Work on bridge 34 at Gotherington

As the works on bridge 1 at Broadway draw to a conclusion...

... extra maintenance work has started on bridge 34, the long skew bridge (near our former sleeper depot) over the main road at Gotherington. Here is our report on the work, currently still ongoing.

BRIDGE 34- REPAIR WORKS

During our regular Principal Inspection, some bad corrosion of the structural steelwork was revealed below the deck on this bridge. During the non-running season window, and with the aid of the PWay department, we have therefore lifted the track and removed the ballast and old waterproofing materials.

You can see that this is quite a sizeable bridge, double track, and that it crosses the road at an angle.

Removing the ballast has also revealed rot in the sloping timber ballast boards, and even worse rot in most of the vertical steel ballast retention plates. 

These are now being cut out and new ones welded in.

This is one of the replacement steel ballast retention plates. You can also see how the deck has been cleared of track and ballast.

More rot has been revealed in some deck plate edges (see photos), also allowing water through to the structural steel below.

The plates are many and variable in size and shape and are being cut on site (see photo). The second photo shows the cut plates lying roughly in position ready for welding.

This water penetration has caused rotting of parts of the bottom flanges of the steel beams, in localised areas, where the beam sit on the padstones on the abutment walls. Notches have formed up to 80mm wide x 300mm long where the steel has been completely eaten away. 

Further rot has been revealed in some of the track bearers and web stiffeners, all of these will need repairs. To stop the water getting onto the padstones supporting the steel, deeper end of deck drains are to be installed (see photo of trench).

Part of the problem is the partial collapse of the ballast retaining walls at the ends of the bridge. These walls stop the ballast falling down on the road, but had failed to do the job properly in recent times. The walls are being broken out, and will be replaced.

Linked to that, the end of deck drainage was too high allowing water to get onto the padstones adding to the corrosion of the steel bearings. (See the deeper drainage trench on the photo further up).

There is also a problem with wear of the padstones beneath where the end bearing plates sit. This is aggravated by the presence of water. (see photo below of the water filled space). 

This allows the ends of the beams to move up and down under train movements. The movements can cause tearing of the deck plates, so the track bearer ends will have to be packed and the gaps filled with grout. Once all of the steel repairs are completed the whole deck will be waterproofed again.

The largest job of all is to blast-clean and paint the entire soffit of the bridge. This has not been painted since we acquired the trackbed about 35 years ago, and probably not in the last years of B.R. ownership either!!! Blasting and painting requires the entire road space beneath the bridge to be filled with scaffolding to form a working platform. Being the largest and longest bridge on the railway the scaffolding is a major task and again a full road closure has been necessary; no doubt you can see why.

The scaffolding has taken over 10 days to complete.

As you can see we have provided a walkway through the works to allow pedestrians and cyclists to get through.

The scaffolding has now been fully sheeted to contain the emissions from the blasting and painting operations. Blasting started last week and is being done in phases with priming in between, to stop surface corrosion of the cleaned steel from starting. We have been told that they may have up to 8 painters on site to get the work done as quickly as possible. Although the work is mainly underneath the bridge, painting cannot be done if the temperature is below 5 degrees, so forecasting completion, at this time of year, is almost impossible. The paint is a 3-coat; twin pack resin based system and should give at least 20 years before needing any attention.

Whilst the blasting is in progress little other work can be done in case any of the blast particles find their way through the gaps between the main girders and the deck plates. Fortunately, as the bridge is so long that welding can be done at one end whilst paint spraying is done at the other. The blaster/painters are also planning to work on Saturdays, when no one else is on site, to minimise any risk of conflict.

The work on bridge 34 is progressing well, but being our largest one everything is taking longer. We have until 27^th February to complete this one, but we have found quite a lot of corroded steelwork which we did not include originally, but which we now feel is essential.

Broadway bridge strike repair

On 27th February 2017 bridge 1 at Broadway suffered a relatively violent strike by the steel arm of an excavator being carried on a trailer along the road. It has taken almost 12 months for the railway to be in a position to commence repairs, these (mostly) being paid for by the insurance of the company involved.

On 3rd January station road was closed off to traffic for the repairs to begin. Below is a photograph of the works, and a progess report on the repair so far.

Bridge I at Broadway under repair - again.

The railway runs roughly due north from Cheltenham Racecourse, and Broadway station is immediately north of this bridge.

The bridge is a steel plate deck supported by a grillage of steel girders, as per picture below. 

This is a portion of a drawing prepared by our Consultants – Halcrow. This shows the layout of the “grillage” and also a cross section through the bridge. It basically comprises 3 large main girders tied together with a series of cross girders. Running between them are the track bearers and at right angles plate stiffening angles. This drawing was produced, after a detailed inspection had been done, to illustrate the 14 areas where damage had been caused to the structure.

When the bridge was built in 1903, it was entirely riveted. 

A 2014 photograph, taken prior to the first refurbishment. Note the large plate bolted across the front, from an earlier repair in 1975.

In repairs to subsequent damage by bridge strikes many parts were bolted together instead. In the 2014 repairs we used high strength torsion control bolts which have a domed head, with a hexagon nut, to replace many rivets.

Sadly we have to report that since the moderately serious strike on 27^th February 2017, which is the reason that these repairs were needed, a further strike has taken place on an unknown date. Incredibly, the damage resulting was in virtually the same locations.  However this has caused extra damage to the central main girder putting a localised but large kink in the 3-plate thick bottom flange 

 The steelworkers have now managed to just about straighten the steel again (see photo below).

Centre buckle

Centre buckle repaired

The repair work involves first weakening the steelwork in some places, and so no trains or any traffic could be permitted until the repairs are completed. The most important repair is to the upside, east track bearer, which has been displaced towards the east and badly buckled. 

 

Buckled track bearer.

During repair

After repair.

We had to remove the original rivets by grinding off the heads, then drilling out the shafts. The two bent bottom angles were then removed and the buckled vertical web plate straightened. Next new angles, site drilled to ensure that the holes lined up, were fitted and the 3 pieces were then bolted together. (see photos, before, during and after the repair was completed). Other sheared off bolts and rivet heads have to be replaced and then all repaired areas will be painted.

Buckled plates removed.

It has also caused extra damage to the east main outer girder, but fortunately, when we did the enormous repair work in 2014, the girder was re-built using bolts. Consequently this new repair was much easier and involved unbolting splice plates (see photo of the removed plates above) and making new longer ones. Similarly the damage to the west main girder has been simplified due to the bolted arrangements. See completed photos of both main girders.

Unfortunately the damage extended to the worst repair needed, that to the east upside track bearer, was across the westbound lane. Consequently we have had to close the entire road, causing inconvenience to all users of this road and especially to the garage and shop, right next to the bridge. Diversions are in place, and though the problem is not of our making and costs a lot of money and time organising the work, we extend our apologies to everyone affected.

At the beginning of this blog post there is a photograph showing the closed road, which has to include Heras fencing to stop people straying into the working area, and even crash barriers to stop vehicles running into the Heras fencing at night. Within the working area we have built a fully scaffolded section on which the men will work. This bridges the public footpath to provide a protected pedestrian walkway right through the site. You can also see an area enclosed with plastic sheeting. This helps to contain sparks, dust, etc from the operations and also provides an area which can be lit and heated to improve the working conditions, in the poor winter conditions, and to enable painting to be done, which otherwise cannot be done below 5 Degrees C.

It is really disheartening to have to suffer more and more strikes after the bridge was refurbished. There may have been more than a dozen now. A number of vehicles involved in the strikes did stop and do the honourable thing, but many did not and could only be observed from the damage suffered, and debris such as sheared off rivets found in the road. As a minimum the damage needs to be inspected and an assessment made after each strike, during which period no trains can run. In a worst case scenario the whole bridge could be displaced, thus closing the railway at Broadway for a considerable time. This could have serious financial consequences for us, now that the extension to Broadway is about to open. The provision of crash protection beams for the bridge, and a system of video camera surveillance, is therefore now being studied in depth.

Two Hedges bridge

Two Hedges bridge - strange name, but it's just south of the former Bishops Cleeve station site -

and if you look carefully you can see a white building in the distance that stands on the old goods yard once next to the station. It was recently converted to a nursery. This picture then is looking north.

Two Hedges bridge is an over rail type and is basically constructed from 6 riveted steel plate girders resting on padstones, on Blue Engineering brick abutments. Between each of the steel girders there are brick arches (referred to as Jack arches). These are only 4 ½” thick laid as a brick on edge. The bricks are then covered with a concrete topping to form a level deck. The concrete is a minimum of approximately 2” thick over the crown of the arch, and it increases to approximately 12” thick at the deepest part where it touches the steel girders. This concrete is then given a waterproof coating of what was originally supposed to be ¾” thick Asphalt, according to the copies of the 110 year old original drawing that we have for almost all of our bridges. The road construction is then laid on top of the waterproofing. 

 

The Jack arches cause a sideways thrust on the steelwork and to prevent them spreading apart, which would eventually lead to the brickwork failing and dropping between the girders, a series of 7/8” diameter tie bars was originally put in – 4 per bay. Unfortunately, due to the smoke and water from the steam, over many years, these bars slowly corrode away and break. 

At the last inspection this bridge had 10 of the original 20  tie rods either completely broken, or reduced in diameter to about 3/8” and so we needed to replace those 10.

 

Starting on 30^th October 2017, we had a line possession and then the contractors replaced these 10 bars - not as easy as it sounds and took almost two weeks for 2 men! The bars actually pass through the brickwork, which is extremely hard, so to do the change the brickwork had to be broken out around the tie bars, the bars inserted and tightened and then the brickwork made good.

This photograph shows part of two tie rods. The end section with a nut on,  being the original 7/8” diameter bar and the other more like 3/8” diameter!! Coroded down to only half, while road traffic has intensified, and steadily increased in weight. These bridges were built in the time of horses and carts.

 

Whilst we had possession of the line we took the opportunity to carry out pointing of the brickwork. The line had to be handed back for race trains on Friday 17^th November, but we just about managed a week of pointing, which enabled us to point both abutments and all 4 wing walls.

 

None of this is very exciting but is something which needs to be done. There is a lot of other work which needs doing, including steel repairs (the poor condition can be seen in a couple of the photos!), but unfortunately the Budget would not stretch that far.

Early next year we will start making good the damage from a bridge strike to the rail over road bridge at Broadway, while almost simultaneously a second project will be launched at Gotherington Skew bridge. Further updates of these will follow once we have some pictures.

2016 review of work done

During the year 2016 quite a number of bridging jobs were undertaken. It isn't always possible to give you a blow by blow account, so readers might appreciate an overview of what was done during the year.
The summary below also contains reports of recent works done, not yet reported on.

We'll start with:

1.      BRIDGE 0 – BROADWAY FOOTBRIDGE

The year started with the digging and concreting of the foundations to the stair tower on platform 2 (platform 1 had been completed in December 2015). 

 

Due to the platform height and lack of other means of access the concrete had to be pumped in.

On 10/2/2016, a week later, the two new staircase towers were erected. They had been manufactured off site by a specialist steel fabricator, and then blasted and painted 3 coats of paint by another specialist contractor.

On site the main span, from Henley-in-Arden, was being blast cleaned, then repaired and strengthened by more specialists.

We ourselves cleared away the lead contaminated residue using a special waste disposal company to take it away for proper disposal. Eventually the entire span was strengthened and cleaned and 3-coat painted, and was then ready for erection. Before that was done we installed all of the salvaged floor timbers.

Next the salvaged tower roof frames (after cleaning and painting off site) were fitted to the tops of the towers.

Then we were ready to erect the main span which, with the timbers, weighed 11T. This required a 60T crane, and because of the location and radii involved, the operation required 3 separate moves.

 

Scaffolding (clear spanning the track) was then installed all around the structure so that eaves timbers and dagger board installation could be done, and the final painting of the timbers could follow. 

This was followed by gutter installation and then roof sheeting fixing and painting. Finally the rainwater pipes were installed and the scaffolding was then removed. Apart from minor finishing around the towers the project has now been on standstill due to the complete lack of funding.

2    PRINCIPAL BRIDGE INSPECTIONS AND WORK PLANNING

Bridge 13 at Toddington being inspected

Through July, September and on 1^st November the final 9 Principal Inspections were carried out . This completes the P.I. programme of inspections on all of our bridges with the exception of Bridge 12 (Stanway Viaduct, which was done in 2010) and Bridge 44 (Hunting Butts Tunnel). These inspections should be done at 6-year intervals and we have now about caught up on the backlog. This P.I. work is in addition to the programme of visual inspections which aims for us to see every bridge, culvert and structure at least once a year. We do these ourselves.

From these inspections, particularly the Principal Inspections, a schedule of remedial works required is then compiled. They mostly require a cherry picker, so that a close up and detailed examination of every structure can be carried out. From these schedules work is prioritised and a programme of important work is costed. The figures then form the basis for our application for our budget funding. When the inevitably diminished figure is received, the programme is re-examined and then the bridges and structures that can be afforded are selected.

Further design, drawing and specifications are then drawn up. Tenders are sent out, and when quotations are returned, we are finally able to place orders and get some work done.

3    BRIDGE 1 – STATION ROAD, BROADWAY – STRIKE DAMAGE REPAIRS

Commencing on 19^th September the work to repair the relatively minor damage done to this bridge by an unknown number of lorry strikes (anything between 6 known and 12 suspected) was started. This work involved complicated safety issues and traffic management. Traffic lights and site enclosure fencing were installed, sheared off rivets and bolts replaced, and warning sign lighting conduits and cables (sheared off 4 times) were moved up to a higher level.

 

Inspection of Broadway, bridge 1.

The structure and walls were inspected for any more serious damage,

 

Moing the lighting conduit

and finally all damaged paint work was retouched. This concernes mainly bolt and rivet heads and the undersides of the lowest steel members, which had been scraped.

4    BRIDGES 1, 2 (CHILDSWICKHAM ROAD), & 5 (LITTLE BUCKLAND)

Whilst we had to put in hand the partial road closure at Bridge 1, we had an ideal opportunity to undertake some high level pointing work of the wing walls on these 3 bridges.

Broadway repointing

Childswickham repointing

We had hoped to do this as part of the Bridges to Broadway project, but mounting costs and pressure to re-open roads meant that it was taken out of that project. The abutment pointing had been done as part of the B2B project.

      BRIDGE 8 – B4632 – STANTON

This bridge underwent major steel repairs during 2009, which included blast cleaning and 3-coat painting. Over the subsequent years water penetration through the verge areas has occurred, which has allowed rusting of mainly the two outer pairs of steel girders to take hold. Unfortunately the design of this bridge is such that the two outermost girders carry the entire weight of the bridge, plus that of the traffic. Consequently we planned to dig out the verge soil to expose the concrete infilled deck (on top of the Jack arch brickwork), check why it was leaking and then repair or replace the original waterproofing. The final intention was to fill the verge areas with tarmac with a fall to the road, to provide further water leakage prevention. We started on the Malvern side, which contains a 9” gas main and an 8” (we were informed) water main. We found the two pipes,

 

Water main in concrete

Gas and unused water main.

but the water main was only 6” and was un-used. Unfortunately STWA would not allow us to remove it. The closeness of the two pipes posed practical difficulties and a re-think was required. We then found that the 200 mm plastic water main was actually in the Cotswold verge, and that verge allegedly also contained a possible B.T. fibre cable. Unfortunately the water pipe was completely surrounded with 75 mm thick concrete, which filled most of the verge, and so no trace could be found of the B.T. service. 

Removal of the soil from the Malvern verge exposed the underside of the top flange plate of the main support girder. Unfortunately this was quite badly corroded and in need of cleaning and painting. The Cotswold side was in a similar state. With the end sections of the verges slipping down our embankment exposing the service pipes, problems with excavating the Malvern verge and the Cotswold verge, plus further corrosion issues and the need to do further steel repairs, it was decided to terminate the work. We tidied up the Malvern verge and decided to create a larger project for the near future.

BRIDGE 12 – STANWAY VIADUCT

The problem there was on the upside, Toddington end. A small ballast retaining wall here was being monitored during inspections. It had been progressively leaning over, and had recently got much worse.

 

Ballast retaining wall leaning over at Stanway

This left a danger that the ballast could slip even further, undermining the track on this elevated position.

With our restricted budget, the work was delayed from last year, and with personal ill health issues, which pushed most of the projects for this year back about 3 months, it was almost delayed again. Obviously it had to be done when no trains were running so was rushed through in January 2017. Fortunately contact was eventually made with Graham Morrison and the work was done at pretty short notice and completed in about a week. 

It's another site where access is very difficult due to the double track from Toddington through to the viaduct, so needed quite a bit of thought. In the end access was obtained by running along the cutting embankment top, from Stow Road. The work involved removing the old brick wall and re-grading the ground. Then we spread some lean mix concrete as a base for the gabion baskets that were to be used. 

For those not familiar with gabions, they are basically large baskets made from galvanised steel mesh panels, that fit together to form a box. These boxes (each app 1M x 1M x 1M) are then filled with neatly stacked stone and form a very substantial and effective retaining structure.  As can be seen from the photo, they are ideal for installation on the filled ground condition that we have at this location. Then suitable backfilling is placed against the track formation and the area levelled off – job done.

In fact we have put back a longer and taller structure than was there before.

      BRIDGE 45 – SWINDON LANE, CHELTENHAM

A Principal Inspection of this bridge showed that the outer girders of this bridge were in extremely poor condition and needed difficult major repairs, or, more likely, the replacement of them both. The Jack arch form of deck construction common to the majority of steel bridges on this railway is in place with this bridge also. In order to replace the two outer girders it would be necessary to demolish and rebuild a panel of roadway app 1.5M wide along both of the edges of the road. These do include services, and are, as with bridge 8, also letting some water through. With a likely cost of perhaps £250,000 on a bridge that does not have trains running below, this was unaffordable. However the condition was so bad that something had to be done. The first urgent operation was to replace 7 tie bars that were missing or badly corroded with stainless steel ones. These tie bars prevent the lateral thrust from the Jack arch brick construction pushing the supporting girders apart, which could lead to the collapse of the brickwork. A small contract was let and the work was done in September.

 

New tie rods at Swindon lane

Ties made good

However the main structure was badly impaired and something had to be done with that too. So in conjunction with Halcrow it was decided to install a semi- permanent propping system which could stand for many years (50 +!). A scheme was drawn up and a contractor appointed. Access to this bridge, in a cutting with no direct vehicular access, was extremely difficult. In the end the local farmer allowed us access across his land to our fence line and then there was a long steep, badly surfaced track down to trackbed level. It was so bad that 4-wheel drive vehicles could not use it and finally a crawler tracked 360 excavator was used (even that had problems after some prolonged rain).  

The work involved constructing a concrete foundation (approximately 6 cubic meters of concrete) which had to be pumped 50 meters from the car park of St. Nicholas church. 

West end verge examination

This foundation supported 6 steel columns, which were clamped to the undersides of the existing steel girders.

Once in place these columns needed to be jacked up slowly and precisely to take some load from the structure, without lifting the bridge off its bearings. Unfortunately due to ill health of the contractor’s foreman, there was a week's delay which then caused a clash with Christmas. The work was finally completed on 9^th January 2017.

Our thanks go to St. Nicholas Church for allowing us the generous use of their car park and to Mr. Hanks, the farmer for the access facility.

7    CULVERT 39 A – BISHOPS CLEEVE

About 18 months ago the wheel of a JCB or the telehandler went through an old timber sleeper, one of about 90 covering a brick walled concrete floored channel, 5 Ft wide x 3 Ft deep crossing the railway at about 45 degrees at this location. Naturally we were extremely concerned at the possible state of the timber sleepers under the track and so designed a scheme to replace them all (app 24 M length of channel) with precast concrete slabs. These are 915 mm wide x 200mm thick x 2440 mm long and weigh approximately 1.25 T each. A contract was placed and the work, which had to be done in the shut down period (not a good time for dealing with water filled channels!). It was first necessary to lift a section of continuously welded track, and replace it once the work was finished. Our P-way dept dealt with that aspect. 

Construction work started on 9^th January 2017 and was completed on January 27^th. There was an awkward section on the Malvern side where the rectangular culvert went underneath a permissive footpath on our land and was replaced, at our boundary, by two 600 mm diameter pipes. These have approximately 40% of the capacity of our culvert and were installed by others. Just how that was allowed is astounding, as it tends to slow of the water flow causing much silting up.

To allow ourselves future maintenance access a rectangular brick chamber with a concrete roof was constructed, incorporating a large cast iron Inspection cover and frame.

8. BRIDGE 39 – STATION ROAD, BISHOPS CLEEVE

The problem here was that the ballast retention boards were delaminating and rotting away (photo). These boards are a vertical extension of vertical steel plates attached to the bridge deck. Their purpose is to stop pieces of ballast being dislodged (often during tamping), and falling through the gaps in the steelwork onto pedestrians or vehicles passing below.

New heavy duty tanalised boards have now been fitted.







We hope you found this report interesting. It shows that a lot of work goes on behind the scenes.
 
Report by John Balderstone, GWSR Structures Engineer, with assistance from Alastair Watson.

10.2.2017