| Abstract [eng] |
Timber structures have been used in construction for a long time. The main subjects of this thesis are the reinforcement of timber beams with carbon fiber, the determination of deformations in reinforced beams, and the determination of beam strength by bending in accordance with the LST EN 408. Specimens of three different types – 36, 48, and 56 mm wide – as well as three types of glue intended for gluing them – polyurethane glue, epoxy resin, and experimental melamine urea formaldehyde resin glue – were chosen for the test. The latter glue was used only in tests with 48 mm beams. The tests performed with beams of 48 mm width have shown that the strength of a beam inset with carbon fire increases by 6,15 per cent when using polyurethane glue, 2,52 per cent when using epoxy resin, and 2,99 per cent when using melamine urea formaldehyde glue. The reinforced beam strength is compared with the average strength of the 48 mm wide solid wood beam. In further tests, the latter beams are treated as a reference point. Other tests were performed on 36 mm wide beams: when insetting the carbon fiber with the use of polyurethane glue, an increase of 0,55 per cent in strength was witnessed, while gluing with epoxy resin caused a decrease of 13,35 per cent in strength. Tests with 56 mm wide beams have shown an increase of 7,99 per cent in strength when gluing with polyurethane glue and an increase of 6,73 percent in strength when gluing with epoxy resin. Two types of research were performed in the thesis: in the first case, the carbon fiber was inset in the middle part of the beam; in the second case, the fiber was inset in the lower part of the beam. The strength of 36 mm wide beams was compared as well: it became apparent that the insetting of carbon fiber using polyurethane glue makes no impact on the beam strength. However, the results are quite the opposite when using the epoxy resin. With carbon fiber strip on the bottom of the beam, the beam strength increased by 20,31 per cent. When bending the beam, the greatest tensile strength was witnessed on the bottom of the beam; therefore, this increase in beam strength can be explained by the presence of the carbon fiber strip in that very position. During the tests, a specific amount of beams was chosen for a measurement of beam deformation. After the tests it became apparent that the deformations distributed very evenly. In thinner 36 mm beams the deformations fluctuate up to 27 mm, while the thicker beams have deformations up to 18,5 mm in width. After performing the research, certain recommendations are given. |
