Building Design and Construction Handbook - Merritt - Ventech!

11.30 SECTION ELEVEN
Slenderness Coefficient. C s may be selected from Table 11.8, or calculated from
Eq. (11.6). Linear interpolation is permitted within the table.
TABLE 11.8 Slenderness Coefficients C s
h/t
2
� � ��
h/t e1 Cs � 1.20 � 5.75 � 1.5 � � 1.0 (11.6)
300 e2 11.10.3 Eccentrically Loaded Shear Walls
‘‘Building Code Requirements for Engineered Brick Masonry’’ also provides a basis
for design of eccentrically loaded shear walls. The standard requires that, in a
nonreinforced shear wall, the virtual eccentricity e L about the principal axis normal
to the length L of the wall not exceed an amount that will produce tension. In a
nonreinforced shear wall subject to bending about both principal axes, e tL � e Lt
should not exceed tL/3, where e t � virtual eccentricity about the principal axis
normal to the thickness t of the shear wall. Where the virtual eccentricity exceeds
the preceding limits, shear walls should be designed as reinforced or partly reinforced
walls.
Consequently, for a planar wall the virtual eccentricity e L, which is found by
dividing the overturning moment about an axis normal to the plane of the wall by
the axial load, should not exceed L/6. In theory, any virtual eccentricity exceeding
L/6 for planar shear wall will result in development of tensile stresses. If, however,
intersecting walls form resisting flanges, the classic approach may be used where
the bending stress Mc/I is combined with the axial stress P/A. If the bending stress
exceeds the axial stress, then tensile stresses are present. (Note that some building
codes require a safety factor against overturning. It is usually 1.5 for nonreinforced
walls. But the codes state that, if the walls are vertically reinforced to resist tension,
the safety factor does not apply.)
e 1/e 2
�1 � 3 ⁄4 � 1 ⁄2 � 1 ⁄4 0 1 ⁄4
1 ⁄2
3 ⁄4 1
5.0 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
7.5 1.00 1.00 1.00 1.00 1.00 0.98 0.96 0.93 0.90
10.0 1.00 0.99 0.98 0.96 0.93 0.91 0.88 0.84 0.80
12.5 0.95 0.94 0.92 0.90 0.87 0.83 0.79 0.75 0.70
15.0 0.90 0.88 0.86 0.83 0.80 0.76 0.71 0.66 0.60
17.5 0.85 0.83 0.81 0.77 0.73 0.69 0.63 0.57 0.50
20.0 0.80 0.78 0.75 0.71 0.67 0.61 0.55 0.48 0.40
22.5 0.75 0.73 0.69 0.65 0.60 0.54 0.47 0.39
25.0 0.70 0.67 0.64 0.59 0.53 0.47 0.39
27.5 0.65 0.62 0.58 0.53 0.47 0.39
30.0 0.60 0.57 0.52 0.47 0.40
32.5 0.55 0.52 0.47 0.41
35.0 0.50 0.46 0.41
37.5 0.45 0.41
40.0 0.40