V. ACI 318-02 Rectangular Beam

Determine the reinforced steel quantity for a rectangular beam per the ACI 318 code.

Reference

Notes on ACI 318-02 Building Code Requirements for Structural Concrete, Example 7.1, p7-24, Design of Rectangular Beam with Tension Reinforcement Only

Notes on ACI 318-99 Building Code Requirements for Structural Concrete, Example 10.1, p10-10, Design of Rectangular Beam with Tension Reinforcement Only

Problem

 Live Load moment (service) = 35 ft·kips

 f'c = 4,000 psi

 fy = 60,000 psi

Comparison

Table 1. Comparison of results
Result Type ACI Notes STAAD.Pro Difference
Required steel area (in2) per ACI 318-99 2.78 2.793 none
per ACI 318-02 2.40 2.44 1.7%
Provided steel area (in2) per ACI 318-02 2.40 (2 - #8 & 1- #9) (2- #10) 2.45 1.7%

STAAD.Pro reports that it is unable to find a suitable bar arrangement to satisfy the reinforcement requirement per ACI 318-99. However, this does not mean that it is impossible to come up with a bar arrangement. When STAAD looks for a bar arrangement, it uses only bars of the same size. It begins with the bar size corresponding to the parameter MINMAIN. If an arrangement is not possible with that bar, it tries with the next larger bar size. If all the permissible bar sizes are exhausted, the program reports that it could not come up with a bar arrangement. However, the user may be able to satisfy the requirement by mixing bars of various diameters. For example, 3 # 11 bars and 2 # 10 bars may satisfy the requirement. The program is not equipped with facilities to come up with such combinations of bar sizes.

In fact, in the reference mentioned for the 1999 edition of ACI 318, the bar arrangement chosen is 2 # 9 and 1 # 8. It proves the point that finding bars of the same diameter is not possible for the 1999 edition based solution.

The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\10 Concrete Design\US\ACI\318-2002\ACI 318-02 Rectangular Beam.STD is typically installed with the program.

``````STAAD PLANE RECTANGULAR CONCRETE BEAM DESIGN PER ACI 318
START JOB INFORMATION
ENGINEER DATE 21-Sep-18
END JOB INFORMATION
*
* REFERENCE : NOTES ON ACI 318-02 BUILDING CODE REQUIREMENTS
*             FOR STRUCUTURAL CONCRETE EXAMPLE 7.1 (PAGE # 7-24)
*                             AND
*             NOTES ON ACI 318-99 BUILDING CODE REQUIREMENTS
*             FOR STRUCUTURAL CONCRETE EXAMPLE 10.1 (PAGE # 10-10)
*
*  OBJECTIVE : TO DETERMINE THE REINFORCED STEEL QUANTITY FOR A
*              RECTANGULAR BEAM PER THE ACI 318 CODE
*
*
INPUT WIDTH 79
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 10 0 0;
MEMBER INCIDENCES
1 1 2;
UNIT INCHES KIP
MEMBER PROPERTY AMERICAN
1 PRIS YD 16 ZD 10
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 3150
POISSON 0.17
END DEFINE MATERIAL
CONSTANTS
MATERIAL MATERIAL1 ALL
SUPPORTS
1 2 PINNED
UNIT FEET KIP
1 UNI GY -4.48
1 UNI GY -2.8
1 1.4 2 1.7
1 1.2 2 1.6
PERFORM ANALYSIS
*
** CONCRETE DESIGN AS PER ACI 318R-99
*
UNIT INCHES KIP
START CONCRETE DESIGN
CODE ACI 1999
FC 4 ALL
FYMAIN 60 ALL
TRACK 1 ALL
DESIGN BEAM ALL
END CONCRETE DESIGN
*
** CONCRETE DESIGN AS PER ACI 318R-02
*
START CONCRETE DESIGN
CODE ACI 2002
FC 4 ALL
FYMAIN 60 ALL
TRACK 1 ALL
DESIGN BEAM ALL
END CONCRETE DESIGN
FINISH
``````

```      RECTANGULAR CONCRETE BEAM DESIGN PER ACI 318             -- PAGE NO.    3
=====================================================================
BEAM  NO.     1 DESIGN RESULTS - FLEXURE PER CODE ACI 318-99
LEN -  10.00FT.  FY - 60000.  FC - 4000.  SIZE - 10.00 X 16.00 INCHES
LEVEL    HEIGHT     BAR INFO       FROM            TO         ANCHOR
FT.    IN.              FT.     IN.     FT.     IN.   STA  END
_____________________________________________________________________
*** A SUITABLE BAR ARRANGEMENT COULD NOT BE DETERMINED.
REQD. STEEL =  2.793 IN2,  MAX. STEEL PERMISSIBLE =  2.873 IN2
___   1J____________________  120.X  10.X  16_____________________   2J____
|                                                                           |
|                                                                           |
|                                                                           |
|                                                                           |
|                                                                           |
|                                                                           |
|                                                                           |
|___________________________________________________________________________|
_________    _________    _________    _________    _________     _________
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|_________|  |_________|  |_________|  |_________|  |_________|   |_________|
********************END OF BEAM DESIGN**************************
57. END CONCRETE DESIGN
58. *
59. ** CONCRETE DESIGN AS PER ACI 318R-02
60. *
62. START CONCRETE DESIGN
CONCRETE DESIGN
63. CODE ACI 2002
64. FC 4 ALL
65. FYMAIN 60 ALL
66. TRACK 1 ALL
67. DESIGN BEAM ALL
RECTANGULAR CONCRETE BEAM DESIGN PER ACI 318             -- PAGE NO.    4
=====================================================================
BEAM  NO.     1 DESIGN RESULTS - FLEXURE PER CODE  ACI 318-02
LEN -  10.00FT.  FY - 60000.  FC - 4000.  SIZE - 10.00 X 16.00 INCHES
LEVEL    HEIGHT     BAR INFO       FROM            TO         ANCHOR
FT.    IN.              FT.     IN.     FT.     IN.   STA  END
_____________________________________________________________________
1    0 + 2-3/4    2-NUM.10     0 + 0-0/0     10 + 0-0/0    YES  YES
|----------------------------------------------------------------|
|   CRITICAL POS MOMENT=    123.20 KIP-FT  AT  5.00 FT, LOAD    4|
|   REQD STEEL=  2.44 IN2, RHO=0.0183, RHOMX=0.0214 RHOMN=0.0033 |
|   MAX/MIN/ACTUAL BAR SPACING= 10.00/ 2.54/ 4.73 INCH           |
|   REQD. DEVELOPMENT LENGTH = 48.52 INCH                        |
|----------------------------------------------------------------|
Cracked Moment of Inertia Iz at above location =    1817.34 inch^4
B E A M  N O.     1 D E S I G N  R E S U L T S - SHEAR
AT START SUPPORT - Vu=   38.19 KIP  Vc=   21.42 KIP  Vs=   29.50 KIP
Tu=    0.00 KIP-FT  Tc=   1.95 KIP-FT  Ts=   0.00 KIP-FT  LOAD     4
NO STIRRUPS ARE REQUIRED FOR TORSION.
REINFORCEMENT IS REQUIRED FOR SHEAR.
PROVIDE NUM. 4 2-LEGGED STIRRUPS AT  6.7 IN. C/C FOR   46. IN.
AT END   SUPPORT - Vu=   38.19 KIP  Vc=   21.42 KIP  Vs=   29.50 KIP
Tu=    0.00 KIP-FT  Tc=   1.95 KIP-FT  Ts=   0.00 KIP-FT  LOAD     4
NO STIRRUPS ARE REQUIRED FOR TORSION.
REINFORCEMENT IS REQUIRED FOR SHEAR.
PROVIDE NUM. 4 2-LEGGED STIRRUPS AT  6.7 IN. C/C FOR   46. IN.
RECTANGULAR CONCRETE BEAM DESIGN PER ACI 318             -- PAGE NO.    5
___   1J____________________  120.X  10.X  16_____________________   2J____
|                                                                           |
|                                                                           |
|                                                                           |
|  8#4 C/C  7                                                 8#4 C/C  7    |
| 2#10H   3.   0.TO  120.                                                   |
||=========================================================================||
|                                                                           |
|___________________________________________________________________________|
_________    _________    _________    _________    _________     _________
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
|         |  |         |  |         |  |         |  |         |   |         |
| 2#10    |  | 2#10    |  | 2#10    |  | 2#10    |  | 2#10    |   | 2#10    |
|   OO    |  |   OO    |  |   OO    |  |   OO    |  |   OO    |   |   OO    |
|         |  |         |  |         |  |         |  |         |   |         |
|_________|  |_________|  |_________|  |_________|  |_________|   |_________|
********************END OF BEAM DESIGN**************************
```