Durability of Timber Softwood/Hardwood Composite Systems

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DURABILITY OF TIMBER SOFTWOOD/HARDWOOD COMPOSITE SYSTEMS

Research interest in innovative timber building systems suitable for multi-storey structures has largely increased in the last years, due to the increasing popularity of high-rise timber buildings. In this context, RP3 focuses on the development of a novel, digital wood building system, which allows a high degree of freedom in the structural grid, overcoming the design limitations of standard building systems, characterized by rigid grids as ordering systems.

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

Innovative timber (hardwood/softwood) composite systems have many advantages with respect to traditional reinforced concrete or steel–concrete composite systems, including: (i) lighter structures; (ii) sustainability; (iii) and good predisposition to prefabrication, with reduced construction time and costs. However, the different mechanical and hygroscopic properties of the two wood types greatly influence both the short- and long-term performance of the composite.

So far, limited experimental data are available on the long-term performance of such systems under variable 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 (RP23-1) is aimed at providing more insight into the complex hygro-thermo-mechanical behavior of timber composite (hardwood/softwood) systems through experimental study and development of a novel and reliable material modelling approach. The developed numerical model, supported by experiments, will support the design through derivation of durability functions/factors which 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 cooperation with 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

TEAM

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