V. AISC LRFD - Non Compact Wide Flange 3
To determine the design bending strength of a non-compact American wide flange section bent about its strong axis.
Validation
The plastic limiting unbraced length is given by:
The inelastic limiting unbraced length is given by:
(F1-6) |
= | ||
= | ||
= |
Lp < Lb < Lr; thus, the section is inelastic.
The nominal flexural strength is:
(F1-2) |
Mr = FLSx = 40 × 93.0 = 3,720 in·k | (F1-7) |
Mp = FyZx = 50 × 107 = 5,350 in·k
Conservatively assume Cb = 1.0 (this is the default behavior in STAAD.Pro when the parameter is not directly specified).
The lateral-torsional buckling limit state capacity:
ϕbMn = 0.9×(4,071) = 3,664 in·k
Comparison
The reported STAAD.Pro value is based on the term MNZ in the STAAD.Pro output.
Result Type | Reference | STAAD.Pro | Difference | Comments |
---|---|---|---|---|
Design flexural strength, ϕbMn (in·kips) | 3,664 | 3,658.52 | negligible |
STAAD Input
The file C:\Users\Public\Public Documents\STAAD.Pro 2023\Samples \Verification Models\09 Steel Design\US\AISC\AISC LRFD - Non Compact Wide Flange 3.STD is typically installed with the program.
STAAD SPACE BENDING CAPACITY PER AISC LRFD 3RD ED
START JOB INFORMATION
ENGINEER DATE 23-Sep-18
END JOB INFORMATION
*
* EXAMPLE PROBLEM 5.2, CASE (B), PAGE 5-16, AISC LRFD 3RD ED.
* CAPACITY (MNZ) SHOULD BE ABOUT 306 KIP-FT
*
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 40 0 0;
*
MEMBER INCIDENCES
1 1 2;
*
MEMBER PROPERTY AMERICAN
1 TABLE ST W21X48
*
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 4.176e+06
POISSON 0.3
END DEFINE MATERIAL
CONSTANTS
MATERIAL MATERIAL1 ALL
*
SUPPORTS
1 PINNED
2 FIXED BUT MZ
*
LOAD 1
MEMBER LOAD
1 CON GY -10 13.333
1 CON GY -10 26.667
*
PERFORM ANALYSIS
*
PARAMETER 1
CODE LRFD
MAIN 1 ALL
FYLD 7200 ALL
UNT 13.333 ALL
TRACK 1 ALL
CHECK CODE ALL
FINISH
STAAD Output
STAAD.Pro CODE CHECKING - (LRFD 3RD EDITION) v1.0 *********************** ALL UNITS ARE - KIP FEET (UNLESS OTHERWISE Noted) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1 ST W21X48 (AISC SECTIONS) PASS LRFD-H1-1B-C 0.437 1 0.00 C 0.00 -133.33 13.33 +---------------------------------------------------------------------+ | DESIGN STRENGTHS FOR MEMBER 1 UNITS - KIP IN | | PNC= 35.84 PNT= 634.50 MNZ= 3658.52 MNY= 636.75 VN= 194.67 | +---------------------------------------------------------------------+