# 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

P = 50 lbs

## Comparison

Table 1. Comparison of results
σBD 10.4 10.4 none
σCD 22.9 22.9 none

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 &amp; 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
4 FZ 50
PERFORM ANALYSIS
PRINT MEMBER STRESSES
FINISH
``````

```  ALL UNITS ARE POUN/SQ INCH