Civil Engineering Reference
In-Depth Information
diaphragm shears across the opening. A strut supports the left end of the skylight and
connects the shear walls along grid line 1. The strut acts as part of the boundary member
along the line of lateral force resistance. The sections above and below the opening are
designated as sections A and B, respectively. Since the sections act as cantilevers, the
members at grid lines B and C from 1 to 2 are chord members for the sections, which
are discontinuous. The disrupted chords are embedded into transfer diaphragm TD1
where their forces are then transferred to the exterior wall lines at A and C. The aspect
ratio of TD1 is 3.73 : 1; therefore the transfer diaphragm must be blocked. The 200 plf
uniform load applied to the diaphragm is caused by wind. The notched area is enclosed
by a wall at grid line 1 from B to C. The wind load is split into windward and leeward
pressures between lines 1 and 2.
Construction of the basic shear diagram (see Fig. 4.12):
VV
wL
1
200 150
2
(
)
== =
=
15 000
,
lbshear at each support wall
4
2
The depth of the diaphragm between grid lines 1 and 2 is equal to 22 ft plus 16 ft.
15 000
22
,
v
1
=
=+
394 7
.plf unit diaphragmshearatgrid line1
+
16
Section A: apply windward wind pressures.
Rv D
1
=
=
394 722
.( )
=
8683 4
.
lb
diaph ectA
V
2
=
8683 4
.
-
123 16
(
)
=
6716
lbshear at grid linee ection A eft
2,
(
)
6716
22
v
2
=
= +
305 3
.plf unit diaphragmshear attgrid lineleft
2(
)
Section B: apply leeward wind pressures.
Rv D
1
=
=
394 716
.( )
=
6315 2
.
lb
diaph ectB
V
2
=
6315 27716
.
-
(
)
=
5084
lbshear at grid line ection B eft
2,
(
)
5084
16
v
2
=
= +
317 8
.plf unit shearatgrid linee ection B eft
2,
(
)
V
2
=
15 000
,
-
(
123
+
77
)(
16
)
=
11 800
,
lb shearat
grid line ight
2(
)
R
11 800
56
,
v
2
=
= +
210 7
.
plfunitshear at grid
line ight
2(
)
R
V
3
=
11 800
,
-
200 15
(
)
=
8800
lbshear at grid linee3
8800
56
v
3
=
= +
167 9
.plf unit shearatgrid linee3
V
4
=- ,
15 000
lbshear at grid line
4
=
-
15 000
56
,
v
43
=-
267 9
.plf unit shearatgrid line4
Search WWH ::
Custom Search