Abstract

Modified Augmented Lagrangian Genetic Algorithm (ALGA) and Quadratic Penalty Function Genetic Algo­rithm (QPGA) optimization methods are proposed to obtain truss structures with minimum structural weight using both continuous and discrete design variables. To achieve robust solutions, Compressed Sparse Row (CSR) with reordering of Cholesky factorization and Moore Penrose Pseudoinverse are used in case of non-singular and singular stiffness matrix, respectively. The efficiency of the proposed nonlinear optimization methods is demonstrated on several practical exam­ples. The results obtained from the Pratt truss bridge show that the optimum design solution using discrete parameters is 21% lighter than the traditional design with uniform cross sections. Similarly, the results obtained from the 57-bar planar tower truss indicate that the proposed design method using continuous and discrete design parameters can be up to 29% and 9% lighter than traditional design solutions, respectively. Through sensitivity analysis, it is shown that the proposed methodology is robust and leads to significant improvements in convergence rates, which should prove useful in large-scale applications.

Highlights

  • IntroductionJournal of Civil Engineering and Management, 2017, 23(2): 252–262 kinematic stability constraints

  • Structural optimization techniques are effective tools that can be used to obtain lightweight, low-cost and high performance structures

  • This paper aims to develop an efficient hybrid Genetic algorithms (GAs) method for size and topology optimization of truss structures using both continuous and discrete design variables

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Summary

Introduction

Journal of Civil Engineering and Management, 2017, 23(2): 252–262 kinematic stability constraints. Dede et al (2011) combined GA with value and binary encoding for continuous and discrete optimization of trusses to minimize structural weight based on stress and displacement constraints. The results of their study indicated that multiple truss topologies with almost equal overall weight can be found concurrently as the number of members in the ground structure increases. They showed that the value encoding method requires less computer memory and computational time to achieve optimum solutions. This paper aims to develop an efficient hybrid GA method for size and topology optimization of truss structures using both continuous and discrete design variables. The efficiency of the proposed methods to obtain reliable optimum solutions is investigated through sensitivity analysis

Objective function
Constraint handling
Procedure for obtaining the optimum solution
Size optimization using continuous cross-sectional areas
Size optimization using discrete cross-sectional areas
Size and topology optimization using discrete cross-sectional areas
Sensitivity analysis of 10-bar truss structure
Optimum results for 61-bar Pratt truss bridge
Convergence proof and sensitivity analysis
Optimum design of 57-bar planar tower truss
Findings
Summary and conclusions
Full Text
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