Gustaf LarssonDoctoral Student
Innovative design enables strong and economic glued lap joints in timber constructions. The research demonstrates more than a twofold increase in load bearing capacity compared to standard techniques.
Timber construction is the best option to achieve sustainable housing solutions. This fact have strongly contributed to the increasing demand of high-rise timber buildings. Tall buildings do imply large forces, which requires larger construction elements and stronger connections in order to join the different elements together. In modern timber engineering such connections are costly and often non-efficient, two properties this research aims to improve.
One would expect that by doubling the size of two areas glued together, one would get a bond twice as strong. Unfortunately, that is however not the case with adhesives commonly used today. The adhesives are considerably stiffer than timber and thus does not allow the timber to elongate freely. So even though a large area is glued together, only a small part of it actually transfers load in which failure will occur prematurely. The solution is to make the bond line softer, which can be done by adding a thin layer of rubber foil between the elements.
Not only strength, but also a high degree of prefabrication and simple on-site assemblage is also important to obtain a cost effective connection. In order to achieve this, the rubber foil adhesive type bond line is implemented to bond steel plates to timber elements, a process preferably conducted in a factory. The timber and steel plates are fitted with a single large hole. By use of this hole, the on-site assemblage would the only require to align the timber elements and inserting a large single dowel as load transferring element.
The current research is evaluating this design concept in terms of strength, stiffness and durability by means of calculations, computer simulations and tests. A test series using 400x400 mm2 plates on each side found a load bering capacity of staggering 100 metric tonnes, almost three times as much as without rubber! The tests also verified the computer simulations which are used to further optimize material properties and geometries to find the ideal combination for the so-called Shear plate dowel connection.
Recent research outputs
Research output: Thesis › Doctoral Thesis (compilation)