Civil Engineering Reference
In-Depth Information
Second floor:
V
r
= factored shear force at roof level
V
3
= factored shear force at third-loor level
hh
3
=
+
h
wall
roof
hh
2
=
+
h
floor
wall
L
= length of wall segment
VV
L
+
r
3
v
=
unit shearinwallatsecondfloor
x
= distance from center of bearing to center of hold-down anchor
∑
Vh
(
++ ±
hVh
)
(
load factor
)
M
r
3
2
32
DL
F
=
OT
/
x
First floor:
V
r
= factored shear force at roof level
V
3
= factored shear force at third-loor level
V
2
= factored shear force at second-loor level
hh
3
=
+
h
wall
roof
hh
2
=
+
h
wall
floor
hh
1
=
+
h
floor
wall
L
= length of wall segment
VVV
L
++
3
v
=
r
2
unit shearinwallatfirst floor
x
= distance from center of bearing to center of hold-down anchor
∑
Vh
(
++ +
hh Vh
)
(
+
hVh
)
+
±
(
load factor
)
M
r
3
2
1
32
1
2
1
DL
F
=
OT
/
x
For sloped roofs, the distance to the center of gravity (C.G.) of the roof is added for
seismic loading.
The diaphragm shears occur at the roof or floor sheathing and are then trans-
ferred down through the roof or floor framing into the top of the wall. Per code and
accepted engineering practice, all the forces from the diaphragm and upper walls,
including overturning forces, must be transposed to the top of the wall in accordance
with the basic rules of statics, as shown in Fig. 9.12. Assume that the tension overturn-
ing force from the wall above is equal to 2400 lb, and the horizontal shear force applied
to the wall is equal to 4000 lb, as shown in Fig. 9.12. The design is controlled by wind.
Determine the tension forces only.
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