DOL effect of different sized timber beams

Abstract

beamsThe objective of an AIR PROIECT (1994PROIECT ( -1997 was to establish a new scientific basis for the determination of the long term performance of reconstituted timber (glulam and LVL) in a variable environment with a duration of load of a few months. Three current problems of timber engineering were treated: delayed fracture in bending of straight or notched beams, delayed fracture of curved beams by tension perpendicular to grain, with the same methodology and with a sufficient number of tests to obtain a good statistical and phenomenological understanding of the phenomena. DOL-Effekt (Duration Of Load) in Tri~gern verschiedener Form und AbmessungZiel dieses Projektes war das Erarbeiten einer neuen wissenschaftlichen Grundlage zum Bestimmen des Langzeitverhaltens van verleimten Werkstoffen (Glulam und LVL) in wechselnder Umgebung und unter Belastung van einigen Monaten. Drei aktuelle Probleme des Ingenieurholzbaus wurden behandelt: a) der verz6gerte Biegebruch in einteiligen und b) keilgezinkten geraden Tr~igern, sowie c) der verz6gerte Bruch gekriimmter Tr/iger unter Zugbelastung senkrecht zur Faser. AUe Proben wurden mit der gleichen Versuchsanordnung und in ausreichender Probenzahl geprfift, um gesicherte statistische Assagen und ein gutes Verst~indnis der Ph/inomene zu erarbeiten.

Duration of load behaviour of different sized straight timber beams subjected to bending in variable climate

“…In addition, a factor kMc was defined to quantify, the effect of moisture content on long-term strength as compared to tests at standard conditions (65%RH, 20 ~ The product of the two factors was denoted kmod. These factors have been discussed in detail by Morlier and Ranta-Maunus (1998). This methodology provides practical means to estimate the differences of DOL-behaviour in different conditions.…”

“…A review of earlier results of DOL-effect studies is included as part of the introductory paper of this series (Morlier and Ranta-Maunus 1998).…”

Adhesives for on-site bonding: Characteristics, testing and prospects

“…In Eurocode 5 this strength reduction is taken into account by means of the modification factor, k mod , used to derive the design values. The values of k mod approximately conform to the behaviour of the stress level versus the logarithm of time to failure for timber, according to the linear Madison curve [47]. These values are defined through consideration of load duration classes: permanent (e.g.…”

Service life modelling of timber structures

“…A ''moisture load'' due to humidity variations may be included in cases where tension stresses perpendicular to the grain are expected. For instance this is the case for curved or pitched cambered glued laminated members, where cracks have been discovered in the area with high stresses perpendicular to the grain, relatively early after erection of the structure [28]. The parameters C 1 and C 2 are determined from standard time to failure tests.…”