海角视频

5 Broadgate

London, UK

At approximately 100,000m², 5 Broadgate is one of the largest and most robust and resilient single office buildings in London鈥檚 financial district. It was also an award-winning trailblazer of sustainability principles, representing the dawn of a new shift towards a consciousness around the importance of considering embodied carbon in commercial buildings.

This imposing structure sits on the site previously occupied by 4 and 6 Broadgate, and provides the keystone for the ongoing development for the area. As the new home of UBS, 5 Broadgate houses four trading floors and seven levels of offices and trading support facilities.

Challenge

海角视频 needed to work as part of the project team, collaborating closely with client British Land, Make Architects and the ultimate tenant UBS, to develop a building that is as intuitive to work in as it is impressive to look at. We also needed to consider 5 Broadgate鈥檚 relationship with its busy city centre location, carefully planning public spaces and improving people flow around the area.

This was a highly constrained site beside Liverpool Street Station, a Transport for London bus gyratory and the busy Broadgate Estate service yard that needed to remain accessible at all times. Our engineers had to temporarily prop up the northern edge of Broadgate Circle, a major thoroughfare, during works. There was also a major sewer below the site, along with other subterranean infrastructure that had to be carefully worked around during the construction of the 15-metre-deep basement below the 11-storey new building.

With sustainability a key consideration at every stage, the design team needed to balance the impact of the project alongside the benefits and economic catalyst that the new facility would enable. To support this balance, it was imperative that our teams created a real landmark of sustainability out of this highly engineered and complex building. We also had to design the cladding of the new building so that it plays an integral role in its energy efficiency.

As well as ensuring the building is as energy efficient as possible, our team also had to deliver a commercial office project that is robust and has a high level of protection against fire and blast. It was critical that the UBS trading floor must be capable of continuing trading in any eventuality, and this was given as the benchmark for designing a truly robust and resilient building.

Solution

The solid facade mitigates the effects of solar gain and plays a key part in the project exceeding its own high sustainability targets. Aligning the vision of the architect with this environmental strategy, the simplicity of this shell gives 5 Broadgate a unified, elegant appearance.

Considerations around embodied carbon drove the design, at a time when such sustainability targets were very much in their infancy. Our teams trailblazed this emerging discipline, painstakingly gathering a wealth of data upon which the design should be measured against to assess its embodied carbon footprint.

We produced a whole life carbon model to give the client a high-level perspective of the project鈥檚 carbon impact, from the building鈥檚 construction through to its day-to-day operation. By carrying out 鈥榟ot spot鈥� studies to measure the effectiveness of carbon savings measures, our team was able to save significant quantities of CO2. We achieved this through a range of measures, including reducing the thickness of facade skin, incorporating low carbon concrete, using twin primary beams and using a raft foundation system.

As well as helping to reduce the carbon footprint of the building, the twin beams also achieved the client鈥檚 aim to limit the movement of the building鈥檚 floorplate under footfall whilst working within the highly specific structural requirements of the trading floor 鈥� where line-of-sight obstruction from columns as well as vibration needed to be kept to a minimum.

The highly cost-effective twin beam solution we devised also played a key role in ensuring the blast-proof resilience of the structure. We designed each floor to support its own load, protecting against progressive collapse. The use of the primary beams also meant that the secondary beams span was reduced from 13.5 metres to 12.5 metres, offering significant steel weight savings of 12% across the project. Further seeking to ensure the robustness of the structure, our team carried out a detailed assessment of the building using our in-house bespoke software VULCAN. Specifically developed to predict the behaviour of steel structures when exposed to fire, our use of VULCAN enabled us to ensure the building had a high fire resistance.

Value

The bold and prominent 5 Broadgate building is a catalyst for new development. The sleek stainless-steel facade reflects the prominence of the company that occupies this commercial office space in the heart of London, while also symbolising architectural and engineering precision.

We worked with the wider design team to engineer a clever and carefully considered design that enabled significant sustainability-focused improvements alongside cost savings for the client, while also meeting the exacting requirements of the tenant around resilience and business continuity in any scenario.

By employing a carbon tracking model from the outset the designers ensured that sustainability featured in a quantitative manner thought the design process, influencing decisions on layout, structure, facades and foundations. Thus choices were made on the basis of the best overall outcome, thereby ensuring that efficiencies were balanced. By adopting this approach the designers have shown how a seemingly conventional solution 鈥� albeit one that had to address stringent client requirements 鈥� can be modified in several respects so as to achieve a true optimum and thus to embody the principles of sustainable construction.

Judge鈥檚 comment, The Institution of Structural Engineers Structural Awards 2016