Numerical hygro-thermal analysis of coated wooden bridge members exposed to Northern European climates

Fortino, Stefania; Hradil, Petr; Genoese, Alessandra; Pousette, Anna

doi:10.1016/j.conbuildmat.2019.03.012

Cited by 28 publications

(31 citation statements)

References 27 publications

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“…Due to increasingly larger cross sectional dimensions of timber construction, recently published studies on moisture behavior deal with the topic of moisture penetration into wood depending on a variable environmental climate over time, which leads to moisture gradients. For this topic extensive work is available, especially based on numerical studies, Fortino et al (2019), Fragiacomo et al (2011). It should be noted that the numerical investigations of the deformation states (moisture distribution and internal cross sectional stress) always use well known shrinkage and swelling coefficients, which were determined on small specimens under uniform homogeneous moisture fields.…”

Section: Related Work In Wood Materials Sciencementioning

confidence: 99%

Determination of the moisture change behavior of cross-laminated timber using an optical flow based computer vision technique

Hofinger

Pock

Moosbrugger³

2019

Wood Material Science & Engineering

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Although cross-laminated timber (CLT) offers greatly improved directional stability against moisture changes compared to lumber, some layup dependent directional differences still remain. Furthermore, even under a purely homogeneous distributed moisture change strong deformations appear along the boundaries, which show a decrease of swelling/shrinkage towards the inside of CLT panels. Metrological determination of this behavior is still a challenging task and involves longlasting moisture content conditioning and typically manual measurements. This limits the amount of measurable data-points and thus the gain-able insights. We apply a recently introduced computer vision technique based on optical flow from scan images to measure surface deformation fields of various CLT specimens with different layups. This allows us to measure the change of average differential swelling and shrinkage coefficients throughout the cross section and visualize them as curves with high resolution. We gain measurements for each image pixel and demonstrate good matching to previously published manual single-point measurements. Furthermore, we analyze various specimens specifically built to allow for investigations of the aforementioned boundary effects. Using the computer vision approach we are able to show how the combination of homogeneous deformations and boundary effects leads to the resulting deformations observable with manual methods.

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Section: Related Work In Wood Materials Sciencementioning

confidence: 99%

Determination of the moisture change behavior of cross-laminated timber using an optical flow based computer vision technique

Hofinger

Pock

Moosbrugger³

2019

Wood Material Science & Engineering

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“…The moisture content (MC) accumulated in wood for longer periods may cause, in combination with certain temperatures, conditions suitable for biodegradation of the primary material. The longterm mechanical deterioration of wood driven by cyclic variations of the environmental conditions is a challenging topic for timber bridges (Fortino et al 2013a(Fortino et al , 2019 because of the rheological properties of timber characterized mainly by mechanosorptive and viscoelastic creep. Peaks of air relative humidity (RH) above 80% in combination with high RH daily variations can cause high moisture gradients with consequent development of additional internal stresses in timber structures (Fragiacomo et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…A multi-Fickian model with wood hysteresis for timber structures subjected to continuously varying environmental conditions was implemented and tested for glulam beams of timber bridges under Southern European climates with temperature above zero degrees Celsius in Fortino et al (2013a). More recently, a multi-Fickian model with sorption dependency on temperatures above and below zero but without wood hysteresis was specialized for coated bridge components under Northern European climates in Fortino et al (2019). Recently, there was an increasing use of multi-Fickian models for hygro-mechanical analysis of wood (Huc et al 2018, Konopka andKaliske 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Recently, there was an increasing use of multi-Fickian models for hygro-mechanical analysis of wood (Huc et al 2018, Konopka andKaliske 2018). However, to the knowledge of the authors, the large beams of timber bridges were analysed by a three-dimensional multi-Fickian modelling only in Fortino et al (2013aFortino et al ( , 2019 and the related literature by the same authors.…”

Section: Introductionmentioning

confidence: 99%

“…The moisture-induced strains and stresses are calculated during 10 years of service life. It should be noted that the numerical model is intentionally prepared with the highest possible surface emission (uncoated wood surface) (see Fortino et al 2019), in order to assess the effects of moisture variation on timber bridges exposed to severe environmental condition without any chemical treatment. Therefore, the main aim of the study is to present the results of a refined numerical analysis to evaluate the impact of moisture content on the safety and serviceability level of timber bridge elements in term of induced stresses and deflection.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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Three-dimensional orthotropic nonlinear transient moisture simulation for wood: analysis on the effect of scanning curves and nonlinearity

et al. 2020

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This paper introduces, with the development of user-subroutines in the finite-element software Abaqus FEA®, a new practical analysis tool to simulate transient nonlinear moisture transport in wood. The tool is used to revisit the calibration of moisture simulations prior to the simulation of mechanical behaviour in bending subjected to climate change. Often, this calibration does not receive sufficient attention, since the properties and mechanical behaviour are strongly moisture dependent. The calibration of the moisture transport simulation is made with the average volumetric mass data experimentally obtained on a paired specimen of Norway spruce (Picea abies) with the dimensions $$30\times 15\times 640\, {\mathrm{mm}}^{3}$$ 30 × 15 × 640 mm 3 . The data, from a 90-day period, were measured under a constant temperature of 60 °C and systematic relative humidity cycles between 40 and 80%. A practical method based on analytical expressions was used to incorporate hysteresis and scanning behaviour at the boundary surface. The simulation tool makes the single-Fickian model and Neumann boundary condition readily available and the simulations more flexible to different uses. It also allows for a smoother description of inhomogeneity of material. The analysis from the calibration showed that scanning curves associated with hysteresis cannot be neglected in the simulation. The nonlinearity of the analysis indicated that a coherent set of moisture dependent diffusion and surface emission coefficient is necessary for the correct description of moisture gradients and mass transport.

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Numerical hygro-thermal analysis of coated wooden bridge members exposed to Northern European climates

Cited by 28 publications

References 27 publications

Determination of the moisture change behavior of cross-laminated timber using an optical flow based computer vision technique

Determination of the moisture change behavior of cross-laminated timber using an optical flow based computer vision technique

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

Three-dimensional orthotropic nonlinear transient moisture simulation for wood: analysis on the effect of scanning curves and nonlinearity

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