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United StatesDepartment ofAgriculture Performance ofForest Service
ForestProducts
Red Maple GlulamLaboratory
ResearchPaperFPL-RP-519
Timber BeamsHarvey B. ManbeckJohn J. JanowlakPaul R. BlankenhornPeter LaboskyRussell C. MoodyRoland Hernandez
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Abstract
A red maple glued-laminated (glulam) beam combi-nation that would achieve a design bending stress of2,400 lb/in2 (16.5 MPa) and modulus of elasticity of1.8 × 106 lb/in2 (12.4 GPa) was developed; 45 beamswere evaluated. The properties of the lumber gradesused in the layup and their placement within the beamswere closely monitored during beam fabrication. An-other 166 specimens of end-jointed lumber were gath-ered during manufacture to relate the individual tensilestrength performance of end joints to their performancein the beams. The evaluations of the end-jointed spec-imens and the full-sized beams indicate that a glulambeam combination with the targeted design stress inbending and modulus of elasticity is possible.
Contents
Page
Keywords: Glued-laminated beams, hardwood,modeling, red maple
May 1993
Manbeck, Harvey B.; Janowiak, John J.; Blankenhorn, PaulR.; Labosky, Peter; Moody, Russell C.; Hernandez, Roland.1993. Red maple glulam timber beam performance. Res.Pap. FPL-RP-519. Madison, WI: U.S. Department ofAgriculture, Forest Service, Forest Products Laboratory.30 p.
A limited number of free copies of this publicationare available to the public from the Forest ProductsLaboratory, One Gifford Pinchot Drive, Madison, WI53705-2398. Laboratory publications are sent to more than1,000 libraries in the United States and elsewhere.
The Forest Products Laboratory is maintained incooperation with the University of Wisconsin.
Introduction . . . . . . . . . . . . . . . . .
Objective and scope . . . . . . . . . . . . . .
Design of beam combinations . . . . . . . . . . .
Procedures for grading lumberand characterizing knots . . . . . . . . . . .
Lumber sawing and grading . . . . . . . . .
Measurement of lumber MOE . . . . . . . .
Characterization of knot properties . . . . . .
Beam and end-jointed lumber tests . . . . . . .
Procedures . . . . . . . . . . . . . . . . .
Beam test results . . . . . . . . . . . . . .
End-jointed lumber tests . . . . . . . . . . .
Analysis . . . . . . . . . . . . . . . . . . .
Effect of beam size . . . . . . . . . . . . .
Design levels . . . . . . . . . . . . . . . .
Comparison with predicted values . . . . . . .
Comparison of beam and end-jointbending strength . . . . . . . . . . . . .
Conclusions . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . .
Appendix A . . . . . . . . . . . . . . . . .
Appendix B . . . . . . . . . . . . . . . . .
Appendix C . . . . . . . . . . . . . . . . .
Appendix D . . . . . . . . . . . . . . . . .
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Red Maple Glulam TimberBeam Performance
Harvey B. Manbeck, Professor, Department of Agricultural Engineering
John J. Janowiak, Assistant Professor of Wood Products
Paul R. Blankenhorn, Professor of Wood Technology
Peter Labosky, Professor of Wood Science and Technology
Pennsylvania State University, University Park, Pennsylvania
Russell C. Moody, Supervisory Research General Engineer
Roland Hernandez, Research General Engineer
Forest Products Laboratory, Madison, Wisconsin
Introduction
Red maple is rapidly becoming a predominant hard-wood species in the forests of the Northeastern UnitedStates. Because this species has not been tradition-ally considered for structural applications, there hasbeen little interest in developing engineered red mapleproducts. The emerging prominence of red maple inthe forests makes product development of vital interestto landowners and to wood processors, fabricators, anddesigners.
Red maple has excellent mechanical properties, treatswell, and has good gluing characteristics (FPL 1987).Thus, it is a good candidate for structural applicationssuch as glued-laminated (glulam) timber beams. TheAmerican Institute of Timber Construction (AITC)established specifications for hardwood glulam timberin AITC 119 (AITC 1985). However, red maple is notincluded as a candidate species for lamination stock.Moreover, this specification provides conservativedesign properties of homogeneous combinations ofhardwood and does not provide options for developingefficient combinations of glulam timber. Consequently,a cooperative research project was conducted betweenthe Pennsylvania State University and the USDAForest Service, Forest Products Laboratory to developefficient combinations of red maple glulam timber. Thetarget design stresses for these combinations were2,400 lb/in2 in bending stress and 1.8 × 106 lb/in2
in modulus of elasticity (MOE). (See Table 1 for SIconversion factors.)
The research reported here was sponsored and fundedby the Pennsylvania Department of Transportation(Project No. SS-043), the Pennsylvania AgricultureExperiment Station, and the U.S. Department
of Agriculture, Forest Service, Forest ProductsLaboratory.
Objective and Scope
The objectives of the research described in this reportwere as follows:
1. to develop a red maple glulam timber beamcombination with a target bending design stresslevel of 2,400 lb/in2 and MOE of 1.8 × 106 lb/in2
2. to establish the technical basis for developingallowable properties for bending strength and MOEof red maple glulam beams
3. to determine if calculation procedures outlined inthe American Society for Testing and Materials(ASTM) D 3737 (ASTM 1991a) can be used topredict bending strength and stiffness of red mapleglulam beams
We expected that successful completion of theobjectives would provide data to support includingred maple in glulam timber design specifications.In addition, the procedures developed could pro-vide the glulam timber industry with better meth-ods for developing more efficient hardwood glulamtimber beam designs than does the current standardAITC 119 (AITC 1985).
The scope of the study included (1) design of beamcombinations, (2) sawing, drying, grading, andcharacterization of properties of a large sample of redmaple structural lumber, (3) manufacture of 45 glulamtimber beams, and (4) evaluation of beam bendingstrength and stiffness.
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Results of the laboratory tests of the lumber specimenswill be used to develop input lumber propertiesrequired by advanced probabilistic models (Hernandezand others 1992). Laboratory test results for end-jointed lumber are presented in this report becausethey are critical for the development of a glulamstandard. Results of the glulam beam modeling willbe presented in a separate report.
Design of Beam Combinations
2.0-1/31.8-1/3
No. 2
1.8-1/32.0-1/6
2.0-1/3
1.8-1/3
No. 2
1.8-1/3
2.0-1/6
Glulam beam combinations were designed on the basisof assumed lumber properties of red maple lumber,current surveys of mechanical properties of existingred maple lumber, and procedures established in theASTM D 3737 Standard (ASTM 1991a). The proposedbeam combinations targeted a design bending stress of2,400 lb/in2 and MOE of 1.8 × 106 lb/in2.
The lamination material consisted of E-rated grades oflumber for the outer laminations and visually gradedlumber for the core laminations. The beams contained2.0E material in the outer zones, 1.8E material inthe next inner zones, and No. 2 material in the corelaminations. Edge knots for the lumber grades used forthe two zones on the compression side of the beams andfor the next inner zone on the tension side were limitedto one-third the area of the cross section (two-thirdsclear lumber). This represents No. 2 or better lumberand is designated in the text as 2.0-1/3 lumber for theouter zone and 1.8-1/3 lumber for the next inner zone.The E-rated lumber in the outer tension zone had anedge-knot limitation of one-sixth of the cross section(five-sixths clear lumber) (designated 2.0-1/6 lumber).
Three beam combinations were developed and fab-ricated to represent critical beam sizes with small,medium, and large dimensions (Fig. 1). The smallestbeam (8-Lam) had eight laminations with finished di-mensions of 3 in. wide by 12 in. deep by 20 ft long.The intermediate beam (12-Lam) had 12 laminationswith dimensions of 5 in. wide by 18 in. deep by 30 ftlong. The largest beam (16-Lam) had 16 laminationswith dimensions of 6.75 in. wide by 24 in. deep by40 ft long. The beams were manufactured using nomi-nal 2 by 4, 2 by 6, and 2 by 8 lumber, respectively (1.5by 3.5 in., 1.5 by 5.5 in., and 1.5 by 7.25 in., respec-tively).
The target beam MOE of 1.8 × 106 lb/in2 requiredcertain MOE levels of laminating lumber. To determineif the current resource of red maple structural lumberwould provide adequate yields of the desired E-ratedgrades, preliminary results of ongoing research studiesat both Pennsylvania State University (Janowiak andothers 1992) and the Forest Products Laboratory
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8-Lam3-in. width
12-in. depth20-ft length
12-Lam5-in. width
18-in. depth30-ft length
16-Lam6.75-in. width24-in. depth40-ft length
2.0-1/3
1.8-1/3
No. 2
1.8-113
2.0-1/6
Figure 1—Red maple glulam beam combina-tions. Location of various lumber grades for 8-,12-, and 16-lamination beams.
(FPL) were reviewed. The MOE data indicatedthat the proposed E-rated grades of 2.0-1/6, 2.0-1/3,and 1.8-1/3 could be readily derived from availablered maple lumber populations. Also, results of theknot analysis from the independent sample of redmaple lumber indicated that the lumber quality wasadequate to achieve the targeted 2,400-lb/in2 designbending stress (Green and McDonald, in preparation).Therefore, assumed properties were used to develop theglulam beam combinations (Table 2).
To develop glulam beam combinations that wouldachieve the target bending stress of 2,400 lb/in2,several assumptions were necessary to estimate theminimum strength ratio, the bending stress indices(clear wood stress), and the knot properties required bythe ASTM D 3737 Standard (ASTM 1991a). Values forthe minimum strength ratios of the candidate grades ofred maple were estimated from values established forE-rated lumber across all species in AITC 117 (AITC1979). Bending stress indices for the proposed E-ratedgrades were those recommended by ASTM D 3737.Finally, conservative estimates of knot propertiesrequired by ASTM D 3737 procedures were derivedfor each proposed lumber grade using actual knotmeasurements obtained on an independent sample ofSelect Structural (SS), No. 2, and No. 3 grades of redmaple lumber (Green and McDonald, in preparation).The visually graded lumber was graded accordingto inspection rules established by the NortheasternLumber Manufacturers Association (NELMA 1986).
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To achieve the bending stresses predicted with theASTM D 3737 procedures, special grades of lumberwere required in the outer 5 percent of the tensionlaminations (e.g., 5 percent of 16 laminations equaled1 lamination). In this study, one 2.0-1/6 laminationof the red maple combinations was replaced witha lamination meeting the special criteria given inTable 3. These special grades, referred to as tensionlamination grades, were developed following ASTMD 3737. For each beam size, a sample of 15 beamswas selected, which is statistically significant for a10-percent difference in strength properties with a90-percent level of confidence.
Procedures for Grading Lumberand Characterizing Knots
Lumber Sawing and Grading
Lumber for manufacturing glulam beams was obtainedby sawing red maple (Acer rubrum) logs into green8/4 (2-in.) dimensional material. The lumber wasconditioned at a commercial facility, using a predrier,to moisture content of approximately 16 to 18 percentover a 6-week period. Once the target moisture contentlevel was reached, the material was rough-planed toa thickness of 1.75 in. The rough-sawn lumber wasthen visually graded by NELMA rules and subdividedinto Select Structural, No. 1, No. 2, and No. 3 grades(NELMA 1986). The lumber was subsequently shippedto the laminator. Total processed log volume was33.1 × 103 board feet (fbm).
The sawing yielded approximately 4,700, 6,650, and14,100 fbm of 2 by 4, 2 by 6, and 2 by 8 material,respectively. These board footage values were basedon two independent sawmill runs. The first sawmillrun was based on a higher proportion of lower gradelogs, which resulted in poor lumber recovery yieldfor the larger 2 by 8 material. The second run wasmore heavily predisposed to No. 1 and veneer-gradelogs, which enhanced 2 by 8 recovery. Logs in eitherprocessing run were sawn leaving the center log portionin the form of 4 by 4 or larger cants. Yields of thevarious grades were as follows: SS, 32.0 percent;No. 1, 28.7 percent; No. 2, 34.3 percent; No. 3,2.8 percent; and cull, 1.7 percent. These yields werebiased with respect to sawing practices and removal ofcant log sections to minimize the inclusion of juvenilewood.
Measurement of Lumber MOE
Stiffness was measured once the lumber attained anaverage moisture content of 15 percent. The long-span
flatwise bending MOE was measured using a deflectionapparatus with the following specifications:
• steel strongback support assembly equipped withradius supports
• mechanical lever crane for applying a constant148-lb load
• calibrated linear variable differential transformer(LVDT) for measuring midspan displacement
• digital voltmeter for reading output transducervoltage
• portable laptop computer for data entry and storageand MOE computation
The 8- and 10-ft-long lumber was tested over a 7.5-and 9.5-ft span, respectively, using a simply supported,center-point loading configuration. No shear correctionwas made for the apparent MOE calculation as a resultof the large span-to-depth ratio. The results of theMOE tests were used to sort the lumber using thecriteria listed in Table 4.
The SS and No. 1 material was initially sorted to the2.0-1/6, 2.0-1/3, or 1.8-1/3 grades using these criteria.Material that did not meet the criteria was either notused (higher stiffness) or added to the No. 2 grade(lower stiffness). The No. 2 material was then sortedto obtain additional amounts of 2.0-1/3 and 1.8-1/3material. It was expected that much of the No. 2material would not meet these grades and would beused in the beam core. The sorting of the SS and No. 1grades provided nearly all the E-rated material.
Although the lumber samples that were measured forMOE were large, we wanted to determine the aver-age MOE for the lumber specimens that actually ap-peared in the beam layups. We were able to do thisbecause the location of these specimens was specificallymapped. The MOE averages for the lumber that ap-peared in the beam layups are presented in Table 5.These results show that the average stiffness values ofthe 2.0E and 1.8E lumber for each size were slightlylower than the target values. Conversely, the averagestiffness of the No. 2 lumber for each size significantlyexceeded the value of 1.5 × 106 lb/in2 assumed inTable 2.
Characterization of Knot Properties
To accurately analyze the beams for bending strengthusing the ASTM D 3737 (ASTM 1991a) procedures,knots were measured for each grade of lumber afterthe lumber was sorted by MOE. Knots were measuredby estimating an equivalent “straight-through” knotand determining the percentage of the lumber cross-section that the knots occupied. The knot properties
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were measured for all the tension lamination materialand for representative samples of the remaininglumber grades. Knot data were analyzed following theprinciples in USDA Technical Bulletin 1069 (Freas andSelbo 1954).
The knot properties calculated from the knot measure-ments are listed in Table 6. The data were based on aminimum of 1,000 lineal fbm examined for each lamina-tion grade for the three lumber widths combined.
Beam and End-JointedLumber Tests
Forty-five beams (15 of each combination) weremanufactured along with extra specimens for end-jointed lumber tests. The location of each lumberpiece was recorded on prepared beam maps so thatthe lumber properties could later be related to beamperformance. In addition, the quality of the criticaltension laminations was assessed in relation to theallowable knot and slope-of-grain properties, todetermine the relative qualities of the beams.
Procedures
Manufacture of the beams followed the normalproduction procedures (ANSI 1983). Each grade oflumber included a range of qualities permitted bythe grade. Lumber quality was random; the lumberwas not sorted to include high as opposed to lowquality material in any specific arrangement alongthe lamination length. The general manufacturingprocedure was as follows:
1. Lumber pieces were continuously finger-jointed,with the lamination ribbon cut to beam length.Vertically oriented finger-joints were manufacturedwith a melamine–formaldehyde adhesive underradio-frequency cure. Special outer-zone laminationswere manufactured first, followed by production ofcore plies to develop the beam depth profile. End-joint geometry was finger length, 1.03 in.; pitch,0.25 in.; and tip thickness, about 0.03 in. Theobserved tip gap was approximately 0.038 in.
2. Laminations were planed prior to adhesive appli-cation for face bonding. Initial lamination thick-ness was reduced to 1.5 in. by removing 0.13 in. ofmaterial from both faces.
3. The adhesive resin for face lamination was a room-temperature curing resorcinol-formaldehyde.Adhesive application was through a single gluelinewith an 80.lb/1,000-ft2 spread rate. Surfaceadhesive was spread with a roll-coat applicator.Open assembly time was not modified from that
typically used within the operation for SouthernPine beam fabrication. Total closed-assembly timeto applied clamp pressure was approximately50 min. Clamp pressure was similar to that usedfor Southern Pine fabrication.
4. Adhesive cure was at ambient temperature (75°F to80°F) under pressure for a minimum 12-h period.Beams were dressed to a surface finish acceptableunder the category of industrial grade glulam.
Following manufacture, the beams were visuallyinspected to assure conformance to ANSI A190.1(ANSI 1983) and to determine the relative qualitiesof the tension laminations in the midlength regionsubjected to >85 percent of the maximum momentduring test. Using the maximum allowable strength-reducing characteristics listed in Table 3, a relativerating system was developed to systematically assigna quality to the tension lamination. Table 7 lists theallowable percentages of lumber cross-sectional areasthat can be occupied by knots, the slope-of-grainlimitations, and the MOE restrictions for classificationof low, medium, or high quality.
Beam Test Results
Inspection of the beams following manufacture revealedthat two beams (beams RM8-5 and RM8-9) in the16-Lam group had end joints in adjacent laminations inthe outer tension zone spaced closer than the 6 in. re-quired by ANSI A190.1 (ANSI 1983). Also, one beamof each combination had a tension lamination thatdid not meet the visual criteria of Table 3 (beamsRM4-3, RM6-5, and RM8-10). However, the des-ignated compression side of the two smaller beams(RM4-3 and RM6-5) met the criteria, and they weretested with the tension and compression sides reversed(these were balanced combinations). It was not possibleto test the third beam (RM8-10) as a result of both theunbalanced layup of the 16-Lam beam and the qualityof the compression-side lamination. Therefore, althoughthe 15 beams in the 16-Lam group were tested, only12 were included in the final analysis.
The percentage of beams categorized as havinglow, medium, or high quality tension laminations isshown in Table 8. Additional details on the qualityof the individual tension laminations are provided inAppendix A.
All the full-sized glulam beams were tested followingthe procedures given in the ASTM Standard D198(ASTM 1991b). The loading configuration used to testthe full-sized beams is illustrated in Figure 2. Physicalproperties (moisture content, weight, and dimensions),stiffness properties (full-span deflections), and failure
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Figure 2—Loading configurations for bendingtests
load were measured for each beam. In addition, noteswere taken on failures, typical failure types werephotographed, and high-speed videotapes were madeof failures on selected beams. Moisture contents weremeasured with a resistance-type moisture meter nearthe midspan of all laminations after ultimate failure ofthe beams. Weights were measured on a mobile scale tothe nearest 10-lb increment. Dimensions were measuredat each load point.
During the application of load, beam deflections weremeasured using a precision rule (0.02-in. markings)attached to the beam. Deflections were recorded atmid-depth with respect to a stringline attached overeach support. The readings were taken at specifiedload increments with the use of a surveyor’s scope;this allowed the recorder to take readings to thenearest 0.01 in. During the load-deflection readings,elapsed time readings were also taken. The purposefor the elapsed time readings was to record wheninitial cracking occurred (noise) and when compressionwrinkling was first detected. The time-of-occurrencereadings were then traced back to applied load.
After the beams failed, detailed descriptions of thefailure propagations were recorded (Fig. 3), alongwith an assessment of the cause of failure (end joint,
Figure 3—Mapping of failure propagations inglulam beams. (M91 0266-50)
Figure 4—Cumulative distribution of modulus ofrupture (MOR) for three sizes of glulam beams.
knot, etc.). Each beam failure was photographed forfuture reference. Modulus of rupture (MOR) and MOEwere calculated using standard flexural formulas. Deadload stress was included in the MOR calculations. TheMOE values were calculated based on the slope of theload-deflection curve determined by a linear regressionup to design load.
Strength and StiffnessResults of the bending tests on the beams are sum-marized in Table 9. Individual beam results are givenin Appendix B. Figure 4 compares the cumulativedistribution function of MOR for the 8-, 12-, and16-lamination beams.
Beam FailureMost beams failed abruptly at ultimate load and manyemitted cracking sounds as the ultimate load wasapproached. Several beams exhibited compression
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wrinkling at or between the load points prior to max-imum load. All beams ruptured throughout the tensionzone near or within the constant moment region. Al-though it was not possible to positively identify the ini-tial point of failure for all beams, estimates were madeof the mechanism that triggered the initial cause of fail-ure. These results are summarized in Table 10. Beamfailures are described in detail in Appendixes B and C.
Most beams failed through either clear wood orslope-of-grain regions in the tension laminations.The failure of up to two beams in each group wasattributed solely to the finger joints, whereas severalother beams failed by a combination of end jointswith other characteristics. About one-half the beamsexhibited areas of shallow or little wood failure at thebonds between laminations as the rupture progressed.These failures are referred to as glueline failures(GLF) in Appendix B. Although these face bondswere not believed to affect the beam strength, theycould hamper long-term durability. The face bondsare not perceived to be critical in the development ofcommercial red maple glulam lumber. Examination ofthe failed glueline areas suggested that the problemof durability may well be resolved through slightmodification of the lamination assembly, such as slowerplaning speeds and higher face-bonding pressures(private conversation with Bryan River, ResearchForest Products Technologist, FPL).
End-Jointed Lumber Tests
End-jointed lumber specimens from each grade and sizewere tested in tension. The test specimens were 8-ftlong with the end joint located near midspan. Prior totesting, specimens were face- and edge-planed to thesame dimensions of the laminating lumber used in theglulam beams.
For the purpose of characterizing lumber propertiesfor probabilistic models (Hernandez and others 1992),short-span stiffness properties were obtained on the2-ft lumber segment on each side of the joint and onthe 2-ft segment across the joint. These bending testswere conducted on a screw-driven bending machinewith a load cell and LVDT setup for measuring theshear-free deflections between the load points. Theloading configuration for the bending test was 5.5 ftbetween the supports and 2 ft between the appliedload points. Load-deflection readings were taken in5-lb increments. The 2 by 4 specimens were loaded toa maximum load of 300 lb and the 2 by 6 and 2 by 8specimens to a maximum load of 400 lb. The MOEvalues were calculated using the slope of the load-deflection readings.
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Figure 5—Cumulative distribution of tensilestrength of finger-jointed 2.0E-1/6 grade lumberfor nominal 2 by 4, 2 by 6, and 2 by 8 material.
After the nondestructive static bending tests, thespecimens were tested to failure in tension accordingto the procedures specified in the ASTM StandardD 198 (ASTM 1991b), which specify a 5- to 10-mintime-to-failure. Normal quality control practices fortesting end joints would follow the AITC 200 (1991a)procedures, which specify a 2-min time-to-failure. Endjoints for this research project were tested according tothe ASTM D 198 (ASTM 1991b) procedures as a resultof the similar failure times of the full-sized beams. Thetension testing machine was adjusted such that thegrips were 30 in. apart. The specimens were placedin the machine with end joints located near the centerof the 30-in. span. A 30-in. span was used because ofthe minimum span limitations of the tension machine;thus, the 24-in. segment tested in bending was centeredwithin the 30-in. span. After testing, the short-spanstiffness data and the visual grade of the end-jointspecimens between the grips were used to reclassifythe end joints with respect to grade. The strengthand stiffness data provided information to relate therelationship of the individual performance of end jointsto their performance in the beams.
Results of tension tests on the end-jointed tensionlamination material are given in Table 11 and shown inFigure 5. Results on tests of the other grades of fingerjoints are in Appendix D.
Analysis
The glulam beam strength and stiffness results inTable 9 were calculated assuming both the normaland lognormal distributions. However, to analyzethe data, the ASTM D 3737 Standard (ASTM1991a) recommends that a lognormal distribution be
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used. Therefore, our analysis assumes a lognormaldistribution.
Effect of Beam Size
By evaluating three beam sizes, it was possible todetermine if beam volume exerted a significant effect onthe strength of red maple beams. The results indicatedthat the small beams (8-Lam) had significantly higherstrength than the other two sizes (Table 9). However,there was no significant difference between the strengthof the other two sizes (12- and 16-Lam). The followingequation is used in the National Design Specificationfor Structural Wood (NFPA 1991) to account for theeffect of varying beam size on bending strength.
(1)
Figure 6—Variation in beam MOR with beamvolume showing a line approximating anexponent of 0.071.
where
b is beam width (in.),
L beam length (ft), and
d beam depth (in.)
and x, y, and z are exponents that determine therelative adjustments for width, length, and depth.
was conducted. First, the ratio between the volumeeffect factors of each beam size was determined usingboth the 1/10 and 1/20 exponents. Next, the ratio be-tween the averages of the various paired groupings ofbeams were determined along with a confidence inter-val using the procedures described in Appendix II of anFPL report (Wolfe and Moody 1978). Table 12 lists theresults of this analysis.
When width, depth, and length are combined to obtainvolume, the following relationship is used in place of
These results indicate that neither exponent can be
Equation (1) (assuming x = y = z).statistically rejected because predicted results usingboth exponents fell within the confidence interval.
where
(2)
V0 is standard volume (5.125 in. by 12 in. by 21 ft)
For the comparison of the 16- and 12-Lam beams, thepredicted results with the 1/10 exponent were at theedge of the confidence interval whereas those with the1/20 exponent were near the middle of the confidenceinterval.
V volume of actual beam (b by d by L)
k exponent that represents x = y = z
Moody and others (1988, 1990) found that exponents ofx = y = z = 1/10 adequately explained the variationin strength for Douglas-fir beams. A volume effectequation has been adopted by ASTM CommitteeSection D07.02.02 with exponents x = y = z = 1/10for all species. The American Institute of TimberConstruction (AITC), on the other hand, has adoptedthe x = y = z = 1/10 exponents for all species ofglulam except Southern Pine. The parameters adoptedby AITC for Southern Pine are x = y = z = 1/20(AITC 1991b).
Next, a regression analysis was conducted to determinea single exponent to use for x, y, and z that best fitall the data. This exponent was 0.071. The resultingequation is plotted with the bending strength datain Figure 6. Thus, for further analysis, an exponentvalue of 0.071 was used to adjust the beam results to astandard volume.
Design Levels
To determine the most appropriate method of account-ing for variation in beam strength resulting from beamsize. a confidence interval on the ratio of the beam sizes
All beam strengths were adjusted to a standard beamsize of 5.125 in. by 12 in. by 21 ft using the best fitvolume effect relationship (exponent of 0.071). Then,results were pooled and analyzed to determine theappropriate design level using the procedures of ASTMD 2915 (ASTM 1991c). A lognormal distribution wasassumed and the 5th percentile (75 percent tolerance
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Figure 7—Distribution of MOR adjusted tostandard beam size and compared to lognormaldistribution.
limit) was adjusted by dividing by 2.1 to obtain thedesign level. The 2.1 factor includes adjustments forsafety and load duration effects. Figure 7 shows thatthe data closely fit the assumed lognormal distribution.Results shown in Table 13 indicate that the calculatedadjusted 5th percentile (75 percent tolerance limit)significantly exceeded the target level of 2,400 lb/in2.
The average MOE of the three groups of beams wasessentially the same, averaging 1.78 × 106 lb/in2,which rounds off to the target average value of 1.8 ×106 lb/in2. As would be expected with E-rated lumber,the variability of the MOE values was quite low.
Comparison with Predicted Values
StrengthThe same procedure used to design the combinationswas used to reanalyze them with the actual MOE andknot data (Table 5). Because the actual knot sizes weresignificantly smaller than that assumed (Table 2), thecalculated design stress level exceeded the 2,400 lb/in2
value originally predicted.
A comparison of the actual results with those fromthe reanalysis indicated that the actual results stillexceeded the predicted values. The next step in thereanalysis was to permit the bending stress index valueto be increased from the 3,250 lb/in2 value assumedin Table 2. An analysis of the bending stress indexvalues is presented in Figure 8; it shows that a value ofat least 3,500 lb/in2 is justified for the 2.0E1/6 gradelumber used for the outer tension lamination.
Figure B—Analysis of bending stress indexvalues for 2.0E grade red maple lumber basedon results of 42 glulam beam tests.
StiffnessBeam stiffness can be predicted by using the actualstiffness data for the lumber (Table 5) and theprocedures of ASTM D 3737 (ASTM 1991a). Resultsare compared in Table 14 and show that the beamMOE values were within 2 percent of the valuespredicted for the three sizes.
Comparison of Beam and End-JointBending Strength
According to ANSI A190.1, the required end-jointstrength is 1.67 times the nominal design strength inbending. By pooling all of the joint-associated tensilestrength data (lumber size exerted little apparenteffect; Table 10), a 5th percentile (75 percent tolerancelimit using the lognormal distribution) of 5,590 lb/in2
was calculated. This value greatly exceeds the value of4,000 lb/in2 commonly targeted for 24F (2,400 lb/in2)beams. The ratio of the 5th percentile (75 percenttolerance limit) of the combined end-joint data to theadjusted 5th percentile (75 percent tolerance limit) ofthe combined beam data in Table 13 is 1.78, which isslightly higher than the ANSI A190.1 requirements.
Conclusions1. Structural glued-laminated (glulam) timber beams
manufactured with E-rated red maple lumber inthe outer zones and No. 2 lumber in the core metor exceeded the target bending design stress of2,400 lb/in2 and modulus of elasticity (MOE) of1.8 × 106 lb/in2.
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2. A red maple combination of glulam timber withdesign properties of at least 2,400 lb/in2 in bendingand MOE of 1.8 × 106 lb/in2 is technically feasible.Both the lumber grades and the finger joints usedwould provide adequate strength and stiffness forthis combination.
3. The ASTM D 3737 procedures developed forsoftwood species accurately predict beam stiffnessand provide conservative strength estimates forbeams made with E-rated red maple lumber.
References
AITC. 1979. Determination of design values forstructural glued laminated timber. AITC 117-79. Vancouver, WA: American Institute of TimberConstruction.
AITC. 1985. Standard specifications for hardwoodglued laminated timber. AITC 119-85. Vancouver,WA: American Institute of Timber Construction.
AITC. 1988. Standard specifications for structuralglued-laminated timber of softwood species. AITC117-88—Manufacturing, Vancouver, WA: AmericanInstitute of Timber Construction.
AITC. 1991a. Inspection manual. AITC 200-91. Van-couver, WA: American Institute of Timber Construc-tion.
AITC. 1991b. Use of a volume effect factor in the de-sign of glued laminated timber beams. Tech. Note 21,October. Vancouver, WA: American Institute of Tim-ber Construction.
ANSI. 1983. Structural glued laminated timber. ANSIA190.1. Englewood, CO: American National StandardsInstitute.
ASTM. 1991a. Standard test method for establishingstresses for structural glued-laminated timber (glulam).ASTM D 3737-91. Philadelphia, PA: American Societyfor Testing and Materials.
ASTM. 1991b. Standard methods of static tests of tim-bers in structural sizes. ASTM D198-84. Philadelphia,PA: American Society for Testing and Materials.
ASTM. 1991c. Standard practice for evaluatingallowable properties for grades of structural lumber.
ASTM D2915-90. Philadelphia, PA: American Societyfor Testing and Materials.
Forest Products Laboratory. 1987. Wood handhook–Wood as an engineering material. Agric. Handb.72 (Rev.). Washington, DC: U.S. Department ofAgriculture. 466 p.
Freas, A.D.; Selbo, M.L. 1954. Fabrication anddesign of glued laminated wood structural members.Tech. Bull. 1069. Madison, WI: U.S. Departmentof Agriculture, Forest Service, Forest ProductsLaboratory.
Hernander, R.; Bender, D.A.; Richburg, B.A.; Kline,K.S. 1992. Probabilistic modeling of glued-laminatedtimber beams. Wood and Fiber Science. 24(3):294-306.
Janowiak, J.J.; Manbeck, H.B.; Wolcott, M.P.;Dawlos, J.F. 1992. Final project report on specialproject SS-047-Preliminary refinement of hardwooddesign values. Harrisburg, PA: Pennsylvania Dept. ofTransportation.
Moody, R.C.; Dedolph, C. Jr.; Plantinga, P.L. 1988.Analysis of size effect for glulam beams. Vol. 1.In: Proceedings of the international conference ontimber engineering; 1988 September; Seattle, WA.Madison, WI: Forest Products Research Society:892-898.
Moody, R.C.; Falk, R.; Williamson, T. 1990. Strengthof glulam beams-volume effects. Vol. 1. In: Proceed-ings of the international timber engineering conference;1990 October 23-25; Tokyo. Tokyo: Steering Commit-tee of the International Timber Engineering Confer-ence: 176-182.
NELMA. 1986. Grading rules for northeastern lumber.Cumberland Center, ME: Northeastern LumberManufacturers Association.
NFPA. 1991. National design specification for struc-tural wood. Washington, DC: National Forest ProductsAssociation.
Wolfe, R.W.; Moody; R.C. 1978. Bending strengthof water-soaked glued-laminated beams. Res. Pap.FPL-RP-307. Madison, WI: U.S. Departmentof Agriculture, Forest Service, Forest ProductsLaboratory.
9
-
Table 1—SI conversion factors
ConversionEnglish unit factor SI unit
board foot (fbm) 0.0024 cubic meter (m3)foot (ft) 0.3048 meter (m)inch (in.) 25.4 millimeter (mm)Fahrenheit (°F) (°F - 32)/1.8 centigrade (°C)pound (lb) 0.4535 kilogram (kg)pound per square
inch (lb/in2) 6.894 Pascal (Pa)
Table 2—Assumed properties of red maplelumber grades for ASTM D 3737 procedures
BendingLamin- MOE stressation (× 106 +ha indexgrade lb/in2) (%) (%) (lb/in
2)b
2.0-1/6 2.0 0.27 12.9 3,2502.0-1/3 2.0 2.63 31.8 3,2501.8-1/3 1.8 2.63 31.8 2,800No. 2 1.5 2.63 31.8 2,500
= average of sum of all knot sizes withineach 1-ft length, taken at 2-in. intervals.
+ h = 99.5 percentile knot size (ASTM 1991a).bClear wood design bending stress.
10
Table 3—Maximum allowable tensionlamination criteriaa
Beam type andlamination criterion
Maximumallowablecharac-teristic
8-Lam
Edge knot + grain deviationCenter knot + grain deviationSlope of grain
12-Lam
40 percent45 percent
1:14
Edge knot + grain deviationCenter knot + grain deviationSlope of grain
16-Lam
30 percent33 percent
1:16
Edge knot + grain deviation 30 percentCenter knot + grain deviation 33 percentSlope of grain 1:16
aASTM 1991a. Knots plus grain deviationsare given in percentage of cross section.
-
Table 4—Target MOE values and sorting scheme Table 6—Knot properties of laminating lumber
Laminationgrade Sorting and grading criteria
2.0-1/6 Average MOE of 2.0 to 2.1 × 106 lb/in2
No MOE value < 1.60 × 106 lb/in2
5th percentile at 1.67 × 106 lb/in2
No MOE value > 2.4 × 106 lb/in2
Edge knot limitation of 1/6
(%)
2.0-1/3
1.8-1/3
MOE restrictions same as for 2.0-1/6 gradeEdge knot limitation of 1/3
Average MOE of 1.8 to 1.9 × 106 lb/in2
No MOE value < 1.40 × 106 lb/in2
5th percentile at 1.45 × 106 lb/in2
No MOE value > 2.2 × 106 lb/in2
Edge knot limitation of 1/3
Table 5—MOE properties of laminating lumber
Lumber typeand grade
Samplesize
AverageMOE(× 106
lb/in2)COVa
(%)
2 by 4 Lumber
2.0-1/62.0-1/31.8-1/3No. 2
2 by 6 Lumber
2.0-1/62.0-1/31.8-1/3No. 2
2 by 8 Lumber
2.0-1/62.0-1/31.8-1/3No. 2
39 1.96 5.940 1.96 5.880 1.72 8.250 1.80 16.2
52 1.93 7.748 1.92 8.9
215 1.74 10.650 1.73 14.3
141 1.93 9.8144 1.90 8.5193 1.74 10.350 1.69 14.9
Lumber typeand grade
Linealfootage
(ft)+h a
(%)
2 by 4 Lumber
2.0-1/6 386 0.2 14.82.0-1/3 420 0.3 16.81.8-1/3 524 0.6 25.5No. 2 442 0.9 29.2
2 by 6 Lumber
2&1/6 572 0.1 13.62.0-1/3 488 0.4 18.51.8-1/3 376 0.1 7.1No. 2 362 2.0 35.3
2 by 8 Lumber
2.0-1/6 304 0.5 11.22.0-1/3 334 0.7 16.61.8-1/3 436 0.1 7.0No. 2 666 1.7 33.6
= average of sum of all knot sizes withineach 1-ft length, taken at 2-in. intervals.
+ h = 99.5 percentile knot size.
aCOV is coefficient of variation
11
-
Table 7—Relative rating system for tension lamination quality
Beam type andlamination criterion
D 3737allowable
value
Lamination quality
Lowa Medium High
8-Lam
Edge knot + grain deviationCenter knot + grain deviationSlope of grainMOE (× 106 lb/in2)
40% >30%45% >30%1:14 >1:16
2.0E (avg.) 20% 10%-20%Slope of grain 1:16 >1:18 1:18-1:20MOE (× 106 lb/in2) 2.0E (avg.) 1:20
2.0E (avg.)
-
Table 9—Results of bending tests on red maple glulam beams
Property 7-Lam 12-Lam 16-Lama 16-Lam
Sample sizeMoisture content (%)
15 1512 12
Normal distribution
Average MOR (lb/in2) 9,070 7,970COV of MOR (%) 13.8 12.4M0R0.05 at 75% tolerance 6,580 6,000Average MOE (× 106 lb/in2) 1.78 1.77COV of MOE (%) 4.3 3.0
Lognormal distribution
Average MOR (lb/in2) 9,080 7,980COV of MOR (%) 14.4 12.1MOR0.05 at 75% tolerance 6,760 6,230
1512
7,890 7,84013.9 14.3
5,720 5,5401.78 1.78
2.5 2.7
7910 7,86015.1 15.8
5,800 5,630
1212
aData in column four exclude the 16-Lam beams thateither did not meet tension lamination requirements(RM8-10) or end-joint spacing requirements (RM8-5, RM8-9).
Table 10—Estimated initial cause ofglulam beam failures
Number of beams
Failure type 8-Lam 12-Lam 16-Lam
Compression followed 4 1 3by tension
Tension in strength- 2 1 3reducing characteristic
Tension in lumber 2 2 2Tension in end joint 7 11 4
13
-
Table 11—Results of tension tests on end-jointedred maple tension lamination material usinglognormal distributiona
PropertyAll sizes
2 by 4 2 by 6 2 by 8 combined
All specimens
Sample size 20 27 19 66Average TS (lb/in2) 8,310 8,690 8,120 8,410COV TS (%) 28.4 20.7 16.8 22.2
Specimens with failure involving end joint
Sample Size 19 26 18 63Average SGb 0.57 0.57 0.56 0.57Average MC (%) 8.6 8.6 7.8 8.3Average TS (lb/in2) 8,470 8,720 8,010 8,430COV TS (%) 27.6 21.1 16.2 21.9
aTS is tensile strength; SG, specific gravity; and MC,moisture content.
bBased on volume at time of test and ovendry weight.
Table 12—Comparison of beam strength using differentvolume effect exponents
Ratio of predictedmean MOR
Ratio of actualx = y = x = y = mean MOR
Beam comparison z = 0.1 z = 0.05 (average (lower, upper))a
12-Lam and 8-Lam 0.876 0.936 0.879 (0.810, 0.948)16-Lam and 8-Lam 0.803 0.896 0.864 (0.785, 0.943)16-Lam and 12-Lam 0.910 0.954 0.983 (0.909, 1.057)
a90 percent confidence interval
Table 13—Adjusted glulam beambending strength resultsa
Property Result
Sample size 42Average MOR (lb/in2) 8,590COV (%) 13.85th percentile (75% tolerance limit) 6,620Adjusted 5% tolerance limit 3,150
aData adjusted to standard dimensions of5.125 in. width by 12 in. depth by 21 ft length.
Table 14—Comparison of actual and predictedMOE values based on actual lumber properties
Beamtype
Actual Predicted RatioMOE (A) MOE (P) of A/P
8-Lam 1.78 1.78 1.0012-Lam 1.77 1.73 1.0216-Lam 1.78 1.74 1.02
14
-
Appendix A
Properties of Red Maple Lumber Used forMidlength Region of Outer Tension Lamination
Table Al-Properties of 2 by 4 lumberused in tension lamination
Relativequality of
Tables A1 through A3 list the lumber properties usedfor the tension lamination of 8-Lam, 12-Lam, and 16-Lam beams, respectively. All lumber ranged from 13 to
Beam midlengthno. MOE Characteristica regionb
RM4-1 1.89 Clear16 percent moisture content.
RM4-2
RM4-3c
RM4-4
RM4-5
RM4-6
RM4-7
RM4-8
RM4-9
RM4-10
RM4-11
RM4-12
RM4-13
RM4-14
RM4-15
1.93
2.022.03
1.892.08
1.901.84
1.951.87
2.032.18
1.922.19
1.92
2.021.97
1.99
2.072.20
1.821.93
2.111.89
1.99
1.862.12
1:16 GS
Clear5% GD
1:10 GSClear
40% CK + GDClear
ClearClear
ClearClear
ClearClear
30% EK + GDand 1:16 GS
33% EK + GDClear
Clear
ClearClear
25% EK + GDClear
ClearClear
Blue stain
1:14 GSClear
M
H
L
L
H
H
H
M
L
H
H
M
H
H
M
aCK is center knot, GD grain deviation,and GS slope of grain.
bM is medium, H high, and L low.cTested upside down because ofbelow-grade tension lamination.
15
-
Table A2—Properties of 2 by 6 lumberused in tension lamination
Relativequality of
Beam midlengthno. MOE Characteristic region
RM6-1 1.97 Clear2.19
RM6-2 1.841.71
RM6-3 1.951.70
RM6-4 1.931.84
RM6-5a 2.041.80
RM6-6 2.011.84
RM6-7 1.642.00
RM6-8 2.111.81
RM6-9 2.031.91
RM6-10 1.982.25
RM6-11 2.022.04
RM6-12 1.881.85
RM6-13 1.65
RM6-14 1.981.97
RM6-15 1.831.90
20% GD
ClearClear
ClearLow MOE
30% EK + GD1:8-1:10 GS
Clear1:16 GS
1:6-1:8 Edge GSClear
Low MOEClear
Clear33% EK + GD
1:12 GS1:16 GS
ClearClear
1:12 GSClear
ClearClear
Worm holesLow MOE
1:18 GSClear
ClearClear
M
H
M
L
M
L
M
L
L
H
L
H
M
M
H
aTested upside down because ofbelow-grade tension lamination.
Table A3—Properties of 2 by 8 lumberused in tension lamination
Beamno. MOE Characteristic
Relativequality ofmidlength
region
RM8-1
RM8-2
RM8-3
RM8-4
RM8-5a
RM8-6
RM8-7
RM8-8
RM8-9a
RM8-10a
RM8-11
RM8-12
RM8-13
RM8-14
RM8-15
2.222.122.14
2.212.13
2.192.21
2.022.001.96
2.062.011.90
2.031.562.10
1.641.88
1.671.97
1.711.55
1.711.62
2.041.811.90
2.082.54
1.401.841.88
1.791.741.98
1.751.96
ClearClearClear
Clear40% GD
35% CK + GDClear
Clear1:6 GS1:8 GS
Clear50% EK + GD
Clear
Clear50% GD + Low MOE
30% EK + GD
Clear + Low MOE1:12 Edge GS
Clear1:8 Edge GS
1:12 GS1:12 GS + Low MOE
ClearClear + Low MOE
Clear1:16 GS + 20% GD
Clear
Clear1:10 GS + 10% CK
+GD
40% CK + GD15% CK + GD30% CK + GD
1:8-1:11 GS1:13 GS10% GD
ClearClear
H
L
L
L
L
L
L
L
L
M
L
M
L
L
H
aBelow-grade tension lamination. Beams weretested in their original orientation as a resultof unbalanced layup.
16
-
Appendix B
Glulam Beam Results and Failure Descriptions
Tables B1 through B3 list the results of bending testson 8-Lam, 12-Lam, and 16-Lam beams, respectively.
17
-
Tab
le B
1—R
esu
lts
of b
end
ing
test
s on
8-L
am r
ed m
aple
bea
ms
Bea
mno
.
Dim
ensi
onB
eam
Beam
Tim
e to
Loa
d at
MO
Rb
MO
EFa
ilure
Wid
th
Dep
th
MC
a fa
ilu
refa
ilure
(× 1
03 (
× 1
03ty
pec
(in
.) (
in.)
(%
) (m
in:s
) (×
10
3 l
b)
lb/i
n2)
lb/i
n2)
(EJ
/La
m)
Com
men
td
RM
4-1
3.00
12.0
3 12
2.91
12.0
3 12
2.98
12.0
0 10
3.00
12.0
3 13
2.99
12.5
0 12
3.00
12.0
3 12
3.00
12.0
3 12
2.98
12.0
7 12
2.98
12.0
7 13
5:40
14.6
8
RM
4-2
10:3
017
.72
RM
4-3
6:39
12.0
87.
645
1.73
RM
4-4
9:16
14.5
29.
060
1.62
RM
4-5
10:0
216
.24
RM
4-6
8:36
13.6
2
RM
4-7
12:3
815
.46
RM
4-8
8:03
14.7
2
RM
4-9
6:32
12.1
6
RM
4-10
3.01
12.0
3 14
•
14
:02
17.0
4
9.17
3
11.1
62
10.1
31
8.50
1
9.64
5
9.18
5
7.58
0
10.5
92
1.77
1.87
1.81
1.75 1.75
1.77
1.70
1.86
Lam
Mos
tly
TL fa
ilure
; 5%
EJ
failu
re a
t 10
.5 ft
, pro
paga
ted
thro
ugh
2d L
am;
obse
rved
GLF
from
6.5
to
11 ft
bet
wee
n 2d
and
3d
Lam
s.
Lam
Noi
se a
t 17
× 1
03 lb
; mos
tly
TL f
ailu
re f
rom
11
to 1
2 ft
; 30%
EJ
failu
rein
TL
at 1
2.8
ft, p
ropa
gate
d th
roug
h E
J in
2nd
Lam
at
10.5
ft
(95%
).
Lam
Bea
m t
este
d up
side
-dow
n du
e to
bel
ow-g
rade
TL;
TL
failu
re (
GS)
fro
m6
to 7
ft,
prop
agat
ed t
o G
LF b
etw
een
2d a
nd 3
d La
ms
from
0 t
o 7
ft.
Lam
Noi
se a
t 11
.5 ×
103
lb, m
ostl
y TL
fai
lure
at
9.8
ft; 2
5% E
J fa
ilure
in T
Lat
7.8
ft.
Lam
Noi
se a
t 14
× 1
03 lb
; bri
ttle
TL
failu
re a
t 11
.9 f
t; m
ore
TL f
ailu
re f
rom
5 to
7 f
t, pr
opag
ated
to
EJ
(100
%)
in 2
d La
m a
t 12
.5 f
t.
EJ/
Lam
Noi
se a
t 12
.24
× 10
3 lb
; fai
lure
in T
L fr
om 8
to
13 f
t; al
so 1
0% E
Jfa
ilure
in T
L at
10.
5 ft
; GLF
bet
wee
n 1s
t an
d 2d
Lam
s fr
om 1
3 to
15
ft.
Lam
Noi
se a
t 12
.5 ×
103
lb; c
ompr
essi
on w
rink
ling
in 8
to
12 ft
reg
ion,
init
iate
d at
13.
5 ×
103
lb t
hrou
gh f
ailu
re; a
ll TL
fai
lure
at
7 to
8 f
t
Lam
Noi
se a
t 14
.2 ×
103
lb; T
L fa
ilure
(G
S) f
rom
9 t
o 12
ft;
seve
ral G
LFs
ingl
uelin
es b
etw
een
4th
and
5th
Lam
s.
Lam
Noi
se a
t 10
.2 ×
103
lb; 1
0% E
J fa
ilure
in T
L at
10.
6 ft
, pro
paga
ted
thro
ugh
EJ
in 3
d La
m a
t 11
.8 ft
.
Lam
TL f
ailu
re f
rom
12.
5 to
13.
8 ft
, pro
paga
ted
to E
J (5
%)
in 2
d La
m a
t9.
6 ft
; com
pres
sion
wri
nklin
g in
8 t
o 12
ft r
egio
n, in
itia
ted
at 1
5,20
0 ×
103
lb.
(Pag
e 1
of 2
)
-
Ta
ble
B1—
Res
ult
s o
f b
end
ing
tes
ts o
n 8
-La
m r
ed m
ap
le b
eam
s-co
n.
Bea
mno
.
Dim
ensi
onB
eam
Bea
mTi
me
toLo
ad a
tM
OR
bM
OE
Failu
reW
idth
Dep
th M
Ca
failu
refa
ilu
re
(×
103
(×
103
type
c
(in
.)
(in
.)
(%)
(min
:s)
(×
103
lb)
lb/in
2 )
lb/in
2 )
(EJ/
Lam
)C
omm
entd
RM4-
113.
0012
.07
128:
2315
.18
9.41
01.
88EJ
No
nois
eun
til f
ailu
re; 1
00%
EJ
failu
re in
TL
at 1
2.5
ft; G
LF b
etw
een
4th
and
5th
Lam
s.RM
4-12
2.95
12.0
512
11:0
416
.12
10.1
921.
75EJ
No
nois
eun
til f
ailu
re;
100%
EJ
failu
re i
n TL
at
10.3
ft;
britt
le f
ailu
reth
roug
h 2d
and
3d
Lam
s; G
LF b
etw
een
5th
& 6
th a
nd 6
th &
7th
Lam
s.RM
4-13
2.97
12.0
513
5:15
10.6
86.
717
1.77
Lam
No
nois
eun
til f
ailu
re; b
ritt
le T
L fa
ilure
at
11.3
ft; G
LF b
etw
een
2d &
3d a
nd 5
th &
6th
Lam
s.
RM4-
142.
9712
.03
128:
1314
.98
9.44
11.
92La
mN
oise
at
10.7
× 1
03 lb
; com
pres
sion
wri
nklin
g, in
itia
ted
at 1
3.6
× 10
3 lb
at 1
2 ft
; bri
ttle
TL
failu
re a
t 10
.5 ft
; GLF
bet
wee
n 2d
and
3d
Lam
s fr
om13
to
17ft.
RM4-
153.
0012
.05
136:
4512
.23
7.61
11.
81La
mN
oise
at
6.5
× 10
3 lb
; TL
failu
re a
t 7
to 1
0 ft
to
EJ
(25%
) in
2d
Lam
at
11.3
ft;
slig
ht c
ompr
essi
on w
rink
ling
at f
ailu
re a
t 12
.5 f
t.
a MC
is
moi
stur
e co
nten
t.b M
OR
cal
cula
tions
inc
lude
d de
ad l
oad
stre
ss.
c EJ
is e
nd jo
int,
GLF
glu
elin
e fa
ilure
, GS
slop
e of
gra
in, a
nd T
L te
nsio
n la
min
atio
n.
(Pag
e 2
of 2
)
-
Tab
le B
2—R
esu
lts
of b
end
ing
test
s on
12-
Lam
red
map
le b
eam
s
Bea
mno
.
Dim
ensi
onB
eam
Beam
Tim
e to
Load
at
MO
Ra
MO
EFa
ilure
Wid
th
Dep
th
MC
fa
ilu
refa
ilure
(× 1
03 (
× 1
03ty
pe(i
n.)
(i
n.)
(%
) (m
in:s
) (×
1
03
lb)
lb/i
n2)
lb/i
n2)
(EJ
/La
m)
Com
men
tb
RM
6-1
5:40
28.3
67.
161.
85La
m
RM
6-2
7:23
33.7
58.
503
1.78
EJ
RM
6-3
9:38
40.9
910
.240
1.73
EJ
RM
6-4
5:31
27.8
96.
982
1.76
EJ/
Lam
RM
6-5
5.00
18.0
9 12
5.00
18.0
6 12
5.00
18.0
9 11
5.00
18.1
0 11
5.00
18.1
0 12
6:23
31.2
07.
808
1.73
EJ/
Lam
RM
6-6
5.00
18.0
5 12
8:15
35.6
08.
945
1.78
EJ/
Lam
RM
6-7
5.00
18.0
5 13
5.00
18.0
5 13
5.00
18.0
6 12
4.95
18.0
6 11
8:24
36.5
19.
172
1.78
Lam
RM
6-8
7:08
32.0
08.
050
1.78
Lam
RM
6-9
5:20
27.6
56.
961
1.83
EJ/
Lam
RM
6-10
5:47
28.5
97.
267
1.78
EJ/
Lam
Noi
se a
t 15
× 1
03 lb
; TL
failu
re a
t 12
to
17 f
t; 5%
EJ
failu
re in
TL
at11
.6 ft
.
Noi
se a
t 15
× 1
03 lb
; 60%
EJ
failu
re in
TL
at 1
2.5
ft; G
LF b
etw
een
7th
and
8th
Lam
s fr
om 6
to
8 ft
.
Noi
se a
t 23
× 1
03 lb
; 100
% E
J fa
ilure
in T
L at
15
ft; c
ompr
essi
onw
rink
ling
at f
ailu
re a
t 15
.3 a
nd 1
7.2
ft.
Noi
se S
t 13
× 1
03 lb
; 50%
EJ
failu
re in
TL
at 1
6.3
ft, p
ropa
gate
d to
100%
EJ
failu
re in
3d
Lam
at
17.3
ft.
Bea
m t
este
d up
side
-dow
n du
e to
bel
ow-g
rade
TL;
noi
se a
t 25
.5 ×
103
lb; 4
0% E
J fa
ilure
in T
L at
17.
5 ft
; sev
eral
GLF
s be
twee
n 6t
h an
d 7t
hLa
ms.
Noi
se a
t 14
.2 ×
103
lb; 7
0% E
J fa
ilure
in T
L at
20.
6 ft
, als
o TL
fai
lure
at 1
7.5
ft; G
LF b
etw
een
5th
and
6th
Lam
s; s
econ
dary
EJ
failu
re (7
5%)
in 2
nd L
am a
t 16
.6 ft
.
Noi
se a
t 26
× 1
03 lb
; all
TL f
ailu
re f
rom
13
to 1
4 ft
; GLF
bet
wee
n 4t
han
d 5t
h La
ms
from
0 t
o 9
ft.
Noi
se a
t 18
.5 ×
103
lb;
TL
failu
re (
GD
) fr
om 1
4 to
16
ft; G
LF b
etw
een
6th
and
7th
Lam
s fr
om 2
2 to
25
ft.
Noi
se a
t 21
.5 ×
103
lb; 3
0% E
J fa
ilure
in T
L at
14.
5 ft
, pro
paga
ted
thro
ugh
EJ
(50%
) in
2d
Lam
at
16 f
t.
Noi
se a
t 21
× 1
03 lb
; 40%
EJ
failu
re in
TL
at 1
1.8
ft, a
lso
TL f
ailu
refr
om 1
1.8
to 1
4.5
ft, t
hen
to E
J (5
0%)
in 2
d La
m a
t 14
.3 f
t; G
LFbe
twee
n 4t
h an
d 5t
h La
ms.
(Pag
e 1
of 2
)
-
Ta
ble
B2—
Res
ult
s o
f b
end
ing
tes
ts o
n 1
2-L
am
red
ma
ple
bea
ms-
con
.
Dim
ensi
onB
eam
Bea
mTi
me
toLo
ad a
tM
OR
aM
OE
Failu
reBe
amW
idth
Dep
th M
Cfa
ilure
fail
ure
(×
10
3 (×
10
3ty
peno
.(i
n.)
(i
n.)
(%
) (m
in:s
) (×
1
03
lb)
lb/i
n2)
lb/i
n2)
(EJ
/La
m)
Com
men
tb
RM6-
115.
0018
.10
105:
0726
.64
6.68
11.
82La
mN
oise
at
25 ×
103
lb; m
ostl
y TL
fai
lure
at
16.5
ft;
5% E
J fa
ilure
at
17 f
t;G
LF b
etw
een
1st
and
2d L
ams
from
11
to 1
6 ft
.
RM6-
125.
0018
.10
118:
3834
.90
8.72
31.
67E
J/La
mN
oise
at
16.5
× 1
03 lb
; 25%
EJ
failu
re a
t 17
.6 f
t, to
100
% E
J fa
ilure
in2d
Lam
at
18.3
ft; G
LF b
etw
een
4th
and
5th
Lam
s fr
om 2
1 to
24
ft.
RM6-
134.
9518
.05
126:
2230
.90
7.85
51.
79La
mN
oise
at
23.5
× 1
03 lb
; all
TL f
ailu
re a
t 14
.3 f
t, to
100
% E
J fa
ilure
in 2
dLa
m a
t 14
.5 ft
; GLF
bet
wee
n 2d
and
3d
Lam
s fr
om 1
2 to
14
ft.
RM
6-14
5.00
18.0
5 13
5:47
29.0
07.
304
1.76
EJN
oise
at
17 ×
103
lb; 7
5% E
J fa
ilure
in T
L at
11.
3 ft
, pro
paga
ted
to30
% E
J fa
ilure
in 4
th L
am a
t 17
.7 ft
.
RM6-
155.
0018
.08
127:
1531
.71
7.95
21.
67E
J/La
mN
oise
at
9.5
× 10
3 lb
; 100
% E
J fa
ilure
in T
L at
11.
7 ft
; TL
failu
re f
rom
9 to
11.
7 ft
; GLF
bet
wee
n 1s
t an
d 2d
Lam
s.
a MO
R c
alcu
latio
ns i
nclu
ded
dead
loa
d st
ress
.b E
J is
end
join
t, G
D g
rain
dir
ecti
on, G
LF g
luel
ine
failu
re, G
S sl
ope
of g
rain
, and
TL
tens
ion
lam
inat
ion.
(Pag
e 2
of 2
)
-
Tab
le B
3—R
esu
lts
of b
end
ing
test
s on
16-
Lam
red
map
le b
eam
s
Bea
mno
.
Dim
ensi
onB
eam
Bea
mTi
me
toLo
ad a
tM
OR
aM
OE
Failu
reW
idth
Dep
th M
Cfa
ilure
failu
re(×
103
(×
103
type
(in
.)
(in
.)
(%)
(min
:s)
(×
10
3
lb)
lb/i
n2)
lb/i
n2)
(EJ
/La
m)
Com
men
tb
RM
8-1
RM
8-2
8:52
69.6
09.
690
1.82
Lam
6:25
57.0
07.
980
1.82
Lam
RM
8-3
6:52
60.0
08.
399
1.79
EJ
RM
8-4
RM
8-5
5:15
47.5
06.
697
1.77
EJ/
Lam
8:36
48.5
06.
907
1.75
Lam
RM
8-6
12:3
854
.30
7.68
11.
77La
m
RM
8-7
6.75
24.1
2 14
6.75
24.0
9 11
6.74
24.0
9 11
6.70
24.1
3 11
6.70
24.0
0 12
6.75
23.9
7 12
6.75
24.0
0 13
6.75
23.9
4 13
6.75
23.9
4 12
8:03
59.2
08.
342
1.78
EJ/
Lam
RM
8-8
6:32
50.6
07.
184
1.81
RMB-
914
:02
58.0
08.
217
RM
8-10
6.75
24.2
0 11
8:07
66.5
09.
202
1.77
1.79
Lam
Lam
Noi
se a
t 43
× 1
03 lb
; TL
failu
re f
rom
16
to 2
0 ft
.
Noi
se a
t 41
× 1
03 lb
; TL
failu
re (
GD
) at
24.
5 ft
, pro
paga
ted
to 5
0% E
Jfa
ilure
in
2d L
am a
t 24
ft.
Noi
se a
t 43
× 1
03 lb
; 100
% E
J fa
ilure
in T
L at
18.
3 ft
; com
pres
sion
wri
nklin
g at
fai
lure
at
22 f
t.
Noi
se a
t 13
× 1
03 lb
; 50%
EJ
failu
re in
TL
at 2
5 ft
.
Noi
se a
t 20
.5 ×
103
lb; s
tack
ed E
J in
Lam
s 2
and
3 (1
8.7
ft a
nd18
.6 f
t)c ;
join
ts n
ot a
ssoc
iate
d in
fai
lure
–all
TL f
ailu
re f
rom
24
to 2
5 ft
.
Noi
se a
t 18
× 1
03 l
b; T
L fa
ilure
(G
D)
at 1
6.5
ft, p
ropa
gate
d to
50%
EJ
failu
re in
2d
Lam
at
17 ft
.
Noi
se a
t 20
× 1
03 lb
; 75%
EJ
failu
re in
TL
at 1
8 ft
; 1:1
2 ed
ge G
S in
TL
at 1
7.5
ft le
adin
g in
to 7
5% E
J fa
ilure
in 2
d La
m a
t 17
ft.
Noi
se a
t 38
× 1
03 l
b; T
L fa
ilure
(G
S) f
rom
20
to 2
1 ft
, pro
paga
ted
to80
% E
J fa
ilure
in 2
nd L
am a
t 20
.5 ft
.
Noi
se a
t 33
× 1
03 lb
; 10%
EJ
failu
re in
TL
at 2
0 ft
, pro
paga
ted
thro
ugh
EJ
(100
%) i
n 2d
Lam
at
22.5
ft; c
ompr
essi
on w
rink
ling
at fa
ilure
in t
opLa
m a
t 19
ft;
EJ
stac
ked
in 1
st a
nd 2
nd L
ams
at 1
2 ft
–not
invo
lved
infa
ilure
.c
Noi
se a
t 34
× 1
03 lb
; all
TL f
ailu
re a
t 15
ft,
prop
agat
ed t
o 15
% E
Jfa
ilure
in 2
d La
m a
t 14
ft; G
LF b
etw
een
4th
and
5th
Lam
s; T
L di
d no
tm
eet
crite
ria.
(Pag
e 1
of 2
)
-
Tab
le B
3—R
esu
lts
of b
end
ing
test
s on
16-
Lam
red
map
le b
eam
s—co
n.
Dim
ensi
onB
eam
Bea
mTi
me
toLo
ad a
tM
OR
a M
OE
Failu
reB
eam
Wid
th D
epth
MC
failu
refa
ilu
re
(×
103
(×
103
type
no.
(in
.)
(in
,)
(%)
(min
:s)
(×
10
3
lb)
lb/i
n2)
lb/i
n2)
(EJ
/La
m)
Com
men
tb
RM8-
116.
7524
.03
106:
2854
.10
7.61
51.
87E
J/La
mN
oise
at
22 ×
103
lb; 8
0% E
J fa
ilure
in T
L at
15.
5 ft
, pro
paga
ted
to15
% E
J fa
ilure
in 2
d La
m a
t 19
.5 ft
; GLF
bet
wee
n 3d
and
4th
Lam
sfr
om 1
to
7 ft
.
RM
8-12
6.75
24.0
8 11
5:15
59.5
08.
328
1.75
EJN
oise
at
38 ×
103
lb; 1
00%
EJ
failu
re in
TL
at 2
2.5
ft; c
ompr
essi
onw
rink
ling
first
det
ecte
d in
top
Lam
at
53 ×
103
lb.
RM
8-13
6.75
24.0
0 12
8:13
36.6
05.
203
1.68
EJ/
Lam
Noi
se a
t 28
× 1
03 lb
; 50%
EJ
failu
re in
TL
at 1
4 ft
; GLF
bet
wee
n 7t
han
d 8t
h La
ms
from
24
to 3
0 ft
.
RM8-
14
6
.75
24.0
0 13
7:40
59.0
08.
313
1.75
EJN
oise
at
34.5
× 1
03 lb
; 95%
EJ
failu
re in
TL
at 1
5.5
ft, p
ropa
gate
d to
25%
EJ
failu
re i
n 2d
Lam
at
17 f
t; co
mpr
essi
on w
rink
ling
first
det
ecte
din
top
Lam
at
55 ×
103
lb; G
LF b
etw
een
9th
and
10th
Lam
s fr
om 2
4 to
33 f
t.
RMB-
156.
7524
.00
127:
3361
.50
8.66
21.
76La
mN
oise
at
16 ×
103
lb; a
ll TL
fai
lure
at
18 f
t; G
LF b
etw
een
7th
and
8th
Lam
s at
12
ft.a M
OR
cal
cula
tions
inc
lude
dea
d lo
ad s
tres
s.b E
J is
end
join
t, G
D g
rain
dir
ecti
on, G
LF g
luel
ine
failu
re, G
S sl
ope
of g
rain
, and
TL
tens
ion
lam
inat
ion.
c Did
not
mee
t A
NSI
A19
0.1
requ
irem
ents
.
(Pag
e 2
of 2
)
-
Appendix C
Glulam Beam Failure Maps and Lumber Properties
Location of failures in the tension zone of the beamsis given in the figures. Failure through end joints isreported by an indication of the percentage of thefailure that occurred at the joint itself. Modulus ofelasticity values are given for each piece of lumber inthe outer tension zone; the locations with reference toone end are given at the bottom of each figure.
24
-
Beam No. RM4-1 Beam No. RM4-2
Beam No. RM4-3
Beam No. RM4-5
Beam No. RM4-7 Beam No. RM4-8
Beam No. RM4-9 Beam No. RM4-10
B e a m No. R M 4 - 4
Beam No. RM4-6
25
-
Beam No. RM4-11 Beam No. RM4-12
Beam No. RM4-13 Beam No. RM4-14
Beam No. RM6-1 Beam No. RM6-2
26
-
Beam No. RM6-3 Beam No. RM6-4
Beam No. RM6-5 Beam No. RM6-6
Beam No. RM6-7 Beam No. RM6-8
Beam No. RM6-9 Beam No. RM6-10
Beam No. RM6-11 Beam No. RM6-12
27
-
Beam No. RM6-13 Beam No. RM6-14
Beam No. RM6-15
Beam No. RM8-1 Beam No. RM8-2
Beam No. RM8-3 Beam No. RM8-4
Beam No. RM8-5 Beam No. RM8-6
28
-
Beam No. RM8-7 Beam No. RM8-8
Beam No. RM8-9 Beam No. RM8-10
Beam No. RMB-11 Beam No. RM8-12
Beam No. RM8-13 Beam No. RM8-14
Beam No. RM8-15
29
-
Appendix D
Properties of Red Maple End-Jointed Lumber for
Grades Other Than Tension Lamination Quality
Table D—Results of tension tests on red mapleend-jointed lumber for grades other thantension lamination quality using thelognormal distribution
AllStatistics reported include results for all end-jointspecimens considered and for those specimens withjoint-associated failures.
Lumber size sizescom-
Grade and property’ 2 by 4 2 by 6 2 by 8 bined
2.0-1/6
All specimens
Sample size 10 20 5 35Average TS (lb/in2) 6,950 7,130 6,880 7,020TS COV (%) 26.6 20.7 59.3 28.9
End-joint failures
Sample size 8 16 5 29Average SG 0.57 0.57 0.57 0.57Average MC (%) 8.7 8.9 7.1 8.5Average TS (lb/in2) 7,030 7,160 6,880 7,050TS COV (%) 30.0 21.1 59.3 31.0
1/3 EKc
All specimens
Sample size 14 19 21 54Average TS (lb/in2) 7,060 6,450 6,520 6,630TS COV(%) 23.3 29.3 25.2 26.1
End-joint failures
Sample size 9 12 13 34Average SG 0.54 0.52 0.55 0.54Average MC (%) 8.7 8.5 7.4 8.1Average TS (lb/in2) 7,040 6,580 6,830 6,790TS COV (%) 15.2 31.9 20.1 23.6
No. 2
All specimens
Sample size 4 4 3 11Average TS (lb/in2) 5,720 5,180 4,990 5,270TS COV (%) 35.1 43.7 3.9 30.9
End-joint failures
Sample size 1 3 1 5Average SG. 0.64 0.52 0.59 0.56Average MC (%) 8.7 8.8 8.4 8.7Average TS (lb/in2) 6,230 5,740 5,160 5,670TS COV (%) 50.6 — 35.9
aTS is tensile strength, SG specific gravity, andMC moisture content.
bSpecimens with failures involving an end joint.cBecause of the percentage of small sample sizes, resultsfor 2.0-1/3 and 1.8-1/3 grades were combined.
30
top related