As a result of the technique’s success, a new project has been undertaken recently to demonstrate that this well-known aerospace technology can also be applied to steel rail bridges. It aims to increase the carrying capacity of the bridges, allowing trains to cross them with greater speeds. It also aims to increase the fatigue life of the bridge.
The original technique involved bonding a carbon composite patch onto the damaged area. This resulted in the stress levels being reduced significantly, thus allowing the life span of the structure to expand, providing complete safety.
The repair technique involves bonding a carbon composite reinforcing plate (CCRP) to the bottom flange of steel girders on the bridge. An important part of the repair process involves determining the optimum size of the CCRP for the girder that needs to be reinforced.
High strength, fast curing adhesive is used to allow the repair to be completed without the need to close the bridge and halt rail traffic.
Laboratory trials were conducted to prove the concept. This involved a CCRP being bonded to an instrumented steel girder, which was then subjected to representative loads in a test rig.
The laboratory tests show that in regards to the selected test girder and the size of the CRRP used, a 25% reduction in the stress of the steel girder was possible.
A CRRP was then bonded to a girder of an operational bridge. During the trial, a similar reduction in stress was demonstrated. The CCRP was bonded to the bridge in April 2006 and it is still in place now, without any signs of deterioration.
The theoretical analysis, laboratory tests and in-field trials have all demonstrated that it is possible to achieve a 25% reduction in the stress levels of steel bridges.
The repair technique can be used on any steel bridge, or it can be adapted to any wooden and concrete bridge that carries rail or road transport.
