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.

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.

Effect of grain angle on shear strength of Douglas-fir wood

Holzforschung ◽  
2012 ◽  
Vol 66 (5) ◽  
pp. 655-658 ◽  
Author(s):  
Rakesh Gupta ◽  
Arijit Sinha
Keyword(s):  
Shear Strength ◽  
Root Mean Square ◽  
Failure Mode ◽  
Shear Plane ◽  
Douglas Fir ◽  
Mean Square ◽  
Rolling Shear ◽  
Grain Angle ◽  
Shear Block ◽  
The Relationship

Abstract The effect of grain angle (GA) on shear strength of Douglas-fir has been evaluated. Shear block specimens with a GA varying from 0 to 90° was loaded in the shear plane, resulting in failure mode transitioning from parallel to grain shear to rolling shear. As expected, shear strength decreased as the GA increased from 0° to 90°. A root-mean-square equation was found to be suitable to predict the relationship between GA and shear strength. Traditional Hankinson formula and the Tsai-Wu criteria were less effective with this regard.

ANALYSIS OF RESEARCH AND DESIGN MODELS FOR THE PUNCHNING SHEAR OF FLAT RC SLABS

2010 ◽  
Vol 2 (3) ◽  
pp. 93-100
Author(s):  
Gediminas Marčiukaitis ◽  
Remigijus Šalna
Keyword(s):  
Shear Strength ◽  
Theoretical Calculations ◽  
Theoretical Models ◽  
Complex Stress ◽  
Complex Stress State ◽  
Punching Shear ◽  
Shear Stresses ◽  
Test Results ◽  
Design Models ◽  
The Difference

The paper presents the review and analysis of the existing methods and models for calculating punching shear strength. The analysis of the existing design methods has showed that there is no unified theory about calculating punching shear strength. The models are similar in the way that fictitious shear stresses act in the fictitious shear area and are mainly obtained from the test results that may differ in their values. Therefore, the difference between the results obtained employing various calculation methods can be as high as 1,37 times, whereas the difference between the results of theoretical calculations and test research may vary up to 1,8 times. These facts clearly demonstrate that punching shear phenomena are not completely analyzed and require additional researches. The paper also proposes an in-deep analysis of famous analytical punching shear calculation models suggested within the last 50 years like Kinnunen and Nylander (1960), Moe (1961), Breastrup et al. (1976), Georgopoulos (1989), Broms (1990), Hallgren (1998), Menetrey (2002) and Theodorakopoulos (2002). The development of the above mentioned design models, the main assumptions and an algorithm for calculating punching shear strength are discussed in the article. The review of the existing models for calculating punching shear strength has also revealed that two main model types can be distinguished: type 1 – failure occurs when the compression zone is cut by shear and compression stress; type 2 – failure occurs when tensile stresses in concrete punching cone exceeds its tensile strength. A comparison between theoretical models and test results performed by different authors demonstrate that more accurate results can be obtained by calculating punching shear strength using the first types of models. The analysis has revealed it is purposeful to search for more effective reinforcing methods that can change the character of failure from brittle to plastic. A more effective replacement of reinforcement and the behaviour of concrete taking into account complex stress state in the failure zone should be applied.

Determination of Shear Stress in Pull out Tests in Laminated Bamboo Guadua angustifolia

2015 ◽  
Vol 668 ◽  
pp. 17-22 ◽  
Author(s):  
Caori Patricia Takeuchi ◽  
Martin Estrada ◽  
Dorian Luis Linero
Keyword(s):  
Shear Strength ◽  
Shear Stresses ◽  
Average Value ◽  
Pull Out ◽  
Laminated Bamboo ◽  
Tension Tests ◽  
Cross Section Area ◽  
Section Area ◽  
The Common

Specimens of laminated bamboo Guadua angustifolia do not usually fail due to fiber breakage when submitted to shear stresses. The common failure mechanism in that case is slippage in the fiber-matrix interface, accompanied by degradation of the lignin matrix (parenchyma). In this study the shear strength of laminated bamboo Guadua angustifolia specimens was determined by tension tests reducing the cross section area. The perimeter of the slipped area was determined using digital image processing. Shear stresses were calculated taking into account the load and slipped area in specimens of two different groups, depending on the orientation of the laminated boards. It was found that the average value of the shear strength on pull out tests were 2.9 MPa, which is a mechanical property of the material that is useful, for example, in the analysis of the behavior of the joints, and analysis of the fracture process.

In-Plane Shear Strength Determination of Composite Materials in Laminated and Sandwich Panels

1997 ◽  
Vol 50 (11S) ◽  
pp. S237-S240 ◽  
Author(s):  
J. R. Vinson
Keyword(s):  
Shear Strength ◽  
Composite Materials ◽  
Test Procedure ◽  
Sandwich Panels ◽  
Laminated Composite ◽  
Adhesive Bond ◽  
Shear Stresses ◽  
Plane Shear ◽  
Laminated Composite Materials

A simple test procedure is available to determine the in-plane shear strength of laminated composite materials, as well as other orthotropic and isotropic advanced material systems. The test apparatus is simple, inexpensive, and the flat rectangular plate test specimen is not restricted in size or aspect ratio. In addition to its use for laminated composite materials, the test can also be used for foam core sandwich panels. In sandwich panels, the tests can be used to determine the in-plane shear strength of the faces, the core and/or the adhesive bond between face and core. The shear stresses developed vary linearly in the thickness direction and are constant over the entire planform area.

Comparison of the TL-Shear Strength of Normal and Compression Wood of European Larch

Holzforschung ◽  
2003 ◽  
Vol 57 (4) ◽  
pp. 421-426 ◽  
Author(s):  
W. Gindl ◽  
A. A.Teischinger
Keyword(s):  
Shear Strength ◽  
Compression Wood ◽  
Fracture Behaviour ◽  
Microfibril Angle ◽  
Middle Lamella ◽  
Longitudinal Shear ◽  
Normal Wood ◽  
European Larch ◽  
The Difference ◽  
Scanning Electron

Summary The strength of larch compression wood specimens in longitudinal shear in the radial plane was determined and compared to normal wood. Fracture surfaces were examined with a scanning electron microscope. Compression wood showed higher shear strength than normal wood. The difference persisted after correction of the strength values for density. Scanning electron microscopy revealed clear differences in the pattern of failure in normal wood compared to compression wood. While transwall and intrawall fracture predominate in normal wood, intercell fracture at the middle lamella occurs in compression wood. An explanation of this change in fracture behaviour is proposed in terms of microfibril angle and lignification of the cell wall.

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.

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