Position and Thickness Optimization of Ribs for Ventilation Covering Using the Micro Genetic Algorithm with an Interpolated Smooth Objective Function

Young-Doo Kwon,Seong-Su Kim,Jin-Won Lee,Soon-Bum Kwon

doi:10.1155/2015/859653

Abstract

Structures with supporting ribs are adopted in many fields of engineering. These ribs are attached to the main plate or shell to increase stiffness and reduce the stresses of a structure. Currently, much research in structural optimization has been devoted to size or thickness optimizations. In this study, the discrete positions of the ribs of a structure are optimized in addition to their thicknesses. The objective function, which is the total weight of a structure, is a continuous function with respect to the thickness of the ribs. However, it is a stepwise function of a dimensionless variable, which represents the set of positions of the ribs. Because of this stepwise objective function, the gradient method of optimization is not applicable. Therefore, we applied the micro genetic algorithm (MGA), which does not need derivatives of the objective function. To accelerate the rate of convergence, the stepwise objective function is interpolated to a smooth artificial objective function that does not alter the optimal solution.

Highlights

With the recent construction of large-scale buildings, there has been an increase in the number of ventilation facilities for the ventilation of underground spaces with a dramatic increase in the underground sector
As reported in The Law & Police News [2], 27 people who had climbed atop an aboveground ventilation facility to witness a recent live concert in Seoul, Korea, either lost their lives or were seriously injured when the steel covering collapsed, which was caused by accidental overloading on the ventilation shafts. An investigation of this accident was conducted, and the results indicated that the collapse was attributed to overloading on the stiffening ribs of the ventilation shaft, not because of any defect in the top plate
The discrete optimization problem can be converted into a continuous variable problem, which resulted in a stepwise objective function problem

Summary

Introduction

With the recent construction of large-scale buildings, there has been an increase in the number of ventilation facilities for the ventilation of underground spaces with a dramatic increase in the underground sector. The heights of most shafts are accessible to passersby. As studied by Lee et al [1], steel coverings are structures that mainly function as drainage covers, as they enhance the strength of the structure and facilitate efficient drainage through the formation of a tilted inflow tract for wastewater or rainfall. These covers enable smooth discharge and inflow of air through large openings of ventilation holes, which prevents a loss of ventilation shaft efficiency. Given the fact that most of the steel covering is subjected to considerable loads, several designs have been developed that take the safety of steel coverings into consideration

Methods

Results

Conclusion