V. AISC LRFD - Angle Section Compression Capacity

To determine the design strength of an 8ft long single angle L4X3.5X5/16 in axial compression.

References

Hand calculation using the following reference:

AISC Load Factor Resistance Design, 3rd Edition, Example 4.3, page 4-12.

Details

The column is pinned at its ends and no intermediate bracing.

F_y =36 ksiLength = 8 ft

Results

The reported STAAD.Pro value is based on the term PNC in the STAAD.Pro output..

Table 1. Comparison of results
Result Type	Theory	STAAD.Pro	Difference	Comments
Design strength (kips)	28.7	28.66	Negligible

Input

The file C:\Users\Public\Public Documents\STAAD.Pro 2026\Samples \Verification Models\09 Steel Design\US\AISC\AISC LRFD - Angle Section Compression Capacity.STD is typically installed with the program.

STAAD

STAAD SPACE AXIAL COMPRESSION CAPACITY PER AISC LRFD 3RD ED
START JOB INFORMATION
ENGINEER DATE 23-Sep-18
END JOB INFORMATION
*
*  EXAMPLE PROBLEM 4.3, PAGE 4-12, AISC LRFD 3RD ED.
*  CAPACITY (PNC) SHOULD BE ABOUT 28.7 KIPS
*
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 8 0;
MEMBER INCIDENCES
1 1 2;
MEMBER PROPERTY AMERICAN
1 TABLE ST L40355
UNIT INCHES KIP
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 29000
POISSON 0.3
END DEFINE MATERIAL
UNIT FEET KIP
CONSTANTS
MATERIAL MATERIAL1 ALL
SUPPORTS
1 PINNED
2 FIXED BUT FY MX MZ
LOAD 1
JOINT LOAD
2 FY -25
PERFORM ANALYSIS
UNIT INCHES KIP
PARAMETER 1
CODE LRFD
FYLD 36 ALL
TRACK 1 ALL
CHECK CODE ALL
FINISH

Output

                         STAAD.Pro CODE CHECKING - (LRFD 3RD EDITION)   v1.0
                         ***********************
 ALL UNITS ARE - KIP  INCH (UNLESS OTHERWISE Noted)
 MEMBER     TABLE       RESULT/   CRITICAL COND/     RATIO/     LOADING/
                          FX            MY             MZ       LOCATION
 =======================================================================
      1  ST   L40355                   (AISC SECTIONS)
                           PASS     LRFD-H1-1A-C       0.872         1
                       25.00 C          0.00           0.00        0.00
 +---------------------------------------------------------------------+
 | DESIGN STRENGTHS FOR MEMBER     1       UNITS - KIP IN              |
 | PNC=   28.66  PNT=   72.90  MNZ=   60.87  MNY=   67.97  VN=   16.23 | 
 +---------------------------------------------------------------------+