# V. AISC LRFD - Select Compression and Biaxial Bending

To select the lightest ASTM A992 W14 section capable of carrying an axial compression plus biaxial bending.

## Reference

AISC Load Factor Resistance Design, 3rd Edition, Example 6.4, page 6-9.

## Problem

 Fy = 50 ksi

 Pu = 400 kips

 Muy = 80 ft·kips, Muz = 250 ft·kips

 Lb = 14 ft

Reverse curvature bending with equal end moments for both axis.

## Comparison

Table 1. Comparison of results
Result Type Theory STAAD.Pro Difference
Selection section W14x99 W14x99 none

The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\09 Steel Design\US\AISC\AISC LRFD - Select Compression and Biaxial Bending.STD is typically installed with the program.

``````STAAD SPACE AXIAL COMPRESSION + BIAXIAL BENDING PER AISC LRFD 3RD ED
START JOB INFORMATION
ENGINEER DATE 23-Sep-18
END JOB INFORMATION
*
*  EXAMPLE PROBLEM 6.4, PAGE 6-9, AISC LRFD 3RD ED.
*  THE LIGHTEST SUITABLE SECTION SHOULD BE A W14X99
*
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 14 0 0;
*
MEMBER INCIDENCES
1 1 2;
*
MEMBER PROPERTY AMERICAN
1 TABLE ST W14X90
*
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 4.176e+06
POISSON 0.3
END DEFINE MATERIAL
CONSTANTS
MATERIAL MATERIAL1 ALL
*
SUPPORTS
1 FIXED
*
2 FX -400
2 MZ 250
2 MY 80
*
PERFORM ANALYSIS
*
PARAMETER 1
CODE LRFD
FYLD 7200 ALL
TRACK 2 ALL
SELECT ALL
*
FINISH
``````

```      AXIAL COMPRESSION + BIAXIAL BENDING PER AISC LRFD 3RD ED -- PAGE NO.    3
STAAD.PRO MEMBER SELECTION - (LRFD 3RD EDITION)   v1.0
***********************************************
|--------------------------------------------------------------------------|
|                                                    Y        PROPERTIES   |
|*************                                       |        IN INCH UNIT |
|            *  |=============================|   ===|===     ------------ |
|MEMBER   1  *  |  AISC SECTIONS              |      |        AX=0.2910E+2 |
|            *  | ST  W14X99                  |      |   --Z  AY=0.6887E+1 |
|DESIGN CODE *  |                             |      |        AZ=0.1518E+2 |
| LRFD 2001  *  ===============================   ===|===     PY=0.8360E+2 |
|            *                                                PZ=0.1730E+3 |
|            *  |&lt;---LENGTH (FT)=   14.00 --->|               RY=0.3717E+1 |
|*************                                                RZ=0.6176E+1 |
|                                                                          |
|                250.0 (KIP-FEET)                                          |
|PARAMETER        |                               L1  L1  L1  CAPACITIES   |
|IN KIP  INCH     |                               L1  L1  L1  IN KIP  INCH |
|---------------  +                               L1  L1  L1  -------------|
| KL/R-Y=  45.20  |                               L1  L1  L1  PNC=0.1065E+4|
| KL/R-Z=  27.20  +                               L1  L1  L1  pnc=0.4000E+3|
| UNL   = 168.00  |L1 L1  L1  L1  L1  L1  L1  L1              PNT=0.1310E+4|
| CB    =   1.00  +L1 L1  L1  L1  L1  L1  L1  L1              pnt=0.0000E+0|
| PHIC  =   0.85  |L1 L1  L1  L1  L1  L1  L1  L1              MNZ=0.7717E+4|
| PHIB  =   0.90  +L1 L1  L1  L1  L1  L1  L1  L1              mnz=0.3000E+4|
| FYLD  =  50.00  |L1 L1  L1  L1  L1  L1  L1  L1              MNY=0.3698E+4|
| NSF   =   1.00  +---+---+---+---+---+---+---+---+---+---|   mny=0.9600E+3|
| DFF =     0.00 250.0                                        VN =0.1859E+3|
| dff =     0.00               ABSOLUTE MZ ENVELOPE           vn =0.0000E+0|
|                                 (WITH LOAD NO.)                          |
|                                                                          |
|                      MAX FORCE/ MOMENT SUMMARY  (KIP-FEET)               |
|                      -------------------------                           |
|                                                                          |
|                AXIAL      SHEAR-Y    SHEAR-Z    MOMENT-Y    MOMENT-Z     |
|                                                                          |
|      VALUE     400.0         0.0        0.0        80.0       250.0      |
|   LOCATION       0.0         0.0        0.0         0.0         0.0      |
|    LOADING         1           0          0           1           1      |
|                                                                          |
|**************************************************************************|
|*                                                                        *|
|*                         DESIGN SUMMARY  (KIP-FEET)                     *|
|*                         --------------                                 *|
|*                                                                        *|
|*       RESULT/     CRITICAL COND/     RATIO/         LOADING/           *|
|         FX              MY             MZ           LOCATION             |
|        ======================================================            |
|          PASS        LRFD-H1-1A-C     0.951              1               |
|        400.00 C        -80.00      -250.00             0.00              |
|*                                                                        *|
|**************************************************************************|
|                                                                          |
|--------------------------------------------------------------------------|
```