Civil Engineering Blog: February 2021

CIVIL ENGINEERING HISTORIC ACCOUNT OF STRENGTHENING WORK DONE on Br. 08 CARRYING THE B4632 ROAD over the RAILWAY at STANTON

When I started the “Bridge dept” in August 2005, the first job was to examine all 46 bridges and decide what work needed doing. There was a lot, especially on the bridges north of Toddington and a small team was created which went round cutting back vegetation around bridges, repairing or replacing fences, repairing, and pointing brickwork and deciding what repairs were required on the steel bridges. Work started at Broadway and slowly progressed southwards. Eventually it was mentioned that there was “a bit of a problem” with Bridge 08, so I went and had a closer look.


Large hole in the web.

Tear in bottom flange plate.

Apart from looking like a paint sample test operation, there was a large hole in the bottom of the web (see photo, and another of a tear in the bottom flange plate) of the main girder supporting the whole bridge!!!! Clearly some repairs were essential.

A detailed examination of the bridge was needed, but it was so heavily rusted that a shot blasting operation was needed before this could be done.

Shotblasting, with hole in the web visible.

Shotblasting the damage.

Blast cleaning and primer painting was done in late July 2006.

West section, showing jack arches.

North East corner.

and it then looked quite respectable!!

On 3.8.06, I met an Engineer from Atkins (acting for Gloucestershire County Council) who had looked at the bridge and was very concerned about its condition. It was agreed that we should introduce a 3T weight limit on the bridge, with traffic lights to keep traffic to the other side of the bridge, and that propping should be installed, and a repair scheme prepared.

Engineer John Sreeves (now a volunteer) of Halcrow of Swindon was contacted, and came and looked at the bridge, and they were instructed to design a suitable propping scheme. On 10.8.06, John returned and did a detailed examination, using a MEWP. (Mobile platform)

Propped section of B4632 bridge, in 2006.

A propping scheme provided by Mabey was approved and installation took place on 12.9.06. After a further inspection of the tower, traffic was then returned to normal.

A detailed repair scheme was then designed by Halcrow and, after tendering, a contractor was appointed and a pre-start meeting took place on 3.4.2007. By then it was discovered that each of the 20 alcoves on top of the abutments was filled with nesting birds, so the start date was put back! Eventually work began on 5.7.2007. Almost immediately it was discovered that there was extremely thick scale (up to 10mm) in places, which meant that the repair scheme had to be modified and a localised heavy duty blast cleaning operation was required. That started on 5.7.07, and the steelwork contractors were able to make a start on 6.7.07.

E. end N. side of cross beam - shotblasting, water leakage.

Cross beam 2.2 shot blasted.

Cross beam 1 repair - south view.

Cross beam 1 - jack arch fill.

Cross beam cut out for new web plate.

N.W. view old repair to cross beam 1.

S.E. view of web repair cross beam 1

S.W. view of repair to cross beam 1.

Second cross beam repair.

Water & Gas pipes from below_

West girder splice.


Web repair.

West girder web repair after painting.

The first item tackled was the hole in the web. Overplating was required, which entailed drilling holes to go over rivets. This was then extended to 3 panels as the steel was so thin. Work progressed for a couple of weeks and then on 20.7.06, there was torrential rain, and the cutting was flooded to a depth of 3Ft!! Amazingly the water had virtually all disappeared the next day – down the excellent track drains!!

More difficult were the problems with the cross girders where there were holes right through the web. Eventually sections of Jack arch brick had to be broken out. These areas were eventually repaired with concrete.

I attach a group of about 12 photos showing various shots of the steel repairs. These show much of the work that was done. In places old bolts can be seen, which formed part of strengthening work done by B.R.

Finally, the whole of the bridge was blast cleaned and given a 3-coat, resin-based paint treatment which was supposed to give about 25 years before touching up was needed.

West Girder repaired and repainted

All work was completed, and the contractors left site on 13.9.2007. The bridge was re-opened to dual 40T vehicles.

Volunteers then spent a further 6 weeks doing brickwork repairs to the tops of abutments and wing walls, and installing netting across the alcoves to stop future nest building.

PWay extension train under bridge 8, with Hawksworth Mess Coach.

Track laying towards Laverton Loop had then reached the Bridge and on 17.11.07 the first train (P-way) was able to pass under the bridge.

John Balderstone - Structures Engineer

Blogger's note:

This was all in 2006 / 2007, but was not blogged before, and we thought you might find it interesting.

What of bridge 8 today then, hasn't it got a speed restriction and a traffic light on it? Well, it does need further structural work after 14 years, that's the reason for the restrictions. A repair scheme is being designed, to return the bridge back to dual lane 40T capacity, but the start of works has been delayed by the pandemic, as you can imagine.

Addendum

Four extra pictures from John which show the extent that Station Road bridge at Broadway was covered. The fourth picture is of Pry Lane, one of the few made of brick.