Moisture content and moisture-induced stresses of large glulam members: laboratory tests, in-situ measurements and modelling

Franke, Bettina; Franke, Steffen; Schiere, Marcus; Müller, Andréas

doi:10.1080/17480272.2018.1551930

Cited by 14 publications

(7 citation statements)

References 5 publications

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“…In another numerical study, focusing on the moisture-induced stresses in timber frames (Ormarsson and Gíslason 2016), the tensile stress was found to be twice larger than the strength of the material. In addition, recent experimental and numerical studies on large glulam beams (Franke et al 2018) found out high values of MIS perpendicular to grain for a variation of moisture content of only ±6%. In that paper, the monitoring of climate and moisture content of a bridge structure in Switzerland, along with several indoor structures, has shown a difference of 3% MC between the outer and the inner fibres of the section that exposes the beam to the risk of crack formation.…”

Section: Introductionmentioning

confidence: 95%

“…In these kinds of modelling, the temperature T in wood is assumed to be equal to the air temperature (Fortino et al 2009) or considered as variable in thermal analyses sequentially coupled with hygro-mechanical analyses (Zhu et al 2010). Moistureinduced stresses in large glulam beams of bridges were recently simulated in Franke et al (2018) by using a hygromechanical analysis based on a single-Fickian approach for the moisture transport and a mechanical model including viscoelastic creep and mechanosorption.…”

Section: Introductionmentioning

confidence: 99%

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Moisture-induced stresses in large glulam beams. Case study: Vihantasalmi Bridge

Fortino

Hradil

Metelli

2019

Wood Material Science & Engineering

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The structural performance of timber elements may depend on the environmental conditions and in particular on the cyclic variations of the moisture content. Moisture gradients in the sections of the structural elements can produce additional stresses, the so-called moisture-induced stresses (MIS), which can cause the formation of cracks and delamination in wooden components. In order to achieve a reliable evaluation of the safety level of timber structures, the present paper proposes a numerical methodology to evaluate the MIS in glulam beams of timber bridges under Northern European climates and mechanical loads. A hygro-thermal multi-Fickian model for prediction of moisture content, relative humidity and temperature in wood is sequentially coupled with an orthotropic-viscoelastic-mechanosorptive model for calculation of wood stresses. Both models were developed by some of the authors in Abaqus FEM code in previous works and their coupling is used here to analyse the hygro-thermo-mechanical response of a glulam beam of Vihantasalmi Bridge in Finland under bending loads. Both perpendicular and parallel to grain MIS in a beam section sheltered from rain are evaluated during a 10-year analysis and conclusions on the crack risk related to these stresses are given.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Moisture-induced stresses in large glulam beams. Case study: Vihantasalmi Bridge

Fortino

Hradil

Metelli

2019

Wood Material Science & Engineering

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“…The surface-checking (SC) defect appears on the surface of the veneer and SL-based products when subject to desorption, resulting in small but visible cracks [10]. SC in solid wood and multi-layered wood products has been attributed to several phenomena: anisotropic shrinkage [13][14][15][16], drying gradient presence between the surface and a structure core [12,17,18], and restricted shrinkage [19,20]. SC reduces customer value due to decreased surface aesthetics, smoothness, and in-service performance due to possible moisture intrusion and retention in the crack cavities [21].…”

Section: Introductionmentioning

confidence: 99%

The Impact of Top-Layer Sliced Lamella Thickness and Core Type on Surface-Checking in Engineered Wood Flooring

Grubîi,

Johansson

2023

Forests

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Surface-checking is a significant quality issue of veneer and sliced lamellae-based wood products. This study explores how surface-checking in sliced lamellae-based engineered wood Flooring (EWF) is influenced by two key structure parameters: core type and top-layer thickness. The core types assessed were a standard solid wood lamellae with a veneer back-end layer (S), a standard solid wood lamellae core with veneer back-end layers on the two sides (DS), and a single-layer oriented strand board (OS) core. The EWF element’s top-layer lamellae were plain sliced at nominal dimensions of 1.5, 2.5, 3.5, and 4.5 mm from freshly sawn slabs of European oak (Quercus spp.). The surface-checking of EWF specimens was quantified based on a digital image correlation (DIC) method, which outputs a surface-checking index. The surface-checking results were evaluated using a Tweedie compound Poisson data distribution to fit a general linear model. The model evaluated the impact of individual factors, sliced lamellae thickness and core type, and their interaction. The checking index confidence intervals were estimated using a bootstrapping technique. Findings reveal a significant interaction between studied factors and provide insight into optimizing top-layer thickness and core construction to diminish surface-checking. A low sliced lamella thickness on standard solid wood lamellae core resulted in low surface-checking, deemed relevant for further research.

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“…Many studies regarding the impact of moisture gradients on beam bending in which simulations have been involved have been carried out. These have concerned both controlled changes in climate (Honfi et al 2014;Ranta-Maunus 2001) and changes in climate that occur naturally (Fortino et al 2019b;Franke et al 2019;Müller et al 2007;Toratti 1992). A variety of constitutive models has been used in such studies, involving one-, two-or three-dimensional space considerations.…”

Section: Introductionmentioning

confidence: 99%

A three-dimensional numerical analysis of moisture flow in wood and of the wood’s hygro-mechanical and visco-elastic behaviour

2021

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A three-dimensional numerical model was employed in simulating nonlinear transient moisture flow in wood and the wood’s hygro-mechanical and visco-elastic behaviour under such conditions. The model was developed using the finite element software Abaqus FEA®, while taking account of the fibre orientation of the wood. The purpose of the study was to assess the ability of the model to simulate the response of wood beams to bending and to the climate of northern Europe. Four-point bending tests of small and clear wood specimens exposed to a constant temperature and to systematic changes in relative humidity were conducted to calibrate the numerical model. A validation of the model was then performed on the basis of a four-point bending test of solid timber beams subjected to natural climatic conditions but sheltered from the direct effects of rain, wind and sunlight. The three-dimensional character of the model enabled a full analysis of the effects of changes in moisture content and in fibre orientation on stress developments in the wood. The results obtained showed a clear distinction between the effects of moisture on the stress developments caused by mechanical loads and the stress developments caused solely by changes in climate. The changes in moisture that occurred were found to have the strongest effect on the stress state that developed in areas in which the tangential direction of the material was aligned with the exchange surface of the beams. Such areas were found to be exposed to high-tension stress during drying and to stress reversal brought about by the uneven drying and shrinkage differences that developed between the outer surface and the inner sections of the beams.

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Moisture content and moisture-induced stresses of large glulam members: laboratory tests, in-situ measurements and modelling

Cited by 14 publications

References 5 publications

Moisture-induced stresses in large glulam beams. Case study: Vihantasalmi Bridge

Moisture-induced stresses in large glulam beams. Case study: Vihantasalmi Bridge

The Impact of Top-Layer Sliced Lamella Thickness and Core Type on Surface-Checking in Engineered Wood Flooring

A three-dimensional numerical analysis of moisture flow in wood and of the wood’s hygro-mechanical and visco-elastic behaviour

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