V. Axial Stress on a Truss Model
To find member stress due to a joint load in a space truss using static analysis.
Reference
Beer, F.P., and Johnston, Jr., E.R., Vector Mechanics for Engineers, Statics and Dynamics, McGraw - Hill, Inc., New York, 1962, p.47, Problem 2.70.
Problem
A 50 lb load is supported by three bars which are pinned to a ceiling as shown. Determine the stress, σ, in each bar.
Area of each bar = 1 in2, E = 30 (10)6 psi
Space truss
P = 50 lbs
Comparison
| Result Type | Theory | STAAD.Pro | Difference |
|---|---|---|---|
| σAD | 31.2 | 31.2 | none |
| σBD | 10.4 | 10.4 | none |
| σCD | 22.9 | 22.9 | none |
STAAD Input
The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\02 Trusses\Axial Stress on a Truss Model.STD is typically installed with the program.
STAAD TRUSS :A SPACE TRUSS
START JOB INFORMATION
ENGINEER DATE 18-Sep-18
END JOB INFORMATION
*
* REF: "VECTOR MECHANICS FOR ENGINEERS, STATICS & DYNAMICS",
* MCGRAW HILL BOOK CO., INC., NEW YORK, 1962
* PROBLEM 2.70, PAGE 47.
*
UNIT FEET POUND
JOINT COORDINATES
1 0 0 0; 2 8 0 0; 3 0 6 0; 4 4 2 6;
MEMBER INCIDENCES
1 1 4; 2 2 4; 3 3 4;
UNIT INCHES POUND
MEMBER PROPERTY AMERICAN
1 TO 3 PRIS AX 1
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 3e+07
POISSON 0.290909
END DEFINE MATERIAL
CONSTANTS
MATERIAL MATERIAL1 ALL
SUPPORTS
1 TO 3 PINNED
LOAD 1 WEIGHT
JOINT LOAD
4 FZ 50
PERFORM ANALYSIS
PRINT MEMBER STRESSES
FINISH
STAAD Output
ALL UNITS ARE POUN/SQ INCH MEMB LD SECT AXIAL BEND-Y BEND-Z COMBINED SHEAR-Y SHEAR-Z 1 1 .0 10.4 T 0.0 0.0 10.4 0.0 0.0 1.0 10.4 T 0.0 0.0 10.4 0.0 0.0 2 1 .0 31.2 T 0.0 0.0 31.2 0.0 0.0 1.0 31.2 T 0.0 0.0 31.2 0.0 0.0 3 1 .0 22.9 T 0.0 0.0 22.9 0.0 0.0 1.0 22.9 T 0.0 0.0 22.9 0.0 0.0 ************** END OF LATEST ANALYSIS RESULT ************** 32. FINISH