Estruturas alteadas são fortemente afetadas pelas ações naturais, que são por sinal, as ações de maior complexidade na engenharia estrutural em função do grande número de variáveis envolvidas. O vento é uma destas ações e também uma das mais importantes em condições gerais. Em projeto, a ação do vento é normalmente considerada através das indicações normativas de cada país, que são, em função de sua complexidade, descritas na forma de métodos estático equivalentes, suficientes para maioria dos casos. Este critério não difere ao se tratar de linhas de transmissão, no entanto, grande parte das normas do mundo basearam-se no comportamento das torres autoportantes, mas que vêm sendo igualmente utilizadas em projetos de torres estaiadas. Por este motivo, se propõe a análise estatística de esforços de uma torre estaiada, modelada em conjunto com os demais componentes de uma linha de transmissão, de modo a compará-los aos resultados obtidos pelo método estático equivalente da IEC 60826 (IEC 2003). A hipótese de carregamento estudada é a ação transversal do vento na linha. Na simulação numérica, diversos campos aleatórios de velocidades são gerados, sendo as ações também calculadas pela formulação da norma IEC 60826. Os campos foram gerados por dois diferentes métodos, o método de Deodatis (1996) e método de Riera e Ambrosini (1992), ambos baseados no método de superposição de ondas. O espectro de velocidades utilizado neste trabalho é o espectro de Davenport. Apesar de saber da importância de outras fontes de não linearidades, foram consideradas neste trabalho: a não linearidade geométrica dos componentes, computada automaticamente com o uso do método de integração explícito por diferenças finitas centrais, e a não linearidade física dos cabos suspensos. Diferentes parâmetros de amortecimento foram testados para os componentes estruturais. Nos resultados é possível observar que a IEC 60826 mostrou-se suficiente na estimativa de esforços da maioria dos elementos analisados, no entanto, nas barras pertencentes ao mastro da torre verificaram-se valores normativos inferiores aos calculados pelo método numérico. Nestas barras, a diferença chegou a aproximadamente 22% pelo método de Deodatis (1996) e a 12% pelo método de Riera e Ambrosini (1992), ambos na configuração de menor amortecimento testada e para o intervalo de confiança de 98%. / High structures are strongly affected by natural loads, which are the most complexity loads in the structural engineering due the large number of variables involved. The wind is one of these actions and one of the most important in general conditions. In design, the action of wind is normally accounted through the country‟s standards indications which, due to its complexity, are usually descripted by equivalent static methods, enough in the most cases. This criterion does not differ for transmission lines, however, the most of standards in the world were based on the self-support towers behavior, but they are also being used for guyed towers design. Therefore, in this study is proposed a statistic analysis of internal forces in the guyed tower elements, modeled together with the other transmission lines components, in order to compare them with the results obtained by equivalent static method of IEC 60826 (IEC 2003). The load hypothesis is the across wind action. In the numerical simulation, several random velocity fields were generated, the actions being calculated by the formulation of IEC 60826 standard. The fields were generated by two different methods, the method of Deodatis (1996) and the method of Riera and Ambrosini (1992), both of them are based in the wave superimposition method. The power wind spectrum (PSD) used in this work is the Davenport‟s spectrum. Although knowing the importance of other nonlinearities, were considered in this work: the geometric non-linearity of all elements, which are automatically computed by explicitly integration method by central finite differences used, and the physic non-linearity of suspended cables. Different damping rates were considered for the structural components. In the results, it is possible to observe that the IEC 60826 was enough in the estimation of internal forces on the majority of elements analyzed, however, on the tower mast bars were verified normative values smaller than those obtained by numerical method. In these bars, the difference among analyses reached 22% by Deodatis (1996) method and 12% by Riera e Ambrosini (1992) method, both of them considering the lower tested damping configuration and the 98% confidence interval.

[pt] Torres estaiadas são, em geral, estruturas bastante leves e esbeltas e que apresentam comportamento eminentemente não - linear. Assim, a análise de sua estabilidade sob cargas estáticas e dinâmicas é essencial para se ter um projeto econômico e seguro. Neste trabalho estuda-se a estabilidade estática e dinâmica de um modelo plano de torre estaiada. Especial atenção é dada à modelagem dos estais, que são modelados como elementos de mola (linear ou não -linear) ou como cabos inextensíveis. Faz-se, com base no princípio da energia potencial mínima, um estudo da carga crítica e do caminho pós-crítico. Um estudo paramétrico minucioso permite analisar a influência dos diversos parâmetros físicos e geométricos na estabilidade da torre e chegar às melhores configurações para os estais. Na análise dinâmica atenção especial é dada ao estudo paramétrico da freqüência natural. Com base nos resultados da análise estática, analisa-se também o comportamento global da torre em vibração livre e forçada. Em virtude das não linearidades, verifica-se que a torre pode apresentar diversos comportamentos típicos de sistemas não -lineares tais como saltos, bifurcações de período e caos. / [en] Guyed towers are in general very light and slender structures and their behavior under static and dynamic loads is eminently nonlinear. Thus the analysis of its stability under static and dynamic loads is an essential step in obtaining an economic and safe project. In this work the static and dynamic stability analysis of a plain model of a guyed tower is studied. Special attention is given to the modeling of the stays; here they are modeled as spring elements (linear or nonlinear) or as inextensible cables. A study of the critical load and the postcritical nonlinear equilibrium paths is conducted based on the principle of the minimum potential energy A detailed parametric analysis is performed to identify the influence of the physical and geometric parameters of the system on the stability of the tower. This allows one to choose the best configurations for the stays. In the dynamic analysis special attention is given to the parametric study of the system natural frequencies. Based on the results of the static analysis, the global behavior of the tower under free and forced vibration is also analyzed. Due to the inherent nonlinearities, the tower may present dynamic responses typical of nonlinear systems such as jumps, period bifurcations and chaos.

Measurement collection is a primary step towards analyzing and optimizing performance of a telecommunication service. With an Mobile Broadband (MBB) network, the measurement process has not only to track the network's Quality of Service (QoS) features but also to asses a user's perspective about its service performance. The later requirement leads to "user-side measurements" which assist in discovery of performance issues that makes a user of a service unsatisfied and finally switch to another network. User-side measurements also serve as first-hand survey of the problem domain. In this thesis, we exhibit the potential in the measurements collected at network edge by considering two well-known approaches namely crowdsourced and distributed testbed-based measurements. Primary focus is on exploiting crowdsourced measurements while dealing with the challenges associated with it. These challenges consist of differences in sampling densities at different parts of the region, skewed and non-uniform measurement layouts, inaccuracy in sampling locations, differences in RSS readings due to device-diversity and other non-ideal measurement sampling characteristics. In presence of heterogeneous characteristics of the user-side measurements we propose how to accurately detect mobile coverage holes, to devise sample selection process so to generate a reliable radio map with reduced sample cost, and to identify cellular infrastructure at places where the information is not public. Finally, the thesis unveils potential of a distributed measurement test-bed in retrieving performance features from domains including user's context, service content and network features, and understanding impact from these features upon the MBB service at the application layer. By taking web-browsing as a case study, it further presents an objective web-browsing Quality of Experience (QoE) model.

Dissertation (PhD)--University of Stellenbosch, 1995. / Bibliography. Also available via the Internet.

A large portion of the existing building stock in North America is comprised of post-World War II high-rise apartment buildings, particularly in the Greater Golden Horseshoe in Ontario. They are home to a large portion of the Canadian population. These buildings are nearly 50 years old and reaching the end of their useful lifespan. Significant deterioration has lead to life safety concerns, poor standards of living, and aesthetic degradation. They also consume a significant amount of energy resulting in contributing to Canada’s high per capita greenhouse gas emissions. This thesis investigates the impact of various retrofit strategies on the energy consumption, durability, and occupant comfort of the towers. The building enclosure is the primary focus. The impacts were analyzed using three approaches. Whole building energy consumption was simulated by adapting a spreadsheet based Building Energy and Loads Analysis (BELA) model, originally intended for office buildings. Heat flow and temperatures across the enclosures were modeled using a two-dimensional finite element model (Therm 5.2). A single, theoretical building dubbed the, “Archetype”, was developed to define the characteristics of a “typical” tower using details extracted from four sets of drawings for towers built in Toronto during the late 1960s. Various quantities and configurations of thermal insulation were added to the Archetype and the resulting effective thermal resistances were modeled. Adding insulation to the interior significantly reduces the effectiveness of any added thermal resistance. Insulating on the exterior allows the insulation around the balconies to reach 80% of its rated value, even without insulating the balconies. Energy efficiency measures (EEMs) including retrofitting the walls, windows, appliances, or HVAC equipment were simulated and it was found that each on its own did not have a major impact on annual energy consumption. Packages of EEMs were created and simulated. It was found that a basic and high-performance whole building retrofit packages would save approximately 40% and 55% of the annual energy consumption, respectively, based on the Archetype. An analysis and discussion of the enclosure retrofit impacts on freeze-thaw potential, interior surface and interstitial condensation, occupants’ thermal comfort, and passive thermal comfort was completed. An interior versus exterior enclosure retrofit comparison summary illustrated that an exterior enclosure retrofit has significant benefits relative to an interior retrofit including ease of construction, greater durability, and improved comfort. The difference in annual energy reduction between an interior and exterior enclosure retrofit was small.

Guyed masts are special type of structures that are widely used in the telecommunication industry. In the past, there was no guideline for seismic design of these types of structures in the corresponding design codes. On the other hand, in the latest &ldquo / G&rdquo / revision of the ANSI/TIA-EIA code there is a comprehensive design criterion for the seismic design of the guyed masts. However, during the design process of these structures the most common approach is to ignore the effect of seismic loading and use only the internal forces developed from the wind load and ice load analysis. In this study firstly the efficiency and accuracy of the commercial SAP2000 and PLS-TOWER software were investigated, then finite element models of three guyed masts that had been designed in Turkey with the heights 30m, 60m and 100m in the SAP2000 and PLS-TOWER software were analyzed under the effect of earthquake, wind and ice loadings. The most common design code recognized all over the world used for the design of the guyed masts is ANSI/TIA-EIA 222-G &ldquo / Structural Standards for Steel Antenna Towers and Supporting Structures&rdquo / . Thus, the corresponding sections of this code were followed during the study. The main objective of this research is to check the correctness of commercial SAP2000 and PLS-TOWER software and to investigate the effect of seismic actions on the guyed masts and also to gain a better understanding of the behavior of guyed masts under the effects of the wind, ice and earthquake loadings.

Emergency wood shoring towers are utilized by Urban Search & Rescue (US&R) specialists to temporarily stabilize a damaged structure. Standardized designs for wood shoring towers have been developed and are published in manuals for use in US&R operations. These designs have been validated largely through past testing under simplified vertical loading. Research was conducted to provide additional insight into the performance of two common types of shores, the laced post (LP) shore and the plywood laced post (PLP) shore, under non-ideal (other than vertical) loading scenarios. Shores were tested under vertical load only, under lateral load only, and under combined vertical and lateral load. For lateral loading, some shores were tested under monotonic lateral load (lateral load applied in one direction only) and some were tested under cyclic lateral loading. Each specimen was tested to failure, and the documented capacity compared to the FEMA specified shore design capacity. Early warning signs of shore distress known as "fuses" characterized by audible cracking sounds, cupping of the wedges, or cracking of members were also evaluated during testing for their effectiveness and consistency. The performances of the laced post and plywood laced post shores were compared and recommendations made. / text

No description available.

Σκοπός είναι η διερεύνηση της τεχνολογίας των χερσαίων (onshore) ανεμογεννητριών και συγκεκριμένα των πυλώνων των ανεμογεννητριών. Αν εξετάσουμε το αιολικό δυναμικό στις χερσαίες περιοχές της Ευρώπης, παρατηρούμε αμέσως τις τεράστιες δυνατότητες ανάπτυξης ανεμογεννητριών. Παρατηρούμε επίσης την πλεονεκτική θέση της χώρας μας που εμφανίζεται να διαθέτει στο Αιγαίο πέλαγος μια από τις πλουσιότερες, σε αιολικό δυναμικό, περιοχές της Ευρώπης. Για να έχουμε όμως μεγαλύτερη απόδοση στην ισχύ μιας ανεμογεννήτριας πρέπει να αυξήσουμε το ύψος της έτσι ώστε να εκμεταλλευτούμε τις υψηλότερες ταχύτητες ανέμου σε μεγαλύτερα ύψη. Αυτό με την σειρά του θα επιφέρει πιο μεγάλα φορτία και επομένως μεγαλύτερες καταπονήσεις (εντατικά μεγέθη) στην βάση του πυλώνα καθώς η ανεμογεννήτρια προσομοιώνεται με σύστημα προβόλου. Ως συνέπεια τούτου θα πρέπει να αυξήσουμε την αντοχή του πυλώνα είτε αυξάνοντας το πάχος του υλικού της διατομής (αποφεύγεται – απαιτούνται μεγάλα πάχη συνεπώς μεγάλα κόστη), είτε αυξάνοντας τη διάμετρο της διατομής (αποφεύγεται – περιορισμένο πλάτος οδικού δικτύου που αποτρέπει την μεταφορά τμημάτων του πυλώνα της ανεμογεννήτριας με μεγάλες διατομές), είτε αυξάνοντας την αντοχή του υλικού της διατομής (αντικείμενο διατριβής). Στην παρούσα διατριβή γίνεται μελέτη βελτιστοποίησης σχεδιασμού των πυλώνων των ανεμογεννητριών με σύμμικτη διατομή χάλυβα-σκυροδέματος η οποία οδηγεί σε σχετικά μικρά πάχη διατομών, μικρής διαμέτρου, μεγάλης επιθυμητής αντοχής και μειωμένου κόστους υλικά. Αρχικά γίνεται η ανάλυση διατομής με στόχο την βελτιστοποίηση - ελαχιστοποίηση του κόστους για δεδομένη αντίσταση και στη συνέχεια η ανάλυση επαναλαμβάνεται για την βελτιστοποίηση του κόστους για δεδομένη δυσκαμψία. Στη συνέχεια με τη βοήθεια του σχεδιαστικού αναλυτικού προγράμματος ANSYS θα γίνει η σχεδίαση του πυλώνα της ανεμογεννήτριας όπου θα εφαρμοστούν τα προβλεπόμενα φορτία. Κατόπιν αυτού του σχεδιασμού διεξάγουμε πείραμα στο εργαστήριο όπου προσομοιώνουμε την ανεμογεννήτρια ώστε να συγκρίνουμε τα πειραματικά αποτελέσματα με την αναλυτική διαδικασία στο πρόγραμμα ANSYS. Γίνεται παράθεση και σχολιασμός των αποτελεσμάτων ώστε να προκύψουν τα συμπεράσματά μας και τελικώς γίνονται προτάσεις για περαιτέρω έρευνα όσον αφορά τα υλικά της διατομής των πυλώνων καθώς και την καλύτερη αξιοποίηση της αιολικής ενέργειας. / The aim is to investigate the technology of land (onshore) wind turbines and specifically for the pillars of wind turbines. If we investigate the wind potential in inland areas of Europe, we see immediately the enormous growth potential of wind turbines. We also observe the vantage point of our country that appears to have the Aegean Sea, one of the richest in wind potential areas of Europe. In order to increase the power of a wind turbine we must increase its height so as to take advantage of higher wind speeds at higher altitudes. This leads to higher loads and thus higher stresses (section forces) at the base of the tower as the wind turbine system is simulated with the cantilever system. As a consequence we should increase the strength of the pillar by increasing the thickness of the section material (to be avoided - large thicknesses therefore high costs required) or by increasing the diameter of the cross section (to be avoided - narrow road network that prevents transfer of the turbine pillar parts with large cross-sections), or by increasing the strength of the section’s material (subject of thesis). This thesis deal with the Design Optimization of Composite Cross Section Steel – Concrete Wind Turbine Towers which leads to relatively low thickness cross-sections, with small diameters, desirable high strength and reduced cost of materials. Initially we conduct sectional analysis in order to optimize - minimize the cost for a given resistance, and then the analysis is repeated for cost optimization for a given stiffness. Then we develop equations which correlate the moment, the stiffness and the cost of the wind turbine tower with the thicknesses of the materials (steel – concrete) which the cross section is composed of. Consequently we plot the equations that give the materials’ dimensions ranges when both the moment and stiffness is modified. Also we can understand how all this procedure affects the whole cost of the cross section. Then we conduct analysis and design of the wind turbine pillar with the analytical program ANSYS according to the design loads. Afterwards, lab-scale tests are conducted in order to model the wind turbine behavior. The experimental results are compared to the analytical observations. Finally we display and comment the results of that research so as to draw conclusions regarding the pillar design and the efficient wind energy utilization and present suggestions to future research.

Αντικείμενο αυτής της διπλωματικής εργασίας είναι η μελέτη και η αξιολόγηση δεδομένων που αφορούν τις εργασίες αποκατάστασης παραδοσιακών ιστορικών κτιρίων και πιο συγκεκριμένα των κτιρίων του Αγίου Όρους. Ειδικότερα, τα κτίρια που μας απασχόλησαν είναι οι Πύργοι και οι Αρσανάδες των Ιερών Μονών του Αγίου Όρους, όπου κάποιοι από αυτούς είναι ερειπωμένοι ενώ σε κάποιους άλλους έχουν γίνει εργασίες αποκατάστασης. Στα πρώτα στάδια της εργασίας, ερευνήθηκε βιβλιογραφία που αφορούσε γενικότερα το Άγιο Όρος, την αρχιτεκτονική του αλλά και τη γεωμορφολογία της περιοχής, ώστε να αποκτηθεί ένα επίπεδο εξοικείωσης με βασικές έννοιες και αρχές που θα μας ήταν απαραίτητες για την συνέχεια. Στα πλαίσια αυτής της μελέτης, δανειστήκαμε βιβλία από την Κεντρική Βιβλιοθήκη του Πανεπιστημίου Πατρών όπως και από των Αρχιτεκτόνων Μηχανικών Πάτρας. Επίσης, από την βιβλιοθήκη του ΤΕΕ Πατρών. Τέλος, επισκεφτήκαμε και δανειστήκαμε βιβλία από τις ανάλογες βιβλιοθήκες του Πανεπιστημίου αλλά και του ΤΕΕ που βρίσκονται στην Αθήνα. Στη συνέχεια, μετά από την μελέτη του υλικό που βρήκαμε, επισκεφτήκαμε στη Θεσσαλονίκη το Κέντρο Διαφύλαξης Αγιορείτικης Κληρονομιάς (Κε.Δ.Α.Κ) αλλά και την Αθωνική Τεχνική όπου έχει αναλάβει πολλά έργα αποκατάστασης σε Μονές και Πύργους του Αγίου Όρους. Εκεί βρήκαμε κυρίως τεχνικές μελέτες καθώς και φωτογραφικό υλικό από διάφορες επεμβάσεις στη χερσόνησο των συγκεκριμένων φορέων. Όλες οι μελέτες που έφτασαν στα χέρια μας έχρηζαν προσεκτικής σπουδής, διαλογής και καταγραφής, αλλά περισσότερο σεβασμού στον τρόπο σκέψης και στην πνευματική ιδιοκτησία που "δανειστήκαμε" από τους μελετητές. Έπρεπε με λίγα λόγια να εξάγουμε τις αρχές με τις οποίες έγιναν οι επεμβάσεις στα παραδοσιακά κτίρια και ασφαλώς, λαμβάνοντας τα στοιχεία που μας ενδιαφέρουν, να τις αποτυπώσουμε χωρίς να χάσουν την έννοια και τη σημασία τους. Αργότερα στην τελευταία φάση της διπλωματικής εργασίας, επισκεφτήκαμε το Άγιο Όρος και τους συγκεκριμένους Πύργους και αρσανάδες που επικεντρωθήκαμε, για την εκτενέστερη αλλά και προσωπική μελέτη και φωτογράφηση των στοιχείων που μας χρειαζόταν για την διεκπεραίωση της εργασίας. Στο Άγιο Όρος κάθε κατασκευή κρύβει και μια καινούργια γνώση για την παλιά τεχνολογία, αναλλοίωτη μετά από σχεδόν μια χιλιετία και αποτελεί μια πρόκληση για τους μηχανικούς και ένα πλούτο για εμάς τους φοιτητές. Προσπαθήσαμε και νομίζουμε πετύχαμε να φέρουμε κοντά στους συναδέλφους μας συγκεντρωμένα, στοιχεία σκόρπια που αφορούν την παραδοσιακή κατασκευή καθώς και τις μεθόδους αποκατάστασης αυτών, που είναι εκ των πραγμάτων δύσκολο να συναντηθούν σε κάποιο βιβλίο. Και εδώ πιστεύουμε πως η παρούσα εργασία συμβάλει. Στο Κεφάλαιο 1 παρατίθενται γενικά στοιχεία για την ιστορία της Αθωνικής χερσονήσου, για τη διοίκηση του Αγίου Όρους καθώς και τη συνταγματική του προστασία. Στο Κεφάλαιο 2 γίνεται μια αναφορά στα πλούσια φυσικά χαρακτηριστικά της χερσονήσου, όπως και στη γεωτεκτονική θέση που κατέχει και που επηρεάζει και τη σεισμικότητα της περιοχής. Στο Κεφάλαιο 3 επικεντρωνόμαστε στη δόμηση στο Άγιο Όρος. Συγκεκριμένα με την Αγιορείτικη αρχιτεκτονική και την προέλευσή της, αλλά και τους κανόνες και τις αρχές δόμησής της. Επίσης, ασχολούμαστε με τις κατηγορίες κτισμάτων που βρίσκονται στο Άγιο Όρος οι οποίες είναι οι Μονές, οι Σκήτες, τα Κελλία, οι Καλύβες, τα Καθίσματα και τα Ησυχαστήρια ή Ασκητήρια. Στο Κεφάλαιο 4 αναφερόμαστε στην αποκατάσταση των οικισμών που περιγράφτηκε, στους τρόπους και τις μεθόδους επέμβασης και συγκεκριμένα σε ξύλινα δομικά στοιχεία αλλά και τοιχοποιίες, στοιχεία που αποτελούν κυρίως τους οικισμούς του Αγίου Όρους. Στο Κεφάλαιο 5 ξεκινάμε με μια ιστορική αναφορά σε Πύργους και Αρσανάδες του Όρους καθώς και στην αρχιτεκτονική τους. Στη συνέχεια γίνεται η ταξινόμησή τους ανάλογα με τα κατασκευαστικά και μορφολογικά τους στοιχεία. Τέλος το μεγαλύτερο τμήμα της εργασίας αποτελεί η παρουσίαση των επεμβάσεων και των εργασιών αποκατάστασης που έχουν γίνει σε κάποιους από αυτούς ενώ παρουσιάζονται και δυο από τους πολλούς ερειπωμένους πύργους της χερσονήσου. Το Κεφάλαιο 6 κλείνει με κάποιες παρατηρήσεις και συμπεράσματα στα οποία καταλήξαμε μετά την επεξεργασία και μελέτη των στοιχείων που παρουσιάστηκαν προηγουμένως. / This project is about reconstruction work made in traditional and historical buildings. In addition, the project is focused in the traditional and historical buildings of holy mountain Agio Oros and especially those of the ports and the towers.