52 Lime street — G&S site visit
On the 3rd of March a successful site visit was organised to the construction site of 52 Lime Street, also known as “Scalpel” by the G&S ICE committee. The site visit was hosted by concrete subcontractor “Byrne Bros”, and delivered by Ben White the Head of Engineering.
Scalpel is neighbouring the Gherkin and is a 36-storey office building in the City of London. Skanska was awarded this £198m contract to build the tower and is responsible for the construction, mechanical and electrical engineering and installation of services within this prestigious new development.
The 190m-tall tower was designed by Kohn Pedersen Fox as a European HQ for US insurer W.R.Berkley. The tower will provide approximately 37,000sqm of office accommodation over 35 office floors, plus shops and restaurants with 2 basement levels.
During the site visit, graduates and students were informed about the progress of works. The completion date is estimated towards the end of 2017 and Skanka is progressing well with the 160-week construction programme.
The superstructure is comprised by a steel composite metal decking slab with concrete topping and steel columns. The ground floor and substructure slabs are concrete with steel encased and in-situ concrete columns. The stability core is concrete and a secant pile wall is built around the perimeter of the building.
As the programme (figure below) is the main driver, a top-down construction method was the preferred chosen, which allowed the basement construction and the steel erection to carry on simultaneously. Early works also included the construction of the main concrete core of the building. Once the concrete core reached half-weight through its total height, at level 17, the steel erection programme kicked off at ground floor.
Ben White stated that Byrne Brother’s job was nearing completion. They dismantled the slipform a few days prior to the site visit. Also, as Scalpel’s main core is offset and positioned along the south elevation, the loads on the building are eccentric. To counteract this, the north elevation and the east and west facades have been built as large perimeter moment frames to add stiffness and the core will be post-tensioned.
The figure below shows the eccentric core at the first floor level.
It is also worth mentioning that because of the building’s inclined northern elevation, floor areas decrease from 1,466m2 on the second floor to 614m2 on level 35, the uppermost office floor. Up to level 21 the building has one row of internal columns, but as the floorplates decrease these are no longer needed and by level 24 there are none.
Steelwork and glazing were the main activities on site the day of the site visit as the photos below show. These activities will be completed by the end of summer.
The site visit was successful and the G&S committee would like to thank Byrne Brothers, one of the UK’s premier concrete contractors and especially Ben White for the time and effort he devoted. The site visit was organised by Stratos Gavotsis, the site visit coordinator of the G&S ICE committee.
