Dissertations / Theses on the topic 'Structural'

Les blocs protéiques (BP) constituent un alphabet structural qui permettent une bonne approximation du squelette carbonnée des protéines et la compression de l'information 3D en 1D. Leur utilisation a permis d'appréhender sous un nouvel angle la structure des protéines. Cette thèse explore de nouvelles applications des BP pour l'analyse des structures des protéines, leur prédiction et la reconnaissance de leurs repliements. Dans un premier temps, nous utilisons les BP pour une caractérisation fine des régions variables dans les alignements structuraux de protéines homologues. Ces régions peuvent néanmoins présenter des similarités importantes en terme de conformation. Leur caractérisation a permis de les distinguer des régions dont les conformations sont différentes. Nous montrons aussi que les variations intrinsèques de certaines régions comme les boucles au sein d’une protéine ne sont pas corrélées aux différences de conformation observées dans les régions équivalentes entre protéines homologues. Dans une deuxième partie, nous analysons la relation séquence-structure à l'aide de BP par le biais d'une base de données de pentapeptides issus des structures des protéines. Celle-ci a servi de base pour la mise en place d'outils pour la prédiction du squelette carbonnée des protéines (PB-kPRED) et de sa plasticité (PB-SVindex). Nous exposons comment ces prédictions permettent la reconnaissance du repliement des protéines avec un certain succès et l'identification de probables points chauds structuraux et fonctionnels. En dernière partie, nous présentons un nouvel algorithme (FoRSA) pour la reconnaissance du repliement des protéines à l'aide des BP. Cet algorithme s'appuie sur le calcul de la probabilité conditionnelle qu'une séquence adopte un repliement donné et a été testé avec succès sur des protéines tirées de CASP10. Nous montrons que FoRSA peut être utilisé pour l'annotation structurale rapide de génomes entiers
Analysis of protein structures using structural alphabets has provided new insights into protein function and evolution. We have used a structural alphabet called proteins blocks (PBs) which efficiently approximates protein backbone and allows abstraction of 3D protein structures into 1D PB sequences. This thesis describes applications of PBs for protein structure analysis, prediction and fold recognition. First, PBs were used to provide a refined view of structurally variable regions (SVRs) in homologous proteins in terms of conformationally similar and dissimilar SVRs in which were compiled a database of structural alignments (DoSA). We also show that the inherent conformational variations in loop regions are not correlated to corresponding conformational differences in their homologues. Second, to further analyze sequence-structure relationships in terms of PBs and other structural features, we have set up a database of pentapeptides derived from protein structures. This served as a basis for the knowledge-based prediction of local protein structure in terms of PB sequences (PB-kPRED) and of local structure plasticity (PB-SVindex). We demonstrate the successful applications of PB-kPRED for fold recognition and explored possible identification of structural and functional hotspots in proteins using PB-SVindex. Finally, an algorithm for fold recognition using a structural alphabet (FoRSA) based on calculation of conditional probability of sequence-structure compatibility was developed. This new threading method has been successfully benchmarked on a test dataset from CASP10 targets. We further demonstrate the application of FoRSA for fast structural annotations of genomes

Uncertainty involved in the safe and comfort design of the structures is a major concern of civil engineers. Traditionally, the uncertainty has been overcome by utilizing various and relatively large safety factors for loads and structural properties. As a result in conventional design of for example tall buildings, the designed structural elements have unnecessary dimensions that sometimes are more than double of the ones needed to resist normal loads. On the other hand the requirements for strength and safety and comfort can be conflicting. Consequently, an alternative approach for design of the structures may be of great interest in design of safe and comfort structures that also offers economical advantages. Recently, there has been growing interest among the researchers in the concept of structural control as an alternative or complementary approach to the existing approaches of structural design. A few buildings have been designed and built based on this concept. The concept is to utilize a device for applying a force (known as control force) to encounter the effects of disturbing forces like earthquake force. However, the concept still has not found its rightful place among the practical engineers and more research is needed on the subject. One of the main problems in structural control is to find a proper algorithm for determining the optimum control force that should be applied to the structure. The investigation reported in this thesis is concerned with the application of active control to civil engineering structures. From the literature on control theory. (Particularly literature on the control of civil engineering structures) problems faced in application of control theory were identified and classified into two categories: 1) problems common to control of all dynamical systems, and 2) problems which are specially important in control of civil engineering structures. It was concluded that while many control algorithms are suitable for control of dynamical systems, considering the special problems in controlling civil structures and considering the unique future of structural control, many otherwise useful control algorithms face practical problems in application to civil structures. Consequently a set of criteria were set for judging the suitability of the control algorithms for use in control of civil engineering structures. Various types of existing control algorithms were investigated and finally it was concluded that predictive optimal control algorithms possess good characteristics for purpose of control of civil engineering structures. Among predictive control algorithms, those that use ARMA stochastic models for predicting the ground acceleration are better fitted to the structural control environment because all the past measured excitation is used to estimate the trends of the excitation for making qualified guesses about its coming values. However, existing ARMA based predictive algorithms are devised specially for earthquake and require on-line measurement of the external disturbing load which is not possible for dynamic loads like wind or blast. So, the algorithms are not suitable for tall buildings that experience both earthquake and wind loads during their life. Consequently, it was decided to establish a new closed loop predictive optimal control based on ARMA models as the first phase of the study. In this phase it was initially established that ARMA models are capable of predicting response of a linear SDOF system to the earthquake excitation a few steps ahead. The results of the predictions encouraged a search for finding a new closed loop optimal predictive control algorithm for linear SDOF structures based on prediction of the response by ARMA models. The second part of phase I, was devoted to developing and testing the proposed algorithm The new developed algorithm is different from other ARMA based optimal controls since it uses ARMA models for prediction of the structure response while existing algorithms predict the input excitation. Modeling the structure response as an AR or ARMA stochastic process is an effective mean for prediction of the structure response while avoiding measurement of the input excitation. ARMA models used in the algorithm enables it to avoid or reduce the time delay effect by predicting the structure response a few steps ahead. Being a closed loop control, the algorithm is suitable for all structural control conditions and can be used in a single control mechanism for vibration control of tall buildings against wind, earthquake or other random dynamic loads. Consequently the standby time is less than that for existing ARMA based algorithms devised only for earthquakes. This makes the control mechanism more reliable. The proposed algorithm utilizes and combines two different mathematical models. First model is an ARMA model representing the environment and the structure as a single system subjected to the unknown random excitation and the second model is a linear SDOF system which represents the structure subjected to a known past history of the applied control force only. The principle of superposition is then used to combine the results of these two models to predict the total response of the structure as a function of the control force. By using the predicted responses, the minimization of the performance index with respect to the control force is carried out for finding the optimal control force. As phase II, the proposed predictive control algorithm was extended to structures that are more complicated than linear SDOF structures. Initially, the algorithm was extended to linear MDOF structures. Although, the development of the algorithm for MDOF structures was relatively straightforward, during testing of the algorithm, it was found that prediction of the response by ARMA models can not be done as was done for SDOF case. In the SDOF case each of the two components of the state vector (i.e. displacement and velocity) was treated separately as an ARMA stochastic process. However, applying the same approach to each component of the state vector of a MDOF structure did not yield satisfactory results in prediction of the response. Considering the whole state vector as a multi-variable ARMA stochastic vector process yielded the desired results in predicting the response a few steps ahead. In the second part of this phase, the algorithm was extended to non-linear MDOF structures. Since the algorithm had been developed based on the principle of superposition, it was not possible to directly extend the algorithm to non-linear systems. Instead, some generalized response was defined. Then credibility of the ARMA models in predicting the generalized response was verified. Based on this credibility, the algorithm was extended for non-linear MDOF structures. Also in phase II, the stability of a controlled MDOF structure was proved. Both internal and external stability of the system were described and verified. In phase III, some problems of special interest, i.e. soil-structure interaction and control time delay, were investigated and compensated for in the framework of the developed predictive optimal control. In first part of phase III soil-structure interaction was studied. The half-space solution of the SSI effect leads to a frequency dependent representation of the structure-footing system, which is not fit for control purpose. Consequently an equivalent frequency independent system was proposed and defined as a system whose frequency response is equal to the original structure -footing system in the mean squares sense. This equivalent frequency independent system then was used in the control algorithm. In the second part of this phase, an analytical approach was used to tackle the time delay phenomenon in the context of the predictive algorithm described in previous chapters. A generalized performance index was defined considering time delay. Minimization of the generalized performance index resulted into a modified version of the algorithm in which time delay is compensated explicitly. Unlike the time delay compensation technique used in the previous phases of this investigation, which restricts time delay to be an integer multiplier of the sampling period, the modified algorithm allows time delay to be any non-negative number. However, the two approaches produce the same results if time delay is an integer multiplier of the sampling period. For evaluating the proposed algorithm and comparing it with other algorithms, several numerical simulations were carried during the research by using MATLAB and its toolboxes. A few interesting results of these simulations are enumerated below: ARM A models are able to predict the response of both linear and non-linear structures to random inputs such as earthquakes. The proposed predictive optimal control based on ARMA models has produced better results in the context of reducing velocity, displacement, total energy and operational cost compared to classic optimal control. Proposed active control algorithm is very effective in increasing safety and comfort. Its performance is not affected much by errors in the estimation of system parameters (e.g. damping). The effect of soil-structure interaction on the response to control force is considerable. Ignoring SSI will cause a significant change in the magnitude of the frequency response and a shift in the frequencies of the maximum response (resonant frequencies). Compensating the time delay effect by the modified version of the proposed algorithm will improve the performance of the control system in achieving the control goal and reduction of the structural response.

Uncertainty involved in the safe and comfort design of the structures is a major concern of civil engineers. Traditionally, the uncertainty has been overcome by utilizing various and relatively large safety factors for loads and structural properties. As a result in conventional design of for example tall buildings, the designed structural elements have unnecessary dimensions that sometimes are more than double of the ones needed to resist normal loads. On the other hand the requirements for strength and safety and comfort can be conflicting. Consequently, an alternative approach for design of the structures may be of great interest in design of safe and comfort structures that also offers economical advantages. Recently, there has been growing interest among the researchers in the concept of structural control as an alternative or complementary approach to the existing approaches of structural design. A few buildings have been designed and built based on this concept. The concept is to utilize a device for applying a force (known as control force) to encounter the effects of disturbing forces like earthquake force. However, the concept still has not found its rightful place among the practical engineers and more research is needed on the subject. One of the main problems in structural control is to find a proper algorithm for determining the optimum control force that should be applied to the structure. The investigation reported in this thesis is concerned with the application of active control to civil engineering structures. From the literature on control theory. (Particularly literature on the control of civil engineering structures) problems faced in application of control theory were identified and classified into two categories: 1) problems common to control of all dynamical systems, and 2) problems which are specially important in control of civil engineering structures. It was concluded that while many control algorithms are suitable for control of dynamical systems, considering the special problems in controlling civil structures and considering the unique future of structural control, many otherwise useful control algorithms face practical problems in application to civil structures. Consequently a set of criteria were set for judging the suitability of the control algorithms for use in control of civil engineering structures. Various types of existing control algorithms were investigated and finally it was concluded that predictive optimal control algorithms possess good characteristics for purpose of control of civil engineering structures. Among predictive control algorithms, those that use ARMA stochastic models for predicting the ground acceleration are better fitted to the structural control environment because all the past measured excitation is used to estimate the trends of the excitation for making qualified guesses about its coming values. However, existing ARMA based predictive algorithms are devised specially for earthquake and require on-line measurement of the external disturbing load which is not possible for dynamic loads like wind or blast. So, the algorithms are not suitable for tall buildings that experience both earthquake and wind loads during their life. Consequently, it was decided to establish a new closed loop predictive optimal control based on ARMA models as the first phase of the study. In this phase it was initially established that ARMA models are capable of predicting response of a linear SDOF system to the earthquake excitation a few steps ahead. The results of the predictions encouraged a search for finding a new closed loop optimal predictive control algorithm for linear SDOF structures based on prediction of the response by ARMA models. The second part of phase I, was devoted to developing and testing the proposed algorithm The new developed algorithm is different from other ARMA based optimal controls since it uses ARMA models for prediction of the structure response while existing algorithms predict the input excitation. Modeling the structure response as an AR or ARMA stochastic process is an effective mean for prediction of the structure response while avoiding measurement of the input excitation. ARMA models used in the algorithm enables it to avoid or reduce the time delay effect by predicting the structure response a few steps ahead. Being a closed loop control, the algorithm is suitable for all structural control conditions and can be used in a single control mechanism for vibration control of tall buildings against wind, earthquake or other random dynamic loads. Consequently the standby time is less than that for existing ARMA based algorithms devised only for earthquakes. This makes the control mechanism more reliable. The proposed algorithm utilizes and combines two different mathematical models. First model is an ARMA model representing the environment and the structure as a single system subjected to the unknown random excitation and the second model is a linear SDOF system which represents the structure subjected to a known past history of the applied control force only. The principle of superposition is then used to combine the results of these two models to predict the total response of the structure as a function of the control force. By using the predicted responses, the minimization of the performance index with respect to the control force is carried out for finding the optimal control force. As phase II, the proposed predictive control algorithm was extended to structures that are more complicated than linear SDOF structures. Initially, the algorithm was extended to linear MDOF structures. Although, the development of the algorithm for MDOF structures was relatively straightforward, during testing of the algorithm, it was found that prediction of the response by ARMA models can not be done as was done for SDOF case. In the SDOF case each of the two components of the state vector (i.e. displacement and velocity) was treated separately as an ARMA stochastic process. However, applying the same approach to each component of the state vector of a MDOF structure did not yield satisfactory results in prediction of the response. Considering the whole state vector as a multi-variable ARMA stochastic vector process yielded the desired results in predicting the response a few steps ahead. In the second part of this phase, the algorithm was extended to non-linear MDOF structures. Since the algorithm had been developed based on the principle of superposition, it was not possible to directly extend the algorithm to non-linear systems. Instead, some generalized response was defined. Then credibility of the ARMA models in predicting the generalized response was verified. Based on this credibility, the algorithm was extended for non-linear MDOF structures. Also in phase II, the stability of a controlled MDOF structure was proved. Both internal and external stability of the system were described and verified. In phase III, some problems of special interest, i.e. soil-structure interaction and control time delay, were investigated and compensated for in the framework of the developed predictive optimal control. In first part of phase III soil-structure interaction was studied. The half-space solution of the SSI effect leads to a frequency dependent representation of the structure-footing system, which is not fit for control purpose. Consequently an equivalent frequency independent system was proposed and defined as a system whose frequency response is equal to the original structure -footing system in the mean squares sense. This equivalent frequency independent system then was used in the control algorithm. In the second part of this phase, an analytical approach was used to tackle the time delay phenomenon in the context of the predictive algorithm described in previous chapters. A generalized performance index was defined considering time delay. Minimization of the generalized performance index resulted into a modified version of the algorithm in which time delay is compensated explicitly. Unlike the time delay compensation technique used in the previous phases of this investigation, which restricts time delay to be an integer multiplier of the sampling period, the modified algorithm allows time delay to be any non-negative number. However, the two approaches produce the same results if time delay is an integer multiplier of the sampling period. For evaluating the proposed algorithm and comparing it with other algorithms, several numerical simulations were carried during the research by using MATLAB and its toolboxes. A few interesting results of these simulations are enumerated below: ARM A models are able to predict the response of both linear and non-linear structures to random inputs such as earthquakes. The proposed predictive optimal control based on ARMA models has produced better results in the context of reducing velocity, displacement, total energy and operational cost compared to classic optimal control. Proposed active control algorithm is very effective in increasing safety and comfort. Its performance is not affected much by errors in the estimation of system parameters (e.g. damping). The effect of soil-structure interaction on the response to control force is considerable. Ignoring SSI will cause a significant change in the magnitude of the frequency response and a shift in the frequencies of the maximum response (resonant frequencies). Compensating the time delay effect by the modified version of the proposed algorithm will improve the performance of the control system in achieving the control goal and reduction of the structural response.

The simulation of diffractive optical structures allows for the efficient testing of a large number of structures without having to actually fabricate these devices. Various forms of analysis of these structures have been done through computer programs in the past. However, programs that can actually design a structure to perform a given task are very limited in scope. Optimization of a structure can be a task that is very processor time intensive, particularly if the optimization space has many dimensions. This thesis describes the creation of a computer program that is able to find an optimal structure while maintaining a low-dimensional search space, thus greatly reducing the processor time required to find the solution. The program can design the optimal structure for a wide variety of planar optical devices that conform to the weakly-guiding approximation with an efficient code that incorporates the low-dimensional search space concept. This work is the first use of an electromagnetic field solver inside of an optimization loop for the design of an optimized diffractive-optic structure.

The assumptions encountered during the analysis and design of civil engineering structures lead to a difference in the structural behavior between calculations based models and real structures. Moreover, the recent approach in civil engineering nowadays is to rely on the performance-based design approaches, which give more importance for durability, serviceability limit states, and maintenance.Structural identification (St-Id) approach was utilized to bridge the gap between the real structure and the model. The St-Id procedure can be utilized to evaluate the structures health, damage detection, and efficiency. Despite the enormous developments in parametric time-domain identification methods, their relative merits and performance as correlated to the vibrating structures are still incomplete due to the lack of comparative studies under various test conditions and the lack of extended applications and verification of these methods with real-life data.This licentiate thesis focuses on the applications of the parametric models and non-parametric models of the System Identification approach to assist in a better understanding of their potentials, while proposing a novel strategy by combining this approach with the utilization of the Singular Value Decomposition (SVD) and the Complex Mode Indicator Function (CMIF) curves based techniques in the damage detection of structures.In this work, the problems of identification of the vertical frequencies of the top storey in a multi-storey¸ building prefabricated from reinforced concrete in Stockholm, and the existence of damage and damage locations for a bench mark steel frame are investigated. Moreover, the non-parametric structural identification approach to investigate the amount of variations in the modal characteristics (frequency, damping, and modes shapes) for a railway steel bridge will be presented.
Godkänd; 2014; 20141023 (taredr); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Tarek Edrees Saaed Ämne: Konstruktionsteknik/Structural Engineering Uppsats: Structural Identification of Civil Engineering Structures Examinator: Professor Jan-Erik Jonasson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Forskare Andreas Andersson, Brobyggnad inklusive Stålbyggnad, Kungliga Tekniska Högskolan Tid: Torsdag den 20 november 2014 kl 10:00 Plats: F1031, Luleå tekniska universitet

This DEng thesis consists of 83 articles containing research material on the stability of thin-walled structural members and systems with emphasis on metal structures. Metal structures are used widely in the construction industry. They include structural members and frames made from rolled and fabricated steel, cold-formed steel, stainless steel and aluminium. Common to these products is the desire to minimise the cross-sectional area to reduce weight and cost. Structural cross-sections are therefore thin-walled and prone to buckling, and an overriding consideration in the design of metal structures is to account for buckling in determining the strength of sections, members and frames. Specifically, the thesis is concerned with determining the reduction in buckling capacity and strength of structural members and frames caused by cross-sectional buckling and material softening. The thesis presents research under the headings Stainless Steel Structures - Hollow Sections, covering tubular columns, beams and welded connections; Stainless Steel Structures - Open Sections, addressing the effect of distortional buckling and interaction buckling on the design of stainless steel columns and beams; Analysis of Locally Buckled Members and Frames, describing a theory to determine the buckling loads of locally and/or distortionally buckled members and frames; Behaviour and Design of Members and Sections Composed Solely or Predominantly from Unstiffened Elements, outlining analytical, numerical and experimental research to advance the understanding of the behaviour and design of singly symmetric cross-sections made up entirely or predominantly from plate elements, including angle sections, T-sections and plain channel sections; Cold-formed Steel Structural Systems, describing numerical and experimental investigations of steel storage racks including selective and drive-in racking systems; and System-based Design of Steel Structures, developing a general framework for designing steel structural framing systems by advanced analysis, termed the Direct Design Method. The thesis also highlights the implementation of the research outcomes in national and international specifications for the design of steel, cold-formed steel and stainless steel structures.

Les modèles géologiques sont couramment utilisés pour estimer les ressources souterraines, pour faire des simulations numériques, et pour évaluer les risques naturels ; il est donc important que les modèles géologiques représentent la géométrie des objets géologiques de façon précise. La première étape pour construire un modèle géologique consiste souvent à interpréter des surfaces structurales, telles que les failles et horizons, à partir d'une image sismique ; les objets géologiques identifiés sont ensuite utilisés pour construire le modèle géologique par des méthodes d'interpolation. Les modèles géologiques construits de cette façon héritent donc les incertitudes d'interprétation car une image sismique peut souvent supporter plusieurs interprétations structurales. Dans ce manuscrit, j'étudie le problème de réduire les incertitudes d'interprétation à l'aide des données sismiques. Particulièrement, j'étudie le problème de déterminer, à l'aide des données sismiques, quels modèles sont plus probables que d'autres dans un ensemble des modèles géologiques cohérents. Ce problème sera connu par la suite comme "le problème d'évaluation des modèles géologiques par données sismiques". J'introduis et formalise ce problème. Je propose de le résoudre par génération des données sismiques synthétiques pour chaque interprétation structurale dans un premier temps, ensuite d'utiliser ces données synthétiques pour calculer la fonction-objectif pour chaque interprétation ; cela permet de classer les différentes interprétations structurales. La difficulté majeure d'évaluer les modèles structuraux à l'aide des données sismiques consiste à proposer des fonctions-objectifs adéquates. Je propose un ensemble de conditions qui doivent être satisfaites par la fonction-objectif pour une évaluation réussie des modèles structuraux à l'aide des données sismiques. Ces conditions imposées à la fonction-objectif peuvent, en principe, être satisfaites en utilisant les données sismiques de surface (« surface seismic data »). Cependant, en pratique il reste tout de même difficile de proposer et de calculer des fonctions-objectifs qui satisfassent ces conditions. Je termine le manuscrit en illustrant les difficultés rencontrées en pratique lorsque nous cherchons à évaluer les interprétations structurales à l'aide des données sismiques de surface. Je propose une fonction-objectif générale faite de deux composants principaux : (1) un opérateur de résidus qui calcule les résidus des données, et (2) un opérateur de projection qui projette les résidus de données depuis l'espace de données vers l'espace physique (le sous-sol). Cette fonction-objectif est donc localisée dans l'espace car elle génère des valeurs en fonction de l'espace. Cependant, je ne suis toujours pas en mesure de proposer une implémentation pratique de cette fonction-objectif qui satisfasse les conditions imposées pour une évaluation réussie des interprétations structurales ; cela reste un sujet de recherche
Subsurface structural models are routinely used for resource estimation, numerical simulations, and risk management; it is therefore important that subsurface models represent the geometry of geological objects accurately. The first step in building a subsurface model is usually to interpret structural features, such as faults and horizons, from a seismic image; the identified structural features are then used to build a subsurface model using interpolation methods. Subsurface models built this way therefore inherit interpretation uncertainties since a single seismic image often supports multiple structural interpretations. In this manuscript, I study the problem of reducing interpretation uncertainties using seismic data. In particular, I study the problem of using seismic data to determine which structural models are more likely than others in an ensemble of geologically plausible structural models. I refer to this problem as "appraising structural models using seismic data". I introduce and formalize the problem of appraising structural interpretations using seismic data. I propose to solve the problem by generating synthetic data for each structural interpretation and then to compute misfit values for each interpretation; this allows us to rank the different structural interpretations. The main challenge of appraising structural models using seismic data is to propose appropriate data misfit functions. I derive a set of conditions that have to be satisfied by the data misfit function for a successful appraisal of structural models. I argue that since it is not possible to satisfy these conditions using vertical seismic profile (VSP) data, it is not possible to appraise structural interpretations using VSP data in the most general case. The conditions imposed on the data misfit function can in principle be satisfied for surface seismic data. In practice, however, it remains a challenge to propose and compute data misfit functions that satisfy those conditions. I conclude the manuscript by highlighting practical issues of appraising structural interpretations using surface seismic data. I propose a general data misfit function that is made of two main components: (1) a residual operator that computes data residuals, and (2) a projection operator that projects the data residuals from the data-space into the image-domain. This misfit function is therefore localized in space, as it outputs data misfit values in the image-domain. However, I am still unable to propose a practical implementation of this misfit function that satisfies the conditions imposed for a successful appraisal of structural interpretations; this is a subject for further research

Les modèles géologiques sont couramment utilisés pour estimer les ressources souterraines, pour faire des simulations numériques, et pour évaluer les risques naturels ; il est donc important que les modèles géologiques représentent la géométrie des objets géologiques de façon précise. La première étape pour construire un modèle géologique consiste souvent à interpréter des surfaces structurales, telles que les failles et horizons, à partir d'une image sismique ; les objets géologiques identifiés sont ensuite utilisés pour construire le modèle géologique par des méthodes d'interpolation. Les modèles géologiques construits de cette façon héritent donc les incertitudes d'interprétation car une image sismique peut souvent supporter plusieurs interprétations structurales. Dans ce manuscrit, j'étudie le problème de réduire les incertitudes d'interprétation à l'aide des données sismiques. Particulièrement, j'étudie le problème de déterminer, à l'aide des données sismiques, quels modèles sont plus probables que d'autres dans un ensemble des modèles géologiques cohérents. Ce problème sera connu par la suite comme "le problème d'évaluation des modèles géologiques par données sismiques". J'introduis et formalise ce problème. Je propose de le résoudre par génération des données sismiques synthétiques pour chaque interprétation structurale dans un premier temps, ensuite d'utiliser ces données synthétiques pour calculer la fonction-objectif pour chaque interprétation ; cela permet de classer les différentes interprétations structurales. La difficulté majeure d'évaluer les modèles structuraux à l'aide des données sismiques consiste à proposer des fonctions-objectifs adéquates. Je propose un ensemble de conditions qui doivent être satisfaites par la fonction-objectif pour une évaluation réussie des modèles structuraux à l'aide des données sismiques. Ces conditions imposées à la fonction-objectif peuvent, en principe, être satisfaites en utilisant les données sismiques de surface (« surface seismic data »). Cependant, en pratique il reste tout de même difficile de proposer et de calculer des fonctions-objectifs qui satisfassent ces conditions. Je termine le manuscrit en illustrant les difficultés rencontrées en pratique lorsque nous cherchons à évaluer les interprétations structurales à l'aide des données sismiques de surface. Je propose une fonction-objectif générale faite de deux composants principaux : (1) un opérateur de résidus qui calcule les résidus des données, et (2) un opérateur de projection qui projette les résidus de données depuis l'espace de données vers l'espace physique (le sous-sol). Cette fonction-objectif est donc localisée dans l'espace car elle génère des valeurs en fonction de l'espace. Cependant, je ne suis toujours pas en mesure de proposer une implémentation pratique de cette fonction-objectif qui satisfasse les conditions imposées pour une évaluation réussie des interprétations structurales ; cela reste un sujet de recherche
Subsurface structural models are routinely used for resource estimation, numerical simulations, and risk management; it is therefore important that subsurface models represent the geometry of geological objects accurately. The first step in building a subsurface model is usually to interpret structural features, such as faults and horizons, from a seismic image; the identified structural features are then used to build a subsurface model using interpolation methods. Subsurface models built this way therefore inherit interpretation uncertainties since a single seismic image often supports multiple structural interpretations. In this manuscript, I study the problem of reducing interpretation uncertainties using seismic data. In particular, I study the problem of using seismic data to determine which structural models are more likely than others in an ensemble of geologically plausible structural models. I refer to this problem as "appraising structural models using seismic data". I introduce and formalize the problem of appraising structural interpretations using seismic data. I propose to solve the problem by generating synthetic data for each structural interpretation and then to compute misfit values for each interpretation; this allows us to rank the different structural interpretations. The main challenge of appraising structural models using seismic data is to propose appropriate data misfit functions. I derive a set of conditions that have to be satisfied by the data misfit function for a successful appraisal of structural models. I argue that since it is not possible to satisfy these conditions using vertical seismic profile (VSP) data, it is not possible to appraise structural interpretations using VSP data in the most general case. The conditions imposed on the data misfit function can in principle be satisfied for surface seismic data. In practice, however, it remains a challenge to propose and compute data misfit functions that satisfy those conditions. I conclude the manuscript by highlighting practical issues of appraising structural interpretations using surface seismic data. I propose a general data misfit function that is made of two main components: (1) a residual operator that computes data residuals, and (2) a projection operator that projects the data residuals from the data-space into the image-domain. This misfit function is therefore localized in space, as it outputs data misfit values in the image-domain. However, I am still unable to propose a practical implementation of this misfit function that satisfies the conditions imposed for a successful appraisal of structural interpretations; this is a subject for further research

Considerable interest has developed recently in 'stretch' and 'power' fabrics and their component yams. Stretch fabrics are finding applications in areas such as medical compression therapy, support for back, knee and ankle, and in prosthetics. These stretch fabrics can be made by either knitting or weaving; knitted structures are widely used as stretch fabrics due to their inherent elasticity, drapability and the relative ease of fabrication with stretchable yams. Therefore, the present research work deals with the development of comprehensive mechanical models to predict the mechanical properties of plain knitted elastomeric structures namely the tensile, and interface pressure profile behaviour. All the models are based on Rayleigh-Ritz energy approach, which allows handling nonlinear mechanical properties of constituent yams while producing computationally efficient algorithms. The models incorporate modes of deformation i.e. yam elongation, yam bending and yam compression. An effort has been made to make the models more general by considering generalised geometry with adequate degrees of freedom to represent the yam path under all deformed configurations. A geometric model based on cubic spline geometry has been developed and it has been shown that the energy model based on this geometry closely simulates plain knitted elastomeric structure's mechanical behaviour in contrast to Chamberlain geometry. And therefore, cubic spline geometry has been applied for elastomeric plain knitted derivative structure, which is a stable structure and very much more capable of achieving the required high pressure profiles than the plain knitted elastomeric structure, and maintaining them over a useful period of time. This study also describes experimental investigation into the physical, structural, and mechanical behaviour of both constituent yam, i.e. covered elastomeric yams and plain knitted elastomeric fabrics, in order to ascertain the contribution of core and covered yams in terms of structural mechanical properties.

学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2856号 ; 請求記号: 新制/工/1420 ; 整理番号: 25541
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第13385号
工博第2856号
新制||工||1420(附属図書館)
25541
UT51-2007-Q786
京都大学大学院工学研究科建築学専攻
(主査)教授 加藤 直樹, 教授 上谷 宏二, 准教授 大﨑 純
学位規則第4条第1項該当

La connaissance du métabolisme demeure incomplète mais sa compréhension reste un but majeur tant pour la recherche fondamentale qu’appliquée. Environ 40% des gènes des organismes procaryotes n’ont pas de fonction précise proposée. En conséquence, de nombreuses voies métaboliques restent incomplètes, rendant très difficile la prédiction du métabolisme d’un organisme. Les recherches et les avancées dans la compréhension de la cascade des « omiques » incluant la génomique, la transcriptomique, la protéomique et la métabolomique jouent aujourd’hui un rôle central dans la connaissance du métabolisme. En tant qu’intermédiaires des réactions biochimiques, les métabolites connectent les différentes voies métaboliques d’un organisme. La quantité et la nature de ces molécules étant la résultante de l’expression des gènes, la composition en métabolites de la cellule est donc liée de très près à son phénotype. La métabolomique, qui étudie l’ensemble de ces petites molécules présentes dans un échantillon biologique, constitue une source d’informations importante nécessaire à la compréhension du métabolisme. En ce sens, le travail présenté dans ce manuscrit décrit la mise en place d’une approche métabolomique au sein du Genoscope pour l’étude du métabolisme de la bactérie modèle Acinetobacter baylyi (ADP1) en utilisant la spectrométrie de masse à haute résolution (LTQ-Orbitrap) couplée à la chromatographie liquide (LC/MS).Nous avons suivi la réorientation du métabolisme d’ADP1 à la suite d’une perturbation environnementale, induite par un changement de source de carbone. Nous avons comparé les métabolomes d’ADP1 cultivée sur succinate (source de carbone de référence) et sur quinate (source de carbone alternative). Environ 450 métabolites potentiels ont été détectés et plus d’une centaine ont pu être identifiés. Plusieurs phénomènes ont pu être observés. Premièrement, l’utilisation du quinate comme source de carbone engendre une réponse spécifique attendue, liée à sa dégradation (intermédiaires cataboliques détectés et gènes associés surexprimés). Toutefois, alors que le métabolisme central est peu affecté par ce changement biotique, la concentration d’environ la moitié des métabolites détectés est significativement modifiée. Ce résultat inattendu est en accord avec les expériences de transcriptomique qui indiquent, qu’avec ce changement de source de carbone, 12% des gènes sont différentiellement exprimés. Nos résultats montrent que la perturbation du métabolisme dans ces conditions s’étend bien au-delà de la voie de dégradation du quinate ; elle engendre un bouleversement global du métabolisme (Stuani, Lechaplais et al. 2014).Cette étude a également permis de détecter de nouveaux métabolites, produits dans des cellules utilisant du quinate. L’élucidation structurale de l’un d’entre eux est décrite dans ce manuscrit. Il s’agit d’une tyrosine substituée en position benzylique par un groupement méthylamine (BMAT). Son identification aura nécessité des expériences de CID-MSn séquentielles avec détection à haute résolution et d’échanges H/D. Des études structurales effectuées sur deux autres molécules suggèrent des similarités structurales entre elles et avec le BMAT. Nous pourrions donc être en présence d’une famille de nouveaux métabolites secondaires, impliqués dans une même voie métabolique. C’est donc une approche métabolomique qui a permis à un simple changement de source de carbone de nous orienter vers la découverte de nouvelles voies métaboliques et d’appréhender une part cachée du métabolisme d’ADP1
While incomplete, the knowledge of metabolism remains a priority for both basic and applied research. With approximately 40 % of genes of prokaryotic genomes with no accurate function, a number of metabolic pathways remain incomplete, which impedes the accurate prediction of the metabolism of a cell.Recent progress and breakthroughs in the understanding of the Omics Cascade that includes genomics, transcriptomics, proteomics and metabolomics play an important role in the knowledge of metabolism. As intermediaries of biochemical reactions, metabolites connect the different metabolic pathways of the cell. The amount and nature of these molecules being the result of gene expression, the metabolite content of a cell is thus closely related to its phenotype. Metabolomics, which aims at studying the whole set of metabolites present in a biological sample, is an invaluable source of information for the understanding of metabolism.This is why the work presented in this thesis reports the setup of a metabolomic approach at Genoscope for the study of metabolism of the model bacterium Acinetobacter baylyi ADP1 (ADP1) through high-resolution mass spectrometry (LTQ-Orbitrap) coupled to liquid chromatography (LC/MS).We investigated the metabolism of ADP1 after an environmental perturbation induced by a change of carbon source. We compared the metabolomes of ADP1 grown on succinate (reference carbon source) and on quinate (alternative source). About 450 potential metabolites could be detected and more than a hundred were identified. Many observations were made. First, quinate as a carbon source triggered an expected specific metabolic response in relation with its dissimilation (quinate catabolites were detected and the corresponding genes were up-regulated). However, while central metabolism is not impacted by this biotic change, about half of the detected metabolites had their concentration changed. This unexpected result is consistent with transcriptomic experiments that revealed that with the change of carbon source, 12% of the total number of genes are differentially expressed. Our results show that in these conditions, metabolic alteration goes far beyond the quinate degradation pathway and causes a global overhaul of the metabolism of ADP1 (Stuani, Lechaplais et al. 2014).This study also led to the detection of novel metabolites that were exclusively produced in quinate-grown cells. The structural elucidation of one of them is reported in this manuscript. It is a tyrosine substituted in the benzylic position by an aminomethyl group (BMAT). Its identification required sequential CID-MSn experiments with high-resolution detection and isotopic H/D exchange experiments. Structural studies conducted on two other molecules suggest structural similarities with BMAT. We thus could be in the presence of a family of novel secondary metabolites, involved in the same metabolic pathway.In conclusion, a metabolomic approach allowed a mere change of carbon source to guide us toward the discovery of novel metabolic pathways and gain insight into the hidden part of ADP1 metabolism

Deployable structures serve a large number of space missions. They are vital since spacecraft are launched by placing them inside launch vehicle payload fairings of limited volume. Traditional spacecraft design often involves large components. These components could have power, communication, or optics applications and include booms, masts, antennas, and solar arrays. Different stowing methods are used in order to reduce the overall size of a spacecraft. Some examples of stowing methods include simple articulating, more complex origami inspired folding, telescoping, and rolling or wrapping. Wrapping of a flexible component could reduce the weight by eliminating joints and other components needed to enable some of the other mechanisms. It also is one of the most effective methods at reducing the compaction volume of the stowed deployable. In this study, a generic unfurlable structure is optimized for maximum natural frequency at its fully deployed configuration and minimal strain energy in its stowed configuration. The optimized stowed structure is then deployed in simulation. The structure consists of a rectangular panel that tightly wraps around a central cylindrical hub for release in space. It is desired to minimize elastic energy in the fully wrapped panel and hinge to ensure minimum reaction load into the spacecraft as it deploys in space, since that elastic energy stored at the stowed position transforms into kinetic energy when the panel is released and induces a moment in the connected spacecraft. It is also desired to maximize the fundamental frequency of the released panel as a surrogate for the panel having sufficient stiffness. Deployment dynamic analysis of the finite element model was run to ensure satisfactory optimization formulation and results.
Master of Science
Spacecraft, or artificial satellites, do not fly from earth to space on their own. They are launched into their orbits by placing them inside launch vehicles, also known as carrier rockets. Some parts or components of spacecraft are large and cannot fit in their designated space inside launch vehicles without being stowed into smaller volumes first. Examples of large components on spacecraft include solar arrays, which provide power to the spacecraft, and antennas, which are used on satellite for communication purposes. Many methods have been developed to stow such large components. Many of these methods involve folding about joints or hinges, whether it is done in a simple manner or by more complex designs. Moreover, components that are flexible enough could be rolled or wrapped before they are placed in launch vehicles. This method reduces the mass which the launch vehicle needs to carry, since added mass of joints is eliminated. Low mass is always desirable in space applications. Furthermore, wrapping is very effective at minimizing the volume of a component. These structures store energy inside them as they are wrapped due to the stiffness of their materials. This behavior is identical to that observed in a deformed spring. When the structures are released in space, that energy is released, and thus, they deploy and try to return to their original form. This is due to inertia, where the stored strain energy turns into kinetic energy as the structure deploys. The physical analysis of these structures, which enables their design, is complex and requires computational solutions and numerical modeling. The best design for a given problem can be found through numerical optimization. Numerical optimization uses mathematical approximations and computer programming to give the values of design parameters that would result in the best design based on specified criterion and goals. In this thesis, numerical optimization was conducted for a simple unfurlable structure. The structure consists of a thin rectangular panel that wraps tightly around a central cylinder. The cylinder and panel are connected with a hinge that is a rotational spring with some stiffness. The optimization was solved to obtain the best values for the stiffness of the hinge, the thickness of the panel, which is allowed to vary along its length, and the stiffness or elasticity of the panel's material. The goals or objective of the optimization was to ensure that the deployed panel meets stiffness requirement specified for similar space components. Those requirements are set to make certain that the spacecraft can be controlled from earth even with its large component deployed. Additionally, the second goal of the optimization was to guarantee that the unfurling panel does not have very high energy stored while it's wrapped, so that it would not cause large motion the connected spacecraft in the zero gravity environments of space. A computer simulation was run with the resulting hinge stiffness and panel elasticity and thickness values with the cylinder and four panels connected to a structure representing a spacecraft. The simulation results and deployment animation were assessed to confirm that desired results were achieved.

This thesis documents the results of a structural and compositional study of selected mixed metal oxides possessing novel structures based upon 'ribbons' of corner sharing metal-oxygen octahedra. The techniques employed to characterise the specimens of interest have included Powder X-ray Diffraction (PXRD). High Resolution Transmission Electron Microscopy (HRTEM) and Energy Dispersive X-ray Spectroscopy (EDS). Compositional analysis of specimens containing strontium, lanthanum and titanium has been achieved to a high degree of accuracy using EDS analysis in the electron microscope. A mathematical technique based upon the intensity ratios of the X-ray emission lines has been developed to overcome the problem of overlapping lanthanum L and titanium K peaks in the X-ray emission specimen. The viability of the new technique has been proven using well characterised test specimens containing all three elements. An in-depth study of two compounds in the SrO-La₂O₃-TiO₂ system, Sr₃La₂Ti₂O₁₀ and Sr₈La₄Ti₅O₂₄ has been performed. Evidence from high resolution imaging and electron diffraction has confirmed that threes phases possess composite layer structures based upon corner sharing ribbons of TiO₆ octahedra. Their status as the n=4 and n=5 members of a homologous series Sr_2n-2La₄Ti_nO_4n+4, where the parameter n represents the number of TiO₆ octahedra in the ribbons, has also been established using EDS. However, results also suggest that these compounds may be metastable. The effect of niobium substitution on the structure of the n=1 Aurivillius phase, Bi₂WO₆, has also been investigated. Results from HRTEM have shown up to 25% of the tungsten can be substituted by niobium without any observable effect on the Aurivillius structure. Upon 50% niobium substitution, it appears that a structural modification takes place, as high resolution imaging and electron diffraction reveal a superstructure on the (012) or (013) planes of a Bi₂WO₆ sub-cell, which can be attributed to the presence of steps in the Aurivillius matrix at regular intervals.

In general, the main purpose of a structural control system is to apply powerful control techniques that improve the behaviour of civil structures under various kinds of dynamic loading. The first part of this thesis presents novel applications of posicast and input shaping control schemes that have never previously been applied in the field of structural control. Numerical simulations of a benchmark three-story building with an MR damper are used to verify the efficiency of the proposed control theories. The superiority and effectiveness of the suggested schemes at reducing the structure’s responses were demonstrated using six evaluation criteria and by comparison to results achieved with well-established classical control schemes. Moreover, a comprehensive procedure for generating scaled real ground motion records appropriate for a seismic analysis and design of structures using the linear spectrum matching technique is presented based on a seismic hazard study.To efficiently control a structure, it is necessary to estimate its real-life dynamical behaviour. This is usually done using the Structural Identification approach, which is also addressed in this thesis. Structural Identification is commonly utilized to bridge the gap between the real structure and its modeled behaviour. It can also be used to evaluate the structure’s health, detect damage, and assess efficiency. Despite the extensive development of parametric time domain identification methods, their relative merits and the accuracy with which they predict the behaviour of vibrating structures are largely unknown because there have been few comparative studies on their performance under diverse test conditions, and they have not been verified against real-life data gathered over extended periods of time.Thus, the second part of this thesis focuses on applications of parametric and non-parametric models based on the Structural Identification approach in order to clarify their potential and applicability. In addition, a new strategy is proposed that combines this approach with techniques based on Singular Value Decomposition (SVD) and Complex Mode Indicator Function (CMIF) curves to detect structural damage.The methods developed in this work are used to predict the vertical frequencies of the top storey in a multi-storey building prefabricated from reinforced concrete in Stockholm, and to detect and locate damage in a benchmark steel frame. In addition, the non-parametric structural identification approach is used to investigate variation in the modal characteristics (frequency, damping, and mode shapes) of a steel railway bridge.

Godkänd; 2015; 20150303 (taredr); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Tarek Edreees Saaed Alqado Ämne: Konstruktionsteknik/Structural Engineering Avhandling: Structural Control and Identification of Civil Engineering Structures Opponent: Professor Francesc Pozo, Department of Applied Mathematics III, Escola Universitària d’Enginyeria Tècnica Industrial de Barcelona (EUETIB), Universitat Politècnica de Catalunya Comte d’Urgell, Barcelona, Spanien Ordförande: Professor Jan-Erik Jonasson vid Avd för byggkonstruktion och produktion, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Torsdag den 26 mars 2015, kl 10.00 Plats: C305, Luleå tekniska universitet

Composite materials are in use in several applications, for example, aircraft structural components, because of their light weight and high strength. However the delamination which is one of the serious defects often develops and propagates due to vibration during the service of the structure. The presence of this defect warrants the design life of the structure and the safety. Hence the presence of such defect has to be detected in time to plan the remedial action well in advance. There are a number of methods in the literature for damage detection. They are either 'baseline free/reference free method' or using the data from the healthy structure for damage detection. However very limited vibration-based methods are available in the literature for delamination detection in composite structures. Many of these methods are just simulated studies without experimental validation. Grossly 2 kinds of the approaches have been suggested in the literature, one related to low frequency methods and other high frequency methods. In low frequency approaches, the change in the modal parameters, curvatures, etc. is compared with the healthy structure as the reference, however in the high frequency approaches, excitation of structures at higher modes of the order of few kHz or more needed with distributed sensors to map the deflection for identification of delamination. Use of high frequency methods imposes the limitations on the use of the conventional electromagnetic shaker and vibration sensors, whereas the low frequency methods may not be feasible for practical purpose because it often requires data from the healthy state which may not be available for old structures. Hence the objective of this research is to develop a novel reference-free method which can just use the vibration responses at a few lower modes using a conventional shaker and vibration sensors (accelerometers/laser vibrometers). It is believed that the delaminated layers will interact nonlinearly when excited externally. Hence this mechanism has been utilised in the numerical simulations and the experiments on the healthy and delaminated composite plates. Two methods have been developed here - first method can quickly identify the presence of the delamination when excited at just few lower modes and other method identify the location once the presence of the delamination is confirmed. In the first approach an averaged normalised RMS has been suggested and experimentally validated for this purpose. Latter the vibration data have then been analysed further to identify the location of delamination and its size. Initially, the measured acceleration responses from the composite plates have been differentiated twice to amplify the nonlinear interaction clearly in case of delaminated plate and then kurtosis was calculated at each measured location to identify the delamination location. The method has further been simplified by just using the harmonics in the measured responses to identify the location. The thesis presents the process of the development of the novel methods, details of analysis, observations and results.

This study presents the application of control methods in seismic mitigation of structural responses. The study consists of two parts. In the first section, fractional order filters are utilized to enhance the performance of the conventional LQR method for optimal robust control of a simple civil structure. The introduced filters modify the state variables fed back to the constant gain controller. Four combinations of fractional order filter and LQR are considered and optimized based on a new performance criterion defined in the paper. Introducing fractional order filters is shown to improve the results considerably for both the artificially generated ground motions and previously recorded earthquake data. In the second part, frequency dependent filters are introduced to improve the effectiveness of active control systems designed to mitigate the seismic response of large scale civil structures. These filters are introduced as band pass pre-filters to the optimally designed H2/LQG controller to reduce the maximum singular value response of input-output transfer matrices over a defined frequency range. Furthermore, a structured uncertainty model is proposed to evaluate robustness of stability and performance considering nonlinear force-deformation behavior of structures. The proposed perturbation model characterizes variations in the stiffness matrix more accurately, thereby reducing overconservatism in the estimated destabilizing perturbations. The aforementioned techniques are applied to the nonlinear SAC three story steel building. Numerical results indicate that introducing filters can enhance the performance of the system in almost all response measures, while preserving robustness of stability and performance.

Programa de Pós Graduação em Engenharia Civil. Departamento de Engenharia Civil, Escola de Minas, Universidade Federal de Ouro Preto.
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This paper provides a qualitative investigation about the structural performance of the membranes, surface structures (with double curvature in opposite directions) with minimum thickness and weight, which absorb forces in form of tensile stresses in its own plane, considering two aspects: structural and design procedure. Initially, it involved the analyses of lightweight structure buildings and the observation of constructive work process in membrane roofs. These investigations allowed identifying strategies that contribute to achieve optimum system performance and the challenges encountered along the stages of designing and building. They also guided the qualitative analysis of the performance of a structural membrane roofing project, i.e., a particular situation, as example. This qualitative analysis was developed in two stages, guided by experimental and numerical data. The first stage involved the optimization procedure of the structural system under load action. This analysis showed that the flexible system performance is a result of the three-dimensional stability of the structural system (arrangement and geometry of all components), membrane surface stiffness (membrane geometry), as well as the cooperation of all components in pre-tension state. The second stage comprised the experimental investigation of the membrane material behaviour within the structure context in order to analyze the flattened membrane geometry. Such evaluation enabled to verify the difference between the theoretical model (shape of equilibrium) and the actual shape (consisting of flat panels), enabling the proper adjustment of the surface geometry so that the final shape can reveal not only the path of the forces, but also the best use of the material. The investigations, analyses and working procedure here adopted broadened the understanding of this system pointing possibilities to increase its performance and to minimize failures during the preliminary stage of design.

Methods for modeling structural failure with applications for fluid structure interaction (FSI) are developed in this work. Fracture as structural failure is modeled in this work by both the extended finite element method (XFEM) and element deletion. Both of these methods are used in simulations coupled with fluids modeled by computational fluid dynamics (CFD). The methods presented here allow the fluid to pass through the fractured areas of the structure without any prior knowledge of where fracture will occur. Fracture modeled by XFEM is compared to an experimental result as well as a test problem for two phase coupling. The element deletion results are compared with an XFEM test problem, showing the differences and similarities between the two methods.

A new method for modeling fracture is also proposed in this work. The new method combines XFEM and element deletion to provide a robust implementation of fracture modeling. This method integrates well into legacy codes that currently have element deletion functionality. The implementation allows for application by a wide variety of users that are familiar with element deletion in current analysis tools. The combined method can also be used in conjunction with the work done on fracture coupled with fluids, discussed in this work.

Structural failure via buckling is also examined in an FSI framework. A new algorithm is produced to allow for structural subcycling during the collapse of a pipe subjected to a hydrostatic load. The responses of both the structure and the fluid are compared to a non-subcycling case to determine the accuracy of the new algorithm.

Overall this work looks at multiple forms of structural failure induced by fluids modeled by CFD. The work extends what is currently possible in FSI simulations.

What stance should we take toward our best scientific theories? Traditionally, there have been two answers: realism and antirealism. Structural realism is an attempt to find middle-ground between these two views. Rather than accept everything our best theories seem to say about the world, the structural realist endorses only what those theories tell us about the structure of the world. I argue that switching the focus to structure allows the realist to better deal with problems of theory-change, and to better make sense of contemporary physics. I go on to offer a specific version of structural realism based on an understanding of structures as networks of relations between objects that are nothing more than places in structures. My view allows that there are objects and relations, but reverses the usual order of dependence: objects depend on relations rather than the other way around.

The Structural Insulated Panel System (SIP system) has recently attracted continuingly growing interest since it is strong, energy efficient, easy to use in construction and hence has a potential to become a new alternative building material. It is anticipated that Structural Insulated Panels (SIPs) are required to withstand loads in various directions either individually or in combinations, e.g., the axial, racking and transverse loadings. Very few publications report the performance of SIPs when subjected to loads in multiple directions. Moreover, when applying SIPs as a load bearing material, there is another major concern related to their long-term performance, mainly caused by creep. This research presents studies on structural behaviours of the SIPs under both short-term and long-term loadings under single and multi-axial loadings together with two typical joint designs i.e. mini-SIP and dimensional timber spline joints with and without openings by experimental, analytical and numerical investigations. It has been demonstrated that the developed numerical models can well predict the initiation of failure load and the failure mode of SIPs. Interactive failure load curves between axial and transverse loadings have been developed by carrying out a parametric analysis for SIPs with/without openings by using two types of joint construction.

The great social and economic impact of earthquakes has made necessary the development of novel structural health monitoring (SHM) solutions for increasing the level of structural safety and assessment. SHM is the process of comparing the current state of a structure’s condition relative to a healthy baseline state to detect the existence, location, and degree of likely damage during or after a damaging input, such as an earthquake. Many SHM algorithms have been proposed in the literature. However, a large majority of these algorithms cannot be implemented in real time. Therefore, their results would not be available during or immediately after a major event for urgent post-event response and decision making. Further, these off-line techniques are not capable of providing the input information required for structural control systems for damage mitigation. The small number of real-time SHM (RT-SHM) methods proposed in the past, resolve these issues. However, these approaches have significant computational complexity and typically do not manage nonlinear cases directly associated with relevant damage metrics. Finally, many available SHM methods require full structural response measurement, including velocities and displacements, which are typically difficult to measure. All these issues make implementation of many existing SHM algorithms very difficult if not impossible. This thesis proposes simpler, more suitable algorithms utilising a nonlinear Bouc-Wen hysteretic baseline model for RT-SHM of a large class of nonlinear hysteretic structures. The RT-SHM algorithms are devised so that they can accommodate different levels of the availability of design data or measured structural responses, and therefore, are applicable to both existing and new structures. The second focus of the thesis is on developing a high-speed, high-resolution, seismic structural displacement measurement sensor to enable these methods and many other SHM approaches by using line-scan cameras as a low-cost and powerful means of measuring structural displacements at high sampling rates and high resolution. Overall, the results presented are thus significant steps towards developing smart, damage-free structures and providing more reliable information for post-event decision making.

Med utviklingen som har funnet sted innenfor den norske oljebransjen de siste årene har både teknologien og utfordringene blitt mer komplekse. Subsea-operasjoner har blitt mer vanlig og gir utslag i at det på havbunnen i mange felt er sammenkoblede systemer av konstruksjoner. I relasjon til seismisk aktivitet reises da spørsmålet om disse systemene med brønner, rør og andre konstruksjoner kan tåle å bli utsatt for et jordskjelv av en viss størrelse. For å ta et steg i retningen av å besvare dette spørsmålet, dreier denne hovedoppgaven seg om studien av en beskyttelseskonstruksjon som utsettes for grunnakselerasjoner funnet ved probabilistisk evaluering av valgte jordskjelvdata tilgjengelig for den norske kontinentalsokkelen.Den valgte konstruksjonen er lokalisert i Åsgårdfeltet på Haltenbanken vest for midt-Norge. Det er en ganske liten og slank konstruksjon hvis funksjon er å beskytte oljeinstallasjoner fra eventuelle skader forårsaket fra trål og fallende objekter i forbindelse med fiskeriindustrien. I modelleringen av konstruksjonen vurderes den som et produkt av tre forskjellige systemer. Det første systemet er konstruksjonen alene, det andre systemet er jordsystemet og det tredje er fluidsystemet. Dermed ble tre modeller laget der de forskjellige systemegenskapene (fjærer/dempere, hydrodynamiske krefter) ble introdusert stegvis.For å undersøke konstruksjonens respons i forhold til påsatte grunnakselerasjoner, måtte representative tidsrekker for jordskjelv brukes. Disse tidsrekkene ble funnet ved hjelp av probabilistisk vurdering av en syntetisk jorskjelvkatalog. Denne jordskjelvkatalogen ble generert ved å bruke Gutenberg-Richter relasjonen, og de tilhørende parametrene og områdene de gjelder for ble funnet i en rapport angående seismisk inndeling av Norge \cite{zonation}. Jordskjelvparameteren som ble valgt var maksimum grunnakselerasjon (PGA) i både horisontal og vertikal retning estimert ved en relasjon funnet av Ambraseys, med flere \cite{ambhor}\cite{ambver}. Videre ble ordningsstatistikk brukt på de genererte PGA-verdiene ved å bruke Gumbels fordeling for maksima. De resulterende PGA-verdiene i horisontal og vertikal retning ble så brukt for å finne en passende tidsrekke for akselerasjon i en database over jordskjelv for Europa og Midtøsten \cite{esmd}. Deretter ble disse akselerasjonene påsatt de tre modellene og responsen ble evaluert ved ikkelineær direkte implisitt integrasjon. Videre ble en modal analysis av responene utført på den fullt neddykkede modellen for sammenlikningens skyld. Enda en tidsserie ble også påsatt den fullt neddykkede modellen som ble generert basert på det området med høyest seismisk aktivitet, funnet i rapporten nevnt ovenfor for å vurdere det verst tenkelige tilfellet.Resultatene av disse analysene viste at med introduksjon av jord-konstruksjon-interaksjon modellert ved fjærer og dempere, så økte forskyvningene sammenliknet med den fast innspente modellen (konstruksjonen alene). Videre så økte forskyvningene ytterligere ved å introdusere hydrodynamiske krefter. På grunn av små forskyvninger dominerte treghetskreftene responsen for den neddykkede modellen. Med tanke på konstruksjonens oppførsel så ble konstruksjonen nesten ikke affisert av de påsatte grunnakselerasjonene - som er et godt tegn. Imidlertid er det vanskelig å konkludere hvordan andre typer konstruksjoner som rør og platformer ville ha respondert hvis de ble utsatt for de samme grunnakselerasjonene ettersom disse har mye større dimensjoner og annerledes geometri.

The structural analysis serves as a bridge to link the structure of materials to their properties. Revealing the structure details allows a better understanding on the growth mechanisms and properties of materials, and a further designed synthesis of functional materials. The widely used methods based on X-ray diffraction have certain limitations for the structural analysis when crystals are small, poorly crystallized or contain many defects. As electrons interact strongly with matter and can be focused by electromagnetic lenses to form an image, electron crystallography (EC) approaches become prime candidates for the structural analysis of a wide range of materials that cannot be done using X-rays, particularly nanomaterials with poor crystallinity. Three-dimensional electron diffraction tomography (3D EDT) is a recently developed method to automatically collect 3D electron diffraction data. By combining mechanical specimen tilt and electronic e-beam tilt, a large volume of reciprocal space can be swept at a fine step size to ensure the completeness and accuracy of the diffraction data with respect to both position and intensity. Effects of the dynamical scattering are enormously reduced as most of the patterns are collected at conditions off the zone axes. In this thesis, 3D EDT has been used for unit cell determination (COF-505), phase identifications and structure solutions (ZnO, Ba-Ta3N5, Zn-Sc, and V4O9), and the study of layer stacking faults (ETS-10 and SAPO-34 nanosheets). High-resolution transmission electron microscope (HRTEM) imaging shows its particular advantages over diffraction by allowing observations of crystal structure projections and the 3D potential map reconstruction. HRTEM imaging has been used to visualize fine structures of different materials (hierarchical zeolites, ETS-10, and SAPO-34). Reconstructed 3D potential maps have been used to locate the positions of metal ions in a woven framework (COF-505) and elucidate the pore shape and connectivity in a silica mesoporous crystal. The last part of this thesis explores the combination with X-ray crystallography to obtain more structure details.

This research study addresses two issues for the identification of structural characteristics of civil infrastructure systems. The first one is related to the problem of dynamic system identification, by means of experimental and operational modal analysis, applied to a large variety of bridge structures. Based on time and frequency domain techniques and mainly with output-only acceleration, velocity or strain data, modal parameters have been estimated for suspension bridges, masonry arch bridges, concrete arch and continuous bridges, reticular and box girder steel bridges. After giving an in-depth overview of standard and advanced stochastic methods, differences of the existing approaches in their performances are highlighted during system identification on the different kinds of civil infrastructures. The evaluation of their performance is accompanied by easy and hard determinable cases, which gave good results only after performing advanced clustering analysis. Eventually, real-time vibration-based structural health monitoring algorithms are presented during their performance in structural damage detection by statistical models. The second issue is the noise-free estimation of high order displacements taking place on suspension bridges. Once provided a comprehensive treatment of displacement and acceleration data fusion for dynamic systems by defining the Kalman filter algorithm, the combination of these two kinds of measurements is achieved, improving the deformations observed. Thus, an exhaustive analysis of smoothed displacement data on a suspension bridge is presented. The successful tests were subsequently used to define the non-collocated sensor monitoring problem with the application on simplified models
Questo lavoro di ricerca mira a due obiettivi per l'identificazione delle caratteristiche strutturali dei sistemi infrastrutturali civili. Il primo è legato al problema della identificazione del sistema dinamico, mediante analisi modale sperimentale e operativa, applicata ad una grande varietà di strutture da ponte. Basandosi su tecniche nel dominio del tempo e delle frequenze e, soprattutto, su dati di output di accelerazione, velocità o strain, i parametri modali sono stati stimati per ponti sospesi, ponti ad arco in muratura, ponti a travi in calcestruzzo e ad arco, ponti reticolari e ponti in acciaio a cassone. Dopo aver dato una panoramica approfondita dei metodi stocastici standard ed avanzati, sono state evidenziate le differenze degli approcci esistenti nelle loro performance per l'identificazione del sistema sui diversi tipi di infrastrutture civili. La valutazione della loro performance viene accompagnata da casi facilmente e difficilmente determinabili, che hanno dato buoni risultati solo dopo l'esecuzione di analisi avanzate di Clustering. Inoltre, sono stati sviluppati algoritmi di identificazione dinamica automatica in tempo reale basandosi sulle vibrazioni strutturali dei ponti monitorati, a sua volta utilizzati nel rilevamento dei danni strutturali tramite modelli statistici. Il secondo problema studiato riguarda la stima di spostamenti di ordine superiore che si svolgono sui ponti sospesi, eliminando il rumore di misura e di processo. Una volta fornito un trattamento completo della fusione dei dati di spostamento e accelerazione per i sistemi dinamici tramite il filtro di Kalman, la combinazione di questi due tipi di misurazioni ha mostrato un miglioramento nelle deformazioni osservate. Pertanto, è stata presentata un'analisi esauriente di un ponte sospeso e dei sui dati dinamici e di spostamento filtrati. I test positivi sono stati successivamente utilizzati per definire il problema dei sensori non collocati alla stessa locazione ed applicazione su modelli semplificati

This thesis covers the process from expression of a heterologous gene in Escherichia coli to structure determination of a protein by nuclear magnetic resonance (NMR) spectroscopy.

The first part concerns structural genomics-related parallel screening studies on the effect of fusion tags (in particular the His tag) on protein solubility and the use of fusion tags in fast, parallel purification protocols intended for initial biophysical characterization of human proteins produced in E. coli. It was found that for most proteins the His tag has a negative influence on protein solubility. This influence appears to be more pronounced for our C-terminal His tag than for the N-terminal His tags used in this study. Moreover, high ratios of soluble per total protein do not always guarantee a high yield of soluble protein after purification, as different vector - target protein combinations result in large differences in host cell growth rates. Protein purification protocols for different fusion tags were developed that make it possible to express, purify and study structural properties of low concentration samples of 15N-labeled proteins in one or two days.

The second part of this thesis describes the assignment and solution structure determination of ribosomal protein L18 of Thermus thermophilus. The protein is a mixed α/β structure with two α-helices on one side of a four-stranded β-sheet. Comparison to RNA-bound L18 showed that the protein to a large extent adopts identical structures in free and bound states, with exception of the loop regions and the flexible N-terminus.

Keywords: protein production, protein solubility, fusion tags, nuclear magnetic resonance, structure determination, ribosomal protein

Active control of sound radiation from vibrating structures has been an area of much research in the past decade. In Active Structural Acoustic Control (ASAC), the minimization of sound radiation is achieved by modifying the response of the structure through structural inputs rather than by exciting the acoustic medium (Active Noise Control, ANC). The ASAC technique often produces global far-field sound attenuation with relatively few actuators as compared to ANC. The structural control inputs of ASAC systems are usually constructed adaptively in the time domain based on a number of error signals to be minimized. One of the primary concerns in active control of sound is then to provide the controller with appropriate ``error'' information. Early investigations have implemented far-field microphones, thereby providing the controller with actual radiated pressure information. Most structure-borne sound control approaches now tend to eliminate the use of microphones by developing sensors that are integrated in the structure. This study presents a new sensing technique implementing such an approach. A structural acoustic sensor is developed for estimating radiation information from vibrating structures. This technique referred to as Discrete Structural Acoustic Sensing (DSAS) provides time domain estimates of the radiated sound pressure at prescribed locations in the far field over a broad frequency range. The structural acoustic sensor consists of a set of accelerometers mounted on the radiating structure and arrays of digital filters that process the measured acceleration signals in real time. The impulse response of each filter is constructed from the appropriate radiation Green's function for the source area associated with each accelerometer. Validation of the sensing technique is performed on two different systems: a baffled rectangular plate and a baffled finite cylinder. For both systems, the sensor is first analyzed in terms of prediction accuracy by comparing estimated and actual sound pressure radiated in the far field. The analysis is carried out on a numerical model of the plate and cylinder as well as on the real structures through experimental testing. The sensor is then implemented in a broadband radiation control system. The plate and cylinder are excited by broadband disturbance inputs over a frequency range encompassing several of the first flexural resonances of the structure. Single-sided piezo-electric actuators provide the structural control inputs while the sensor estimates are used as error signals. The controller is based on the filtered-x version of the adaptive LMS algorithm. Results from both analytical and experimental investigations are again presented for the two systems. Additional control results based on error microphones allow a comparison of the two sensing approaches in terms of control performance. The major outcome of this study is the ability of the structural acoustic sensor to effectively replace error microphones in broadband radiation control systems. In particular, both analytical and experimental results show the level of sound attenuation achieved when implementing Discrete Structural Acoustic Sensing rivaled that achieved with far-field error microphones. Finally, the approach presents a significant alternative over other existing structural sensing techniques as it requires very little system modeling.
Ph. D.

This thesis investigates the possibility of controlling the response of a general multi-degree of freedom structure to a relatively distant blast load using passive and semi-active devices. A relatively distant blast is one that applies significant momentum to the structure, but does not destroy the face of the structure. Three multi-storey structures, and one single-storey structure, are modelled using non-linear finite elements with structural columns discretised into multiple elements to accurately capture the effects of higher order modes that are typically excited in such blast load responses. The single-storey model structure is subjected to blast loads of varying duration, magnitude and shape, and the critical aspects of the response are investigated over a range of structural periods in the form of blast load response spectra. The optimal device arrangements are found to be those that reduce the first peak of the structural displacement and thus also reduce the subsequent free vibration of the structure. For a given blast load, various passive and semi-active devices, as well as device architectures, are investigated. The optimal device architecture was found to be one that spanned approximately two-thirds the height of the structure. Depending on what damage parameters are considered critical for a given structure, different devices and arrangements are appropriate. The main factors in choosing a semi-active device and its control architecture, or arrangement, are the tradeoffs between permanent deflection, free vibration, base shear and device capacity limitations. Overall, the results present a first analysis on the effectiveness of semi-active devices and the unique force-displacement properties they offer for mitigating non-catastrophic blast loads.

Thesis (Ph.D)--Computing, Georgia Institute of Technology, 2010.
Committee Chair: Yannis Smaragdakis; Committee Member: Oege de Moor; Committee Member: Richard LeBlanc; Committee Member: Santosh Pande; Committee Member: Spencer Rugaber. Part of the SMARTech Electronic Thesis and Dissertation Collection.