The guide is the USA’s first-ever set of recommendations for hybrid steel frames with mass timber floors.
Design Guide 37: Hybrid Steel Frames with Wood Floors encourages the use of mass timber floor systems in construction. Arup said that this is an underused yet important material to reduce the amount of carbon-intensive concrete in a structure.
“Mass timber and steel hybrid systems have tremendous potential to advance the building industry’s sustainability goals and reduce global emissions,” said Arup associate principal Michelle Roelofs. “Illuminating pathways for this hybrid topology will help accelerate the use of timber in place of more carbon-intensive materials.”
Design Guide 37 illustrates the potential of hybrid steel-frame buildings with mass-timber floors for achieving low-embodied carbon while optimising steel and mass timber. It provides a context for the new building typology, detailing strategies from the perspective of multiple disciplines. By facilitating this new generation of sustainable buildings, the guide will help accelerate the use of hybrid timber and steel in multistorey residential and commercial construction, said Arup.
In total, the building industry produces 50% of the globe’s greenhouse gas emissions, 20% of which is due to materials and material production, it said. Mass timber and steel is a low-carbon structural system option that can reduce the use of energy and emissions intensive materials such as concrete within buildings, it added.
The guide says that, while mass timber is lightweight, steel provides strength to structures and may better meet buildings’ vibration and span requirements. Hybrid steel-frame buildings with mass timber floor panels allow for longer beam spans and reduced column size than comparable mass-timber post and beam construction, making it an attractive option for market-driven spaces such as office buildings. Cross-laminated timber (CLT) flooring can take the place of carbon intensive concrete slabs and may be left exposed in places, such as at soffits, eliminating the need for additional architectural finishes and to showcase the structural aesthetics of both steel and mass timber. Both are prefabricated, which facilitates quality control and fast construction.
To create a design guide, Arup brought together fire safety, acoustic and sustainability specialists, along with structural engineers.
Arup’s hybrid steel-timber design for the Houston Endowment Headquarters in Texas achieved an almost 50% reduction in its carbon footprint relative to an original cast-in-place concrete design. The original schematic design for Houston Endowment Headquarters was reconsidered to address significant structural costs and a protracted construction schedule.
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