Hygrothermal Effects on Load‐Duration Behavior of Structural Lumber

Fridley, Kenneth J.; Tang, R. C.; Soltis, Lawrence A.; Yoo, Chai H.

doi:10.1061/(asce)0733-9445(1992)118:4(1023)

Cited by 28 publications

(7 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Indeed the hygroscopic nature of wood can lead to dimensional variations of the elements in service, with possible deformations, disconnections or occurrence of internal stresses due to constrained swelling or shrinkage strains [14], resulting eventually in loss of structural integrity and the development of cracks. Moreover, most physical and mechanical properties of the material are affected by wood MC [15]; [16], and the long-term performance of timber elements, both in terms of load bearing behavior (i.e., creep) [17]; [18]; [19] and durability [20]; [21], can be negatively influenced by prolonged exposure to a humid microclimate. As a note related to the rheological behaviour of wood, it is worth mentioning that traditionally, it was very common to build timber structures using green wood; significant deflections can be therefore found in heritage timber structures, as a result of creep of timbers loaded while green.…”

mentioning

confidence: 99%

Assessment of heritage timber structures: Review of standards, guidelines and procedures

Riggio

D’Ayala

Parisi

et al. 2018

Journal of Cultural Heritage

View full text Add to dashboard Cite

This paper reviews the official documentation (standards, guidelines and procedures) available for the assessment of heritage timber structures. The subsequent discussion does not catalogue all relevant technical literature. Instead, it intends to convey the state of background knowledge, recommendations and code rules using some illustrative examples. A specific focus is given to visual inspection as a fundamental first step for all different scopes and levels of assessment. The objectives of this review are to: 1) highlight the gaps and limitations in the currently available tools as well as the need for standardization; 2) contribute to the definition of an ontological approach, Highlights • A review of the methodological, normative and operational tools for the assessment of heritage timber structures. • A critical discussion of the gaps and limitations of current assessment tools. • An introduction to a proposed inspection form for heritage timber roofs.

show abstract

mentioning

confidence: 99%

Assessment of heritage timber structures: Review of standards, guidelines and procedures

Riggio

D’Ayala

Parisi

et al. 2018

Journal of Cultural Heritage

View full text Add to dashboard Cite

show abstract

“…Varios estudios analizan el efecto de la temperatura en las propiedades mecáni-cas de la madera. A modo de ejemplo se puede mencionar a Fridley et al (1989), quienes mostraron que el tiempo de falla del material disminuye con el aumento de la temperatura a una misma carga. Por otro lado, Placet et al (2008) mostraron que la rigidez de la madera disminuye signi cativamente a temperaturas superiores a los 80ºC.…”

Section: Fluencia Y Relajación En La Maderaunclassified

Análisis del comportamiento reológico y termo-higromecánico en probetas de tableros tensados de madera para puentes a condiciones ambientales variables

Figueroa¹,

Bustos²,

Dechent³

et al. 2012

Maderas, Cienc. tecnol.

View full text Add to dashboard Cite

RESUMENLa madera presenta un comportamiento termo-higromecánico cuando se somete a la acción conjunta de variaciones de temperatura, humedad relativa y carga mecánica. Los tableros tensados de madera presentan pérdidas de fuerza en la barra de tensado debido principalmente a la relajación de la tensión y a la contracción de la madera, aumentando con los cambios de humedad y temperatura de ésta. El objetivo de este estudio fue estudiar el comportamiento reológico de tableros tensados de madera de pino radiata (Pinus radiata D. Don) sometidos a cambios de temperatura y humedad relativa. Un total de 16 probetas fueron previamente tratadas con diferentes tratamientos de preservación, las cuales fueron sometidas a cuatro ciclos de temperatura y humedad relativa en una cámara de clima. La deformación de las probetas y la tensión de las barras de acero fueron medidas. Los resultados mostraron que la variación de la temperatura y de la humedad tiene una fuerte in uencia en la variación de la tensión de las barras tensoras. Los retensados minimizaron la pérdida de tensión de las barras. Además, no se observaron evidencias de uencia termo-higromecánica ni relajación de la tensión de las muestras de puentes tensados en este estudio.Palabras clave: Puentes tensados, tensión en las barras, tratamientos de preservación, Pinus radiata D.Don. ABSTRACTWood material has a thermo-hygromechanical behaviour because its deformation depends on the combined action of temperature, relative humidity and mechanical load variations. Stresslaminated timber bridge deck show a reduction of stress in the tension bars mainly due to the relaxation and shrinkage of wood, increasing with moisture content and temperature changes within the wood. e aim of this research was to study the rheological behavior of stress-laminated timber bridge deck samples under temperature and relative humidity variations. A total of 16 samples were previously treated with four types of preservative treatments, which were subjected to four cycles of temperature and relative humidity in a climate chamber. Wood samples deformation and stress in the steel bars were measured. e results showed a signi cant stress reduction in the steel bar during

show abstract

“…Some researchers carried out a number of experiments to determine the constant and cyclic temperature, and cyclic relative humidity effects on load-duration behavior of timber, and they thereby proposed some modified models such as the model under constant temperature, cyclic temperature and hygrothermal changes. Fridley [9] developed the cumulative damage model of timber subjected to cyclic hygrothermal environment:…”

Section: Cumulative Damage Model Of Structural Timbermentioning

confidence: 99%

“…C 1 , C 2 , C 3 and C 4 are the coefficients given by Ref. [9]. θ and ω are the temperature and moisture content factors respectively, t θ and t ω are times associated with the temperature or moisture change, respectively, ω and θ are two parameters to describe the time rate of change of the temperature and moisture factors.…”

Section: Cumulative Damage Model Of Structural Timbermentioning

confidence: 99%

“…They believed that when the stress level is less than the threshold ratio, the time-related effect should not be considered. Fridley et al carried out some experiments on sawn larch to study constant temperature [6] , cyclic temperature [7] , cyclic relative humidity [8] and hygrothermal effects [9] on load-duration behavior of timber and obtained corresponding models. Recently, Qu et al [10] has applied the models to predict the residual service-life of a timber structure.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Long-term cumulative damage model of historical timber member under varying hygrothermal environment

Wang

2009

Wuhan Univ. J. Nat. Sci.

View full text Add to dashboard Cite

A long-term damage cumulative model for the duration of load effect of structural timber is proposed in this paper, which is economical in analysis as well as involving long-term hygrothermal effect. Based on the Miner linear damage cumulative theory, the cumulative damage model is applied to analyze the annual hygrothermal, daily cyclic thermal and daily cyclic relative humidity's effect on load-duration behavior and to calculate the sum of damage in one year. The results indicate that the annual and daily hygrothermal effect should be taken into consideration when calculating the damage accumulation, in which the influence levels from large to small are annual hygrothermal, daily relative humidity and daily thermal effect. Considering both annual and daily hygrothermal variations as external loads the long-term model is determined. Its application to service-life prediction of a historic timber structure verifies the feasibility and high-efficiency of the proposed approach.The strength of structural timber can be affected by both the intensity and the duration of loads, which is often referred to as the duration of load (DOL) effect. It is actually induced by the 'creep-rupture' phenomena of the wood material. Owing to the creep, the deformation of the structural timber under loading induce plastic deformation, which cannot restore and increase continuously until the wood fiber ruptures, thereby causing the reduction in the strength of wood [1] .The DOL effect is a major and difficult issue in the research of wood science. It causes the reduction in the strength of wood material and thereby induces the substantial deformation of the structures constructed by timbers. In some historic buildings the structural timber is repaired or replaced due to the large deformation instead of the lack of material strength. For example in the Tai-he Palace in the Summer Palace, the large flexibility of a timber beam induced the drop of the swallowtail by about 10-11.5 cm [2] . Similar observations are also reported in other historic buildings. Therefore, in the research on the security assessment and residual service-life prediction of historic buildings, the DOL effect is one of the major factors. Many experimental programs have focused on DOL effects in full-size timbers and various cumulative damage models have been proposed. Gerhards et al [3] first applied the Miner linear cumulative damage theory to evaluate the time-related effect of loading on the strength of sawn larch under constant environment. Barrett et al [4] and Foschi et al [5] revised the WANG Xueliang et al : Long-Term Cumulative Damage Model of … 431 model and proposed a threshold ratio for stress level. They believed that when the stress level is less than the threshold ratio, the time-related effect should not be considered. Fridley et al carried out some experiments on sawn larch to study constant temperature [6] , cyclic temperature [7] , cyclic relative humidity [8] and hygrothermal effects [9] on load-duration behavior of timber and obtained correspond...

show abstract

Hygrothermal Effects on Load‐Duration Behavior of Structural Lumber

Cited by 28 publications

References 9 publications

Assessment of heritage timber structures: Review of standards, guidelines and procedures

Assessment of heritage timber structures: Review of standards, guidelines and procedures

Análisis del comportamiento reológico y termo-higromecánico en probetas de tableros tensados de madera para puentes a condiciones ambientales variables

Long-term cumulative damage model of historical timber member under varying hygrothermal environment

Contact Info

Product

Resources

About