Bridge work overview

With the 5 bridges to Broadway now spick and span, attention has focused on the other end of the line, where other bridges of similar construction are also getting much needed attention.

Here is a tour of inspection and update of several of them, being bridges 28, 32, 34, 37, 38, and 45. The first 4 are in the Gotherington area, the last on the southernmost tip of the railway.

ACCOMMODATION BRIDGE 37

Work on this bridge was described in an earlier post, and is now complete, with the embankment back filled and re-graded. The two pictures below show you the vast improvement made to this bridge's brickwork:

 

Before work started, a collapsed wing wall on the up side....

 

 ... and a fully repaired wing wall on the down side, a few weeks later.

Here we can see both repaired wing walls on the up side, now in excellent condition. This arched bridge type is less common on the railway; most of our bridges having a metal deck.

There is still a lot of pointing work remaining to be done, but our budget this year does not extend to do all that was needed, so just the cracks and localised areas were done.

 

ACCOMMODATION BRIDGE 38

Apart from a final coat of paint on the handrails this bridge is also completed. The work here was tidying up the pilasters, where vandals had removed some bricks. In addition the parapet wall on the downside had to be raised as the ballast was too high and was spilling over onto the public footpath below. Due to the height of the ballast, the handrail was too low for safety reasons and so the pilasters were extended upwards and an extra rail inserted. Some fence repairs were needed, and Andy Prothero and gang did a brilliant vegetation clearance job, as shown on his last blog.

 

Pilaster tops missing, ballast spilling over under the rail.

The same view from underneath, with ballast sitting on the girder

Repair work completed: Extra rows of bricks, higher pilasters with caps, and an extra guard rail.

BRIDGES 28 (STANLEY PONTLARGE, 32 (PRESCOTT ROAD), & 34 (GOTHERINGTON SKEW BRIDGE)

These all had the same problems:-

 

1.      Rotting or missing ballast retaining boards

These are found on all steel decked bridges and are installed to stop any pieces of ballast displaced during ballast tamping, or from rail traffic vibration, from spilling down the sides of the steelwork and falling down onto passing vehicles, or pedestrians. From the sketch detail attached (see below) you can see that the bulk of the ballast containment is done by 300 mm high vertical steel plates attached to the deck. Then to close off the gap back to the web plates of the main bridge girders, sloping heavy wooden boards (38 mm thick) are fitted. Unfortunately many of our bridges only have thin (12mm) narrow boards battened together and these also tend to warp.With the height of the ballast being greater than it should be, the bottom edges lie in the ballast where they rot away allowing gaps to form, and, in the worst cases, allowing the boards themselves to slip down into the gaps!

 

 





Here is an example of a missing ballast board, replaced by a plank of wood, but still leaving a large hole.

 

A worse example is this one on bridge 28, where a piece of ballast board has slipped and is in danger of falling into the road.

 

Repairs at last! New bigger and thicker ballast boards are being cut to size here, with old examples in the background, and replacements newly fitted in the front.

Here is the drawing of the ballast boards referred to in the first paragraph.

2.      End gaps adjacent to the pilasters.

This is an extension of the ballast board problem, and occurs at the end of the deck, where there is a gap (varying in width), which again allows ballast to slip down onto the padstones under the steel girders, and eventually into the road again. The simple solution was to build a small brick pier against the pilaster brickwork, to close these gaps.

 

3.      Failure of mortar grout under the padstones (mainly of those beams carrying the track)

 

The problem with these is that the mortar breaks down beneath the plates which supports the ends of the beams that sit on the abutments. The resulting gap allows the steel beams to move up and down under moving wheel loads. Without the mortar support the beam ends are then only supported by the deck plates, and, as we found on the B2B contract, this leads to plates tearing followed by waterproofing breakdown allowing water in and causing the steel to corrode. The problem is not an easy one to solve, as it involves jacking the beam ends and inserting new grout. A temporary scheme of inserting temporary steel packs has been carried out, until we have funds to do a better job. Unfortunately there are no photographs of this work.

 

One final shot is of an inspection done on Bridge 45 (Swindon Lane), earlier this year. Quite a tricky one to get a machine to, but we managed it, thanks to a helpful farmer. The machine is standing on the disused trackbed, in GWSR ownership, south of Cheltenham Race Course station, between Hunting Butts tunnel and Pittville, where our trackbed ownership actually ends.

That is about all of the bridge work that can currently be done with the budget available. Hopefully there will be a fresh allocation next year.