Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 23 - Wood › Section 2305 - GENERAL DESIGN REQUIREMENTS FOR LATERAL-FORCE-RESISTING SYSTEMS › Subsection 2305.2 - Diaphragm deflection

Current through Register 1525, July 5, 2024
The deflection (Delta) of a blocked wood structural panel
				  diaphragm uniformly fastened throughout with staples is permitted to be
				  calculated by using the following equation. If not uniformly fastened, the
				  constant 0.188 (For SI: 1/1627) in the third term shall be modified
				  accordingly.
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							 image
(Equation 23-1)
For SI:
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							 image
where:
A
= Area of chord cross section, in square
				  inches (mm2).
B
= Diaphragm width, in feet (mm).
E
= Elastic modulus of chords, in pounds
				  per square inch (N/mm2).
e
n = Staple
				  deformation, 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, in feet (mm).
v
= Maximum shear due to design loads in
				  the direction under consideration, in pounds per linear foot (plf)
				  (N/mm).
[Delta] = The calculated deflection, in inches (mm).
[Sigma] (Delta;c
X
) =
				  Sum of individual chord-splice slip values on both sides of the diaphragm, each
				  multiplied by its distance to the nearest support.
TABLE 2305.2(1)
e
n 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 x 2 inches long
60
0.011
80
0.018
100
0.028
120
0.04
140
0.053
160
0.068
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound =
							 4.448 N.
a. Increase
e
n
							 values 20 percent for plywood grades other than Structural I.
b.
							 Load per fastener = maximum shear per foot divided by the number of fasteners
							 per foot at interior panel edges.
c. Decrease
e
n 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)
OTHER
STRUCTURAL I
3-ply
Plywood
4-ply
Plywood
5-ply Plywooda
OSB
3-ply
Plywood
4-ply
Plywood
5-ply Plywooda
OSB
Sheathing
24/0
25,000
32,500
37,500
77,500
32,500
42,500
41,500
77,500
24/16
27,000
35,000
40,500
83,500
35,000
45,500
44,500
83,500
32/16
27,000
35,000
40,500
83,500
35,000
45,500
44,500
83,500
40/20
28,500
37,000
43,000
88,500
37,000
48,000
47,500
88,500
48/24
31,000
40,500
46,500
96,000
40,500
52,500
51,000
96,000
Single Floor
16 o.c.
27,000
35,000
40,500
83,500
35,000
45,500
44,500
83,500
20 o.c.
28,000
36,500
42,000
87,000
36,500
47,500
46,000
87,000
24 o.c.
30,000
39,000
45,000
93,000
39,000
50,500
49,500
93,000
32 o.c.
36,000
47,000
54,000
110,000
47,000
61,000
59,500
110,000
48 o.c.
50,500
65,500
76,000
155,000
65,500
85,000
83,500
155,000
OTHER
STRUCTURAL I
Thickness
(inches)
A-A,
A-C
Marine
All Other
Grades
A-A,
A-C
Marine
All Other
Grades
Sanded Plywood
1/4
24,000
31,000
24,000
31,000
31,000
31,000
11/32
25,500
33,000
25,500
33,000
33,000
33,000
3/8
26,000
34,000
26,000
34,000
34,000
34,000
15/32
38,000
49,500
38,000
49,500
49,500
49,500
1/2
38,500
50,000
38,500
50,000
50,000
50,000
19/32
49,000
63,500
49,000
63,500
63,500
63,500
5/8
49,500
64,500
49,500
64,500
64,500
64,500
23/32
50,500
65,500
50,500
65,500
65,500
65,500
3/4
51,000
66,500
51,000
66,500
66,500
66,500
7/8
52,500
68,500
52,500
68,500
68,500
68,500
1
73,500
95,500
73,500
95,500
95,500
95,500
11/8
75,000
97,500
75,000
97,500
97,500
97,500
For SI: 1 inch = 25.4 mm, 1 pound per inch = 0.1751
							 N/mm.
a. Applies to plywood with five or more layers; for
							 five-ply/three-layer plywood, use values for four ply.