I noticed that when we design a rectangular column, STAAD Pro always arrange the reinforcements as equal number on each face ? I ask the instructor who teach us at Bentley and he didnt have an answer.
Not sure which code you are referring to. But for most codes, STAAD designs columns by placing equal number of bars on all 4 faces. For some codes like the Indian code, there is a parameter to specify if the bars should be just on 2 faces.
ACI-318-05 Code.I think that whatever you do, STAAD Pro can not handle unequal arrangement of bars.
check this output file:
****************************************************
* *
* STAAD.Pro V8i SELECTseries1 *
* Version 20.07.06.35 *
* Proprietary Program of *
* Bentley Systems, Inc. *
* Date= OCT 3, 2010 *
* Time= 20:34:35 *
* USER ID: *************************** *
1. STAAD SPACE
2. START JOB INFORMATION
3. ENGINEER DATE 03-OCT-10
4. END JOB INFORMATION
5. INPUT WIDTH 79
6. UNIT FEET KIP
7. JOINT COORDINATES
8. 1 0 0 0; 2 0 10 0
9. MEMBER INCIDENCES
10. 1 1 2
11. DEFINE MATERIAL START
12. ISOTROPIC CONCRETE
13. E 453600
14. POISSON 0.17
15. DENSITY 0.150336
16. ALPHA 5E-006
17. DAMP 0.05
18. END DEFINE MATERIAL
19. MEMBER PROPERTY
20. 1 PRIS YD 3.28084 ZD 0.984252
21. CONSTANTS
22. MATERIAL CONCRETE ALL
23. SUPPORTS
24. 1 FIXED
25. LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1
26. JOINT LOAD
27. 2 MX 100
28. PERFORM ANALYSIS
STAAD SPACE -- PAGE NO. 2
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ 1
SOLVER USED IS THE OUT-OF-CORE BASIC SOLVER
ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 6 DOF
TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = 6
SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS
REQRD/AVAIL. DISK SPACE = 12.0/ 327276.8 MB
29. START CONCRETE DESIGN
30. CODE ACI
31. MAXMAIN 10 ALL
32. DESIGN COLUMN ALL
STAAD SPACE -- PAGE NO. 3
====================================================================
COLUMN NO. 1 DESIGN PER ACI 318-05 - AXIAL + BENDING
FY - 60000 FC - 4000 PSI, RECT SIZE - 11.81 X 39.37 INCHES, TIED
AREA OF STEEL REQUIRED = 6.929 SQ. IN.
BAR CONFIGURATION REINF PCT. LOAD LOCATION PHI
----------------------------------------------------------
12 - NUMBER 7 1.548 1 END 0.650
(PROVIDE EQUAL NUMBER OF BARS ON EACH FACE) ???????
TIE BAR NUMBER 4 SPACING 11.81 IN
********************END OF COLUMN DESIGN RESULTS********************
33. END CONCRETE DESIGN
34. FINISH
For column design per the ACI code, STAAD offers only an arrangement that involves equal bars on all 4 faces.
I think this should be written beside the message :
(PROVIDE EQUAL NUMBER OF BARS ON EACH FACE)
by saying:
Note that: For current release, STAAD CAN ONLY ARRANGE COLUMNS BARS AS EQUAL NUMBER ON ALL 4 FACES.
in that way when STAAD somtimes said that there is no possible arrangemnet for bars, that not necessarlly lead to wrong design so one should increase the column size but one should check other arrangments that STAAD can not handle.
Mr. Ahmed Sh is right. Some change in Staad make engineer happier ever after, I think.