Axially stressed threaded rods glued into the wood
2015, 2017
Glued-in threaded rods are used in construction to replace conventional fasteners. The load-bearing capacity of various standard connections was investigated. Characteristic values were determined from the test results.
Basic principles and research procedure
The load-bearing behavior was determined at different wood strengths, bond lengths and fiber-load angles. Furthermore, the influence of reinforcing the transversely stressed areas with double-threaded screws was investigated. Tensile tests, with threaded rods glued into the transverse layers of cross laminated timber, were carried out.
Glulam (spruce GL24h) was used for the standard connections and the reinforced test series. For the preliminary tests with cross laminated timber, a 5-ply panel (spruce C24) was used. Bonding was carried out with the 2-component polyurethane casting resin LOCTITE® CR 421 PURBOND from Henkel & Cie. AG.
Results and conclusion
It was shown that the wood strength has no influence on the load-bearing behavior, although considerable differences were observed in the fiber-load angle. When comparing the mean fracture values with the standard used today, it was shown that the characteristic pull-out values according to the current design standard are about 30% lower than the mean fracture values of the tests. The double-threaded bolts prevented splitting of the test specimens in the transversely stressed area. In the series with two threaded rods, an increase of 38 % in the load-bearing capacity to above the yield strength of the steel was observed for the same bond length.
Type of work: Thesis at BFH AHB Authors: Markus Ryffel (2017), Michael Hollenstein (2015)