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.