Client
Transport for London
Value
£1.4M
Sectors & Services
Rail Structural Strengthening ECI (Early Contractor Involvement) Projects
Streatham Station Bridge carries the A23 trunk road over twin railway tracks adjacent to Streatham Station in south London. Originally constructed in 1850, the bridge comprises a two-span masonry jack-arch deck supported on cast iron beams, later partially strengthened in the early 1900s with steel beams encased in concrete.
With increasing traffic demands, Transport for London required the two-lane carriageway to be extended to accommodate dedicated bus lanes. This necessitated strengthening ten original cast iron beams without altering the historic structure, reducing headroom, or excavating the footways above, presenting a technically complex and sensitive structural repairs UK challenge.
Services undertaken
-
Structural strengthening of cast iron beams using UHM CFRP plates
-
Vacuum blasting to prepare beam soffits
-
Application of primer coatings to cast iron surfaces
-
Bonding of CFRP laminates using structural adhesive
-
Design and installation of temporary clamping system
-
Environmental monitoring during installation
-
On-site preparation of adhesive and shear lap test samples
-
Quality assurance testing, including tap testing of bonded plates
-
Works undertaken during engineering hours with full rail closures
CRL was appointed to work collaboratively with Tony Gee & Partners to develop and deliver an innovative strengthening solution using ultra high modulus carbon fibre reinforced polymer technology. Drawing on its pioneering experience, including the first-ever bridge strengthened with UHM CFRP plates in 1999, CRL designed a scheme that preserved the existing bridge fabric while achieving the required capacity increase. The final design involved bonding Sika-DML UHM CFRP laminates to the soffits of ten cast iron beams, providing significant structural enhancement with minimal physical intervention.
Due to the sensitivity of strengthening cast iron, strict environmental controls were essential. CRL installed the system over two consecutive summer periods to ensure suitable temperature and humidity conditions. Works were carried out during engineering hours under full rail closures, requiring careful coordination to maintain operational continuity and safety. Beam soffits were prepared using vacuum blasting to achieve an appropriate surface profile, followed by the application of a Sika primer to promote bond performance.
The CFRP laminates were bonded using Sikadur 31 adhesive, applied to both the prepared beam surfaces and plates. To ensure correct alignment and full adhesion during curing, CRL designed and installed a bespoke temporary clamping system, which was removed one week after installation. Quality control formed a critical part of the process, with on-site preparation of adhesive test samples and shear lap specimens for independent testing by Oxford Brookes University. Environmental conditions, including humidity and steel surface temperatures, were continuously monitored and recorded, and completed installations were tap tested to confirm bond integrity and the absence of voids.
“An innovative and expertly delivered solution. CRL strengthened the bridge efficiently and safely allowing an icrease in loading.”
Kevin Jones | Project Engineer | CRL
The use of UHM CFRP plates delivered benefits well beyond immediate strengthening, providing a durable, low-maintenance solution that extended the bridge’s service life without intrusive structural alteration. By eliminating the need for excavation or significant reconstruction, the scheme preserved headroom, protected the historic asset, and reduced disruption to road and rail users.
CRL’s rigorous quality control, environmental monitoring and collaborative approach with Transport for London and the designer ensured a resilient outcome aligned with long-term asset management objectives.
This project clearly demonstrates CRL’s expertise in advanced concrete repairs and structural strengthening, delivering innovative, efficient and sustainable solutions to complex infrastructure challenges.
