Case Study: London Bridge Station

London Bridge Station

Midland Steel provided an Offsite Modular Rebar solution for the London Bridge Redevelopment which delivered a modern, spacious and fully accessible train station fit for the 21st century. Network Rail described this project as “the most ambitious station redevelopment in a generation”. Costain Group PLC contracted this redevelopment with Midland Steel responsible for the design and prefabrication of all reinforcing steel elements.

Midland Steel’s involvement consisted of developing detail and design of steel reinforcement to allow prefabrication of 24 individual hour-shaped columns and crossheads. The resulting design included 451 bars of which none had the same angle shape or dimension. This was made possible through 3D modelling of the prefabrication solutions, with efficiency and safety at the core of the innovations.

The client required the provision of prefabricated structures which had to be placed in extremely tight time frames and within deadlines coordinated by Network Rail. Our provisions provided all requirements, the reinforcing steel columns were dropped in from the trailer to the final destination and fixed within 45 minutes. Each column weighed approximately 10 tonnes so this task was a key outcome that was only made possible with our prefabricated solutions. The cross heads were installed from trailer to destination within 2 hours. These weighed approximately 20 tonnes each and had to be placed with a tolerance of +/- 5 mm. Our solutions drastically reduced the program time which was needed to meet the client’s requirements.

KEY BUSINESS BENEFITS

• Eliminates approximately 60% of onsite time for installing steel reinforcement
• Approximately £250,000 to £300,000 was saved just on one project, equivalent to approximately 40% of steel by weight
• Delivers specialised solutions and configurations for main contractors, developers and structural engineers through Midland Steel’s Rebar BIM process.
• Midland Steel is able to provide a collaborate data management tool – all information in one platform
• Produces highly detailed as-built Building Information Models: provides the ability to visualise a constructible model of a project and identify problems immediately, allowing them to be solved at that point rather than later onsite.

The distinguishing factor was our experience with the 3D modelling of this project. The model was used in collaboration with the main contractor, Costain and the structural engineer, Hyder WSP providing full transparent information on the design, detail, prefabrication, delivery and construction of the 24 elements provided for the columns, crossheads and pile caps. A seamless process was achieved with no errors onsite allowing program time to be reduced. The entire project was achieved on budget with a substantial cost saving for the client on prelims.

The achievement of fabricating these products to such precise tolerance indicated the value of the 3D model. The project consisted of no welding as everything was stainless steel wire tied. Transport from Mountmellick to London provided a major challenge which was overcome with diligent planning and verification. The logistic tolerances of less than 20mm on some bridge structures on the journey were successfully managed which was a massive achievement. These low loaders were transporting a massive structure on the verge of the limit in transporting something of this size and over such a distance. And, as always, our health and safety policies were at the core of all practices taken.

BIM BENEFITS ON THIS PROJECT

By effectively using BIM, Midland Steel has proven to reduce formwork labour cost by 20%, efficiency on rebar fixing on-site by 60% and costs overall by 25%. Tony explains: “In the past, you can have a fixer foreman who spends 85% of their time inside an office; reading the drawings and relaying that information – they are just directing 15% of their time into actual physical labour. Now by using 3D model information from Tekla, they are able to move around the site with an iPad and read the elements they are about to fix, therefore becoming significantly more productive. The progression of using Tekla 3D imagery, scheduling internally, fabricating internally, and dropping prefab rebar elements on the site has improved the overall efficiency on-site by approximately 50-60%.

Modelling and visualizing the concrete using Midland Steel’s Rebar BIM Process enables accurate assessments of the area of formwork required. Having this knowledge allows for the precise ordering of materials, as well as the exact planning of where formwork can be reused and scheduled – this is value engineering deriving from having the accurate quantities and dimensions of the concrete model. In addition, the 3D model reduces the likelihood of unforeseen errors onsite, preventing the requirement for additional labour to rectify mistakes.