ASTM D198-99

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: D 198 – 99
Standard Test Methods of
Static Tests of Lumber in Structural Sizes
This standard is issued under the fixed designation D 198; 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 (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Numerous evaluations of structural members of solid sawn lumber have been conducted in
accordance with ASTM Test Methods D 198 – 27. While the importance of continued use of a
satisfactory standard should not be underestimated, the original standard (1927) was designed
primarily for sawn material such as solid wood bridge stringers and joists. With the advent of
laminated timbers, wood-plywood composite members, and even reinforced and prestressed timbers,
a procedure adaptable to a wider variety of wood structural members is required.
The present standard expands the original standard to permit its application to wood members of all
types. It provides methods of evaluation under loadings other than flexure in recognition of the
increasing need for improved knowledge of properties under such loadings as tension to reflect the
increasing use of dimensions lumber in the lower chords of trusses. The standard establishes practices
that will permit correlation of results from different sources through the use of a uniform procedure.
Provision is made for varying the procedure to take account of special problems.
1. Scope D 1165 Nomenclature of Domestic Hardwoods and Soft-
woods
1.1 These test methods cover the evaluation of lumber in
D 2395 Test Methods for Specific Gravity of Wood and
structural size by various testing procedures.
Wood-Base Materials
1.2 The test methods appear in the following order:
D 4442 Test Methods for Direct Moisture Content Measure-
ment of Wood and Wood-Base Materials
Sections
E 4 Practices for Force Verification of Testing Machines
Flexure 4 to 11
Compression (Short Column) 12 to 19
E 6 Terminology Relating to Methods of Mechanical Test-
Compression (Long Member) 20 to 27
ing
Tension 28 to 35
E 83 Practice for Verification and Classification of Exten-
Torsion 36 to 43
Shear Modulus 44 to 51
someters
3. Terminology
1.3 Notations and symbols relating to the various testing
3.1 Definitions—See Terminology E 6, Terminology D 9,
procedures are given in Table X1.1.
and Nomenclature D 1165. A few related terms not covered in
1.4 This standard does not purport to address all of the
these standards are as follows:
safety concerns, if any, associated with its use. It is the
3.1.1 span—the total distance between reactions on which a
responsibility of the user of this standard to establish appro-
beam is supported to accommodate a transverse load (Fig. 1).
priate safety and health practices and determine the applica-
3.1.2 shear span—two times the distance between a reac-
bility of regulatory limitations prior to use.
tion and the nearest load point for a symmetrically loaded beam
2. Referenced Documents
(Fig. 1).
2.1 ASTM Standards: 3.1.3 depth of beam—that dimension of the beam which is
perpendicular to the span and parallel to the direction in which
D 9 Terminology Relating to Wood
the load is applied (Fig. 1).
3.1.4 span-depth ratio—the numerical ratio of total span
divided by beam depth.
These methods are under the jurisdiction of ASTM Committee D-7 on Wood
and are the direct responsibility of Subcommittee D07.01 on Fundamental Test
3.1.5 shear span-depth ratio—the numerical ratio of shear
Methods and Properties.
span divided by beam depth.
Current edition approved Dec. 10, 1999. Published April 2000. Originally
published as D 198 – 24. Last previous edition D 198 – 98.
2 3
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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D 198
FIG. 1 Flexure Method
3.1.6 structural wood beam—solid wood, laminated wood, 6.1.6 Data on the effects of chemical or environmental
or composite structural members for which strength or stiff- conditions on mechanical properties.
ness, or both are primary criteria for the intended application
6.1.7 Data on effects of fabrication variables such as depth,
and which usually are used in full length and in cross-sectional
taper, notches, or type of end joint in laminations.
sizes greater than nominal 2 by 2 in. (38 by 38 mm).
6.1.8 Data on relationships between mechanical and physi-
3.1.7 composite wood beam—a laminar construction com-
cal properties.
prising a combination of wood and other simple or complex
6.2 Procedures are described here in sufficient detail to
materials assembled and intimately fixed in relation to each
permit duplication in different laboratories so that comparisons
other so as to use the properties of each to attain specific
of results from different sources will be valid. Special circum-
structural advantage for the whole assembly.
stances may require deviation from some details of these
procedures. Any variations shall be carefully described in the
FLEXURE
report (see Section 11).
4. Scope
7. Apparatus
4.1 This test method covers the determination of the flexural
7.1 Testing Machine— A device that provides (1) a rigid
properties of structural beams made of solid or laminated
frame to support the specimen yet permit its deflection without
wood, or of composite constructions. This test method is
restraint, ( 2) a loading head through which the force is applied
intended primarily for beams of rectangular cross section but is
without high-stress concentrations in the beam, and (3)a
also applicable to beams of round and irregular shapes, such as
force-measuring device that is calibrated to ensure accuracy in
round posts, I-beams, or other special sections.
accordance with Practices E 4.
5. Summary of Test Method
7.2 Support Apparatus:
7.2.1 Reaction Bearing Plates—The beam shall be sup-
5.1 The structural member, usually a straight or a slightly
ported by metal bearing plates to prevent damage to the beam
cambered beam of rectangular cross section, is subjected to a
at the point of contact between beam and reaction support (Fig.
bending moment by supporting it near its ends, at locations
1). The size of the bearing plates may vary with the size and
called reactions, and applying transverse loads symmetrically
shape of the beam. For rectangular beams as large as 12 in.
imposed between these reactions. The beam is deflected at a
(305 mm) deep by 6 in. (152 mm) wide, the recommended size
prescribed rate, and coordinate observations of loads and
of bearing plate is ⁄2 in. (13 mm) thick by 6 in. (152 mm)
deflections are made until rupture occurs.
lengthwise and extending entirely across the width of the
6. Significance and Use beam.
7.2.2 Reaction Bearing Roller—The bearing plates shall be
6.1 The flexural properties established by this test method
supported by either rollers and a fixed knife edge reaction or a
provide:
rocker type-knife edge reaction so that shortening and rotation
6.1.1 Data for use in development of grading rules and
of the beam about the reaction due to deflection will be
specifications.
unrestricted (Fig. 1).
6.1.2 Data for use in development of working stresses for
structural members. 7.2.3 Reaction Bearing Alignment—Provisions shall be
6.1.3 Data on the influence of imperfections on mechanical made at the reaction to allow for initial twist in the length of the
properties of structural members. beam. If the bearing surfaces of the beam at its reactions are
6.1.4 Data on strength properties of different species or not parallel, the beam shall be shimmed or the individual
grades in various structural sizes. bearing plates shall be rotated about an axis parallel to the span
6.1.5 Data for use in checking existing equations or hypoth- to provide full bearing across the width of the specimen (Fig.
eses relating to the structural behavior of beams. 2).
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D 198
curvature equal to two to four times the beam depth for a chord
length at least equal to the depth of the beam. Load shall be
applied to the blocks in such a manner that the blocks may
rotate about an axis perpendicular to the span (Fig. 4).
Provisions such as rotatable bearings or shims shall be made to
ensure full contact between the beam and both loading blocks.
Metal bearing plates and rollers shall be used in conjunction
with one load bearing block to permit beam deflection without
restraint (Fig. 4). The size of these plates and rollers may vary
with the size and shape of the beam, the same as for the
reaction bearing plates. Beams having circular or irregular
cross sections shall have bearing blocks which distribute the
load uniformly to the bearing surface and permit, unrestrained
deflections.
7.3.2 Load Points— The total load on the beam shall be
applied equally at two points equidistant from the reactions.
The two load points will normally be at a distance from their
reaction equal to one third of the span, but for special purposes
other distances may be specified.
NOTE 1—One of the objectives of two-point loading is to subject the
portion of the beam between load points to a uniform bending moment,
free of shear, and with comparatively small loads at the load points. For
example, loads applied at one-third span length from reactions would be
FIG. 2 Example of Bearing Plate, A, Rollers, B, and Reaction-
less than if applied at one-fourth span length from reaction to develop a
Alignment-Rocker, C, for Small Beams
moment of similar magnitude. When loads are applied at the one-third
points the moment distribution of the beam simulates that for loads
uniformly distributed across the span to develop a moment of similar
7.2.4 Lateral Support— Specimens that have a depth-to-
magnitude. If loads are applied at the outer one-fourth points of the span,
width ratio of three or greater are subject to lateral instability
the maximum moment and shear are the same as the maximum moment
during loading, thus requiring lateral support. Support shall be
and shear for the same total load uniformly distributed across the span.
provided at least at points located about half-way between the
7.4 Deflection Apparatus:
reaction and the load point. Additional supports may be used as
7.4.1 General—For either apparent or true modulus of
required. Each support shall allow vertical movement without
elasticity calculations, devices shall be provided by which the
frictional restraint but shall restrict lateral deflection (Fig. 3).
deflection of the neutral axis of the beam at the center of the
7.3 Load Apparatus:
span is measured with respect to either the reaction or between
7.3.1 Load Bearing Blocks—The load shall be applied
cross sections free of shear deflections.
through bearing blocks (Fig. 1) across the full beam width
which are of sufficient thickness to eliminate high-stress 7.4.2 Wire Deflectometer—Deflection may be read directly
concentrations at places of contact between beam and bearing by means of a wire stretched taut between two nails driven into
blocks. The loading surface of the blocks shall have a radius of the neutral axis of the beam directly above the reactions and
FIG. 3 Example of Lateral Support for Long, Deep Beams
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D 198
wood, that is, species, source, etc., whereas composite wooden
beams would be identified by the characteristics of the dissimi-
lar materials and their size and location in the beam.
8.3 Specimen Measurements—The weight and dimensions
as well as moisture content of the specimen shall be accurately
determined before test. Weights and dimensions (length and
cross section) shall be measured to three significant figures.
Sufficient measurements of the cross section shall be made
along the length of the beam to describe the width and depth of
rectangular specimen and to accurately describe the critical
section or sections of nonuniform beams. The physical char-
acteristics of the specimen as described by its density and
moisture content may be determined in accordance with Test
Methods D 2395 and Test Methods D 4442.
8.4 Specimen Description—The inherent imperfections or
intentional modifications of the composition of the beam shall
be fully described by recording the size and location of such
factors as knots, checks, and reinforcements. Size and location
of intentional modifications such as placement of laminations,
glued joints, and reinforcing steel shall be recorded during the
fabrication process. The size and location of imperfections in
FIG. 4 Example of Curved Loading Block, A, Load-Alignment
the interior of any beam must be deduced from those on the
Rocker, B, Roller-Curved Loading Block, C, Load Evener, D, and
Deflection-Measuring Apparatus, E
surface, especially in the case of large sawn members. A sketch
or photographic record shall be made of each face and the ends
showing the size, location, and type of growth characteristics,
extending across a scale attached at the neutral axis of the beam
including slope of grain, knots, distribution of sapwood and
at midspan. Deflections may be read with a telescope or
heartwood, location of pitch pockets, direction of annual rings,
reading glass to magnify the area where the wire crosses the
and such abstract factors as crook, bow, cup, or twist which
scale. When a reading glass is used, a reflective surface placed
might affect the strength of the beam.
adjacent to the scale will help to avoid parallax.
8.5 Rules for Determination of Specimen Length—The
7.4.3 Yoke Deflectometer—A satisfactory device commonly
cross-sectional dimensions of solid wood structural beams and
used for short, small beams or to measure deflection of the
composite wooden beams usually have established sizes,
center of the beam with respect to any point along the neutral
depending upon the manufacturing process and intended use,
axis consists of a lightweight U-shaped yoke suspended
so that no modification of these dimensions is involved. The
between nails driven into the beam at its neutral axis and a dial
length, however, w
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