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// CODE SNIPPET

2305.2 Diaphragm Deflection

Building Code of the Department of Personnel & Administration/Office of the State Architect (DPA/OSA) > 23 Wood > 2305 General Design Requirements for Lateral Force-Resisting Systems > 2305.2 Diaphragm Deflection
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The deflection of wood-frame diaphragms shall be determined in accordance with AWC SDPWS. The deflection (Δdia) of a blocked wood structural panel diaphragm uniformly fastened throughout with staples is permitted to be calculated in accordance with Equation 23-1. If not uniformly fastened, the constant 0.188 (For SI: 1/1627) in the third term shall be modified by an approved method.

Δdia = 5vL3/8EAW + vL/4Gt + 0.188Len + Σ(xΔc)/2W (Equation 23-1)

For SI: Δdia = 0.052vL3/EAW + vL/4Gt + Len/1627 + Σ(xΔc)/2W
where:
A = Area of chord cross section, in square inches (mm2).
E = Modulus of elasticity of diaphragm chords, in pounds per square inch (N/mm2).
en = Staple slip, in inches (mm) [see Table 2305.2(1)].
Gt = Panel rigidity through the thickness, in pounds per inch (N/mm) of panel width or depth [see Table 2305.2(2)].
L = Diaphragm length (dimension perpendicular to the direction of the applied load), in feet (mm).
v = Induced unit shear in pounds per linear foot (plf) (N/mm).
W = Diaphragm width [in the direction of applied force, in feet (mm)].
x = Distance from chord splice to nearest support, in feet (mm).
Δc = Diaphragm chord splice slip at the induced unit shear, in inches (mm).
Δdia = Maximum mid-span diaphragm deflection determined by elastic analysis, in inches (mm).
TABLE 2305.2(1)
en VALUES (inches) FOR USE IN CALCULATING DIAPHRAGM AND SHEAR WALL DEFLECTION DUE TO FASTENER SLIP (Structural I)a, c
LOAD PER FASTENERb
(pounds)
FASTENER DESIGNATIONS
14-Ga staple × 2 inches long
600.011
800.018
1000.028
1200.04
1400.053
1600.068

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 4.448 N.

  1. Increase en values 20 percent for plywood grades other than Structural I.
  2. Load per fastener = maximum shear per foot divided by the number of fasteners per foot at interior panel edges.
  3. Decrease en values 50 percent for seasoned lumber (moisture content < 19 percent).
TABLE 2305.2(2)
VALUES OF Gt FOR USE IN CALCULATING DEFLECTION OF WOOD STRUCTURAL PANEL SHEAR WALLS AND DIAPHRAGMS
PANEL
TYPE
SPAN
RATING
VALUES OF Gt (lb/in. panel depth or width)
Structural SheathingStructural I
PlywoodOSBPlywoodOSB
3-ply4-ply5-plya3-ply4-ply5-plya
Sheathing24/025,00032,50037,50077,50032,50042,50041,50077,500
24/1627,00035,00040,50083,50035,00045,50044,50083,500
32/1627,00035,00040,50083,50035,00045,50044,50083,500
40/2028,50037,00043,00088,50037,00048,00047,50088,500
48/2431,00040,50046,50096,00040,50052,50051,00096,000
Single Floor16 o.c.27,00035,00040,50083,50035,00045,50044,50083,500
20 o.c.28,00036,50042,00087,00036,50047,50046,00087,000
24 o.c.30,00039,00045,00093,00039,00050,50049,50093,000
32 o.c.36,00047,00054,000110,00047,00061,00059,500110,000
48 o.c.50,50065,50076,000155,00065,50085,00083,500155,000
Structural SheathingStructural I
Thickness
(in.)
A-A,
A-C
MarineAll Other
Grades
A-A,
A-C
MarineAll Other
Grades
Sanded Plywood1/424,00031,00024,00031,00031,00031,000
11/3225,50033,00025,50033,00033,00033,000
3/826,00034,00026,00034,00034,00034,000
15/3238,00049,50038,00049,50049,50049,500
1/238,50050,00038,50050,00050,00050,000
19/3249,00063,50049,00063,50063,50063,500
5/849,50064,50049,50064,50064,50064,500
23/3250,50065,50050,50065,50065,50065,500
3/451,00066,50051,00066,50066,50066,500
7/852,50068,50052,50068,50068,50068,500
173,50095,50073,50095,50095,50095,500
11/875,00097,50075,00097,50097,50097,500

For SI: 1 inch = 25.4 mm, 1 pound/inch = 0.1751 N/mm.

  1. 5-ply applies to plywood with five or more layers. For 5-ply plywood with three layers, use values for 4-ply panels.

Related Code Sections


2305.2 Wood, Diaphragm Deflection
The deflection of wood-frame diaphragms shall be determined in accordance with AWC SDPWS. The deflection (Δ dia ) of a blocked wood structural panel ...
Building Code of the Department of Personnel & Administration/Office of the State Architect (DPA/OSA) > 23 Wood > 2305 General Design Requirements for Lateral Force-Resisting Systems > 2305.2 Diaphragm Deflection
2305.2 Wood, Diaphragm Deflection
The deflection of wood-frame diaphragms shall be determined in accordance with AWC SDPWS. The deflection (Δ) of a blocked wood structural panel ...
Building Code of the Department of Personnel & Administration/Office of the State Architect (DPA/OSA) > 23 Wood > 2305 General Design Requirements for Lateral Force-Resisting Systems > 2305.2 Diaphragm Deflection
1604.3.1 Structural Design, Deflections
The deflections of structural members shall not exceed the more restrictive of the limitations of Sections 1604.3.2 through 1604.3.5 ...
Building Code of the Department of Personnel & Administration/Office of the State Architect (DPA/OSA) > 16 Structural Design > 1604 General Design Requirements > 1604.3 Serviceability > 1604.3.1 Deflections
1604.3.1 Structural Design, Deflections
The deflections of structural members shall not exceed the more restrictive of the limitations of Sections 1604.3.2 through 1604.3.5 ...
Building Code of the Department of Personnel & Administration/Office of the State Architect (DPA/OSA) > 16 Structural Design > 1604 General Design Requirements > 1604.3 Serviceability > 1604.3.1 Deflections
1709.3.2 Special Inspections and Tests, Deflection
The deflection of structural members under the design load shall not exceed the limitations in Section 1604.3 ...
Building Code of the Department of Personnel & Administration/Office of the State Architect (DPA/OSA) > 17 Special Inspections and Tests > 1709 Preconstruction Load Tests > 1709.3 Load Test Procedures Not Specified > 1709.3.2 Deflection
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