Adhesively bonded joints
Adhesively bonded double lap joints composed were investigated both experimentally and numerically under consideration of various parameters such as overlap length, adhesive layer thickness and type of adhesive. Characteristic material properties of wood such as anisotropy, large scattering of mechanical values and brittle failure complicate the capacity prediction of bonded joints. A probabilistic concept allowed predicting capacities under consideration of the complex stress distributions in the joint. The proposed method has immediate actionable application for the dimensioning of adhesively bonded timber joints.
Rounded dovetail joints
In my PhD thesis I experimentally and numerically studied the structural performance of Rounded Dovetail Connections (RDC). RDC are mainly used to transfer vertical shear forces, but in my tests, I showed that they can carry considerable load in tension and bending and I demonstrated that self-tapping screws significantly improve the performance of RDC under vertical shear. My results showed that it is impractical to determine a set of empirical equations to describe the structural performance of RDC based on basic wood material properties. Therefore I developed a 3D FEA model and worked on a specific failure criterion which took into account the size effect.
Geometry optimization of contact joints
Contrary to most other timber connections, the load-deformation behaviour of contact joints is very ductile and rather than ultimate limit states, serviceability limit states are crucial. In this research, non-plane geometries were compared to a planar reference joint, as one approach of improving the performance of contact joints is by producing a non-plane geometry. The results demonstrate that non-planar geometries can increase the stiffness of contact joints; however since they exhibit a relatively large initial slip, the design loads regarding serviceability limit state are not increased. The reported approach has potential for the optimization of timber contact joints.
Experimental and numerical investigations on a composite wooden-timber composite beam connected by an adhesive layer elaborated on the possibility to simulate long-term effects of composite materials under varying conditions in climatic conditions. In a long-term investigation with two specimens under constant load, the creep deflection and climatic data were continuously measured. The objective was to provide experimental data to verify a numerical model of the creeping behaviour under changing climatic conditions.
Glued truss systems
Experimental and numerical investigations on full-scale adhesively bonded timber trusses were performed, comparing adhesive bonds to doweled connections. The adhesively bonded trusses achieved significantly higher failure load and stiffness. The influence of the embedded length of the applied steel plates was experimentally determined, delivering data to benchmark the subsequent dimensioning method. The trusses were then modeled and excellent agreement was found between numerical and experimental results. The investigation demonstrates the high potential of adhesive bonding in timber structures.
Nail-laminated timber elements
My MSc thesis project was dedicated to the study of nail laminated timber elements for the construction of buildings in Chile. The system consists in nailing together individual boards over their whole lengths and had taken an important position in Europe but was not yet introduced to the Chilean market. The project basically intended to demonstrate the suitability of nail laminated timber elements for the construction of timber houses in Chile.
Pre-stressed timber bridge decks
As Research Assistant in a project in Chile that promoted the use of Timber (FONDEF “Protection by Design in the use of Wood in the Road Infrastructure”), I was involved in the introduction of Stress Laminated Timber Decks to Chile. Stress laminated decks are multifunctional; they transfer loads, provide a dimensionally stable base for the asphalt layer, distribute concentrated loads, and minimize the deflection of the structure. The system is suitable for small dimension timber because of the possible use of but joints these and the costs of production and maintenance are comparably low.
As member of the Timber & Composite Construction research unit at the Bern University of Applied Sciences, I was involved in a very wide variety of industry consultancies, amongst them the testing of Wood-wall-concrete-deck-assemblies. Here the compliance of the assemblies in term of ultimate and serviceability limit states with Swiss regulations was investigated.