Reprogramación de fibroblastos embrionarios bovinos

9.1 General 58

9.2 Reference Design Values 58 9.3 Adjustment of Reference Design

Values 59

9.4 Design Considerations 60

Table 9.3.1 Applicability of Adjustment Factors for

Wood Structural Panels ... 59 Table 9.3.4 Panel Size Factor, C_s ... 60

9

Copyright © American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized.

9.1 General

9.1.1 Scope

Chapter 9 applies to engineering design with the following wood structural panels: plywood, oriented strand board, and composite panels. Basic requirements are provided in this Specification. Design procedures and other information provided herein apply only to wood structural panels complying with the require-ments specified in this Chapter.

9.1.2 Identification

9.1.2.1 When design procedures and other informa-tion herein are used, the wood structural panel shall be identified for grade and glue type by the trademarks of an approved testing and grading agency.

9.1.2.2 Wood structural panels shall be specified by span rating, nominal thickness, exposure rating, and grade.

9.1.3 Definitions

9.1.3.1 The term “wood structural panel” refers to a wood-based panel product bonded with a waterproof

adhesive. Included under this designation are plywood, oriented strand board (OSB) and composite panels.

These panel products meet the requirements of USDOC PS 1 or PS 2 and are intended for structural use in resi-dential, commercial, and industrial applications.

9.1.3.2 The term “composite panel” refers to a wood structural panel comprised of wood veneer and reconstituted wood-based material and bonded with waterproof adhesive.

9.1.3.3 The term “oriented strand board” refers to a mat-formed wood structural panel comprised of thin rectangular wood strands arranged in cross-aligned lay-ers with surface laylay-ers normally arranged in the long panel direction and bonded with waterproof adhesive.

9.1.3.4 The term “plywood” refers to a wood struc-tural panel comprised of plies of wood veneer arranged in cross-aligned layers. The plies are bonded with an adhesive that cures on application of heat and pressure.

9.1.4 Service Conditions

9.1.4.1 Reference design values reflect dry service conditions, where the moisture content in service is less than 16%, as in most covered structures.

9.2 Reference Design Values

9.2.1 Panel Stiffness and Strength

9.2.1.1 Reference panel stiffness and strength de-sign values (the product of material and section proper-ties) shall be obtained from an approved source.

9.2.1.2 Due to the orthotropic nature of panels, ref-erence design values shall be provided for the primary and secondary strength axes. The appropriate reference design values shall be applied when designing for each panel orientation. When forces act at an angle to the principal axes of the panel, the capacity of the panel at the angle shall be calculated by adjusting the reference design values for the principal axes using principles of engineering mechanics.

9.2.2 Strength and Elastic Properties

Where required, strength and elastic parameters shall be calculated from reference strength and stiffness

design values, respectively, on the basis of tabulated design section properties.

9.2.3 Design Thickness

Nominal thickness shall be used in design calcula-tions. The relationships between span ratings and nominal thicknesses are provided with associated refer-ence design values.

9.2.4 Design Section Properties

Design section properties shall be assigned on the basis of span rating or design thickness and are pro-vided on a per-foot-of-panel-width basis.

WOOD STRUCTURAL PANELS

9

9.3 Adjustment of Reference Design Values

9.3.1 General

Reference design values shall be multiplied by the adjustment factors specified in Table 9.3.1 to determine adjusted design values.

9.3.2 Load Duration Factor, C

_D

(ASD Only)

All reference strength design values (FbS, FtA, Fvtv, Fs(Ib/Q), FcA) shall be multiplied by load duration fac-tors, CD, as specified in 2.3.2.

9.3.3 Wet Service Factor, C

_M

, and Temperature Factor, C

_t

Reference design values for wood structural panels are applicable to dry service conditions as specified in 9.1.4 where CM = 1.0 and Ct = 1.0. When the service conditions differ from the specified conditions, adjust-ments for high moisture and/or high temperature shall be based on information from an approved source.

Table 9.3.1 Applicability of Adjustment Factors for Wood Structural Panels

ASD

only ASD and LRFD LRFD only

Format Conversion Factor Resistance Factor

Load Duration Factor Wet Service Factor Temperature Factor Panel Size Factor

K

F



Time Effect Factor

F

b

S

^'

= F

b

S x C

D

C

M

C

t

C

s

2.54 0.85 

F

t

A

^'

= F

t

A x C

D

C

M

C

t

C

s

2.70 0.80 

F

v

t

v'

= F

v

t

v

x C

D

C

M

C

t

- 2.88 0.75 

F

s

(Ib/Q)

^'

= F

s

(Ib/Q) x C

D

C

M

C

t

- 2.88 0.75  F

c

A

^'

= F

c

A x C

D

C

M

C

t

- 2.40 0.90  F

c'

= F

c

x - C

M

C

t

- 1.67 0.90 - EI

^'

= EI x - C

M

C

t

- - - - EA

^'

= EA x - C

M

C

t

- - - - G

v

t

v'

= G

v

t

v

x - C

M

C

t

- - - -

Copyright © American Wood Council. Downloaded/printed pursuant to License Agreement. No reproduction or transfer authorized.

9.3.4 Panel Size Factor, C

_s

Reference bending and tension design values (FbS and FtA) for wood structural panels are applicable to panels that are 24" or greater in width (i.e., dimension perpendicular to the applied stress). For panels less than 24" in width, reference bending and tension design val-ues shall be multiplied by the panel size factor, Cs, specified in Table 9.3.4.

.

Table 9.3.4 Panel Size Factor, C_s

Panel Strip Width, w Cs

w  " 0.5

 "  w  24" (8 + w) / 32 w  24" 1.0

9.3.5 Format Conversion Factor, K

_F

(LRFD Only)

For LRFD, reference design values shall be multi-plied by the format conversion factor, KF, specified in Table 9.3.1.

9.3.6 Resistance Factor,  (LRFD Only)

For LRFD, reference design values shall be multi-plied by the resistance factor, , specified in Table 9.3.1.

9.3.7 Time Effect Factor,  (LRFD Only)

For LRFD, reference design values shall be multi-plied by the time effect factor, , specified in Appendix N.3.3.

9.4 Design Considerations

9.4.1 Flatwise Bending

Wood structural panels shall be designed for flex-ure by checking bending moment, shear, and deflection.

Adjusted planar shear shall be used as the shear resis-tance in checking the shear for panels in flatwise bend-ing. Appropriate beam equations shall be used with the design spans as defined below.

(a) Bending moment-distance between center-line of supports.

(b) Shear-clear span.

(c) Deflection-clear span plus the support width factor. For 2" nominal and 4" nominal framing, the support width factor is equal to 0.25" and 0.625", respectively.

9.4.2 Tension in the Plane of the Panel

When wood structural panels are loaded in axial tension, the orientation of the primary strength axis of the panel with respect to the direction of loading, shall be considered in determining adjusted tensile capacity.

9.4.3 Compression in the Plane of the Panel

When wood structural panels are loaded in axial compression, the orientation of the primary strength axis of the panel with respect to the direction of load-ing, shall be considered in determining the adjusted compressive capacity. In addition, panels shall be de-signed to prevent buckling.

9.4.4 Planar (Rolling) Shear

The adjusted planar (rolling) shear shall be used in design when the shear force is applied in the plane of wood structural panels.

9.4.5 Through-the-Thickness Shear

The adjusted through-the-thickness shear shall be used in design when the shear force is applied through-the-thickness of wood structural panels.

9.4.6 Bearing

The adjusted bearing design value of wood struc-tural panels shall be used in design when the load is applied perpendicular to the panel face.

MECHANICAL

In document Lic. Camila Vázquez Echegaray (página 68-78)