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1.
This study established a prediction model for bending properties of glued-laminated timber (glulam) using optimized knot and
modulus of elasticity (MOE) distributions of lumber laminate as the main input variables. For this purpose, knot and MOE data
were investigated for all pieces of lumber that were prepared for glulam manufacturing, and statistical distributions of knot
size, knot number in one lumber, and MOE of each laminate were optimized as distribution functions. These knot and MOE data
were used as input variables in the prediction model for bending properties, and were also used in generating virtual glulam
using the inverse transform method. Prediction of bending properties for glulam was carried out using the transformed section
method, which is partially provided in ASTM D 3737 (Annex A4). Predicted values were compared with those from full-scale four-point
bending tests for 60 six-layered glulams with 10 different laminar combinations. Finally, the allowable bending properties
of glulam for each specific laminate combination were determined by calculating the fifth percentile of the modulus of rupture
and the average modulus of elasticity from virtual test results of more than 1000 virtual glulams. From the results of this
study, predicted bending properties for glulam and their distributions could be used for structural design in both allowable
stress design and limit state design. 相似文献
2.
《中国林业科技(英文版)》2010,(2):62-67
Structural finger-jointed (FJ) lumber was used mainly in structural applications including glue-laminated beams and wooden I-joists and more recently in parallel chord wood trusses. The paper evaluated strength properties of structural FJ lumber by three nondestructive methods (edge-wise bending, longitudinal and transversal vibration) in order to find an alternative to traditional evaluation methods. Lumber was sawn from the logs following a pattern typically used in China to maximize the volume of recover... 相似文献
3.
Kiyohiko Fujimoto Yasushi Hiramatsu Atsushi Miyatake Kenta Shindo Masahiko Karube Masaki Harada Seiichiro Ukyo 《Journal of Wood Science》2010,56(6):444-451
The object of this study was to investigate the strength properties of edge-glued laminae and to propose a suitable grading
method based on the lamina modulus of elasticity (MOE). Edge-glued laminae composed of lumber with similar MOEs (uniform laminae)
and edge-glued laminae produced by randomly gluing lumber independent of MOE (random laminae) were made from karamatsu (Larix kaempferi) lumber having the same thickness and length, but various widths. For both the uniform and random laminae, there was a strong
correlation between MOE values measured using the longitudinal vibration technique, the static bending test, and a grading
machine. The average values of bending, tensile, and compressive strengths of the uniform laminae were similar to those of
the random laminae. On the other hand, the average strength of laminae without end joints was significantly higher than that
of finger-jointed laminae for both uniform and random laminae. Finger-joints and knots played a significant role in the failure
of specimens, but the edge-gluing and the difference in MOE within an edge-glued lamina did not appear to affect the strength
properties. The bending, tensile, and compressive strengths of edge-glued laminae were strongly correlated to the lamina MOE. 相似文献
4.
无损检测技术评估规格材的性质 总被引:3,自引:1,他引:2
采用两种应力波设备对北美黄杉规格材进行抗弯强度性质的预测,分析规格材破坏模式,并讨论木材节子对规格材强度的影响。测试结果表明,动态与静态测试结果之间的相关程度较高。结构材的破坏模式主要为纹理断裂和脆性断裂;在规格材中间部位节子较多,且节子在规格材横断面上投影面积较大时,易发生脆性断裂。 相似文献
5.
Sung-Jun Pang Jung-Kwon Oh Jung-Pyo Hong Sang-Joon Lee Jun-Jae Lee 《Journal of Wood Science》2018,64(2):126-137
The aim of this study was to develop a stochastic model for predicting the bending strength distribution of glued-laminated timber (GLT). The developed model required the localized modulus of elasticity (MOE) and tensile strengths of laminae as input properties. The tensile strength was estimated using a regression model based on the localized MOEs and knot area ratios (KAR) which were experimentally measured for lamina grades samples. The localized MOE was obtained using a machine stress-rated grader, and the localized KAR was determined using an image-processing system. The bending strength distributions in four types of GLTs were simulated using the developed GLT beam model; these four types included: (1) GLT beams without finger joints; (2) GLT beams with finger joints; (3) GLT beams with different lamina sizes; and (4) GLT beams with different combinations of lamina grades. The simulated bending strength distributions were compared with actual test data of 2.4 and 4.8 m-long GLTs. The Kolmogorov–Smirnov goodness-of-fit tests showed that all of the simulated bending strength distributions agreed well with the test data. Especially, good agreement was shown in the fifth percentile point estimate of bending strength with the difference of approximately 1%. 相似文献
6.
四种方法测木质材料动弹性模量的对比研究 总被引:1,自引:0,他引:1
为寻找比较准确的估计木质材料静弹性模量的方法,以色木方材为例,采用纵向应力波、超声波、纵向共振和弯曲共振等4种方法检测41个无瑕疵试件的动弹性模量,采用静态载荷法测量其静弹性模量,并分析二者的相关性,采用配对t检验比较不同方法的差异。研究结果表明:四种方法测得的木质材料动弹性模量均高于其静弹性模量,但静、动弹性模量之间均呈显著的线性相关性,R2都大于0.7,因而四种方法都可以用来估计其静弹性模量。其中,弯曲共振法得到的样本试件动弹性模量与静弹性模量的差值均值最小,且相关性最高,因而运用弯曲共振法对木质材料静弹性模量进行估计最为准确,检测值也最接近静弹性模量值。 相似文献
7.
F. Lam Prof. Dr. R. O. Foschi Prof. Dr. J. D. Barrett Technician Q. Y. He 《Wood Science and Technology》1993,27(2):81-94
Summary A procedure has been developed to determine the cut-off frequency in an algorithm to evaluate the localized modulus of elasticity (MOE) in lumber. MOE profiles have been artificially generated to serve as input for evaluation of the procedure. A noise component has also been added to the input record to test the robustness and accuracy of the procedure. Good agreement between program predictions and the known localized MOE values has been obtained. The efficiency of the procedure has also been tested using MOE profiles collected from experiments. The program performed efficiently and program predictions seemed reasonable. 相似文献
8.
采用Pundit、Metriguard、FFT等三种无损检测方法和常规弯曲法对加拿大扭叶松(lodgepole pine)蓝变与非蓝变实木板材的动态及静态弹性模量进行检测和比较研究。结果表明,蓝变材三种动态弹性模量及静态弹性模量均高于非蓝变材;对比分析表明,蓝变材和非蓝变材的动态及静态弹性模量存在差异,其中动态弹性模量差异均达到0.01显著性水平,静态弹性模量差异达到0.05显著性水平,并且心、边材及密度值不同是导致以上差异的主要原因。相关性分析表明,动态与静态弹性模量间相关性达到0.01显著性水平;尽管三种无损检测方法测量结果存在差异,但它们之间仍存在密切相关性,FFT 技术测量的准确性高于Pundit和Metriguard;板材中结子数影响木材动态和静态弹性模量,随着板材结子数增加弹性模量相应地降低。 相似文献
9.
Song-Yung Wang Cheng-Jung Lin Chih-Ming Chiu Jin-Hau Chen Te-Hsin Yung 《Journal of Wood Science》2005,51(1):1-6
The effects of different thinning and pruning methods on the bending strength and dynamic modulus of elasticity (DMOE) of young Taiwania (Taiwania cryptomerioides Hay) were investigated. The average DMOE, modulus of elasticity (MOE), and modulus of rupture (MOR) in the thinning treatments showed the following trend: no thinning > medium thinning > heavy thinning. This indicates that thinning reduces average bending properties. The average DMOE, MOE, and MOR in the pruning treatments showed the following trend: medium pruning > no pruning > heavy pruning. According to this tendency, better average qualities of lumber and specimens were from wood subjected to no-thinning and medium-pruning treatments according to an ultrasonic wave technique and static bending tests. However, most results showed no statistically significant differences among thinning, pruning, and thinning and pruning treatments. The average values of DMOE, MOE, and MOR of visually graded construction-grade lumber were significantly greater than those of below-grade lumber. Moreover, there were very significant positive relationships between density, ultrasonic velocity, DMOE, MOE, and MOR, although the determination coefficients were small. 相似文献
10.
11.
LIN Lanying FU Feng Research Institute of Wood Industry Chinese Academy of Forestry Beijing China 《中国林业科技(英文版)》2007,6(3):17-25
Resonance flexural vibration(Fast Fourier Transform, FFT), ultrasonic wave(Pundit) and stress wave(Metriguard) techniques were examined as means of evaluating the static modulus of elasticity (MOE) and predicting the modulus of rupture (MOR) of finger-jointed lumber specimens made with four kinds of Eucalyptus (Eucalyptus. citriodora, E. exserta, E. grandis x E. urophylla and E. grandis). Dynamic MOE was calculated from frequency and time obtained from forced vibrations and sounds induced in the four species of finger-jointed specimens. It was found that correlation coefficients between density and static MOE and dynamic MOE were statistically significant at the 0.01 level. And it was also found that the three nondestructive techniques can provide rapid and accurate means to determine the MOE, and the dynamic MOE was more accurate to predict static MOE than density. But the correlation coefficient between dynamic MOE, static MOE and MOR were lower than results reported by other researchers for solid wood, and were not statistically significant. It can be concluded that the three nondestructive techniques are useful for evaluating the MOE, but not suitable for predicting the MOR of finger-jointed. 相似文献
12.
利用超声波检测杉木抗弯弹性模量 总被引:7,自引:0,他引:7
以大尺寸杉木板材为研究对象,通过超声波测试仪对其动态弹性模量进行无损检测及用微机控制电子式木材万能试验机测试其静曲弹性模量,并分析了两种试验方法测定结果之间的关系。结果表明:(1)杉木板材的静曲弹性模量E1和动态弹性模量E2之间呈线性相关,不同厚度的试样无论是作为独立样本还是合并成总体样本空间,其相关性都非常显著,相关系数为0.75~0.95;(2)各种规格的杉木静曲弹性模量平均值E1与动态弹性模量平均值E2的比值E1/E2受杉木板材的厚度影响较小,其值为0.768~0.837。 相似文献
13.
基于单片机的单板层积材弹性模量的无损检测 总被引:2,自引:1,他引:1
笔者介绍了以A1、89C51单片机为核心,应用应力波法测量单板层积材的弹性模量;构建了由加速度传感器、信号调理电路、峰值检测和保持电路、数字处理及显示电路、单片机等组成的测量系统,用以测定单板层积材的动态弹性模量.将动态弹性模量试验数据与力学试验机所测静态弹性模量相比较,得出二者具有显著的相关性,相关系数达到0.9以上.基于单片机的应力波法检测单板层积材的弹性模量,具有尢损、设备简单、成本低,测量效率高等特点,适用于单板层积材的实时在线检测,有较好的应用前景. 相似文献
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15.
弹性模量是人造板重要的力学性能指标之一,它是表征人造板刚度性能的重要指标,与其他的力学指标也有密切的关系,直接影响人造板的使用.对国内外人造板弹性模量的检测方法及其研究现状进行了归纳总结,指出振动、应力波、机械应力等无损检测方法是今后发展方向之一. 相似文献
16.
Models for predicting lumber bending MOR and MOE based on tree and stand characteristics in black spruce 总被引:1,自引:0,他引:1
In this study, a stepwise method was introduced to identify the best variables for predicting lumber static bending modulus of elasticity (MOE) and modulus of rupture (MOR) based on stand and tree characteristics in black spruce (Picea mariana). In the initial development of the technique, the two equations were fitted independently using ordinary least squares (OLS). A test for cross-equation correlation using black spruce data showed highly significant correlation between the two equations. Since the cross-equation correlation exists between the two equations, more efficient parameter estimation can be achieved through joint-generalized least squares, better known as seemingly unrelated regression (SUR). A simultaneous system of two equations was derived for black spruce. The two methods were evaluated and compared for some statistical parameters. The results indicated that there is a small difference between the two methods, but parameter estimates from seemingly unrelated regression estimation had smaller standard errors in all cases as compared to those from ordinary least squares estimates. Therefore, the system estimation methods theoretically perform better for simultaneously interdependent systems of equations and the appropriate system estimation approaches are recommended for estimating coefficients in simultaneously interdependent systems of forestry equations. 相似文献
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18.
This study investigated near-infrared spectroscopy (NIRS) to rapidly estimate physical and mechanical properties of No. 2 2 × 4 southern pine lumber. A total of 718 lumber samples were acquired from six mills across the Southeast and destructively tested in bending. From each piece of lumber, a 25-mm-length block was cut and diffuse reflectance NIR spectra were collected from the transverse face using a FOSS 5000 scanning spectrometer. Calibrations were created using partial least squares (PLS) regression and their performance checked with a prediction set. Overall moderate predictive ability was found between NIRS and the properties for the calibration and prediction sets: block specific gravity (SG) (R 2 = 0.66 and R p 2 = 0.63), lumber SG (0.54 and 0.53), modulus of elasticity (MOE) (0.54 and 0.58), and modulus of rupture (MOR) (0.5 and 0.4). Model performance for MOE (R p 2 = 0.70) and MOR (R p 2 = 0.50) improved when performing PLS regression on a matrix containing lumber SG and NIR spectra. Overall NIRS predicted MOE better than linear models using lumber SG (R 2 = 0.46), whereas lumber SG (R 2 = 0.51) predicted MOR better than NIRS. Overall NIRS has reasonably good predictive ability considering the small volume of wood that is scanned with the instrument. 相似文献
19.
三种典型竹质工程材料纵向弹性模量评价 总被引:1,自引:1,他引:0
以重组竹、竹束单板层积材(BLVL)、竹集成材为代表的竹质工程材料受到越来越多的关注和应用。文中采用超声波法、自由横向振动法和力学法分别对上述3种典型竹质工程材料的纵向动态弹性模量(MOE)进行评价比较,结果表明,横向自由振动法能较为快速、准确和无损地评价出竹质工程材料的MOE,MOE的变异系数与其自身铺装结构有关;重组竹、BLVL和竹集成材的一阶共振频率分别为455.73、380.41和487.62 Hz;超声波在竹集成材的纵向上传播速度最快,重组竹其次,BLVL最慢;三点弯曲力学测试发现3种竹质工程材料的断裂模式不同,全顺向的重组竹为竹纤维拉断和界面剪切破坏,纵横组坯的BLVL为横向竹束拉断以及竹/木复合界面分层,而更多体现实竹性能的竹集成材为底层竹材维管束拉断和拔出破坏,其断裂载荷为重组竹> BLVL >竹集成材,而断裂位移为竹集成材> BLVL >重组竹。 相似文献