Monotonic and cyclic pull-pull tests on dowel-nut connector in laminated veneer lumber made of European beech wood. (12th December 2022)

• Record Type: Journal Article
• Authors: Fabbri, Andrea; Minghini, Fabio; Tullini, Nerio
• Is Part Of: Construction & building materials. Volume 359(2022)
• Publication Date: 2022-12-12
• Subjects: Dowel-nut -- Bed-bolt nut -- Barrel bolt -- Larsen bolt -- Beech -- LVL -- Monotonic test -- Cyclic test -- Pull-pull test -- Preload -- Tightening; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2022.129461
• Languages: English
• ISSNs: 0950-0618

Abstract

Graphical abstract: Highlights: 45 load tests on threaded rod with dowel-nut connector in beech LVL bars were conducted. Preloading the connection increased both tension and compression stiffness. Greater strength and smaller scatter were found for dowel axis orthogonal to the veneers. Strengths for dowel end distances 2.5 d and 5 d were 33% and 100% those for 7.5 d. No increase in strength degradation was observed due to cyclic loading. Abstract: The findings from tests on steel dowel-nut connector in Laminated Veneer Lumber (LVL) bar are reported. Test specimens were prepared using LVL members made of European beech wood ( Fagus sylvatica L. ), showing a square cross-section of side length 50 mm and veneers arrangement comprised of 18 layers with the grain oriented in the bar longitudinal direction. The tested connection consisted in a 12 mm-diameter longitudinal threaded rod of class 12.9 steel (nominal yield strength f yb = 1080 MPa) screwed into a transverse 20 mm-diameter (= d ), 50 mm-long dowel-nut. Three monotonic compression tests and 42 pull-pull tests were carried out. Among these latter, 22 were monotonic and the remaining 20 were cyclic. The dowel-nuts were also made of class 12.9 steel, with the exception of those used in ten cyclic tests, which were of grade S355 steel ( f yk = 355 MPa). Preloading the connection with a controlled tightening increased both tension and compression stiffness. Greater tensile strength and smaller results scatter were found for dowel-nut axis orthogonal to the veneers. Load-carrying capacities obtained for dowel-nut end distances of 2.5 d and 5 d were 33% and 100%, respectively, those obtained for 7.5 d . In cyclic tests, no significant increase in the strength degradation was observed due to cyclic loading. In the case of grade S355 dowel-nut, evident plastic deformations were achieved in the connector for end distances 5 d and 7.5 d . However, this did not influence neither strength nor corresponding displacement.