Durability of Timber Softwood/Hardwood Composite Systems

DURABILITY OF TIMBER SOFTWOOD/HARDWOOD COMPOSITE SYSTEMS

Research interest in innovative timber building systems suitable for multi-storey structures has increased significantly in recent years due to the increasing popularity of high-rise timber buildings. In this context, Research Project RP 3-1 focuses on the development of a novel, digital wood building system that allows a high degree of freedom in the structural grid, overcoming the design limitations of standard building systems that are characterised by rigid grids as an ordering system.

In particular, a new column-to-slab system consisting of cross-laminated timber (CLT) and glued laminated timber (GLT) elements has been developed, based on highly optimised individual components. The connection consists of two tailor-made beech LVL inserts glued into cavities on either side of the CLT (spruce) plate. A real-sized specimen was manufactured and its mechanical performance (load capacity and failure mode) was tested experimentally at the Materials Testing Institute (MPA) of the University of Stuttgart.

Innovative timber (hardwood/softwood) composite systems have many advantages over traditional reinforced concrete or steel-concrete composite systems, including lighter structures, sustainability and good predisposition to be prefabricated, reducing construction time and costs. However, the different mechanical and hygroscopic properties of the two wood types have a significant impact on both the short and long term performance of the composite.

To date, there is limited experimental data are available on the long-term performance of such systems under varying environmental conditions (relative humidity and temperature). This aspect is really important and should be properly taken into account in design.

With these premises, the new research project aims to get a better understanding of the complex hygro-thermo-mechanical behaviour of timber composite (hardwood/softwood) systems through experimental investigation and  the development of a novel and reliable material modelling approach. The developed numerical model, supported by experiments, will support the design by deriving durability functions/factors that account for the influence of relative humidity and temperature on the long-term performance of the timber composite systems. The project goals foresee a close collaboration with Research Project RP 3-2.

PRINCIPAL INVESTIGATORS

Dr. Serena Gambarelli
Materials Testing Institute (MPA), University of Stuttgart
Prof. Dr.-Ing. Jan Knippers
Institute of Building Structures and Structural Design (ITKE), University of Stuttgart

RESEARCHERS

Rey-Noe Fararoni-Platas (MPA)
Gregor Neubauer (ITKE)