Clownes Bridge Strengthening Works

Clownes Bridge is a single span masonary arch structure which carries the A614 Bawtry Road over Woodhouse sewer drain. The original structure consists of a single span segmental arch founded on spread foundations, with a skew of 20° from the perpendicular, which was built circa 1952. The arch barrel is constructed from red brickwork and has a square span of 3.66m.During 1967 the structure was extended at both ends with bolted segmental corrugated steel Armco side extensions.

C R Reynolds were engaged at an early stage to discuss methods of executing the works and offered value engineering to the client. Due to the volume of traffic that uses the A614 on a daily basis along with the number of underground and overhead services the option of installing traditional pre-cast concrete box culvert units wasn’t commercially viable and carried an enhanced risk due to the location and required diversion.

As a result of the above, the outline of the scheme included constructing a reinforced concrete invert slab and training walls, fixing a lightweight self-supporting welded wire fabric mesh to the structures soffit and spray applied concrete. The scheme was awarded as a contractor design and build, during the pre-start stages and throughout the construction stage the site team worked closley with the design team and client to ensure the most workable methods were encorporated and also that the specification could be adhered to to produce a high-quality finished product.

In order for the works to be carried out safely Woodhouse sewer drain required diverting to enable a dry working environment. The watercourse was diverted for the duration of works by installing a robust dam up and down stream along with permanent PCIP flume pipes beneath the structure which were then sealed in position by mass filling the excavation with concrete.

The flume pipes ran beneath each dam to enable the watercourse to flow through the works area. Casting concrete above the pipes created a working area more suitable than stone as it could be easily cleaned and kept dry for fixing the invert slab and wall reinforcement.

Following the watercourse diversion and enabling works, the main construction works included constructing the invert slab and walls which created a solid working platform for the soffit reinforcement to be fixed and the walls created a base to enable the sprayed concrete to be applied from. Minor works were carried out on the A614 carrigeway which inclued the removal of existing timber guardrail and replacement with N2 containment with P4 terminals.

A further element of the scheme was to protect the concrete invert from potential scour and increase the lifespan by placing both up and downstream a clean stone within the watercourse which would take the initial impact of fast flowing water. The permanent flume pipes were capped off on completion and are recognised as a futureproof element for the client where inpsections are required the caps can be removed and watercourse easily diverted.

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Clownes Bridge Strengthening Works

Client: Doncaster MBC
Location: Clownes Bridge, A614, Doncaster
Contract Value: £200,000
Contract Period: 8 weeks