Update on Broadway

BRIDGE 1 – COLLISION PROTECTION BEAM – WEEK 1 OF INSTALLATION

As mentioned last week, work on site on the north abutment started on Monday 3^rd Sept. In the last blog we reported that the two half length steel channel beams had arrived and 4 No. Mabey temporary support columns had been erected and bolted to the walls.

 

By Wednesday each half beam has been raised and manoeuvred into position and roughly to the correct level, using chain blocks attached to the bridge beams. 

Lifting the two half beams.

 

 

Extension pieces of Mabey columns were then bolted to the outer faces, at the tops of the main columns, to prevent the channel beams toppling over as the huge end brackets make them top heavy and unstable. 

Then the whole channel was raised to the correct level and packed there.

 

The joint between the two half beams

These two halves were then bolted together at the centre.

To make room for the new CPB’s the wasp stripe panels have been temporarily removed and will be attached to the new CPB beams spanning the road later. In addition the electric cables and conduits providing power to light the headroom warning signs have also had to be relocated temporarily.

 

Drilling holes into the abutment.

With the abutment channel beam now in place, drilling the 40 No. 35mm diam holes, extending 650mm into the abutment brickwork, was started. These will eventually take the 30mm diam resin anchor bolts. By Friday afternoon, all 40 holes had been drilled to a depth of app. 400mm.

 

General view of site, with drilling in progress.

As is the case with many of our bridges both abutment walls lean towards each other. At Broadway the lean is app 200mm in the 4.4M height. We believe that the reason for this is that the construction of the embankments was started before the brickwork had hardened sufficiently and so the brickwork (between 900mm thick at the top and about 2.2M at the bottom!!) was slowly pushed over as the embankment level rose. This line was built in a rush (some viaduct arches also fell down!!!), and we think that this was the result. When we did the major repairs and renovations in 2014 we discovered that the steel beams overhung the padstones at both ends – we imagine that the steel fabricator (Edward Finch of Chepstow) was somewhat baffled when they came to install them!!

As a result of this lean and some unevenness in the brickwork generally, the channels will have to be set vertically and packed in place. Then cement grout will be fed into the gap behind to fill the gap, which will be app 12mm wide at the top and 35 to 40mm at the bottom.

Once the CPB work is done on this side, the contractors have to do a small amount of minor repairs (scratched paint and wasp stripe panel replacement) to damage done on 1^st May 2018, for which insurers AXA will be paying.

Then the road closure arrangements will be switched over to the south half of the road and the similar work repeated on that abutment.

 8.9.2018 - John Balderstone and John Fancote