Department of Architecture and Civil Engineering

Prolonging the life of our concrete infrastructure

Our researchers developed assessment and strengthening methods to increase the life of our bridges and structures, saving millions for the economy and industry in maintenance.

concrete-overpass

Challenge

The Highways Agency (the UK’s largest bridge owning authority) and Network Rail are responsible for maintaining almost 12,000 concrete bridges, some constructed as far back as the 1920s and to out-of-date standards.

The research carried out on assessment has resulted in significant economic and operational benefits related to the management of concrete bridges. In addition, through effective dissemination of the research, the benefits have been realised to a greater extent across the industry.

— Regional Associate,
Parsons Brinckerhoff

REF submission

This research was part of our REF 2014 submission for Architecture, Built Environment and Planning.

Maintaining these bridges costs millions of pounds a year, with the highest economic cost being the necessary lane closures associated with any maintenance carried out. The Highways Agency calculated this cost as somewhere between £10,000 and £50,000 per lane, per day.

Finding a way to increase the life of these ageing structures would have significant economic benefit for the UK and industry.

Solution

Assessment

In collaboration with leading engineering consultant, HA and Parsons Brinckerhoff, Professor Tim Ibell, Dr Antony Darby and colleagues from the Department of Architecture & Civil Engineering investigated the shear capacity of bridges with insufficiently anchored reinforcement.

Under existing guidelines for structural assessment, many bridges built before 1972 would have been condemned  because they were deemed as being designed to insufficient standards. The team developed a simplified and realistic assessment procedure that adopted a plasticity approach, showing that, in many situations, the capacity of these poorly detailed structures was, in fact, sufficient.

They also established a shear assessment methodology for bridges constructed using pre-stressed beams, laterally post-tensioned together, which are widely used by the UK rail network. Research identified that the effect of lateral pre-stress increased capacity by over forty per cent, something that had been ignored in existing assessment methods.

Strengthening

A strengthening method was developed for when these bridges were found to have inadequate capacity. The method, termed deep embedment strengthening, involved Fibre Reinforced Polymer (FRP) rods glued into holes drilled through the beams to act as additional shear reinforcement. The technique is more efficient and ductile than alternative methods and can be applied to slabs as well as beams.

 

Benefits and outcomes

The findings from the project have led to the researchers being commissioned to write various design and maintenance guidance documents that are routinely used by infrastructure owners and consulting engineers worldwide.

The research has allowed the life of concrete structures to be extended through developing proper methods for assessing existing capacity as well as the means to increase capacity where necessary. This has prevented buildings and bridges from being condemned as unfit for purpose, ensuring that our ageing structures remain in service for the present and future.

The direct impact is vast savings in reconstruction costs for the UK economy and the prevention of disruption to infrastructure users.