Loughor Viaduct replacement

13th March 2013

Constructed in 1852, the Loughor viaduct is a 220 metre long, eighteen span railway structure, constructed mainly of timber, which carries a single track railway line over the Loughor Estuary between Swansea and Llanelli in South Wales.

Originally one of Brunel’s once numerous timber viaducts, the superstructure has since been entirely replaced and it has received substantial re-designs and strengthening works in subsequent years, last being refurbished in the mid 1980s.

Now, detailed site investigations and conditional surveys have determined that the viaduct has reached the end of its lifespan. Network Rail and Carillion are replacing the complete structure, including the existing piers within the current track alignment, with a new viaduct capable of supporting two tracks as part of the larger, £50 million Gowerton Re- doubling Scheme. The work is jointly funded by the Welsh Government and Network Rail.

Design Criteria

One of the primary considerations for Tony Gee and Partners in designing the replacement for Loughor Viaduct has been the construction methodology and how the new viaduct can be constructed within the limited 250 hour blockade provided by Network Rail in March 2013. As there is only a limited period of rail disruption available, the vast majority of the construction had to be carried out in advance, allowing the switch over from the existing to the new viaduct during the shut down period.

This resulted in the new bridge being designed to be constructed in sections and launched longitudinally from the west bank alongside the existing viaduct and slid transversely into position during the blockade in March.

The existing viaduct is a Grade 2 listed structure, so listed building consent to demolish it was required before work could commence. Network Rail and Carillion planned to retain as much of the existing structure as possible and the east and west abutments have been incorporated into the new design to retain some of the heritage of the original viaduct.

Loughor Viaduct – Launches 1 to 4 from STUDIOME on Vimeo.

Although the viaduct was originally double track, it was single tracked in 1986 by British Rail due to structural concerns. In addition, a speed restriction was imposed for both freight and passenger trains. Such capacity constraints were having a negative impact on the immediate and wider economy of the region as the bottleneck was causing unacceptable delays. The new viaduct at Loughor will therefore not only be beneficial to the local community but will contribute greatly to the economic regeneration of the region and Wales as a whole.

Environmental constraints

With Loughor being a designated conservation area, ecological impact assessments were carried out in the form of desk studies, surveys and consultations with stakeholders such as the Carmarthenshire County Council and the City and County of Swansea planning and environmental departments. The existing viaduct is situated within or adjacent to several sites of European importance for nature conservation. These include the Carmarthen Bay and Estuaries Special Area of Conservation (SAC) which was designated in 2004 for the presence of important habitats, SSSI (sites of special scientific interest) and Ramsar wetlands.

Consequently, prior to commencement of the project, flood defence licences and a marine consent had to be obtained. Several months of intense consultation were undertaken with the Environment Agency for Wales, the Marine Consents Unit, the Countryside Council for Wales and the environmental departments of local councils during which the sensitivity issues of the area concerned were addressed.

The surrounding area was also designated as a Special Protection Area (SPA) as it is an important wildfowl overwintering site, regularly supporting over 20,000 birds. As a result, mitigation measures were taken to minimise disruption by carrying out works such as piling for the foundations of the new structure outside the winter period between November and February. This reduced the potential for any significant impact on bird migration.

As part of the agreement between Network Rail, Cadw (the Welsh Government’s historic environment service) and local authority planning and environmental departments, some of the existing timber trestles will be retained. Four will stay in their original place as part of the new structure, while several others will be re-erected close by as an acknowledgment of the heritage of the viaduct.

Piles and beams

The design of the new bridge is for a steel and concrete deck supported on new piers 36 metres apart – three times the span distance of the old structure. Twelve 1200mm diameter permanent steel cased piles will form the foundations for the new structure while six temporary piles will facilitate the launch of the new bridge on the north side of the existing viaduct. In order to minimise disruption in the estuary, Carillion employed a method of installing the piles using cranes and piling rigs situated on jack-up barges which were towed into position by four tugs.

Despite adverse weather conditions throughout the operation, and having to deal with one of the highest tidal ranges in the UK with river flows reaching up to eight knots on high tides, this phase of the works was successfully completed in July 2012.

Constructing the crosshead beams in situ working below the existing structure would have been difficult. It was therefore decided to pre-cast the concrete side panels and lift them into position using a 350 tonne crane working off the jack-up barge. Once in position, the main beam reinforcement was fixed and concreting completed to each crosshead.

On completion of the permanent crosshead beams, temporary steel crossheads and slide rails were constructed to facilitate the launching of the new steel deck sections.

Steel deck – and concrete

The bridge deck also had to be manufactured and placed in position without interfering with either the live railway or the local wildlife. Specialist manufacturer Mabey Bridge held a series of planning meetings with designers Tony Gee and Partners and main contractor Carillion to establish the suitability of steelwork to launch and slide. Design discussions at these initial meetings covered the number of launches, nose and tail design, splice design and positioning.

The main design consideration was that the steelwork had to be detailed to allow it to be launched and then slid sideways into position.

Following agreement on design, Mabey Bridge began a three month programme of fabrication of the 1200 tonnes of structural steelwork and walkways, with a total length of 236 metres, at its modern manufacturing facility in Chepstow, South Wales.

As well as fabrication, Mabey Bridge was contracted to oversee site assembly, including temporary pier cross beams, launch of the structure in four phases and slide.

The finished steelwork was transported to site by road in girder sections each 24 metres long. These were assembled in a laydown area on the west side of the estuary. After the assembly of each of the four phases, the structure was launched over the river onto the temporary piers. Following completion of the launches, in December 2012, the steelwork was jacked down onto its permanent bearings.

Once reinforcement was in place, the concrete deck slab was cast in bays to a designed pour sequence using a mobile concrete boom pump and rigid delivery located on the west and east banks of the estuary. Once cured, the new deck was waterproofed using an approved membrane system.

The track goes on

Ramps at each end of the viaduct were constructed to allow vehicular access. Track ballast was delivered by road and placed on the new deck using rubber- tyred excavators. G44 sleepers and rail is also coming in by road before being placed into position.

Once completed, track protection matting will be placed for the full length of the deck in preparation for access for the demolition of the existing viaduct.

The blockade

The existing bridge will be completely closed for 250 hours between 24 March and 3 April 2013. During this time the existing bridge will be removed and the new structure slid into position on the same track alignment.

Demolition will start with the removal of the existing ballast, rail and deck timbers which will be loaded by excavator and transported from the bridge. The remainder of the bridge, which includes the steel girders and trestles, will be demolished using 65-tonne excavators equipped with mechanically operated shears. These will cut the structural members into short sections for ease of handling and transportation.

Whilst demolition of the existing bridge is going on, abutment works will be carried out on both the east and west ends of the viaduct. New reinforced concrete abutment base slabs will be cast and pre-cast retaining wall units placed to accommodate the new structure.

When the old structure has been completely removed, the new deck can be slid into place from its resting place on top of the temporary piers. Trial slides will be carried out during possessions in advance of the main blockade to test the slide system, which will consist of semi-continuous pulling rams mounted on brackets attached to the deck and the end of the slide tracks. The hydraulic power packs will be coupled up to a central control. This system allows for differential pressure to be applied to the pulling arms for directional control of the new bridge whilst moving into position. Once in place the new deck will be locked into its final position.

And there it shall remain. Will it carry trains over the River Loughor for 160 years like its predecessor? Only time will tell.

SSS – Sub Surface Signalling

12th March 2013

London Underground is 150 years old this year. The first train on the Metropolitan Railway ran between Paddington and Farringdon on 9 January 1863.

Today, the Metropolitan line is one of the four lines that make up the sub-surface railway (SSR), the others being the Circle, District and Hammersmith & City. Although they have been upgraded during the last 150 years, they are still some of the oldest parts of the Tube’s network.

Not surprisingly, with an ageing system, it is difficult to achieve reliability; yet London Underground has the objective to provide not only increased reliability, but also a significant increase in capacity, faster trains and a better service for its customers. It will do this by introducing new state-of-the art trains and a signalling system that enables more frequent services.

Largest signalling contract

Bombardier Transportation was awarded the contract for SSR automatic train control (ATC) signalling upgrade for London Underground in June 2011. The contract, valued at approximately £354 million, is reportedly the largest metro re-signalling contract ever undertaken in the world.

At the heart of the new system is Bombardier’s proven CITYFLO 650 ATC system which uses communication-based train control (CBTC) technology. It is similar to that running successfully on the Metro de Madrid Lines 1 and 6 in Spain, part of one of the busiest networks in Europe where the customer has already noted a 30% increase in passenger carrying capacity with further improvement expected. The same system is also in operation on Shenzhen Metro Line 3 in China, which was delivered in 22 months.

CITYFLO is a moving block system utilising modern radio-based wide area networks to communicate between the control centre and the train. In addition to enabling the system to be installed without interruption to service and to tight timelines, it can provide interoperability with legacy train control systems and can be adapted to accommodate country requirements.

The full scope of the London Underground contract is for the signalling renewal and provision of an ATC system for the four sub- surface lines which carry 1.3 million passengers a day. Together, the lines comprise 40% of the network and carry 25% of the total ridership.

By 2018, Bombardier will equip the 310 km of track line (40 km in tunnels), 113 stations, 191 trainsets, 49 engineering trains and six heritage trains, followed by a two-year warranty period.

New methods – one team

The sheer scale of this project has required London Underground to adapt its processes and requirements to the solution that Bombardier is providing. Matthew Steele, London Underground’s programme delivery manager, explained: “We’ve recognised that we need to be flexible as a customer to enable our suppliers to give us the solutions we need. This is facilitated by our ‘New Engineering Contracts’ (NEC) – a very different way of working – and one that reciprocally incentivises collaboration with our supplier partners.

“The sub-surface railway represents 40% of London Underground’s network. We also have to deal with the age of the system and the need for reliability, which means that we want to ensure that the impact on our customers is kept to a minimum.”

The project teams from LU and Bombardier are co-located one building. Matthew Steele is convinced that this was the correct move to make. “It ensures a spirit of transparency and openness and it helps to integrate all the functions – from the operations team, who understand how the railway operates, to the testing team and through to the maintenance staff who will look after the system down the line.

“There are a lot of inter- dependent projects that all have an impact on each other. So we can’t look at re-signalling, rolling out new trains, or maintaining them as projects in isolation. We have to do all of these things together and recognise that the smallest change can impact upon the other initiatives. We can only deliver if we are monitoring all our interfaces and working collaboratively.”

Minimising risk

“Knowing that London Underground is probably the most complex metro in the world, we ran a comprehensive 18-month selection process before embarking on this project. Bombardier offered a proven product that could deliver the performance that we believe we need. For us it was critically important that the system could be delivered within a challenging timeframe and we gained confidence from the fact that the product is already in use (in Metro de Madrid and Shenzhen).

“Nevertheless, we face different challenges. As well as being a much larger and older system, we have mixed operations such as a shared network with Chiltern Railways and London Overground. It is a complex layout, with junctions – interfacing with the Jubilee and Piccadilly lines. There are, however, similarities, for example, this is a brownfield site and we are reliant on night closure times to test and install the system.”

Measuring success

The project team’s objective is to introduce the full performance of the sub-surface signalling upgrade with minimal closures. Whilst closures will be needed to remodel the key trackwork, disruption to customers will be avoided by applying the fundamental principle of proving the system performance and reliability off-site, both in the factory and at the test track at Old Dalby, before installing it on the railway.

Carrying out testing over the next 18 months at the dedicated 5km Old Dalby test track, near Melton Mowbray in Leicestershire, will ensure that the CITYFLO 650 system completely meets all of London Underground’s requirements. Long term, this will minimise disruption to customers both by reducing the need for closures as well as by proving the reliability and performance before installing on SSR.

“Our objective is to guarantee reliable service on the railway,” Matthew Steele commented. “We will know we have been successful if there is no discernible impact of the upgrade to our customers and when we complete a system that delivers reliability, performance and the customer benefits including the increase in capacity that we defined. We recognise this is no mean feat but we are embracing this challenge to delivery on time and realise the benefit for London.”

Vehicle testing on the GCR

11th March 2013

This article is not a historical reminiscence, although the writer is old enough to remember the Great Central Railway (GCR) running passenger trains from Loughborough to London Marylebone in the early 1960s with a journey time of 2 hours. Not bad for steam engine hauled trains having several stops en route.

Readers of this magazine will almost certainly know a great deal about the GCR. Some may have lived through its run-down and closure which began in 1960 with the withdrawal of the Manchester – London expresses and ended with the last remaining Nottingham – Rugby section closing in 1969.

The closure was much lamented by railway enthusiasts for many reasons, partly because it was the only UK mainline railway built
to an expanded loading gauge capable of accommodating larger continental trains in anticipation of a future Channel Tunnel. This was the dream of GCR’s then chairman and driving force, Sir Edward Watkin, who envisaged a new railway line that could be expanded and linked to the continent via a tunnel. Sadly, the closure of the GCR put paid to that, and with 20-20 hindsight we now realise what a dreadful mistake it was. There may even have been a case for part of the old GCR to take the proposed HS2 from London to near Birmingham.

Following the closure of the Nottingham – Rugby section, a group of enthusiasts got together with the aim of keeping at least part of the line open as a heritage railway. Fund raising was a major problem in the early 1970s and this was only resolved when the local Charnwood Borough Council came to the rescue by purchasing the trackbed and associated lands from Loughborough to Belgrave and Birstall (now Leicester North).

During the last four decades, the expertise and dedication of both volunteers and some highly experienced and qualified staff have transformed what was a struggling little concern into one of the UK’s leading heritage railways. The collection of restored stations, signal boxes, carriages, wagons and steam and diesel locomotives are also a tribute to the hard work of those involved.

From 25 to 60 mph

Her Majesty’s Railway Inspectorate (HMRI – now the Office of Rail Regulation or ORR)
did not normally permit a heritage or minor railway to operate passenger trains above a speed limit of 25mph as laid down in the Light Railways Act 1896. This speed limit initially prevailed on the GCR. However in 2001, senior officers at GCR realised that there was a business need to utilise their infrastructure to provide a facility for established and potential operators which wanted to carry out testing of railway vehicles and associated components without interference on days when heritage trains were not running.

An application was made to HMRI for a derogation to run trains at up to 60mph to enable such testing to be undertaken. It
was laid down by HMRI that, to permit such running, there should be no public access to the railway, a full track survey would have to be undertaken and appropriate remedial work carried out, GCR should appoint a competent Permanent Way Engineer and a full risk assessment should be drawn up by GCR staff and approved by HMRI.

All these requirements were met and derogation was granted in 2002 which allowed testing at 60mph in perpetuity.

The upgrade from 60 to 75mph running

For many years, brake tests on freight wagons were carried out on the national network, latterly between Crewe and Winsford. Up until 1993, this testing was carried out free of charge to the operator. However, with the run up to privatisation and with track access charges/traction hire/traincrew/test staff, the cost of a test slot escalated sharply to several thousands of pounds.

Following the derogation for 60mph running, the GCR became the preferred site for brake testing by BR Research. The officers of the company quickly realised there was a further business case for upgrading the test line up to 75mph so that new freight wagons could be tested away from the national network at much lower cost and with a more flexible programme.

HMRI (ORR) laid down conditions before GCR were allowed to run test trains at 75mph. Primarily, ORR had to be satisfied that the permanent way was in a fit condition to accept trains with axle loads up to 25 tons at this speed. To this end, all lines along the GCR route were crack detected. This resulted in some repair and remedial work, after which the track was re-tested to ensure that it was in A1 condition. Interestingly, a high-speed rail crack detection vehicle was flown in especially from the USA to carry out this work and was flown back as soon as it was completed.

Many of the conditions laid down for 60mph running were reviewed for the higher speed derogation and a further full risk assessment was also carried out by GCR staff which was approved by ORR. To accredit their drivers to work at 75mph, GCR selected existing qualified 60mph drivers and ran accreditation sessions with them using a volunteer, who is also a Pendolino driver, and was passed to work trains at speeds up to 125mph.

In order to ensure the safety of the public and those carrying out testing duties, all work is carried out under total possession of the line and nobody is allowed at trackside within the possession limits except for essential testing staff. Along the length of the test track, there are no farm crossings, accommodation or footpath crossings. GCR observe high standards of Health and Safety in what can otherwise be at times a hazardous environment.

The first testing at 75mph took place in 2008 involving brake and slip tests on a WH Davis Super Low 45 wagon. Many tests have been carried out since and, although GCR has to apply for a letter of no objection from ORR each time 75mph testing is carried out, to date there have been no problems.

Advantages of the GCR

One of the major problems faced by owners of any form of rolling stock is the ability to have it tested in the UK. Using Network Rail infrastructure is expensive, takes a long time to organise and usually has to be carried out at the most unsocial of times often in the hours of darkness and in some cases, geographically remote from the point of origin of the vehicles to be tested.

As a private railway, the GCR can offer testing facilities at any reasonable time usually within a few days of the first contact. It is located in the East Midlands just a few minutes from Junction 23 of the MI. The railway is eight miles long with five and a half miles of double track. It has gentle curves and shallow gradients (maximum of 1 in 176) and axle loading is the maximum permitted in the UK at 25 tonnes. Access is by road only at present usually at Quorn, three miles south of Loughborough, via a large yard where there is ample room to set up a project base. There are, however, well advanced plans to develop rail access to the national network at Loughborough on the Midland Main Line. The GCR has four stations, a sixty foot turntable, maintenance sheds and one of the finest mechanical signalling schemes in the heritage arena.

Having gained approval to test at 75 mph, GCR has accumulated an impressive list of clients including Network Rail, Balfour Beatty, Amey, Serco, Brush Traction and various overseas organisations. Testing has included mileage accumulation (1000 km in 2 days), braking tests including slip tests at 75mph and noise acceptance trials. The latter was particularly useful to WH Davis back in 2008 when their new Super Low 45 wagon became subject to the requirements of the full EU Technical Standards for Interoperability (TSI).

Noise testing

Within the environmental section of the TSI is a requirement for any new vehicle to pass certain parameters in regard to noise generation. At the time, there was no private test track in the UK able to carry out these tests, so Network Rail and GCR jointly set up a noise testing facility. Had this not happened the WH Davis wagon would have had to be transported, at considerable cost, to either Switzerland or Germany or Poland or the Czech Republic for testing which would have resulted in enormous delays in the approval process.

Noise testing is carried out on a specially prepared stretch of continuously welded rail approximately one quarter of a mile long. Noise detection equipment provided by Network Rail stands in a ‘free field’ site, i.e. a location out in the country with minimum external noise sources. As both sides of the vehicle have to be tested, it is turned around on the 60ft turntable that was gifted to GCR by the National Railway Museum and which is located at Quorn.

Brake and slip testing has been carried out in conjunction with disc brake manufacturers so that essential coefficient of friction characteristics can be collated for various compounds used in disc pad manufacture. Tests involving the intentional modification of the wheel/rail interface have been undertaken, examining the effect of different railhead conditions and quantifying measures that can be taken to combat lack of adhesion.

New (old) locomotives

One particularly interesting piece of testing, especially to steam enthusiasts, involved
the Peppercorn A1 Pacific steam locomotive 60163 Tornado. Trials required assessment of wheel impact and loads on the infrastructure, both for the identification of wheelset defects and acceptability of new locos in terms of vertical and horizontal forces. These trials were carried out whilst Tornado was at the GCR for acceptance and running in tests.

GCR have an ongoing training partnership with Vital Rail and others, providing a facility where permanent way trainees can learn their craft ‘hands-on’. Apprentices can get ballast on their boots and receive lessons in track maintenance, inspection or design. Washing and messing facilities are available on site.

GCR has also helped organisations that have required their staff to have realistic driving and operating experience. The four stations provide opportunity to learn braking and control of both light engine and braked trains so as to achieve the correct stopping points. For theory work, classroom facilities are provided and the inner man is catered for by on-site cafes and restaurants providing everything from coffee and biscuits to full meals. Conference rooms are also available for larger or specialist groups.

What does the future hold?

At the time of writing, the other two test tracks in the UK are also fairly busy. Network Rail’s own site at High Marnham has a lower speed limit than the GCR and is also used for testing on-track machinery, while the nearby track at Old Dalby (just a few miles from Loughborough), where the Virgin Pendolinos were commissioned, is now operated by London Underground testing both new
trains and a new signalling system. With the excellent facilities that GCR can offer other customers for both vehicles to be tested and project support staff, their future looks bright.

Resignalling the Victoria Line

8th March 2013

Much has been written about the excellent way in which public transport performed during the 2012 London Olympic Games. This was due to detailed planning and to making sure that major improvement projects by both London Underground and Network Rail were completed in advance of the competitors and spectators arriving.

The Rail Engineer has looked at several of those projects. One that it has not was the commissioning by Invensys Rail of the seventh and final asset replacement stage of the Victoria Line Upgrade (VLU) Project, marking the completion of a challenging nine year programme.

Invensys delivered the upgrade in partnership with London Underground (LU) and Bombardier Transportation, the programme seeing the replacement of all the Victoria Line’s rolling stock and signalling and ultimately providing improved headways and journey times. The upgrade programme has delivered a ‘30 trains per hour’ service, providing passengers with faster, more reliable and more comfortable journeys, with week day peak services increasing from 28 to 30 trains per hour and off peak services from 23 to 24 trains per hour.

Overlaying the new system

A little over 13 miles long, the Victoria Line was originally opened in four sections between 1968 and 1972. The line is predominantly formed of a deep level tube tunnel which serves 16 stations with a fleet of 43 trains (37 of which are in service at peak hours).

The design and installation teams for the VLU programme therefore faced a number of significant challenges, the project representing a first for LU in that it required migration from one Automatic Train Operation (ATO) system to another, with Invensys Rail’s Distance to Go-Radio (DTG-R) trackside equipment being overlaid on to the legacy signalling system, transmitting both the new radio messages and legacy track circuit codes during the migration period for the new rolling stock fleets.

Train detection, interlocking and point detection and control continued to be delivered by the legacy signalling system, which also switched and transmitted the legacy Automatic Train Control (ATC) track circuit codes to the 1967 stock trains. Invensys delivered new ATO and Automatic Train Protection (ATP) solutions which were overlaid onto the existing infrastructure and which enabled mixed operation of the original 1967 fleet and new rolling stock. The overlay solution allowed the first of the 47 new Bombardier 09TS trains to start running on the live passenger-carrying railway three years ahead of the final project completion, minimising service disruption throughout the project.

The ATP system provides train protection for over-speed; driving limit enforcement (end of authority) and protection limit enforcement (limit of movement authority), while the ATO

provides automatic driving functionality for control within driving limits, speed and distance; signal stopping and auto-restarting; platform stopping (to within +/- 1 metre of the actual stopping mark) as well as the potential for automatic door opening.

The new 09TS fleet began to enter service in January 2010 and has already accumulated over 10.2 million kilometres of passenger operation. As part of the migration stage, the new Signalling Centre at Osbourne House also took control of the legacy interlockings and the legacy control room, with the control centre commencing continuous operations in January 2011.

Removing the legacy

An asset replacement programme was undertaken by Invensys after the last of the 1967 stock was withdrawn. Over 15 months and seven stage commissionings, the company successfully removed the last of the legacy signalling equipment and installed new WESTLED signals, FS2550 track circuits and a full range of platform equipment. The company’s WESTRACE solution now controls the entire line which is split into 16 interlockings, linked to the signalling control system.

The final stage was delivered over a 27-hour weekend closure in July and saw the commissioning of bi-directional signalling between Seven Sisters and Northumberland Park Depot. New control centre operations were also installed, together with an upgraded version of DTG-R train data, which provides full functionality for control of the entire Victoria Line.

“Migration to the new signalling system presented many challenges, both technical and operational. Keeping the railway running whilst the signalling system was being replaced required a realistic and realisable migration plan, while recognising the constraints on access to the railway. Throughout the project, the Victoria Line remained operational during the day. Access was generally limited to three extended nights per week, plus a number of weekend shutdowns, limiting disruption to passengers and ensuring a smooth transition from the legacy to the new system”, said Invensys Rail’s delivery director, Matt Kent.

“This has been one of the longest, most complex and most challenging projects we have undertaken, but the result is a railway which is delivering significantly improved capacity, performance and reliability for London Underground and its passengers, as well as a greatly improved service for the increasing number of people using the line.”