REGENERATIVE HIGH-RISE

REGENERATIVE

HIGH-RISE

Bethel Teferra, Senior Consultant at Ramboll, illustrates how a modular, sustainable high-rise tower that evolves with a city’s needs could be a future reality and include engineered timber as key component.

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Modular houses may have been around for a while, but modular high-rise with flexibility in function is a relatively new concept. Imagine a high-rise building made up of modular units that can be slotted in-and-out, with spaces for living, working and playing – a building whose functions evolve according to a city’s needs, built with sturdy and sustainable materials and a building that’s adaptable, practical and eco-friendly.

Created by Haptic Architects and engineering firm Ramboll, the

‘Regenerative High-Rise’ blends exactly this flexibility and functionality and aims to redefine conventional uses and lifespans of high-rise buildings in cities worldwide. Constructed from a hybrid timber mix, the high-rise shows how tall buildings can be both versatile and green at a time when climate change is a pressing concern and requires a drastic rethink of the built environment.

So how does this modular structure work? What are the various uses for this type of building – and perhaps most importantly, how can it be made more accessible?

The high-rise structure aims to find the optimum between two key constraints: flexibility in function and sustainability credentials via the use of timber and other similar offsite production structural elements. To equally satisfy the two constraints is a true balancing act as the requirement for large spacious layouts imposes the need for higher capacity structural elements, whereas sustainability is driven by minimalism. Consequently, the highly loaded tower columns supporting large spans with critical load-path are proposed in recycled steel, sand timber-composite and modular options for frames defined within three-storey ‘villages’.

The core-wall (framing the lift shaft) gives the high-rise structural lateral stability, using the Lateral Force Resisting System (LFRS) via a precast and steel-brace solution that provides sufficient lateral-stiffness against building sway, enabling the building to resist environmental loads arising from wind and seismic activity. Being an offsite manufactured solution, the precast central-core provide sufficient stiffness and sustainable solution, given its durability and low-carbon footprint.

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Overall, the vertical elements including LFRS consist of a 20-40-40 timber-steelprecast ratio.

The floor divide has a ‘hard floor/ soft floor’ concept. The hard floors at every third level work as a diaphragm mechanism to transfer lateral load to LFRS in the overall structural system. These transfer-floors are proposed to have the flexibility to support the construction of up to three-storey ‘villages’ which consist of ‘soft-floors’ and other modular plug-and-play frames. Hence, for the diaphragm horizontal elements, cross laminated timber (CLT) floor construction with recycled steel beams is proposed. The steel beams are used to reinforce the CLT overall, to compose a robust floorsystem that resists the above modular three-storey floor occupancy loading as well as assist to meet its serviceability limits. The horizontal elements have a timber-steel proportion of 80-20. This timber-composite mix benefits the high-rise with not only its low carbon footprint, but also imbues it with a warm aesthetic.

The flexibility of the ‘hard floor/soft floor’ concept is a highlight of the ‘Regenerative High-Rise’. The innovative structural and MEP design aims to serve multi-purpose occupancy including hotel, residential, office, retail and entertainment, but the high-rise’s flexibility in design means it could also extend beyond these functionalities too, if needed. For example, such buildings could be used to cater to unexpected demands for flexible space as we’ve seen during the recent COVID-19 crisis, which at its peak brought about a sudden large need for extra hospital rooms, medical treatment centres, testing facilities and quarantine spaces. In such cases, buildings with flexible functionality would be best suited to meet great societal needs, whilst also having a positive impact on the need for sustainable and economical building solutions.

The project utilises offsite construction and is inspired by Scandinavian prefabricated housing. While prefab homes have existed for some time, modular towers are a new and innovative concept, and the global construction market may be slow to adopt new technologies compared to fast-moving industries like information technology, automation, financial markets. Construction markets vary from region to region, depending on factors such as economy, resources and natural environment. Contractors, engineers and architects’ familiarity in the design and delivery of offsite construction solutions, as well as familiarity of skilled labour can be key aspects to widespread adoption of offsite methods. While professional institutions endeavour in continual education of engineers and architects and stimulate wider discussion on latest innovations, another idea to drive offsite to wider market can be that companies specialising in these technologies could actively seek opportunities to enter emerging market economies. Likewise, innovative and adoptable holistic-building design solutions that are aspiring such as advanced modular construction solutions contribute to the advancement of the field – like the regenerative high-rise.

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www.uk.ramboll.com www.hapticarchitects.com

IMAGES:

01-03. Modular, sustainable high-rise with a timber/hybrid approach is a vision of city regeneration. Courtesy Forbes Massie Studio

TWO DOUNE ONE ACROSS

New timber bridges in the UK are still relatively rare phenomena, especially ones fabricated from material extracted from local forests or woodland. A new development at Doune Castle proves what can be achieved with homegrown timber.

When a new timber bridge emerges that is not only visually striking in its design but constructed from timber sourced from within spitting distance of its site, you know change is in the air regarding outdated perceptions of UKgrown timber’s usefulness.

You may never have been to Doune Castle, but you will almost certainly have seen it: its imposing structure has featured in ‘Monty Python and the Holy Grail’, ‘Game of Thrones’ (as Winterfell) and ‘Outlander’ (as Castle Leoch). The Castle’s attractiveness to national and international visitors has increased to the point where the infrastructure of the site and the adjacent historic village was under unsustainable pressure, as there were no obvious pedestrian links between it and Doune Village.

This has now changed. Finance from the Rural Tourism Infrastructure Fund (RTIF) in 2019 enabled a collaboration between Stirling Council, Historic Environment Scotland (HES), the Kilmadock’s Community Development Trust and Kilmadock’s Community Council to plan several important projects. The most significant of these is the recently completed pedestrian bridge crossing the Ardoch Burn by the Mill of Doune and the associated paths to/from it.

So, what makes the bridge so remarkable? First, it is configured as two asymmetrical arches of 20m and 10m respectively to span the fast-flowing water. The bridge’s deck stretches over the 10m run-offs either side of the crossing to connect the high points, extending its overall length to 50m. Second, the bridge is cranked on-plan and it is the combination of these two factors that make its timber engineering so innovative in design.

The bridge structure is made from short pieces of timber – locally-grown larch – that are 50mm wide and up to 250mm in depth and laminated in 1500 or 2000mm lengths. The fabrication method uses a ‘glue and screw’ method to vertically connect the deep boards by gluing and screwing between each row of laminates to form a single solid mass of timber. This empirically tested technique allows arches with a flatter profile to be constructed and the application of this laminated structural solution is particularly suited to the use of locally grown larch as this improves the structural performance of a material that would otherwise not be suitable for bridge construction. The main span of the bridge is currently the longest single span timber ‘glue and screw’ arch built to date.

The arches support a more traditional post, beam and joist deck arrangement, added to which the guarding on either side of the bridge has been developed as a series of three-dimensional forms constructed from lengths of larch connected into panels and mounted onto oak primary support rails. The design ingenuity of this responds to the bridge’s cranked plan and greatly enhances the sculptural impact of the arches’ geometry.

The principal timber used in the construction of the bridge is homegrown Scottish larch, sourced from woods that sit to the north-east of Doune in the Moray Estate. After felling, the timber was cut locally to the sections required using mobile saw-milling equipment before being visually graded for kilning. Once dried, the material was planed and CNCmachined to the precise dimensions required for fabrication. Both structural arches were manufactured offsite before delivery to site and their final lifting into place as complete structural elements. The finished bridge construction is likely to require very little maintenance during its lifespan.

Designed by Historic Environment Scotland architect Gary Treacy, engineered by Fairhurst with Geoff Freedman Rural Bridges and constructed by Beaver Bridges Ltd, the new pedestrian bridge at Doune Castle is not only a visually striking demonstration of innovative structural design employing locally-grown and milled timber, but also stands as an exemplar of the merits of offsite manufacture, foregoing the need for on-site scaffolding in a challenging location. The pedestrian bridge at Doune Castle proudly displays the symbiotic benefits that context-driven design thinking and procurement can bring to the UK’s culturally- and environmentally sensitive landscapes.

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www.historicenvironment.scot

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01. The new bridge is a timber connection and homegrown timber innovation.

Courtesy Historic Environment Scotland