Celebrating a decade of the Broadgate Framework

If early engagement set the foundation, collaboration became the engine that propelled the project forward. 2FA, like other projects in the Broadgate Framework, has benefited from a deeply integrated working environment. Key partners, including British Land, cost consultants, project managers and major sub-contractors, share a co-located office, making real time decision making both natural and efficient.

Co-location, now a hallmark of the Broadgate approach, means that decisions on logistics, interfaces and temporary works are resolved in real time. Complex interactions between the steel frame, concrete cores and top down construction were successfully navigated because the team had already built years of familiarity, trust and shared ways of working.

This extended to the façade programme, where the 5,738 unit sawtooth façade, with its shifting geometries and diagonal dividers, demanded exceptionally close cooperation between structural and façade teams. The crane grillage, cantilevered off the building façade, was designed to allow façade installation to progress uninterrupted and with millimetre level tolerance, a feat enabled only through this deep integration.

On the concrete side, 2FA has pushed engineering practice in several ways. The concrete frame was delivered by Morrisroe, who incorporated extensive use of GGBS (Ground Granulated Blast-Furnace Slag) as cement replacement across the concrete frame (up to 50% in slabs, composite decks, capping beams and substructure), delivering significant embodied carbon reductions compared to Stage 4 design assumptions.

The simultaneous progression of concrete cores and steel erection was made possible by tower cranes mounted directly on the slipform rigs. This was only the second time such a method has been used in the UK.

Temporary works were led by Robert Bird Group and McAlpine Design Group, who provided specialist engineering input to the temporary works strategy, particularly around coordination with the slipform rig and associated loads.

Complex top down construction beneath the rising superstructure required meticulous sequencing, lightweight formwork solutions, pick and carry cranes and the pressurised pumping of self compacting concrete into deep, constrained shuttering, executed by Morrisroe with precision.

A unique logistical challenge saw a large excavator operating up to two storeys inside the steel frame, enabled through temporary leave outs and careful sequencing by Morrisroe and Hares (supporting temporary works), alongside expert machine control from the plant hire contractor.

Collectively, these innovations reflect the maturity of the engineering capability that has grown across a decade of Broadgate delivery.

The steelwork strategy was shaped by sustainability from the outset. The majority of steel was sourced from electric arc furnaces, including ArcelorMittal’s low carbon XCarb product.

A circular approach saw steel reclaimed from the previous building, carefully dismantled, stored, cut and re fabricated into elements of the new frame, avoiding the carbon impact of melting down and producing new material.

This complements the carbon savings delivered through the GGBS enhanced concrete mix designs, together forming one of the most sustainably engineered major structures in the framework to date.