Timber with its natural appearance and glass with its transparency may be appealing material for architects and users of modern buildings. Glass is a brittle material, but it is about six times stiffer than timber. Combined appropriately, the materials could form different types of composite products, e.g. beams or shear walls, that can be included in the load-carrying structure of buildings. e knowledge on load- carrying timber/glass components is limited. e intention of this research has been to contribute to the knowledge required for the industry to be willing to produce timber/glass components for the market.
The thesis includes experimental testing accompanied with complementary nite element simulations, which provide more details and information about the test results. Tests were performed on small-scale specimens with a bond area of 800 mm2 as well as on I-beam and shear wall prototypes. For the small-scale specimens tested in standard climate, three different adhesives were used for the bond line between timber and glass. ese specimens were tested in both tension and shear. In addition, one of the adhesives was used for small-scale shear specimens which were exposed to different humidity levels before the tests were performed. e 4 m long I-beam prototypes designed with a web of glass and wooden anges were tested in four- point bending. e shear wall prototypes were tested by applying either a vertical load, a horizontal load or a combination of these, all being applied in the plane of the shear wall.
Of the three adhesives used in the small-scale testing, an acrylate adhesive had the largest strength, both in tension and in shear. e study on the effect of humidity was performed with this adhesive. is study indicates that the adhesive properties do not change dramatically in indoor climate. is adhesive was also used for twelve of the fourteen tested I-beams. e results from the beams show that a signi cant redundancy is obtained; the load at the nal failure was around 240 % of the load when the rst crack in the glass web appeared. e shear walls were glued using the acrylate adhesive and for a few cases a 2-component silicone based adhesive. e results from the shear wall tests showed the shear wall to behave in a much more brittle manner, without any noticeable redundancy.
Structural glass-timber composite beams and shear wall elements were investigated in terms of their mechanical behaviour, energy performance and their LCA performance. The load bearing components were manufactured using annealed float glass which was adhesively bonded to the timber with different adhesives. The results show, among other things, that is is possible to join the two materials glass and timber and obtaining a non-brittle failure of the beams. The shear wall elements have the potential of being used as stabilising elements and load bearing walls in buildings of up to 4 storeys height. It is possible to combine glass and timber in a load bearing shear wall without loss of energy performance of a building or without loosing LCA performance. In addition to these benefits, the timber glass composite wall has, of course the benefit of being transparent.
A wooden I-stud as a member of a light-frame timber wall is modelled with reducing flange width to simulate fire exposure. The stud is loaded with a vertical load and the effect of restraints from one gypsum board and the top and bottom rail is considered. Geometry and material values are chosen to correspond to a stud with flanges of solid wood and web of OSB (oriented strand board).
A model with shell and beam elements is implemented in Abaqus. A buckling analysis is performed on a perfectly straight stud and then a geometrically nonlinear analysis is performed on a stud with an initial curvature. Both the buckling analysis and the geometrically nonlinear analysis show that even a large reduction of the flange width results only in moderate changes of the load-carrying capacity of the structure.
In the report diagrams are presented from the geometrically nonlinear analysis where the critical load is easy to read once a failure stress is determined, but an estimate of the the failure stress is not given here.
Timber and glass are materials with aesthetically pleasing properties. If the materials can be combined appropriately, drawbacks can be overcome and the beneficial mechanical properties utilised and timber/glass elements can be a natural part of the load-carrying structure of buildings. Since glass is a brittle material, an important task for the timber is to provide redundancy – a glass failure should not lead to a catastrophic failure of the entire structural element.
This paper presents results from ongoing research related to load-bearing components made of timber and glass. Results from tests on small timber/glass bond-line specimens, recently submitted for publication, are briefly presented. The core of the paper is, however, a study of fourpoint bending tests on twelve timber/glass I-beams with acrylate adhesive. These I-beams had a nominal height of 240 mm and were designed with a web of 10 mm float glass and flanges of LVL (laminated veneer lumber), bonded together with an acrylate adhesive.
The mean values of the beams imply that the ultimate load capacity is 240 % of the load when the fi rst crack in the glass appeared. Thus, the timber well fulfils the redundancy task of avoiding a catastrophic failure of the structural element.
A study of three different adhesives, silicone, acrylate and polyurethane, intended for adhesive joints in structural timber/glass applications is presented in this paper. Intentionally, adhesives with a wide range of properties were chosen. The adhesive bonds between timber and glass were tested both in tension and in shear with a bond area of 800 mm2. Special fixtures were designed both for gluing and testing the specimens. The results include strength and failure type of the adhesive bond as well as deformation of the bond lines, measured with LVDTs and a non-contact optical 3D-deformation measuring system used in combination with finite element modelling in order to obtain detailed information about the behaviour.
Of the tested adhesives, the acrylate (SikaFast 5215) provided the largest strength, both in tension and shear. The mean strength obtained for this adhesive bond was 3.0 MPa in tension and 4.5 MPa in shear.
Further, it is demonstrated how rotations in the specimen during the test can be detected with the optical measuring system and how finite element modelling can be used to study the stress distribution internally in the adhesive bond. One conclusion obtained from the combination of results from the optical measuring system and finite element modelling is that the behaviour of the silicone adhesive is highly influenced by its near incompressible behaviour.
Both timber and glass are materials that have aesthetically pleasing properties. An appealing idea is to combine them to overcome the drawbacks and utilise the beneficial mechanical properties. Adhesive bonding with an appropriate adhesive could provide a uniform stress distribution at the transition between the materials.
This report presents a study of three different adhesives, silicone, acrylate and polyurethane. Intentionally, adhesives with a wide range of properties were chosen. The adhesive bonds between timber and glass were tested both in tension and in shear with rather small bonds, 800 mm2. Special fixtures were designed both for gluing and testing of the adhesive bond specimens studied. The results presented include a traditional study of strength, failure type and relative displacement measured with LVDT’s, but also an extended study with a non-contact optical 3D-deformation measuring system and finite element modelling.
Of the adhesives tested, the acrylate (SikaFast 5215) performed best, both in tension and shear. The mean strength obtained for this adhesive was 3.0 MPa in tension and 4.5 MPa in shear. Even if an important factor when gluing glass is the load distribution ability, the flexible silicone adhesive has too low stiffness and strength for use in structural components, where structural refers to the ability of a component to carry loads other than its own weight.