Shear strength of spruce glued—laminated timber beams

1985 ◽  
Vol 12 (3) ◽  
pp. 661-672 ◽  
Author(s):  
F. J. Keenan ◽  
J. Kryla ◽  
B. Kyokong
Keyword(s):  
Shear Strength ◽  
Cross Sections ◽  
Weibull Model ◽  
Longitudinal Shear ◽  
Douglas Fir ◽  
Published Data ◽  
Cross Sectional ◽  
Characteristic Value ◽  
Glued Laminated Timber ◽  
Timber Beams

The effect of size on longitudinal shear strength has been well established for Douglas-fir glued–laminated (glulam) timber beams. The present study examined whether this phenomenon exists in glulam beams made of spruce. The experiment consisted of three projects in which beams of various sizes were tested under concentrated mid-span load. The project A beams had clear spruce webs and white elm flanges with cross-sectional dimensions varying from 25 × 25 mm to 75 × 75 mm. The project B beams had spruce glulam webs with Douglas-fir flanges; cross sections ranged from 20 × 100 mm to 90 × 200 mm. In project C, three groups of 10 replications of commercially representative sizes of glulam beams were made from stiffness-rated spruce–pine–fir lumber. The beam cross sections were 76 × 200 mm, 76 × 400 mm, and 127 × 400 mm.The results indicated that depth, width, and shear plane had significant effects on the longitudinal shear strength of the beams in project A. Depth, width, and shear span of the small glulam beams in project B also had highly significant effects on shear strength. However, no effects of depth and width on the shear strength of glulam beams in project C were found. Regression analysis showed no dependence of shear strength on sheared volume for the beams of all three projects. The three-parameter Weibull model also failed to predict the near-minimum shear strength of spruce glulam beams. The results suggested that the lower-bound shear strength of spruce glulam beams is a constant (regardless of beam volume) and could be used as a single characteristic value for glulam design in shear. Further review of published data indicates that this may also be the case for Douglas-fir glulam but with a lower characteristic value than for spruce.

Deflection behavior and load-bearing period of structural glued laminated timber beams in fire including cooling phase

2018 ◽  
Vol 9 (4) ◽  
pp. 287-299
Author(s):  
Hitoshi Kinjo ◽  
Yusuke Katakura ◽  
Takeo Hirashima ◽  
Shuitsu Yusa ◽  
Kiyoshi Saito
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Shear Failure ◽  
Fire Performance ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Content Type ◽  
Glued Laminated Timber ◽  
Cooling Phase ◽  
Timber Beams

Purpose This paper aims to discuss the fire performance of glulam timber beams based on their deflection behavior and load-bearing period, which were obtained from load-bearing fire tests under constant load conditions. Design/methodology/approach In this report, the fire performance, primarily deflection behavior and load-bearing period of glued laminated (glulam) timber beams will be discussed from the standpoint of load-bearing fire tests conducted during the cooling phase under constant load conditions. Then, based on the charring depth and the per section temperature transformation obtained from loading test results, the load-bearing capacity of the glulam timber beams will be discussed using the effective section method and the strength reduction factor, which will be calculated in accordance with the European standards for the design of timber structures (Eurocode 5). Findings In the cooling phase, the charring rate is decreases. However, as the temperature in the cross section rises, the deflection is increases. The failure mode was bending failure because of tensile failure of the lamina at the bottom of the beam. Moreover, a gap caused by shear failure in a growth ring in the beam cross-section in the vicinity of the centroid axis was observed. Shear failure was observed up until 1 to 3 h before end of heating. The calculated shear strength far exceeded the test results. Shear strength for elevated temperature of glued laminated timber is likely to decrease than the shear strength in Eurocode 5. Originality/value Unlike other elements, a characteristic problem of timber elements is that their load-bearing capacity decreases as they are consumed in a fire, and their bearing capacities may continue to degrade even after the fuel in the room has been exhausted. Therefore, the structural fire performance of timber elements should be clarified during not only the heating phase but also the subsequent cooling phase. However, there are few reports on the load-bearing capacity of timber elements that take the cooling phase after a fire into consideration.

scholarly journals ANÁLISE DA UTILIZAÇÃO DE FIBRAS DE VIDRO EM VIGAS DE MADEIRA LAMINADA COLADA SUBMETIDAS À FLEXÃO SIMPLES

2017 ◽  
Vol 14 (1) ◽  
Author(s):  
Fernanda Lenzi ◽  
Paloma de Oliveira Matias ◽  
Adriano Vieira Risson
Keyword(s):  
Failure Mode ◽  
Glass Fibers ◽  
Wood Fiber ◽  
Reference Beam ◽  
Longitudinal Shear ◽  
Breaking Load ◽  
Maximum Increase ◽  
Reinforced Beams ◽  
Glued Laminated Timber ◽  
Timber Beams

RESUMO: A madeira apresenta boas propriedades mecânicas, porém há a necessidade de melhorias para que os elementos estruturais atendam as demandas solicitadas. Neste contexto, buscou-se com este trabalho analisar a utilização de fibras de vidro em vigas de madeira laminada colada submetidas à flexão simples para reforço estrutural, verificando o aumento de rigidez e resistência de seis vigas de madeira laminada colada através do adesivo Melamina Uréia Formaldeído MUF 1242 com o emulsificante líquido 2542, reforçadas com tecido unidirecional de fibra de vidro em conjunto com a resina epoxídica Compound, em comparação com uma viga de referência sem aplicação de reforço, assim como analisando a aderência entre o reforço e a superfície da madeira e também o modo de ruptura de cada viga. A aderência madeira-madeira e a aderência madeira-fibra demonstraram-se satisfatórias. Houve aumento quanto à rigidez das vigas reforçadas e quanto à carga de ruptura das mesmas, com um aumento máximo de 26,25% de carga de ruptura em relação à viga de referência. O modo de ruptura de todas as vigas deu-se por tração, sendo que em apenas uma viga não ocorreu cisalhamento longitudinal e em duas vigas houve esmagamento das lamelas superiores das vigas por compressão. A principal contribuição deste trabalho foi apresentar a viabilidade do uso de fibras de vidro como reforço para vigas de madeira laminada colada.ABSTRACT: The wood has good mechanical properties, but there is a need for improvements to the structural elements meet the demands requested. In this context, it sought this paper was to analyze the use of glass fibers in glued laminated timber beams subjected to simple bending for structural reinforcement, Verifying the increase of stiffness and strength of six laminated wood beams bonded through the adhesive Melamine Urea MUF 1242 with the liquid emulsifier 2542, reinforced with unidirectional fiberglass fabric together with epoxy resin Compound, comparing with a reference beam without reinforcement application, and also analyzing the adhesion between the reinforcement and the surface of the wood and the failure mode of each beam. The wood-wood grip and wood-fiber adhesion proved to be satisfactory. There was an increase in the stiffness of the reinforced beams and in the load of failure of the reinforced beams, with a maximum increase of 26.25% of breaking load in relation to the reference beam. The failure mode of all the beams occurred by traction, and in only one beam did not occur longitudinal shear and in two beams there was crushing of the upper lamellae of the beams by compression. The main contribution of this paper is to present the viability of using glass fibers as reinforcement for glued laminated timber beams.

Longitudinal shear in wood beams: a design method

1977 ◽  
Vol 4 (3) ◽  
pp. 363-370 ◽  
Author(s):  
Ricardo O. Foschi ◽  
J. David Barrett
Keyword(s):  
Shear Strength ◽  
Brittle Fracture ◽  
Design Method ◽  
Longitudinal Shear ◽  
Douglas Fir ◽  
Wood Beams

The results of a study on longitudinal shear strength of Douglas fir, based on Weibull's theory of brittle fracture, are implemented in a design method. Design formulae are given and required parameters are calculated for several common configurations of beams and loadings. A method for extending the results to other species is proposed.

Longitudinal shear strength of Douglas-fir

1976 ◽  
Vol 3 (2) ◽  
pp. 198-208 ◽  
Author(s):  
Ricardo O. Foschi ◽  
J. D. Barrett
Keyword(s):  
Shear Strength ◽  
Longitudinal Shear ◽  
Douglas Fir ◽  
Shear Stresses ◽  
Loading Conditions ◽  
Theoretical Predictions ◽  
The Difference ◽  
American Society ◽  
Shear Block

Weibull's theory of brittle fracture is applied to the determination of strength of Douglas-fir wood in longitudinal shear. Ultimate stresses, at a given survival probability, are derived for beams under different loading conditions. The theory allows an explanation for the difference in shear strength between beams and the standard American Society for Testing Materials shear block, as well as for the dependence of shear strength upon beam size. The theory is verified by comparing theoretical predictions and test results on Griplam nailed connections loaded parallel to the grain and shear tests on torque tubes. Very good agreement is shown. Finally, allowable shear stresses for beams under different loading conditions are derived.

Gender determination of caucasoid hair using image analysis

1993 ◽  
Vol 51 ◽  
pp. 216-217
Author(s):  
T.B. Ball ◽  
W.M. Hess
Keyword(s):  
Image Analysis ◽  
Cross Sections ◽  
Scalp Hair ◽  
The Body ◽  
Equivalent Diameter ◽  
Cross Sectional ◽  
Hair Samples ◽  
Length Width ◽  
Morphological Differences

It has been demonstrated that cross sections of bundles of hair can be effectively studied using image analysis. These studies can help to elucidate morphological differences of hair from one region of the body to another. The purpose of the present investigation was to use image analysis to determine whether morphological differences could be demonstrated between male and female human Caucasian terminal scalp hair.Hair samples were taken from the back of the head from 18 caucasoid males and 13 caucasoid females (Figs. 1-2). Bundles of 50 hairs were processed for cross-sectional examination and then analyzed using Prism Image Analysis software on a Macintosh llci computer. Twenty morphological parameters of size and shape were evaluated for each hair cross-section. The size parameters evaluated were area, convex area, perimeter, convex perimeter, length, breadth, fiber length, width, equivalent diameter, and inscribed radius. The shape parameters considered were formfactor, roundness, convexity, solidity, compactness, aspect ratio, elongation, curl, and fractal dimension.

Assessment of Knowledge and Practice of Various Eye Diseases in Sulaimani: A Descriptive Study

2018 ◽  
pp. 1-6
Author(s):  
Abdulrahman M. Ibrahem ◽  
Salah Q. Mahmood ◽  
Muhammed Babakir-Mina ◽  
Salar Ibrahim Ali ◽  
Bakhtyar Kamal Talabany
Keyword(s):  
Vision Loss ◽  
Good Practice ◽  
Study Data ◽  
Eye Diseases ◽  
Vision Impairment ◽  
P Value ◽  
Published Data ◽  
Knowledge Level ◽  
Cross Sectional ◽  
Knowledge And Practice

Knowledge and practice of public, especially patients about eye diseases are important to reduce magnitude of human blindness. Vision and sight are very essential because they allow us to connect to each other’s. In accordance to the recently published data; the estimation of 253 million people lives with vision impairment, 36 million are blind and 217 million suffer from moderate to severe vision impairment. A descriptive cross-sectional study was conducted at Shahid Dr. Aso Hospital in Sulaimani city-Iraq, from April to August 2017 by face-to-face interview through close ended questionnaire for data collecting. All data were analyzed by Statistical Package for Social Sciences version 22.0 software. P-value of < 0.05 was considered as a statistically significant. A total of 430 patients were randomly chosen to participate in the study. They were 254 (59.1%) males and 176 (40.9%) females. 76.7% of respondents was worrying about vision loss, 0.7% was worrying about hair loss. Of the participants, 32.8% was with a good knowledge level and 40.5% was with a poor knowledge level, as well as 3.1% was in a good practice and 58.8% was in a poor practice level. Female knowledge mean score was 9.53±4.96 and male knowledge mean score was 8.42±5.45, the practice mean score of males was 4.33±1.96 and mean practice score of females was 4.13±1.93. The study data indicate the worrying of participates about vision loss is in the highest proportion and the awareness and practice of patients about eye diseases is unsatisfactory. Health education campaigns are needed to improve personal awareness about vision related problems and for better eye health.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

Study on the strength of glued laminated timber beams with round holes: difference in structural performance between homogeneous-grade and heterogeneous-grade timber

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Shigefumi Okamoto ◽  
Nobuhiko Akiyama ◽  
Yasuhiro Araki ◽  
Kenji Aoki ◽  
Masahiro Inayama
Keyword(s):  
Scots Pine ◽  
Maximum Shear Stress ◽  
Material Strength ◽  
Laminated Beams ◽  
Strength Grade ◽  
Glued Laminated Timber ◽  
The Difference ◽  
Materials Used ◽  
Beam Height ◽  
Timber Beams

AbstractVarious design codes and design proposals have been proposed for glued laminated timber beams with round holes, assuming that the entire beam is composed of homogeneous-grade timber. However, in Japan, glued laminated timber composed of homogeneous-grade timber is rarely used for beams. In this study, the difference in the load-bearing capacity of glued laminated beams composed of homogeneous-grade timber and heterogeneous-grade timber with round holes when fractured by cracking was investigated experimentally and analytically. The materials used in the tests were glued laminated beams composed of homogeneous-grade Scots pine timber with a strength grade of E105-F345 and heterogeneous-grade Scots pine timber with a strength grade of E105-F300. Experiments confirmed that although the glued laminated beams composed of heterogeneous-grade timber have a lower material strength in the lamina with holes, its resistance to fracturing due to cracks associated with the holes is almost the same as that of the glued laminated beams composed of homogeneous-grade timber. The stresses acting on the holes in the laminated timber with holes of less than half the beam height were lower in the glued laminated beams composed of heterogeneous-grade timber than in the glued laminated beams composed of homogeneous-grade timber. The ratio of the stresses was found to be approximately equal to the ratio of the maximum bending stress or the maximum shear stress acting on the inner layer lamina, as determined by Bernoulli–Euler theory.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

Comparison of the Cross Sectional Area, the Loss in Volume and the Mechanical Properties of LAE442 and MgCa0.8 as Resorbable Magnesium Alloy Implants after 12 Months Implantation Duration

2010 ◽  
Vol 638-642 ◽  
pp. 675-680 ◽  
Author(s):  
Martina Thomann ◽  
Nina von der Höh ◽  
Dirk Bormann ◽  
Dina Rittershaus ◽  
C. Krause ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cross Sections ◽  
Degradation Process ◽  
Cross Sectional Area ◽  
Bending Test ◽  
Sectional Area ◽  
Cross Sectional ◽  
Initial Strength ◽  
Three Point Bending ◽  
The Cross

Current research focuses on magnesium based alloys in the course of searching a resorbable osteosynthetic material which provides sufficient mechanical properties besides a good biocompatibility. Previous studies reported on a favorable biocompatibility of the alloys LAE442 and MgCa0.8. The present study compared the degradation process of cylindrical LAE442 and MgCa0.8 implants after 12 months implantation duration. Therefore, 10 extruded implants (2.5 x 25 mm, cross sectional area 4.9 mm²) of both alloys were implanted into the medullary cavity of both tibiae of rabbits for 12 months. After euthanization, the right bone-implant-compound was scanned in a µ-computed tomograph (µCT80, ScancoMedical) and nine uniformly distributed cross-sections of each implant were used to determine the residual implants´ cross sectional area (Software AxioVisionRelease 4.5, Zeiss). Left implants were taken out of the bone carefully. After weighing, a three-point bending test was carried out. LAE442 implants degraded obviously slower and more homogeneously than MgCa0.8. The mean residual cross sectional area of LAE442 implants was 4.7 ± 0.07 mm². MgCa0.8 showed an area of only 2.18 ± 1.03 mm². In contrast, the loss in volume of LAE442 pins was more obvious. They lost 64 % of their initial weight. The volume of MgCa0.8 reduced clearly to 54.4 % which corresponds to the cross sectional area results. Three point bending tests revealed that LAE442 showed a loss in strength of 71.2 % while MgCa0.8 lost 85.6 % of its initial strength. All results indicated that LAE442 implants degraded slowly, probably due to the formation of a very obvious degradation layer. Degradation of MgCa0.8 implants was far advanced.

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