Numerical analysis of moisture-induced strains and stresses in glued-laminated timber

Huč, Sabina; Svensson, Staffan; Hozjan, Tomaž

doi:10.1515/hf-2019-0025

Cited by 8 publications

(5 citation statements)

References 53 publications

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“…A protocol for the preparation of relevant calculations was reported by Hering (2011). Although it is important to properly understand the aging mechanism, the long-term performance of gluelaminated timber products has not been sufficiently researched (Hering 2011, Niemz 2016, Clerc et al 2017, Clerc et al 2020a, 2020b, Huč et al 2020. The numerous laboratory tests conducted provided adequate reference data corresponding to reasonable exposure times covering multiple years of service.…”

Section: Influence Of Mechanical Loads and The Surrounding Climatementioning

confidence: 99%

Selected previous findings on the factors influencing the gluing quality of solid wood products in timber construction and possible developments: A review

Hänsel¹,

Sandak

et al. 2021

Wood Material Science & Engineering

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Various factors affect the bonding quality of elements used for timber construction. This review includes literature studies and personal experiences related to relevant technological variables defining glue bond performance in glue-laminated timber elements during their service life. The gluing of hardwood species receives special focus as it is considered by the industry to be the most challenging process for implementation. In particular, the effects of wood species, type of adhesive, glued-wood surface quality, physical and/or chemical modification of the wood, technological solutions for gluing, and varying climatic conditions during the use phase (relative humidity, temperature, air circulation, etc.) are considered. In addition, overlapping of individual influencing factors often leads to problems with bonding, thus requiring strongly integrating measurement methods (e.g. NIR spectroscopy). The causes of variations in the results when glued wood is tested using different standardized methods are discussed. A list of open research questions is provided, and problem solutions are recommended based on systematized cuttingedge knowledge. The aim of the work is to systematize the state of knowledge of wood gluing to create a basis for controlled and stable manufacturing processes. The progress of the work will be reported in further publications.

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Section: Influence Of Mechanical Loads and The Surrounding Climatementioning

confidence: 99%

Selected previous findings on the factors influencing the gluing quality of solid wood products in timber construction and possible developments: A review

Hänsel¹,

Sandak

et al. 2021

Wood Material Science & Engineering

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“…This model was extended in [18] to 3D and updated to yield a symmetric creep compliance matrix. In [19,20], the capabilities of the model from [16] were investigated regarding mechanosorptive creep.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Moisture-Induced Stresses in Wood Cross-Sections Determined with a Time-Dependent, Plastic Material Model during Long-Time Exposure

Pech,

Autengruber,

Lukacevic

et al. 2024

Buildings

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In recent years, the use of timber as a building material in larger construction applications such as multi-story buildings and bridges has increased. This requires a better understanding of the material to realize such constructions and design them more economically. However, accurate computational simulations of timber structures are challenging due to the complexity and inhomogeneity of this naturally grown material. It exhibits growth inhomogeneities such as knots and fiber deviations, orthotropic material behavior and moisture dependence of almost all physical parameters. Describing the creep response of wood under real climate conditions is particularly difficult. Changes in moisture content, plasticity and viscoelasticity affect moisture-induced stresses and potentially lead to cracks and structural damage. In this paper, we apply a material model that combines time and moisture-dependent behavior with multisurface plasticity to simulate cross-sections of different dimensions over a 14-month climate period. Our findings indicate that considering this long-term behavior has a minor impact on moisture-induced stresses during the drying period. However, during the wetting period, neglecting the time- and moisture-dependent material behavior of wood leads to a significant overestimation of tensile stresses within the cross-section, resulting in unrealistic predictions of wetting-induced fracture. Therefore, simulations during wetting periods require a sophisticated rheological model to properly reproduce the stress field.

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“…Besides, a moisture difference of 3 % already induced sufficient stress to initiate large cracks around the fully threaded screws or steel rods. Moreover, Huč et al ( 2020 ) determined that moisture-induced stresses caused by drying in glued laminated timber were greater than the limits of the tensile strength perpendicular to the grain of spruce wood. Further investigations of different climates on moisture-induced stresses were conducted by Angst and Malo ( 2012 ), where glulam cross sections were exposed to wetting and drying cycles during the experiments.…”

Section: Introductionmentioning

confidence: 99%

Prediction of moisture-induced cracks in wooden cross sections using finite element simulations

Brandstätter¹,

Autengruber²,

Lukacevic³

et al. 2023

Wood Sci Technol

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Wood absorbs and desorbs moisture due to its hygroscopic behavior, leading to moisture gradients in timber elements as well as swelling and shrinkage. These processes are constrained due to the orthotropic material properties of wood, leading to moisture-induced stresses, which can cause crack initiation and propagation. A significant amount of the damage in timber constructions indoors can be related to changes of the moisture content (MC). However, more information is needed about the correlation between moisture changes or gradients and specific damage characteristics, like crack depths. Thus, based on numerical simulations, the crack depth development within two solid timber and one glued laminated timber (GLT) cross section over time for different relative humidity (RH) reductions and initial MCs is analyzed. For this purpose, a multi-Fickian transport model is used to determine moisture fields, which are then used as loads in a subsequent stress simulation, where linear elastic material behavior is considered. An extended finite element approach, supported by a multisurface failure criterion defining the failure behavior, allows for the simulation of moisture-induced discrete cracking. Based on simulation results, correlations between potential maximum crack depths and moisture gradients in indoor climate conditions are derived, which enables the prediction of crack depths in wood. Finally, it is shown that the initial MC level significantly influences the maximum crack depth that can be expected.

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Numerical analysis of moisture-induced strains and stresses in glued-laminated timber

Cited by 8 publications

References 53 publications

Selected previous findings on the factors influencing the gluing quality of solid wood products in timber construction and possible developments: A review

Selected previous findings on the factors influencing the gluing quality of solid wood products in timber construction and possible developments: A review

Evaluation of Moisture-Induced Stresses in Wood Cross-Sections Determined with a Time-Dependent, Plastic Material Model during Long-Time Exposure

Prediction of moisture-induced cracks in wooden cross sections using finite element simulations

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