V. AISC LRFD - Wide Flange Tension Capacity

To check the adequacy of a W8X24 American section to carry a tensile design load of 245 Kips.

Reference

Hand calculation using the following reference:

AISC Load Factor Resistance Design, 3rd Edition, Example 3.1, case (a), page 3-5.

Problem

Assume the reduction in area due to bolt holes to be equivalent to a net section factor of 0.72.

F_y =50 ksi

L =10ft

Hand Calculation

Net section = 0.72(7.08in.²) = 5.11 in.²

ϕ P_{n} = {\begin{matrix} ϕ_{t} F_{y} A_{g} = 0.9 (50 k s i) (7.08 {i n .}^{2}) = 318.6 k \\ ϕ_{t} F_{u} A_{e} = 0.75 (65 k s i) (5.11 {i n .}^{2}) = 248.5 k \end{matrix}

Comparison

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

表 1. Comparison of results
Result Type		Theory	STAAD.Pro	Difference
Design strength (kips)		248.5	248.51	none

注記: The assumed NSF of 0.72 is comparable to the term Ae/Ag which evaluates to 5.11/7.08.

STAAD Input

The file C:\Users\Public\Public Documents\STAAD.Pro 2023\Samples \Verification Models\09 Steel Design\US\AISC\AISC LRFD - Wide Flange Tension Capacity.STD is typically installed with the program.

STAAD SPACE TENSION CAPACITY PER AISC LRFD 3RD ED
START JOB INFORMATION
ENGINEER DATE 23-Sep-18
END JOB INFORMATION
*
*  OBJECTIVE : CHECKING THE DESIGN AXIAL TENSILE STRENGTH OF A
*  W8X24 AMERICAN SECTION. CAPACITY SHOULD BE 245 KIPS ACCORDING TO
*  EXAMPLE 3-1 ON PAGE 3-5 OF 3RD EDITION LRFD CODE.
*
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 10 0 0;
MEMBER INCIDENCES
1 1 2;
MEMBER PROPERTY AMERICAN
1 TABLE ST W8X24
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 FIXED
LOAD 1
JOINT LOAD
2 FX 245
PERFORM ANALYSIS
UNIT INCHES KIP
PARAMETER 1
CODE LRFD
* NSF = 5.11/7.08 = 0.72
NSF 0.72 ALL
FYLD 50 ALL
FU 65 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   W8X24                    (AISC SECTIONS)
                           PASS     LRFD-H1-1A-T       0.986         1
                      245.00 T          0.00           0.00        0.00
 +---------------------------------------------------------------------+
 | DESIGN STRENGTHS FOR MEMBER     1       UNITS - KIP IN              |
 | PNC=  200.22  PNT=  248.51  MNZ=  930.59  MNY=  380.08  VN=   52.46 | 
 +---------------------------------------------------------------------+