Civil Engineering Reference
In-Depth Information
4621 512
55
.( )
.
Header depth
d
=
=
21 53
.
in
3
Length = 18.5 - 0.533 - 0.727 = 17.24 ft
Height = 10 - 1.139 = 8.86 ft
The equivalent rectangular member sizes are located at their respective neutral axis
locations as shown in the figure. The pier sections are extended to the top of the wall as
previously discussed to account for the vertically offset lateral force. The uniform gravity
loads over the outer panel sections are applied as equivalent concentrated forces located
at the neutral axis of the pier sections.
P
L
=
020 533
.(.
)
=
0 107
.
k
P
R
=
020 727
.(.
)
=
0 145
.
k
Figure 14.18 shows that the base of the piers can be modeled by two different methods
as previously discussed. The first method is to create a fully fixed base node. The second
method replaces the fixed base with an additional horizontal member that extends
across the width of the piers, which has its ends fixed in the vertical direction only. The
horizontal members at the base are modeled using the same rectangular section as the
piers. The moment at the base of the vertical pier member is the transferred through
the horizontal member into the support nodes that will provide the actual anchor forces.
The latter method will be used for this example.
Computer output (see Fig. 14.19):
The load case of
W
+ 0.6
D
should be run for the maximum
overturning tension force and the design of the hold-down connections. The design
of the wall members for strength and for deflection should use load case
W
+
D
. The
appropriate load combinations should be used if seismic controls. The results of the
computer output for
W
+
D
can be seen in Figs. 14.19 through 14.21. The locations of
the inflection points determine the unbraced length of the compression flanges. The
contraflexure of the frame members causes the compression flanges to change sides of
the pier and header sections, as shown in Figs. 14.20 and 14.21.
Verify the right pier reaction (check) (Fig. 14.19):
FC
-
M
2490727
.
(.
)
-
712
.
T
=
x
2
1
=
=
398
.
k
b
1 333
.
pier
FC
+
M
2490606
.
(.
)
+
712
.
C
=
x
1
1
=
=
647
.
k
b
133
.
pier
Therefore the computer reactions are verified.
Design of the right pier section (see Fig. 14.20):
Forces at top:
F
x
= 2.49 k
apply all to inside jamb stud because of the
bearing condition of the header
M
4
=
732114
.
+
.
=
846
.
ft-k
omentattop plus offset moment
,
use
I
t
⊥
moment in piper at bottom of header
from similar triangles, use
I
n
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