New design guide for hybrid steel-mass timber frames released

The American Institute of Steel Construction (AISC) has released the first-ever set of U.S. recommendations for hybrid steel frames with mass timber floors, according to a news release.

Design Guide 37: Hybrid Steel Frames with Wood Floors, written by Arup, encourages the use of mass timber floor systems in construction, “an underused yet important material to reduce the amount of carbon-intensive concrete in a structure,” the release says. The guide provides a comprehensive context for this 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 multistory residential and commercial construction. Mass timber is lightweight, and 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 allowing for the showcasing of the structural aesthetics of both steel and mass timber.

“Mass timber and steel hybrid systems have tremendous potential to advance the building industry’s sustainability goals and reduce global emissions,” said Michelle Roelofs, associate principal at Arup. “Illuminating pathways for this hybrid topology will help accelerate the use of timber in place of more carbon-intensive materials.”

New York City has two very large buildings dedicated to answering the 911 calls of its five boroughs. With more than 11 million emergency calls annually, it makes perfect sense. The second of these buildings, the Public Safety Answering Center II (PSAC II) is located on a nine-acre parcel of land in the Bronx. It’s an imposing 450,000 square-foot structure—a 240-foot-wide by 240-foot-tall cube. The gleaming aluminum cube risesthe equivalent of 24 stories from behind a grassy berm, projecting the unlikely impression that it might actually be floating. Like most visually striking structures, the building has drawn as much scorn as it has admiration.