Market Street Flyover, Mexborough

 

Market Street Flyover, Mexborough


Grid Ref  SK 474 997


Constructed 1967/8

market STREET OVER  greens way (MEXBOROUGH Relief road) A6023

This was one of the first bridges which I worked on as a designer, newly graduated from Cambridge in July / August 1967. David Garner was my mentor in the County Bridges Section of the WRCC Highways and Bridges Dept. on Balne Lane at Cliffe Field House in Wakefield. Jack Milburn was shortly to take over the reins as Chief Bridge Engineer from Joe Sims, when Joe moved across to the newly-formed Road Construction Unit next door. Maurice Allinson headed the  team responsible for new bridge construction in the single-storey timber hut next to the old house where the maintenance team were based. Cliffe Field House still stands but the timber huts and the prefabricated 2-storey buildings of the RCU have been replaced with flats.


The Engineer in charge of the design of Market Street Flyover was Phil Wilkes - he subsequently had a change of career out of civil engineering.


Market Street Flyover (I am using the name given for its construction) is remarkable on several counts:

  1. 1.The bridge is situated on a valley side, between the town centre of Mexborough and the valley of the River Don. Between the two runs the Mexborough New Cut Canal.

  2. 2.Market Street (diverted by the new ‘relief road’) runs therefore on a tight horizontal curve over the dual -carriageways of the new by-pass.

  3. 3.The south abutment of the flyover (on the left of the photo above) is heavily skewed and is founded on large diameter piles (bored from memory).


The decision to construct the bridge as a single span had been made before I joined the design team, but it may have been dictated by the curved geometry.


The superstructure of the bridge consists of cantilever and suspended span sections, with the precast beams of the suspended span supported on ‘half-joints’. The internal beams are pre-stressed concrete, but the fascia beams, being curved on plan, are reinforced concrete. The cantilevers are post-tensioned reinforced concrete, the post-tensioning being provided by Maccalloy bars. Half joints were difficult to detail for steel reinforcement, especially with the post tensioning anchorages being required. When I joined the team, most of the design was complete, but I do recall being involved with with these parts of the bridge.


In the decades which followed the constriction , the vulnerability of half-joints to reinforcement corrosion was realised - crack control was in its infancy, and special design rules were being formulated for this type of joint. Road salt leakage through deck joints was to become a major problem for this type of construction - hence the removal of the fascia panels ,clearly visible in the photographs, to facilitate inspection and maintenance.


Ina addition to the flyover, I was asked to design one of the reinforced concrete retaining walls between the bridge and the canal. This was my introduction to piled foundation design - vertical and raking piles, if I recall correctly. Photos of the wall on Leach Lane are included with the photos of the flyover, which I took in December 2012.


For photographs of Market Street Flyover and Leach Lane Retaining Wall see next page.

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