Random field-based modeling of size effect on the longitudinal tensile strength of clear timber

Moshtaghin, Alireza Farajzadeh; Franke, Steffen; Keller, Thomas; Vassilopoulos, Anastasios P.

doi:10.1016/j.strusafe.2015.09.002

Cited by 7 publications

(3 citation statements)

References 35 publications

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“…It is important to highlight that besides the cross-sectional area, the length of the specimens influences the timber compressive and tensile strengths parallel to grain (Fryer et al 2018;Moshtaghin et al 2016a;Showalter et al 1987;Totsuka et al 2022). In particular, several studies (Moshtaghin et al 2016b;Showalter et al 1987) proposed models to consider the size effects on timber tensile strength, which are based on the weakest link theory for brittle failures. However, the possible effect of the specimen length on the reduction of timber strength at elevated temperatures was not statistically significant in the data set collected in the present study.…”

Section: Data On Temperature-dependent Materials Strength Of Timbermentioning

confidence: 99%

Probabilistic Models for Temperature-Dependent Compressive and Tensile Strengths of Timber

2023

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Reliable reduction factors for timber mechanical properties at elevated temperatures are needed to design timber structures for fire safety as well as to assess the safety of historic timber structures against fire hazards. In this paper, a compilation of the available data on the compressive and tensile strengths of timber at elevated temperatures is carried out. Then, a probabilistic modeling approach to predict the temperature-dependent reduction factors applicable to fire design is proposed. The collected data cover both solid and engineered timber at temperatures from 20°C to 300°C, with a variety of sample sizes, wood species, test protocols, and moisture content used in the experiments. The data revealed a large scatter in elevated temperature strengths, and a large conservativeness of the relationships of the current European standard, which is commonly used for the advanced design of timber structures under fire. To address this variability, multiple probability density functions were calibrated across the temperature range, quantifying the goodness of fit with statistical criteria. Two-parameter Weibull functions provided the best fit, and continuous temperature-dependent relationships were derived for the parameters of the distribution. The proposed probabilistic models can be implemented in a numerical code, facilitating their use in analytical and computational approaches, and can be applied to the probabilistic assessment of the structural performance and reliability of timber structures against fire.

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Section: Data On Temperature-dependent Materials Strength Of Timbermentioning

confidence: 99%

Probabilistic Models for Temperature-Dependent Compressive and Tensile Strengths of Timber

2023

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“…Few works have been focused on the spatial variability of timber structures. Moshtaghin et al [13,26] performed an experimental characterization of the longitudinal mechanical properties (elastic modulus and compressive strength) of light wood at different scales. They found that the dimension of the specimens should be carefully selected to avoid scale effects.…”

Section: Introductionmentioning

confidence: 99%

Spatial Variability of Ozigo Wood Beams under Long-Term Loadings in Various Environmental Exposures

et al. 2021

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Timber is a renewable material that should be more used for sustainable construction. While the mechanical behavior and durability of some species have been widely studied in the past, few studies are available for the Ozigo (Dacryodes buettneri) specie. This paper deals with the spatial variability of Ozigo beams subjected to long-term loadings and different environmental conditions. These beams were previously subjected to long-term creep in three environments (air-conditioned, unsheltered, and sheltered) at Masuku in the south-east of Gabon. Various specimens were extracted from these beams to determine its moisture content and subjected to three-point bending tests to obtain the modulus of elasticity and failure stress at various points in the space. The results obtained showed that, after long-term loadings, environmental exposure combined with mechanical loading, play a key role in the mechanical properties of the timber beams. A reduction of strength was found for the specimens extracted from the unsheltered and sheltered outdoor exposures in comparison with those extracted from the air-conditioned exposure. Concerning the spatial variability, statistical tests confirm that there is significant spatial correlation. It was also found that the spatial variation of properties in the beam is not stationary because it was affected by loading and support conditions.

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“…The limiting distribution for the fracture stress, which is identical to the first asymptotic distribution of the smallest values, was derived on the basis of the chain-of-bundles probability model. Moshtaghin et al [23] presented a random field-based size effect model based on the weakest-link theory to predict the longitudinal tensile strength of clear timber.…”

Section: Introductionmentioning

confidence: 99%

Reliability Analysis of CFRP-Strengthened RC Bridges Considering Size Effect of CFRP

Xie

Wang

2019

Materials

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A reliability analysis of an existing structure and a carbon fiber-reinforced plastic (CFRP)-strengthened structure is commonly used to evaluate the effectiveness of strengthening. It also provides the basis for the calibration of the partial factors involved in strengthening design codes. As the fundamental data, the statistical characteristics of the CFRP tensile strength affect the evaluation result. In general, the statistical characteristics of the CFRP strength were obtained from laboratory experiments with small-scale specimens, which resulted in errors caused by the size effect. In this study, a probabilistic series-parallel model is developed to describe the size effect of CFRP. The CFRP fabric is divided into a set of representative volume elements. By numerically simulating the CFRP strength, the relationship between the number of representative volume elements and the mean and coefficient of variation (COV) of the CFRP strength is analyzed. A chi-square test is carried out to determine the distribution type of the CFRP strength. An analytical expression of the mean, COV, and the cumulated density function of the CFRP strength are derived. Finally, an existing bridge, which has operated for 41 years, is selected for the case study; it is strengthened by using CFRP fabric. Reliability indexes of the existing and the strengthened bridges are calculated to analyze the size effect on the reliability of the strengthened structure.

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Random field-based modeling of size effect on the longitudinal tensile strength of clear timber

Cited by 7 publications

References 35 publications

Probabilistic Models for Temperature-Dependent Compressive and Tensile Strengths of Timber

Probabilistic Models for Temperature-Dependent Compressive and Tensile Strengths of Timber

Spatial Variability of Ozigo Wood Beams under Long-Term Loadings in Various Environmental Exposures

Reliability Analysis of CFRP-Strengthened RC Bridges Considering Size Effect of CFRP

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