A Tool for Designing Bar Structures

Structural Optimization Problems Page

Problem descriptions

Every structure designed with Ebe is described in a .ebe file. These files are used as input data to configure a jMetal problem that can be solved with many of the provided multi-objective metaheuristics.

In this page, we include some structures, providing for each of them:

  • Problem name
  • Description: number of nodes, number of bars, number of bar groups
  • Figure: Picture of the structure
  • .ebe file: File containing the description of the structure.
  • Pareto front approximation: front obtained with a multi-objective metaheuristic.

Problem nameDescriptionFigure.ebe filePareto front approximation
Bridge25N35B8G Mobile cable-strayed bridge with 25 nodes, 35 bars, 8 groups File

Algorithm: NSGA-II
Evaluations: 75000

Bridge33N221B33G Cable-strayed bridge with 133 nodes, 221 bars, 33 groups File

Algorithm: NSGA-II
Evaluations: 150000

Steps to solve the problems with jMetal

The optimization of the structural design problems with jMetal requires to follow these steps:

  1. The working directory must contain a file called "EBEs.txt" containing the name of the .ebe file describing the problem followed by number the "12"
  2. The .ebe file must be also in the working directory.
  3. Run a jMetal algorithm to optimize the problem.
  4. The algorithm will produce as output two files: "VAR", containing the variable values, and "FUN", containing the function values of the obtained front.

Some comments about optimizing the structural design problems

The encoding of the solutions of the Ebes problems is real, so most of the multi-objective metaheuristics provided by jMetal can be applied.

Depending on the complexity of the problem, the total running time of an optimization can be very high. Some examples:

  • Bridge25N35B8G: 2.4 minutes (NSGA-II, 75000 function evaluations)
  • Bridge33N221B33G: 4.2 hours (NSGA-II, 300000 function evaluations)
  • Computer: MacBook Pro, 2.2GHz Intel Core i7, 8 GB 1333 MHz DDR3, MacOS X 10.9.2, Java(TM) SE Runtime Environment (build 1.8.0-ea-b94)

The current implementation of Ebes problems in jMetal is not thread-safe, so multithreaded algorithms such as pMOEAD, pNSGAII, and pSMPSO cannot be used.