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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
2
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
7
-
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.
8
-
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