Fatigue Strength of Glued-Laminated Timber Loaded in Shear Along Grain and Withdrawal of Threaded Rods.

Abstract

This thesis involves the investigation of both static and fatigue performance of two different longitudinal shear situations. The first being axially loaded threaded rods with small rod to grain angles. The second situation is longitudinal radial and longitudinal tangential shear properties for GL30c glulam. This thesis is therefore divided in three parts. The first part consists of introduction and general literature. The second part is the investigation of threaded rods. The third part is the investigation of longitudinal shear properties of GL30c. For the second part, a total of 10 static and 11 fatigue specimens were tested, this results in 20 static connections and 22 fatigue connections. The fatigue strength was better than anticipated with the slope of the SN-curve being 0,0374 for withdrawal in grain direction and 0,0398 for withdrawal at 5-degrees to grain direction. For the third part, a total of 51 static tests and 48 fatigue tests were conducted for two different designs which both had longitudinal radial and longitudinal tangential orientation. The specimen was modeled numerically, and strains were measured on the surface using video extensometer. Approximately 77 % of specimen failed by fracture propagation of a single plane. While the remaining 23% formed two planes. This is a considerable improvement compared to previous optimization. The characteristic shear strength f_(v,g,k) ranged between 3.51 MPa and 4.26 MPa depending on specimen design and orientation. The mean G-modulus was found to be 619 MPa for longitudinal radial orientation and 1145 for longitudinal tangential. The slope of the SN curve was between 0,0527 and 0,0815 depending on design and orientation. These values correspond well with literature.