Civil Engineering Reference
In-Depth Information
F
i g u r e
3.25 Net diaphragm shears.
Determination of transverse collector/chord forces (see Fig. 3.26):
Starting at grid line 2, the net
shear transferred into the collector at grid line 2B is 28 -23.95 = +4.05 plf and 32.05 - 28 =
+4.05 plf at grid line 2A. Both net shears act toward grid line B, indicating that the collector
is in compression. Starting at grid line A, the force at grid line 2B is equal to
F
2
=
40535
.
()
=
141 7
.
lb compression
B
The net shear on the collector section between grid lines B and C changes from +24.4 plf
to -5.56 plf as diagrammed below the plan. From similar triangles, it can be seen that the
total force on the collector at that section is the sum of the areas of the shear triangles.
F
2
=
149 33
.
-
773
.
=
141 6
.
lb
B
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