Civil Engineering Reference
In-Depth Information
80
20
TD
1
==,
4
blocked herefore OK
,
50
15
TD
2
==.
333
,
blocked herefore OK
,
90
25
TD
3
=
TD
4
=
TD
5
=
= .,
36
blocked herefore OK
,
The disrupted chord at grid line 4D must be embedded into transfer diaphragm
TD2. Since the transfer diaphragm cannot extend to grid line A, it must be supported
by the struts and collectors that are embedded into transfer diaphragms TD1 and TD3
at grid line B. Before transfer diaphragms TD1 and TD3 can be analyzed, the forces in
the collectors above and below the opening must be determined.
Diaphragm 1:
Panel shear forces at the opening (see Fig. 8.9): The section above the
opening is broken down into two sections. The sections are assumed to have a point of
contraflexure at midlength as outlined in Chap. 5. The total shear at grid line 5 is −5000 lb
acting downward, as determined by placing the sheathing element symbols adjacent
to the transfer diaphragm as shown in the free-body diagram at the upper right of the
figure, in accordance with the sign convention legend. Therefore, the shear acting on the
right edge of the sections above and below the opening is acting in the upward direction,
also shown in the figure. Applying the sheathing element symbols at all edges of the
sections, determine if the unit shears are positive or negative. Distribution of this force
into the panels at this location is in accordance with the depth of the sections above and
below the opening.
VD
=
−
5000 10
60
()
5
AA
−
.
2
V
=
=−
833 33
.
lb sh
earappliedtouppersection
upper
D
V
D
=
−
833 33
10
.
upper
v
=
=−
83 33
.
plfunits
hear of uppersection
upper
AA
− .
2
VD
D
=
−
5000 50
60
()
5
BE
−
4166 67
.
ar appliedtolower section
V
=
=−
lb she
lower
V
D
=
−
4166 67
50
.
v
=
lower
BE
=−
83 33
.
plfunitsh
earoflower section
lower
−
Starting at grid line 5 at the upper panel, summing to the left (see free body in Fig. 8.9):
V
5
=
833 33
.
lbactingupward
VVVwx
==−=
833 33
.
−
123 12 5
(
.)
left
4
5
=−
704 2
.
lb a
ctingupwardonleftedgetobalance verticalforcestozero
V
D
704 2
10
.
left
v
=
=
=+
70 42
.
plfunitshear at left
edgeofsection
4
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