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Extensive temporary steelwork props up MRI scanner in City of London

A tricky office-to-health conversion saw Paragon use large amounts of temporary steelwork to prop up the installation of a large MRI scanner.

Project: King William Street office conversion
Client: Fortius Clinic
Main contractor: Paragon, part of Interserve
Structural engineer: Conisbee
Architect: TP Bennett
MEP consultant: Hoare Lea

The majority of buildings in the City of London are offices, which in comparison to medical facilities are fairly straightforward to fit out and have established processes in place.

Paragon recently delivered a new state-of-the-art facility in the City for the UK’s leading orthopaedic and sports injury clinic, Fortius Clinic, which wanted to expand its London presence and target a more city-based audience. Located on King William Street, the new clinic required nine consulting rooms, treatment rooms, a pain management centre, ultrasound facilities, an X-ray suite and an MRI scanner.

Paragon delivered 12,000 sq ft of refurbished space across two floors of an office building, which was occupied throughout; this posed a few challenges to the project team and required a great deal of temporary steelwork to achieve the required solution.

Temporary steelwork

Paragon worked closely with structural engineer Conisbee, who designed the temporary steelwork for the installation of the £1m, 8-tonne MRI scanner.

None of the access points to the building were large enough for the scanner, so a telescopic crane was used to lift the MRI unit over the surrounding buildings and it was lowered through an 11-storey existing rear lightwell with tolerances of only 500 mm.

The MRI unit was then trafficked all the way back across the ground floor to its final location at the front of the building.

Fortius Clinic Paragon 5

Fortius Clinic Paragon 5

The 8-tonne MRI scanner had to be lifted over surrounding buildings and lowered through an 11-storey rear lightwell

Here, the walls were lined with Faraday caging in line with medical regulations and added a secondary reinforced concrete slab to support the MRI scanner in its permanent position.

Temporary steelworks were needed to reinforce the floor slab that the heavy MRI scanner was transported across.

The installation required the closure of King William Street, which Paragon scheduled over a weekend to minimise disruption.

To add to this, the team’s biggest challenge was that the crane required to lift the MRI unit was only available for one day and so the installation of the complex temporary steelwork had to be fitted to programme with no room for error.

MRI move

After considering a number of options to move the MRI unit across the floor, including pneumatically assisted ‘skids’, it was agreed that the most practical solution was to use a more traditional roller system.

The suspended ground floor slab had a thin 125 mm top slab supported by a ribbed slab spanning 9 m. Unfortunately, the concentrated loads under the rollers would have been too much for the thin top slab to withstand, so a reinforced trackway was required to distribute the loads.

Steel works illustration

Steel works illustration

The most practical solution when moving the MRI scanner across the floor was to use a traditional roller system

The custom-designed steel trackway was built up from 12 steel 203 x 203 Universal Column sections fixed side-by-side, alongside a steel trackway with plywood decking.

“The resulting temporary steelworks system required approximately 40 tonnes of steel in the reinforced trackway and a further 20 tonnes of complex bridging and propping steel in the basement below”

Following in-situ investigations of the reinforcement in the concrete ribs, it was realised that they didn’t have sufficient capacity to support the MRI unit during its journey across the floor. The tight headroom restrictions at ground floor level also meant there was not enough room for a reinforced trackway system to span the 9 m between structural grids.

As a result, a series of steel props were installed in the basement between the basement slab and the downstand beams to provide additional support to the lower ground floor. The props were used in conjunction with the trackways, which were lined up above.

This additional temporary propping system had to be designed around the existing floor-to-ceiling plant units and services to ensure that they remained uninterrupted and still accessible if needed.

The resulting temporary steelworks system required approximately 40 tonnes of steel in the reinforced trackway and a further 20 tonnes of complex bridging and propping steel in the basement below.

It was a meticulous and well-executed exercise that required intensive planning and attention to detail that ultimately resulted in the successful installation of the MRI scanner.

Connecting floors

The installation of a new feature staircase, designed by Clifford Chapman, also posed a challenge to the team.

Fortius Clinic Paragon 4

Fortius Clinic Paragon 4

An opening was created in the ground floor slab in reception to facilitate the installation of the staircase

The existing building is a 1980s construction with a reinforced concrete frame, and the clinic space covers the lower two floors.

The team created an opening in the ground floor slab to facilitate the installation of the staircase, which runs from the new 1,000 sq ft reception area down to the rest of the clinic on the lower ground floor. This required co-ordinated, controlled breaking to preserve the rest of the floor slab and to protect the one below.

“The team was able to recycle much of the temporary works steel for use on another Fortius Clinic project in the West End of London”

Managing and de-risking this process was a priority, particularly because the other floors of the building and neighbouring buildings were occupied throughout the process. Noise and vibrations were reduced during the work as much as possible by employing alternative methods of builders’ work and sequencing.

Constrained site

The site itself was extremely constrained with only two access points to the building: double doors at the front and an access staircase at the back with a very small goods lift. The team explored using a hoist in the slab opening, but it was too difficult to install and the access was just too limited.

“Another key focus throughout the project was reducing as much waste as possible to minimise the environmental impact of the work”

Meticulous scheduling and logistics came into play on many aspects of the project, and this was especially important for fitting out the equipment, including the MRI scanner.

Another key focus throughout the project was reducing as much waste as possible to minimise the environmental impact of the work.

While the majority of temporary steelwork is custom-designed and unique to each project, in this particular case the team was able to recycle much of the temporary works steel for use on another Fortius Clinic project in the West End of London.

The whole project team worked closely together throughout the project, which enabled it to be completed on time and to budget.

The final completed space, which was designed by TP Bennett, has provided a welcoming and accessible clinic in the heart of London.

Seb Bryce is a project director at Paragon, part of Interserve

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