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V. AISC ASD - Rectangular Tube Compression Capacity

Determine the axial compression capacity of a rectangular 7x5x3/8 structural tube.

Reference

AISC Allowable Stress Design, 9th Edition, tables on page 3-49.

Problem

Fy =46 ksi

KyLy = KzLz = 25ft

Comparison

The reported STAAD.Pro value is obtained by multiplying FA times AX from the STAAD.Pro output = 6.32(8.08) = 51.06.

Table 1. Comparison of results
Result Type Theory STAAD.Pro Difference
Axial capacity (kips) 51 51.1 <1%

STAAD Input

The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\09 Steel Design\US\AISC\ASD 9th Edition\AISC ASD - Rectangular Tube Compression Capacity.STD is typically installed with the program.

STAAD SPACE AISC VERIFICATION PROBLEM FOR AXIAL COMPRESSION CAPACITY.
START JOB INFORMATION
ENGINEER DATE 03-Sep-18
END JOB INFORMATION
* PAGE 3-49 OF 9TH ED. AISC-ASD. RECTANGULAR TUBE 7X5X3/8, 25 FT LONG.
* FA SHOULD BE APPROX. 51/8.08 = 6.31 KSI
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 25 0;
MEMBER INCIDENCES
1 1 2;
START USER TABLE
TABLE 1
UNIT INCHES KIP
TUBE
TUB70506
8.08 7 5 0.375 52.2 30.8 64.2 3.97 2.98
END
UNIT INCHES KIP
MEMBER PROPERTY AMERICAN
1 UPTABLE 1 TUB70506
*1 TA ST TUB70506
DEFINE MATERIAL START
ISOTROPIC STEEL_50_KSI
E 29000
POISSON 0.3
DENSITY 0.000283
ALPHA 6.5e-06
DAMP 0.03
TYPE STEEL
STRENGTH FY 50 FU 62 RY 1.5 RT 1.2
END DEFINE MATERIAL
UNIT FEET KIP
CONSTANTS
MATERIAL STEEL_50_KSI ALL
SUPPORTS
1 FIXED
LOAD 1
JOINT LOAD
2 FY -50
PERFORM ANALYSIS
UNIT INCHES KIP
PARAMETER 1
CODE AISC
FYLD 46 ALL
TRACK 2 ALL
CHECK CODE ALL
FINISH

STAAD Output

                       STAAD.PRO CODE CHECKING - (AISC 9TH EDITION)   v1.0
                       ********************************************
  |--------------------------------------------------------------------------|
  |                                                    Y        PROPERTIES   |
  |*************                                       |        IN INCH UNIT |
  |            *  |=============================|   |=====|     ------------ |
  |MEMBER   1  *  |            UPT              |   |     |     AX =   8.08  |
  |            *  | UP  TUB70506                |   |     |--Z  AY =   3.97  |
  |DESIGN CODE *  |                             |   |     |     AZ =   2.98  |
  | AISC-1989  *  ===============================   |=====|     SY =  12.32  |
  |            *                                                SZ =  14.91  |
  |            *  |&lt;---LENGTH (FT)=   25.00 --->|               RY =   1.95  |
  |*************                                                RZ =   2.54  |
  |                                                                          |
  |                  0.0 (KIP-FEET)                                          |
  |PARAMETER        |L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  STRESSES     |
  |IN KIP  INCH     |L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  IN KIP  INCH |
  |---------------  +L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  -------------|
  | KL/R-Y= 153.66  |L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  FA  =   6.32 |
  | KL/R-Z= 118.03  +L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  fa  =   6.19 |
  | UNL   = 300.00  |L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  FCZ =  27.60 |
  | CB    =   1.00  +L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  FTZ =  27.60 |
  | CMY   =   0.85  |L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  FCY =  27.60 |
  | CMZ   =   0.85  +L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  FTY =  27.60 |
  | FYLD  =  46.00  |L0 L0  L0  L0  L0  L0  L0  L0  L0  L0  L0  fbz =   0.00 |
  | NSF   =   1.00  +---+---+---+---+---+---+---+---+---+---|   fby =   0.00 |
  | DFF   =   0.00   0.0                                        Fey =   6.32 |
  | dff=      0.00               ABSOLUTE MZ ENVELOPE           Fez =  10.72 |
  | (KL/R)max = 153.66              (WITH LOAD NO.)             FV  =  18.40 |
  |                                                             fv  =   0.00 |
  |                                                                          |
  |                      MAX FORCE/ MOMENT SUMMARY  (KIP-FEET)               |
  |                      -------------------------                           |
  |                                                                          |
  |                AXIAL      SHEAR-Y    SHEAR-Z    MOMENT-Y    MOMENT-Z     |
  |                                                                          |
  |      VALUE      50.0         0.0        0.0         0.0         0.0      |
  |   LOCATION       0.0         0.0        0.0         0.0         0.0      |
  |    LOADING         1           0          0           0           0      |
  |                                                                          |
  |**************************************************************************|
  |*                                                                        *|
  |*                         DESIGN SUMMARY  (KIP-FEET)                     *|
  |*                         --------------                                 *|
  |*                                                                        *|
  |*       RESULT/     CRITICAL COND/     RATIO/         LOADING/           *|
  |         FX              MY             MZ           LOCATION             |
  |        ======================================================            |
  |          PASS        AISC- H1-1       0.978              1               |
  |         50.00 C          0.00         0.00             0.00              |
  |*                                                                        *|
  |**************************************************************************|
  |                                                                          |