How do we address the particular issues inherent in tall structures? This question was addressed by a panel of experts at a conference hosted by Architecture Today with Kingspan, The Concrete Centre and Polypipe.

Conference Speakers

Jenny Burridge
Head of Structural Engineering, The Concrete Centre
Damian Farrell
Regional Director, Polypipe
Dr Thomas Henriksen
Technical Director, Kingspan Facades
Jane Richards
Head of Discipline, Structures, WSP
Lee Polisano
Founding Partner & President, PLP/Architecture
Andrew Waugh
Founding Director, Waugh Thistleton Architects

Tall structures are arousing a great deal of interest, not least because building upwards seems to offer the most viable way to accommodate the expansion of cities around the world. Last year New London Architecture compiled planning statistics for new buildings of above 20 storeys in London, finding that more than 500 were either in planning, approved or under construction. Architecture Today’s half-day conference at London’s Building Centre brought together six speakers, from manufacturing, architecture and engineering, to offer views on the subject.

Thomas Henriksen, technical director of Kingspan Facades, opened the conference by asking three questions: How will the new demands for low-energy buildings require innovative facade solutions? What are the future solutions for today’s architectural demands and the ever-evolving facade solutions? And how can safety prerequisites be achieved in an energy-efficient way?

Kingspan’s Dri-Design Flat facade cassettes were used at SCB’s Parkview West in Chicago

Kingspan Facades, a new division of the company, has been set up specifically in response to the pressing challenges of combining energy efficiency with safety. Henriksen argued that solutions need to be developed that can provide exemplary energy performance, A-class fire rating, damp prevention and acoustic performance.

Kingspan itself is focusing on unitised solutions, and in 2020 plans to introduce a new fibre-free, insulating core with an A-class rating that it believes has the potential to change the way facades are designed. Facade technologies are being developed that incorporate sensors that continually monitor the performance of the buildings, and Henkriksen anticipates that these new dynamic materials and components will require integrated and factory-applied systems.

Damian Farrell, regional director at Polypipe Building Services, the plastic piping systems manufacturer that embraces solutions for air, water and ventilation, reported that the company is currently waiting on 33 patents and designs to come to fruition, many of which will allow it to add innovative new products to its product ranges.

Polypipe Building Services’ Terrain Positive Air Pressure Attenuator system is designed to prevent traps failing in high-rise buildings

Farrell suggested that offsite fabrication can help to mitigate some of the issues around the current skills gap in construction, for example in the production of fabricated drainage stacks and bespoke fittings. At Broadway Malyan’s St George Wharf Tower in London’s Vauxhall, the UK’s tallest residential building, Polypipe Building Services designed in a fully-locked rail system.

The Terrain PAPA (Positive Air Pressure Attenuator) system is an innovative solution to the secondary venting of soil stacks. Designed to prevent traps failing in high-rise buildings, it can replace extensive ventilation stacks. Used in combination with the Terrain Pleura Valve it can also reduce the use of rooftop venting, which is particularly useful for green roofs, for example at Vauxhall Sky Gardens and the Landmark Pinnacle, Squire & Partners’ residential tower under construction at London’s Canary Wharf.

Engineer WSP employed viscous dampers to counter high seismic forces at the Zeidler Grinnell Partnership’s Torre Mayor in Mexico City

Jane Richards, director of building structures at WSP, discussed the structural challenges in creating tall buildings. In structures of around 60 storeys and more, damping has to be added to reduce the potentially damaging effect of wind loads. Damping systems effectively absorb energy and thereby reduce the dynamic response.

A common type is the tuned mass damper – typically a weight that is supported by a pendulum arrangement at the top of the building – which sways in an opposite motion to the building and is tuned by matching the mass to counter the predicted wind load. Another damper type is the tuned slosh damper, effectively a partially-filled water tank installed at the top of the building that absorbs vibration energy.

Viscous dampers can be placed within the structure itself so that the viscosity of the fluid within the damper helps absorb the energy of the dynamic motion. At Torre Mayor, Mexico City, this was used to resist the potentially very high seismic forces, and since its completion the building has weathered an 8.1 magnitude earthquake without significant damage.

22 Bishopsgate, London, by PLP Architecture 

Jenny Burridge, head of structural engineering at The Concrete Centre, examined the range of different concrete structural approaches that tend to be employed for tall buildings. In the shear wall system, the typical framing system adopted in the UK, stability is provided by the core which acts as a cantilever. Depending on the size of the core and the slenderness of the building the system can be viable for up to 40 storeys.

The tube-in-tube system, appropriate for buildings of up to about 70 storeys, relies on a combination of the core and the perimeter to provide stability. The outrigger braced system, which can be used up to and above 100 storeys, combines the core and perimeter tubes with outriggers that stiffly connect the two systems at levels up the building to further enhance stability.

Currently the tallest purely residential building in the world is 432 Park Avenue, New York, designed by Rafael Viñoly and engineered by WSP. The structure, 425-metres tall and 28.5-metres wide with a slenderness ratio of 15:1, employed in-situ concrete construction pumped from street level, with 110MPa high-strength concrete.

Oakland Tower, a timber structure research project developed with the University of Cambridge

Lee Polisano, founding partner and president of PLP Architecture has been involved in the design of numerous tall buildings around the world. The practice has recently formed an internal research group, based on a series of partnerships and collaborations with universities, scientists and tech companies to consider what directions will be adopted in the future.

PLP is seeking to create a balance between health and wellbeing, smart technology and sustainability in terms of design. By 2028 smart buildings will be the norm, Polisano suggested, but with a focus on spatial variety: creating opportunities for people to gather in different types of space, to produce collaboration and ideas and promote productivity. For Polisano, tall buildings should work harder to provide placemaking, encourage sociability and visibility, accessibility and amenity, and allow people to connect with one another. Small and medium-sized companies need to attract the same talent pool as large companies so, at PLP’s 22 Bishopsgate, 15 to 20 per cent of the office space is given over to a range of amenities that are open to all of the tenants, in a building conceived as a vertical campus.

Andrew Waugh of Waugh Thistleton Architects spoke about how timber can be employed to create high-rise buildings, drawing on the practice’s 15 years’ experience in CLT and other engineered timbers. In 2017 it completed Dalston Lane Studios in London, a 17,000-square-metre mixed-use development 25 metres tall. Using BIM Stage 2, the practice could send drawing files direct to the CLT manufacturer, and through the finite element modelling could reduce the thickness of the material, using 25 per cent less CLT per square metre than it used at Murray Grove, nine years previously. Prefabricated structures of timber construction, including pod systems and volumetric construction offer a repeatable process but one that can readily be made bespoke, Waugh explained. Last autumn, he reported, a US Senate bill was passed to add the use of engineered timber in tall buildings of up to 18-storeys to its building code, predominately using as reference works in the UK.