ASTM D7199-07(2012)
(Practice)Standard Practice for Establishing Characteristic Values for Reinforced Glued Laminated Timber (Glulam) Beams Using Mechanics-Based Models
Standard Practice for Establishing Characteristic Values for Reinforced Glued Laminated Timber (Glulam) Beams Using Mechanics-Based Models
ABSTRACT
This practice covers mechanics-based models for calculating characteristic values for the strength and stiffness of reinforced structural glued laminated timbers (glulam). The mechanics-based analyses shall account for the following: (1) stress-strain relationships for wood laminations and reinforcement; (2) strain compatibility; (3) equilibrium; (4) variability of mechanical properties; (5) volume effects; (6) finger-joint effects; (7) laminating effects; and (8) stress concentrations at the termination of reinforcement in beams with partial length reinforcement. This practice also provides for minimum physical test requirements to validate mechanics-based models. A minimum set of performance-based durability test requirements for reinforced glulams is also herein described. Additional durability test requirements shall be considered in accordance with the specific end-use environment.
SCOPE
1.1 This practice covers mechanics-based requirements for calculating characteristic values for the strength and stiffness of reinforced structural glued laminated timbers (glulam) manufactured in accordance with applicable provisions of ANSI/AITC A190.1, subjected to quasi-static loadings. It addresses methods to obtain bending properties parallel to grain, about the x-x axis (Fbx and Ex) for horizontally-laminated reinforced glulam beams. Secondary properties such as bending about the y-y axis (Fby), shear parallel to grain (F vx and Fvy), tension parallel to grain (Ft), compression parallel to grain (Fc), and compression perpendicular to grain (Fc⊥) are beyond the scope of this practice. When determination of secondary properties is deemed necessary, testing according to other applicable methods, such as Test Methods D143, D198 or analysis in accordance with Practice D3737, is required to establish these secondary properties. Reinforced glulam beams subjected to axial loads are outside the scope of this standard. This practice also provides minimum test requirements to validate the mechanics-based model.
1.2 The practice also describes a minimum set of performance-based durability test requirements for reinforced glulams, as specified in Annex A1. Additional durability test requirements shall be considered in accordance with the specific end-use environment. Appendix X1 provides an example of a mechanics-based methodology that satisfies the requirements set forth in this standard.
1.3 Characteristic strength and elastic properties obtained using this standard may be used as a basis for developing design values. However, the proper safety, serviceability and adjustment factors including duration of load, to be used in design are outside the scope of this standard.
1.4 This practice does not cover unbonded reinforcement, prestressed reinforcement, nor shear reinforcement.
1.5 The values stated in SI units are to be regarded as standard. The mechanics based model may be developed using SI or in.-lb units.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: D7199 − 07 (Reapproved 2012)
Standard Practice for
Establishing Characteristic Values for Reinforced Glued
Laminated Timber (Glulam) Beams Using Mechanics-Based
Models
This standard is issued under the fixed designation D7199; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 The values stated in SI units are to be regarded as
standard. The mechanics based model may be developed using
1.1 This practice covers mechanics-based requirements for
SI or in.-lb units.
calculatingcharacteristicvaluesforthestrengthandstiffnessof
1.6 This standard does not purport to address all of the
reinforced structural glued laminated timbers (glulam) manu-
safety concerns, if any, associated with its use. It is the
factured in accordance with applicable provisions of ANSI/
responsibility of the user of this standard to establish appro-
AITC A190.1, subjected to quasi-static loadings. It addresses
priate safety and health practices and determine the applica-
methods to obtain bending properties parallel to grain, about
bility of regulatory limitations prior to use.
the x-x axis (F and E ) for horizontally-laminated reinforced
bx x
glulam beams. Secondary properties such as bending about the
2. Referenced Documents
y-y axis (F ), shear parallel to grain (F and F ), tension
by vx vy
parallel to grain (F), compression parallel to grain (F ), and
2.1 ASTM Standards:
t c
compressionperpendiculartograin(F')arebeyondthescope
D9 Terminology Relating to Wood and Wood-Based Prod-
c
of this practice.When determination of secondary properties is
ucts
deemed necessary, testing according to other applicable
D143 Test Methods for Small Clear Specimens of Timber
methods, such as Test Methods D143, D198 or analysis in
D198 Test Methods of Static Tests of Lumber in Structural
accordance with Practice D3737, is required to establish these
Sizes
secondary properties. Reinforced glulam beams subjected to
D905 Test Method for Strength Properties of Adhesive
axial loads are outside the scope of this standard. This practice
Bonds in Shear by Compression Loading
also provides minimum test requirements to validate the
D1990 Practice for Establishing Allowable Properties for
mechanics-based model.
Visually-Graded Dimension Lumber from In-Grade Tests
of Full-Size Specimens
1.2 The practice also describes a minimum set of
D2559 Specification for Adhesives for Bonded Structural
performance-based durability test requirements for reinforced
Wood Products for Use Under Exterior Exposure Condi-
glulams, as specified in Annex A1. Additional durability test
tions
requirements shall be considered in accordance with the
D2915 Practice for Sampling and Data-Analysis for Struc-
specific end-use environment. Appendix X1 provides an ex-
tural Wood and Wood-Based Products
ample of a mechanics-based methodology that satisfies the
D3039/D3039M Test Method for Tensile Properties of Poly-
requirements set forth in this standard.
mer Matrix Composite Materials
1.3 Characteristic strength and elastic properties obtained
D3410/D3410M Test Method for Compressive Properties of
using this standard may be used as a basis for developing
Polymer Matrix Composite Materials with Unsupported
design values. However, the proper safety, serviceability and
Gage Section by Shear Loading
adjustment factors including duration of load, to be used in
D3737 Practice for Establishing Allowable Properties for
design are outside the scope of this standard.
Structural Glued Laminated Timber (Glulam)
1.4 This practice does not cover unbonded reinforcement,
D4761 Test Methods for Mechanical Properties of Lumber
prestressed reinforcement, nor shear reinforcement. and Wood-Base Structural Material
D5124 Practice for Testing and Use of a Random Number
This practice is under the jurisdiction of ASTM Committee D07 on Wood and
is the direct responsibility of Subcommittee D07.02 on Lumber and Engineered
Wood Products. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2012. Published October 2012. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2006. Last previous edition approved in 2007 as D7199 – 07. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7199-07R12. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7199 − 07 (2012)
Generator in Lumber and Wood Products Simulation example, polypropylene or nylon) or thermosetting (for
example, epoxy or vinyl-ester).
2.2 Other Standard:
ANSI/AITC A190.1 Structural Glued Laminated Timber
3.2.7 laminating effect—an apparent increase of lumber
lamination tensile strength because it is bonded to adjacent
3. Terminology
laminations within a glulam beam. This apparent increase may
3.1 Definitions—Standard definitions of wood terms are
be attributed to a redirection of stresses around knots and grain
given in Terminology D9 and standard definitions of structural
deviations through adjacent laminations.
glued laminated timber terms are given in Practice D3737.
3.2.8 partial length reinforcement—reinforcement that is
3.2 Definitions of Terms Specific to This Standard: terminated within the length of the timber.
3.2.1 bonded reinforcement—a reinforcing material that is
3.2.9 reinforcement—any material that is not a conventional
continuously attached to a glulam beam through adhesive
lamstock whose mean longitudinal ultimate strength exceeds
bonding.
20 ksi for tension and compression, and whose mean tension
3.2.2 bumper lamination—a wood lamination continuously
and compression MOE exceeds 3000 ksi, when placed into a
bonded to the outer side of reinforcement.
glulamtimber.Acceptablereinforcingmaterialsincludebutare
not restricted to: fiber-reinforced polymer (FRP) plates and
3.2.3 compression reinforcement—reinforcement placed on
bars,metallicplatesandbars,FRP-reinforcedlaminatedveneer
the compression side of a flexural member.
lumber (LVL), FRP-reinforced parallel strand lumber (PSL).
3.2.4 conventional wood lamstock—solid sawn wood lami-
3.2.10 shear reinforcement—reinforcement intended to in-
nations with a net thickness of 2 in. or less, graded either
crease the shear strength of the beam. This standard does not
visually or through mechanical means, finger-jointed and
cover shear reinforcement.
face-bonded to form a glulam.
3.2.5 development length—the length of the bond line along 3.2.11 tension reinforcement—reinforcement placed on the
tension side of a flexural member.
the axis of the beam required to develop the design tensile
strength of the reinforcement.
3.3 Symbols:
3.2.6 fiber-reinforced polymer (FRP)—any material consist-
Arm = moment arm, distance between compression and
ing of at least two distinct components: reinforcing fibers and
tension force couple applied to beam cross-section
a binder matrix (a polymer). The reinforcing fibers are permit-
b = beam width
ted to be either synthetic (for example, glass), metallic, or
C = total internal compression force within the beam cross-
natural (for example, wood), and are permitted to be long and
section (see Fig. 2)
continuously-oriented, or short and randomly oriented. The
CFRP = carbon fiber reinforced polymer
binder matrix is permitted to be either thermoplastic (for
d = beam depth
E = long-span flatwise-bending modulus of elasticity for
wood lamstock (Test Methods D4761; also see Fig. 1)
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
F = allowable bending stress parallel to grain
b
4th Floor, New York, NY 10036, http://www.ansi.org.
FIG. 1 Typical Stress-Strain Relationship for Wood Lamstock, with Bilinear Approximation
D7199 − 07 (2012)
NOTE 1—A simplified rectangular block stress distribution can be used but it must be shown that it accurately represents the stress distribution.
FIG. 2 Example of Beam Section with Strain, Stress, and Force Diagrams
F = internal horizontal force on the beam cross-section (see ρ = tension reinforcement ratio (%); cross-sectional area of
x
Eq 2) tension reinforcement divided by cross-sectional area of beam
between the c.g. of tension reinforcement and the extreme
GFRP = Glass fiber-reinforced polymer
compression fiber
LEL = lower exclusion limit (point estimate with 50 %
confidence, includes volume factor)
ρ' = compression reinforcement ratio (%); cross-sectional
LTL = lower tolerance limit (typically calculated with 75 %
area of compression reinforcement divided by cross-sectional
confidence)
area of beam between the c.g. of compression reinforcement
M = external moment applied to the beam cross-
and the extreme tension fiber
applied
section
σ(y) = stress distribution through beam depth (see Fig. 2)
M = internal moment on the beam cross-section
internal
MC = moisture content (%)
4. Requirements for Mechanics-Based Analysis
MOE = modulus of elasticity
Methodology
MOR = modulus of rupture
NOTE 1—At a minimum, the mechanics-based analysis shall account
MOR = 5 % one-sided lower tolerance limit for modulus for: (1) Stress-strain relationships for wood laminations and reinforce-
5%
ment;(2)Straincompatibility;(3)Equilibrium;(4)Variabilityofmechani-
of rupture, including the volume factor
cal properties; (5) Volume effects; (6) Finger-joint effects; (7) Laminating
MOR = 5 % one-sided lower tolerance limit for modu-
BL5%
effects; and (8) Stress concentrations at termination of reinforcement in
lus of rupture corresponding to failure of the bumper
beams with partial length reinforcement. In addition to the above factors,
lamination, including the volume factor
characteristic values developed using the mechanics-based model need to
be further adjusted to address end-use conditions including moisture
m*E = downward slope of bilinear compression stress-strain
effects, duration of load, preservative treatment, temperature, fire, and
curve for wood lamstock (see Fig. 1)
environmental effects. The development and application of these addi-
N.A. = neutral axis
tional factors are outside the scope of this practice. Annex A1 addresses
T = total internal tension force within the beam cross-section
the evaluation of durability effects. The minimum output requirements for
the analysis are mean MOE (based on gross section) and 5% LTL MOR
(see Fig. 2)
with 75 % confidence (based on gross section), both at 12 % MC. These
UCS = ultimate compressive stress parallel to grain
analysis requirements are described below.
UTS = ultimate tensile stress parallel to grain
4.1 Stress-strain Relationships:
Y = distance from extreme compression fiber to neutral axis
(see Fig. 2)
4.1.1 Conventional Wood Lamstock:
y = distance from extreme compression fiber to point of
4.1.1.1 The stress-strain relationship shall be established
interest on beam cross-section (see Fig. 2)
through in-grade testing following Test Methods D198 or Test
ε = strain at extreme compression fiber of beam cross-
c Methods D4761, or other established relationships as long as
section (see Fig. 2)
the resulting model meets the criteria established in Section 5.
ε = compression strain at lamstock failure (see Fig. 1)
cult Test lamstock shall be sampled in sufficient quantity from
ε = compression yield strain at lamstock UCS (see Fig. 1)
enough sources to insure that the test results are representative
cy
ε = tensile strain at lamstock failure (see Fig. 1)
of the lamstock population that will be used in the fabrication
tult
ε(y) = strain distribution through beam depth (see Fig. 2) of the beams. Follow-up testing shall be performed annually in
D7199 − 07 (2012)
order to track changes in lamstock properties over time, so that of the lamstock population that will be used in the fabrication
the layup designs may be adjusted accordingly. of the beams. Follow-up testing shall be performed annually in
order to track changes in lamstock properties over time, so that
4.1.1.2 The stress-strain relationship shall be linear in ten-
sion. The stress-strain relationship shall be nonlinear in com- the layup designs may be adjusted accordingly.
pression if compression is the governing failure mode. In this
4.5 Volume Effects:
case, a bilinear approximation is acceptable, and shall be used
4.5.1 The model shall properly account for changes in beam
throughoutthisstandard(seeFig.1).Inthebilinearmodelboth
strength properties as affected by beam size. In conventional
tension and compression MOE shall be permitted to be
glulam, this is achieved by using a volume factor C , which
v
approximated by using the long-span flatwise-bending MOE
was derived from laboratory test data. With adequate
obtained using Test Methods D4761.In Fig. 1, m*E is the
reinforcement, glulams can achieve a reduction or even elimi-
downwardslopeofthecompressionstress-straincurve,defined
nation of volume effects. The model shall properly account for
as the best-fit downward line through the point (UCS, ε )on
cy
this phenomenon. One possible approach to address the vol-
thecompressionstress-straincurve.Thedownwardbest-fitline
ume effect is described in Appendix X1.
shall be permitted to be terminated at the point where the
4.6 Finger-Joint Effects:
ultimate compressive strain ε is approximately 1 %.
cu
4.6.1 Finger joints affect the mechanical properties of lam-
4.1.2 Reinforcement:
stockusedinglulams.Themodelshallaccountfortheseeffects
4.1.2.1 The stress-strain relationship shall be established
on both the mean and variability of the beam mechanical
through material-level testing in accordance with Test Method
properties. One example of how this may be achieved is
D3039/D3039M and D3410/D3410M.
provided in Appendix X1.
4.1.2.2 Nonlinearities in the stress-strain relationship shall
be included in the analysis, if present.
4.7 Laminating Effects:
4.1.2.3 Acceptable stress-strain models for unidirectional
4.7.1 The laminating effects may be predicted by the model
E-glass FRP (GFRP), Aramid, or Carbon FRP (CFRP) in
or else developed outside the model (and applied in the model)
tension are linear-elastic. Acceptable models for hybrid
using an empirical, numerical or analytical approach. One way
E-glass/Carbon composites in tension are linear or bilinear.
to achieve this for a beam subjected to 4-point bending is
Acceptable models for mild steel reinforcement are elastic-
described in Appendix X1.
plastic. Similar models may also apply in compression.
4.8 Str
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