In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform...In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform lateral load simulated using a gasbag.The investigation involved the performance of light frame wood structure after it experienced the repeated cyclic lateral wind load as well as the performance of the structure under the ultimate lateral load.Then,the study verified that light frame wood structure can resist repeated cyclic wind loads without observable degradation in stiffness during the anticipated serve life,and recommended shear wall percent drift restriction for lateral wind load design of wood structure in serviceability limit states is 1/400 drift,and in ultimate limit states is 1/80 drift.The conclusions of this paper can be benefit for the engineering practice of the light frame wood structures in high wind load regions.展开更多
Wood is a green material in line with the sustainable development strategy.From the excellent performance of engineering wood products,modern wood structures represented by light wood structures have gained more devel...Wood is a green material in line with the sustainable development strategy.From the excellent performance of engineering wood products,modern wood structures represented by light wood structures have gained more development opportunities.As an indispensable part of light wood structure systems,the wood-frame shear wall plays a vital role in the bearing capacity and earthquake resistance of light wood structure systems.This paper is focused on a review of the lateral performance of wood-frame shear walls and classifies the influencing factors in relevant experimental research into three categories,including internal factors such as shear wall structure,external factors such as test scheme,and other factors of material production and test process.Finally,the research prospects in this field were introduced based on the summary of the research status.This work can be a reference for further research on the lateral performance of wood-frame shear walls.展开更多
In this study, tubular pinewood (Pinus sylvestris L.) specimens are tested and shear strain measurements are performed by applying torsion in z direction in the consideration of light weight aircraft engineering. The ...In this study, tubular pinewood (Pinus sylvestris L.) specimens are tested and shear strain measurements are performed by applying torsion in z direction in the consideration of light weight aircraft engineering. The objective of this paper is to contribute and generate the nonlinear material model in terms of shear modulus presented with power functions under the consideration of nonlinear behavior of wood under torque. Strain gauge measurements are performed for the maximum shear stresses which develop on the tubular specimen, along the radial r(rin, rout), circumferential Φ(Φin, Φout) and z directions, in a point-wise manner. The data is gathered and examined for the determination of the local variations of empirical shear modulus functions on transversely isotropic surfaces of the specimens. The coordinate dependent shear modulus functions of GzΦ(r), GzΦ(Φ), GzΦ(z) are derived for GzΦ(r, Φ, z)as the function of r, Φ and z, respectively, by analyzing the gathered data. It is proposed to represent the shear modulus functions, GzΦ(Φ) and GzΦ(z) with the parabolic polynomials, and, to represent the shear modulus function GzΦ(r) with a linear equation.展开更多
The effects of photostabilizers of ultraviolet absorbers （UVA）, hindered amine light stabilizer （HALS） and pigment on surface color change and mechanical properties of weathered wood-flour/ polyethylene （HDPE） c...The effects of photostabilizers of ultraviolet absorbers （UVA）, hindered amine light stabilizer （HALS） and pigment on surface color change and mechanical properties of weathered wood-flour/ polyethylene （HDPE） composites were investigated. After being added UVA with high UV absorbance, the WPC exhibites better ability to resist color fading and mechanical property loss. High molecular weight HALS is found to be the most effective in controlling long term fading and yellowing changes. Pigments cover the composites for remaining the original color after weathering regardless of less contribution to mechanical property. Addition of photostabilizer and pigment together show great synergism in decreasing color fading and flexural property loss.展开更多
Quercus gambelii (Gambel’s oak) communities are found in the mountains of the western United States from Wyoming, Colorado, and Utah south into northern Mexico. Leaf gas exchange rates were measured for potential suc...Quercus gambelii (Gambel’s oak) communities are found in the mountains of the western United States from Wyoming, Colorado, and Utah south into northern Mexico. Leaf gas exchange rates were measured for potential successional species in Q. gambelii communities. Daily average light level below the canopy was 125 μmol/m2/sec. Light response curves indicated that Pinus ponderosa and Q. gambelii had high maximum photosynthetic rates (14.13 and 11.21 μmol/m2/sec) and were sun species. Abies concolor (white fir) is a shade species with the lowest photosynthetic rate (3.71 μmol/m2/sec). At low light levels few differences in photosynthetic rates were found between the species. Pinus ponderosa and Q. gambelii maximum photosynthetic rates were reduced 71% - 73% in shade and the shade species maximum photosynthetic rates were reduced by 50% - 57%. Comparing annual gas exchange rates for all species showed that A. concolor had higher gas exchange rates and could replace Q. gambelii. Growth in height of Q. gambelii was a second order quadratic function reaching a plateau of about ten meters between 80 and 95 years. Growth estimates of height of A. concolor in canopy shade were exponential, which would allow seedlings to reach the Q. gambelii canopy in approximately 35 years. Abies concolor wood specific gravity is 56% lower than Q. gambelii, which means more carbon is put into growth in height to reach the canopy at low light levels and low photosynthetic rates. The additional shading it causes would further reduce Q. gambelii photosynthesis rates and prevent self-replacement in these Q. gambelii communities, leading to an A. concolor dominated community.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No. 50508012)
文摘In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform lateral load simulated using a gasbag.The investigation involved the performance of light frame wood structure after it experienced the repeated cyclic lateral wind load as well as the performance of the structure under the ultimate lateral load.Then,the study verified that light frame wood structure can resist repeated cyclic wind loads without observable degradation in stiffness during the anticipated serve life,and recommended shear wall percent drift restriction for lateral wind load design of wood structure in serviceability limit states is 1/400 drift,and in ultimate limit states is 1/80 drift.The conclusions of this paper can be benefit for the engineering practice of the light frame wood structures in high wind load regions.
基金This work was supported by the National Natural Science Foundation of China(Nos.51878354&51308301)the Natural Science Foundation of Jiangsu Province(Nos.BK20181402&BK20130978)333 Talent High-Level Project of Jiangsu Province,and Qinglan Project of Jiangsu Higher Education Institutions.Any research results expressed in this paper are those of the writer(s)and do not necessarily reflect the views of the foundations.
文摘Wood is a green material in line with the sustainable development strategy.From the excellent performance of engineering wood products,modern wood structures represented by light wood structures have gained more development opportunities.As an indispensable part of light wood structure systems,the wood-frame shear wall plays a vital role in the bearing capacity and earthquake resistance of light wood structure systems.This paper is focused on a review of the lateral performance of wood-frame shear walls and classifies the influencing factors in relevant experimental research into three categories,including internal factors such as shear wall structure,external factors such as test scheme,and other factors of material production and test process.Finally,the research prospects in this field were introduced based on the summary of the research status.This work can be a reference for further research on the lateral performance of wood-frame shear walls.
文摘In this study, tubular pinewood (Pinus sylvestris L.) specimens are tested and shear strain measurements are performed by applying torsion in z direction in the consideration of light weight aircraft engineering. The objective of this paper is to contribute and generate the nonlinear material model in terms of shear modulus presented with power functions under the consideration of nonlinear behavior of wood under torque. Strain gauge measurements are performed for the maximum shear stresses which develop on the tubular specimen, along the radial r(rin, rout), circumferential Φ(Φin, Φout) and z directions, in a point-wise manner. The data is gathered and examined for the determination of the local variations of empirical shear modulus functions on transversely isotropic surfaces of the specimens. The coordinate dependent shear modulus functions of GzΦ(r), GzΦ(Φ), GzΦ(z) are derived for GzΦ(r, Φ, z)as the function of r, Φ and z, respectively, by analyzing the gathered data. It is proposed to represent the shear modulus functions, GzΦ(Φ) and GzΦ(z) with the parabolic polynomials, and, to represent the shear modulus function GzΦ(r) with a linear equation.
文摘The effects of photostabilizers of ultraviolet absorbers （UVA）, hindered amine light stabilizer （HALS） and pigment on surface color change and mechanical properties of weathered wood-flour/ polyethylene （HDPE） composites were investigated. After being added UVA with high UV absorbance, the WPC exhibites better ability to resist color fading and mechanical property loss. High molecular weight HALS is found to be the most effective in controlling long term fading and yellowing changes. Pigments cover the composites for remaining the original color after weathering regardless of less contribution to mechanical property. Addition of photostabilizer and pigment together show great synergism in decreasing color fading and flexural property loss.
文摘Quercus gambelii (Gambel’s oak) communities are found in the mountains of the western United States from Wyoming, Colorado, and Utah south into northern Mexico. Leaf gas exchange rates were measured for potential successional species in Q. gambelii communities. Daily average light level below the canopy was 125 μmol/m2/sec. Light response curves indicated that Pinus ponderosa and Q. gambelii had high maximum photosynthetic rates (14.13 and 11.21 μmol/m2/sec) and were sun species. Abies concolor (white fir) is a shade species with the lowest photosynthetic rate (3.71 μmol/m2/sec). At low light levels few differences in photosynthetic rates were found between the species. Pinus ponderosa and Q. gambelii maximum photosynthetic rates were reduced 71% - 73% in shade and the shade species maximum photosynthetic rates were reduced by 50% - 57%. Comparing annual gas exchange rates for all species showed that A. concolor had higher gas exchange rates and could replace Q. gambelii. Growth in height of Q. gambelii was a second order quadratic function reaching a plateau of about ten meters between 80 and 95 years. Growth estimates of height of A. concolor in canopy shade were exponential, which would allow seedlings to reach the Q. gambelii canopy in approximately 35 years. Abies concolor wood specific gravity is 56% lower than Q. gambelii, which means more carbon is put into growth in height to reach the canopy at low light levels and low photosynthetic rates. The additional shading it causes would further reduce Q. gambelii photosynthesis rates and prevent self-replacement in these Q. gambelii communities, leading to an A. concolor dominated community.
