Working for both road and rail bridge owners pitt&sherry is particularly active in extending the useful lives of structures through load rating assessment, strengthening, rehabilitation and load testing.

pitt&sherry has been particularly active undertaking load rating assessments, strengthening and rehabilitation design and load testing of existing bridges for both road and rail bridge owners.

Load rating
A critical component of managing the bridge asset is to understand the load capacity of the bridge stock. With the aging profile of bridges, many have been designed to carry lighter design loads. However, with improved analytical techniques and through implementation of risk management techniques many bridges can be deemed to be suitable to carry current design loads.

In order to determine the load capacity of a bridge, pitt&sherry usually undertake:

• An as-new load assessment of the structure
• A detailed inspection to identify any loss in structural capacity in the as-is condition
• An as-is load assessment.

Bridge strengthening
Strengthening solutions are developed to address deficiencies identified from the load rating assessment to suit each structure and site constraints.

pitt&sherry has developed a broad range of bridge strengthening methods including:

• External post-tensioning of pier crossheads
• Widening of blade piers
• Bonding of steel plates to pier crossheads and beams
• Infill walls between columns
• Widening of pier crossheads
• Strengthening of steel girder halving joints
• Carbon fibre to strengthen bridge decks and beams
• Provision of new shear connectors
• Strengthening of halving joints

Bridge rehabilitation

In order to extend the life of a structure, it is often necessary to specify extensive rehabilitation works including:

• Bridge painting
• Lead paint removal
• Cathodic protection
• Concrete repairs

Load testing

Often the load rating assessment process shows the capacity of a bridge to be marginal and the cost of strengthening is high. In these cases, it is often considered appropriate to install instrumentation and load test the structures to determine actual strains and deflections under live load and relate the findings to those predicted by analysis.