While most other timber construction projects attempt to maximise the use of timber, the LCT concept focused instead on the most efficient use of resources. LCT ONE is Austria’s first timber building at this height, where the load-bearing timber elements did not need to be enclosed but remained visible and untreated.
The eight storey prototype consists of a circulation core, which stabilises the entire structure, with office spaces attached on one side. Its load-bearing system comprises three main elements, which by nature of their construction are cavity-free: the building core, the floors and the facade supports. The core was originally planned to be constructed from solid timber. Nevertheless, in the case of the LCT ONE pilot project, in-situ concrete had to be used instead. This was primarily due to the Austrian fire protection regulations which do not yet allow for the construction of a structural core made from flammable materials.
The floor slabs are prefabricated units. Each of these 2.1 m units consists of an 8-cm-thick concrete slab supported by four parallel beams made of glued laminated timber (cross section 24 ≈ 28 cm). Each floor element has to be supported on its four corners. At the core, the floor slabs rest on welded steel consoles. Along the facade, supports are formed by the laminated timber columns. The facade columns consist of two glued laminated timber rectangular sections each 24 ≈ 24 cm. Each of the two column halves supports an adjacent floor element. The columns are all hinged columns and are only subject to perpendicular forces.
The facade and floor elements of the upper levels are erected one storey at a time.The end of each construction phase results in one completed storey – with the moisture sensitive wood finishes inside the building protected from inclement weather by the floors and facade elements. Work on the interior finishes can thus begin immediately.
In order to assess the benefits of the composite construction, the client performed a environmental impact assessment according to the criteria defined by the German Sustainable Building Council (DGNB) shortly after the completion of the pilot project. During an assumed life time of 50 years, the LCT ONE emits 27 kg of CO2 per square metre of net floor area per year, of which approximately two thirds result from the building operation and one third from the construction. That is approximately 32 % less CO2 emissions than a conventionally built reinforced concrete building of the same size and with the same use. Over the course of its life cycle, the building thus saves 340 tonnes of CO2 emissions. This is comparable to the amount that a Volkswagen Golf would emit during 60 circumnavigations around the globe.
