System effects influencing the bending strength of timber beams

Ove Dalager Ditlevsen, B. Källsner

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


    A stochastic model of hierarchical series system type for the bending strength of spruce beams isdefined from the anticipation that the bending failure takes place at a cross-section with a defect cluster formed by knots or grain irregularities. The parameters of the model are estimated from measurements of the strengths of a large number of shorttest pieces cut from the beams such that judgementally each test piece contains only a single defect cluster. The testpiece is spliced to stronger wood beam shafts in both ends. Due to the occurrence of a substantial number of splicefailures in the total test series of 197 tests a special maximum likelihood estimation procedure is applied to estimate theparameters. Assuming that the estimated parameters are applicable in the series system model for the full uncutbeams a theoretical bending strength distribution function is obtained in dependence of number of defect clusterswithin the span of constant bending moment loading. A strong test of the predictional power of the model is establishedby experiments with 54 long beams from the same population of beams from which the small test pieces were cut.
    Original languageEnglish
    Title of host publicationReliability and Optimization of Structural Systems
    Place of PublicationAnn Arbor, USA
    PublisherUniversity of Michigan
    Publication date1998
    Publication statusPublished - 1998
    Event8th IFIP WG 7.5 Working Conference on Reliability and Optimization of Structural Systems - Krakow, Poland
    Duration: 1 Jan 1998 → …


    Conference8th IFIP WG 7.5 Working Conference on Reliability and Optimization of Structural Systems
    CityKrakow, Poland
    Period01/01/1998 → …

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