Structural design of hybrid steel-timber buildings for lower production stage embodied carbon emissions

Abstract

Using cross laminated timber (CLT) floor panels in combination with steel framing has been identified as a promising new structural configuration that can reduce the embodied greenhouse gas emissions of buildings. This project evaluated efficient structural design of hybrid steel-timber floor sections for a wide range of design parameters to determine the reductions in global warming potential possible relative to a conventional steel-concrete cross section. Each of the structural designs was checked for strength limit states, deflection, and minimum fire rating of either unrated, 1-h, or 2-h for a range of deck spans between 2.3 m and 4.6 m and beam spans between 5.5 m and 13.5 m. For an unrated floor assembly there is little global warming potential benefit to use steel-timber floors if a topping slab is included on top of the CLT slab. Whereas, using steel-timber configurations without a topping slab result in the largest global warming potential reductions. For the 1-h and 2-h ratings, even steel-timber configurations with a 64 mm thick topping slab had up to 20% reduction in global warming potential compared to the steel-concrete alternative. Additionally, several considerations that can drastically affect the global warming potential results were discussed. The results from this project demonstrate the best practices for structural design of hybrid steel-timber buildings to reduce global warming potential of the superstructure frame by between 5% and 35% relative to conventional steel and concrete construction.