Finite element modelling of moisture related and visco-elasticdeformations in inhomogeneous timber beams

• Wood is a hygro-mechanical, non-isotropic and inhomogeneous material concerning both modulus ofelasticity (MOE) and shrinkage properties. In stress calculations associated with ordinary timber design,these matters are often not dealt with properly. The main reason for this is that stress distributions ininhomogeneous glued laminated members (glulam) and in composite beams exposed to combinedmechanical action and variable climate conditions are extremely difficult to predict by hand. Severalexperimental studies of Norway spruce have shown that the longitudinal modulus of elasticity and thelongitudinal shrinkage coefficient vary considerably from pith to bark. The question is how much thesevariations affect the stress distribution in wooden structures exposed to variable moisture climate. Thepaper presents a finite element implementation of a beam element with the aim of studying how woodencomposites behave during both mechanical and environmental load action. The beam element is exposedto both axial and lateral deformation. The material model employed concerns the elastic, shrinkage, mechano-sorption and visco-elastic behaviour of the wood material. It is used here to simulate the behaviourof several simply-supported and continuous composite beams subjected to both mechanical and environmentalloading to illustrate the advantages this can provide. The results indicate clearly both the inhomogeneityof the material and the variable moisture action occurring to have had a significant effecton the stress distribution within the cross-section of the products that were studied.

Subject headings

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Trävetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Wood Science (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering (hsv//eng)

Keyword

Wood

Moisture induced stresses

Creep

FEM

Beam element

Civil engineering

Byggteknik

wood

moisture induced stresses

creep

FEM

beam element

Publication and Content Type

ref (subject category)

art (subject category)