Moacir Kripka

Discrete optimization of trusses by simulated annealing

At present, several methods are available for optimization of structures. The application of such methods to real structural problems, however, has not been as intense as the development of the techniques themselves. One of the main reasons is that the great majority of the methods, based on mathematical programming, consider a continuous search space. This paper presents an application of the Simulated Annealing method to the optimization of trusses considering the cross sections of the members as discrete variables. The constraints imposed to the analysis were the allowable stresses and the displacements on nodes. Some examples are presented in order to demonstrate the effectiveness of the method when compared with other methods found in literature.

Cross-Sectional Optimization of Reinforced Concrete Columns Considering both Economical and Environmental Costs

This work presents the development and implementation of a mathematical formulation for obtaining optimal sections of reinforced concrete columns subjected to uniaxial flexural compression. In order to minimize the cost of the reinforced concrete columns, the amount and diameters of the reinforcement bars and the dimensions of the columns cross sections were considered as discrete variables. The optimization was made by Harmony Search optimization method, a metaheuristic inspired by music performance. Initially, the economical cost of each material (concrete, steel and formwork) were considered, as usual in most optimization strategies. In the sequence, the lesser environmental cost was studied, by considering the Life Cicle Assessment (LCA) to determine the global warming potential. The results obtained led to a different configuration when the objective is a reduction in carbon dioxide (CO2) emissions, regarding the optimum economical cost.

Otimização númerica e experimental de perfis U formados a frio sujeitos à compressão

This paper presents a numeric study that aims to obtaining minimum weight of cold-formed channel columns, with and without lips. Flexural, torsional and torsional-flexural buckling of columns were considered as constraints. The design of cold-formed steel columns was prepared on the basis of the 2001 edition of the North American Specification for the Design of ColdFormed Steel Structural Members. The optimization was made through the Simulated Annealing method. Several numeric simulations are presented and discussed with the main goal of validate the proposal, as well as an experimental example that qualifies the implementation.

Advanced Optimization Techniques and Their Applications in Civil Engineering

Department of Civil Engineering, Karadeniz Technical University, 61080 Trabzon, Turkey Department of Civil Engineering, Universidade de Passo Fundo, 99001-970 Passo Fundo, RS, Brazil ICITECH, Department of Construction Engineering, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain Department of Mechanical Engineering, Sardar Vallabhai National Institute of Technology, Gujarat 395007, India

Determinação do posicionamento ótimo de apoios em pontes

O presente trabalho apresenta um estudo para a determinacao do posicionamento otimizado dos apoios em pontes, bem como da relacao otima entre os vaos de vigas de pontes visando conduzir tanto a reducao como a uniformizacao dos esforcos nestas estruturas. O problema matematico foi formulado tendo como objetivo a minimizacao dos momentos fletores maximos, tendo como variaveis de projeto as coordenadas relativas de cada apoio interno. Na formulacao as coordenadas nodais sao canalizadas, uma vez que podem existir limitacoes a livre locacao dos apoios. O programa desenvolvido com base neste estudo determina os esforcos em cada apoio, para o deslocamento da carga ao longo da estrutura, a partir do Metodo dos Deslocamentos para analise de estruturas reticuladas, efetuando a otimizacao com o emprego de tecnica de programacao matematica. As estruturas analisadas a partir da implementacao computacional do modelo idealizado apontam para a validacao e eficiencia do procedimento proposto. Palavras-chave: otimizacao, pontes, posicionamento dos apoios. OPTIMUM SUPPORT POSITIONS IN BRIDGES ABSTRACT This paper presents a study to determine the optimal support positions in bridges, as well as the optimal relation between the spans of beams, aiming both the reduction and the unifirmization of the efforts in these structures. The mathematical problem is formulated in order to minimize the maximum bending moments, taking the coordinate of each internal support as design variable. To take into account possible location limitations, size constraints are also considered in the formulation. The software developed based on this study determines the efforts in each support for load shifting along the structure by the usage of the Displacement Method, and the optimization is performed with a mathematical programming technique. The structures analyzed from the computational implementation of the idealized model point to the validation and efficiency of the proposed procedure. Keywords: optimization, bridges, support positions.

Simultaneous geometry and cross-section optimization of aluminum trusses

Purpose – Trusses constitute a fertile field to demonstrate the application of optimization techniques because of the possibility of several different configurations. Using such techniques allows the search for designs that minimize the use of material to safely comply with the imposed loads. Truss optimization can be classified into three categories: cross-section, shape, and topology. The purpose of this paper is to present a numerical and experimental study developed to minimize the weight of aluminum trusses, taking both the cross-sectional dimensions of the elements and the nodal coordinates as design variables. Design/methodology/approach – Initially, several numerical computer simulations were performed with an optimization program developed by combining the displacement method and a simulated annealing optimization method. Subsequently, two aluminum trusses were selected and built in order to validate the numerical results obtained. Findings – Experimental tests verified the excellent performance ...