A sound investment for UBS
At approximately 100,000 m2, 5 Broadgate is one of the largest single office buildings in London’s financial district.
This imposing structure sits on the site previously occupied by 4 and 6 Broadgate, and will 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.
BuroHappold Engineering needed to work as part of the project team, collaborating closely with UBS’s own design advisers, 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’s relationship with its built up city centre location, carefully planning public spaces and improving people flow around the area.
With sustainability a key concern, our engineers also needed to consider the environmental impact of demolishing two existing 1980’s office blocks. We also had to design the cladding of the new building so that it plays and 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 project that is robust and has a high level of protection against fire.
The solid facade mitigates the effects of solar gain and through this exceeding the high sustainability targets that were set for the project. Aligning the vision of the architect with this environmental strategy, the simplicity of this shell gives 5 Broadgate a unified, elegant appearance.
To ensure that embodied carbon produced was kept to a minimum, our engineers assessed all sources of carbon emissions throughout the project. We produced a whole life carbon model to give the client a high-level perspective of the project’s carbon footprint, from the building’s construction through to its day-to-day running. By carrying out ‘hot spot’ studies to measure the effectiveness of carbon savings measures, our team was able to save over 3300 tones of CO2. We achieved this by 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’s aim to limit the movement of the building’s floorplate under footfall. Additionally, we designed each floor to support its own load. These solutions combined contributed to the robustness of the structure, protecting it 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. Our assessments demonstrated that the fire resistance period could be downgraded from the standard 90 minutes to 75 minutes.
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 – albeit one that had to address stringent client requirements – can be modified in several respects so as to achieve a true optimum and thus to embody the principles of sustainable construction.
Judge’s comment, The Institution of Structural Engineers Structural Awards 2016
The bold and prominent 5 Broadgate building is a catalyst for new development. The stainless steel facade reflects the nature of the company that occupy the space, while also symbolising architectural and engineering precision.
Services and approach
When we integrate our specialist teams around an approach, the benefits to the client multiply