OS-E: 0920 Ten Bar Truss

Demonstrates how size (parameter) optimization can be used.

Figure 1. Structural Model

Model Files

Before you begin, copy the file(s) used in this example to your working directory.

Model Description

For the ten bar truss structure, a cross-sectional area distribution is sought that minimizes the structural mass and allows limited stress values in the elements. The stress limit is 25000. The y displacements are limited to 2.

The cross-sectional area for each element is varied. Therefore, 10 variables are defined in the analysis deck. The initial cross-sectional area of all the elements is 20, with a lower bound of 0.2 and an upper bound of 200.

The optimization problem, objective and constraint functions, is defined in the same manner as for the other types of structural optimization. OptiStruct then goes through an iteration process to solve the optimization problem. OptiStruct converged after thirteen iterations.


Table 1 shows the optimization results of the ten bar truss structure, which met the constraints and minimizes the mass (decrease of 38.7%).
Table 1.
  Bar1 Bar2 Bar3 Bar4 Bar5 Bar6 Bar7 Bar8 Bar9 Bar10 Volume
Initial 20 20 20 20 20 20 20 20 20 20 83929
Final 30.4 38.4 24.5 15.4 0.2 0.2 8.8 21.5 20.1 0.4 51448