. Expansion joints are a vital component of any reinforced concrete, pre-stressed concrete and steel structures, and bridge decks in particular, as they absorb these movements, while also accommodating shrinkage, creep effects and changes in temperature experienced by the structure. An expansion joint is the element under the most strain in any engineering structure.
Movement on bridges caused by wind, live load or thermal expansion is a significant issue for bridge designers. When designing a bridge, an engineer will take these external forces and effects into account, ensuring the structure has both bridge bearings to allow movement and defined restraint at its support, and also expansion joints (or movement joints) strategically placed to allow traffic to pass over movement gaps.
Specification and selection of expansion joints
When designing a new structure or looking to repair an existing bridge, an engineer will take into account how it will react to the external factors and calculate a specification, taking whole life and service life into consideration.
Freyssinet offers a wide range of expansion joints which incorporate all manner of requirements – from traffic frequency and movement range to driver comfort and resistance to aggressive elements (gravel, salt, sand, etc). Selecting the correct type of joint is fundamental, and therefore Freyssinet provides a thorough inspection and design service to establish which joint not only matches the requirements of the structure, but also the client.
When selecting expansion joints, it is important to consider the material, the type of fixity of the joint and the type structure it is to be fitted to, to easy allow maintenance and replacement when necessary.
Traffic frequency is also an important factor, both in terms of average daily use and during installation. Freyssinet makes every effort to minimise inconvenience to road users, and therefore will install temporary trafficking plates, which allow traffic flow during day time hours and work can be completed during night time closures.
Allowances for vertical differential movements must be made, especially when considering rubber mat expansion joints. Differences in levels across the joint can lead to reductions in lifespan where the rubber is deflected by traffic passing over it, creating a ‘pounding’ effect on the supporting grout below.
Selecting the most suitable joint, based calculations of movement, external forces and the operating needs to the structure can increase its life span.
An integrated approach
Freyssinet has been installing expansion joints to structures all over the world for more than 40 years. As a bridge expansion joint specialist, Freyssinet is able to offer an inspection and design service to establish the correct type of joint for a structure, provide efficient removal of old joints and expert installation operations.
As part of our integrated approach, Freyssinet can provide:
- Full and detailed assessment of a structure
- Bespoke design of the most performance-efficient and cost-effective joint
- Propose the best sequence of joint installation and replacement to minimise project schedules and disruption to traffic.
- Associated services, such as concrete repair, traffic management, hydrodemolition, waterproofing and resurfacing.
For further details, or to discuss your requirements, call 01952 201901 or email email@example.com