Civil Engineering Reference
In-Depth Information
and are equal to the basic diaphragm shear. The net shears in the transfer diaphragm
are calculated as follows:
Location (Grid Line)
Net Shear
1 from A to B
v
= +300 + (67.5) = +367.5 plf
2 from A to B (left side)
v
= +240 + (67.5) = +307.5 plf
2 from A to B (right side)
+300 plf
1 from B to C
v
= +300 - (270) = +30 plf
2 from B to C
v
= +240 - (270) = -30 plf
The diaphragm nailing patterns can be determined from the calculated net diaphragm
shears.
Determination of right transfer diaphragm shears (see Fig. 4.2):
Disrupted chord force = 10,062.5 lb at grid line 3B
V
D
10 062 510
50
,
. ()
=
-
2012 5
.
A
TD
V
=
=
2012 5
.
lb
v
=
=-
134 2
.plf
A
A
15
The reaction at A is acting to the right. Applying the remaining shears on the sheathing
element shows that the transfer diaphragm shear is negative.
10 062 540
50
,
. ()
V
D
8050
15
C
TD
V
=
=
8050
lb
v
=
=
=+
5
36 .plf
C
C
The reaction at C is also acting to the left. Applying the remaining shears on the sheathing
element shows that the transfer diaphragm shear is positive.
Determination of diaphragm net shears (see Fig. 4.2):
Following the same procedure as for
the left transfer diaphragm, the net shears in the transfer diaphragm are calculated as
follows:
Location (Grid Line)
Net Shear
3 from A to B (right side)
v
= +160 - (134.2) = +25.8 plf
3 from A to B (left side)
+200 plf
3 from B to C
v
= +160 + (536.7) = +696.7 plf
4 from A to B (left side)
v
= +100 - (134.2) = -34.2 plf
4 from B to C (left side)
v
= +100 + (536.7) = +636.7 plf
4 from A to C (right side)
+100 plf
Determination of longitudinal collector/chord forces (see Fig. 4.3):
The collector/chord forces
are determined by adding or subtracting the shears on each side of the collector or chord
member based on their direction relative to each other. The resulting shears at each end
of the member are averaged and multiplied by the member length; or simply take the
area of the resulting shear diagram along the length of the member being analyzed. It is
important that all the force diagrams are calculated and placed on the plan, as a visual
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