This is the longest existing research field of the institute. For more than 25 years, the institute has been investigating how planar and spatial structures can be realized in timber. This area ranges from ribbed elements and HP-shells up to product developments necessary for creating two- or three-dimensional load-bearing structures in timber. The institute is especially known for its leading research, development and transfer activities concerning probably the most innovative engineered timber product of the last two decades, namely Cross Laminated Timber (CLT). With the product CLT, engineers are able to use timber as a planar building material, opening up new market segments for timber constructions. All started in 1989 with the dissertation from G. Schickhofer (doctoral vita in 1994) and an award-winning FFF-project in collaboration with the regional sawmill industry afterwards. In 1998, the first National Technical Approval (ÖTZ) for CLT was issued to KLH Massivholz GmbH, which is today one of the most successful producers of Cross Laminated Timber. Another milestone was the presentation of CLT for structural use in the frame of the COST E5 conference in 2000. These first successes were followed by 14 years of R&D (focused on CLT) in collaboration with the holz.bau forschungs gmbh (founded in 2002). Related efforts made it possible to establish solid timber constructions on national and international level. This extensive R&D work at the institute may be one reason why between 2005 and 2010, the still most important CLT factories worldwide arose within a 150 km radius around Graz. Today, there are globally over 40 CLT factories with a worldwide production capacity of 650,000 m³. The institute will continue working in this research field especially focusing on modularization, prefabrication, connection techniques and system solutions. [Graz, 20. April 2016, GS]

There is no timber construction without fasteners. The key aspect to realise efficient and economical timber constructions requires the “right” choice of connection technique. Thus, the institute has been dealing with this topic since its early beginning. Within the last 10 years, focus was predominately set on axially loaded fasteners especially comprising self-tapping screws, which can achieve high load-bearing capacities at this load situation. In 2005, a master’s thesis was published, which developed and improved system connectors for transversal load transmission between main and secondary beams. Based on this research a long-lasting cooperation with a regional fastener manufacturer was established and led to the development of the well-known and worldwide recognised SHERPA connector. Besides axially loaded fasteners, which include glued-in rods as well, the institute also investigates the load bearing and deformation behaviour of laterally loaded fasteners such as dowels as well as variously shaped glued-in steel plates. The major difference between the more commonly used axially and laterally loaded dowel-type fasteners and glued connections is their potential in respect to strength, stiffness and ductility. These main connection properties need to be optimized, especially concentrating on a ductile behaviour. For future developments it will be important to focus on fast assembly times and the possibility to disassemble timber structures as well. In fact, both issues can only be achieved by prefabricated system solutions. [Graz, 21. April 2016, GS]

Established in 2014 and consequently the youngest research field at the institute, LHHA deals with product developments for various applications made of less used wood species. Due to existing and constantly growing resources as well as a good peelability, the focus is in particular on diffuse-porous hardwood species like beech, birch and poplar. Engineered timber products, built up from veneers, are more homogeneous than common board-based products and thus vary less in their mechanical properties. Besides the peeling process itself, the influence on strength and stiffness of veneers is investigated. By bonding the veneers together with ply-orientation parallel and/or perpendicular to each other, load-optimized cross sections (e.g. planar or shaped profiles) can be realised. Variously shaped profiles, like I-shaped or trapezoidal profiles as well as plates can be combined afterwards to create wall, roof, or ceiling elements. These products are characterised by comparatively high strength and stiffness in combination with a low variation of their mechanical properties. Besides the utilization as building material, the mobility sector “timber_meets_mobility” also plays an increasingly important role in the application of such shaped and optimized veneer based products. [Graz, 20. April 2016, GS]

Worth pointing out that more than 350,000 buildings in Austria are older than 100 years. Furthermore, the city of Graz has been UNESCO world heritage since 1999. Therefore, the institute is engaged in analysis and maintenance of historic timber structures comprising teaching as well as research. Within the last years, two remarkable projects were completed in this field. The first project lasting from 2009 to 2011 was funded by the “Zukunftsfond Steiermark” and the second one was conducted as FFG-bridge project in the timeframe between 2012 and 2014. The first project dealt with the analysis and the assessment of timber roofs combined with the development of maintenance and reconstruction plans for damaged parts related. Honoring the historic character of these buildings, structural modification should be kept at a minimum and only if the damaged components endanger the load carrying capacity. This especially concerns areas close to the supports as consequence of high moisture levels. In order to calculate and design a historic roof structure, a 3D-model is mandatory. In addition, all nodes must be modelled considering their specific stiffness and load-carrying capacity to achieve realistic results for structural verification. [Graz, 21. April 2016, GS]