Effect of Moisture

Dry service conditions are those in which the moisture content during the use of the member will not be more than 19 percent,

 

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain Ft

Shear parallel to grain Fv

Compression perpendicular to grain Fc

Compression parallel to grain Fc

Modulus

of

Elasticity

E

DOUGLAS FIR-LARCH

Select Structural

1450

1000

95

625

1700

1,900,000

No. 1 and Better

2"-4" thick

1150

775

95

625

1500

1,800,000

No. 1

1000

675

95

625

1450

1,700,000

No. 2

2" & wider

875

575

95

625

1300

1,600,000

WCLIB*

No. 3

500

325

95

625

750

1,400,000

WWPA**

Stud

675

450

95

625

825

1,400,000

Construction

2′-4" thick

1000

650

95

625

1600

1,500,000

Standard

550

375

95

625

1350

1,400,000

Utility

2′-4" wide

275

175

95

625

875

1,300,000

DOUGLAS FIR-LARCH (NORTH)

Select Structural

2"-4" thick

1300

800

95

625

1900

1,900,000

No. 1/No. 2

825

500

95

625

1350

1,600,000

No. 3

2" & wider

475

300

95

625

775

1,400,000

NLGA***

Stud

650

375

95

625

850

1,400,000

Construction

2′-4" thick

950

575

95

625

1750

1,500,000

Standard

525

325

95

625

1400

1,400,000

Utility

2′-4" wide

250

150

95

625

925

1,300,000

* West Coast Lumber Inspection Bureau

** Western Wood Products Association

*** Northeastern Lumber Grading Agency

From National Design Specification for Wood Construction 1991

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain Ft

Shear parallel to grain Fv

Compression perpendicular to grain

Fce

Compression parallel to grain Fc

Modulus

of

Elasticity

E

DOUGLAS FIR-SOUTH

Select Structural

1300

875

90

520

1550

1,400,000

No. 1

2"-4" thick

900

600

90

520

1400

1,300,000

No. 2

825

525

90

520

1300

1,200,000

No. 3

2" & wider

475

300

90

520

750

1,100,000

WWPA

Stud

650

425

90

520

825

1,100,000

Construction

2"-4" thick

925

600

90

520

1550

1,200,000

Standard

525

350

90

520

1300

1,100,000

Utility

2"-4" wide

250

150

90

520

875

1,000,000

EASTERN HEMLOCK-TAMARACK

Select Structural

1250

575

85

555

1200

1,200,000

No. 1

2"-4" thick

775

350

85

555

1000

1,100,000

No. 2

575

275

85

555

825

1,100,000

No. 3

2" & wider

350

150

85

555

475

900,000

NELMA*

Stud

450

200

85

555

525

900,000

NSLB**

Construction

2"-4" thick

675

300

85

555

1050

1,000,000

Standard

375

175

85

555

850

900,000

Utility

2"-4" wide

175

75

85

555

550

800,000

* Northeastern Lumber Manufacturers Association ** Northern Softwood Lumber Bureau

EASTERN SOFTWOODS

Select Structural

1250

575

70

335

1200

1,200,000

No. 1

2"-4" thick

775

350

70

335

1000

1,100,000

No. 2

575

275

70

335

825

1,100,000

No. 3

2" & wider

350

150

70

335

475

900,000

NELMA

Stud

450

200

70

335

525

900,000

NSLB

Construction

2′-4" thick

675

300

70

335

1050

1,000,000

Standard

375

175

70

335

850

900,000

Utility

2′-4" wide

175

75

70

335

550

800,000

EASTERN WHITE PINE

Select Structural

1250

575

70

350

1200

1,200,000

No. 1

2"-4" thick

775

350

70

350

1000

1,100,000

No. 2

575

275

70

350

825

1,100,000

No. 3

2" & wider

350

150

75

350

475

900,000

NELMA

Stud

450

200

70

350

525

900,000

NSLB

Construction

2′-4" thick

675

300

70

350

1050

1,000,000

Standard

375

175

70

350

850

900,000

Utility

2′-4" wide

175

75

70

350

550

800,000

HEM-FIR

Select Structural

1400

900

75

405

1500

1,600,000

No. 1 & Btr

2"-4" thick

1050

700

75

405

1350

1,500,000

No. 1

950

600

75

405

1300

1,500,000

No. 2

2" & wider

850

500

75

405

1250

1,300,000

WCLIB

No. 3

500

300

75

405

725

1,200,000

WWPA

Stud

675

400

75

405

800

1,200,000

Construction

2′-4" thick

975

575

75

405

1500

1,300,000

Standard

550

325

75

405

1300

1,200,000

Utility

2′-4" wide

250

150

75

405

850

1,100,000

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain Ft

Shear parallel to grain Fv

Compression perpendicular to grain

Fcl_

Compression parallel to grain Fc

Modulus

of

Elasticity

E

HEM-FIR (NORTH)

Select Structural

2"-4" thick

1300

775

75

370

1650

1,700,000

No. 1/No. 2

1000

550

75

370

1450

1,600,000

No. 3

2" & wider

575

325

75

370

850

1,400,000

NLGA

Stud

775

425

75

370

925

1,400,000

Construction

2′-4" thick

1150

625

75

370

1750

1,500,000

Standard

625

350

75

370

1500

1,400,000

Utility

2′-4" wide

300

175

75

370

975

1,300,000

MIXED MAPLE

Select Structural

1000

600

100

620

875

1,300,000

No. 1

2"-4" thick

725

425

100

620

700

1,200,000

No. 2

700

425

100

620

550

1,100,000

No. 3

2" & wider

400

250

100

620

325

1,000,000

NELMA

Stud

550

325

100

620

350

1,000,000

Construction

2′-4" thick

800

475

100

620

725

1,100,000

Standard

450

275

100

620

575

1,000,000

Utility

2′-4" wide

225

125

100

620

375

900,000

MIXED OAK

Select Structural

1150

675

85

800

1000

1,100,000

No. 1

2"-4" thick

825

500

85

800

825

1,000,000

No. 2

800

475

85

800

625

900,000

No. 3

2" & wider

475

275

85

800

375

800,000

NELMA

Stud

625

375

85

800

400

800,000

Construction

2′-4" thick

925

550

85

800

850

900,000

Standard

525

300

85

800

650

800,000

Utility

2′-4" wide

250

150

85

800

425

800,000

NORTHERN RED OAK

Select Structural

1400

800

110

885

1150

1,400,000

No. 1

2"-4" thick

1000

575

110

885

925

1,400,000

No. 2

975

575

110

885

725

1,300,000

No. 3

2" & wider

550

325

110

885

425

1,200,000

NELMA

Stud

750

450

110

885

450

1,200,000

Construction

2′-4" thick

1100

650

110

885

975

1,200,000

Standard

625

350

110

885

750

1,100,000

Utility

2′-4" wide

300

175

110

885

500

1,000,000

NORTHERN SPECIES

Select Structural

2"-4" thick

950

450

65

350

1100

1,100,000

No. 1/No. 2

575

275

65

350

825

1,100,000

No. 3

2" & wider

350

150

65

350

475

1,000,000

NLGA

Stud

450

200

65

350

525

1,000,000

Construction

2′-4" thick

675

300

65

350

1050

1,000,000

Standard

375

175

65

350

850

900,000

Utility

2′-4" wide

175

75

65

350

550

900,000

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain Ft

Shear parallel to grain Fv

Compression perpendicular to grain Fc

Compression parallel to grain Fc

Modulus

of

Elasticity

E

NORTHERN WHITE CEDAR

Select Structural

775

450

60

370

750

800,000

No. 1

2"-4" thick

575

325

60

370

600

700,000

No. 2

550

325

60

370

475

700,000

No. 3

2" & wider

325

175

60

370

275

600,000

NELMA

Stud

425

250

60

370

300

600,000

Construction

2′-4" thick

625

375

60

370

625

700,000

Standard

350

200

60

370

475

600,000

Utility

2′-4" wide

175

100

60

370

325

600,000

RED MAPLE

Select Structural

1300

750

105

615

1100

1,700,000

No. 1

2"-4" thick

925

550

105

615

900

1,600,000

No. 2

900

525

105

615

700

1,500,000

No. 3

2" & wider

525

300

105

615

400

1,300,000

NELMA

Stud

700

425

105

615

450

1,300,000

Construction

2′-4" thick

1050

600

105

615

925

1,400,000

Standard

575

325

105

615

725

1,300,000

Utility

2′-4" wide

275

150

105

615

475

1,200,000

RED OAK

Select Structural

1150

675

85

820

1000

1,400,000

No. 1

2"-4" thick

825

500

85

820

825

1,300,000

No. 2

800

475

85

820

625

1,200,000

No. 3

2" & wider

475

275

85

820

375

1,100,000

NELMA

Stud

625

375

85

820

400

1,100,000

Construction

2"-4" thick

925

550

85

820

850

1,200,000

Standard

525

300

85

820

650

1,100,000

Utility

2"-4" wide

250

150

85

820

425

1,000,000

REDWOOD

Clear Structural

1750

1000

145

650

1850

1,400,000

Select Structural

1350

800

80

650

1500

1,400,000

Select Structural, open grain

1100

625

85

425

1100

1,100,000

No. 1

2"-4" thick

975

575

80

650

1200

1,300,000

No. 1, open grain

775

450

80

425

900

1,100,000

No. 2

2" & wider

925

525

80

650

950

1,200,000

No. 2, open grain

725

425

80

425

700

1,000,000

RIS*

No. 3

525

300

80

650

550

1,100,000

No. 3, open grain

425

250

80

425

400

900,000

Stud

575

325

80

425

450

900,000

Construction

2"-4" thick

825

475

80

425

925

900,000

Standard

450

275

80

425

725

900,000

Utility

2"-4" wide

225

125

80

425

475

800,000

* Redwood Inspection Service

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain Ft

Shear parallel to grain Fv

Compression perpendicular to grain

Fcl_

Compression parallel to grain Fc

Modulus

of

Elasticity

E

SPRUCE-PINE-FIR

Select Structural

2"-4" thick

1250

675

70

425

1400

1,500,000

No. 1/No. 2

875

425

70

425

1100

1,400,000

No. 3

2" & wider

500

250

70

425

625

1,200,000

NLGA

Stud

675

325

70

425

675

1,200,000

Construction

2′-4" thick

975

475

70

425

1350

1,300,000

Standard

550

275

70

425

1100

1,200,000

Utility

2′-4" wide

250

125

70

425

725

1,100,000

SPRUCE-PINE-FIR (SOUTH)

Select Structural

1300

575

70

335

1200

1,300,000

No. 1

2"-4" thick

850

400

70

335

1050

1,200,000

No. 2

750

325

70

335

975

1,100,000

NELMA

No. 3

2" & wider

425

200

70

335

550

1,000,000

NSLB

Stud

575

250

70

335

600

1,000,000

WCLIB

Construction

2′-4" thick

850

375

70

335

1200

1,000,000

WWPA

Standard

475

225

70

335

1000

900,000

Utility

2′-4" wide

225

100

70

335

650

900,000

WESTERN CEDARS

Select Structural

1000

600

75

425

1000

1,100,000

No. 1

2"-4" thick

725

425

75

425

825

1,000,000

No. 2

700

425

75

425

650

1,000,000

No. 3

2" & wider

400

250

75

425

375

900,000

WCLIB

Stud

550

325

75

425

400

900,000

WWPA

Construction

2′-4" thick

800

475

75

425

850

900,000

Standard

450

275

75

425

650

800,000

Utility

2′-4" wide

225

125

75

425

425

800,000

WESTERN WOODS

Select Structural

875

400

70

335

1050

1,200,000

No. 1

2"-4" thick

650

300

70

335

925

1,100,000

No. 2

650

275

70

335

875

1,000,000

No. 3

2" & wider

375

175

70

335

500

900,000

WCLIB

Stud

500

225

70

335

550

900,000

WWPA

Construction

2′-4" thick

725

325

70

335

1050

1,000,000

Standard

400

175

70

335

900

900,000

Utility

2′-4" wide

200

75

70

335

600

800,000

Fb

Grades

Width (in.)

Thickness 2 and 3 in.

Thickness 4 in.

Ft

Fc

2, 3, and 4

1.5

1.5

1.5

1.15

Select

5

1.4

1.4

1.4

1.1

Structural

6

1.3

1.3

1.3

1.1

No. 1 and Better

8

1.2

1.3

1.2

1.05

No.

10

1.1

1.2

1.1

1.0

No. 2

12

1.0

1.1

1.0

1.0

No. 3

14 and wider

0.9

1.0

0.9

0.9

Stud

2, 3, and 4

1.1

1.1

1.1

1.05

5 and 6

1.0

1.0

1.0

1.0

Construction and Standard

2, 3, and 4

1.0

1.0

1.0

1.0

Utility

4

1.0

1.0

1.0

1.0

2 and 3

0.4

0.4

0.6

Table 3.3b Flat Use Factor Cfu

Width in.

Thickness (in.)

2 and 3

4

2 and 3

1.0

4

1.1

1.0

5

1.1

1.05

6

1.15

1.05

8

1.15

1.05

10 and wider

1.2

1.1

Type of stress

Fb

Ft

Fv

Fcl_

Fc

E

Cm

0.85*

1.0

0.97

0.67

0.8t

0.9

* When (F)(Cf) s 1150 psi, CM = 1.0. t When (Fc)(Cf) s 750 psi, CM = 1.0.

Table 3.3d Shear Stress Factor CH

Length of split on wide face of 2-in. (nominal) lumber

CH

Length of split on wide face of 3-in. (nominal) and thicker lumber

CH

Size of shake* in 2-in. (nominal) and thicker lumber

CH

No split

2.00

No split

2.00

No shake

2.00

1/2 X wide face

1.67

V2 X narrow face

1.67

1/6 X narrow face

1.67

3/4 X wide face

1.50

3/4 X narrow face

1.50

1/4 X narrow face

1.50

1 X wide face

1.33

1 X narrow face

1.33

1/3 X narrow face

1.33

1-1/2 X wide face or more

1.00

1-1/2 X narrow face or more

1.00

1/2 X narrow face or more

1.00

* Shake is measured at the end between lines enclosing the shake and perpendicular to the loaded surface.

Table 3.4 Base Design Values For Visually Graded Mixed Southern Pine Dimension Lumber

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain

Ft

Shear parallel to grain Fv

Compression perpendicular to grain Fd

Compression parallel to grain Fc

Modulus

of

Elasticity

E

MIXED SOUTHERN PINE

Select Structural

2050

1200

100

565

1800

1,600,000

No. 1

2"-4" thick

1450

875

100

565

1650

1,500,000

No. 2

1300

775

90

565

1650

1,400,000

No. 3

2"-4" wide

750

450

90

565

950

1,200,000

Stud

775

450

90

565

950

1,200,000

SPIB[14]

Construction

2"-4" thick

1000

600

100

565

1700

1,300,000

Standard

550

325

90

565

1450

1,200,000

Utility

4" wide

275

150

90

565

950

1,100,000

Select Structural

1850

1100

90

565

1700

1,600,000

No. 1

2"-4" thick

1300

750

90

565

1550

1,500,000

No. 2

1150

675

90

565

1550

1,400,000

No. 3

5"-6" wide

675

400

90

565

875

1,200,000

Stud

675

400

90

565

875

1,200,000

Select Structural

2"-4" thick

1750

1000

90

565

1600

1,600,000

No. 1

1200

700

90

565

1450

1,500,000

No. 2

8" wide

1050

625

90

565

1450

1,400,000

No. 3

625

375

90

565

850

1,200,000

Select Structural

2"-4" thick

1500

875

90

565

1600

1,600,000

No. 1

1050

600

90

565

1450

1,500,000

No. 2

10" wide

925

550

90

565

1450

1,400,000

No. 3

565

325

90

565

825

1,200,000

Select Structural

2"-4" thick

1400

825

90

565

1550

1,600,000

No. 1

975

575

90

565

1400

1,500,000

No. 2

12" wide

875

525

90

565

1400

1,400,000

No. 3

500

300

90

565

800

1,200,000

Table 3.4a Size Adjustment Factor CF for Southern Pine Including Mixed

For dimension lumber 4 in. thick, 8 in. and wider

For 12 in. and wider lumber

Cf

1.1

0.9

Table 3.4b Wet Service Adjustment Factor CM

Type of stress

Ft

Ft

Fv

Fcx

Ft

E

CM

0.85*

1.0

0.97

0.67

0.8t

0.9

* When (Ft)(CF) ^ 1150 psi, CM = 1.0. t When (Fb) < 750 psi, CM = 1.0.

Table 3.4c Flat Use Factor Cfu

Width (in.)

Thickness (in.)

2 and 3

4

2 and 3

1.0

4

1.1

1.0

5

1.1

1.05

6

1.15

1.05

8

1.15

1.05

10 and wider

1.2

1.1

Table 3.4d Shear Stress Factor CH

Length of split on wide face of 2-in. (nominal) lumber

CH

Length of split on wide face of 3-in. (nominal) and thicker lumber

CH

Size of shake* in 2-in. (nominal) and thicker lumber

CH

No split

2.00

No split

2.00

No shake

2.00

V2 X wide face

1.67

1/2 X narrow face

1.67

1/6 X narrow face

1.67

3/4 X wide face

1.50

3/4 X narrow face

1.50

1/4 narrow face

1.50

1 X wide face

1.33

1 X narrow face

1.33

1/3 narrow face

1.33

I-V2 X wide face or more

1.0

1-1/2 X narrow face or more

1.00

1/2 X narrow face or more

1.00

* Shake is measured at the end between lines enclosing the shake and perpendicular to the loaded surface.

Table 3.5 Base Design Values for Visually Graded Southern Pine Dimension Lumber

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain Ft

Shear parallel to grain Fv

Compression perpendicular to grain

Fc±

Compression parallel to grain Fc

Modulus

of

Elasticity

E

SOUTHERN PINE

Dense Select Structural

3050

1650

100

660

2250

1,900,000

Select Structural

2850

1600

100

565

2100

1,800,000

Non-Dense Select Structural

2650

1350

100

480

1950

1,700,000

No. 1 Dense

2000

1100

100

660

2000

1,800,000

No. 1

2"-4" thick

1850

1050

100

565

1850

1,700,000

No. 1 Non-Dense

1700

900

100

480

1700

1,600,000

No. 2 Dense

2"-4" wide

1700

875

90

660

1850

1,700,000

No. 2

1500

825

90

565

1650

1,600,000

SPIB*

No. 2 Non-Dense

1350

775

90

480

1600

1,400,000

No. 3

850

475

90

565

975

1,400,000

Stud

875

500

90

565

975

1,400,000

Construction

2"-4" thick

1100

625

100

565

1800

1,500,000

Standard

625

350

90

565

1500

1,300,000

Utility

4" wide

300

175

90

565

975

1,300,000

Dense Select Structural

2700

1500

90

660

2150

1,900,000

Select Structural

2550

1400

90

565

2000

1,800,000

Non-Dense Select Structural

2350

1200

90

480

1850

1,700,000

No. 1 Dense

1750

950

90

660

1900

1,800,000

No. 1

No. 1 Non-Dense No. 2 Dense No. 2

No. 2 Non-Dense

No. 3

Stud

2"-4" thick 5"-6" wide

1650

1500

1450

1250

1150

750

775

900

800

775

725

675

425

425

90

90

90

90

90

90

90

565

480

660

565

480

565

565

1750

1600

1750

1600

1500

925

925

1.700.000

1.600.000

1.700.000

1.600.000

1.400.000

1.400.000

1.400.000

Dense Select Structural

2450

1350

90

660

2050

1,900,000

SPIB

Select Structural

2300

1300

90

565

1900

1,800,000

Non-Dense Select Structural

2100

1100

90

480

1750

1,700,000

No. 1 Dense

2"-4" thick

1650

875

90

660

1800

1,800,000

No. 1

1500

825

90

565

1650

1,700,000

No. 1 Non-Dense

8" wide

1350

725

90

480

1550

1,600,000

No. 2 Dense

1400

675

90

660

1700

1,700,000

No. 2

1200

650

90

565

1550

1,600,000

No. 2 Non-Dense

1100

600

90

480

1450

1,400,000

No. 3

700

400

90

565

875

1,400,000

Dense Select Structural

2150

1200

90

660

2000

1,900,000

Select Structural

2050

1100

90

565

1850

1,800,000

Non-Dense Select Structural

1850

950

90

480

1750

1,700,000

No. 1 Dense

2"-4" thick

1450

775

90

660

1750

1,800,000

No. 1

1300

725

90

565

1600

1,700,000

No. 1 Non-Dense

10" wide

1200

650

90

480

1500

1,600,000

No. 2 Dense

1200

625

90

660

1650

1,700,000

No. 2

1050

575

90

565

1500

1,600,000

No. 2 Non-Dense

950

550

90

480

1400

1,400,000

No. 3

600

325

90

565

850

1,400,000

Species and commercial grade

Size

classification

Design values in

pounds per square inch (psi)

Grading

Rules

Agency

Bending

Fb

Tension parallel to grain Ft

Shear parallel to grain Fv

Compression perpendicular to grain Fd

Compression parallel to grain Fc

Modulus

of

Elasticity

E

Dense Select Structural

2050

1100

90

660

1950

1,900,000

Select Structural

1900

1050

90

565

1800

1,800,000

Non-Dense Select Structural

1750

900

90

480

1700

1,700,000

No. 1 Dense

2"-4" thick

1350

725

90

660

1700

1,800,000

No. 1

1250

675

90

565

1600

1,700,000

No. 1 Non-Dense

12" wide4

1150

600

90

480

1500

1,600,000

No. 2 Dense

1150

575

90

660

1600

1,700,000

No. 2

975

550

90

565

1450

1,600,000

No. 2 Non-Dense

900

525

90

480

1350

1,400,000

No. 3

575

325

90

565

825

1,400,000

SOUTHERN PINE (Dry service conditions-

-19% or less moisture content)

Dense Structural 86

2-1/2"-4" thick

2600

1750

155

660

2000

1,800,000

Dense Structural 72

2200

1450

130

660

1650

1,800,000

SPIB

Dense Structural 65

2" & wider

2000

1300

115

660

1500

1,800,000

SOUTHERN PINE (Wet service conditions)

Dense Structural 86

2-1/2"-4" thick

2100

1400

145

440

1300

1,600,000

Dense Structural 72

1750

1200

120

440

1100

1,600,000

SPIB

Dense Structural 65

2-1/2" & wider

1600

1050

110

440

1000

1,600,000

* Southern Pine Inspection Bureau

From National Design Specification for Wood Construction 1991

Type of stress

Fb

Ft

Fv

Fd

Fc

E

Cm

1.00

1.0

1.00

0.67

0.91

1.00

Table 3.5b Shear Stress Factor CH

Length of split on wide face of 5-in. (nominal) and thicker lumber

CH

Size of shake* in 5-in. (nominal) and thicker lumber

CH

No split

2.00

No shake

2.00

V2 X narrow width

1.67

1/6 X narrow face

1.67

3/4 X narrow width

1.50

1/4 X narrow face

1.50

1 X narrow width

1.33

1/3 X narrow face

1.33

11/2 X narrow width

1.00

V2 X narrow face or more

1.00

* Shake is measured at the end between lines enclosing the shake and perpendicular to the loaded surface.

Table 3.6 Design Values for Visually Graded Decking

Design values in pounds per

Species and

square inches

Size classification

Fb

Fi

E

commercial grade

Douglas Fir-Larch

Select Dex

2-4 in. thick

1750.0

625.0

1,800,000

Commercial Dex

6-8 in. wide

1450.0

625.0

1,700,000

Hem-Fir

Select Dex

2-4 in. thick

1400.0

405.0

1,500,000

Commercial Dex

6-8 in. wide

1150.0

405.0

1,400,000

Redwood

Select, Close Grain

2 in. thick

1850.0

1,400,000

Select

1450.0

1,100,000

Commercial

6 in. and wider

1200.0

1,000,000

Deck heart and

Deck common

2 in. thick, 4 in. wide

400.0

420.0

900,000

2 in. thick, 6 in. wide

700.0

420.0

900,000

Southern Pine (Dry service conditions—19% or less moisture content)

Dense Standard

2-4 in. thick

2000.0

660.0

1,800,000

Dense Select

1650.0

660.0

1,600,000

Select

1400.0

565.0

1,600,000

Dense Commercial

1650.0

660.0

1,600,000

Commercial

2 in. and wider

1400.0

565.0

1,600,000

Southern Pine (Wet service conditions)

Dense Standard

21/2-4 in. thick

1600.0

440.0

1,600,000

Dense Select

1350.0

440.0

1,400,000

Select

1150.0

375.0

1,400,000

Dense Commercial

1350.0

440.0

1,400,000

Commercial

2 in. and wider

1150.0

375.0

1,400,000

From National Design Specification for Wood Construction 1991

 

Подпись: Copyright © Marcel Dekker, Inc. All rights reserved.

Type of stress

Fb

fcL

E

Cm

0.85t

0.67

0.9

* For Southern Pine use tabulated design values for wet service conditions without further adjustment.

t When (Fb)(CF) s 1150 psi, CM = 1.0.

regardless of the moisture content of the member at the time of its manufacture. The design values (allowable design stresses) for lumber are applicable to members that are used under dry service conditions, such as in most covered structures. For lumber used under conditions where the moisture content of the wood will ex­ceed 19 percent for an extended period of time, the design values of the member shall be multiplied by the wet service condition factor CM, as is specified by the National Design Specification for Wood Construction (NDS). The wet service factor (<1.0) is used to decrease the allowable stresses to account for the weakening of the member due to the increase in its moisture content. An ex­ample of the wet service factor is given in Table 3.3c.

Подпись: Density Подпись: 62.4 Подпись: G 1 + G(0.009)(m.c.) Подпись: 1 + 100

Also, moisture content adds additional weight to the lumber. NDS specifies that the following formula shall be used to deter­mine the density (in lb./ft3) of wood.

where

G = specific gravity of wood based on weight and volume when oven-dry m. c. = moisture content of wood, %