BRIDGE 32 – PRESCOTT ROAD BRIDGE REPAIR CONTRACT

3^RD JANUARY TO 28^TH FEBRUARY 2023

Starting in June 2022, after 6 months of design, drawing, tender documentation and tendering by our volunteer Chartered Engineers, we finally appointed Walsh Construction to do this contract. The road between Gretton and Gotherington had to be completely closed for the entire period and 12 weeks’ notice had to be given to Glos. CC and a fee paid to get the Licence for this!

Work duly started on Tuesday 3^rd January 2023 with our own P-way team lifting the track and moving it out of the way. 

Drone view of track removal, by Paul Fuller.

 

Track panels removed, ready for bridge work to start.

 

 

 

 

 

 

Walsh’s then removed the ballast and stockpiled it for re-use. The next task was to remove the old ¾” asphalt waterproofing which had failed and was leaking. 

 

 

 

 

 

 

 

Large and small holes in the deck

 

 

 

Example of deck repair made.

 

 

 

 

 

 

This then causes corrosion of the 3/8” thick deck plates which rot into holes. These rotten parts have to be cut out and new plates welded in. 

 

 

 

 

 

 

Concrete protection and drip strip.

 

In addition we now attach a vertical steel drip at the ends of the deck plates to stop water tracking below the plate by capillary action. In the picture on the right you can see props being placed from below.

 

 

 

On this bridge 6 of the 14 stone bearing blocks supporting the entire bridge steelwork were in poor condition (cracked and worn) and needed replacement. To do that the steelwork had to be supported on heavy duty propping provided and installed by Mabey.

 

 

 

Naturally, the entire area beneath the bridge has to be provided with a fully boarded scaffolding to enable the work to be done safely.

 

The existing ballast retention walls at the ends of the deck were in poor condition, and the end of deck drainage was too shallow. The result of these factors is that the ends of the steelwork constantly get wet causing further corrosion. The wetness also contributes to the failure of the stone bearing blocks. These walls were all exposed and some of the steelwork which needed repairs.

 

Enclosed scaffolding for shotblasting (lead paint risk).

 

This bridge has not been painted in the 40 + years that GWSR has owned it and it was our intention that it should be done. With the extent of corrosion and poor condition of what paint remained we opted for our preferred approach which was to blast clean the entire steel structure and to apply a 3-coat, 2-pack resin based paint system which has a 25 year guarantee before needing any attention. To do this work the entire structure has to be encapsulated to contain the blast debris and paint spray particles. The encapsulation is shown in the photograph above.

 

Concrete wedge for additional protection.

 Meanwhile, up at deck level progress was being made with making good the ballast retention walls. Part of the reason for their failure is down to the vigorous mechanical tamping which is done these days. We now provide a concrete wedge at the ends of the walls to provide additional protection. Notice also the damaged pilaster cap top right.

 

Outlet from drain to pit in road.

The end of deck drainage is then laid just outside this concrete wedge and the pipe is taken down the embankment slope. This drainage not only takes the run-off from the deck but any rainwater falling near the deck helping to eliminate, soft spots.

 

 

 

 

 

Steel deck primer applied.

 

 

 

With the blast cleaning and painting being completed the waterproofing of the deck was to be the last task. This also requires the deck to be blast cleaned and then a bright orange primer is applied.

 

 

 

 

 

 
This is followed by a white waterproof finish coat.

Whilst the main steelwork was in relatively good condition, with just small local repairs required, the lattice parapets (Left and right) were very poor. We therefore opted to remove them completely and replace them with new, having both a galvanised and a painted finish.

Protection applied to waterproofed deck.

 

The white finish coat is then covered with a rubberised sheet to stop any ballast from damaging the lower coats.

 

 

Unfortunately, one of the stone pilaster cappings was seriously damaged by flail vegetation clearance and a new one was installed. The new pilaster cap can be seen on the top left, as viewed from the roadside.

Contractor spreading new ballast over the bridge, looking south.

The contractor then replaced the ballast.

 

Track replaced, and ready for the race special trains.

Then P-way came along and replaced the track.

View of completed works, with new parapets and pilaster cap.

 

Malvern view from road level.

Cotswolds view, with the road leading to the Prescott Hill climb.

Finally I attach 2 photos at road level above. Note new low headroom warning signs (provided by Glos C.C. but installed by our contractor). These are now circular (prohibition) instead of triangular (warning).

 

Collapsing fence.

 

 

Last but not least, we have culvert 31 B running under the road, alongside the abutment, and then slewing back onto our land. The wall of this held up the road and the end 1.8m x 230mm was pushed forwards, the fence was collapsing, and the exit for the ditch was blocked. This was all repaired and a new fence installed after the roadside ditch was cleared to try to improve the flow into the roadside ditch.

 

Culvert wall pushed outwards

 

The work was completed a day early on 27^th February 2023.

Sadly, I was unable to visit site during the contract, because of my failed and very painful hip and so supervision of the works was done by Ian Scholey, John Sreeves and Peter Lewis. The photos have all been provided by Ian Scholey.

My hip has now been replaced and I am recovering!! I hope to be fully mobile again by mid April!!

 

Report by John Balderstone – Structures Engineer. 26.03.2023.

Bridge 32 repair.

 

BRIDGE 32 – REPAIR CONTRACT – JAN 2023 – first 3 weeks to 20.01.23.

Back in June 22, preparation of a scheme to carry out repairs and painting of Bridges 28 & 32 was started using the data from our Detailed Examination reports to create a comprehensive schedule of works required. Both bridges had similar issues – mainly, leaking decks, collapsed end of deck ballast walls, minor steel repairs needed, and were geographically quite close, so it was decided to do both. Neither had been painted since the GWSR acquired them over 40 years ago, so blast cleaning and painting was also to be done.

Up side view of rusty parapet.

The work would require the road between Gretton and Gotherington to be completely closed and so an application (min 12 weeks’ notice required) was made to Glos. C.C. by our Traffic Management company. GCC granted it without any issues. Unfortunately, being a country area, only a relatively long diversion route was available. Liaison with the two local schools and businesses on the route was also established. It later came out that GCC were planning to arrange their own road closure to enable them to carry out a road improvement and lining operation during part of our closure, but we beat them to it!!. After some negotiations we have managed to agree plans that both contractors are happy with, which will save another closure, at a later date!!

Volunteer Bridge design Engineer, John Sreeves was busy preparing the Construction drawings, specification and tender documents. Tenders were sought on 3^rd September but the programmes that came back showed that it would be extremely tight to do both bridges between 3^rd Jan. and 28^th Feb. Consequently the tenders had to be revised to omit Bridge 28.

The GWR Trust then agreed to fund it (partly with money from the estate of former volunteer Civil Engineer – Peter Muir). Finally an order for Bridge 32 work was placed with contractors, Walsh’s, on 14^th November 22.

Work started site on Tuesday 3^rd of January 23, with the installation of the contractor's welfare unit in the road below.

Contractor's cabin in the road.

and the arrival of items of plant and machinery. 

Contractor's machinery.

On Wednesday 4^th Jan. GWSR P-way then lifted the track and sleepers.

Track being lifted by the PWay volunteers.

 

Track removed (3 panels).

 You can see some steel brackets sticking up from the deck plate. 

Deck plate with former brackets.

These were to fix large (approx. 19” x 6”) hardwood timber way-beams to the deck. These carried the rails, and there was no ballast or sleepers. In March 1928, the timbers were removed, and ballast and sleepers were added. This added about 35T of ballast (340mm thick below the sleepers) to this small bridge, which has caused spillage problems, ever since!!

A very important part of the work would be the removal and eventual replacement of 6 of the 14 large stone pads which carried the main bridge steelwork. Obviously, the steelwork needed propping,

Up side view showing props.

 and a scaffold deck was also needed for the works.

Up side view showing scaffolding and encapsulation.

The paint to be used is a high quality 3-coat resin-based product (used on oil rigs, etc) and this requires shot blasting to give the necessary surface preparation required. This should give a min. 25 years life before any maintenance is required. The blast cleaning operation requires the entire steelwork to be encapsulated to stop the spread of blast emissions. 

Encapsulation of the works area.

The steelwork sub-contractor started on Monday 16^th Jan. removing the brackets from the deck, and was arranging for a couple of small areas where there are holes through the ends of the deck, to have plates welding in.

 

Deck plate holes revealed.

 

Investigation into the state of the end of deck ballast walls (One had virtually collapsed and the other 3 were cracked) was in hand.. 

 

End of deck ballast walls. with angles.

Parts of these were also broken out to expose the ends of the steelwork where repairs were needed. In parallel, below the deck breaking out of the cracked and defective stone bearing blocks was taking place. 

Deck plate holes and bottom flange plate missing.

 

Props installed.

After two days of delay due to the very cold weather the shot blaster started work on Wednesday and had already blast cleaned and primed the main central girder, by yesterday. 

Centre girder blast cleaned and primed.

Meanwhile, on the upside, low mileage side, the drainage outlet pipe from the planned end of deck drains, has been installed, together with a set of steps to make track access safer in future.

Drain outlet and steps.

Finally work has started to rebuild the top section of the brick wall which retains the road on the Upside, low mileage side. 

Retaining wall and standing water.

 

Work is also planned to investigate why standing water in the ditch from Culvert 31 B, which passes around the abutment, cannot get away.  

 

 

This causes the ditch to silt up and, in turn the inside of the 3Ft. x 3 Ft. brick culvert.

Interior of culvert.

Detail of internal view of culvert.

Thanks to Ian Scholey and Jonathan Taylor (Lineside drainage) for the photographs.

Report by John Balderstone

Structures Engineer GWSR (20.01.2023)

Br. 12 – STANWAY VIADUCT REPAIRS

Blog covering the entire 10-week contract.

Unfortunately, this our largest structure, required a large quantity of rather uninteresting repair works and, naturally there is a vast amount of repetition involved!! Not too exciting!! 

Stanway viaduct, with scaffolding.

Despite that, the GWR Trust kindly agreed that they would fund these very important works on what is a really iconic structure.

There are 4 main types of work required. These are: -

1. Corner re-casing. The problem is that vertical cracks appear close to the corner on both faces of a pier, and as happened to pier 8 in April 2019 (LH photo), the entire corner about 3M high x app 250 to 350 mm along both faces fell off. 

 

 

 

This was repaired in March 2021. The work involves removing the cracked bricks and toothing out the brickwork to enable new bricks to be inserted (see RH photo). 

The corners are then strengthened by the building in of 5mm diam stainless steel twisted helical bars into the joints. These wrap around the corners and extend along both faces to tie the corner into the sound face brickwork alongside.

 

Special repair of bullnose feature, from above.

 

2. Replacement of cracked, frost damaged, or missing bricks. This is fairly obvious as to what is required. A frequent item is missing bricks from the holes where the temporary curved formwork was supported during the building of the arches. (photo below).

Missing bricks

 

3. Hollow brickwork. This is where the bonding between facing brickwork and the inner core brickwork has failed with linking bricks cracking right through. The solution is to drill at an angle into the brickwork, through to the inner sound brickwork and install stainless steel anchors which are grouted into place.

4. Pointing. This is a very common problem on older structures and the old crumbling mortar has to be cut out and new rammed in.

 

 Repointing work on various parts of the arches.

 

The work started in mid-September 2022, and, as the ground gets very boggy and soft, the first thing was to construct a main access route onto site was created using very thick heavy duty interlocking plastic mats (see photos below).

 

Interlocking mats.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Naturally, as the work extended to all faces of the piers, including the spandrels (the high-level side walls above the piers/arches) very extensive scaffolding was required. (Photos below).

Extensive scaffolding

 

Spandrel above pier 7.

 

The work started with pier 7 and then 6 and 5, with the spandrels above, following. Some work was also done to the lower parts of the arches, just above the piers.

Repointing work done.

 

The extent of the work was based on the 228-page report received from the very detailed examination done in October 2018. Most of this was done by men working from the parapet, suspended by ropes (photo below). 

Abseiling to examine the state of the structure.

 

With the continuing deterioration in the subsequent 4 years and with the somewhat limited accessibility issue, an additional 15% to 20% of additional items have been found and dealt with. Our Chartered Engineer volunteer Peter Lewis, who joined early last year, did a magnificent job of surveying and identifying the extent of the hew work, in conjunction with the contractors.

Because of the scaffolding and the localised nature of the work, taking useful photos has been difficult, but a small selection is included.

All work on site, including the removal of the scaffolding, was completed before Christmas. The temporary road mats will be removed in the first week of 2023.

We are grateful to the local tenant farmer, who kindly moved the grazing horses into an adjacent field for the duration of the works, and to Lord Wemyss for permission to work on his land.

Photos have been provided by me, John Fancote. Peter Lewis and the contractors site manager – Mark Williams.

 

Prepared by John Balderstone - Structures Engineer GWSR. 2^nd January 2023.