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This thesis presents a study about the determination of the stress intensity factors in cracked sheets with riveted stiffeners. Stress intensity factors are determined with both analytical method and finite element method for different combination of rivet/stringer spacing and stringer to sheet stiffness ratio. Analytical part of the thesis is a replication of the original study of Poe which assumes rigid rivet connections with no stringer offset. In the analytical part, the whole systems of equations of Poe are re-derived, and it is shown that there are two typographical errors in the expressions for the calculation of the influence coefficients of the cracked sheet and the stringer. Major objective of the analytical part is to develop a computer code which calculates the variation of the normalized stress intensity factor with the crack length for any combination of rivet/stringer spacing and stringer to sheet stiffness ratio. Analytical part of the study also covers the effect of broken stiffener on the stress intensity factor of the cracked sheet. The stress intensity factors of stiffened cracked sheets are calculated by the finite element method by incorporating fastener flexibility and stringer offset. Finite element solutions are performed by Franc2D/L and Abaqus, and comparisons are made. The effect of geometry, fastener flexibility, and stringer offset on the stress intensity factors are studied by presenting normalized stress intensity factor versus crack length curves. Finally, as a case study a sample damage tolerant stiffened panel is designed according to FAR 25 safety criteria. Experiments are performed for determining mechanical and crack growth properties of Al 2124 which is used as the material in the case study. Present study showed that the most significant effect on the stress intensity factor is seen when stringer-cracked sheet offset is included in the analysis model.

Establishing dynamic characteristics of structures is a challenging area of research. The dynamic characteristics of structures, such as natural frequencies, modeshapes, response levels and damping characteristics play an important role in identifying the condition of the structures. The assumed modes method is a particular analytical method used to estimate the dynamic characteristics of a structure. However, the eigenfunctions used in the assumed mode method often led to ill-conditioning due to the presence of hyperbolic functions. Furthermore, a change in the boundary conditions of the system usually necessitates a change in the choice of assumed mode. In this thesis, a set of Alternative Admissible Functions (AAF), along with penalty functions, are used to obtain closed form solutions for an Euler-Bernoulli beam with various boundary conditions. A key advantage of the proposed approach is that the choice of AAF does not depend on the boundary conditions since the boundary conditions are modelled via penalty functions. The mathematical formulation is validated with different boundary conditions, Clamped-Free (CF), Simply-Supported (SS), and Clamped-Clamped (CC). A specific relation between the penalty function and the system parameters are established for CF, SS and CC boundary conditions to obtain appropriate values of penalties. Validation of results with the reported literature indicates excellent agreement when compared with closed-form Euler-Bernoulli beam values. The AAF approach with penalties is extended to a beam with a shallow crack to estimate the dynamic characteristics. The crack is modelled as a penalty function via a massless rotational spring. This model has the advantage of simplifying parametric studies, because of its discrete nature, allowing easy modification in the crack position and depth of the crack. Therefore, once the model is established, various practical applications may be performed without reformulation of the problem. Validation of results with the reported literature on beams with shallow cracks indicates the suitability of the proposed approach.

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Neste estudo, o novo algoritmo hibrido autoconfigurado PSOS (Particle Swarm Optimization - Simplex) para avaliação da integridade estrutural a partir de respostas dinâmicas é apresentado. A formulação da função objetivo para o problema de minimização definido emprega funções de resposta em freqüência e/ou dados modais do sistema. Uma nova estratégia para o controle dos parâmetros do algoritmo Particle Swarm Optimization (PSO), baseada no uso do método de Nelder - Mead é desenvolvida; conseqüentemente, a convergência do PSO fica independente dos parâmetros heurísticos e sua estabilidade e precisão são melhoradas. O método híbrido proposto teve melhor desempenho, nas diversas funções teste analisadas, quando comparado com os algoritmos simulated annealing, algoritmos genéticos e o PSO. São apresentados diversos problemas de detecção de dano, levando em conta os efeitos do ruído e da falta de dados experimentais. Em todos os casos, a posição e extensão do dano foram determinadas com sucesso. Finalmente, usando o PSOS, os parâmetros de um oscilador não linear (oscilador de Duffing) foram identificados. / In this study, a new auto configured Particle Swarm Optimization - Simplex algorithm for damage detection has been proposed. The formulation of the objective function for the minimization problem is based on the frequency response functions (FRFs) and the modal parameters of the system. A novel strategy for the control of the Particle Swarm Optimization (PSO) parameters based on the Nelder-Mead algorithm (Simplex method) is presented; consequently, the convergence of the PSOS becomes independent of the heuristic constants and its stability and accuracy are enhanced. The formulated hybrid method performs better in different benchmark functions than the Simulated Annealing (SA), the Genetic Algorithm (GA) and the basic PSO. Several damage identification problems, taking into consideration the effects of noisy and incomplete data, were studied. In these cases, the damage location and extent were determined successfully. Finally, using the PSOS, a non-linear oscillator (Duffing oscillator) was identified with good results.

<p>Mounds of fire-cracked stones is a typical Bronze Age monument for the region around lake Mälaren. They are usually, because of their content, interpreted as piles of rubbish. But as they often have kerbs, are situated on cemeteries and sometimes contain human bones, the traditional interpretation is not fully satisfactory.</p><p>The main focus of this essay is on the mounds of fire-cracked stones which contain human bones in the region north of lake Mälaren. With a detailed study of these, and a comparison with those without human bones, my aim is to get closer to an explanation why the human bones were deposited. The essay consist of a comp­ilation  of 98 excavated mounds and a database with various information gathered from excavation reports and archive documents.</p><p>With different kinds of osteological aspects taken in consideration, the study shows that human bones have been found in about a third of the mounds. The mounds with human bones more often have kerbs. The same types of artefacts are found both in mounds with and without human bones. A significant difference is that the mounds with human bones contain more categories of artefacts and sometimes even bronze. The study also shows that there is nothing that indicates that the bones were deposited after the primary use of the mound. The human bones could therefore had been deposited contemporary to the “rubbish”. To understand this phenomenon I strongly believe that the mounds no longer only can be interpreted as heaps of garbage.</p>

In this Thesis, the problem of the Free Vibrations Analysis of Doubly Stiffened Composite, Orthotropic and/or Isotropic, Base Plates or Panels (with Orthotropic Stiffening Plate Strips) is investigated. The composite plate or panel system is made of an Orthotropic and/or Isotropic Base Plate stiffened or reinforced by adhesively bonded Upper and Lower Orthotropic Stiffening Plate Strips. The plates are assumed to be the Mindlin Plates connected by relatively very thin adhesive layers. The general problem under study is considered in terms of three problems, namely Main PROBLEM I Main PROBLEM II and Main PROBLEM III. The theoretical formulation of the Main PROBLEMS is based on a First Order Shear Deformation Plate Theory (FSDPT) that is, in this case, the Mindlin Plate Theory. The entire composite system is assumed to have simple supports along the two opposite edges so that the Classical Levy&#039 / s Solutions can be applied in that direction. Thus, the transverse shear deformations and the rotary moments of inertia of plates are included in the formulation. The very thin, yet elastic deformable adhesive layers are considered as continua with transverse normal and shear stresses. The damping effects in the plates and the adhesive layers are neglected. The sets of the systems of equations of the Mindlin Plate Theory are reduced to a set of the Governing System of First Order Ordinary Differential Equations in the state vector form. The sets of the Governing System for each Main PROBLEM constitute a Two-Point Boundary Value Problem in the y-direction which is taken along the length of the plates. Then, the system is solved by the Modified Transfer Matrix Method (with Interpolation Polynomials and/or Chebyshev Polynomials)which is a relatively semi-analytical and numerical technique. The numerical results and important parametric studies of the natural modes and the corresponding frequencies of the composite system are presented.

This thesis deals with issues relating to the cosmological dimensions of landscapes, the cultural construction of age and the long-term changes in passage rituals and mortuary practices in the Bronze Age societies of Södermanland in East Central Sweden. A gender perspective forms the underlying theoretical framework, while the study as a whole is particularly interested in power relations between generations as an impetus for societal change. Burials from cairns and cemeteries, as well as heaps of fire-cracked stones, rock-carvings and ritual hoards from two Bronze Age Landscapes in Södermanland are used as examples and to illustrate the interpretations presented in this study. It is proposed that perceptions of landscapes and cosmology were created by placing cairns and stone settings at liminal places or boundaries in the landscape, while heaps of fire-cracked stones were situated at focal points. Places where rock-carvings are found, nearby rapids or on islands along river courses, are interpreted as birth-places, and stem from origin myths about the birth of the first humans at these sites. It is proposed that birth, life and death as cosmological principles may be perceived in the landscape and are related to different kinds of waters. In addition, it is suggested that the cultural construction of age is expressed in spatial terms where adults - both men and women - with special abilities and esoteric knowledge related to passage rituals, were buried in cairns. Infants, whose relationship with these adults was special, were instead buried in the heaps of fire-cracked stones. It is also considered that, among other things, the absence of swords in burials implies that the societies of East Central Sweden probably had a social organization that was distinct from the societies of southern Scandinavia. Regarding long-term changes in ritual practices it is suggested that ritual tools used in mortuary practices change from flint daggers in the Late Neolithic, to razors and tweezers during the Bronze Age. Further changes occurred in the Late Bronze Age, when pins were introduced into the ritual practices. Regarding age and gender, osteological estimates show that both adult men and women participated in passage rituals. With the transition to pins we also see changes in who dealt with passage rituals and it is rather young women who were responsible for this sphere in the later period. As children also become visible - both in burials and at rock-carving sites – during the Late Bronze Age, this is interpreted as signalling shifts in power relations between genders and generations in favour of women and younger people.

Mounds of fire-cracked stones is a typical Bronze Age monument for the region around lake Mälaren. They are usually, because of their content, interpreted as piles of rubbish. But as they often have kerbs, are situated on cemeteries and sometimes contain human bones, the traditional interpretation is not fully satisfactory. The main focus of this essay is on the mounds of fire-cracked stones which contain human bones in the region north of lake Mälaren. With a detailed study of these, and a comparison with those without human bones, my aim is to get closer to an explanation why the human bones were deposited. The essay consist of a comp­ilation  of 98 excavated mounds and a database with various information gathered from excavation reports and archive documents. With different kinds of osteological aspects taken in consideration, the study shows that human bones have been found in about a third of the mounds. The mounds with human bones more often have kerbs. The same types of artefacts are found both in mounds with and without human bones. A significant difference is that the mounds with human bones contain more categories of artefacts and sometimes even bronze. The study also shows that there is nothing that indicates that the bones were deposited after the primary use of the mound. The human bones could therefore had been deposited contemporary to the “rubbish”. To understand this phenomenon I strongly believe that the mounds no longer only can be interpreted as heaps of garbage.

Orientador: Gilberto Pechoto de Melo / Resumo: No decorrer dos anos, alguns métodos de manutenção têm sido desenvolvidos para evitar que falhas em estruturas e maquinários possam ocorrer e desencadear paradas inesperadas ou desnecessárias. Os observadores de estado podem reconstruir os estados não medidos do sistema, desde que o mesmo seja observável, tornando possível, desta forma, estimar as medidas nos pontos de difícil acesso. A técnica dos observadores de estado consiste em desenvolver um modelo para o sistema em análise e comparar a estimativa da saída com a saída medida, a diferença entre os dois sinais presentes resulta em um resíduo que é utilizado para análise. Neste trabalho foi montado um banco de observadores associado a um modelo de trinca em placa de Kirchhoff de modo a acompanhar o progresso da mesma. Foram analisados quatro sistemas mecânicos contendo placas, sendo estes um sistema computacional de placa sobre elementos de molas e amortecimento, um sistema computacional de placa engastada livre com ausência ou presença de trinca, um sistema experimental de placa engastada livre com ausência ou presença de entalhe e um sistema experimental de placa engastada livre com ausência ou presença de massa extra. Novamente, o banco de observadores é utilizado para detecção da falha na estrutura. Os resultados obtidos através de simulações computacionais em uma viga engastada discretizada pela técnica dos elementos finitos e as análises experimentais realizadas foram bastante satisfatórios, validando a metodologia d... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre