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STRUCTURAL GLUED LAMINATED TIMBER GLULAM 4.127TABLE 4.35 Typical Glulam Column Widths TABLE 4.36 Typical Glulam Column Sizes TABLE 4.37 Column Lay-up Designations Member Lay-up and Desig

4.126 CHAPTER FOUR

Dead load, w d⫽ (10 ⫻ 10) ⫹ 36 ⫽ 136 lb/ft

Total load, w t⫽ 1250 ⫹ 136 ⫽ 1386 lb/ft

Max moment, fully loaded, M⫽ 80 312 lb/ft, at interior reaction

Max moment, unbalanced loading, M u⫽ 69,790 lb/ft at approximately 10 ft from the outer support of the 23.25 ft span

Max shear, fully loaded, V⫽ 16,795 lb at 24 in away from the interior reaction,

in the 23.25 ft span

Max shear, unbalanced loading, V u⫽ 15,544 lb

Max reaction, R⫽ 37,079 lb at interior support

lb / ft is less than the assumed 36 lb / ft—OK.

The allowable compression perpendicular to grain, F c⬜ ⫽ 740 psi Minimum bearing length at interior support⫽ 37,079/(740 ⫻ 5) ⫽ 10 in Revised design shear, V ⫽

16,867 lb at 23 3 ⁄ 8 in away from the face of the interior support ⬍21,038 lb—OK Max deflection: total load on longer span, dead load only on shorter span ⫽ 0.66

as green timbers Glued laminated timber will remain straight and true in section Since glued laminated timber is manufactured with dry lumber, it is alsoless susceptible to checking and splitting, which often occur with green timbers,and it has better fastener holding capacities

man-ufactured in virtually any cross-sectional size and length required However, sincethey are manufactured using dimension lumber, specifying glued laminated timbercolumn in the typical widths as shown by Table 4.35 will ensure maximum effi-ciency of the resource and product availability

The depths of glued laminated timber columns are normally specified in tiples of 11⁄2 in for western species and 13⁄8 in for southern pine Examples ofcolumn sizes are given in Table 4.36 to show the use of typical glued laminatedtimber width and depth size multiples

mul-Another advantage of glued laminated timber is that any length can be supplied,thereby eliminating the need for costly splices to create long-length columns formultistory applications or high open areas Availability of specific cross-sectiondimensions and lengths should be verified with the supplier or manufacturer

STRUCTURAL GLUED LAMINATED TIMBER (GLULAM) 4.127

TABLE 4.35 Typical Glulam Column Widths

TABLE 4.36 Typical Glulam Column Sizes

TABLE 4.37 Column Lay-up Designations

Member Lay-up and Design Stresses. Since compression parallel to grain stressesare distributed uniformly over the cross-section of an axially loaded member, gluedlaminated timber columns are typically manufactured using a single grade of lumberthroughout the depth of the member Examples of lay-up combinations and some

of the associated design stresses for single grade glued laminated timber membersare shown in Table 4.37

Two distinct values are provided for F b and F v, depending on which axis theload is applied to, i.e., parallel to the wide or to the narrow face of the member If

a column is going to be loaded as a combined axial and bending member, it may

be preferable to specify a bending member lay-up such as a V8 DF or V5 SP combination Such members use a graded lumber lay-up throughout thedepth of the member and are more efficient for resisting high bending stresses.For a complete listing of available glued laminated timber layup combinationsfor both members primarily loaded axially or as bending members, refer to Tables4.3 and 4.4

col-umns were designed based on a methodology that required classifying the member

as a short, intermediate, or long column This required a trial-and-error solution

single column design formula regardless of the length-to-depth (l / d ) ratio

previ-ously used to classify columns as short, intermediate, or long This is shown as Eq

(4.18) for a member subjected to concentric axial loads only.

2

1⫹(F / F *) cE c 1⫹(F / F *) cE c (F / F *) cE c

F⬘ ⫽c F * c 再 2c ⫺冪 冋 2c 册 ⫺ c 冎 (4.18)whereF⬘c ⫽allowable compression parallel to grain design value

⫽

F * c tabulated compression parallel to grain design value adjusted for vice conditions (moisture, temperature, load duration) and size effectwhen applicable

ser-F cE⫽critical buckling design value

c ⫽0.8 for sawn lumber, 0.85 for round timber poles and piles, 0.9 forglued laminated timber and structural composite lumber

The critical buckling design value is determined by the well-known Euler umn formula:

col-K E cE ⬘

(L / d ) e where E⬘ ⫽allowable modulus of elasticity adjusted for service conditions (mois-

ture, temperature)

d⫽least unbraced dimension of column

L e⫽effective column length based on unbraced length and end fixity ditions

con-K cE⫽0.300 for products with the coefficient of variation of MOE, COV E⫽0.25, such as visually graded lumber and round timber poles and piles;

0.384 for products with COV E⫽0.15, such as machine-evaluated

lum-ber (MEL); 0.418 for products with COV Eⱕ0.11, such as glued inated timber, machine stress-rated (MSR) lumber, and structuralcomposite lumber

lam-The solution of this equation, which determines the allowable compression allel to grain stress, is based on the physical dimensions of the column, the pub-

par-lished material properties such as E and F c, and several constants The two

con-stants, c and K cE, are material-dependent, with higher values assigned to woodproducts with lower variability such as glued laminated timber, thus resulting inhigher column capacities

Through the laminating process, naturally occurring strength-reducing teristics in the lumber are randomly distributed throughout the member, resulting

charac-in lower variability charac-in mechanical properties for glued lamcharac-inated timber as pared to sawn lumber products For example, the typical coefficient of variation forthe modulus of elasticity of glued laminated timber is about 10%, which is equal

com-to or lower than other comparable wood products Based on the relative

homoge-neity of glued laminated timber and its low variability, the values of c and K cEforglued laminated timber have been established as 0.9 and 0.418, respectively

STRUCTURAL GLUED LAMINATED TIMBER (GLULAM) 4.129

col-umn capacities for two typical glued laminated timber lay-up combinations for aneccentric condition of load application These tables are summarized as follows:

No 2 DF Tables 4.38A–4.38C (eccentric loading)

No 47 SP Tables 4.38D–4.38F (eccentric loading)

All tables have been truncated at an L / d ratio of 50.

For most applications, the No 2 DF and No 47 SP combinations will result inthe most cost-efficient columns These permit the use of all L2 laminations for the

No 2 DF and all No 2 medium grain laminations for the No 47 SP combinations.For those applications requiring greater capacities, the use of a No 5 DF (allL1 laminations) or a No 50 SP (all No 1 dense laminations) are recommended

For additional tables of glulam columns, see EWS publication Y240A, Design of Structural Glued Laminated Timber Columns.12

Since wood columns are typically not truly loaded concentrically, Tables 4.38A–4.38F are provided based on the conservative assumption that the load is appliedwith an eccentricity of 1⁄6 of the least dimension of the column This degree ofeccentricity is considered to be representative of many actual in-service columninstallations such as an end column supporting a beam As such, it provides aconservative solution based on an allowance for some degree of field framing in-consistencies It is recommended that these tables be used for those applicationswhere it is desirable to use a simple tabular solution for preliminary design sizing.For applications with greater degrees of eccentricities or side loads, the designer

is referred to the NDS6for equations that account for these conditions of loading

As with the use of all design tables, it is recommended that the advice of adesign professional be obtained to verify the capacity and applicability of any col-umn size provided in Tables 4.38A–4.38F

Where higher capacities are required and it can be ensured that the loads will

be applied concentrically, the column may be designed in accordance with Eq.(4.18), as shown in the following example

Column Design Example Determine the size of a glued laminated timber column required to support a 45 kip axial floor load (DOL ⫽ 1.0) applied concentrically Assume the length of the column is 15 ft and that it is in a dry use service condition Use a Douglas fir combination No 2 Assume the column is unbraced and that the end conditions are pinned.

Tabulated allowable stresses (see Table 4.4):

F c / / ⫽ 1900 psi

E⫽ 1,700,000 psi Adjusted allowable stresses:

F * c ⫽ 1900 ⫻ 1.0 ⫽ 1900 psi

E ⬘ ⫽ E ⫽ 1,700,000 psi

Try a 6 3 ⁄ 4 in ⫻ 7 1 ⁄ 2 in section: net area ⫽ 6.75 ⫻ 7.5 ⫽ 50.62 in 2

Determine effective length (L e) ⫽ 15(12) ⫻ 1.0 ⫽ 180 in.

Determine slenderness ratio⫽ L e / d⫽ 180/6.75 ⫽ 26.67 ⬍ 50

TABLE 4.38A Glulam Column Design Tables

ECCENTRIC END LOADS FOR DOUGLAS-FIR COMBINATION NO 2 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth

TABLE 4.38A Glulam Column Design Tables

ECCENTRIC END LOADS FOR DOUGLAS-FIR COMBINATION NO 2 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth (Continued)

TABLE 4.38B Glulam Column Design Tables

ECCENTRIC END LOADS FOR DOUGLAS-FIR COMBINATION NO 2 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth.

TABLE 4.38B Glulam Column Design Tables

ECCENTRIC END LOADS FOR DOUGLAS-FIR COMBINATION NO 2 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth (Continued)

TABLE 4.38C Glulam Column Design Tables

ECCENTRIC END LOADS FOR DOUGLAS-FIR COMBINATION NO 2 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth.

TABLE 4.38C Glulam Column Design Tables

ECCENTRIC END LOADS FOR DOUGLAS-FIR COMBINATION NO 2 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth (Continued)

TABLE 4.38D Glulam Column Design Tables

ECCENTRIC END LOADS FOR SOUTHERN PINE COMBINATION NO 47 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth.

TABLE 4.38D Glulam Column Design Tables

ECCENTRIC END LOADS FOR SOUTHERN PINE COMBINATION NO 47 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth (Continued)

TABLE 4.38E Glulam Column Design Tables

ECCENTRIC END LOADS FOR SOUTHERN PINE COMBINATION NO 47 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth.

TABLE 4.38E Glulam Column Design Tables

ECCENTRIC END LOADS FOR SOUTHERN PINE COMBINATION NO 47 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth (Continued)

TABLE 4.38F Glulam Column Design Tables

ECCENTRIC END LOADS FOR SOUTHERN PINE COMBINATION NO 47 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth.

TABLE 4.38F Glulam Column Design Tables

ECCENTRIC END LOADS FOR SOUTHERN PINE COMBINATION NO 47 GLULAM COLUMNS Allowable axial loads (pounds) Side loads and bracket loads are not permitted End loads are limited

to a maximum eccentricity of either 1 / 6 column width or 1 / 6 column depth (Continued)

Determine allowable axial load ⫽F⬘c ⫻ A ⫽ 914.5 ⫻ 50.62 ⫽ 46.3 kips ⬎ 45 kips.

Use a 6 3 ⁄4 in ⫻ 7 1 ⁄2 in No 2 Douglas fir glued laminated timber combination.

4.7.3 Substitution of Glued Laminated Timber Beams for Steel or

Sawn Lumber

Glued laminated timber beams of equal or greater strength and stiffness can often

be substituted for sawn lumber or steel beams Refer to APA Data File S570,

Substitution of Glulam Beams for Steel or Solid-Sawn Lumber,11 for substitutiontables and additional information

4.8 FIELD HANDLING AND INSTALLATION

CONSIDERATIONS

Glued laminated timber beams must be stored properly and handled with care toensure optimum performance When they leave the mill, glued laminated timberbeams are often protected with sealants, primers, or wrappings as specified by thedesigner Care must be taken during loading, unloading, and transporting as well

as in the yard and on the job site to protect these members from damage

4.8.1 Sealants, Primers, and Wrappings

Sealants applied to the ends of beams help guard against moisture penetration andexcessive end grain checking A coat of sealant should be field applied to the ends

of beams (see Fig 4.34) if they are trimmed to length, dapped, or otherwise cutafter leaving the mill

Surface sealants, which can be applied to the top, bottom, and sides of beams,resist dirt and moisture intrusion and help control checking and grain raising Spec-ify a paintable penetrating sealant if beams are to be stained or given a naturalfinish A primer coat also helps protect beams from moisture and soiling and pro-vides a paintable surface for subsequent finishing, if specified See Chapter 9 for afurther discussion of paints and stains

Water-resistant wrappings are often specified to protect beams from moisture,soiling, and surface scratches during transit and job-site storage Because exposure

to sunlight can discolor beams, opaque wrappings are recommended Beams can

be wrapped individually, by bundle, or by load tarping In applications where pearance is especially important, individual wrapping should be left intact until

ap-STRUCTURAL GLUED LAMINATED TIMBER (GLULAM) 4.143

FIGURE 4.34 Glulam sealant at the end of the beam.

Beams

Wrapping

FIGURE 4.35 Glulam handling.

installation to minimize exposure to job-site conditions Individual wrapping should

be completely removed during the erection process to minimize uneven surfacebleaching due to exposure to sunlight

4.8.2 Loading and Unloading

Glued laminated timber beams are commonly loaded and unloaded with forklifts.For greater stability and handling safety, place the sides of the beams, rather thanthe bottoms, flat on the forks (see Fig 4.35) Carrying extremely long beams ontheir sides, however, can cause them to flex excessively To control flex in thesecases, use two or more forklifts, lifting in unison If a crane with slings or chokers

is used to load or unload beams, provide adequate blocking at all beam edgesbetween the sling and the members to protect corners and edges Only fabric slingsshould be used to lift glued laminated timber members Using spreader bars canreduce the likelihood of damage when lifting long beams