- Project Major Project construction of Gotham City at Leadenhall Street
- Principal Contractor Mace
- Sub Contractor AJ Morrisroe
- Principal Designer for propping scheme McCormack Stockwell Young Structural Engineers and Kingscote Design Ltd
- Project Lead Andrew Sharp, Major Projects Manager
- Lead Engineer Stephen Barker, Chief Engineer
- Key Benefit Limited obstruction for access and construction works
40 Leadenhall Street is a 900,000 sq ft office-led development located within the City of London Financial District. The development site, known as the Leadenhall Triangle is situated within the Aldgate Ward in the Eastern portion of the City. From initial discussions with the Morrisroe Project team the stringent design criteria for deflection and stiffness for the temporary propping, together with maximising working room soon became apparent. This was further exasperated with the proposed fast-tracked programme and complicated excavation and build sequence. The proposal was to blend bottom-up construction within the Sheet Piled Core Cofferdams and partial top-down construction of the main basement areas to achieve the critical path for construction of the permanent works.
Andrew Sharp, National Major Projects Manager
Introduction
Taking inspiration from the DC Universe series is something that has been done many times – but not in this capacity! In central London, construction of 14-storey and 34-storey towers to the north and south of the site, overlooking the city to create a building that emulates the world renowned three blades of Batman’s gloves is taking place on Leadenhall Street.
On the edge of London’s ‘square mile’ financial district, M&G Prudential have commissioned the construction of an architecturally significant office complex that, once complete, will be an impressive addition to the iconic London skyline.
Leadenhall Street has been a demonstration of the capabilities of multi-business, multi-disciplinary collaboration and early engagement. With the majority of the tender and design process taking place during the peak of the Covid-19 pandemic, remote working and online software collaboration allowed the MGF team to continually develop our design in collaboration with AJ Morrisroe and McCormack Stockwell Young to meet the clients requirements.
The Solution
Through the use of technology, we have been able to work collaboratively: within a central BIM model enabling all contractors involved to visualise the project through 3D modelling and regular video conferencing updates meaning all businesses on site were able to progress despite the lockdown restrictions.
MGF’s involvement in the scheme was not a decision we took lightly. The complex engineering required for the interlinked north and south core cofferdams and north and south basement put an immense pressure on both MGF’s design and manufacturing teams to ensure that our modular and bespoke equipment would be suitable for the works.
Our South East Key Account Manager, Martin Smyrl was a champion of our involvement through his existing strong relationship with the Morrisroe team. Our experience of delivering prestigious schemes in addition to supplying their day-to-day core requirements over many years has resulted in a strong and reliant relationship that confidently works in perfect harmony. Morrisroe’s experience and confidence in our ability to blend a combination of highly bespoke manufactured items with modular equipment using wholly in house resources with commercial and technical management of an evolving workspace is a testament to our Major Projects team.
Despite the fierce competition, MGF were lucky enough to win the contract and began supplying the excavation works mid-2020.
From the onset of the project it was a pleasure as always to work with such a competent and experienced site team – Nick Gilmore, Brian Connolly and Danny Sullivan are great to work with on such prestigious projects.
Martin Smyrl, South East Key Account Manager
With the footprint of the building totalling 900,000sq/ft, the work was split into four sections, the north and south core cofferdams and the north and south basements. Each had to be designed to support the depths of the excavation within, but with the additional factors of the other 3 excavations as surrounding complications. Below the office floors, the excavations are designed to house a 3-storey basement with a mix of underground car parking as well as the server and control rooms for the businesses above.
Excavating to 15m at the deepest part, we supplied a total of 70 250t and 350t hydraulics with combinations of 400, 600 and 1000 series and 450 linear meters of 406 UC braces modular waling beams. MGF’s ability to bespoke manufacture various lengths of our modular, standard range of equipment meant that the site teams could manoeuvre the props around the site avoiding the concrete plunge columns and allowing construction of the basement floor above the prop network.
The Verdict
The complex geometry caused by the interface between the secant and sheet piling meant that the use of purely modular equipment would require multiple props to provide the required support around corners.
Our bespoke manufacturing enabled maximum spacing within the excavation by providing structural continuity around the corners so that fewer props were required.
The project was extremely challenging, it brought together a combination of high loading, strict deflection limits, complex geometry, and a complex construction sequence. Having the capability to design and manufacture complex bespoke steelwork allowed us to provide an efficient solution that reduced the number of props required across the basement giving the contractor much more working space.
Stephen Barker, Chief Engineer
The complex layout of the site, paired with the limited access placed further stresses on the MGF equipment.
Our confidence that our products and design work would sit within the 15mm movement allowance from Morrisroe stems from working from calculated principles and analytical theories of how the ground and equipment should behave.
If we need anything, MGF are always there – from designs to kit to on site support. I can’t speak highly enough of them, hopefully the next job will be as easy as this and we hope to work with MGF again in the future!
Danny Sullivan, Construction Manager at AJ Morrisroe
With basements become ever deeper and more complex MGF’s engineering ability and product capabilities are regularly tested and pushed to the extreme.
With extensive knowledge and experience of basement construction MGF’s Major Projects team have the engineering expertise to provide innovative solutions that continually exceed expectations.
We look forward to seeing the finished product in late 2023.
