With increasing attention in the construction industry being directed towards designs with reduced carbon emissions, hybrid designs combining wood with steel or other materials are increasingly sought out as solutions. At Buro Happold we are taking note and supporting this solution.
Timber offers both versatility and excellent seismic performance; steel provides strength and connections. Combining both materials for your project is often the most efficient way to reach optimal results.
Adaptability
Hybrid designs often deliver higher performance levels than timber alone; however, their success often depends on several factors including how well the components are connected and whether or not they have been adequately tested. Due to this complexity and time consumption involved with design processes such as this one, designers should take the necessary time to develop an efficient connection system and test for loads that they will face during real world applications.
As building owners focus more on reducing their embodied carbon footprints, structural engineering professionals have sought efficient designs with lower embodied energy usage as an important goal of structural design. One method to accomplish this goal is the combination of cross laminated timber (CLT) floor panels with steel framing. To help meet this goal more effectively, this study assessed which CLT-to-steel hybrid floor cross sections provided optimal efficiency when evaluated against multiple decision criteria for production stage greenhouse gas emission reduction.
For this to work effectively, the load-carrying capacity of hybrid components must be maximized. As such, various methods were tested in order to increase their bond between timber and steel. Adhesives proved an ideal method for joining these materials together when compared with dowel-type fasteners and punched metal plate fasteners (PMPF), with small scale specimens used to evaluate bond strength between materials; adhesive bonds proved superior by up to 82% compared with both dowel-type fasteners and PMPF fasteners resulting in maximum load carrying capacity of 82% shear capacity of hybrid component!
As demand for timber and hybrid design increases, building owners, design teams and authorities with jurisdiction are quickly adapting. This pre-recorded webinar will explore innovative projects where hybrid wood/steel systems maximize each material’s advantages; also discussed will be some challenges associated with including hybrid elements into tall timber buildings as well as solutions.
Energy efficiency
Use of hybrid designs combining timber with steel or other materials results in more energy-efficient buildings. This approach marries structural efficiency with warmth and flexibility provided by wood, as well as increased resilience against seismic or wind hazards. Hybrid construction also helps lower embodied carbon in buildings.
One hybrid design approach involves the combination of glulam with steel ribs to form a hybrid truss structure. Steel provides stiffness and strength necessary to support slender timber members. A hybrid system offers an economical solution that is both straightforward and versatile in application. Timber may not always perform optimally with steel; therefore the design must take this into account when planning. As an example, it is critical that wood members be placed near the top chord (in compression) while steel remains at the bottom chord (tension). Furthermore, connections should be designed so as to avoid thermal expansion gaps occurring between components. It is also vitally important to work with fabricators who understand both timber and steel fabrication processes as their connection details differ significantly from standard AESS standards.
Engineered timber has long been utilized in the construction industry, yet only recently has it gained momentum as a material of choice to construct large-scale structures. This trend can be traced back to its advantages over concrete and steel: among these advantages being its versatility in creating intricate shapes without increasing costs significantly. Engineered timber allows architects to achieve their vision while saving on costs at once.
Timber provides many advantages: carbon storage and renewable resource status; its aesthetic qualities exceed steel and concrete; however, timber does lack some of the stiffness and strength that high-rise buildings need – hence engineers often combine timber with other materials that offer more stiffness or load-bearing capacity than its own materials can offer.
The most prevalent approach for bonding timber to steel is with adhesives. Different methods have been tested, including dowel-type fasteners and punched metal plate fasteners (PMPF). A recent study concluded that adhesive bonds provide the superior performance in timber-steel hybrid sections compared with dowels (tensile strength being up to 9 times greater) and PMPFs (5.55 times more shear capacity than dowels). Furthermore, hybrid steel-timber buildings may reduce superstructure embodied carbon by up to 5-35% when compared with steel-concrete buildings
Flexibility
Hybrid designs provide greater flexibility than single material designs by taking advantage of timber’s beneficial features when needed, and employing other materials when necessary. CLT (cross-laminated timber) flooring may reduce carbon emissions while steel trusses may improve seismic performance; using multiple materials simultaneously allows hybrid designs to balance sustainability with strength – something eco-conscious projects must take into consideration.
Hybrid construction is a rapidly developing field of structural engineering, and new technical solutions are constantly being created to meet market demands. Peikko recently released a standardised range of timber-to-steel connection items designed to make designing hybrid structures simpler, making the creation of reliable hybrid structures much simpler for engineers.
But many experts recognize there are challenges associated with wider adoption of hybrid structures, particularly in Australia where high-rise timber-to-steel buildings have not seen widespread uptake. To combat these difficulties, researchers are conducting several experiments designed to explore Australia’s potential for hybrid timber-to-steel construction.
One such experiment involves testing the performance of hybrid steel-timber beams. These beams consist of radiata pine and Douglas fir timber lamellae that have been bonded to encased steel sections, with these studies evaluating their resistance to bending, load bearing capacity and impacts from adhesive types, size/location/type etc. to develop more efficient structural designs for hybrid steel-timber buildings in Australia.
This research could have an enormously transformative effect on how high-rise buildings are designed in Australia. The goal is to reduce their global warming potential (GWP) by decreasing concrete use.
The structural industry is witnessing an international shift toward hybrid steel-timber building techniques for high-rise buildings, driven by various factors including dominant geography; building function; height considerations and other variables.
Sustainability
As construction practices evolve towards more eco-friendly approaches, timber has emerged as a desirable building material with both environmental and architectural benefits. Unfortunately, its strength and durability limits how far timber can be utilized on certain projects; to maximize its usage in such cases, many design teams are turning toward hybrid structures which combine mass timber’s benefits with steel or concrete strength to produce the perfect hybrid structure.
Hybrid designs can also offer significant sustainability advantages. Employing various materials together can reduce overall embodied carbon emissions and improve energy efficiency while offering flexibility, adaptability and cost savings. Combining wood with concrete construction material may reduce construction costs and speed up the building process; however it’s essential that appropriate combinations of materials be selected to protect structural integrity of buildings.
Hybrid buildings provide more than carbon savings; they can also offer enhanced seismic resilience compared to traditional steel-concrete structures. A recent study examined six pioneering case studies of hybrid designs combining steel framing and timber truss construction for earthquake resilience purposes. Results demonstrate that hybrid structures provide more eco-friendly alternatives while also meeting all AEC Code seismic requirements.
Timber construction dates back millennia; its recent resurgence is driven by increased attention on sustainable practices and lower embodied carbon emissions. Now more construction firms are turning toward wood as part of a plan to combat climate change while creating healthier environments.
Microsoft and Gensler, working alongside Thornton Tomasetti, recently conducted research that demonstrated how using sustainable wood can significantly lower a data center’s carbon footprint compared to conventional steel construction and 65 percent when compared with precast concrete construction. When coupled with innovative engineering solutions and careful team planning, hybrid construction is an attractive option for builders seeking to minimize environmental impact from their project.
Timber is an ideal material for high-performance buildings, yet its strengths and weaknesses must be carefully considered during design. Engineers need to understand its strengths (stiffness, durability), weaknesses (permeability) and environmental impacts before proceeding with its use. Hybrid construction has become an increasingly popular solution that brings together various advantages of different materials to produce unique structures with lasting visual appeal and functionality.