Abstract

This paper presents an optimal design of three dimensional multi-story reinforced concrete structures using recently developed meta-heuristic algorithms, namely; the charged system search and the enhanced charged system search. The design is based on the ACI 318-05 code and loadings are based on ASCE7-05. Analysis of the structures is performed by the standard stiffness method. All members are subjected to biaxial moments and axial loads. Pre-determined sections are assumed for beams and columns, and the corresponding interaction curves are utilized to check whether the selected section for each member is acceptable. The objective function is taken as the weight of the structure, and constraints consist of the slenderness of compression members, the maximum allowable drift of the structure and the natural frequency of the structure. It should be mentioned that second order effects are also considered and that the end moments of the columns are magnified when needed. First, a 7-story frame with 3 spans is considered and optimized. Then, a sensitivity analysis is performed by optimal design of nine frames having 3 stories and 2 spans. In each story, different span lengths and loading conditions are assumed, and the results are compared.

Abstract

By the integral finite element analysis of elasto-plastic constitutive relationship, the process of crack formation and development of the T-shaped frame joint in reinforced concrete and its stress distribution under monotonic and low-cycle repeated loading were studied . The nonlinear constitutive relation of concrete and the failure mechanism of T-shaped column joint were further discussed. The work of this paper provides a reference to the design and construction of T-shaped column joints. 

Abstract

The paper describes a finite element damage model for non linear analysis of concrete or reinforced structures. It is show how can be effectively used to predict local and global damage up to structural failure. Examples of applications of the model to the analysis of different structures such as a nuclear containment shell, a housing building and the domes of St. Mark Basilica are presented.

Abstract

O Modelo de Bielas e Tirantes pode ser uma excelente alternativa para o dimensionamento de elementos estruturais em concreto armado submetidos a estado plano de tensão e para regiões que apresentem descontinuidade de ordem geométrica ou estática, substituindo procedimentos empíricos por uma metodologia racional de projeto. Para tornar a concepção do modelo menos dependente da experiência do projetista, o presente artigo tem como objetivo aliar a técnica de otimização topológica ESO (Evolutionary Structural Optimization) ao Método dos Elementos Finitos para geração automática dos modelos de bielas e tirantes. O critério de evolução do método de otimização topológica adotado considera a eliminação de elementos menos solicitados em termos de tensão, a partir de uma análise elástico-linear. Nesse contexto, é possível obter soluções otimizadas de problemas complexos envolvendo o concreto estrutural. São apresentados três exemplos numéricos para comprovação e validação das formulações e técnicas implementadas,  cujos modelos de bielas e tirantes obtidos apresentam boa concordância em relação às respostas encontradas em trabalhos científicos precursores sobre o tema.

Abstract

The present work aims to define formally the method termed as \textit{``Idealized Smeared Reinforcement'' (ISR)} for optimization in the design of reinforcing steel in concrete structures, its boundaries, background and potentials. Such method has been extensively used implicitly in many different studies of reinforced concrete structures related with optimization and mechanical structural behaviour, but it has not yet been formally established as a method itself even though it represents a great solution approach when designing optimally concrete sections, which is a tendency so vital nowadays for sustainability in construction projects. A general survey of such method of the ISR will be presented on in this document, presenting relevant background research related to the use of the method and optimization of reinforcing steel in general for concrete structures, thereafter proposals of different optimization methods, both classical optimization and meta-heuristic methods will be regarded as possible approaches to apply the ISR, specifically Gradient Descent Optimization methods when one variable for the ISR is considered and meta-heuristics for more than one variable involved given their versatility and flexibility to adapt to different problems, particularly the Particle Swarm Optimization PSO method and the Genetic Algorithm GA. At the end, these solution approaches for the application of the ISR method will be compared for the testing of rectangular solid geometries with different analysis parameters in order to show how adaptable and feasible such ISR method might be using a proper optimization algorithm and analysis for its approach when designing reinforcing steel.

Abstract

The present work presents  numerical methods to evaluate the global dynamic response of railway bridges.the structural response of an existing reinforced concrete railway bridge is obtained via the Modal Superposition Method, using a finite element three-dimensional numerical model. The cracking stiffness, and consequently loss of flexural stiffness, is considered indirectly in the numerical modeling of the bridge and the dynamic responses, in terms of the displacement histories, they are compared with experimental results, obtained in the short-term monitoring of the structure. The results predicted by the model show a satisfactory convergence with the experimental responses. The study showed that the stiffness penalty method significantly influences the dynamic response and, although it is a linear analysis, which considers physical nonlinearity approximately, it can be used to obtain convergent responses with a low computational cost.

Abstract

Abstract