The technique of bonding external reinforcement to structures was first used in the UK in 1975 on the M5 near Birmingham to strengthen the Quinton Interchange.
The method of strengthening using externally bonded reinforcement, structural strengthening, can be introduced by providing the answers to some simple questions.
- What is Structural Strengthening?
- Why do we need in?
- What can be achieved by using the technique?
- Where can we use it?
Structural strengthening involves the bonding of additional reinforcement to the external faces of a structural member. This additional reinforcement can incorporate steel plates, composite plates or composite wrapping systems. The method is attractive because it provides a cost effective solution to increasing load carrying capacity, especially when compared to demolition and rebuilding.
One of the main reasons for the use of the method in the UK is due to the change of use of a structure giving an increased load-carrying requirement. Other reasons such as, inadequate design, poor quality construction, structural damage, fire damage, seismic loading, reinforcement corrosion (If the cause is treated) and loss of prestress force are not uncommon.
Strengthening can improve the load carrying capacity of structures by;
- Increasing flexural strength,
- Shear strength,
- impact resistance,
- punching shear resistance,
- redistribute loads around new openings.
Externally bonded reinforcement gives the opportunity to strengthen without having a significant visual impact on the structure. The installation process is fast and can minimise disruption to the function of the structure including the services attached to it.
Structures made from reinforced concrete, steel, cast iron, masonry and timber have all been strengthened to date using a form of the technique. Beams and slabs have been strengthened on both the top and bottom surface for flexural strength. Columns and beams have been strengthened on there side faces for shear. Slabs have been strengthened around columns to increase punching shear resistance. Various other types of structural elements have been strengthened for many different reasons.