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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Energy Based Seismic Performance Assessment Of Reinforced Concrete Columns

Acun, Bora 01 March 2010 (has links) (PDF)
Severe seismic events in urban regions during the last two decades revealed that the structures constructed before the development of modern seismic codes are the most vulnerable to earthquakes. Sub-standard reinforced concrete buildings constitute an important part of this highly vulnerable urban building stock. There is urgent need for the development and improvement of methods for seismic performance assessment of existing reinforced concrete structures. As an alternative to current conventional force-based assessment methods, a performance evaluation procedure for structural members, mainly reinforced concrete columns is proposed in this study, by using an energy-based approach combined with the low cycle fatigue concept. An energy-based hysteresis model is further introduced for representing the inelastic response of column members under severe seismic excitations. The shape of the hysteresis loops are controlled by the dissipated cumulative energy whereas the ultimate strength is governed by the low cycle fatigue behavior. These two basic characteristics are obtained experimentally from full scale specimens tested under constant and variable amplitude displacement cycles. The first phase of the experimental program presented in the study constitutes of testing sub-standard non-conforming column specimens. The second phase of testing was conducted on standard, code compliant reinforced concrete columns. A total number of 13 specimens were tested. The behavior of these specimens was observed individually and comparatively according to the performance based objectives. The results obtained from the experiments were employed for developing relations between the energy dissipation capacity of specimens, the specimen properties as well as the imposed displacement history. Moreover, the measured rotation capacities at the plastic regions are evaluated comparatively with the limits proposed by modern displacement-based seismic design and assessment provisions.
142

Buildings Under Recurring Near-field Earthquakes

Bayhan, Beyhan 01 October 2010 (has links) (PDF)
Prior to this study, to our best knowledge, no cast-in-place, older-type RC building has ever been subjected to near-field strong ground motions from three major earthquakes. This happened in an indirect way in Turkey over a time span of eleven years. Three identical buildings belonging to Ministry of Public Works and Resettlement (MPWR) that had been built to the same design templates, experienced March 13th 1992 Erzincan earthquake in Erzincan, November 12th 1999 D&uuml / zce earthquake in Bolu and May 1st 2003 Bing&ouml / l earthquake in Bing&ouml / l, respectively. The ground motion sensor stations were fortuitously nearby in an adjacent single-story building in Bolu and Bing&ouml / l. The station in Erzincan was in a single-story building about 2 km away from the case study building but we assume that the record applies to the building there. These three data represent characteristics of near-field ground motions and the distance of the sensor stations to the nearest fault trace was less than 10 km. The buildings sustained varying degrees of damage during the earthquakes and their damage survey was employed through site investigations. Given that the damage information, input motions, design drawings and material properties of the buildings are all known, this provided an opportunity to predict the structural damage to these buildings by proper modeling using the tools of current computational performance assessment procedures. In this circumstance, three dimensional (3D) analytical models of the MPWR buildings have been performed. Bi-directional excitations have been applied to the models by nonlinear time history analyses (NTHA). The results illustrate that NTHA are capable of indicating the occurrence of shear failure in captive columns / however, they overestimate the global damage level for all buildings. The overestimation is more significant in Erzincan case where the building sustained a pulse-type motion without significant distress.
143

A Nonlinear Equivalent Frame Model For Displacement Based Analysis Of Unreinforced Brick Masonry Buildings

Demirel, Ismail Ozan 01 December 2010 (has links) (PDF)
Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM buildings occupy significant portion of building stock in earthquake prone areas of the world as well as in Turkey. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of perforated walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The work presented in this thesis is about performance assessment of unreinforced brick masonry buildings in Turkey through nonlinear equivalent frame modeling technique. Reliability of the proposed model is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia and a dynamic shake table test on a half scale, two story URM building at the Ismes Laboratory at Bergamo. Good agreement between numerical and experimental results is found. Finally, pushover and nonlinear time history analyses of three unreinforced brick masonry buildings which are damaged in 1995 earthquake of Dinar is conducted using the proposed three dimensional nonlinear equivalent model. After displacement demands of the buildings are determined utilizing Turkish Earthquake Code 2007, performance based assessment of the buildings are done.
144

Seismic vulnerability assessment of wharf structures

Shafieezadeh, Abdollah 08 July 2011 (has links)
Serving as critical gateways for international trade, seaports are pivotal elements in transportation networks. Any disruption in the activities of port infrastructures may lead to significant losses from secondary economic effects, and can hamper the response and recovery efforts following a natural disaster. Particularly poignant examples which revealed the significance of port operations were the 1995 Kobe earthquake and 2010 Haiti earthquake in which liquefaction and lateral spreading of embankments imposed severe damage to both structural and non-structural components of ports. Since container wharf structures are responsible for loading and unloading of cargo, it is essential to understand the performance of these structures during earthquakes. Although previous studies have provided insight into some aspects of the seismic response of wharves, limitations in the modeling of wharf structures and the surrounding soil media have constrained the understanding of various features of the wharf response. This research provides new insights into the seismic behavior of wharves by using new and advanced structure and soil modeling procedures to carry out two and three-dimensional seismic analyses of a pile-supported marginal wharf structure in liquefiable soils. Furthermore, this research investigates the interaction between cranes and wharves and closely assesses the role of wharf-crane interaction on the response of each of these systems. For this purpose, the specific effect of wharf-crane interaction is studied by incorporating advanced models of the crane with sliding/uplift base conditions. To reduce the computational time required for three-dimensional nonlinear dynamic analysis of the wharf in order to be applicable for probabilistic seismic demand analysis, a simplified wharf model and an analysis technique are introduced and verified. In the next step probabilistic seismic demand models (PSDMs) are generated by imposing the wharf models to a suit of ground deformations of the soil embankment and pore water pressure generated for this study through free-field analysis. Convolving PSDMs and the limit states, a set of fragility curves are developed for critical wharf components whose damage induces a disruption in the normal operation of ports. The developed fragility curves provide decision makers with essential tools for maximizing investment in wharf retrofit and fill a major gap in seismic risk assessment of seaports which can be used to assess the regional impact of the damage to wharves during a natural hazard event.
145

Control and monitoring of sheet and film forming processes

Ramarathnam, Jaganath Unknown Date
No description available.
146

Perspectives on the implementation of the performance management and development system in the department of social development in Eastern Cape

Makas, Siphiwo Seymour January 2011 (has links)
<p>This research report, explores the challenges contributing to a non-effective implementation of performance and development management system at the Department of Social Development in Eastern Cape. My argument is that although the system has been fully implemented throughout the province and in all the layers of the department, there are still challenges that contribute to its ineffective implementation of this system. This research report debates a range of issues such as: challenges that revolve around the lack of proper&nbsp / knowledge and training in staff, non-alignment of performance contracts with operations of the department, attitudes of officials towards the system itself and the desired&nbsp / institution&rsquo / s operation that may contribute to its performance and achieve its objective of effective service delivery meaningfully. The research report also explores the paradigm shift&nbsp / of the department from a traditional &lsquo / welfarish&rsquo / approach to a one that focuses on social development. This research especially seeks to understand how the department seeks to plan for institutional change that will promote delivery its services to communities more. The reason for this focus derives from department is practice to provide services sectoralyand not in an integrated manner. Hence the critique, in this research is of the roles and responsibilities of all different layers of the department. This, I specifically argue for re-orientation of the department, not merely institutionally, but also strategically by adopting a social development approach to service delivery.</p>
147

Reconfiguring mining compressed air networks for cost savings / Johannes Izak Gabriël Bredenkamp

Bredenkamp, Johannes Izak Gabriël January 2014 (has links)
The world is currently experiencing major issues in the energy sector. The ever-growing human population, limited energy resources and the effect of greenhouse gas emissions have become major global concerns for the energy sector, including the electricity generation sector. This dilemma caused electricity providers to revise their generation methods and created a major need for consumers to utilise electricity more efficiently. Demand side management (DSM) is one initiative developed for consumers to efficiently utilise electricity. Due to their high electricity consumption and technical skills, mines are ideal targets for the implementation of DSM strategies. Therefore, the focus of this study was to investigate South African mines for possible implementation of DSM strategies on their compressed air networks. Compressed air networks at South African mines are relatively old and inadequately maintained. This causes inefficient distribution and use of compressed air. The study will therefore focus on reconfiguring mining compressed air networks for cost savings. Cost savings include financial savings on electricity bills, implementation costs and decreased maintenance. Through several investigations, the possibility of implementing energy savings strategies to reconfigure the compressed air networks of two South African mines was identified. Reconfiguring the networks would respectively entail interconnecting two shafts and relocating a compressor from an abandoned shaft to a fully productive shaft. Theoretical simulations were developed to determine the networks’ responses to the reconfiguration strategies. The simulations assisted in exposing the viability of implementing the reconfiguration strategies on the respective compressed air networks. Positive responses were obtained from the simulations and proposals were made to the respective mines for possible implementation. The proposed initiatives were implemented on the respective mines’ compressed air networks. After implementation of the interconnection strategy, a consecutive three-month performance assessment period commenced to prove the viability of the proposed savings. An average power saving of 1 700 kW was achieved during the performance assessment period. The proposed initiative to relocate the compressor is currently being implemented. A financial saving of approximately R8.9 million per annum was achieved by implementing the interconnection strategy. The large financial saving was due to the utilisation of the mine’s salvaged equipment. Further savings were achieved by the decreased maintenance on the mine’s compressors. Due to the successful implementation of the interconnection strategy, it is safe to state that cost savings can be achieved by reconfiguring mining compressed air networks. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014
148

Control and monitoring of sheet and film forming processes

Ramarathnam, Jaganath 11 1900 (has links)
Sheet and film forming processes refer to a set of processes that have a 2-dimensional sheet or film as their output. They are typically characterized by a scanning sensor which moves between the edges of the sheet in a periodic manner. This work is concerned with control and monitoring of such processes. There are three main contributions in this study. The first and foremost contribution is the reformulation of the Linear Quadratic Gaussian (LQG) objective function to give one the ability to trade-off between control over either dimension of the sheet. The second contribution is a method to derive the LQG trade-off surface between output variability in either dimension and input variance. The third contribution is a set of data driven techniques for performance assessment of these processes. Simulation results using the model used by Bergh and MacGregor (1987) are provided to support the proposed methods. / Process Control
149

Analysis Methods for Post Occupancy Evaluation of Energy-Use in High Performance Buildings Using Short-Term Monitoring

January 2011 (has links)
abstract: The green building movement has been an effective catalyst in reducing energy demands of buildings and a large number of `green' certified buildings have been in operation for several years. Whether these buildings are actually performing as intended, and if not, identifying specific causes for this discrepancy falls into the general realm of post-occupancy evaluation (POE). POE involves evaluating building performance in terms of energy-use, indoor environmental quality, acoustics and water-use; the first aspect i.e. energy-use is addressed in this thesis. Normally, a full year or more of energy-use and weather data is required to determine the actual post-occupancy energy-use of buildings. In many cases, either measured building performance data is not available or the time and cost implications may not make it feasible to invest in monitoring the building for a whole year. Knowledge about the minimum amount of measured data needed to accurately capture the behavior of the building over the entire year can be immensely beneficial. This research identifies simple modeling techniques to determine best time of the year to begin in-situ monitoring of building energy-use, and the least amount of data required for generating acceptable long-term predictions. Four analysis procedures are studied. The short-term monitoring for long-term prediction (SMLP) approach and dry-bulb temperature analysis (DBTA) approach allow determining the best time and duration of the year for in-situ monitoring to be performed based only on the ambient temperature data of the location. Multivariate change-point (MCP) modeling uses simulated/monitored data to determine best monitoring period of the year. This is also used to validate the SMLP and DBTA approaches. The hybrid inverse modeling method-1 predicts energy-use by combining a short dataset of monitored internal loads with a year of utility-bills, and hybrid inverse method-2 predicts long term building performance using utility-bills only. The results obtained show that often less than three to four months of monitored data is adequate for estimating the annual building energy use, provided that the monitoring is initiated at the right time, and the seasonal as well as daily variations are adequately captured by the short dataset. The predictive accuracy of the short data-sets is found to be strongly influenced by the closeness of the dataset's mean temperature to the annual average temperature. The analysis methods studied would be very useful for energy professionals involved in POE. / Dissertation/Thesis / M.S. Architecture 2011
150

Impact des contrats d’approvisionnement sur la performance de la chaîne logistique : modélisation et simulation

Amrani-Zouggar, Aïcha 20 November 2009 (has links)
Dans un contexte industriel où le partenariat d’entreprises devient une réponse stratégique aux exigences accrues du marché, le contrat d’approvisionnement apparaît progressivement comme un élément-clé de la gestion d’une chaîne logistique. La contribution de cette thèse comporte deux volets. Au plan méthodologique, il s’agit de fournir à l’entreprise un cadre d’analyse support à la contractualisation, permettant de relier clause, risque et performance en vue de définir, par une démarche instrumentée, les clauses pertinentes en adéquation avec le contexte industriel et la relation d’approvisionnement. Au plan des outils, un modèle de planification avec prise en compte des contraintes contractuelles et une plateforme de simulation ont été développés. Deux types de contrats d’approvisionnement (contrat d’engagement sur des quantités par période et contrat d’engagement sur des quantités par horizon) ont été simulés, mettant en évidence l’impact de ces derniers sur la performance locale (vue partenaire) et globale (vue de la chaîne logistique). / In high competitive industrial context where the collaborative partnership becomes a strategic answer to face the increased market requirements, supply contract gradually appears to be a key element in supply chain management. The contribution of this thesis is twofold. In one hand, methodological approach aims at providing deciders with contracting framework support that links clause, risk and performance in order to define, by instrumented approach, the relevant clauses to commit in adequacy with industrial context and supplying relationship. In the other hand, planning model including contractual constraints and simulation platform are developed. Two types of supply contracts (commitments on quantities per period and commitments on quantities per horizon) are simulated, highlighting the impact of these one on local performance (partner view) and global performance (supply chain view)

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