V. ACI 318-14 Circular Column
Calculate the axial capacity of a circular column subjected to axial compressive force, given Ast
Details
A circular, cantilever column of length 5ft with an ultimate axial load of 500 kip has the following concrete and steel properties.
- Compressive strength of concrete (normal weight concrete), fc = 4,000 psi
- Yield strength of steel, fy = 60,000 psi
- Clear spacing for outermost bottom reinforcement to bottom face, Cc = 1.5 in
- Diameter of column, D = 20 in
- Strength reduction factor, ϕ = 0.65
- Number of #8 bars, N = 6
- Rebar diameter for #8 bar, d = 1 in
Factored axial load (axial demand), Pu = 500 kip
Validation
Gross area of concrete section, Ag = πD2/4 = 314.159 in2
Total area of steel reinforcement,
Nominal axial strength at zero eccentricity:
P0 = 0.85×fc(Ag - Ast) + fy×Ast = 1.335×103 kip
For tied reinforced column:
Pn(max) = 0.8·P0 = 1.068×103 kip
Capacity = ϕPn(max) = 694.129 kip
Ratio = Pu/ϕPn(max) = 0.72
STAAD Input
The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\10 Concrete Design\US\ACI 318-14 Circular Column.STD is typically installed with the program.
STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 29-Aug-17
JOB NAME Circular Column Design
JOB CLIENT Bentley Systems Inc.
ENGINEER NAME TK
END JOB INFORMATION
INPUT WIDTH 79
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 5 0;
MEMBER INCIDENCES
1 1 2;
DEFINE MATERIAL START
ISOTROPIC CONCRETE
E 453600
POISSON 0.17
DENSITY 0.14999
ALPHA 5.5e-06
DAMP 0.05
TYPE CONCRETE
STRENGTH FCU 576
END DEFINE MATERIAL
MEMBER PROPERTY AMERICAN
1 PRIS YD 1.66667
CONSTANTS
MATERIAL CONCRETE ALL
SUPPORTS
1 FIXED
LOAD 1 LOADTYPE Dead TITLE LOAD CASE 1
JOINT LOAD
2 FY -500
PERFORM ANALYSIS
PRINT SUPPORT REACTION ALL
START CONCRETE DESIGN
CODE ACI 318 14
MAXMAIN 9 ALL
MINMAIN 8 ALL
TRACK 2 ALL
DESIGN COLUMN ALL
END CONCRETE DESIGN
FINISH
STAAD Output
STAAD.PRO CONCRETE DESIGN - (ACI-318-14) v2.0 *********************************************** Units: KIP , FEET (Unless Noted Otherwise) Member : 1 DESIGN SUMMARY ----------------------------------------------------------------------------- | Status : Pass Type : Column Length: 5.000 | | Critical Ratio : 0.720 Criteria: Axial | | Critical Clause: 10.5.2 | ----------------------------------------------------------------------------- CROSS SECTION ------------------------------------- | Shape: Circular | Dia: 1.67 | ------------------------------------- DESIGN INPUTS ------------------------------------------------------------------------- | Concrete | Fc 576.000 | | Ec 0.519E+06 | | Steel | Fy(main) 8639.999 | Fy(trans) 8639.999 | Es 0.418E+07 | | Cover | Top 0.125 | Bottom 0.125 | Sides 0.125 | ------------------------------------------------------------------------- CRITICAL STRENGTH RESULTS ----------------------------------------------------------------------- | Category | Demand | Min Capacity | Max Capacity | Ratio | ----------------------------------------------------------------------- | Axial | -500.000| -694.079 | 255.960 | 0.720 | | Flexure | 0.000| -148.011 | 148.011 | 0.000 | | Shear Y | 0.000| 0.000 | 0.000 | 0.000 | | Shear Z | 0.000| 0.000 | 0.000 | 0.000 | | Torsion | 0.000| 0.000 | 0.000 | 0.000 | ----------------------------------------------------------------------- LONGITUDINAL BAR DETAILS AT CROSS SECTIONS ----------------------------------------------------------------------- | Distance | Ast-reqd | Ast-prov | No(s)bars| Size | No of Layers | ----------------------------------------------------------------------- | 0.000 | 0.022 | 0.033 | 6 | # 8 | 1 | | 1.250 | 0.022 | 0.033 | 6 | # 8 | 1 | | 2.500 | 0.022 | 0.033 | 6 | # 8 | 1 | | 3.750 | 0.022 | 0.033 | 6 | # 8 | 1 | | 5.000 | 0.022 | 0.033 | 6 | # 8 | 1 | ----------------------------------------------------------------------- LONGITUDINAL BAR LAYOUT --------------------------------------------------------------------------- | | Bars | Location | Distance | Anchor | | Position | Nums | Size | Start | End | From Face | Start End | --------------------------------------------------------------------------- | Evenly Dist. | 6 | # 8 | 0.00| 5.00 | 0.17 | Yes Yes | --------------------------------------------------------------------------- STAAD SPACE -- PAGE NO. 6 TRANSVERSE BAR LAYOUT (Using Standard Ties) ------------------------------------------------------------------------------------ | | Asv | Rebar Specification | | Zone | Dir.| From | To | Reqd. | Prov. | Nums | Size | Spacing | Legs | ------------------------------------------------------------------------------------ | 1 | Y | 0.00 | 5.00 | 0.0021 | 0.0022 | 5 | # 4 | 1.25 | 2 | | 1 | Z | 0.00 | 5.00 | 0.0021 | 0.0022 | 5 | # 4 | 1.25 | 2 | ------------------------------------------------------------------------------------ ------------------------ Member: 1 Design Ends ------------------------