Good news to report this morning - Childswickham Road bridge has reopened to road traffic!

On Wednesday two large lorry loads of ballast arrived, and were unloaded near the bridge, after driving down the trackbed from Broadway station. Due to the wet weather, they could not be spread over the bridge deck, as it had to have a protective textile fitted first, which needs to be done in the dry.

Here is the reason the ballast could not be added immediately - the rolls of textile still need to be fitted. In front is a pile of Cotswold crushed stone, which is for the drainage at each end. The signage had already been fitted.

Thursday was a brighter day, and the contractors were able to fit the textile, spread out the ballast, and with that, the refurbishment was sufficiently advanced for the road to be reopened on Friday morning. The first person to alert your blogger was a Childswickham resident - thank you !

Here are two views of the bridge taken this morning. Signage on, balustrades on, Cotswold crushed stone spread out along the abutment top and part way down the wing walls. Road open and ready for traffic !

One more bridge to go - Peasebrook Farm bridge is expected to be completed within a few days.

Low winter sun is affecting work ! But only for the cameraman... repair work continues steadily, and here is our next update:

Bridge 2, Childswickham Road

The parapet steelwork has now been erected, and the haunching to the ballast retaining walls has been completed (just visible on the photos). You can see how surface water from the deck is guided off and away from the bridge. Not visible are the new road height warning signs which have also been fitted, and the bird netting at the tops of the abutments.

Love the new balustrades!

All things being equal the scaffolding removal may start tomorrow, following completion of which the brick pointing to the abutments can be completed. The end of deck drainage and some fence works also have to be done, together with the fitting of the timber ballast boards and finally the deck waterproofing. Then lastly, the laying of ballast as waterproofing protection. Somewhere amongst that lot the road will be re-opened, it's difficult to predict exactly which day yet.

Bridge 4, Peasebrook farm

The concrete slab was finished last Thursday and the shuttering has been stripped and the site tidied up. Our three photos show shots from various angles. 

With the parapet railings it look rather like a giant double bed!!

We'll take another look later this week to see what happens next.

 

There has been a bit of dialogue between our structures engineer and other engineers reading the blog, which was very enjoyable for all parties concerned.
Following a question raised by a reader about the drip strips we have had added, Bridges Engineer John Sreeves of CH2M Hill has sent us a longer, and very interesting reply which we think will interest our readers. Here is what he said:

During the restoration of these bridges, we became aware of various shortcomings in the original design that were conspiring to impair future durability. Most of the bridge problems are caused by water penetration and poor drainage which we hope to address, along with improved accessibility to some areas for inspection and painting. The brick ballast walls at the deck ends were in such a degraded and collapsed condition that they had to be totally rebuilt. So for the first time since 1903, the ends of the rail bearers and main beams were exposed to reveal extension corrosion. Where the brickwork had been in direct contact with the steel for 111 years, it had not been possible to apply any paint to the interface, which had attracted water through capillary action. The tops of the ballast walls were in contact with the underside of the deck plate, where similar wet conditions prevailed.

As the ballast walls were to be completely renewed, the opportunity arose to make improvements to access and drainage details without in anyway compromising the original design or affecting the heritage of the bridge which we were keen to preserve. To this end, drip strips 25mm x 8mm were welded on to the ends of the deck plates so that water can drain freely off the end of the bridge deck and not percolate along the underside of the deck plate. Furthermore, the addition of a drip strip serves to strengthen the end of the deck plate which is only 3/8” (9.525mm) thick and is quite flexible. It should be appreciated that the deck plates were never intended to carry the weight of ballast, track and live load. In the original design, all of these bridge had directly fixed track on longitudinal timbers mounted over the rail bearers for direct vertical load transfer. The deck plates were simply non-structural coverings over the underlying grillage. Handwritten additions to the drawings show that these bridges together with the others on the railway were converted to ballasted track in 1928, which would have been about the time when the original longitudinal timbers had become life expired. Consequently the additional load applied and flexure has caused fatigue cracking in the plates which we have had to repair.

To ensure accessibility for future inspection and repainting, the ballast walls as rebuilt are not all uniformly 9” (229mm) thick as per the originals. We have notched around the ends of the rail bearers and main beams to ensure a 75mm gap. Also the tops of the ballast walls are kept about 15mm down from the soffit of the deck plate. The intention is that all metal surfaces on the entire bridge shall be repaint-able with at least a fine nozzle spray with the exception of the undersides of the bearing plates. Unfortunately some areas of the main girders remain extremely difficult to access for cleaning and repainting where masked by the pilaster walls, but it should be possible to get a spray nozzle into the gaps in the future. The three-coat epoxy based paint system we are using is the best available that complies with Highways Agency and Network Rail specifications, and a 25 year life is expected.

Further enhancements to durability have been attained by the installation of transverse filter drain pipes at the back of the abutment walls. It had been noticed that seepage through the abutment in the vicinity of the bearing plinths was causing permanent damp conditions and frost spalling. The bearing plinths are highly loaded but surprisingly they are cut from soft sandstone unlike the indigenous limestone of the area. Being highly susceptible to weathering it is essential to keep them dry, so the installation of cut off drains will intercept and prevent rainwater getting to the upper areas of the abutments.

Finally, bird mesh has been fixed to the abutment shelf pockets between the beams as the accumulation of nests, feathers and faeces is very unpleasant and has a deleterious affect on paintwork!

John C Sreeves 

Thank you John !

We've been back to the two bridges being worked on twice over the last two days. There is steady progress!

Here is what we saw:

Bridge 2, Childswickham Road

The gaps beneath all of the steel bearings have been grouted up and the ballast retaining walls are now completed, as shown on the two photographs below.

Looking north, towards Broadway station

Looking south

Note the thicker looking deck plate ends, indicating the drip strip welded on here. This will cause water to run off this side of the ballast retaining wall, also newly installed. No more water running down underneath the girder and causing it to rust!

The lattice parapet steelwork has been made up and delivered. It is expected to go on later this week.

Bridge 4, Peasebrook Farm

Yesterday, the shuttering to the ends of the deck were complete, with the end re-bar cages installed:

 

When the above two pictures were taken, concreting was due to take place early the following morning (12 to 15 Cu. meters expected).

We then went back today, for a follow up picture:

All is ready for concrete

The rebar cages are all in place, and the shuttering has been erected around it. All is ready for the concrete pour.

Because of the size of the slab it was necessary to transfer the concrete mix in using the excavator bucket, as can be seen on this photograph:

 In this last picture, the concrete is being vibrated in. The Malvern side balustrade is already in place.

 Our next report should show the concrete deck in place, and, we hope, the new balustrades at Childswickham Road.