We were specifically engaged by the main contractor SDC because of our ability to pre-fabricate as much of the light steel infill walls and associated steelwork as possible, in order to minimise personnel on site and to speed up the overall construction process. The double height infill walls between the 1st to 3rd floor were manufactured offsite at our Wolverhampton factory and were installed as large panels of 8.2m height and up to 2.4m width. The panels were pre-boarded to provide a weather-tight envelope to which the cladding rails were later attached. The curved façades at the corners of the building were constructed using facetted narrow infill walls to create the curved appearance.
Project Delivery
The 450mm, deep post-tensioned concrete slab and concrete frame were constructed first and we had to carry out a site survey of finished slab levels in order to be able to fit in the large infill wall panels, with the required 20mm provision for long term movement with only 5mm tolerance. The over-sail infill walls were connected to the 2nd floor slab by 4mm thick galvanized U sections bolted to horizontal cast-in channels in the slab The single storey high walls at ground floor were a more conventional ‘stick built’ infill wall.
We were also engaged to provide a ‘package’ of steel components, including the Rectangular Hollow Section posts and curved steelwork and infills at parapet level, and the two 8m high tubular steel flue towers at roof level. These structures were pre-fabricated and installed with their cladding and flues attached and anchored to the slab upstands by 4 holding down bolts at each tubular column. Finally, we also responsible for the manufacture and installation of the infill walls to the roof-top plant rooms.
Challenges & Solutions
This project posed many manufacturing, logistical and constructional challenges but was completed on time and on budget leading to provision of a new much-needed high class medical facility to meet the challenges of this and future pandemics. It was refreshing working with the main contractor, SDC, who have fully embraced LGSF and all its benefits and we look forward to working with them on similar projects using the same manufacturing and installation system, which were heralded as a huge success on this scheme.
Construction Details
Construction started on the south west ‘wing’ of the building in January 2020 and our infill wall panel installation ran from May to October. The site team then moved to the north east ‘wing’, which was completed later and the weather-tight building envelope was handed over to the main contractor in December 2020.
Our work started with the ground floor infill walls but the major innovation was in the delivery and installation of double- and triple storey high pre-boarded infill walls. The 2-storey high panels were 8.2m high and up to 2.4m wide and weighed up to 800kg and the narrower 3 storey panels were 12m high. They had to fit exactly between the projecting 1st and 3rd floors and to allow for 20mm long term relative movement with the post-tensioned concrete frame. This meant a careful site survey of as-built slab levels and coordination with the manufacturing team in Wolverhampton before installation with a permitted tolerance of +/-5mm.
The large wall panels used 150mm deep x 1.2mm thick C sections generally with noggins at one-third length positions to maintain the dimensional accuracy of the panels. Next to the large window openings, pairs of 150 x 2mm C sections were used that were connected to the 2nd floor slab edge using specially made galvanised U-shaped brackets with wedge-shaped bolts fitting into cast-in channels in the slab edge. A single screw to the brackets provided temporary vertical restraint whilst allowing for construction tolerances at the slab edge, and two screws in slotted holes provided permanent lateral restraint whilst allowing for 10mm differential movement at the 2nd floor.
Application Benefits
- Pre-fabricated double storey height infill wall panels speed up installation
- 8m high tubular steel frames for flues at roof level fabricated and installed by Metek
- 3m high parapet walls and posts fabricated and installed by Metek
- Infill walls support large metallic cladding panels
- Metek’s package included fabricated steel and curved members for parapet
- Accurate quality-controlled construction
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It was very enjoyable to work with Metek’s team with the development of this product. It was only made possible due to Metek’s innovative culture and willingness to develop this technology for our scheme. Perhaps the biggest testament to its success is the fact we are using this solution again on a subsequent project, implementing the lessons learned on Atria to further enhance the programme, safety and quality benefits of using this solution.
