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A1 Improvement schemes. Redhouse to Wentbridge

Although only about half of the A1 is Motorway in the former West Riding, it is nevertheless one of the major Trunk Roads, and the works carried out in its improvement represent primary examples of excellence in Highway and Bridge engineering. It is therefore felt that even those sections which are not Motorways should be included in the Motorway Archive.

From the Doncaster By-pass at Redhouse the Trunk Road A1 was to be improved to dual carriageway standards with by-passes of Wentbridge, Ferrybridge, Brotherton, Micklefield, Aberford and Bramham before coming to Wetherby By-pass. The remainder of the route mainly followed the existing road as far as the approaches to Boroughbridge where a new by-pass was to link up with the Great North Road in the North Riding.

Redhouse - Wentbridge

The Redhouse - Wentbridge section was started in January 1960 and completed in 1961 at a cost of £879,000. The roadworks consisted of a new carriageway alongside the existing carriageway together with its improvement in parts to form a dual carriageway for a length of approximately 4½ miles.

The new carriageway was 24 ft. wide with a central reservation between new and existing carriageways not less than 15 ft. wide with side margins 12 in. wide and an 8 ft. wide hard shoulder. These dimensions were generally adopted throughout the West Riding improvement of A1.

The carriageway was constructed of sub-base as required, cement stabilised base 8in. thick, single course coated macadam 2½ in. thick and a wearing surface of hot rolled asphalt 1½ in. thick.

The bridgeworks comprised four main structures.

The existing Humber Head railway bridge carrying Trunk Road A1 over the Leeds - Doncaster line north of Redhouse was replaced by a new bridge consisting of a composite deck of pre-stressed pre-cast beams, with reinforced concrete counterfort abutments and wing walls founded on bored piles.

The culvert in Hampole Dike adjacent to the railway bridge was extended on the west and east side - with a reinforced concrete deck, counterfort headwalls and strutted abutments also on bored piles and mass concrete training walls.

A mass concrete retaining wall was constructed along the east side of Trunk Road A1 from north of the Humber Head Bridge for a distance of some 400 yds. To retain access to the properties alongside. A footbridge was added much later.

Robin Hood's Well culvert was of reinforced concrete and overall length of 107 ft. and carries the River Skell.

At Barnsdale Bar railway bridge, Kirk Smeaton, the railway cutting was filled in and after the east carriageway was completed the existing brick arch was collapsed and further filling placed to bring the west carriageway to required levels.

Barnsdale Bar culvert situated just north of the railway bridge was a 54in. dia. Armco riveted pipe with reinforced concrete head walls.

The Post Office Telephones had vital mains laid in 4 way and 5 way earthenware ducts from the south to Barnsdale Bar, a repeater station at Haven Café and manholes at frequent intervals access to which had to be maintained at all times. This proved particularly difficult at Humber Head bridge embankment where temporary deep manholes had to be constructed to maintain access requirements.

Major services included the Yorkshire Electricity Board 11KV cables in the verge with loops at Skellow Cross Roads, the Gas Board's 3 in. dia. service mains also in the existing verges to properties en route and the Don Valley Water Board's 10 in. and 4 in. water mains across the railway bridge. In addition the area was festooned with poles, including those of British Transport Commission, following the main line.

Items for demolition included a complete farmhouse with out buildings at Robin Hood's Farm, the historic structure known as Robin Hood's Well, with instructions to store as directed, and the buildings in Park Nook Quarry including a house used as the post office. The latter was in fact reprieved and preserved but required a mass concrete retaining wall to support the widened A1.

Parts of Barnsdale Forest affecting the roadworks had been removed as an advanced contract but much remained for site clearance such as walls and hedges, roadside furniture removed to store in the Divisional Surveyor's Depots. Recovered stone was cleaned for reuse in the walls for which the road was noted.

The drainage concept provided for a french drain system consisting of porous pipes on puddle clay later to be changed to concrete, the trench backfilled to ground level with filter media. Such construction catered for sub-soil water and surface water run off with catchpits having an 18 in. depth of sump at 300 ft. intervals from which silt could be removed under normal maintenance.

Some 250,000 cu. yds. of imported fill was brought to site on narrow roads to supplement deficiencies of cut available from site. Much use was made of the coalfield tips. Some of the shale was of excellent quality reserved for the sub-base of the road. This hard well burnt red shale literally "rattled" out of the trucks when tipped on a formation. Many of the tips had been smothered with soil during the war years to hide the glow that was emitted, these had purposely been set alight to render the unburnt clay, which was prevalent in the coal seams, to a more useful product. Nevertheless constant selection was necessary and tips in the Featherstone, Syndale and Bently areas were much used. Many a loaded truck burst into flames if the material became too hot and reacted to exposure through digging operations.

Whilst originally it was intended that the existing road remain in parts, a second phase was introduced, at additional cost, and resulted in experimental surfacings being over-laid.

A labour force in excess of 300 was reduced during the cold spell in December 1960 to some 200 with further recruitment in the following spring. This was normal procedure, all sites suffered, as the weather deteriorated and work was restricted to structures, here braziers and paraffin burners reduced the effects of the frosts. Opening was achieved within the contract period, at the same time as the completion of the Doncaster By-pass in the summer of 1961 not withstanding the inclement weather in the winter of that year.

Site laboratories were established on a minor scale for day to day testing, which was entrusted to a junior engineer. All imported materials were approved initially by the Laboratories and thereafter at frequent intervals for consistency. As operations involving coated materials developed, samples of materials were stored in 6 in. drainage pipes - an expedient method which avoided pollution.

The Contractors worked a double shift system, round the clock, supervision was called for at all times and put the staff under considerable pressure. A sign at Humber Head Bridge pronounced "Road Works for the next 48 miles any inconvenience is regretted".

A further delay occurred at Skelow Cross Roads where one "Smiler" and his masons, excavating the foundations for a wall unearthed a pile of bones. As becoming workmen with no concern for gentlemanly etiquette the jawbones were put on display. Clearly this was a matter for concern, the jaw bones were human and questions of missing persons abounded. The area became a "no go" area while the police were called in. In due course they pronounced the bones to be too old to concern them but advised that the curator of the Rotherham Museum be called in. The archaeologists found the remains to be too recent to interest them and so the bones were interred in a common grave without ceremony, covered over, and work on the stone walls proceeded.

Redhouse - Wentbridge was full of Folklore, historians will continue to argue the connection with Robin Hood.

An item in the "Site Clearance" section of the Bill of Quantities stated:

'Very carefully take down, marking the position of each stone, the ancient structure known as Robin Hood's Well situate near drainage 7,400 clean all stones as directed by the Engineer and cart to store on site where directed and dispose of surplus material. Cubic content above ground 520 cu. ft. approx. haulage not exceeding 2 miles'

The sum of £49.00 was inserted to cover the item.

Redhouse to WentbridgeThe stones of the Well were duly numbered for re-erection and a plan prepared showing the arrangement. Before preparations were made for its orderly removal it was inadvertently demolished. A truck delivering a load of burnt red shale from the tip at Snydale for use in the road works one Saturday 'dinner' time, left the existing road, careered into the structure displacing the stones. These were duly removed to prevent further damage and later stored in a stable at Womersly Park, the home of the Earl of Ross, one of the defenders of the well, whilst a decision on its rebuilding was made.

The stone canopy was erected about 1720 over the centuries old site of a spring about seven miles north of Doncaster on the edge of Barnsdale Forest, a known haunt of Robin Hood. The structure disappeared amid the controversy because of road widening. The Ministry of Transport offered to remove the Well stone by stone but it was not prepared to put it up again.

A public appeal fund was launched and the Doncaster Rural Council put the re-assembly of the heavy weight jig-saw puzzle into the hands of the contractors.

The well now re-erected stands not over a spring but on 6 in. of concrete foundations on the line of the Old Great North Road overlooking the high speed clearway of the new road.

Redhouse Junction Improvement

Redhouse to Wentbridge2In 1977, a scheme was carried out to improve the Redhouse junction. The principal object of the improvement scheme was to eliminate the roundabout at the junction of the A1, at the north end of the Doncaster By-pass, and the A638 Doncaster Wakefield Road. This was achieved by dualling and realigning the A638 to the south and carrying it over the A1(M) on a four span prestressed concrete structure, in addition there were various adjustments to the alignment of other local roads. 200,000 cu. m of colliery shale was imported as filling.

The contract for construction was awarded to AF Budge Construction Ltd who commenced the works in August 1977. The scheme was opened to traffic in the early summer of 1979 and cost £3.2 million.

Barnsdale Bar Grade Separated Junction

The construction of a two span prestressed concrete bridge over the A1, at its junction with the A639 at Barnsdale Bar, in 1985, eliminated a potentially dangerous at-grade crossing of the Great North Road. Interestingly this was one of the first structures in South Yorkshire to use air-entrained concrete in the abutment and pier splash zones. The contract was undertaken by A. Monk & Co at a cost of approximately £0.8 million and the works were supervised by the County on behalf of the Department.

Wentbridge Viaduct and By-pass

Wentbridge lies in the "bonnie Vale of Went." This is an area of high ecological value, designated as a site of special scientific interest. The River Went has Ancient Woodland on both slopes and folklore has it that this was one of the haunts of Robin Hood. When Queen Anne reigned Tom Sagle kept the Blue Bell Inn in the village, claimed to be the oldest hostel on the road, and a place where a frothy pint can still be had. Dick Turpin was on the list of Wayfarers who took shelter at the Inn.

The village was well known to motorists for the road's tortuous descents from both the north and the south. The poor visibility and narrowness of the road created a considerable bottleneck with queues of traffic forming behind climbing lorries.

The by-pass, which is nearly two miles long, runs to the east of the village. The 15 ft. wide central reservation was widened to 30 ft. at junctions and the verges increased to 12ft.

Redhouse to Wentbridge3The Wentbridge Viaduct carries the by-pass at the height of 96 ft. over the picturesque and steeply sided valley. At road level the crossing is some 1000 ft. and the gap was reduced by means of short approach embankments to give a span between abutments of 450 ft. Although the Went is only a small stream, the floor of the valley is subject to flooding.

The valley strata comprises of sandstones and mudstones of the middle coal measures, overlain by alluvium and magnesian limestone is to be found high in the sides on the valley. The underlying coal seams in the area were not considered by the National Coal Board to be worth exploring and consequently the absence of mining subsidence permitted the use of a hyperstatic structure.

In its day Wentbridge Viaduct was the largest viaduct of its kind in Europe, having certain unique features. Although bearing a superficial resemblance to other structures, with sloping legs it differed from them basically in its proportions and method of structural action. Unlike the majority of such bridges, there is no portal action and the structure acts as a three span continuous beam supported at abutments and by sloping legs which are pinned at the top and bottom. There are two side spans of 140 ft, a centre span of 190 ft, the span at the leg supports being 308 ft.

The roadway on both approaches slopes down towards the viaduct and crosses it on a downward vertical curve. This curve has been deliberately emphasised in the elevation of the structure.

In the planning stage the viaduct was submitted for the approval of the Royal Arts Commission and received with acclaim. It also had the distinction of being selected for inclusion in the exhibition of Twentieth Century Engineering by the Museum of Modern Art, New York in 1964. In 1998 it became one of the few bridges to be listed.

The contract was awarded to Taylor Woodrow Construction Ltd. and work began on the 4th October 1959 and opened to traffic in Nov 1961. The value of the contract was £682,000. The labour force reached a peak of some 210.

The deck of the viaduct is of concrete cellular construction comprising six cells with cantilevered footpaths on both sides. Traverse diaphragms have openings which permitted access between the various cells during pre-stressing operations. The main pre-stressing is by means of 204 No. 1 1/8 in. stranded wire cables which are continuous over the whole length of the deck. Their length is about 480 ft. between anchorages and they are placed external to the webs inside the cellular structure. The tendon profile is maintained by mild steel deviators with spring steel strips to facilitate stressing, cast into diaphragms. After stressing the strands were encased in fine concrete for protection connected by reinforcement to the webs. The 18½ miles of cable was manufactured by British Ropes Ltd. at Doncaster. This was the first bridge to use external cables in the United Kingdom.

During stressing of the strands strains were measured by Geoff Base of the Cement and Concrete Association to enable the loss of force in the cables due to friction to be assessed and is summarised in a paper by Base.

Over the haunches additional pre-stress is provided by cap cables, 30 ft. and 60 ft. in length, passing through the ducts in the top slab which were subsequently grouted. The anchorages of these cables being on the underside of the slab were stressed from the inside of the cellular structure from alternate ends to minimise friction losses.

The deck is fixed at the south abutment and free at the north abutment. Considerable horizontal thrust can be caused at the fixed end by unsymmetrical loading of the bridge and 14 hemispherical bearings lubricated with molybdenum disulphide have been used. To prevent large overturning moments this abutment was anchored back to a concrete block in the approach embankment by means of 23/4 in. diameter protected mild steel tie rods. The joint between the deck and the abutment at this end is a pre-compressed natural rubber strip. The relative movement is small, being only that due to rotation of the cellular deck under load. At the north abutment 14 mild steel rocker bearings have been used, together with comb-type expansion joint allowing a relative movement of about ±2 in.

The tapered legs are of reinforced concrete with their axis inclined at 54 degs. Again the construction is cellular with one central longitudinal rib and no traverse diaphragms. By virtue of being hinged at top and bottom the legs act purely as struts, no bending moment being transmitted from either end. The upper slab is thicker than the lower slab which causes the centroid of the cross section to be above the central axis. The resultant eccentricity of thrust counteracts the self weight bending moment effects.

Pre-cast concrete hinges with a working stress in the throat somewhere in excess of 4,500 lb. per sq. in. were used. Exhaustive tests were carried out on a short specimen hinge of full-size cross-sectional dimensions at the Cement and Concrete Association's Research and Development Division at Wrexham Springs to determine the suitability of the design before it was incorporated in the structure. Concrete hinges were used on a number of later bridges in the west Riding and resulted in a paper on the "Design of Concrete Hinges by" Sims and Bridle. The leg foundations are solid mass concrete blocks founded on sandstone rock.

The whole structure was of in situ concrete, and to minimise effects due to shrinkage, elastic shortening, settlement of centering, etc., shrinkage gaps 4 ft. wide were left open at each haunch directly over the legs, and the fixed end bearings were left temporarily free to slide. Closure of the shrinkage gaps was the last operation prior to stressing the tendons and until that time the three spans and the legs were entirely disconnected from one another. Immediately after stressing in was possible to jack the deck longitudinally to centralise it if any unsymmetrical longitudinal movement had taken place. The fixed end bearings were then concreted up to fix them in position permanently.

Another engineering feat was involved in the centering for the bridge structure. Five schemes were considered. In December 1959 Taylor Woodrow put forward a scheme based on the use of Bailey Bridge panels proposed by Thos. Ward.

In September 1960, after a great deal of design effort, calculation, load testing of Bailey panels and discussion with the West Riding engineers, Taylor Woodrow dropped the scheme, because the deflections would have been excessive, in favour of a scaffolding scheme.

Redhouse to Wentbridge4The proposal adopted was for a scaffold 'bird cage' on a 4ft. grid using about 120 miles of 3 in. and 2 in. tubing, founded on a temporary reinforced concrete raft laid across the valley floor. The design and erection of the scaffolding was sub-let to the Mills Scaffolding Co Ltd, erection taking from October 1960 until the following March. Messrs Hannay and Ward were involved. The scaffolding was designed for a wind velocity of 100 mph and assumed a total wind pressure on the structure of 80 per cent of the stagnation wind pressure. The traverse bracing was designed to take this wind pressure over the whole projected area of the scaffold structure together with the agreed restraint against buckling.

Meetings were held to discuss the design of base plates, fork head screwed reveals to support the timber bearers and soffit shutters, the use of couplers (both 90° and swivel types), the squareness of tube ends, and the design of spigots and spiced joints. Numerous loading tests were undertaken by Mills Scaffolding before approval was given to proceed.

Not withstanding the contractors responsibilities under the contract, as the scaffold structure was erected the Resident's Engineer's Supervisors gave meticulous attention to compliance with tolerances, to the installation of couplers, strappings and bolt tightness. All of which contributed to the safety of the temporary works.

The attention to detail was apparent when, during the stressing of the structure, the fork head reveals had to be released as load was transferred to the structure and everything worked as planned.

A request was made that that everyone involved should wear safety helmets, Mills Scaffolding replied that "they did not normally issue safety helmets to their workmen". Helmets were issued and later became standard practise on all sites.

The movement on the pinned couplers normally used to connect sway bracing was found to be unacceptable and only "fixed" couplers were permitted.

The great bulk of the concrete 14,000 cu. yds., was mixed on site and placed using concrete pumps, with air-driven conveyors being used for the sloping legs. Concrete surfaces being treated with DRI-SIL based water repellent compound.

Redhouse to Wentbridge5The major part of the abutments is buried beneath the approach embankment fill - the south abutment is 87 ft. high but only 30 ft. is visible. They are of reinforced concrete construction throughout except for the concrete encased steel beams supporting the bearings.

From the cellular box footings rise five independent skeleton walls which are braced by cross walls where they rise above fill level. The distance between adjacent skeleton walls was sufficient to enable earthmoving and compacting plant to operate satisfactorily. Triangular cantilever walls, with a ribbed patterned finish, spring from the back of the skeleton walls to follow the slope of the embankment and a deck slab spans across the walls to support the roadway.

The north abutment is founded directly onto soft sandstone rock but the south abutment is on 3 ft. 4 in. diameter in situ concrete piles 50 ft. - 65 ft. long, instructed under a variation order when the strata was found to dip at 50 to 60 degrees. Thus the whole structure is ultimately founded on sandstones of the Middle Coal Measures of varying degrees of hardness. The strata of the Middle Coal Measures being very variable provision was made for jacking the legs on the north side with Fressi flat jacks should any slight differential settlement occur.

Construction of the approach embankments involved the placing of 110,000 cu. yds. of rock fill, 30,000 cu. yds. being imported from a neighbouring quarry.

Redhouse to Wentbridge6Roadworks construction required excavation of some 200,000 cu. yds of material a large proportion of which was hard limestone requiring blasting and ripping with a Kelly ripper.

The roadworks was constructed of 6 in. sub-base, an 8 in. base of premixed cement bound granular material and a 4in. thick two coarse asphalt.

A two span bridge carries the Went Edge Road, over the By-pass, at its southern end. The final contract cost was £803,000 which included the additional costs due to piling the south abutment.