Buildings are currently responsible for 40 % of global energy consumption. At present, building expenses primarily stem from their operation. However, using energy-efficient construction methods, as envisaged under Energy Strategy 2050, it will be possible to considerably reduce this energy consumption. As a result, so-called “grey energy” that is used for the production of materials and the construction process is increasingly coming under the spotlight. Steel-free building structures offer an opportunity to reduce grey energy. This is because the production of steel is a very energy-intensive process. An alternative to steel is wood. It also stores CO2 and could thus contribute to reducing CO2 emissions into the air.
The prodigy among the woods is beech. This is because it is very strong and also a widely available raw material in Switzerland. Until now, however, beech has primarily been used as wood fuel, with softwoods dominating the area of timber construction. Beech therefore offers untapped potential.
In this sub-project, researchers from ETH Zurich have investigated how beech could be better used in combination with concrete and thus replace steel. They did so on the basis of ceiling constructions. In these wood-concrete composite ceilings, beech panels assume both the function of formwork and reinforcement and allow for a significant reduction in concrete and steel reinforcement compared to reinforced concrete flat ceilings.
So-called wood-concrete composite ceilings consist of wooden elements which are connected to a concrete slab in a shear-resistant manner. Compared to pure wooden ceilings, concrete increases the stiffness and mass of the ceilings. This in turn improves the vibration behaviour, sound insulation and fire protection – thus making the building component more suitable for use.
However, such hybrid constructions also have some disadvantages: they can usually only be loaded on one axis, which makes supporting elements such as beams and walls necessary. This restricts architectural design freedom. In addition, large quantities of fasteners are needed to hold the concrete and wood together. Such connections also lead to high local stresses being placed on the material and can suffer from corrosion.
The researchers have therefore investigated how wood-concrete could become cheaper, more resilient and more sustainable.