No abstract

Most current structural design codes are based on the concept of limit states, that is, when a structure fails to meet one of its purposes, it is said that it has reached its limit state. In the design of reinforced concrete structures, the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS) must be checked. Therefore, this paper presents an optimization scheme for reinforced concrete plane frames, in which the objective is to minimize the cost of structures for three cases of constraints: the first is related to ULS and SLS; the second refers only to the ULS; and the third is related only to the SLS. Computational routines for checking limit states of beams and columns are implemented in MATLAB, following the requirements of the Brazilian code. Structural analyses are performed by using the MASTAN2 software, taking into account geometric nonlinearities and a simplified physical nonlinearity method. The objective function considers the cost of concrete, reinforcement and formwork, and the optimization problems are solved by genetic algorithms. Two numerical examples of frames are presented. Regarding the optimal characteristics related to each type of limit state, it is noted that the beams and columns tend to have larger and more reinforced cross sections in the case of the ULS. Even so, optimal structures related to the ULS often do not satisfy SLS and vice versa, which indicates that the optimal characteristics related to each limit state may be different. In addition, it is observed that the SLS is less restrictive than ULS.

RESUMO:A tomografia ultrassônica é uma técnica não destrutiva com grande potencial na avaliação da integridade de seções transversais de elementos de madeira. São várias as pesquisas que abordam a influência de diversos fatores como umidade, presença de fungos, entre outros na obtenção de tomogramas a partir da utilização de softwares e equipamentos comerciais projetados para este fim. A fundamentação matemática desta técnica, por outro lado, quando abordada, ocorre de uma forma simplificada. O objetivo desse trabalho é apresentar o processamento matemático envolvido na técnica de tomografia ultrassônica e assim permitir o desenvolvimento de uma ferramenta computacional própria. Resultados preliminares de detecção de imperfeições internas em uma peça de madeira a partir de uma ferramenta computacional, inicialmente desenvolvida, são apresentados e discutidos. Os resultados obtidos identificam a presença de imperfeições internas, e exibem a influência que a anisotropia da madeira exerce sobre a propagação dos pulsos ultrassônicos. MATHEMATICAL BASIS OF ULTRASONIC TOMOGRAPHY FOR INTEGRITY EVALUATION IN WOOD STRUCTURAL ELEMENTSABSTRACT: Ultrasonic tomography is a non-destructive technique used in the internal evaluation of wooden elements. Usually, research in this area lies in the influence of different factors in the obtained tomograms given by commercial software. The mathematical fundamentals of tomography are sparsely discussed. The aim of this study is to present the mathematical process, and thus to allow the implementing of a specific computational tool. This paper presents preliminary results for detecting internal flaws in wood specimens. The generated images identify the presence of the flaws, and show the influence of the material anisotropy in the ultrasonic pulse velocity.

No abstract

No abstract