United States

Department of

Agriculture Performance of

Forest Service

Forest

Products Red Maple Glulam

Laboratory

Research

Paper

FPL-RP-519

Timber Beams

Harvey B. Manbeck

John J. Janowlak

Paul R. Blankenhorn

Peter Labosky

Russell C. Moody

Roland Hernandez
Abstract

A red maple glued-laminated (glulam) beam combination that would achieve a design bending stress of

2,400 lb/in2 (16.5 MPa) and modulus of elasticity of

1.8 × 106 lb/in2 (12.4 GPa) was developed; 45 beams

were evaluated. The properties of the lumber grades

used in the layup and their placement within the beams

were closely monitored during beam fabrication. Another 166 specimens of end-jointed lumber were gathered during manufacture to relate the individual tensile

strength performance of end joints to their performance

in the beams. The evaluations of the end-jointed specimens and the full-sized beams indicate that a glulam

beam combination with the targeted design stress in

bending 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, Paul

R.; Labosky, Peter; Moody, Russell C.; Hernandez, Roland.

1993. Red maple glulam timber beam performance. Res.

Pap. FPL-RP-519. Madison, WI: U.S. Department of

Agriculture, Forest Service, Forest Products Laboratory.

30 p.

A limited number of free copies of this publication

are available to the public from the Forest Products

Laboratory, One Gifford Pinchot Drive, Madison, WI

53705-2398. Laboratory publications are sent to more than

1,000 libraries in the United States and elsewhere.

The Forest Products Laboratory is maintained in

cooperation with the University of Wisconsin.

Introduction .................

Objective and scope ..............

Design of beam combinations ...........

Procedures for grading lumber

and 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-joint

bending strength .............

Conclusions .................

References ..................

Appendix A .................

Appendix B .................

Appendix C .................

Appendix D .................

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29
Red Maple Glulam Timber

Beam 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 hardwood species in the forests of the Northeastern United

States. Because this species has not been traditionally considered for structural applications, there has

been little interest in developing engineered red maple

products. The emerging prominence of red maple in

the forests makes product development of vital interest

to landowners and to wood processors, fabricators, and

designers.

Red maple has excellent mechanical properties, treats

well, and has good gluing characteristics (FPL 1987).

Thus, it is a good candidate for structural applications

such as glued-laminated (glulam) timber beams. The

American Institute of Timber Construction (AITC)

established specifications for hardwood glulam timber

in AITC 119 (AITC 1985). However, red maple is not

included as a candidate species for lamination stock.

Moreover, this specification provides conservative

design properties of homogeneous combinations of

hardwood and does not provide options for developing

efficient combinations of glulam timber. Consequently,

a cooperative research project was conducted between

the Pennsylvania State University and the USDA

Forest Service, Forest Products Laboratory to develop

efficient combinations of red maple glulam timber. The

target design stresses for these combinations were

2,400 lb/in2 in bending stress and 1.8 × 106 lb/in2

in modulus of elasticity (MOE). (See Table 1 for SI

conversion factors.)

The research reported here was sponsored and funded

by the Pennsylvania Department of Transportation

(Project No. SS-043), the Pennsylvania Agriculture

Experiment Station, and the U.S. Department

of Agriculture, Forest Service, Forest Products

Laboratory.

Objective and Scope

The objectives of the research described in this report

were as follows:

1. to develop a red maple glulam timber beam

combination with a target bending design stress

level of 2,400 lb/in2 and MOE of 1.8 × 106 lb/in2

2. to establish the technical basis for developing

allowable properties for bending strength and MOE

of red maple glulam beams

3. to determine if calculation procedures outlined in

the American Society for Testing and Materials

(ASTM) D 3737 (ASTM 1991a) can be used to

predict bending strength and stiffness of red maple

glulam beams

We expected that successful completion of the

objectives would provide data to support including

red maple in glulam timber design specifications.

In addition, the procedures developed could provide the glulam timber industry with better methods for developing more efficient hardwood glulam

timber beam designs than does the current standard

AITC 119 (AITC 1985).

The scope of the study included (1) design of beam

combinations, (2) sawing, drying, grading, and

characterization of properties of a large sample of red

maple structural lumber, (3) manufacture of 45 glulam

timber beams, and (4) evaluation of beam bending

strength and stiffness.
Results of the laboratory tests of the lumber specimens

will be used to develop input lumber properties

required by advanced probabilistic models (Hernandez

and others 1992). Laboratory test results for endjointed lumber are presented in this report because

they are critical for the development of a glulam

standard. Results of the glulam beam modeling will

be presented in a separate report.

Design of Beam Combinations

2.0-1/3

1.8-1/3

No. 2

1.8-1/3

2.0-1/6

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 basis

of assumed lumber properties of red maple lumber,

current surveys of mechanical properties of existing

red maple lumber, and procedures established in the

ASTM D 3737 Standard (ASTM 1991a). The proposed

beam combinations targeted a design bending stress of

2,400 lb/in2 and MOE of 1.8 × 106 lb/in2.

The lamination material consisted of E-rated grades of

lumber for the outer laminations and visually graded

lumber for the core laminations. The beams contained

2.0E material in the outer zones, 1.8E material in

the next inner zones, and No. 2 material in the core

laminations. Edge knots for the lumber grades used for

the two zones on the compression side of the beams and

for the next inner zone on the tension side were limited

to one-third the area of the cross section (two-thirds

clear lumber). This represents No. 2 or better lumber

and is designated in the text as 2.0-1/3 lumber for the

outer zone and 1.8-1/3 lumber for the next inner zone.

The E-rated lumber in the outer tension zone had an

edge-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 fabricated to represent critical beam sizes with small,

medium, and large dimensions (Fig. 1). The smallest

beam (8-Lam) had eight laminations with finished dimensions of 3 in. wide by 12 in. deep by 20 ft long.

The intermediate beam (12-Lam) had 12 laminations

with dimensions of 5 in. wide by 18 in. deep by 30 ft

long. The largest beam (16-Lam) had 16 laminations

with dimensions of 6.75 in. wide by 24 in. deep by

40 ft long. The beams were manufactured using nominal 2 by 4, 2 by 6, and 2 by 8 lumber, respectively (1.5

by 3.5 in., 1.5 by 5.5 in., and 1.5 by 7.25 in., respectively).

The target beam MOE of 1.8 × 106 lb/in2 required

certain MOE levels of laminating lumber. To determine

if the current resource of red maple structural lumber

would provide adequate yields of the desired E-rated

grades, preliminary results of ongoing research studies

at both Pennsylvania State University (Janowiak and

others 1992) and the Forest Products Laboratory

2

8-Lam

3-in. width

12-in. depth

20-ft length

12-Lam

5-in. width

18-in. depth

30-ft length

16-Lam

6.75-in. width

24-in. depth

40-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 combinations. Location of various lumber grades for 8-,

12-, and 16-lamination beams.

(FPL) were reviewed. The MOE data indicated

that the proposed E-rated grades of 2.0-1/6, 2.0-1/3,

and 1.8-1/3 could be readily derived from available

red maple lumber populations. Also, results of the

knot analysis from the independent sample of red

maple lumber indicated that the lumber quality was

adequate to achieve the targeted 2,400-lb/in2 design

bending stress (Green and McDonald, in preparation).

Therefore, assumed properties were used to develop the

glulam beam combinations (Table 2).

To develop glulam beam combinations that would

achieve the target bending stress of 2,400 lb/in2

,

several assumptions were necessary to estimate the

minimum strength ratio, the bending stress indices

(clear wood stress), and the knot properties required by

the ASTM D 3737 Standard (ASTM 1991a). Values for

the minimum strength ratios of the candidate grades of

red maple were estimated from values established for

E-rated lumber across all species in AITC 117 (AITC

1979). Bending stress indices for the proposed E-rated

grades were those recommended by ASTM D 3737.

Finally, conservative estimates of knot properties

required by ASTM D 3737 procedures were derived

for each proposed lumber grade using actual knot

measurements obtained on an independent sample of

Select Structural (SS), No. 2, and No. 3 grades of red

maple lumber (Green and McDonald, in preparation).

The visually graded lumber was graded according

to inspection rules established by the Northeastern

Lumber Manufacturers Association (NELMA 1986).
To achieve the bending stresses predicted with the

ASTM D 3737 procedures, special grades of lumber

were required in the outer 5 percent of the tension

laminations (e.g., 5 percent of 16 laminations equaled

1 lamination). In this study, one 2.0-1/6 lamination

of the red maple combinations was replaced with

a lamination meeting the special criteria given in

Table 3. These special grades, referred to as tension

lamination grades, were developed following ASTM

D 3737. For each beam size, a sample of 15 beams

was selected, which is statistically significant for a

10-percent difference in strength properties with a

90-percent level of confidence.

Procedures for Grading Lumber

and Characterizing Knots

Lumber Sawing and Grading

Lumber for manufacturing glulam beams was obtained

by sawing red maple (Acer rubrum) logs into green

8/4 (2-in.) dimensional material. The lumber was

conditioned at a commercial facility, using a predrier,

to moisture content of approximately 16 to 18 percent

over a 6-week period. Once the target moisture content

level was reached, the material was rough-planed to

a thickness of 1.75 in. The rough-sawn lumber was

then visually graded by NELMA rules and subdivided

into Select Structural, No. 1, No. 2, and No. 3 grades

(NELMA 1986). The lumber was subsequently shipped

to the laminator. Total processed log volume was

33.1 × 103 board feet (fbm).

The sawing yielded approximately 4,700, 6,650, and

14,100 fbm of 2 by 4, 2 by 6, and 2 by 8 material,

respectively. These board footage values were based

on two independent sawmill runs. The first sawmill

run was based on a higher proportion of lower grade

logs, which resulted in poor lumber recovery yield

for the larger 2 by 8 material. The second run was

more heavily predisposed to No. 1 and veneer-grade

logs, which enhanced 2 by 8 recovery. Logs in either

processing run were sawn leaving the center log portion

in the form of 4 by 4 or larger cants. Yields of the

various 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 were

biased with respect to sawing practices and removal of

cant log sections to minimize the inclusion of juvenile

wood.

Measurement of Lumber MOE

Stiffness was measured once the lumber attained an

average moisture content of 15 percent. The long-span

flatwise bending MOE was measured using a deflection

apparatus with the following specifications:

• steel strongback support assembly equipped with

radius supports

• mechanical lever crane for applying a constant

148-lb load

• calibrated linear variable differential transformer

(LVDT) for measuring midspan displacement

• digital voltmeter for reading output transducer

voltage

• portable laptop computer for data entry and storage

and 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 correction

was made for the apparent MOE calculation as a result

of the large span-to-depth ratio. The results of the

MOE tests were used to sort the lumber using the

criteria listed in Table 4.

The SS and No. 1 material was initially sorted to the

2.0-1/6, 2.0-1/3, or 1.8-1/3 grades using these criteria.

Material that did not meet the criteria was either not

used (higher stiffness) or added to the No. 2 grade

(lower stiffness). The No. 2 material was then sorted

to obtain additional amounts of 2.0-1/3 and 1.8-1/3

material. It was expected that much of the No. 2

material would not meet these grades and would be

used in the beam core. The sorting of the SS and No. 1

grades provided nearly all the E-rated material.

Although the lumber samples that were measured for

MOE were large, we wanted to determine the average MOE for the lumber specimens that actually appeared in the beam layups. We were able to do this

because the location of these specimens was specifically

mapped. The MOE averages for the lumber that appeared in the beam layups are presented in Table 5.

These results show that the average stiffness values of

the 2.0E and 1.8E lumber for each size were slightly

lower than the target values. Conversely, the average

stiffness of the No. 2 lumber for each size significantly

exceeded the value of 1.5 × 106 lb/in2 assumed in

Table 2.

Characterization of Knot Properties

To accurately analyze the beams for bending strength

using the ASTM D 3737 (ASTM 1991a) procedures,

knots were measured for each grade of lumber after

the lumber was sorted by MOE. Knots were measured

by estimating an equivalent “straight-through” knot

and determining the percentage of the lumber crosssection that the knots occupied. The knot properties

3
were measured for all the tension lamination material

and for representative samples of the remaining

lumber grades. Knot data were analyzed following the

principles in USDA Technical Bulletin 1069 (Freas and

Selbo 1954).

The knot properties calculated from the knot measurements are listed in Table 6. The data were based on a

minimum of 1,000 lineal fbm examined for each lamination grade for the three lumber widths combined.

Beam and End-Jointed

Lumber Tests

Forty-five beams (15 of each combination) were

manufactured along with extra specimens for endjointed lumber tests. The location of each lumber

piece was recorded on prepared beam maps so that

the lumber properties could later be related to beam

performance. In addition, the quality of the critical

tension laminations was assessed in relation to the

allowable knot and slope-of-grain properties, to

determine the relative qualities of the beams.

Procedures

Manufacture of the beams followed the normal

production procedures (ANSI 1983). Each grade of

lumber included a range of qualities permitted by

the grade. Lumber quality was random; the lumber

was not sorted to include high as opposed to low

quality material in any specific arrangement along

the lamination length. The general manufacturing

procedure was as follows:

1. Lumber pieces were continuously finger-jointed,

with the lamination ribbon cut to beam length.

Vertically oriented finger-joints were manufactured

with a melamine–formaldehyde adhesive under

radio-frequency cure. Special outer-zone laminations

were manufactured first, followed by production of

core plies to develop the beam depth profile. Endjoint geometry was finger length, 1.03 in.; pitch,

0.25 in.; and tip thickness, about 0.03 in. The

observed tip gap was approximately 0.038 in.

2. Laminations were planed prior to adhesive application for face bonding. Initial lamination thickness was reduced to 1.5 in. by removing 0.13 in. of

material from both faces.

3. The adhesive resin for face lamination was a roomtemperature curing resorcinol-formaldehyde.

Adhesive application was through a single glueline

with an 80.lb/1,000-ft2

 spread rate. Surface

adhesive was spread with a roll-coat applicator.

Open assembly time was not modified from that

typically used within the operation for Southern

Pine beam fabrication. Total closed-assembly time

to applied clamp pressure was approximately

50 min. Clamp pressure was similar to that used

for Southern Pine fabrication.

4. Adhesive cure was at ambient temperature (75°F to

80°F) under pressure for a minimum 12-h period.

Beams were dressed to a surface finish acceptable

under the category of industrial grade glulam.

Following manufacture, the beams were visually

inspected to assure conformance to ANSI A190.1

(ANSI 1983) and to determine the relative qualities

of the tension laminations in the midlength region

subjected to >85 percent of the maximum moment

during test. Using the maximum allowable strengthreducing characteristics listed in Table 3, a relative

rating system was developed to systematically assign

a quality to the tension lamination. Table 7 lists the

allowable percentages of lumber cross-sectional areas

that can be occupied by knots, the slope-of-grain

limitations, and the MOE restrictions for classification

of low, medium, or high quality.

Beam Test Results

Inspection of the beams following manufacture revealed

that two beams (beams RM8-5 and RM8-9) in the

16-Lam group had end joints in adjacent laminations in

the outer tension zone spaced closer than the 6 in. required by ANSI A190.1 (ANSI 1983). Also, one beam

of each combination had a tension lamination that

did not meet the visual criteria of Table 3 (beams

RM4-3, RM6-5, and RM8-10). However, the designated compression side of the two smaller beams

(RM4-3 and RM6-5) met the criteria, and they were

tested with the tension and compression sides reversed

(these were balanced combinations). It was not possible

to test the third beam (RM8-10) as a result of both the

unbalanced layup of the 16-Lam beam and the quality

of the compression-side lamination. Therefore, although

the 15 beams in the 16-Lam group were tested, only

12 were included in the final analysis.

The percentage of beams categorized as having

low, medium, or high quality tension laminations is

shown in Table 8. Additional details on the quality

of the individual tension laminations are provided in

Appendix A.

All the full-sized glulam beams were tested following

the procedures given in the ASTM Standard D198

(ASTM 1991b). The loading configuration used to test

the full-sized beams is illustrated in Figure 2. Physical

properties (moisture content, weight, and dimensions),

stiffness properties (full-span deflections), and failure

4
Figure 2—Loading configurations for bending

tests

load were measured for each beam. In addition, notes

were taken on failures, typical failure types were

photographed, and high-speed videotapes were made

of failures on selected beams. Moisture contents were

measured with a resistance-type moisture meter near

the midspan of all laminations after ultimate failure of

the beams. Weights were measured on a mobile scale to

the nearest 10-lb increment. Dimensions were measured

at each load point.

During the application of load, beam deflections were

measured using a precision rule (0.02-in. markings)

attached to the beam. Deflections were recorded at

mid-depth with respect to a stringline attached over

each support. The readings were taken at specified

load increments with the use of a surveyor’s scope;

this allowed the recorder to take readings to the

nearest 0.01 in. During the load-deflection readings,

elapsed time readings were also taken. The purpose

for the elapsed time readings was to record when

initial cracking occurred (noise) and when compression

wrinkling was first detected. The time-of-occurrence

readings were then traced back to applied load.

After the beams failed, detailed descriptions of the

failure propagations were recorded (Fig. 3), along

with an assessment of the cause of failure (end joint,

Figure 3—Mapping of failure propagations in

glulam beams. (M91 0266-50)

Figure 4—Cumulative distribution of modulus of

rupture (MOR) for three sizes of glulam beams.

knot, etc.). Each beam failure was photographed for

future reference. Modulus of rupture (MOR) and MOE

were calculated using standard flexural formulas. Dead

load stress was included in the MOR calculations. The

MOE values were calculated based on the slope of the

load-deflection curve determined by a linear regression

up to design load.

Strength and Stiffness

Results of the bending tests on the beams are summarized in Table 9. Individual beam results are given

in Appendix B. Figure 4 compares the cumulative

distribution function of MOR for the 8-, 12-, and

16-lamination beams.

Beam Failure

Most beams failed abruptly at ultimate load and many

emitted cracking sounds as the ultimate load was

approached. Several beams exhibited compression

5
wrinkling at or between the load points prior to maximum load. All beams ruptured throughout the tension

zone near or within the constant moment region. Although it was not possible to positively identify the initial point of failure for all beams, estimates were made

of the mechanism that triggered the initial cause of failure. These results are summarized in Table 10. Beam

failures are described in detail in Appendixes B and C.

Most beams failed through either clear wood or

slope-of-grain regions in the tension laminations.

The failure of up to two beams in each group was

attributed solely to the finger joints, whereas several

other beams failed by a combination of end joints

with other characteristics. About one-half the beams

exhibited areas of shallow or little wood failure at the

bonds between laminations as the rupture progressed.

These failures are referred to as glueline failures

(GLF) in Appendix B. Although these face bonds

were not believed to affect the beam strength, they

could hamper long-term durability. The face bonds

are not perceived to be critical in the development of

commercial red maple glulam lumber. Examination of

the failed glueline areas suggested that the problem

of durability may well be resolved through slight

modification of the lamination assembly, such as slower

planing speeds and higher face-bonding pressures

(private conversation with Bryan River, Research

Forest Products Technologist, FPL).

End-Jointed Lumber Tests

End-jointed lumber specimens from each grade and size

were tested in tension. The test specimens were 8-ft

long with the end joint located near midspan. Prior to

testing, specimens were face- and edge-planed to the

same dimensions of the laminating lumber used in the

glulam beams.

For the purpose of characterizing lumber properties

for probabilistic models (Hernandez and others 1992),

short-span stiffness properties were obtained on the

2-ft lumber segment on each side of the joint and on

the 2-ft segment across the joint. These bending tests

were conducted on a screw-driven bending machine

with a load cell and LVDT setup for measuring the

shear-free deflections between the load points. The

loading configuration for the bending test was 5.5 ft

between the supports and 2 ft between the applied

load points. Load-deflection readings were taken in

5-lb increments. The 2 by 4 specimens were loaded to

a maximum load of 300 lb and the 2 by 6 and 2 by 8

specimens to a maximum load of 400 lb. The MOE

values were calculated using the slope of the loaddeflection readings.

6

Figure 5—Cumulative distribution of tensile

strength of finger-jointed 2.0E-1/6 grade lumber

for nominal 2 by 4, 2 by 6, and 2 by 8 material.

After the nondestructive static bending tests, the

specimens were tested to failure in tension according

to the procedures specified in the ASTM Standard

D 198 (ASTM 1991b), which specify a 5- to 10-min

time-to-failure. Normal quality control practices for

testing end joints would follow the AITC 200 (1991a)

procedures, which specify a 2-min time-to-failure. End

joints for this research project were tested according to

the ASTM D 198 (ASTM 1991b) procedures as a result

of the similar failure times of the full-sized beams. The

tension testing machine was adjusted such that the

grips were 30 in. apart. The specimens were placed

in the machine with end joints located near the center

of the 30-in. span. A 30-in. span was used because of

the minimum span limitations of the tension machine;

thus, the 24-in. segment tested in bending was centered

within the 30-in. span. After testing, the short-span

stiffness data and the visual grade of the end-joint

specimens between the grips were used to reclassify

the end joints with respect to grade. The strength

and stiffness data provided information to relate the

relationship of the individual performance of end joints

to their performance in the beams.

Results of tension tests on the end-jointed tension

lamination material are given in Table 11 and shown in

Figure 5. Results on tests of the other grades of finger

joints are in Appendix D.

Analysis

The glulam beam strength and stiffness results in

Table 9 were calculated assuming both the normal

and lognormal distributions. However, to analyze

the data, the ASTM D 3737 Standard (ASTM

1991a) recommends that a lognormal distribution be
used. Therefore, our analysis assumes a lognormal

distribution.

Effect of Beam Size

By evaluating three beam sizes, it was possible to

determine if beam volume exerted a significant effect on

the strength of red maple beams. The results indicated

that the small beams (8-Lam) had significantly higher

strength than the other two sizes (Table 9). However,

there was no significant difference between the strength

of the other two sizes (12- and 16-Lam). The following

equation is used in the National Design Specification

for Structural Wood (NFPA 1991) to account for the

effect of varying beam size on bending strength.

(1)

Figure 6—Variation in beam MOR with beam

volume showing a line approximating an

exponent 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 the

relative adjustments for width, length, and depth.

was conducted. First, the ratio between the volume

effect factors of each beam size was determined using

both the 1/10 and 1/20 exponents. Next, the ratio between the averages of the various paired groupings of

beams were determined along with a confidence interval using the procedures described in Appendix II of an

FPL report (Wolfe and Moody 1978). Table 12 lists the

results of this analysis.

When width, depth, and length are combined to obtain

volume, 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 using

both 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, the

predicted results with the 1/10 exponent were at the

edge of the confidence interval whereas those with the

1/20 exponent were near the middle of the confidence

interval.

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 of

x = y = z = 1/10 adequately explained the variation

in strength for Douglas-fir beams. A volume effect

equation has been adopted by ASTM Committee

Section D07.02.02 with exponents x = y = z = 1/10

for all species. The American Institute of Timber

Construction (AITC), on the other hand, has adopted

the x = y = z = 1/10 exponents for all species of

glulam except Southern Pine. The parameters adopted

by AITC for Southern Pine are x = y = z = 1/20

(AITC 1991b).

Next, a regression analysis was conducted to determine

a single exponent to use for x, y, and z that best fit

all the data. This exponent was 0.071. The resulting

equation is plotted with the bending strength data

in Figure 6. Thus, for further analysis, an exponent

value of 0.071 was used to adjust the beam results to a

standard volume.

Design Levels

To determine the most appropriate method of accounting for variation in beam strength resulting from beam

size. a confidence interval on the ratio of the beam sizes

All beam strengths were adjusted to a standard beam

size of 5.125 in. by 12 in. by 21 ft using the best fit

volume effect relationship (exponent of 0.071). Then,

results were pooled and analyzed to determine the

appropriate design level using the procedures of ASTM

D 2915 (ASTM 1991c). A lognormal distribution was

assumed and the 5th percentile (75 percent tolerance

7
Figure 7—Distribution of MOR adjusted to

standard beam size and compared to lognormal

distribution.

limit) was adjusted by dividing by 2.1 to obtain the

design level. The 2.1 factor includes adjustments for

safety and load duration effects. Figure 7 shows that

the data closely fit the assumed lognormal distribution.

Results shown in Table 13 indicate that the calculated

adjusted 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 was

essentially 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

Strength

The same procedure used to design the combinations

was used to reanalyze them with the actual MOE and

knot data (Table 5). Because the actual knot sizes were

significantly smaller than that assumed (Table 2), the

calculated design stress level exceeded the 2,400 lb/in2

value originally predicted.

A comparison of the actual results with those from

the reanalysis indicated that the actual results still

exceeded the predicted values. The next step in the

reanalysis was to permit the bending stress index value

to be increased from the 3,250 lb/in2

 value assumed

in Table 2. An analysis of the bending stress index

values is presented in Figure 8; it shows that a value of

at least 3,500 lb/in2 is justified for the 2.0E1/6 grade

lumber used for the outer tension lamination.

Figure B—Analysis of bending stress index

values for 2.0E grade red maple lumber based

on results of 42 glulam beam tests.

Stiffness

Beam stiffness can be predicted by using the actual

stiffness data for the lumber (Table 5) and the

procedures of ASTM D 3737 (ASTM 1991a). Results

are compared in Table 14 and show that the beam

MOE values were within 2 percent of the values

predicted for the three sizes.

Comparison of Beam and End-Joint

Bending Strength

According to ANSI A190.1, the required end-joint

strength is 1.67 times the nominal design strength in

bending. By pooling all of the joint-associated tensile

strength data (lumber size exerted little apparent

effect; Table 10), a 5th percentile (75 percent tolerance

limit using the lognormal distribution) of 5,590 lb/in2

was calculated. This value greatly exceeds the value of

4,000 lb/in2

 commonly targeted for 24F (2,400 lb/in2)

beams. The ratio of the 5th percentile (75 percent

tolerance limit) of the combined end-joint data to the

adjusted 5th percentile (75 percent tolerance limit) of

the combined beam data in Table 13 is 1.78, which is

slightly higher than the ANSI A190.1 requirements.

Conclusions

1. Structural glued-laminated (glulam) timber beams

manufactured with E-rated red maple lumber in

the outer zones and No. 2 lumber in the core met

or exceeded the target bending design stress of

2,400 lb/in2 and modulus of elasticity (MOE) of

1.8 × 106

 lb/in2.

8
2. A red maple combination of glulam timber with

design properties of at least 2,400 lb/in2

 in bending

and MOE of 1.8 × 106

 lb/in2 is technically feasible.

Both the lumber grades and the finger joints used

would provide adequate strength and stiffness for

this combination.

3. The ASTM D 3737 procedures developed for

softwood species accurately predict beam stiffness

and provide conservative strength estimates for

beams made with E-rated red maple lumber.

References

AITC. 1979. Determination of design values for

structural glued laminated timber. AITC 117-

79. Vancouver, WA: American Institute of Timber

Construction.

AITC. 1985. Standard specifications for hardwood

glued laminated timber. AITC 119-85. Vancouver,

WA: American Institute of Timber Construction.

AITC. 1988. Standard specifications for structural

glued-laminated timber of softwood species. AITC

117-88—Manufacturing, Vancouver, WA: American

Institute of Timber Construction.

AITC. 1991a. Inspection manual. AITC 200-91. Vancouver, WA: American Institute of Timber Construction.

AITC. 1991b. Use of a volume effect factor in the design of glued laminated timber beams. Tech. Note 21,

October. Vancouver, WA: American Institute of Timber Construction.

ANSI. 1983. Structural glued laminated timber. ANSI

A190.1. Englewood, CO: American National Standards

Institute.

ASTM. 1991a. Standard test method for establishing

stresses for structural glued-laminated timber (glulam).

ASTM D 3737-91. Philadelphia, PA: American Society

for Testing and Materials.

ASTM. 1991b. Standard methods of static tests of timbers in structural sizes. ASTM D198-84. Philadelphia,

PA: American Society for Testing and Materials.

ASTM. 1991c. Standard practice for evaluating

allowable properties for grades of structural lumber.

ASTM D2915-90. Philadelphia, PA: American Society

for Testing and Materials.

Forest Products Laboratory. 1987. Wood handhook–

Wood as an engineering material. Agric. Handb.

72 (Rev.). Washington, DC: U.S. Department of

Agriculture. 466 p.

Freas, A.D.; Selbo, M.L. 1954. Fabrication and

design of glued laminated wood structural members.

Tech. Bull. 1069. Madison, WI: U.S. Department

of Agriculture, Forest Service, Forest Products

Laboratory.

Hernander, R.; Bender, D.A.; Richburg, B.A.; Kline,

K.S. 1992. Probabilistic modeling of glued-laminated

timber 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 special

project SS-047-Preliminary refinement of hardwood

design values. Harrisburg, PA: Pennsylvania Dept. of

Transportation.

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 on

timber engineering; 1988 September; Seattle, WA.

Madison, WI: Forest Products Research Society:

892-898.

Moody, R.C.; Falk, R.; Williamson, T. 1990. Strength

of glulam beams-volume effects. Vol. 1. In: Proceedings of the international timber engineering conference;

1990 October 23-25; Tokyo. Tokyo: Steering Committee of the International Timber Engineering Conference: 176-182.

NELMA. 1986. Grading rules for northeastern lumber.

Cumberland Center, ME: Northeastern Lumber

Manufacturers Association.

NFPA. 1991. National design specification for structural wood. Washington, DC: National Forest Products

Association.

Wolfe, R.W.; Moody; R.C. 1978. Bending strength

of water-soaked glued-laminated beams. Res. Pap.

FPL-RP-307. Madison, WI: U.S. Department

of Agriculture, Forest Service, Forest Products

Laboratory. 

9
Table 1—SI conversion factors

Conversion

English 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 maple

lumber grades for ASTM D 3737 procedures

Bending

Lamin- MOE stress

ation (× 106 +ha

index

grade lb/in2

) (%) (%) (lb/in2

)

b

2.0-1/6 2.0 0.27 12.9 3,250

2.0-1/3 2.0 2.63 31.8 3,250

1.8-1/3 1.8 2.63 31.8 2,800

No. 2 1.5 2.63 31.8 2,500

= average of sum of all knot sizes within

each 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 tension

lamination criteriaa

Beam type and

lamination criterion

Maximum

allowable

characteristic

8-Lam

Edge knot + grain deviation

Center knot + grain deviation

Slope of grain

12-Lam

40 percent

45 percent

1:14

Edge knot + grain deviation

Center knot + grain deviation

Slope of grain

16-Lam

30 percent

33 percent

1:16

Edge knot + grain deviation 30 percent

Center knot + grain deviation 33 percent

Slope of grain 1:16

aASTM 1991a. Knots plus grain deviations

are given in percentage of cross section.
Table 4—Target MOE values and sorting scheme Table 6—Knot properties of laminating lumber

Lamination

grade 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 grade

Edge 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 type

and grade

Sample

size

Average

MOE

(× 106

lb/in2)

COVa

(%)

2 by 4 Lumber

2.0-1/6

2.0-1/3

1.8-1/3

No. 2

2 by 6 Lumber

2.0-1/6

2.0-1/3

1.8-1/3

No. 2

2 by 8 Lumber

2.0-1/6

2.0-1/3

1.8-1/3

No. 2

39 1.96 5.9

40 1.96 5.8

80 1.72 8.2

50 1.80 16.2

52 1.93 7.7

48 1.92 8.9

215 1.74 10.6

50 1.73 14.3

141 1.93 9.8

144 1.90 8.5

193 1.74 10.3

50 1.69 14.9

Lumber type

and grade

Lineal

footage

(ft)

+ha

(%)

2 by 4 Lumber

2.0-1/6 386 0.2 14.8

2.0-1/3 420 0.3 16.8

1.8-1/3 524 0.6 25.5

No. 2 442 0.9 29.2

2 by 6 Lumber

2&1/6 572 0.1 13.6

2.0-1/3 488 0.4 18.5

1.8-1/3 376 0.1 7.1

No. 2 362 2.0 35.3

2 by 8 Lumber

2.0-1/6 304 0.5 11.2

2.0-1/3 334 0.7 16.6

1.8-1/3 436 0.1 7.0

No. 2 666 1.7 33.6

= average of sum of all knot sizes within

each 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 and

lamination criterion

D 3737

allowable

value

Lamination quality

Lowa Medium High

8-Lam

Edge knot + grain deviation

Center knot + grain deviation

Slope of grain

MOE (× 106 lb/in2)

40% >30%

45% >30%

1:14 >1:16

2.0E (avg.) <1.7E w/char

15%-30%

15%-30%

1:16-1:18

<1.7E and clear

12-Lam

Edge knot + grain deviation 30% >20% 10%-20%

Center knot + grain deviation 33% >20% 10%-20%

Slope of grain 1:16 >1:18 1:18-1:20

MOE (× 106 lb/in2) 2.0E (avg.) <1.7E w/char <1.7E and clear

16-Lam

Edge knot + grain deviation

Center knot + grain deviation

Slope of grain

MOE (× 106 lb/in2)

30% >20% 10%-20% <10%

33% >20% 10%-20% <10%

1:16 >1:18 1:18-1:20 >1:20

2.0E (avg.) <1.7E w/char <1.7E and clear —

<15%

<15%

>1:18

<10%

<10%

>1:20

a

w/char designates lumber with characteristics. For example, if a board

has an MOE of <1.7E and edge-knot, center-knot, or slope-of-grain

characteristics, it is classified as low quality.

Table 8—Relative quality of tension laminations in midlength region of beams

Percentage of beams

by lamination quality

Beam Sample

type size Low Medium High

8-Lam 15 20 27 53

12-Lam 15 33 40 27

16-Lama 12 75 17 8

a

Three beams did not meet manufacturing

12

 or grade criteria.
Table 9—Results of bending tests on red maple glulam beams

Property 7-Lam 12-Lam 16-Lama

16-Lam

Sample size

Moisture content (%)

15 15

12 12

Normal distribution

Average MOR (lb/in2) 9,070 7,970

COV of MOR (%) 13.8 12.4

M0R0.05 at 75% tolerance 6,580 6,000

Average MOE (× 106 lb/in2) 1.78 1.77

COV of MOE (%) 4.3 3.0

Lognormal distribution

Average MOR (lb/in2) 9,080 7,980

COV of MOR (%) 14.4 12.1

MOR0.05 at 75% tolerance 6,760 6,230

15

12

7,890 7,840

13.9 14.3

5,720 5,540

1.78 1.78

2.5 2.7

7910 7,860

15.1 15.8

5,800 5,630

12

12

aData in column four exclude the 16-Lam beams that

either did not meet tension lamination requirements

(RM8-10) or end-joint spacing requirements (RM8-5, RM8-9).

Table 10—Estimated initial cause of

glulam beam failures

Number of beams

Failure type 8-Lam 12-Lam 16-Lam

Compression followed 4 1 3

by tension

Tension in strength- 2 1 3

reducing characteristic

Tension in lumber 2 2 2

Tension in end joint 7 11 4

13
Table 11—Results of tension tests on end-jointed

red maple tension lamination material using

lognormal distributiona

Property

All sizes

2 by 4 2 by 6 2 by 8 combined

All specimens

Sample size 20 27 19 66

Average TS (lb/in2) 8,310 8,690 8,120 8,410

COV TS (%) 28.4 20.7 16.8 22.2

Specimens with failure involving end joint

Sample Size 19 26 18 63

Average SGb

0.57 0.57 0.56 0.57

Average MC (%) 8.6 8.6 7.8 8.3

Average TS (lb/in2) 8,470 8,720 8,010 8,430

COV 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 different

volume effect exponents

Ratio of predicted

mean MOR

Ratio of actual

x=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)

a

90 percent confidence interval

Table 13—Adjusted glulam beam

bending strength resultsa

Property Result

Sample size 42

Average MOR (lb/in2) 8,590

COV (%) 13.8

5th percentile (75% tolerance limit) 6,620

Adjusted 5% tolerance limit 3,150

aData adjusted to standard dimensions of

5.125 in. width by 12 in. depth by 21 ft length.

Table 14—Comparison of actual and predicted

MOE values based on actual lumber properties

Beam

type

Actual Predicted Ratio

MOE (A) MOE (P) of A/P

8-Lam 1.78 1.78 1.00

12-Lam 1.77 1.73 1.02

16-Lam 1.78 1.74 1.02

14
Appendix A

Properties of Red Maple Lumber Used for

Midlength Region of Outer Tension Lamination

Table Al-Properties of 2 by 4 lumber

used in tension lamination

Relative

quality of

Tables A1 through A3 list the lumber properties used

for the tension lamination of 8-Lam, 12-Lam, and 16-

Lam beams, respectively. All lumber ranged from 13 to

Beam midlength

no. MOE Characteristica

regionb

RM4-1 1.89 Clear

16 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

2.02

2.03

1.89

2.08

1.90

1.84

1.95

1.87

2.03

2.18

1.92

2.19

1.92

2.02

1.97

1.99

2.07

2.20

1.82

1.93

2.11

1.89

1.99

1.86

2.12

1:16 GS

Clear

5% GD

1:10 GS

Clear

40% CK + GD

Clear

Clear

Clear

Clear

Clear

Clear

Clear

30% EK + GD

and 1:16 GS

33% EK + GD

Clear

Clear

Clear

Clear

25% EK + GD

Clear

Clear

Clear

Blue stain

1:14 GS

Clear

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 of

below-grade tension lamination.

15
Table A2—Properties of 2 by 6 lumber

used in tension lamination

Relative

quality of

Beam midlength

no. MOE Characteristic region

RM6-1 1.97 Clear

2.19

RM6-2 1.84

1.71

RM6-3 1.95

1.70

RM6-4 1.93

1.84

RM6-5a2.04

1.80

RM6-6 2.01

1.84

RM6-7 1.64

2.00

RM6-8 2.11

1.81

RM6-9 2.03

1.91

RM6-10 1.98

2.25

RM6-11 2.02

2.04

RM6-12 1.88

1.85

RM6-13 1.65

RM6-14 1.98

1.97

RM6-15 1.83

1.90

20% GD

Clear

Clear

Clear

Low MOE

30% EK + GD

1:8-1:10 GS

Clear

1:16 GS

1:6-1:8 Edge GS

Clear

Low MOE

Clear

Clear

33% EK + GD

1:12 GS

1:16 GS

Clear

Clear

1:12 GS

Clear

Clear

Clear

Worm holes

Low MOE

1:18 GS

Clear

Clear

Clear

M

H

M

L

M

L

M

L

L

H

L

H

M

M

H

aTested upside down because of

below-grade tension lamination.

Table A3—Properties of 2 by 8 lumber

used in tension lamination

Beam

no. MOE Characteristic

Relative

quality of

midlength

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

2.22

2.12

2.14

2.21

2.13

2.19

2.21

2.02

2.00

1.96

2.06

2.01

1.90

2.03

1.56

2.10

1.64

1.88

1.67

1.97

1.71

1.55

1.71

1.62

2.04

1.81

1.90

2.08

2.54

1.40

1.84

1.88

1.79

1.74

1.98

1.75

1.96

Clear

Clear

Clear

Clear

40% GD

35% CK + GD

Clear

Clear

1:6 GS

1:8 GS

Clear

50% EK + GD

Clear

Clear

50% GD + Low MOE

30% EK + GD

Clear + Low MOE

1:12 Edge GS

Clear

1:8 Edge GS

1:12 GS

1:12 GS + Low MOE

Clear

Clear + Low MOE

Clear

1:16 GS + 20% GD

Clear

Clear

1:10 GS + 10% CK

+GD

40% CK + GD

15% CK + GD

30% CK + GD

1:8-1:11 GS

1:13 GS

10% GD

Clear

Clear

H

L

L

L

L

L

L

L

L

M

L

M

L

L

H

aBelow-grade tension lamination. Beams were

tested in their original orientation as a result

of unbalanced layup.

16
Appendix B

Glulam Beam Results and Failure Descriptions

Tables B1 through B3 list the results of bending tests

on 8-Lam, 12-Lam, and 16-Lam beams, respectively.

17
Table B1—Results of bending tests on 8-Lam red maple beams

Beam

no.

Dimension Beam Beam

Time to Load at MOR

b MOE Failure

Width Depth MC

a

 failure failure (× 10

3

 (× 10

3

type

c

(in.) (in.) (%) (min:s) (×10

3

 lb) lb/in

2

) lb/in

2

) (EJ/Lam) Comment

d

RM4-1 3.00 12.03 12

2.91 12.03 12

2.98 12.00 10

3.00 12.03 13

2.99 12.50 12

3.00 12.03 12

3.00 12.03 12

2.98 12.07 12

2.98 12.07 13

5:40 14.68

RM4-2 10:30 17.72

RM4-3 6:39 12.08 7.645 1.73

RM4-4 9:16 14.52 9.060 1.62

RM4-5 10:02 16.24

RM4-6 8:36 13.62

RM4-7 12:38 15.46

RM4-8 8:03 14.72

RM4-9 6:32 12.16

RM4-10 3.01 12.03 14 • 14:02 17.04

9.173

11.162

10.131

8.501

9.645

9.185

7.580

10.592

1.77

1.87

1.81

1.75

1.75

1.77

1.70

1.86

Lam Mostly TL failure; 5% EJ failure at 10.5 ft, propagated thro

observed GLF from 6.5 to 11 ft between 2d and 3d Lams.

Lam Noise at 17 × 10

3

 lb; mostly TL failure from 11 to 12 ft; 30

in TL at 12.8 ft, propagated through EJ in 2nd Lam at 10

Lam Beam tested upside-down due to below-grade TL; TL failur

6 to 7 ft, propagated to GLF between 2d and 3d Lams from 

Lam Noise at 11.5 × 10

3

 lb, mostly TL failure at 9.8 ft; 25% EJ 

at 7.8 ft.

Lam Noise at 14 × 10

3

 lb; brittle TL failure at 11.9 ft; more TL 

5 to 7 ft, propagated to EJ (100%) in 2d Lam at 12.5 ft.

EJ/Lam Noise at 12.24 × 10

3

 lb; failure in TL from 8 to 13 ft; also 

failure in TL at 10.5 ft; GLF between 1st and 2d Lams from 

Lam Noise at 12.5 × 10

3

 lb; compression wrinkling in 8 to 12 ft r

initiated at 13.5 × 10

3

 lb through failure; all TL failure at 

Lam Noise at 14.2 × 10

3

 lb; TL failure (GS) from 9 to 12 ft; seve

gluelines between 4th and 5th Lams.

Lam Noise at 10.2 × 10

3

 lb; 10% EJ failure in TL at 10.6 ft, pro

through EJ in 3d Lam at 11.8 ft.

Lam TL failure from 12.5 to 13.8 ft, propagated to EJ (5%) in 2

9.6 ft; compression wrinkling in 8 to 12 ft region, initiated 

10

3

 lb.

(Page 
Table B1—Results of bending tests on 8-Lam red maple beams-con.

Beam

no.

Dimension Beam Beam

Time to Load at MOR

b MOE Failure

Width Depth MC

a

failure failure (× 10

3

 (× 10

3

type

c

(in.) (in.) (%) (min:s) (× 10

3

 lb) lb/in

2

) lb/in

2

) (EJ/Lam) Comment

d

RM4-11 3.00 12.07 12 8:23 15.18 9.410 1.88 EJ No noise until failure; 100% EJ failure in TL at 12.5 ft; GL

4th and 5th Lams.

RM4-12 2.95 12.05 12 11:04 16.12 10.192 1.75 EJ No noise until failure; 100% EJ failure in TL at 10.3 ft; br

through 2d and 3d Lams; GLF between 5th & 6th and 6th 

RM4-13 2.97 12.05 13 5:15 10.68 6.717 1.77 Lam No noise until failure; brittle TL failure at 11.3 ft; GLF be

3d and 5th & 6th Lams.

RM4-14 2.97 12.03 12 8:13 14.98 9.441 1.92 Lam Noise at 10.7 × 10

3

 lb; compression wrinkling, initiated at 

at 12 ft; brittle TL failure at 10.5 ft; GLF between 2d and 

13 to 17 ft.

RM4-15 3.00 12.05 13 6:45 12.23 7.611 1.81 Lam Noise at 6.5 × 10

3

 lb; TL failure at 7 to 10 ft to EJ (25%) 

11.3 ft; slight compression wrinkling at failure at 12.5 ft.

aMC is moisture content.

bMOR calculations included dead load stress.

cEJ is end joint, GLF glueline failure, GS slope of grain, and TL tension lamination.

(Page 
Table B2—Results of bending tests on 12-Lam red maple beams

Beam

no.

Dimension Beam Beam

Time to Load at MOR

a MOE Failure

Width Depth MC failure failure (× 10

3

 (× 10

3

type

(in.) (in.) (%) (min:s) (× 10

3

 lb) lb/in

2

) lb/in

2

) (EJ/Lam) Comment

b

RM6-1 5:40 28.36 7.16 1.85 Lam

RM6-2 7:23 33.75 8.503 1.78 EJ

RM6-3 9:38 40.99 10.240 1.73 EJ

RM6-4 5:31 27.89 6.982 1.76 EJ/Lam

RM6-5

5.00 18.09 12

5.00 18.06 12

5.00 18.09 11

5.00 18.10 11

5.00 18.10 12 6:23 31.20 7.808 1.73 EJ/Lam

RM6-6 5.00 18.05 12 8:15 35.60 8.945 1.78 EJ/Lam

RM6-7 5.00 18.05 13

5.00 18.05 13

5.00 18.06 12

4.95 18.06 11

8:24 36.51 9.172 1.78 Lam

RM6-8 7:08 32.00 8.050 1.78 Lam

RM6-9 5:20 27.65 6.961 1.83 EJ/Lam

RM6-10 5:47 28.59 7.267 1.78 EJ/Lam

Noise at 15 × 10

3

 lb; TL failure at 12 to 17 ft; 5% EJ failur

11.6 ft.

Noise at 15 × 10

3

 lb; 60% EJ failure in TL at 12.5 ft; GLF 

and 8th Lams from 6 to 8 ft.

Noise at 23 × 10

3

 lb; 100% EJ failure in TL at 15 ft; compr

wrinkling at failure at 15.3 and 17.2 ft.

Noise St 13 × 10

3

 lb; 50% EJ failure in TL at 16.3 ft, prop

100% EJ failure in 3d Lam at 17.3 ft.

Beam tested upside-down due to below-grade TL; noise at 

lb; 40% EJ failure in TL at 17.5 ft; several GLFs between 6

Lams.

Noise at 14.2 × 10

3

 lb; 70% EJ failure in TL at 20.6 ft, also 

at 17.5 ft; GLF between 5th and 6th Lams; secondary EJ fa

in 2nd Lam at 16.6 ft.

Noise at 26 × 10

3

 lb; all TL failure from 13 to 14 ft; GLF b

and 5th Lams from 0 to 9 ft.

Noise at 18.5 × 10

3

 lb; TL failure (GD) from 14 to 16 ft; G

6th and 7th Lams from 22 to 25 ft.

Noise at 21.5 × 10

3

 lb; 30% EJ failure in TL at 14.5 ft, pro

through EJ (50%) in 2d Lam at 16 ft.

Noise at 21 × 10

3

 lb; 40% EJ failure in TL at 11.8 ft, also T

from 11.8 to 14.5 ft, then to EJ (50%) in 2d Lam at 14.3 ft

between 4th and 5th Lams.

(Page 
Table B2—Results of bending tests on 12-Lam red maple beams-con.

Dimension Beam Beam

Time to Load at MOR

a MOE Failure

Beam Width Depth MC failure failure (× 10

3

 (× 10

3

type

no. (in.) (in.) (%) (min:s) (× 10

3

 lb) lb/in

2

) lb/in

2

) (EJ/Lam) Comment

b

RM6-11 5.00 18.10 10 5:07 26.64 6.681 1.82 Lam Noise at 25 × 10

3

 lb; mostly TL failure at 16.5 ft; 5% EJ fail

GLF between 1st and 2d Lams from 11 to 16 ft.

RM6-12 5.00 18.10 11 8:38 34.90 8.723 1.67 EJ/Lam Noise at 16.5 × 10

3

 lb; 25% EJ failure at 17.6 ft, to 100% EJ 

2d Lam at 18.3 ft; GLF between 4th and 5th Lams from 21 t

RM6-13 4.95 18.05 12 6:22 30.90 7.855 1.79 Lam Noise at 23.5 × 10

3

 lb; all TL failure at 14.3 ft, to 100% EJ f

Lam at 14.5 ft; GLF between 2d and 3d Lams from 12 to 14 

RM6-14 5.00 18.05 13 5:47 29.00 7.304 1.76 EJ Noise at 17 × 10

3

 lb; 75% EJ failure in TL at 11.3 ft, propag

30% EJ failure in 4th Lam at 17.7 ft.

RM6-15 5.00 18.08 12 7:15 31.71 7.952 1.67 EJ/Lam Noise at 9.5 × 10

3

 lb; 100% EJ failure in TL at 11.7 ft; TL f

9 to 11.7 ft; GLF between 1st and 2d Lams.

aMOR calculations included dead load stress.

bEJ is end joint, GD grain direction, GLF glueline failure, GS slope of grain, and TL tension lamination.

(Page 2 
Table B3—Results of bending tests on 16-Lam red maple beams

Beam

no.

Dimension Beam Beam

Time to Load at MOR

a MOE Failure

Width Depth MC failure failure (× 10

3

 (× 10

3

type

(in.) (in.) (%) (min:s) (× 10

3

 lb) lb/in

2

) lb/in

2

) (EJ/Lam) Comment

b

RM8-1

RM8-2

8:52 69.60 9.690 1.82 Lam

6:25 57.00 7.980 1.82 Lam

RM8-3 6:52 60.00 8.399 1.79 EJ

RM8-4

RM8-5

5:15 47.50 6.697 1.77 EJ/Lam

8:36 48.50 6.907 1.75 Lam

RM8-6 12:38 54.30 7.681 1.77 Lam

RM8-7

6.75 24.12 14

6.75 24.09 11

6.74 24.09 11

6.70 24.13 11

6.70 24.00 12

6.75 23.97 12

6.75 24.00 13

6.75 23.94 13

6.75 23.94 12

8:03 59.20 8.342 1.78 EJ/Lam

RM8-8 6:32 50.60 7.184 1.81

RMB-9 14:02 58.00 8.217

RM8-10 6.75 24.20 11 8:07 66.50 9.202

1.77

1.79

Lam

Lam

Noise at 43 × 10

3

 lb; TL failure from 16 to 20 ft.

Noise at 41 × 10

3

 lb; TL failure (GD) at 24.5 ft, propagated 

failure in 2d Lam at 24 ft.

Noise at 43 × 10

3

 lb; 100% EJ failure in TL at 18.3 ft; compr

wrinkling at failure at 22 ft.

Noise at 13 × 10

3

 lb; 50% EJ failure in TL at 25 ft.

Noise at 20.5 × 10

3

 lb; stacked EJ in Lams 2 and 3 (18.7 ft a

18.6 ft)

c

; joints not associated in failure–all TL failure from 

Noise at 18 × 10

3

 lb; TL failure (GD) at 16.5 ft, propagated 

failure in 2d Lam at 17 ft.

Noise at 20 × 10

3

 lb; 75% EJ failure in TL at 18 ft; 1:12 edg

at 17.5 ft leading into 75% EJ failure in 2d Lam at 17 ft.

Noise at 38 × 10

3

 lb; TL failure (GS) from 20 to 21 ft, propa

80% EJ failure in 2nd Lam at 20.5 ft.

Noise at 33 × 10

3

 lb; 10% EJ failure in TL at 20 ft, propagat

EJ (100%) in 2d Lam at 22.5 ft; compression wrinkling at fai

Lam at 19 ft; EJ stacked in 1st and 2nd Lams at 12 ft–not i

failure.

c

Noise at 34 × 10

3

 lb; all TL failure at 15 ft, propagated to 15

failure in 2d Lam at 14 ft; GLF between 4th and 5th Lams; 

meet criteria.

(Page 1 
Table B3—Results of bending tests on 16-Lam red maple beams—con.

Dimension Beam Beam

Time to Load at MOR

a

 MOE Failure

Beam Width Depth MC failure failure (× 10

3

 (× 10

3

type

no. (in.) (in,) (%) (min:s) (× 10

3

 lb) lb/in

2

) lb/in

2

) (EJ/Lam) Comment

b

RM8-11 6.75 24.03 10 6:28 54.10 7.615 1.87 EJ/Lam Noise at 22 × 10

3

 lb; 80% EJ failure in TL at 15.5 ft, propaga

15% EJ failure in 2d Lam at 19.5 ft; GLF between 3d and 4th 

from 1 to 7 ft.

RM8-12 6.75 24.08 11 5:15 59.50 8.328 1.75 EJ Noise at 38 × 10

3

 lb; 100% EJ failure in TL at 22.5 ft; compr

wrinkling first detected in top Lam at 53 × 10

3

 lb.

RM8-13 6.75 24.00 12 8:13 36.60 5.203 1.68 EJ/Lam Noise at 28 × 10

3

 lb; 50% EJ failure in TL at 14 ft; GLF betw

and 8th Lams from 24 to 30 ft.

RM8-14 6.75 24.00 13 7:40 59.00 8.313 1.75 EJ Noise at 34.5 × 10

3

 lb; 95% EJ failure in TL at 15.5 ft, propa

25% EJ failure in 2d Lam at 17 ft; compression wrinkling firs

in top Lam at 55 × 10

3

 lb; GLF between 9th and 10th Lams 

33 ft.

RMB-15 6.75 24.00 12 7:33 61.50 8.662 1.76 Lam Noise at 16 × 10

3

 lb; all TL failure at 18 ft; GLF between 7th 

Lams at 12 ft.

aMOR calculations include dead load stress.

bEJ is end joint, GD grain direction, GLF glueline failure, GS slope of grain, and TL tension lamination.

cDid not meet ANSI A190.1 requirements.

(Page 2 
Appendix C

Glulam Beam Failure Maps and Lumber Properties

Location of failures in the tension zone of the beams

is given in the figures. Failure through end joints is

reported by an indication of the percentage of the

failure that occurred at the joint itself. Modulus of

elasticity values are given for each piece of lumber in

the outer tension zone; the locations with reference to

one 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

Beam No. RM4-4

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 maple

end-jointed lumber for grades other than

tension lamination quality using the

lognormal distribution

All

Statistics reported include results for all end-joint

specimens considered and for those specimens with

joint-associated failures.

Lumber size sizes

comGrade and property’ 2 by 4 2 by 6 2 by 8 bined

2.0-1/6

All specimens

Sample size 10 20 5 35

Average TS (lb/in2) 6,950 7,130 6,880 7,020

TS COV (%) 26.6 20.7 59.3 28.9

End-joint failures

Sample size 8 16 5 29

Average SG 0.57 0.57 0.57 0.57

Average MC (%) 8.7 8.9 7.1 8.5

Average TS (lb/in2) 7,030 7,160 6,880 7,050

TS COV (%) 30.0 21.1 59.3 31.0

1/3 EKc

All specimens

Sample size 14 19 21 54

Average TS (lb/in2) 7,060 6,450 6,520 6,630

TS COV(%) 23.3 29.3 25.2 26.1

End-joint failures

Sample size 9 12 13 34

Average SG 0.54 0.52 0.55 0.54

Average MC (%) 8.7 8.5 7.4 8.1

Average TS (lb/in2) 7,040 6,580 6,830 6,790

TS COV (%) 15.2 31.9 20.1 23.6

No. 2

All specimens

Sample size 4 4 3 11

Average TS (lb/in2) 5,720 5,180 4,990 5,270

TS COV (%) 35.1 43.7 3.9 30.9

End-joint failures

Sample size 1 3 1 5

Average SG. 0.64 0.52 0.59 0.56

Average MC (%) 8.7 8.8 8.4 8.7

Average TS (lb/in2) 6,230 5,740 5,160 5,670

TS COV (%) 50.6 — 35.9

aTS is tensile strength, SG specific gravity, and

MC moisture content.

bSpecimens with failures involving an end joint.

cBecause of the percentage of small sample sizes, results

for 2.0-1/3 and 1.8-1/3 grades were combined.

30