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V. ACI 318-99 Square Column

Determine the reinforced steel quantity for the square column as per ACI 318-99.

Reference

Chu-Kia Wang and Charles G.Slamon, Reinforced Concrete Design, 5th Edition, Examples problem 13.21.1, p509 .

Problem

Pu = 144 kips

Muz = 120 ft·kips

Muy = 54 ft·kips

f'c = 3,000 psi

fy = 60,000 psi

Comparison

Table 1. Comparison of results
Result Type Reference STAAD.Pro Difference
Provided steel area per ACI 318-99(in2) 8.0 (8- #9) 9.0 (4- #14) none
Note: In the reference book, the axial capacity provided is 141 kips, which is less than the requirement of 144 kips. In the STAAD implementation of the code, any reinforcement arrangement which yields less capacity than the required value is considered un-acceptable. This is why STAAD reports a higher required steel than the reference book.

STAAD Input

The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\10 Concrete Design\US\ACI\318-1999\ACI 318-99 Square Column.STD is typically installed with the program.

STAAD SPACE SQUARE COLUMN DESIGN ACI 318-99
START JOB INFORMATION
ENGINEER DATE 23-Sep-18
END JOB INFORMATION
*
* REFERENCE :  REINFORCED CONCRETE DESIGN 5TH EDITION BY CHU-KIA WANG
*             AND CHARLES G.SALMON  EX.13.21.1 PAGE 509.
*
*  OBJECTIVE : TO DETERMINE THE REINFORCED STEEL QUANTITY FOR A
*              SQUARE COLUMN PER THE ACI 318-99 CODE
*
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 12 0;
MEMBER INCIDENCES
1 1 2;
UNIT INCHES KIP
MEMBER PROPERTY AMERICAN
1 PRIS YD 16 ZD 16
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 3150
POISSON 0.17
END DEFINE MATERIAL
CONSTANTS
MATERIAL MATERIAL1 ALL
SUPPORTS
1 FIXED
UNIT FEET KIP
LOAD 1
JOINT LOAD
2 FY -144
2 MZ 120
2 MX 54
PERFORM ANALYSIS
START CONCRETE DESIGN
CODE ACI 1999
UNIT INCHES KIP
FC 3 ALL
FYMAIN 40 ALL
FYSEC 40 ALL
MINMAIN 9 ALL
TRACK 2 ALL
DESIGN COLUMN ALL
END CONCRETE DESIGN
FINISH

STAAD Output

   ====================================================================
        COLUMN  NO.     1  DESIGN PER ACI 318-99 - AXIAL + BENDING
   **WARNING: SKZ parameter value    0.00 is out of range for member      1
   Re-setting to default.
   **WARNING: SKY parameter value    0.00 is out of range for member      1
   Re-setting to default.
   FY - 40000  FC - 3000 PSI,  SQRE SIZE - 16.00 X 16.00 INCHES, TIED
           AREA OF STEEL REQUIRED =   8.348  SQ. IN.
   BAR CONFIGURATION       REINF PCT.   LOAD   LOCATION   PHI
   ----------------------------------------------------------
     4 - NUMBER 14           3.516        1      END     0.700
   (PROVIDE EQUAL NUMBER OF BARS ON EACH FACE)
   TIE BAR NUMBER    4 SPACING  16.00 IN
       COLUMN INTERACTION: MOMENT ABOUT Z -AXIS (KIP-FT)
    --------------------------------------------------------
      P0        Pn max    P-bal.    M-bal.   e-bal.(inch)
     989.85    791.88    312.89    272.99   10.47
       M0       P-tens.   Des.Pn    Des.Mn     e/h
     178.89   -360.00    205.71    171.43    0.06944
    --------------------------------------------------------
       COLUMN INTERACTION: MOMENT ABOUT Y -AXIS (KIP-FT)
    --------------------------------------------------------
      P0        Pn max    P-bal.    M-bal.   e-bal.(inch)
     989.85    791.88    312.89    272.99   10.47
       M0       P-tens.   Des.Pn    Des.Mn     e/h
     178.89   -360.00    205.71     77.14    0.03125
    --------------------------------------------------------
                            Pn       Mn       Pn       Mn    (@ Z )
            |              730.97   130.65   365.48   257.21
         P0 |*             670.05   156.16   304.57   272.89
            | *            609.14   178.25   243.66   267.81
      Pn,max|__*           548.22   199.53   182.74   255.16
            |   *          487.31   219.54   121.83   234.02
      Pn    |    *         426.40   238.66    60.91   206.96
     NOMINAL|     *         Pn       Mn       Pn       Mn    (@ Y )
       AXIAL|      *       730.97   130.65   365.48   257.21
 COMPRESSION|       *      670.05   156.16   304.57   272.89
          Pb|-------*Mb    609.14   178.25   243.66   267.81
            |      *       548.22   199.53   182.74   255.16
 ___________|____*_______  487.31   219.54   121.83   234.02
            |  * M0   Mn,  426.40   238.66    60.91   206.96
            | *   BENDING
      P-tens|*     MOMENT
            |            
      SQUARE COLUMN DESIGN ACI 318-99                          -- PAGE NO.    4