Sebastião Arthur Lopes de Andrade

A Neural Network System for Patch Load Prediction

This work presents the application of Artificial Neural Networks to forecast the ultimate resistance of steel beams subjected to patch loads. A single design formula for this structural engineering problem is very difficult to obtain, due to the influence of several independent parameters. On the other hand, creating new experimental data in laboratory is very time consuming and expensive. This work demonstrates that new data can be obtained from a neural network system composed of four Back Propagation networks. The proposed neural network system presented a maximum error value lower than 15%, while the existing formulas errors were over 20%. These results confirmed the possibility of using this methodology to generate new trustworthy data. These data, coupled with experiments found in the literature, can surely help the development of a more consistent and accurate design formula.

Vibration analysis of orthotropic composite floors for human rhythmic activities

Competitive world market trends have long been forcing structural engineers to develop minimum weight and labour cost solutions. A direct consequence of this design philosophy is a considerable increase in problems related to unwanted floor vibrations. This phenomenon is very frequent in a wide range of structures subjected to dynamical loads. The main objective of this paper is to evaluate an orthotropic solution for composite floors subjected to dynamical actions such as rhythmical activities arising from gymnastics, musical and sports events and ballroom dances. The proposed analysis methodology considers the investigation of the dynamic behaviour of a building floor made with a composite slab system with steel beams and an incorporated steel deck. The results indicated that the investigated composite floor violates the vibration serviceability limit state, but satisfied the human comfort criteria.

Numerical and Experimental Assessment of Stainless and Carbon Bolted Tensioned Members with Staggered Bolts

Current stainless steel design codes, like the Eurocode 3, part 1.4, (2006), are still largely based on analogies with carbon steel structural behavior. The net section rupture represents one of the ultimate limit states usually verified for structural elements submitted to normal tension stress. An investigation aiming to evaluate the tension capacity of carbon and stainless steel bolted structural elements was performed and in this article, the results are discussed and compared in terms of stress distribution, and force-displacement curves, among others. The result assessment was done by comparisons to the Eurocode 3 (2003) provisions for carbon and stainless steels. The investigation indicated that when stainless steel is used in certain structural engineering applications like joints under tension forces, the current design criteria based on deformation limits need to be re-evaluated, especially due to the differences in the yields for ultimate deformation and stress ratios.

Non-Linear Dynamical Response of Steel Portal Frames with Semi-Rigid Connections

Traditionally, the steel portal frame design assumes that beam-to-column joints are rigid or pinned. Rigid joints, where no relative rotations occur between the connected members, transfer not only substantial bending moments, but also shear and axial forces. Alternatively, pinned joints are characterised by an almost free rotation movement between the connected elements preventing the bending moment transmission. Despite these facts, it is largely recognised that the great majority of joints does not exhibit such idealised behaviour. These joints, called semi-rigid, should be designed according to their actual structural behaviour. Considering all these facts one of the main objectives of this investigation is to propose a modelling strategy to represent the dynamical behaviour of semirigid joints under dynamic actions. The developed finite element model included geometric nonlinearities and considered the influence of non-linear and hysteretic joint stiffness. The updated Lagrangean formulation is used to model the geometric non-linearity. The mathematical model calibration was made based on comparisons to semi-rigid tests and other numerical models [1],[2] and proving to be in accordance to them. However, it must be emphasized that cautions should be taken on the direct use of the results in structural design. The main reasons for this affirmative are related to the occurrence of very important distortions due to the consideration of the semi-rigid joints geometric non-linearity effects on the steel portal frames dynamical response.

Finite Element Modelling

The objective of this chapter is to present the necessary steps for the development of numerical models based on finite element method and the main aspects related to results interpretation of numerical models used in steel and composite structures simulation. It should be once more emphasised that the present book was conceived from an idea where the most important aspects of numerical modelling are introduced, as computer simulations of practical cases of numerical experiments are presented. Initially, some aspects and general questions will be addressed to elucidate key points of numerical modelling planning to ensure the validity and reliability of the performed computer simulations. The numerical modelling described in this chapter is based on the finite element method, traditionally adopted by structural engineers to simulate complex problems that usually cannot be solved with the suitable accuracy with mechanical, or simple analytical models. In summary this chapter aimed to introduce the necessary steps for the correct design, implementation, and interpretation of numerical model results of using the finite element method for the simulation of the response of steel and composite structures. These ideas are discussed throughout a series of numerical simulations depicting nonlinear responses focusing on their main details and restrictions in terms of boundary conditions, major difficulties, solution strategies, and methods to overcome convergence difficulties.

Computational Intelligence Modelling

The development of new materials and faster computing processes opened new frontier for the conception and development of new and audacious designs that will set the trend for the future 21th century structures. Various methods, techniques, and procedures have been, and still are being, used to improve and design these structures like optimisation processes, numerical modelling systems involving non-linear finite element analysis, etc. Concurrently, the last decade of the 20th century has been related to a large improvement and development of the so-called Computational Intelligent Techniques. These techniques are computational systems that try to mimic human behaviour, such as perception, reasoning, learning, evolution, and adaptation. They involve Neural Networks, Genetic Algorithm, Fuzzy Logic, and Hybrid Intelligent Systems , such as Neuro-Fuzzy, Neuro-Genetic, and Fuzzy-Genetic models .

Estudo do conforto humano em pisos mistos (aço-concreto)

The competitive trends of the civil engineering market have long been forcing structural engineers to develop minimum weight and labor cost solutions. A direct consequence of this new design trend is a considerable increase in floor vibration problems. The main objective of this paper is to present an analysis methodology to evaluate the composite floors human comfort criteria, considering a more realistic loading model incorporating the dynamic effects induced by people walking. The investigated models were based on floors, with main spans varying from 5m to 10m. Based on an extensive parametric study the composite floors dynamic response was obtained and compared to limiting values proposed by several authors and design standards. The results of the present study indicated that the walking loads could induce the composite floors to reach significant vibration levels implying and violating the human comfort criteria.