V. AISC LRFD - Rectangular HSS Compression Strength

To validate that an American ASTM A500 grade B HSS12X10X1/2 compression member has a design compressive strength of over 500 kips.

Reference

Hand calculation using the following reference:

AISC Load Factor Resistance Design, 3rd Edition, Example 4.8, page 4-13 & Table 4-6, Page 4-50.

Problem

F_y = 46 ksi

Length = 20 ft

KY = KZ = 0.8

Comparison

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
Design strength in Axial Compression (kips)		634 (*)	634.26	none

Note: * In the solved example, on page 4-14, the capacity is reported as ϕ×Pn = 580 kips. Looking at Table 4-6 on page 4-50, this happens to be the capacity for a 20 ft effective length, not a 16 ft effective length. As per the table, the capacity corresponding to a 16 ft effective length is 634 kips.

STAAD Input

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

STAAD SPACE AXIAL COMPRESSION CAPACITY PER AISC LRFD 3RD ED
START JOB INFORMATION
ENGINEER DATE 23-Sep-18
END JOB INFORMATION
*
*  EXAMPLE PROBLEM 4.5, PAGE 4-13, AISC LRFD 3RD ED.
*  CAPACITY (PNC) SHOULD BE ABOUT 634 KIPS
*
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 20 0;
MEMBER INCIDENCES
1 1 2;
MEMBER PROPERTY AMERICAN
1 TABLE ST HSST12X10X0.5
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 -500
PERFORM ANALYSIS
UNIT INCHES KIP
PARAMETER 1
CODE LRFD
FYLD 46 ALL
KY 0.8 ALL
KZ 0.8 ALL
TRACK 1 ALL
CHECK CODE ALL
FINISH

STAAD 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   HSST12X10X0.5            (AISC SECTIONS)
                           PASS     HSS COMPRESS       0.788         1
                      500.00 C          0.00           0.00        0.00
 +---------------------------------------------------------------------+
 | DESIGN STRENGTHS FOR MEMBER     1                    UNITS - KIP IN |
 | PNC=  634.26      PNT=  786.60      MNZ= 3262.32       MNY= 2881.44 |
 | VNZ=  231.01      VNY=  277.21      TN= 2533.68                     |
 +---------------------------------------------------------------------+