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PROJECT :
PAGE :
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CLIENT :
DESIGN BY :
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JOB NO. : DATE :
REVIEW BY :
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Design of Column Supporting Discontinuous System Based on CBC 2001/ ACI 318-05
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INPUT DATA & DESIGN SUMMARY
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CONCRETE STRENGTH
fc' =3ksi
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REBAR YIELD STRESS
fy =60ksi
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COLUMN CLEAR HEIGHT
h =16ft
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COLUMN SIZE
c1 =24in
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c2 =24in
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SEISMIC COEFFICIENT (Tab 16-N)
R =5.5
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AMPLIFICATION FACTOR (Tab 16-N)
W0 =2.8
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DESIGN LEVEL STORY DISPLACEMENT
DS =0.1in
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COLUMN LOADS, ASD (ft-kips, kips)
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PMtopVMbot
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DL40000
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LL20000
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E/1.4100802080
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LONGITUDINAL REINFORCING
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SECTIONTOPBOTTOM
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LEFT4#84#8
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( d =21.50in )( d =21.50in )
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( 1 Layer)( 1 Layer)
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RIGHT4#84#8
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( d =21.50in )( d =21.50in )
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( 1 Layer)( 1 Layer)
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THE COLUMN DESIGN IS ADEQUATE.
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TRANSVERSE REINFORCEMENT FOR CONFINEMENT
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3Legs #4@5
in, o.c., full height (ACI 318-05 21.4.4.5 / CBC 1921.4.4.5)
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ANALYSIS
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DESIGN CRITERIA
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1. since the column supported reaction from discontinued stiff member, CBC 1633.2.4 &1921.4.4.5 apply.
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2. since the column is not part of the lateral force resisting system, CBC 1921.7 apply.
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3. since the column Ld required into top & 12" at least into footing per CBC 1921.4.4.5, a fixed-fixed condition should be used.
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DESIGN LOADS
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U1 = 1.2 D + f1 L +1.0 W0 Eh
, (CBC 1630.8.2.1, 12-17 & 30-2)
U2 = 0.9 D ± 1.0 W0 Eh
, (CBC 1630.8.2.1, 12-18 & 30-2)
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Pu =450.0kipsMu,top =313.6ft-kipsPu =428.0kipsMu,top =313.6ft-kips
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Vu =78.4kipsMu,bot =313.6ft-kipsVu =78.4kipsMu,bot =313.6ft-kips
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f1 =0.5
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U3 = 1.4 D + 1.7 L
, (CBC 1909.2.1, conservatively than 1.2D + 1.6L of ACI 318-05 9.2.1)
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Pu =90.0kipsMu,top =0.0ft-kips
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Vu =0.0kipsMu,bot =0.0ft-kips
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CHECK CAPACITY SUBJECTED TO BENDING AND AXIAL LOAD
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LOADINGU1,topU1,botU2,topU2,botU3,topU3,bot
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Pu (kips)450.0450.0428.0428.090.090.0
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Mu (ft-kips)313.6313.6313.6313.60.00.0
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dns = Cm/[1-Pu/(0.75Pc)]
1.1161.1161.1101.1101.0211.021
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dnsMu (ft-kips)
349.9349.9348.0348.00.00.0
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fMn (ft-kips) @ Pu
419.8474.9476.2476.2404.7404.7
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where
EI = 0.4EcIg / (1+bd) = 0.25 EcIg
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Pc = p2EI / (kLu)2
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SUMMARY OF LOAD VERSUS MOMENT CAPACITIES (for ACI 318-05 10.2 & 10.3 only)
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CAPACITYf Pn (kips)
f Mn (ft-kips)
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AT AXIAL LOAD ONLY
10470
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AT MAXIMUM LOAD
1047175
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AT 0 % TENSION
893272
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AT 25 % TENSION
745336
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AT 50 % TENSION
622376
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AT e t = 0.002
431425
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AT BALANCED CONDITION
420428
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AT e t = 0.005
256537
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AT FLEXURE ONLY
0405
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f Pn (kips)(cont'd)
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f Mn (ft-kips)
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All load points to be within capacity diagram.
[Satisfactory]
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DETERMINE INDUCED MOMENT IN THE COLUMN
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282.181672
ft-kips, at top & bottom of column
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where
Ec = 57000 (fc')0.5 =
3122
ksi, ACI 318-05 8.5.1 / CBC 1908.5.1
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Ig = c1 c23 / 12 =
27648in4