Civil Engineering Reference
In-Depth Information
Calculate factored shear force—V
u
The factored shear force
V
u
at the critical section is
V
u
=105.72×25/2-105.72×3.75=925.0 kips.
Nominal shear strength V
n
and resisting capacity V
c
hence
V
c
=922120 lb controls
Shear reinforcement
Assume No. 4 bars placed both horizontally and vertically on both faces of
the beam.
A
v
=
A
vh
=2×0.20=0.40 in
2
f
V
s
=
V
u
-
f
V
c
V
s
=(
V
u
/
f
)-
V
c
=(925 000/0.85)-922 120=166 115 lb
Assume that
s
=18 in in centre to centre and
s
2
=10.5 in centre to centre,
hence
=333642 lb>116 115 lb ? OK
The maximum permissible spacing of vertical bar:
s
=
d
/5 or 18.0 in which
ever is smaller;
s
=162/5=32.4 in. Hence 18.0 in controls, use
s
=18.0 in.
The maximum permissible spacing of horizontal bar:
s
2
=
d
/3 or 18.0 in
whichever is smaller;
s
2
=162/3=54.0in. Hence 10.5 in controls use
s
2
=10.5 in.
Check for minimum steel:
Minimum
A
v
=0.0015
bs
=0.0015×15×18=0.40 in
2
OK
Minimum
A
vh
=0.0025
bs
2
=0.0025×15×10.5=0.393 in
2
OK
Figure 5.11
shows the reinforcement details.
