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