Replacing beams for the A45 South bridge over the electrified railway
The objective of this major project was to replace the narrow, failing A45 South Bridge road over the busy electrified West Coast Main Line.
The bridge, built in 1837, had weak parapets, sub-standard waterproofing and drainage and was too narrow. Used by 30,000 vehicles a day, it was an important transport link to the many businesses and public amenities in the area including the NEC, Birmingham Airport and the large Jaguar Land Rover plant, so effective programming was essential.
It was the first major project under Solihull Council's UK Central Programme to manage the growth of development in the area. It was vital to improve traffic capacity, reduce congestion, and improve safety.
Collaborative approaches to identifying solutions
Two partnering workshops were undertaken at the start of the A45 South Bridge Replacement Scheme. These ensured that everyone fully understood the project and set expectations of each other from the start.
In addition to the core team of Carillion Civil Engineering Ltd, Designers (WSP) and Solihull MBC and project managers SLC Rail, representatives from Network Rail (NR), Highways Agency, NEC, Birmingham Airport and Warwickshire County Council also attended.
Forming the project team
From this point on a single project team was formed across all parties with shared offices and facilities and a clear demonstration from the respective leaders that through the unsociable hours and challenging work, everyone was in it together.
The strong team cohesion and collaborative approach meant all deadlines were met as well as a one team culture promoting value engineering and innovation.
Close partnership with NR was required to resolve issues throughout the contract. The project team elected to follow the NR risk readiness deliverability review programme to reinforce best practice through the most critical aspect of the project – the demolition of the old bridge.
Planning demolition of the old bridge
A new bridge crossing was needed before the old one could be demolished. That demolition demanded a 54-hour possession of the electrified West Coast Main Line, which was only available over Christmas 2015.
Because the demolition could only happen once traffic was rerouted over the new span it was essential that this first phase of construction be completed ahead of that deadline.
The project was planned with two weeks of time risk before the demolition. The project team used a tightly defined reporting framework to manage risk. By laying out in advance exactly what was to be reported and when, a very fast and efficient process was established for reporting to the project board.
Construction challenges
The project demanded a meticulous approach to planning and delivery. It was essential that large parts of the construction be completed before the Christmas 2015 possession and that traffic remained free flowing throughout.
It was also necessary to work with utility companies to ensure the rerouting of their services and provision of a high pressure gas main over the new span in the time between its completion and the demolition of the old bridge.
Several aspects of the construction and project delivery also required innovative approaches or designs. This included an approach to gradual lowering of the electrified overhead line equipment over several possessions, new approaches to earthworks and piling next to live tracks, and extensive prefabrication of bridge parts to minimise the work required during possessions.
Planning and initiating construction
As space was too constrained to build the new bridge while the original remained the project was designed so that the bridge would be built in two phases. The first span would be built very close to the old bridge, with traffic diverted onto the new span, followed by demolition of the old bridge. The second span would be built adjoining the first to provide a single deck.
Earthworks were installed using a TerraTrel reinforced earth system adjacent to the bridge enabling excavation following bridge demolition to be made tight against the adjacent carriageway.
Compared with traditional sheet piles and soil nails this reduced time, cost, and the risk of service strikes. A short height high torque piling rig was used to construct the bored piles for the abutments. This enabled their construction next to live rail lines, reducing night time possession working.
Overhead line equipment (OLE) modifications were required. Due to resource constraints NR were unable to carry these out. In conjunction with Carillion's in-house OLE team they designed an approach which allowed bridge construction alongside OLE works. This included shortening masts, installing new cantilevers and re-profiling OLE equipment along one mile of track over 12 eight-hour possessions.
Diversions and possessions during construction
Effective coordination meetings held throughout the project ensured that all utility mains were diverted in time for the Christmas 2015 possession.
If not diverted, they could have potentially delayed the project by 12 months causing major congestion in the area. This included negotiating with the service owners to divert mains onto the nearby North Bridge. Large diameter sleeves were installed to allow for future utility mains as part of the significant managed growth of development in the area.
Prefabricated bridge beams were delivered to the compound in advance. Braced pairs had the permanent formwork and temporary parapet installed while still on the ground avoiding working at height over railway and possession working at night.
In total 45 weekend possessions were required with none being handed back late or incurring train delays.
The project was planned to the smallest detail with a tightly defined reporting framework to manage risk. The works were all completed ahead of schedule and the possession was handed back 17 hours early.
Bridge replacement social benefits
The bridge is located immediately between the M42 and Birmingham Airport. It carries the major volume of the road traffic into the airport plus a large volume of commuter traffic and visitors to the NEC.
At the outset of the project the route was already heavily trafficked with westbound average daily flows of 28-30,000 vehicles and significant peaks in excess of this when major events are held at the NEC.
The economic assets served directly by the bridge are estimated to generate GDP in excess of £2.5bn and support over 80,000 jobs.
The project team working in close collaboration with all parties met all milestones to deliver the bridge ahead of schedule.
Traffic from the M42 to the airport now has a dedicated slip lane, quality of life has improved for the road users through less congestion and new walking and cycle routes over the bridge have made sustainable travel choices more attractive for local people.
During the project and at its conclusion feedback from stakeholders was overwhelmingly positive. The very low volume of complaints and the tone of media coverage suggest the travelling public had realistic expectations and were happy with the way the project met their needs.
Project details
Location: Solihull, Birmingham
Value: £12m
Date of completion: 25/09/2016
Duration: Two years
Client: Solihull Metropolitan Borough Council – UK - Central
Contractor: Carillion Civil Engineering
Project manager: SLC Rail
Challenge summary: Removing a serious traffic bottleneck by replacing a narrow, failing road bridge over a busy electrified railway line.
Challenge solution: A collaborative approach through the application of innovative ideas and proactive stakeholder liaison.
Contributors
Derek Phillips, Carillion
