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bottom of footing face of wall [critical
section for moment] f twoway or punching
h
s is the
effective depth “d”hear line
distance from top of the shear line
oneway
footing to the centroid of
c
d
the reinforcing steel g
ld oneway shear line c upward soil pressure ld d 3” cover twoway or punching
shear line d
3” cover ld e h d distance “d” from the
face of the wall [critical
section for shear] a face of wall [critical
sd/2 for moment]
ection d d d distance “d” from the
d
face of the wall [critical
section for shear] column
load [P] e g face of wall [critical
section for moment] f h d
g twoway or punching
shear line h c
tension
reinforcing 12” 36” 5’ below grade c
upward soil pressure #8 bar [1in dia] d d d d Step 03: Check for Shear at Critical Section [Face of Wall] d tension
reinforcing face of column: [critical
section for moment] development length of
reinforcing steel tension in
bottom of footing Concrete strength:
Steel Strength:
Dead Load:
Live Load:
Max Soil Pressure: f’c = 3000psi,
12”
fy = 60,000psi,
14,000 lb/ft of wall length,
7,000 lb/ft of wall length,
3,500 lb/ft2 12” ld d = 12in  3in – 0.5in = 8.5in
V = (3ft – d)(1ft)(qs) = (3ft – 0.708ft)(1ft)(4500lb/ft2) = 10,314lb à༎ Actual Shear 12” ld #4 bars [7in o.c.] d
3” cover ld ld 12” Mu = qs(I2)/2 = 4,500(32)/2 = 20,250 ftlb Allowable Shear [ACI Code]: d
d The leg of the footing acts as an inverted cantilever beam: 12” #8 bar [1in dia] d d Step 04: Find the Moment [Face of Wall] ld 12” 36” 5’ below grade d d 3” cover ld 12” #4 bars [7in o.c.] d V = Φ2√fcbd = 0.85(2)√3000(12)(8.5) = 9,497lb
à༎ since actual shear > allowable shear à༎ Need to 14” a 14” deep footing d
try
V = Φ2√fcbd = 0.85(2)√3000(12)(10.5) = 11,732lb #5 bars [8in o.c.]
à༎ now actual shear < allowable shear à༎ 14” deep footing OKAY! ARCH3355  Construction III  Spring 2013 effective depth “d” is th
distance from top of th
footing to the centroid
the reinforcing steel ld Find the required depth, width, and reinforcement for the following load: 12” d 3” cover oneway shear line development length of
reinforcing steel tension in
bottom of footing f’c = 3000psi,
12”
fy = 60,000psi,
14,000 lb/ft of wall length,
7,000 lb/ft of wall length,
3,500 lb/ft2 twoway or punching
shear line Designing Wall Footings: Example face of column: [critical
section for moment] Find the required depth, width, and reinforcement for the f...
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This note was uploaded on 02/04/2014 for the course ARCH 3355 taught by Professor Staff during the Spring '08 term at Texas Tech.
 Spring '08
 Staff

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