Improved Utilization 

of Small-Diameter 

Ponderosa Pine in 

Glued-Laminated Timber

Roland Hernandez

David W. Green

David E. Kretschmann

Steven P. Verrill

United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

Research

Paper

FPL–RP–625
Abstract 

This study involved the evaluation of ponderosa pine glulam

made from lumber that was sawn from a small-diameter 

timber resource. Two different glulam beam depths were 

evaluated: 8 and 13 laminations. A comprehensive glulam

test program was conducted to evaluate edgewise and flatwise bending, shear, and tensile strength. Beam deflection 

was measured and a variety of glulam MOE values were 

determined. The calculated design values for various mechanical properties of this new ponderosa pine glulam beam

combination were compared to the published design values 

of the L3 glulam combination. Using mechanically graded 

lumber in the glulam combination resulted in a structural 

member that efficiently utilized this small-diameter ponderosa pine resource. The calculated design values of this new 

glulam combination are a significant improvement over the 

published design values of the all ponderosa pine L3-grade 

combination that is currently available in the standards. 

Keywords: ponderosa pine, glued-laminated, glulam, 

small-diameter, timber, juvenile wood 

April 2005 

Hernandez, Roland; Green, David W.; Kretschmann, David E.; Verrill, 

Steven P. 2005. Improved utilization of small-diameter ponderosa pine in 

glulam timber. Res. Pap. FPL-RP-625. Madison, WI: U.S. Department of 

Agriculture, Forest Service, Forest Products Laboratory. 38 p.

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Contents 

Page

Executive Summary ............................................................... i

Background........................................................................... 1

Properties of Ponderosa Pine Lumber............................... 1

Ponderosa Pine in Existing Glulam Standards.................. 2

Objectives and Scope............................................................ 3

Experimental Design............................................................. 4

Targeted Ponderosa Pine–Glulam Combination............... 4

Development of Glulam Combination .............................. 4

Material and Methods........................................................... 5

Lumber Grading................................................................ 6

Glulam Beam Manufacture............................................... 7

Properties of Laminating Lumber..................................... 7

Properties of Solid-Sawn and Finger-Jointed Lumber...... 8

Loading Configurations and Data Acquisition ................. 9

Results................................................................................. 12

Edgewise Bending .......................................................... 12

Volume Effect................................................................. 13

Flatwise Bending ............................................................ 14

Edgewise Shear............................................................... 15

Tension............................................................................ 15

Modulus of Elasticity...................................................... 15

Analysis .............................................................................. 16

Glulam Design Values.................................................... 16

ASTM D 3737 Re-Analysis............................................ 17

Conclusions......................................................................... 17

Literature Cited ................................................................... 18

Appendix A—Glulam Beam Maps of Lumber 

MOE Values........................................................................ 19

8-Lamination Beam Maps (Edgewise Specimens) ......... 19

13-Lamination Beam Maps (Edgewise, Flatwise, and 

Shear Specimens)............................................................ 23

Appendix B—Knot Properties of Ponderosa Pine 

Laminating Lumber............................................................. 34

Appendix C—Individual Glulam Beam Test Results......... 36
Executive Summary 

The study reported here involves glued-laminated (glulam)

timber members made entirely from ponderosa pine lumber 

harvested from a small-diameter timber resource. The primary objective was to develop an efficient glulam combination utilizing ponderosa pine for all laminations. Allowable 

properties were calculated from test results for modulus of 

elasticity (MOE), edgewise allowable bending strength (Fbx), 

flatwise allowable bending strength (Fby), allowable tensile 

strength parallel to the grain (Ft), and allowable shear 

strength (Fvx). 

Preliminary analysis of existing ponderosa pine data showed 

that two E-rated grades could be targeted for the outer laminations and a visual No. 2 grade for the core laminations. 

The E-rated grades had an average MOE of 1.4 ×106

 lb/in2

(1.4E). The edge-knot (EK) grades were 1/4- and 1/2-edge 

knot. The glulam combination was designed with 15% 

1.4E–1/4EK lumber in the bottom tension laminations and 

15% 1.4E–1/2EK lumber in the top compression laminations. The remaining 70% was No. 2 grade core laminations. 

This targeted glulam combination could be made entirely

from No. 2 and better grade lumber, an efficient utilization

of the ponderosa pine resource. 

Ponderosa pine lumber was cut from small-diameter trees 

harvested from the Apache–Sitgreaves National Forest in

eastern Arizona. The lumber was initially graded as Standard

and Better, kiln dried, and surfaced on four sides. Initially, 

the 7,972 pieces of lumber were processed through a continuous lumber tester and sorted into four grade classes. The 

lumber was also visually graded to determine if it met laminating stock criteria (wane, warp, and/or skip) and then 

sorted into either 1/4- or 1/2-edge-knot classification. 

Glulam members were manufactured with 8 or 13 laminations for subsequent laboratory testing at the Forest Products

Laboratory. Strength and stiffness were measured for each 

test orientation, and allowable properties were calculated. 

The experimentally determined allowable properties of the 

glulam combination were generally higher than those of the 

all-L3 homogeneous combination currently available in the 

glulam standards. We conclude that mechanical lumber 

grading techniques can be used to obtain an efficient glulam

combination with marketable design properties. 

A comparison of the results obtained for 8- and 13-

lamination glulam members confirmed that the industry

standard volume effect exponent of 0.10 is valid for this

data. 

SI conversion table

Inch–pound unit 

Conversion 

factor SI unit 

inch (in.) 25.4 millimeter (mm) 

foot (ft) 0.3048 meter (m) 

pound force/square inch 

(lb/in2

) 

6.894 kilopascal (kPa) 

pound force/square foot 

(lb/ft2

) 

47.88 pascal (Pa) 
ii 
Improved Utilization of Small-Diameter 

Ponderosa Pine in Glulam Timber 

Roland Hernandez, Research Engineer

David W. Green, Supervisory Research Engineer

David E. Kretschmann, Research Engineer

Steven P. Verrill, Research Statistician

Forest Products Laboratory, Madison, Wisconsin

Background 

The USDA Forest Products Laboratory currently has a research initiative to aid in the management of dense-growth

forests in the western and southwestern United States. Approximately 39 million acres of ponderosa pine forests need 

thinning of small-diameter trees to reduce the fuel load 

created by this dense undergrowth (Forest Products Laboratory 2000). One research objective is to find economical and 

technically feasible value-added uses for the removed material. Value-added applications will help offset forest management costs, provide economic opportunities for rural 

forest-dependent communities, improve forest health, and

reduce the severity of future forest wildfires. Recent research 

on structural applications has involved the development of 

kiln drying procedures to reduce warping and the evaluation 

of grades and characteristics of structural lumber sawn from

small-diameter wood. The project reported here was initiated 

to evaluate the technical feasibility of utilizing ponderosa 

pine (Pinus ponderosa) in structural glued-laminated lumber 

(glulam). 

To best utilize small-diameter ponderosa pine in glulam, 

information is needed on the mechanical properties of solidsawn lumber processed from this resource. This information

will be vital in developing a new glulam combination that 

could potentially be included in existing glulam standards. 

Properties of Ponderosa Pine Lumber 

The properties and yield of lumber cut from small-diameter 

ponderosa pine trees are a function of the diameter and age 

of the trees and the conditions under which the trees are 

grown. The primary grade-determining factor for this lumber, other than knots, is drying degrade, which is caused by

warp (Simpson and Green 2001). A major cause of warp in

ponderosa pine lumber is juvenile wood, which can constitute approximately the first 20 to 25 years of tree growth

(Voorhies and Gorman 1982). Ponderosa pine is only moderately tolerant of shade; it grows rapidly until the upper 

canopy closes. Because of this growth characteristic, a considerable portion of a ponderosa pine log consists of juvenile

wood. The presence of juvenile wood creates a challenge for 

utilization.

Juvenile wood can be thought of as the “core” wood, the 

material closest to the pith (Fig. 1). Trees produce juvenile 

wood in the early growth period. The characteristics of the 

wood change markedly in each successive annual growth 

ring. During a transition period from approximately 5 to

20 years of age, wood characteristics gradually improve until 

they become relatively constant. This latter material is 

known as mature wood. In conifers, juvenile wood has lower 

strength, lower specific gravity, thinner cell walls, lower 

cellulose content, and a lower percentage of latewood compared with that of mature wood. Juvenile wood also has 

higher longitudinal shrinkage, more compression wood, a 

greater fibril angle, and higher lignin content.

Because ponderosa pine is shade intolerant (Burns and 

Hinkala 1990), one would not expect to find much difference in the volume of juvenile wood in trees growing in

suppressed stands than in trees grown in plantations (other 

growth factors being equal). Recent studies support this 

assumption. 

Small-diameter ponderosa pine from an approximately 

35-year-old stand near Emmett, Idaho, yielded virtually no 

lumber that would grade as Select Structural (Table 1); about

13% of the wood was graded as No. 2 and better (Gorman 

and Green 2000). The logs for this study were obtained by

thinning from below, which removed the poorer quality 

trees. Material thinned from a 45-year-old second-growth

stand near Grangeville, Idaho, gave a 47% yield of No. 2

and better lumber, but less than 1% Select Structural (Erickson and others 2000). Even lumber sawn from suppressed 

trees (diameter ≤ 16 in.) from a 90- to 100-year-old stand in

Flagstaff, Arizona, produced less than 3% yield of Select

Structural grade lumber (Lowell and Green 2000). 

The Emmett study also yielded information on mechanical 

properties (Gorman and Green 2000), which allowed us to

compare the performance of lumber from that smalldiameter resource to ponderosa pine lumber evaluated in the 

1987 In-Grade Testing Program (Green and Evans 1987). 
Figure 1—Effect of juvenile wood on physical and mechanical properties. 

Table 1—Grade yield of ponderosa pine from smalldiameter trees 

Yield (%)

Gradea Emmett, ID 

(plantation) 

Grangeville, ID 

(plantation) 

Flagstaff, AZ 

(suppressed) 

SS 0 0.2 2.4

No. 1 1.6 14.0 4.9 

No. 2 11.4 33.2 26.7 

No. 3 31.9 3.2 32.3 

Economy 55.1 49.4 33.7

a SS is Select Structural. 

The lumber tested in the In-Grade Testing Program was 

gathered from larger-diameter resources and likely did not

contain as large a percentage of juvenile wood. Table 2 

summarizes modulus of elasticity (MOE) data for both the 

Emmett study and the In-Grade Testing Program. Although 

only the No. 2 grade 2 by 4 lumber could be compared 

directly, the data suggest that MOE properties are slightly

lower (approximately 10% at the mean) for ponderosa pine 

lumber processed from small-diameter trees. (Note: 2 by 4 

refers to lumber with nominal dimensions of 2 by 4 in.) 

In Table 3, a similar comparison was made for modulus of 

rupture (MOR) of No. 2 grade ponderosa pine lumber. 

Once again, only the No. 2 grade lumber could be compared 

directly; the difference in strength was much more dramatic

than the slight difference found for MOE. The MOR of the 

lumber from the In-Grade Testing Program was approximately 36% higher (mean) than the lumber from the Emmett 

study. This significant difference was likely due to the visually observed higher occurrence of juvenile wood in the 

Emmett lumber. 

Thus, based on these past studies, lumber processed from

small-diameter thinnings could be expected to possess significantly lower strength properties and slightly lower stiffness properties than lumber processed from larger-diameter 

trees harvested under normal logging conditions. Mechanical 

grading will add value to the graded lumber and improve

yields, because visual grading of this resource can result in 

non-conservative design values. These facts strongly suggest

that mechanical grading techniques should be considered 

when developing structural wood products from smalldiameter ponderosa pine lumber. 

Ponderosa Pine in Existing 

Glulam Standards

In existing glulam standards (AITC 2004), the two most

common species groups of lumber used as laminating stock 

are Douglas Fir and Southern Pine. Ponderosa pine lumber is

referenced in this glulam standard as part of a species group 

called Softwood Species. Laminating lumber belonging to

2 
Table 2—Modulus of elasticity properties of ponderosa pine 2 by 4 lumber

a

Emmett, ID data In-Grade data 

MOEedge 

(106 lb/in2) 

MOEtv

(106 lb/in2) 

MOEedge

(106 lb/in2) 

Grade

MC 

(%) SG Mean SD Mean SD Mean SD

SS — — — — — — 1.129 0.19

No. 1 11.1 0.36 0.959 0.20 0.927 0.20 — —

No. 2 10.9 0.35 0.877 0.19 0.855 0.18 0.976 0.18

No. 3 11.4 0.35 0.854 0.22 0.820 0.21 — —

a

MC is moisture content, SG is specific gravity (ovendry weight and volume 

 at test MC), SD standard deviation.

Table 3—Modulus of rupture properties of ponderosa

pine 2 by 4 lumber

MOR (lb/in2

) 

Emmett, ID data In-Grade data 

Grade Mean SD

5th 

percentile Mean SD

5th 

percentile 

SS — — — 7,510 1,700 4,320

No. 1 4,450 1,370 2,700 — — — 

No. 2 3,880 1,410 2,050 5,290 2,100 2,650

No. 3 3,430 1,260 — — — — 

the Softwood Species group has relatively lower physical

and mechanical properties than Douglas Fir and Southern 

Pine. For this reason, Softwood Species are only allowed in

homogeneous glulam combinations made from E-rated 

laminations ranging from an average MOE of 1.6 to 2.1 

×106

 lb/in2, as well as in homogeneous L3 visual combinations. Prior to the 2004 version of the AITC 117 glulam

standard, Softwood Species were allowed in the core laminations of glulam beams made with Douglas Fir in the outer 

laminations. However, these types of glulam combinations 

were considered over-stressed in the outer laminations because of the low-grade core laminations, and thus they were 

removed from the standard. 

Because of the relatively low mechanical properties of 

ponderosa pine, this species is practically disqualified as a 

viable source of E-rated laminating stock in the 1.6E to 2.1E 

range. As Table 2 indicates, ponderosa pine cannot achieve 

these MOE levels. In addition, the National Design Specifications (NDS 1997) publishes a design MOE value of only

1.2 ×106

 lb/in2 for the Select Structural grade for Softwood 

Species. 

This means that the only current glulam combination that

can be made with 100% ponderosa pine is the homogeneous 

L3 visual grade combination. 

The design values for the homogeneous L3 grade ponderosa 

pine glulam combination (Softwood Species) are as follows:

Modulus of elasticity, MOE 1.0 ×106 lb/in2

Edgewise allowable bending strength 

(horizontally laminated), Fbx 

725 lb/in2

Flatwise allowable bending strength 

(vertically laminated), Fby 

800 lb/in2

Allowable tensile strength, Ft 525 lb/in2

Allowable shear strength, Fvx 195 lb/in2

Objectives and Scope 

The objectives of this study were to develop an efficient

glulam combination, with all laminations utilizing ponderosa 

pine lumber, and to evaluate test beams experimentally for 

MOE, Fbx, Fby, Ft, and Fvx. A single glulam combination was 

targeted: 15% high-stiffness laminations were used for the 

top and bottom layers; the remaining core laminations were 

equivalent to a No. 2 visual grade. Two beam depths were 

targeted for testing: 8 and 13 laminations. The 8-lamination 

beam was targeted for the Fbx and Ft tests and the 13-

lamination beam for the Fbx, Fby, and Fvx tests. A total of 15

beams were targeted for each mechanical property group, for 

a total of 75 strength tests. MOE was calculated in each test, 

based on measured loads and deflections. The mechanical 

property test data provided in this report will serve as the 

basis for inclusion of a new all ponderosa pine glulam 

combination into existing glulam standards. 

3
Experimental Design 

Targeted Ponderosa Pine–Glulam 

Combination 

Because past research shows low yields of Select Structural 

grade ponderosa pine lumber, we targeted the utilization of 

laminating grades that do not require stringent edge-knot

criteria. This would permit ponderosa pine to be harvested 

from most areas of the country, including small-diameter 

resources. 

Typically, outer laminations of E-rated glulam combinations 

are designed with 1/6 edge-knot (1/6EK) restrictions (AITC

2004). However, because of the low yields that would be 

expected with this grade of lumber, we designed the test

beams to require only a 1/4 edge-knot (1/4EK) restriction in

the outer tension zone and a 1/2 edge-knot (1/2EK) restriction in the outer lamination grades in the compression zone. 

For the core laminations, a No. 2 visual grade was targeted. 

This design allowed for the entire glulam combination to be

manufactured with No. 2 and better grade lumber. 

For laminating lumber, we evaluated the possibilities of

targeting MOE levels of as high as 1.6 × 106

 lb/in2 for the 

outer laminations. However, based on the results shown in

Table 2, we determined that a 1.4E lumber grade would be 

the highest MOE level that could be achieved with reasonable yields. 

Based on these resource limitations, the resulting glulam

combination would have E-rated grades of 1.4E–1/4EK in

the outer tension zone, 1.4E–1/2EK in the outer compression 

zone, and No. 2 visual grade lumber in the core laminations. 

Furthermore, the 1.4E lumber grades occupied only the top 

and bottom 15% of the laminations in the general glulam

combination.

With the general glulam combination established, an 

analysis was conducted using the industry standard ASTM D 

3737 (ASTM 2000a). This involved estimating the 

properties of the targeted lumber grades (Table 4). These 

estimated properties were based on field data that had been 

gathered by quality control inspectors of the American Institute of Timber Construction (AITC), as well as past information for other species of E-rated lumber having similar 

edge-knot criteria. The properties included MOE, knot size 

characteristics, minimum bending strength ratios, and bending stress indices. 

Development of Glulam Combination 

Based on the lumber properties in Table 4, an analysis was 

conducted using ASTM D 3737 (ASTM 2000a) procedures 

to determine a technically feasible glulam combination made

from all ponderosa pine laminations. Two beam depths were 

targeted, both to be manufactured with 2 by 4 lumber. The 

two combinations shown in Figure 2 were developed on the 

basis of this analysis. 

The bottom tension zone consisted of 15% 1.4E–1/4EK 

grade, the top compression zone of 15% 1.4–1/2EK grade, 

and the remaining portion of No. 2 grade lumber. The 12-in.-

deep 8-lamination beam shown in Figure 2a represents a 

potentially common size of beam that could be used in structural applications such as headers for garage doors and large 

windows. The 13-lamination beam represents the critical 

combination for the 15% outer zones. A 13-lamination beam

requires 1.95 laminations of depth for the 15% zone, and this

combination just meets that requirement. The 8-lamination 

beam, on the other hand, requires 1.2 laminations of depth 

for the 15% outer zones, and the two laminations exceed this 

requirement. The 8-lamination glulam combination results in

25% outer zones and would be expected to have slightly

higher strength and stiffness than the 13-lamination beam. 

An ASTM D 3737 analysis of this glulam combination 

utilizing 1.4E lumber in 15% of the outer zones resulted in a 

design glulam MOE value of 1.2 ×106

 lb/in2. This design 

value was governed by the analytical results of the critical 

13-lamination beam. The calculated design bending strength, 

which was also governed by the 13-lamination beam, was 

Table 4—Estimated properties of ponderosa pine laminating grades for ASTM D 3737 analysis

Grade

MOE 

(× 106

 lb/in2) 

Mean knot

sizea

 

(%)

99.5% knot 

sizeb

 

(%) 

Minimum bending 

strength ratio 

Bending stress 

index 

(lb/in2

) 

Provided by AITC

1.6E–1/4EK 1.6 10.3 48.9 0.65 2,560

1.4E–1/4EK 1.4 10.6 51.8 0.65 2,100

1.2E–1/4EK 1.2 11.4 60.0 0.65 1,650

No. 2 1.0 11.5 56.8 0.45 1,800 

Developed by FPL 

1.4E–1/2EK 1.4 12.0 60.0 0.50 2,100

a

Average of sum of all knot sizes within each 1-ft length, taken at 0.1-ft intervals (ASTM 2000a). b

99.5 percentile knot size (ASTM 2000a). 

4 
Figure 3—Standard and Better grade ponderosa pine 

lumber. Approximately 36% of pieces have pithassociated wood. 

Figure 4—Continuous lumber tester used to test 

lumber for MOE. Panels removed to show rollers. 

Figure 2—Ponderosa pine glulam combinations: 

(a) 8-lamination and (b) 13-lamination. 

1,250 lb/in2

. This value is based on the 302–20 grade (AITC

2004) of tension lamination used in the bottom lamination. 

When a tension lamination is not used, as targeted in this 

study, the design bending strength is 1,050 lb/in2

 for beams 

≤15 in. deep and 950 lb/in2

 for beams >15 in. deep. These 

are standard 15% and 25% reductions, respectively, for the 

two ranges of beam depth. 

Material and Methods 

This section describes the procedures taken to characterize 

the properties of the laminating lumber as well as the fabrication of the experimental glulam beams. 

The ponderosa pine lumber was harvested from the Apache–

Sitgreaves National Forest of eastern Arizona. The lumber 

was Standard and Better grade kiln-dried and surfaced on 

four sides (WWPA 2000). Unique to this lumber set is that

the majority was processed from small-diameter timber. As a 

result, a significant number of pieces had pith-associated 

wood, or juvenile wood, in the cross section. 

Figure 3 shows a typical bundle of Standard and Better 

grade lumber prior to mechanical grading and sorting; pieces 

that contained juvenile wood in the cross section are apparent. More than 36% of this lumber contained juvenile wood. 

Because juvenile wood is defined as approximately the first 

20 to 25 years of growth, the amount of lumber having a 

large percentage of juvenile wood would actually be larger 

than 36%. We also observed considerable warp in this lumber as well as a significant release of stress when the lumber 

straps were cut from the bundles. 

The 7,972 pieces of lumber individually marked with a 

unique identification number and then processed through a 

continuous lumber tester (CLT) (Metriguard, Inc., Pullman, 

Washington) (Fig. 4). Lumber was processed through the 

CLT through a series of rollers at approximately 200 ft/min. 

The rollers are spaced so as to create two continuous 48-in. 

spans. A fixed displacement is applied at the center of each 

span (an upward displacement and a downward displacement). The resultant loads in each span are measured at 1-in. 

increments, which provides the information necessary for 

determining MOE. This information, which is stored in a 

computer text file, includes the average of all MOE values 

along the length of the member, the low-point MOE value, 

and the location of the low-point MOE value. 

The CLT software was set so that different color sprays were 

used for different ranges of lumber MOE (Table 5). The 

ranges targeted an average MOE level that matched those 

values targeted for the experimental beam combination 

5
Table 5—CLT software settings for sorting

various MOE groups

Group 

number 

Minimum 

MOE 

(106

 lb/in2) 

Maximum 

MOE 

(106

 lb/in2) 

Spray

color 

1 1.70 >1.70 Orange

2 1.10 1.69 Green

3 0.80 1.09 Purple

4 <0.80 0.79 None

Figure 5—Grading of lumber: (top) visual grading of 

lumber after exiting CLT machine; (bottom) bundles 

of lumber sorted by MOE and visual lumber grade. 

Table 6—CLT MOE results for ponderosa pine lumber

a

MOE test resultsc Low point 

to avg MOE 

Groupb Sample 

size 

Average 

(106 lb/in2) 

COV 

(%) Ratio

COV 

(%) 

All 7,972 1.166 28.5 0.713 21.3

1 556 1.850 6.6 0.821 11.3

2 3,403 1.356 12.0 0.774 11.5

3 1,335 0.997 8.0 0.789 8.2

4 2,678 0.867 23.4 0.577 27.9

a

Standard and Better grade. 

b

Group numbers correspond to those defined in Table 2. c

COV is coefficient of variation. 

(Fig. 2), along with a low-MOE grade (average 

1.0 × 106

 lb/in2). 

Specimens in groups 1 and 4 (Table 5) were removed to

avoid any unusually high or low MOE values in the targeted 

mechanical grades. Group 2 specimens were targeted for 

1.4E lumber and group 3 specimens for 1.0E lumber (for use 

in a future study to establish a low-MOE E-rated lumber 

grade). Information from the CLT, which was stored in an 

ASCII text file, included lumber length, average MOE, lowpoint MOE, location of low-point MOE, and corresponding 

group number. The calculated MOE values were based on 

the 1.5- by 3.5-in. cross-sectional dimensions of the lumber. 

Immediately after testing, each piece of lumber was visually 

graded to determine if it met laminating stock criteria (wane, 

skip, and/or warp) and for sorting into the targeted 1/4- or 

1/2-edge knot grades (Fig. 5). Once all the lumber needed 

for the outer lamination grades was gathered, pieces for the 

core laminations were gathered from the unsorted Standard 

and Better grade lumber. The Standard and Better grade 

lumber was processed through the CLT machine to record 

information on MOE. The material was visually graded to

ensure that it met No. 2 grade requirements and laminating 

requirements (wane, skip, and/or warp). 

Finally, a static deflection test was conducted to determine 

MOE. The test measured deflection caused by a 10-lb weight

on the full span of specimens in the flatwise orientation. A 

significant number of these specimens were targeted in each 

sorted lumber group to develop a relationship between CLT 

MOE and static MOE throughout the full range of MOE 

values. It was necessary to develop this relationship because 

it verified the proper calibration of the CLT machine and 

provided static MOE values as specified in ASTM D 3737 

(ASTM 2000a).

Lumber Grading 

Table 6 shows the CLT MOE results of all 7,972 pieces of 

lumber processed through the CLT machine. This total also 

includes lumber that did not meet laminating grade visual

criteria, such as wane, skip, and/or warp. As Table 6 shows, 

3,403 pieces of group 2 (42.7%) met the targeted 1.4E grade 

and 1,335 pieces of group 3 (16.7%) the targeted 1.0E grade. 

The total number of pieces meeting these two MOE levels 

was 59.4%. In normal production, group 1 specimens would 

also be included in beam manufacture, which would result in

approximately 66.4% of pieces meeting or exceeding the 

targeted MOE levels of 1.0E and 1.4E. 

Approximately 1,090 pieces were used in beam manufacture, 

181 pieces were processed into finger-jointed lumber specimens for testing, and 973 pieces remained as solid-sawn 

6 
lumber for testing. Of the total of 7,972 pieces, 2,244 pieces 

met laminating stock criteria, which is approximately 28.1% 

yield. Wane and skip were the primary controlling factors 

for the high rate of rejection of lumber for laminating stock 

from this Standard and Better grade lumber. If this lumber 

had been processed at the sawmill to a slightly thicker green

dimension so that the final dressed size would have had 

fewer pieces with wane and skip, our yield of laminating 

stock would have been much higher than 28.1%. Another 

option that would have solved this problem would have been 

to re-plane the lumber during glulam manufacture. 

The mechanical properties of the lumber are the most important aspect of this grading process. We determined that 66% 

of the Standard and Better grade resource possessed the 

properties suitable for glulam manufacture. This yield was 

not fully realized because of the large quantity of lumber 

rejected because of wane and skip. 

Finally, to verify the validity of the CLT results, a total of

221 lumber specimens were tested for flatwise static MOE. 

These specimens were sampled throughout a wide range of 

MOE values to develop a regression relationship between 

CLT MOE and static MOE (Fig. 6). The regression relationship shown in Figure 6 had a very high coefficient of determination (r2

) of 0.983. Because the difference in magnitude 

of the two MOE values was very small (within 3.6% at 1.0E 

and within 1.5% at 1.4E), no adjustments to the CLT MOE 

values were made in subsequent analyses. The small differences between CLT MOE and long-span static MOE were 

not large enough to affect the ASTM D 245 (ASTM 2000c) 

rounding rules for lumber MOE. 

Glulam Beam Manufacture 

The initial step of glulam manufacture involved fingerjointing the lumber end-to-end. The standard (1.113-in.-

long) finger-joint profile was used. The order of manufacture 

was first finger jointing of the 1.4E–1/2EK grade laminations, then the core laminations, and finally the 1.4E–1/4EK 

grade laminations. These laminations were dry-stacked with

the compression laminations on the bottom (1.4E–1/2EK) 

and tension laminations on the top (1.4E–1/4EK) (Fig. 7). 

The 8-lamination beams were processed as 48-ft-long members and the 13-lamination beams as 64-ft-long members. 

The lumber ID number and the location of the finger joints

were recorded during dry-stacking of the full-length laminations. This mapping procedure allowed the recording of 

lumber placement in the experimental glulam beams, which 

will provide valuable data for future analyses. Appendix A 

contains the actual beam maps for all the glulam beams 

tested in this study, along with the MOE properties of the 

lumber. 

Figure 6—Regression relationship between static MOE 

and CLT MOE of ponderosa pine laminating lumber. 

Figure 7—Dry stacking of finger-jointed laminating

lumber. Note lumber, lamination, and beam identification 

numbers. 

Properties of Laminating Lumber 

The MOE properties were obtained from the lumber that was 

actually mapped within the beams. Knot properties for conducting an ASTM D 3737 analysis were determined from

measurements taken on graded lumber that was sampled for 

laboratory testing. These lumber grades were sampled during 

glulam beam manufacture and were representative of the 

lumber used in the beams. A summary of the knot analysis is

included in Appendix B. Moisture contents were measured 

at the laminating plant throughout the duration of the 

manufacturing process. The lumber was determined to have 

an average moisture content of 8.8%, with a range of 7% to

12%. Table 7 shows the results of MOE for the lumber 

mapped within the beams and for the lumber sampled for 

laboratory testing. Results on knot properties were based on 

the lumber sampled for laboratory testing.

7
Table 7—Summary of actual lumber MOE and knot propertiesa

Lumber MOE Knot propertiesb

Grade 

Sample 

size 

Average 

(×106 lb/in2) 

COV 

(%) 

Lineal footage 

(ft) 

x-bar 

(%) 

h 

(%) 

Lumber mapped in glulam beams 

1.4E–1/4EK 344 1.343 11.5 — — —

1.4E–1/2EK 340 1.309 12.7 — — —

Core 999 1.109 27.6 — — —

Lumber sampled for laboratory tests 

1.4E–1/4EK 121 1.232 14.7 525 11.0 42.7

1.4E–1/2EK 144 1.209 17.0 534 15.9 47.4

1.0E–1/4EK 108 0.984 8.2 508 11.2 40.0

1.0E–1/2EK 364 0.994 10.3 1,020 13.3 50.0

All 1/4EK grade — — — 1,033 11.1 41.3 

All 1/2EK grade — — — 1,554 14.2 48.7 

a

To adjust lumber MOE values to 100:1 span-to-depth static MOE value, use the following relationship: 

 y = 1.0367x – 0.0728. b

x-bar is mean knot size; h is difference between 99.5th percentile knot size and mean knot size 

 (ASTM 2000a).

The resulting average MOE values of the lumber actually 

mapped in the beams shows that the targeted MOE level of

1.4 ×106

 lb/in2 was not achieved for the two grades of 1.4E 

lumber. The 1.4E lumber mapped in the glulam beams only

achieved a 1.3E level, and the lumber sampled for laboratory

testing only achieved a 1.2E level. As for the 1.0E grade, we 

found that the targeted MOE levels were exactly met, with

resulting average MOE values of 0.98 ×106

 lb/in2 and 

0.99× 106

 lb/in2 for the 1.0E–1/4EK and 1.0E–1/2EK grades, 

respectively. 

Properties of Solid-Sawn and 

Finger-Jointed Lumber 

To relate lumber properties to glulam properties, the mechanical properties of matched samples of laminating lumber 

for each grade used in the glulam combinations were evaluated. The predominantly 12-ft-long lumber was sorted into

two primary groups matched by lumber MOE: specimens to

be tested in tension and those to be tested in edgewise bending. After processing an approximately 7-ft-long specimen 

from each 12-ft piece of lumber, additional test specimens 

were cut from the remaining 5-ft-long piece of lumber. 

These additional specimens included an approximately 3-ftlong specimen for flatwise bending and a short specimen for 

the standard notched shear block test. With this cutting 

scheme, we obtained matched samples of tensile strength 

and edgewise bending properties, and all specimens had 

lumber MOE, flatwise bending, and shear strength properties. The presence of strength-reducing defects in the tension 

and bending specimens was allowed to occur randomly. 

As Table 7 indicates, average MOE values of the lumber 

sampled for laboratory testing did not accurately match 

average MOE values of the lumber mapped in the glulam

members. Consequently, we sorted the laboratory-tested 

lumber so that its average MOE properties matched those 

reported for the glulam beams and are reported in Table 8. 

These sorted MOE properties closely approximated the 

mapped beam MOE properties. The corresponding strength 

properties for those matched lumber groups were characterized and reported in Table 9. This method of sorting assured 

that the distributions of lumber properties characterized in 

Tables 8 and 9 were representative of the lumber grades 

mapped in the glulam members (Table 7). This characterization will be critical in future research involving glulam

modeling. 

In addition to tests on solid-sawn lumber, finger-jointed 

lumber specimens were tested in tension. This test was conducted to evaluate the ANSI A190.1 requirement that the 5th

percentile tensile strength of the bottom lamination in fingerjoint grade must achieve a level 1.67 times the design bending strength of a glulam beam. Figure 8 shows the distribution of tensile strength of 1.4E–1/4EK grade finger-jointed 

lumber specimens. As is common with lower strength lumber, a significant number of failures were observed to occur 

away from the finger joint, usually in a strength-reducing 

defect such as a knot. Only 18 of 41 specimens in the 1.4E 

grade failed at the finger joint. 

The lowest ranking tensile strength of a specimen with a 

finger-joint failure was 1,690 lb/in2

, which would serve as 

8 
Table 8—Best-fitting distributions of flatwise lumber MOE for each glulam beam groupa

Distribution parameterb

Beam 

group 

Lumber 

grade 

Best-fit 

distribution 

Sample 

size Location Scale Shape

Mean 

(×106

lb/in2

) 

COV 

(%) 

5th percentile 

(×106

lb/in2

) 

8-Lam Fbx 1.4–1/4 3-P Lognormal 88 0.7289 –0.5096 0.2742 1.3526 27.9 1.0991

 1.4–1/2 3-P Weibull 75 0.4231 0.8783 2.3092 1.2326 14.2 0.9264

Core 2-P Lognormal 167 0.0000 –0.0319 0.2767 1.0064 28.2 0.6002

8-Lam Fbt 1.4–1/4 3-P Weibull 46 1.0967 0.2471 1.2732 1.3180 10.6 1.1363

 1.4–1/2 2-P Lognormal 61 0.0000 0.2241 0.1277 1.2614 12.8 0.9949

Core 2-P Lognormal 101 0.0000 –0.0418 0.2436 0.9879 24.7 0.6250

8-Lam all 1.4–1/4 3-P Lognormal 134 0.7492 –0.5614 0.2716 1.3411 27.7 1.1047

 1.4–1/2 3-P Weibull 136 0.2893 1.0312 2.5081 1.2485 14.3 0.9324

Core 2-P Lognormal 268 0.0000 –0.0357 0.2647 0.9994 26.9 0.6135

13-Lam Fbx 1.4–1/4 2-P Lognormal 112 0.0000 0.2884 0.1223 1.3443 12.3 1.0769

 1.4–1/2 3-P Weibull 97 1.0999 0.2573 1.3489 1.3286 9.8 1.1502

Core 3-P Weibull 471 0.5099 0.6976 1.4336 1.1279 27.9 0.6744

13-Lam Fby 1.4–1/4 2-P Lognormal 41 0.0000 0.2977 0.1054 1.3543 10.6 1.1101

 1.4–1/2 3-P Lognormal 48 1.0933 –1.4967 0.7457 1.3890 86.2 1.1510

Core 2-P Lognormal 204 0.0000 0.1042 0.2764 1.1531 28.2 0.6894

13-Lam Fvx 1.4–1/4 3-P Lognormal 57 0.8778 –0.8382 0.3804 1.3427 39.5 1.0956

 1.4–1/2 3-P Weibull 59 1.0964 0.2900 1.3333 1.3545 11.1 1.1510

Core 3-P Weibull 247 0.2763 1.0094 1.7748 1.1797 26.6 0.6694

13-Lam all 1.4–1/4 2-P Lognormal 210 0.0000 0.2893 0.1167 1.3446 11.7 1.0925

 1.4–1/2 3-P Weibull 204 1.0985 0.2768 1.3406 1.3446 10.5 1.1515

Core 3-P Weibull 922 0.3910 0.8534 1.6277 1.1495 26.8 0.6692

1.4–1/4 2-P Lognormal 344 0.0000 0.2880 0.1148 1.3426 11.5 1.1445

 All 1.4–1/2 2-P Lognormal 340 0.0000 0.2614 0.1269 1.3092 12.7 1.0965

Core 3-P Weibull 1,190 0.3595 0.8429 1.6217 1.1085 27.6 0.6319

a

To adjust lumber MOE values to 100:1 span-to-depth static MOE value, use the following relationship: 

y = 1.0367x – 0.0728. b

For lognormal, scale = average of LN(x) and shape = standard deviation of LN(x). 

the non-parametric 5th percentile. The 50th percentile value, 

with all failures included, was 3,266 lb/in2

. If the ANSI 

A190.1 qualification stress level factor of 1.67 were applied 

to the non-parametric 5th percentile value, the corresponding 

glulam design bending strength for which these finger joints

would qualify would be 1,012 lb/in2

. Figure 9 shows the 

cumulative distribution of tensile strength for the 1.0E grade 

finger-jointed lumber specimens. The 50th percentile value, 

with all failures included, was 2,507 lb/in2

, and the lowest 

ranking finger-joint tensile strength was 1,313 lb/in2

. These 

1.0E finger-jointed lumber specimens were representative of 

the finger joints that occur in the core laminations of the 

glulam test specimens. 

Loading Configurations and 

Data Acquisition 

Four types of glulam tests were conducted: edgewise bending, flatwise bending, beam shear, and beam tension. Figures 

10 and 11 show a 13-lamination beam during edgewise and 

flatwise bending, respectively. Figures 12 and 13 show a 

13-lamination glulam beam during shear and tension tests, 

respectively. Table 10 provides information on test spans 

and data acquisition. The targeted time-to-failure for all 

glulam beam and lumber tests was 10 min, with all failures 

occurring between 5 and 20 min as specified in ASTM

standard D 198 (ASTM 2000b). 

9
Table 9—Best-fitting distributions of solid-sawn lumber strength for each glulam beam group 

Distribution parametera

Lumber 

grade 

Best-fit 

distribution 

Sample 

size Location Scale Shape

Mean 

(lb/in2

) 

COV 

(%) 

5th 

percentile 

(lb/in2

) 

Flatwise lumber modulus of rupture 

1.4–1/4 3-P Weibull 25 2815.7 5578.6 3.6182 7843.9 19.7 5270.4

1.4–1/2 2-P Lognormal 67 0.0000 8.8967 0.2275 7499.4 23.0 4869.2 

Core 2-P Lognormal 51 0.0000 8.7837 0.2764 6781.0 28.2 3956.5 

Lumber ultimate tensile strength 

1.4–1/4 2-P Lognormal 12 0.0000 8.2324 0.2630 3893.3 26.8 2194.7 

 1.4–1/2 2-P Lognormal 46 0.0000 8.0718 0.3191 3370.2 32.7 1790.8 

Core 2-P Lognormal 43 0.0000 7.9258 0.2830 2880.9 28.9 1649.1 

Edgewise lumber modulus of rupture 

1.4–1/4 2-P Lognormal 24 0.0000 8.7837 0.3557 6953.2 36.7 3319.0 

 1.4–1/2 2-P Lognormal 34 0.0000 8.5546 0.2503 5356.0 25.4 3267.0 

Core 2-P Lognormal 26 0.0000 8.4040 0.2450 4600.7 24.9 2807.3 

ASTM shear block strength 

1.4–1/4 2-P Lognormal 23 0.0000 6.8459 0.1389 949.09 14.0 721.10 

1.4–1/2 2-P Lognormal 67 0.0000 6.8556 0.1099 954.95 11.0 780.13 

Core 3-P Weibull 47 654.70 248.05 2.0519 874.45 12.8 713.03 

a

For lognormal, scale is average of LN(x) and shape is standard deviation of LN(x). 

Edgewise Bending Tests 

Edgewise bending tests (Fig. 10) were conducted on both the 

8- and 13-lamination glulam combinations. Sixteen beams of 

each configuration were tested (15 test beams plus 1 beam

with high MOE outer laminations). The glulam beams were 

supported on rocker-type platforms that pivoted as the beams 

deflected as a result of loading; this type of support allows 

minor translation during loading. Lateral roller supports

were used at intervals along the beam length to prevent

lateral torsional buckling. Force was applied with a loading

beam having two attached loading points that were also 

capable of pivoting as the beam increased in curvature. The 

support span was set at a 21:1 span-to-depth ratio, according 

to ASTM D 198 (ASTM 2000b). To reduce the possibility of 

local crushing, thick maple blocks were used between the 

load points and the beam surface to increase the area of 

contact. The distance between the load points was 20% of 

the support span. The trapezoidal moment diagram created 

with this loading configuration approximated the parabolic

moment diagram created by a uniform load configuration. 

Load was measured using a 250,000-lb capacity load cell

above the loading beam. Long-span center-point deflection 

was measured using a linear variable displacement 

transducer (LVDT) attached to a piano wire strung tightly at

the neutral axis between the two supports. The LVDT had a 

6-in. maximum gauge length, and the resolution was 

0.005 in. Shear-free deflection was measured across a 

shorter span between the two load points. A tripod-type yoke 

was used to hold the LVDT in place during measurement of 

deflection caused by increasing the curvature of the top 

surface of the beam. The LVDT had a 1-in. maximum gauge 

length, and the resolution was 0.001 in. 

Flatwise Bending Tests 

Flatwise bending tests (Fig. 11) were conducted on only the 

13-lamination beams. This setup required wider rocker 

supports and loading point blocks than the edgewise tests so 

that a line load could be applied across the entire width of 

the beam. Long-span deflection was measured with respect

to the load head, and no shear-free deflection measurements 

were taken. Support span was also set to a 21:1 span-todepth ratio; however, in this case, the depth was the beam

width. Distance between the load points was also set to 20% 

of the support span. 

10 
Figure 11—Testing of 13-lamination glulam beam: 

(top) flatwise bending test; (bottom) LVDT placement for 

measuring center-span deflection.

Figure 8—Cumulative distribution of tensile strength of 

1.4E grade finger-jointed lumber specimens. 

Figure 9—Cumulative distribution of tensile strength of 

1.0E grade finger-jointed lumber specimens. 

Figure 10—Edgewise bending test of 13-lamination 

glulam beam. 

Edgewise Shear Tests 

Only the 13-lamination glulam beams were tested for shear 

strength (Fig. 12) using a bending test setup with a shorter 

span than that used for the other tests. The loading configuration used a span-to-depth ratio of 6:0 with a symmetric

two-point loading configuration, as recommended by Yeh 

(1997). Two loading points were used so that localized 

crushing would not occur under a single load-point; however, the loading points were spaced close together so that 

the test setup would closely simulate a center-point-loaded 

configuration. Although not necessary for development of 

design values, we measured the full-span deflection of these 

beams with respect to the neutral axis. These data, along 

with long-span and shear-free deflections measured on other 

beams, will provide useful information on the effect of shear 

deformation when modeling glulam MOE using lumber 

MOE values. 

Tension Tests 

Unique to this study was the utilization of a large-capacity 

tension machine (Fig. 13), with a 200,000-lb load cell, to 

11
Figure 13—Testing of 8-lamination glulam beam: 

(top) tension test; (bottom) close-up of tension grips.

Figure 12—Glulam beam shear tests: (top) end view of 

support block, stringline for measuring deflection, and 

lateral supports; (bottom) close-up of load points and 

radiused contact blocks. 

evaluate the 8-lamination glulam members in tension. A 

1-in.-long gauge LVDT with 0.001-in. resolution and an 

aluminum rod were pinned to the side of the member to

measure axial displacement over a 96-in. gauge length. The 

distance between the tension grips was 152 in. Hydraulic

pressure to the tension grips was increased as the tensile load

increased, so that no slipping would occur during the test. 

The tension grips had a pinned connection at each end to 

ensure that no bending moment was exerted on the members. 

Results 

Inspection of the test beams revealed that one beam designated for edgewise bending had a very large center knot in

the bottom lamination near a finger joint. The ANSI A190.1 

standard (ANSI/AITC 2004) states that knots of this size 

cannot occur within two knot-diameters from a finger joint

located in the maximum moment regions of a glulam beam. 

For this reason, this beam was excluded from the test group 

and from all analyses. Table 11 summarizes the results of the 

glulam strength and stiffness tests. Details of glulam beam

tests are provided in Appendix C.

Edgewise Bending 

All glulam beam failures exhibited linear load–deflection 

behavior up to the ultimate load, with failure primarily due

to knots and pith-associated wood in the outer two tension 

laminations. The results in Table 11 show that the average 

12 
Table 10—Summary of loading configurations used in 

glulam beam tests

Beam 

groupa Properties testedb Orientation 

Support 

span (in.) 

Load 

span 

(in.) 

8-LamFbx MORx, Ex, Esf

c Edgewise 

253 50

13-Lam Fbx MORx, Ex, Esf

c Edgewise 

408 82

13-Lam Fby MORy, Ey Flatwise 

65.8 13.1

13-LamFvx Shearx, Ex Edgewise 

117 14

8-LamFt UTS, Eaxial Axiald 152 96

a

Fbx refers to horizontally laminated bending, Fby vertically 

 laminated bending, Fvx horizontally laminated shear, and Ft 

 tension. 

b

MOR is modulus of rupture, E modulus of elasticity, and 

 UTS ultimate tensile strength. 

c Shear-free deflection was measured on 32-in. span for 

 8-lamination beams and 56-in. span for 13-lamination beams. 

d

For axial tests, support span value was distance between grips; 

 load span value was gauge length of aluminum rod. 

MOR of the 8-lamination combination was 6.3% higher and 

the apparent MOE 4.3% higher than that of the 13-

lamination combination. This difference in strength performance can be attributed to volume effect. However, note that 

the 13-lamination beam consisted of 70% No. 2 grade core 

laminations, whereas the 8-lamination beam had only 50% 

No. 2 grade core laminations by design. The higher percentage of high-grade laminations in the 8-lamination beam

would also explain its higher stiffness performance. 

The glulam MOR test results for both beam combinations 

were plotted in the form of cumulative distribution plots 

(Fig. 14). The plots show, as expected, that the average 

MOR of the 8-lamination beam was higher than that of the 

13-lamination beam. 

Volume Effect 

One objective in evaluating two beam sizes was to verify 

that existing industry standards for the volume effect were 

applicable to these ponderosa pine glulam beams. The 

volume effect equation for glulam has the form

x y z

v d w L

C

1/ 1/ 1/ 12 5.125 21⎟

⎠

⎞ ⎜

⎝

⎛ ⎟

⎠

⎞ ⎜

⎝

⎛ ⎟

⎠

⎞ ⎜

⎝

⎛ = (1) 

where 

Cv is volume effect factor, 

d beam depth (in.), 

w beam width (in.), and 

L beam length (ft), and 

x,y,z are exponents for depth, width, and length, 

respectively. 

In current glulam standards, x, y, and z are assigned a value 

of 20 for Southern Pine and 10 for all other species. Glulam

beam data are adjusted to a standard size beam (5.125 in. 

wide, 12 in. deep, 21 ft long). The volume effect exponent

for our set of ponderosa pine glulam beams was calculated 

by transforming the raw data into exponential space and 

performing a simple linear regression analysis on the transformed data. The volume effect exponent was calculated 

using all the beams (n = 29), and this value was found to be 

equal to 0.062, which corresponds to an x, y, and z value of 

16 for Equation (1). Using the industry standard 0.10 volume 

Table 11—Strength and MOE results for flexure, shear, and tension tests of ponderosa pine glulama

Lognormal

distribution 

Normal 

distribution Apparent MOE Shear-free MOE 

Group 

Sample 

size 

Avg 

(lb/in2) 

COV 

(%) 

Avg 

(lb/in2) 

COV 

(%) 

Avg 

(×106

lb/in2

) 

COV 

(%) 

Avg 

(×106

lb/in2

) 

COV 

(%) 

8-Lam Fbx 15 4,560 17.4 4,560 17.3 1.373 5.8 1.508 11.9

13-Lam Fbx 14 4,290 16.7 4,290 16.7 1.316 4.7 1.414 8.0

13-Lam Fby 15 5,720 13.9 5,710 13.8 1.263 7.7 – –

13-Lam Fvx 16 357 33.5 354 28.4 1.047 8.6 – –

8-Lam Ft 15 3,040 14.9 3,040 15.4 1.344 8.2 – –

a No adjustments were made to data; results include all failure modes. 

 For Fbx and Fby groups, strength results are modulus of rupture; for Fvx group, shear strength; for Ft group, 

 tensile strength. For Fbx, Fby, and Fvx groups, stiffness results are bending modulus of elasticity; for Ft group, 

 tensile modulus of elasticity. Fvx group MOE was based on short-span bending test and was heavily 

 influenced by shear deformation. 

13
Figure 16—Cumulative distribution of edgewise glulam 

MOR, adjusted to standard beam dimensions. 

Figure 17—Cumulative distribution of flatwise glulam 

MOR (vertically laminated members). 

Figure 14—Cumulative distribution plots of 8- and 

13-lamination glulam beams (all data). 

Figure 15—Calculated MOE as a function of beam 

volume. 

effect exponent, the two glulam data sets were adjusted to a 

standard size glulam beam. A two-sample t-test determined

that the means of the two distributions of adjusted MOR

were statistically equal. This confirmed that the 8- and 

13-lamination beam data could be combined, after adjustment for the volume effect, and justified the use of the 

0.10 volume effect exponent. Figure 15 shows raw MOR

data plotted as a function of beam volume. 

The beam data for both groups were adjusted to a standard 

beam 5.125 in. wide, 12 in. deep, and 21 ft long. The data

were plotted in Figure 16 in the form of a cumulative 

distribution. 

Flatwise Bending 

The flatwise bending specimens exhibited linear load–

deflection behavior up to initial failure. Initial failure always 

occurred in the outer two E-rated laminations on each side of 

the beam at a strength-controlling knot. A brief reduction in

load was observed after initial failure, and then the load

would increase again at a slightly lower load–deflection 

slope. No visible crushing was observed at the supports or 

loading points, and maximum load was used for bending 

strength calculations. Figure 17 shows a cumulative distribution plot of all 15 beam test results. 

The results in Table 11 show that the calculated MOR value 

of flatwise bending specimens (vertically laminated) were 

significantly higher than those of edgewise bending specimens (horizontally laminated). This is the opposite of what

is commonly found in AITC 117 design (AITC 2004), where 

vertically laminated combinations typically have lower 

design values for Fby. The Fby values are typically lower than

the Fbx values for bending combinations, because the methodology used to calculate allowable bending strength is

governed by the lower-grade core laminations. 

Based on the lognormal distribution, average MOR was 

5,720 lb/in2

 for the flatwise bending specimens and 

4,170 lb/in2

 for the edgewise bending specimens. At the 5th 

percentile (75% tolerance), the flatwise bending specimens

14 
had an MOR of 4,130 lb/in2

 and the edgewise bending specimens an MOR of 2,380 lb/in2

. These results show that the 

ratio of flatwise to edgewise MOR was 1.37 at the average 

and 1.74 at the 5th percentile. By comparison, the Fbx to Fby

ratio in AITC 117 (AITC 2004) is 0.66 for the 16F–E1 

combination and 0.55 for the 20F–E1 combination. Both of 

these combinations were made using Softwood species. In 

conclusion, the results show that the relative performance of

vertically and horizontally laminated beams was much 

higher than what is usually published in existing standards. 

Our results indicate that allowing the low-grade core laminations to govern the allowable Fby properties of a bending 

combination is conservative. 

Figure 18—Cumulative distribution of glulam edgewise

shear. 

Figure 19—Cumulative distribution of glulam tensile

strength. 

Edgewise Shear 

The edgewise shear specimens (Fvx) exhibited linear load–

deflection behavior up to failure. The short-span loading 

configuration was designed so that the majority of members 

would fail in horizontal shear through the inner laminations. 

However, some bending failures were still expected with this 

loading configuration, due to the strength-reducing defects 

present in the outer laminations of the tension zone. In this

study, 9 of 16 beams tested had initial failures as a result of

shear (Fig. 18); the remaining 7 beams had initial failure as a 

result of bending stress in the tension zone. 

Figure 18 shows good overlap of bending and shear failures 

throughout the shear stress distribution. In general, the majority of shear failures (5 of 8) occurred in the lower half of

the distribution and failures were equally distributed (4 of 8) 

in the upper half. This mixture of failure types required a 

censored-data analysis to accurately calculate the characteristic shear stress values of only those beams failing in shear. 

The calculated shear strength results based on a censored 

data analysis of all 16 beams were as follows: 

Lognormal distribution Normal distribution

Avg COV

5th0.75 

 percentile Avg COV 

5th0.75

percentile

525 

lb/in2 21.5% 156 

lb/in2 403

lb/in2 33.1% 143 

lb/in2

Thus, all 16 data values were used in the censored analysis, 

and shear properties were based on 9 shear failures and 

7 censored points. The results were based on the calculated 

correlation between shear and bending, assuming that the 

shear/bending pairs had a bivariate normal distribution. For 

the lognormal case, the shear/bending pairs were assumed to

have a bivariate normal distribution after the logs were 

taken. 

Tension 

The axial tension specimens exhibited linear load–deflection 

behavior, with ultimate failure occurring abruptly. Significant cracking usually began at about 50% of ultimate load; 

however, no visible failures were seen until ultimate failure. 

Failures were observed to follow a path of least resistance 

from strength-reducing defects in one lamination to the next;

failures were primarily observed at knots and pith-associated 

wood. Figure 19 is a cumulative distribution plot of all 

15 tension test results. 

Modulus of Elasticity 

For edgewise bending (MOEx), the design glulam MOE 

level was 1.2 ×106

 lb/in2, based on the assumed properties of 

Table 4 and taking 95% of the MOE calculated by a transformed section analysis (ASTM 2004a). The average glulam

MOE results calculated from beam tests were 1.373 and 

1.313 ×106

 lb/in2 for the 8- and 13-lamination beams, respectively. For the members tested in flatwise bending, the calculated design MOE value was 1.07 ×106

 lb/in2, based on 

15
Table 4 lumber properties and taking 95% of the average 

lumber MOE of all laminations (ASTM 2000a). The average 

MOE values calculated from beam tests was 1.263 × 

106

 lb/in2 for the 13-lamination flatwise members. For the 

axially loaded members, the calculated design MOE value 

was 1.12 ×106 lb/in2, based on Table 4 lumber properties and 

taking the weighted average lumber MOE of all laminations

(ASTM 2000a). The average glulam axial MOE was 

1.344 ×106

 lb/in2 for the 8-lamination beams. In all instances, the experimental beam test results exceeded the 

calculated design levels based on design lumber MOE properties. Note that the 8-lamination glulam combination had 

slightly higher MOE values in all cases as a result of the 

larger percentage of higher-MOE outer laminations. 

In this study, shear-free deflections were also measured on 

the edgewise bending members, which allowed comparison 

of the two types of calculated MOE values. The U.S. standards for glulam are based on long-span deflections and the 

international glulam standards on shear-free deflections. For 

the 8- and 13-lamination beam combinations, the calculated 

shear-free MOE values were respectively 9.8% and 7.6% 

higher than the calculated long-span MOE values. This

relationship is important to understand because it shows that 

the same beam combination can have two different reported 

MOE values, based on the type of deflection that is 

measured. 

Analysis 

Glulam Design Values 

In this section, we describe the procedures used to calculate

the allowable design values for each mechanical property of 

glulam. For all strength properties, the allowable design 

values are based on the calculated 5th percentile of the 

strength distribution. The allowable design strength values 

for bending, tension, and shear were calculated using the 

following equation:

F = ( ) 5th0.75 2.1 (2) 

where F is calculated design strength value, 5th0.75 is 5th

percentile strength value at 75% tolerance, and 2.1 is a factor

that includes adjustment for safety and duration of load. For 

glulam MOE, the allowable design value is the average of 

the apparent MOE distribution, as reported in Table 11. 

Edgewise Bending Strength (Fbx) 

The 5th percentile (at 75% tolerance) edgewise MOR was 

calculated from the combined data (adjusted for volume 

effect) shown in Figure 16, which resulted in a value of 

3,020 lb/in2

. The allowable design bending strength Fbx was 

determined to be 1,440 lb/in2

. As previously mentioned, the 

only all ponderosa pine glulam combination in existing 

standards that could be made with this resource is the homogeneous L3 combination, which has an Fbx value of 

850 lb/in2

. Thus, through mechanical grading of the outer 

lamination grades, a new combination was developed that

could offer a 69% increase in allowable design bending 

strength compared with the currently available strength value 

in existing standards. 

Flatwise Bending Strength (Fby) 

The 5th percentile (at 75% tolerance) flatwise MOR was 

calculated from the data shown in Figure 17, which resulted 

in a value of 4,130 lb/in2

. Design values for beams in the 

flatwise orientation (vertically laminated) were based on a 

12-in.-deep member, and our experimental beams were only

3-1/8-in. deep. The flat-use factor from AITC 117 (AITC

1993) that converts from a 3-1/8-in. to a 12-in. depth is 1.16. 

Using Equation (2), the allowable design bending strength 

Fby was determined to be 1,970 lb/in2

. After applying the 

flat-use factor, this value was 1,695 lb/in2

. This compares 

favorably with the homogeneous L3 combination, which has 

an Fby value of 800 lb/in2

, resulting in a 111% improvement

over the comparable combination in existing standards. 

Shear Strength (Fvx) 

The 5th percentile (at 75% tolerance) shear strength based

on a censored data analysis and a lognormal distribution was 

156 lb/in2

. Using Equation (2), the allowable design shear 

strength Fvx was determined to be 74 lb/in2

. This value is 

significantly lower than that published for the all-L3 Western Woods combination of 120 lb/in2

. This leads us to believe that the published design shear strength value for 

glulam beams made with Western Wood core laminations 

may be non-conservative when applied to glulam beams 

with ponderosa pine core laminations. 

Tension Strength (Ft) 

The 5th percentile (at 75% tolerance) tensile strength was 

calculated from the data shown in Figure 19, which resulted 

in a value of 2,140 lb/in2

. Using Equation (2), the allowable 

design tensile strength Ft was determined to be 1,020 lb/in2

. 

This compares favorably to two industry standards and 

results in a 94% improvement over the homogeneous L3 

combination, which has an Ft value of 525 lb/in2

. In addition, the ASTM D 3737 standard (ASTM 2000a) does not

have any provisions for calculating glulam tension strength, 

based on the properties of the laminating lumber. So, the 

relationship in the D 3737 standard assumes that design 

tensile strength (Ft) is 5/8 times the value of the design 

edgewise bending strength (Fbx). The ratio that we found 

experimentally was 0.70, with a 95% confidence interval of 

0.58 to 0.83. This confidence interval is based on the assumption of lognormal distributions for both the tensile and 

bending strengths. These results confirm that the ASTM 

D 3737 5/8 factor is adequate for these beams. 

16 
Solid-Sawn Lumber Properties 

To gauge the relative quality of the lumber used in this 

study, we compared the mechanical properties of our core 

lamination grade to past data on No. 2 grade ponderosa pine 

lumber. The average MOE of our core lamination grade 

(1.11 ×106

 lb/in2) exceeded the value from the In-Grade 

Testing Program (0.98 ×106

 lb/in2, Green and Evans 1987) 

and by far exceeded the value observed in the Emmett, 

Idaho, study (0.86 ×106 lb/in2), which was also derived from

a small-diameter timber resource (Table 3; Gorman and 

Green 2000). For edgewise bending strength, our core lamination grade achieved an average MOR value of 4,600 lb/in2

(Table 9), which was lower than the In-Grade average MOR 

for No. 2 grade ponderosa pine (5,290 lb/in2

), yet was higher 

than the Emmett data (3,880 lb/in2

). For shear strength, the 

core lamination grade had an average shear strength of 

875 lb/in2

, which exceeded the ASTM D 2555 value of 

795 lb/in2

 (adjusted to 12% moisture content). Overall, we 

observed that although this set of lumber had higher stiffness 

and shear strength properties, it was lower in bending 

strength properties than the ponderosa pine lumber tested in

the In-Grade Testing Program (Green and Evans 1987). This

indicates that lumber processed from small-diameter timber 

resources is more likely to have a higher percentage of juvenile wood and thus has lower strength properties in tension 

and bending. 

Comparison of Experimental 

and Alllowable Properties 

In summary, Table 12 compares allowable glulam beam

properties determined experimentally in this study and allowable properties for the all-L3 homogeneous beam combination currently available in the glulam standards. The ratio

for our results (Fig. 2) and the all-L3 combination was also

determined. 

ASTM D 3737 Re-Analysis 

A final analysis of the glulam beam combination involved 

re-analysis of the bending strength and stiffness values using 

actual measured lumber properties. In place of the assumed 

lumber properties in Table 4, we used the actual lumber 

MOE values for the three zones of lumber grades and the 

actual knot properties for the 1.4E grades reported in 

Table 7. The knot properties used for the No. 2 grade of 

lumber were the same as those reported in Table 4. 

The re-analysis of the 8-lamination beam indicated a design 

glulam MOE of 1.190 ×106

 lb/in2 and a design bending 

strength (Fbx) of 1,279 lb/in2

. The re-analysis of the 

13-lamination beam indicated a design glulam MOE of 

1.234 ×106

 lb/in2 and a design bending strength of 

1,328 lb/in2

. The design glulam MOE value was again calculated to be 1.2 ×106

 lb/in2 using ASTM D 3737 procedures, 

and the fact that the experimental results exceeded this level 

shows that this target MOE level is technically feasible. The 

design bending strength, on the other hand, was calculated to

be approximately 1,300 lb/in2

 using the D 3737 procedures. 

This level, however, is based on the use of a special tension 

lamination. Because we did not use a special tension lamination grade, D 3737 procedures require that this design bending stress be reduced to 1,100 lb/in2

 for beams ≤15 in. deep 

and 975 lb/in2

 for beams >15 in. deep. Because our experimental results showed that this beam combination can 

achieve a design bending strength of approximately

1,400 lb/in2

, this leads us to believe that the special tension

lamination requirements calculated by the D 3737 standard 

are not accurate for design stresses as low as these. In other 

words, special tension lamination grades were developed to

ensure that glulam beams having higher design bending 

stress values, in the range of 2,200 to 2,400 lb/in2

, achieve 

these levels of strength. Without considering this special

tension lamination adjustment, the difference between the 

experimentally determined design bending strength and the 

calculated design bending strength was approximately 10%. 

In addition, the ANSI/AITC A190.1 standard requires that

the 5th percentile finger-joint tensile strength value must 

achieve a level of strength that is 1.67 times the design 

bending strength of glulam beams. This ratio of finger-joint

5th percentile to glulam design bending strength is referred

to as the qualification stress level (QSL). We calculated a 

QSL factor from our test data of 1.17 (1,690 lb/in2

/ 

1,440 lb/in2

), which is well below the required 1.67 factor. 

When calculating a similar qualification stress level based on 

the 5th percentile solid-sawn lumber tensile strength of the 

1.4-1/4 grade from Table 9, we found the ratio to be 1.52 

(2,195/1,440 lb/in2

). 

Conclusions 

This study involved the evaluation of ponderosa pine glulam

made from lumber sawn from a small-diameter timber resource. Lumber sawn from small-diameter ponderosa pine 

was found to be feasible for the development of E-rated 

lumber grades, having average MOE values of 1.0 and 

1.4 ×106

 lb/in2. We observed that approximately 66% of this

lumber resource would qualify for these E-rated lumber 

grades. 

Table 12—Comparison of allowable design values for 

ponderosa pine glulam

Allowable design value 

Property

Calculated 

in study

All-L3 

grade 

combination 

Ratio of 

study to L3 

combination 

Fbx (lb/in2

) 1,440 850 1.69

Fby (lb/in2) 1,695 800 2.12

Ft (lb/in2

) 1,020 500 2.04

Fvx (lb/in2

) 74 120 0.62

MOE (106

 lb/in2) 1.34 1.00 1.34

17
Two different glulam beam depths were evaluated: 8 and 

13 laminations. The 8-lamination glulam beam combination 

was targeted for Fbx and Ft tests and the 13-lamination glulam beam combination for Fbx, Fby, and Fvx tests. Beam

deflection was measured during these strength tests, and a 

variety of glulam MOE values were determined. The calculated design values for the various mechanical properties of 

this new ponderosa pine glulam beam combination were 

compared to the published design values of the L3 glulam

combination (combination 22 from AITC 117). Overall, we 

determined that using mechanically graded lumber in the 

glulam combination resulted in a structural member that 

efficiently utilized this small-diameter ponderosa pine resource. The calculated design values of this new glulam

combination are a significant improvement over the published design values of the all ponderosa pine L3-grade 

combination that is currently available in the standards. 

Analysis of the glulam beam and laminating lumber test

results showed that the industry standard volume effect

exponent of 0.10 is appropriate for these ponderosa pine 

glulam beams. The ratio of glulam tensile strength (Ft) to 

glulam bending strength (Fbx) was found to be 0.70, which 

further supports the industry standard value of 5/8 (0.625). 

Finally, the qualification stress levels of finger-jointed and 

solid-sawn lumber tensile strength were found to be 1.17 and 

1.52 times that of the calculated design bending strength of 

the glulam beams. These two values are significantly lower 

than the industry standard value of 1.67, which indicates that

there may be a grade-dependent or layup effect on this 

qualification stress level factor. 

Literature Cited 

AITC. 2004. Standard specifications for structural glued 

laminated timber of softwood species. AITC 117–04. 

Englewood, CO: American Institute of Timber Construction. 

http://www.aitc-glulam.org/

ASTM. 2000a. Standard practice for establishing stresses 

for structural glued laminated timber (glulam). Vol. 4.10, 

ASTM D 3737–99. West Conshohocken, PA: American 

Society for Testing and Materials. 

http://www.astm.org/

ASTM. 2000b. Standard test methods for static tests of 

lumber in structural sizes. Vol. 4.10, ASTM D 198–99. 

American Society for Testing and Materials, West 

Conshohocken, PA. 

http://www.astm.org/

ASTM. 2000c. Standard practice for establishing structural

grades and related allowable properties for visually graded 

lumber. Vol. 4.10, ASTM D245–99. West Conshohocken, 

PA: American Society for Testing and Materials. 

http://www.astm.org/

Burns, R.M.; Honkala, B.H. 1990. Silvics of North America. Vol. I, Conifers. Agric. Handb. 654. Washington, DC:

U.S. Department of Agriculture, Forest Service. 675 p. 

Erickson, R.G.; Gorman, T.M.; Green, D.W.; Graham, 

D. 2000. Mechanical grading of lumber sawn from smalldiameter lodgepole pine, ponderosa pine, and grand fir 

trees from northern Idaho. Forest Products Journal.

50(7/8):59–65. 

Forest Products Laboratory. 2000. Forest Products 

Laboratory research program on small-diameter material. 

Gen. Tech. Rep. FPL–GTR–110 (Rev.). Madison, WI: 

U.S. Department of Agriculture, Forest Service, Forest 

Products Laboratory. 31 p. 

Gorman, T.M.; Green, D.W. 2000. Mechanical grading of 

lumber sawn from small-diameter Rocky Mountain species. 

In: Proc., Gazo, R., ed. Issues related to handling the influx

of small-diameter timber in western North America. 

No. 7261, Madison, WI. Forest Products Society: 29–35. 

Green, D.W.; Evans, J.W. 1987. Mechanical properties of 

visually graded dimension lumber. NTIS PB–88–159–371, 

vol. 1–7. Springfield, VA: National Technical Information 

Service. 

Hernandez, R.; Moody, R.C.; Falk, R.H. 1995. Fiber 

stress values for design of glulam timber utility structures. 

FPL–RP–532. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 23 p. 

Lowell, E.C.; Green, D.W. 2000. Lumber recovery from

small-diameter ponderosa pine from Flagstaff, AZ. In: Proc. 

RMRS–P–22. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 

NDS. 1997. National design specification for wood construction. Supplement. Washington, DC: American Forest 

& Paper Association, American Wood Council. 

http://www.awc.org/

Simpson, W.T.; Green, D.W. 2001. Effect of drying methods on warp and grade of 2 by 4’s from small-diameter 

ponderosa pine. Res. Pap. FPL–RP–601. Madison, WI: 

U.S. Department of Agriculture, Forest Service, Forest 

Products Laboratory. 17 p. 

Voorhies, G.; Gorman, W.A. 1982. Longitudinal shrinkage 

and occurrence of various fibril angles in juvenile wood of 

young-growth ponderosa pine. Arizona Forestry Notes 16. 

Flagstaff, AZ: University of Northern Arizona. 

WWPA. 2000. Western lumber grading rules. Portland, OR:

Western Wood Products Association. 

Yeh, B. 1997. Shear strength of structural glued laminated 

timber based on full size flexure tests. APA Rep. T97–25. 

Tacoma, WA: APA–The Engineered Wood Association. 

 

18 
Appendix A—Glulam Beam 

Maps of Lumber MOE Values 

The following figures are glulam beam maps for the 8- and 

13-lamination beams tested in this study. The MOE values 

were determined using the continuous lumber tester (CLT) 

at the laminating plant and were not adjusted. The location 

of finger joints, accurate to within 1/4-ft, is indicated on 

each map. 

8-Lamination Beam Maps (Edgewise Specimens) 

19
20 
21
22 
13-Lamination Beam Maps (Edgewise, Flatwise, and Shear Specimens) 

23
24 
25
26 
27
28 
29
30 
31
32 
33
Appendix B—Knot Properties 

of Ponderosa Pine Laminating 

Lumber 

Figure B1—Calculated x-bar and h values for ponderosa

pine 1.0E–1/2 EK grade. 

Figure B2—Standard error of estimates from x-bar and h

calculations for ponderosa pine 1.0E–1/2 EK grade. 

The ASTM D 3737 standard (ASTM 2000a) specifies that at

least 1,000 lineal ft of lumber for each grade should be 

targeted for knot property measurements when a new species 

or grade of lumber is being established. In this study, we 

measured the knot properties of the following E-rated 

grades: 1.4E–1/4, 1.4E–1/2, 1.0E–1/4, and 1.0E–1/2. These 

grades include the two grades used in the targeted glulam

beam combinations as well as two lower-MOE grades that 

are candidates for future combinations of ponderosa pine 

glulam. In analyzing these properties, we also conducted a 

study to evaluate the 1,000 lineal ft requirement on knot

property measurements. 

Figure B1 shows the calculated x-bar and h values for both 

individual groups of 60 lineal ft and a cumulative total for 

the 1.0E–1/2 edge-knot grade. Results vary greatly when 

measured in only 60 lineal ft increments. However, note that 

after approximately 500 lineal ft, the cumulative x-bar and 

h values appear to settle into a constant value. To study this 

further, Figure B2 was plotted to show the standard error of 

the estimates from the regression analysis used to calculate 

the x-bar and h values from Figure B1. Figure B2 shows that

the standard error values settle into a constant value after 

approximately 500 lineal ft. 

Because the results with the 1.0E–1/2EK grade indicated 

that 500 lineal ft was an adequate amount of lumber for 

measuring knot properties, we targeted measurements for 

every 500 lineal ft for each remaining E-rated grade of ponderosa pine. 

The following figures show calculated x-bar and h values 

and standard errors of estimates for various ponderosa pine 

edge-knot grades. For each figure, analysis was conducted 

on groups of 60 lineal ft and the cumulative total.

34 
Figure B3—Calculated x-bar and h values for ponderosa

pine 1.0E-–1/4 EK grade. 

Figure B4—Standard error of estimates from x-bar and 

h calculations for ponderosa pine 1.0E–1/4 EK grade.

Figure B5—Calculated x-bar and h values for ponderosa

pine 1.4E–1/2 EK grade. 

Figure B6—Standard error of estimates from x-bar and 

h calculations for ponderosa pine 1.4E–1/2 EK grade. 

Figure B7—Calculated x-bar and h values for ponderosa

pine 1.4E–1/4 EK grade. 

Figure B8—Standard error of estimates from x-bar and 

h calculations for ponderosa pine 1.4E–1/4 EK grade. 

35
Appendix C—Individual Glulam 

Beam Test Results 

Table C1—Results of edgewise bending tests of 8-lamination ponderosa pine 

glulam beams (Fig. 10) 

Beam ID 

Width 

(in.) 

Depth 

(in.) 

Max load 

(lb) 

MOR 

(lb/in2

) 

LS MOE 

(106 lb/in2) 

SF MOE 

(106 lb/in2) 

08-01B 3.13 12.00 7,837 5,294 1.392 1.619

08-02B 3.13 11.94 6,738 4,598 1.522 1.709

08-03B 3.13 11.94 5,420 3,698 1.345 1.217

08-04B 3.13 11.94 5,493 3,749 1.252 1.202

08-05B 3.19 11.84 5,176 3,524 1.494 1.544

08-06B 3.13 11.94 8,106 5,531 1.389 1.711

08-07B 3.13 11.94 6,934 4,731 1.338 1.502

08-08B 3.13 11.94 6,445 4,398 1.344 1.553

08-09B 3.13 11.88 5,444 3,753 1.455 1.841

08-10B 3.19 11.88 8,716 5,895 1.323 1.475

08-11B 3.13 11.94 7,813 5,331 1.432 1.630

08-12B 3.19 11.85 7,959 5,410 1.242 1.404

08-13B 3.13 11.94 6,885 4,698 1.392 1.448

08-14B 3.13 11.88 5,615 3,868 1.327 1.335

08-15B 3.13 11.88 5,664 3,904 1.346 1.424

08-16B 3.19 11.94 7,324 4,904 1.781 2.160

Table C2—Results of edgewise bending tests of 13-lamination ponderosa pine 

glulam beams (Fig. 10) 

Beam ID 

Width 

(in.) 

Depth 

(in.) 

Max load 

(lb) 

MOR 

(lb/in2) 

LS MOE 

(106 lb/in2) 

SF MOE 

(106 lb/in2) 

13-01BX 3.13 19.50 13,700 5,627 1.417 1.573

13-02BX 3.13 19.38 9,420 3,920 1.316 1.345

13-03BX 3.13 19.31 12,280 5,145 1.313 1.503

13-04BX 3.13 19.38 5,860 2,437 1.264 1.404

13-05BX 3.13 19.31 12,110 5,074 1.300 1.481

13-06BX 3.13 19.31 9,230 3,867 1.299 1.352

13-07BX 3.13 19.31 9,720 4,071 1.263 1.464

13-08BX 3.13 19.38 10,690 4,448 1.383 1.449

13-09BX a 3.13 19.44 8,200 3,390 1.312 NA

13-10BX 3.13 19.31 8,200 3,437 1.314 1.334

13-11BX 3.13 19.38 10,160 4,225 1.229 1.223

13-12BX 3.13 19.31 12,110 5,074 1.335 1.472

13-13BX 3.13 19.31 10,470 4,388 1.329 1.433

13-14BX 3.13 19.50 8,110 3,330 1.202 1.212

13-15BX 3.13 19.35 9,640 4,026 1.417 1.538

13-16BX a 3.13 19.30 12,680 5,318 1.518 NA

a

Long-span (LS) deflections based on manual readings (LVDT data unreliable for test). SF designates 

shear-free. 

36 
Table C3—Results of flatwise bending tests of 13-lamination ponderosa 

pine glulam beams (Fig. 11). 

Beam ID 

Width 

(in.) 

Depth 

(in.) 

Max load 

(lb) 

MOR 

(lb/in2) 

LS MOE 

(106 lb/in2) 

13-01BY 19.44 3.13 11,740 4,866 1.192

13-02BY 19.25 3.13 14,800 6,193 1.262

13-03BY 19.38 3.13 14,310 5,946 1.326

13-04BY 19.31 3.13 13,110 5,469 1.142

13-05BY 19.31 3.13 14,110 5,886 1.362

13-06BY 19.25 3.00 13,110 5,972 1.328

13-07BY 19.38 3.13 10,690 4,445 1.150

13-08BY 19.25 3.13 16,530 6,916 1.422

13-09BY 19.44 3.06 16,210 7,028 1.378

13-10BY 19.5 3.13 11,740 4,851 1.165

13-11BY 19.44 3.06 15,280 6,626 1.327

13-12BY 19.44 3.13 12,820 5,311 1.185

13-13BY 19.44 3.13 14,280 5,918 1.281

13-14BY 19.38 3.06 12,570 5,468 1.311

13-15BY 19.38 3.125 11,450 4,774 1.119

13-16BY 19.38 3.13 16,920 7,032 NA

Table C4—Results of edge-wise shear tests of 13-lamination ponderosa pine glulam

beams (Fig. 12) 

Beam ID 

Width 

(in.) 

Depth 

(in.) 

Max load 

(lb) 

Shear 

stress 

(lb/in2

) 

MOR at 

failure 

(lb/in2

) 

LS MOE 

(106 lb/in2) 

Failure 

type 

13-01V 3.06 19.44 18,340 231.2 2,450 1.051 Shear

13-02V 3.06 19.56 11,620 145.6 1,534 0.949 Shear

13-03V 3.06 19.41 22,830 288.2 3,059 1.038 Shear

13-04V 3.13 19.38 20,870 258.1 2,743 1.058 Shear

13-05V 3.06 19.31 29,200 370.6 3,954 1.119 Shear

13-06V 3.13 19.25 28,490 354.6 3,795 0.991 Bending

13-07V 3.13 19.38 36,160 447.1 4,752 0.945 Bending

13-08V 3.13 19.25 27,690 344.6 3,688 1.394 Bending

13-09V 3.06 19.38 32,470 410.7 4,365 1.054 Bending

13-10V 3.09 19.47 23,970 298.9 3,162 1.037 Shear

13-11V 3.06 19.44 33,080 417.1 4,420 1.021 Shear

13-12V 3.13 19.31 21,220 263.3 2,809 0.942 Bending

13-13V 3.06 19.31 37,230 472.6 5,041 1.118 Shear

13-14V 3.06 19.31 41,360 524.9 5,600 0.989 Bending

13-15V 3.06 19.27 30,620 389.4 4,163 1.104 Bending

13-16V 3.13 19.31 35,520 440.8 4,702 1.291 Shear

37
Table C5—Results of tension tests of 8-lamination ponderosa pine glulam

beams (Fig. 13) 

Beam ID 

Width 

(in.) 

Depth 

(in.) 

Max load 

(lb) 

UTS 

(lb/in2

) 

Axial MOE 

(106 lb/in2) 

08-01B 3.125 11.875 121,400 3,271 1.341

08-02B 3.125 11.875 118,600 3,196 1.347

08-03B 3.125 11.875 113,000 3,045 1.244

08-04B 3.125 11.875 110,900 2,988 1.373

08-05B 3.125 11.875 114,800 3,094 1.446

08-06B 3.125 11.875 142,700 3,845 1.432

08-07B 3.125 11.875 98,400 2,652 1.400

08-08B 3.125 11.875 100,200 2,700 1.041

08-09B 3.125 11.875 100,600 2,711 1.304

08-10B 3.125 11.875 90,100 2,428 1.384

08-11B 3.125 11.875 90,100 2,428 1.222

08-12B 3.125 11.875 106,400 2,867 1.432

08-13B 3.125 11.875 121,900 3,285 1.380

08-14B 3.125 11.875 110,300 2,972 1.488

08-15B 3.125 11.875 151,700 4,088 1.327

08-16B 3.125 11.875 132,800 3,579 1.753

38