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Importance of BIM to the precast concrete work of London Bridge

 

30 September 2014 Sourse: www.waldeckconsulting.com

Waldeck’s BIM Technician Amy Cheeseman explains the importance of Building Information Modelling (BIM) to assist in the design of the platform structure in precast concrete units for FP McCann as part of London Bridge station’s redevelopment.

Due to the layout of the platforms and the speed of the erection programme, precast concrete was the best solution for the structure.

At the start of the project, Waldeck was provided with a large package of site co-ordinated models in DGN format.

Being able to have 3D models of the in-situ concrete foundations and platform finishes allowed us to design a series of standard unit types, which can be adapted across the entire station and minimise the number of different moulds required by FP McCann.

Concrete challenges

The design of the main unit type was our first challenge to overcome, needing to be self-supporting and as large as possible, while coming under the maximum lift of 6.3 tonnes.

This led us to design a concrete ‘table’ with two full-height legs and two short legs, which sit on a standardised kerb unit. These two units create 2.8 m of platform with minimal grouting for fast onsite erection.

“The success of the project so far would not have been possible without the use of BIM across the entire project team”

By far the biggest challenge has been making allowance for the other design packages without compromising the integrity of our own precast. All of our units were designed around the steelwork canopies’ 15 m column centres.

However, we also had to take into account all of the services that are integral to modern railway stations.

Again, being a BIM project aided our design, allowing us to physically see where all the services were in 3D.

Co-ordinating change

For example, we were able to detail our units to avoid putting loading onto pipes and, where it was unavoidable, provide a solution to suit both ourselves and the drainage designers.

Drainage outlets and access holes are at regular centres across all of the platforms, which did not always land in a suitable place in our units.

Co-ordination with the other members of the project team allowed us to adjust these locations to make sure there was always sufficient concrete around penetrations to provide a strong precast structure.

We have provided precast in channels for cable trays and other M&E services, locating these using the models provided, thus avoiding post-fixing these support systems and decreasing installation times.

To date, Waldeck has produced approximately 1,600 precast concrete elements across six platforms, with a further nine platforms to deliver.

Overall, London Bridge has achieved BIM Level 2, enabling the assessment of the constructability, maintenance and co-ordination of drainage and electrical services to the station while resolving issues before they got to site, which in turn enabled a higher level of accuracy and faster site erection.

Without a doubt the success of the project so far would not have been possible without the use of BIM across the entire project team.

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