| 1. StrucJoist joists are permitted to use the
LVL flange grades and allowable stresses in Table 1. The last letter in the joist series
designation indicates the flange grade, except for AA flange grade joists, which have no
letter designation. 2. Design properties for joists
with alternative flange grades are determined as follows. The allowable shear, reactions
and K in Table 3 are the same for flange grades A, B, C and E. Similarly, the allowable
shear, reactions and K in Table 4 are the same for flange grades F, G and H. Factor
allowable moments by Ft(desired grade) / Ft (tabulated grade) and factor El by E(desired
grade) / E(tabulated grade).
3. Both bending and shear deformations shall be considered
when computing deflections. For bending deformation, use standard engineering formulae.
For shear deformation use 8 x bending moment/K.
EXAMPLES - Deflection for a simple span joist.
Deflection (Uniform Load) = 5wL6/384El + 8M/K =
5wL4/384El + wl2/K
Deflection (Point Load ) = PL3/48El + 8M/K = PL3/48El
+ 2PL/K
where:
w = uniform load in pounds per lineal inch
P = point load in pounds
L = effective span in inches
4. The allowable moment, shear and reactions are for normal
duration loading and shall be adjusted in accordance with the code for load duration.
Allowable reactions are applicable with the bearing lengths noted. Straight line
interpolation of allowable reactions between bearing lengths is permitted.
5. 9-1/4" and 11-1/4" SJ-15, SJ-25, SJ-35 joists
are permitted, except for 9-1/4" SJ-35 joists with flange grades F, G and H. Factor
9-1/2" and 11-7/8" design properties for the corresponding joist series as noted
below to obtain 9-1/4" and 11-1/4" design properties.
| Depth Conversion |
Flange Grades |
Shear, K & 4"
Exterior Reactions |
1-3/4" Exterior &
3-1/2" Interior Reactions |
Moment |
El |
| 9-1/4" Factors |
AA, A, B, C & E F,G & H |
0.974 0.990
|
1.000 1.000
|
0.963 0.963
|
0.933 0.933
|
| 11-/4" Factors |
AA, A, B, C & E F, G & H |
0.947 0.991
|
1.000 1.000
|
0.937 0.937
|
0.878 0.878
|
6. Allowable reactions are for joists with web stiffeners
installed per detail F16 of Figure 5. The values are also applicable to 5-1/4 inch
interior bearings without web stiffeners.
7. The joists noted require 5 inch exterior bearings to
develop 1550 pound capacity. |
