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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.
11

Reconstructing the Assemblage of Iron Artifacts from the Late Hellenistic Shipwreck at Kızılburun, Turkey

Rash, Kimberly 1981- 14 March 2013 (has links)
Artifacts found within the context of a shipwreck offer valuable insight into specific events surrounding a vessel’s journey and also have broader implications regarding the time period of the ship’s sinking. A collection of iron objects, excavated from the wreckage of a late Hellenistic ship carrying marble from the quarries at Proconnesus to the site of Claros, provides details of the implements vital to this ship’s passage. It was necessary that the completely corroded and encrusted iron artifacts undergo months of conservation, in the form of replication, stabilization of the iron where it survived, and restoration before they could be cataloged and researched thoroughly. The largest of the iron concretions was found to contain an anchor belonging to the ship. Being found on the same ship with wooden composite anchors, the iron anchor excavated at Kızılburun represents an important step in the transition in the use of wooden and lead composite anchors to their eventual replacement by anchors made solely of iron. The remaining identified objects comprise a collection of tools as well as three fasteners, all of which provide insight into the necessary equipment of an ancient wooden ship. Within the scope of this thesis, the conservation of each iron object is detailed, and a discussion of the implements enhances the understanding of their use aboard a seagoing vessel. Further research into similar objects and the development of each tool type offers insight into their value to the ancient seaman. Finally, a catalog of the artifacts is included, in order to provide measurements and technical drawings so that perhaps the currently unidentified artifacts can be compared to examples from other sites.
12

Undrained behavior of plate anchors subjected to general loading

Yang, Ming 14 January 2010 (has links)
This study presents a method for predicting the undrained behavior of plate anchors, including out-of-plane loading of simple plates and performance of suction embedded plate anchors (SEPLA). Three dimensional finite element models are used to investigate the behavior of square and rectangular plate anchors under normal loading with eccentricity in any direction. Upper bound analyses are performed for parallel loading and torsion loading. A simple model is then fit to the FE and upper bound solutions to determine required fitting parameters for both square and rectangular plates. The simple models can, in turn, be used both to predict anchor capacity and as yield surfaces for conducting plastic limit analyses, a method capable of predicting post yield anchor trajectory. The model predictions are shown in reasonable good agreement with the experimental results. For SEPLA, a theoretical model of plastic limit analysis is developed to predict the trajectory during the “keying” process and the ultimate capacity after the “keying” is complete. The predicted results are consistent with relevant known solutions.
13

Shear behavior of reinforced concrete T-beams strengthened with carbon fiber reinforced polymer (CFRP) sheets and CFRP anchors

Kim, Yun Gon, 1977- 30 January 2012 (has links)
The objective of this research is the evaluation of shear behavior of full-scale reinforced concrete T-beams strengthened with carbon fiber reinforced polymer (CFRP) sheets and CFRP anchors. Although the CRFP material has high tensile strength, premature failure due to debonding CFRP sheets prevents utilizing that strength. The use of CFRP anchors prevents this failure, so the CFRP sheets are able to reach ultimate strain. The current shear design is based on plasticity, which assumes that all steel (ductile material) stirrups, across the critical section yield at ultimate. However the strain in the CFRP (brittle material), is essential to estimate the shear contribution of CFRP. To evaluate the validity of CFRP strengthening for shear, 24 tests were conducted with several parameters including shear-span-to-depth ratio, depth of beams, different transverse reinforcement ratios, and the layout of CFRP strips. In addition, a simple shear behavior model was developed to explain the differences between ductile and brittle material. From test observation, the use of CFRP anchors resulted in U-wrap application to perform like continuous wrapping which implies that a CFRP strip reached rupture strain because the anchors prevented debonding failure. However, all FRP strips did not rupture simultaneously because the strain distribution across a critical crack was not uniform. The average strain across the critical crack was about 0.005. Therefore a conservative value of effective strain (0.004) was selected for design purposes. In addition, when a beam is strengthened with CFRP, interactions between the contributions of the CFRP, steel or concrete must be taken into account. Factors ka, ks, and kf were introduced in the proposed shear design equations. Factor ka reflects the change in the material contributions as the shear span to depth ratio (a/d ratio) changes in deep beams. Factors ks and kf account for the change in steel or CFRP shear contribution due to the change in the critical crack angle as well as the interactions between the steel and FRP transverse reinforcement. As the amount of either steel or FRP material increase, the efficiency of the other material decreases. / text
14

Effect of FRP Anchors on the FRP Rehabilitation of Shear Critical RC Beams and Flexure Critical RC Slabs

Baggio, Daniel Frank 20 February 2013 (has links)
The use of fiber-reinforced polymer (FRP) composites as a repair and strengthening material for reinforced concrete (RC) members has increased over the past twenty years. The tendency for FRP sheets to debond at loads below their ultimate capacity has prompted researchers to investigate various approaches and designs to increase the efficiency of FRP strengthening systems. Various anchors, wrapping techniques and clamps have been explored to postpone and/or delay the debonding process which results in premature failure. FRP anchors are of particular interest because they can be selected to have the same material properties as the FRP sheets that are installed for strengthening or repair of the RC member and can be done so using the same adhesives and installation techniques. This research study aimed to investigate the effectiveness of using commercially manufactured FRP anchors to secure FRP sheets installed to strengthen and repair RC beams in shear and RC slabs in flexure. Twenty one shear critical RC beams were strengthened in shear with u-wrapped FRP sheets and FRP anchors. Eight RC one-way slabs were strengthened in flexure with FRP sheets and FRP anchors. The test variables include the type of FRP sheets (GFRP,CFRP), type of FRP anchors (CFRP, GFRP) and the strengthening configuration. The test results of the shear critical RC beams revealed that the installation of commercially manufactured FRP anchors to secure externally applied u-wrap FRP sheets improved the shear behaviour of the strengthened beam. The installation of FRP anchors to secure u-wrapped FRP sheets provided an average 15% increase in the shear strength over companion unanchored beams and improved the ductility of failure experienced with the typical shear failure in beams. The use of FRP anchors allowed the FRP sheets to develop their tensile capacity. Premature failure by FRP debonding was eradicated with the presence of FRP anchors and the failure modes of the strengthened beams with FRP anchors was altered when compared to the companion unanchored beam. Additionally, as the width of a u-wrapped FRP sheet was increased; larger increases in strength were obtained when FRP anchors were used. The test results of the flexure critical RC slabs revealed that the installation of commercially manufactured FRP anchors to secure externally applied u-wrapped FRP sheets improved the behaviour of strengthened slabs. Installation of FRP anchors to secure flexural FRP sheets provided an average 17% increase in strength over companion unanchored beams. The use of FRP anchors allowed the FRP sheets to develop their full tensile strength. Premature failure by CFRP debonding was not eliminated with the presence of FRP anchors; rather the critical failure zone was shifted from the bottom soffit of the slab to the concrete/steel rebar interface. The failure modes of slabs with FRP anchors were altered for all specimens when compared to the companion unanchored slab. The effective strain in the FRP sheet was predicted and compared with the experimental results. The efficiency of FRP anchors defined as the ratio of effective strain in the FRP sheet with and without anchors was related to the increase in strength in beams and slabs. A good correlation was established between the FRP anchor efficiency and the increase in strength. A step-by-step FRP anchor installation procedure was developed and a model to predict the number of FRP anchors required to secure a FRP sheet was proposed. This is the most comprehensive examination of beams and slabs strengthened with FRP sheets and FRP anchors conducted to date. This study provides an engineer with basic understanding of the mechanics, behaviour and failure modes of beams and slabs strengthened with FRP sheets and anchors.
15

Career anchors of engineers in managerial positions in the South African power utility

Sithole, Ntombizodwa 12 October 2012 (has links)
Due to the introduction of the Employment Equity Act of 1998, the structure of management in South African companies has dramatically changed. This emphasizes the need for managerial generalists, especially now where we are faced with a competitive business environment and rapid changes in technology. Edgar Schein (1978) in the (Academy of Management Journal 1996) maintains that these changes have resulted in people forming what he called “internal careers”. He described an “internal career” as a subjective sense of where one is going in one’s working life. He continued to describe the external career as something that is more about formal stages and roles, well defined by organisational policies and societal concepts regarding what an individual can expect in an occupational structure”. The complexities in the occupational environment have implications for career development, and it has obviously become crucial that people form what Edgar Schein regarded a self-concept, to be a ““career anchor” that holds a person’s internal career together even if they experience intense changes in their external career”. An individual’s “career anchor”, as defined by Schein (1978; 1985; 1990; 1993), comprises of a person’s 1) “self-perceived aptitudes and capacities; 2) basic values; and most important, 3) the evolved sense of motives and desires as they apply to the career”. Using the instrument called the Career Orientations Inventory (COI) developed by Edgar Schein, the objective of this study to systematically examine the primary career anchors of a sample of engineers in management positions at one of the utilities in South Africa. This is a quantitative study which uses a statistical analysis to substantiate engineers’ motivation for pursuing managerial positions instead of remaining specialists. The results from this study will have a major contribution in the field of Psychology and in particular, Career Psychology. / Dissertation (MCom)--University of Pretoria, 2012. / Human Resource Management / unrestricted
16

Performance of Adhesive and Cementitious Anchorage Systems

Mendoza, Mirna 11 July 2017 (has links)
Post-installed anchoring systems are used extensively in Massachusetts Department of Transportation (MassDOT) projects due their ease of attachment to existing structures. However, recommendations on materials from various manufacturers are currently lacking for certain situations such as long-term tension loading. The purpose of the investigation presented in this thesis was to provide guidance on the use of anchoring systems to MassDOT. This research project evaluated the behavior of adhesive and cementitious bonded anchoring systems per the Stress-versus-Time-to-Failure approach found in the provisional standard AASHTO TP-84 in order to provide recommendations pertaining to the test method. Supplemental short-term anchor pullout tests were conducted using the best performing materials as evaluated by AASHTO TP-84 to study the effects of certain in-service and installation parameters on bond strength. The parameters studied included installation direction and extreme in-service temperatures. Polymer characterization testing of adhesive products were also conducted in order to comment on technique usefulness for field quality assurance/quality control of field installed bonded anchor materials.
17

Geometric Routing Without Geometry

Jadhav, Rajesh 02 May 2007 (has links)
No description available.
18

Pullout Strength of Epoxy Anchors Installed Underwater

Blanchette, Jeffrey Lee 01 December 2012 (has links)
This work presents the development of a test program and the results from the final round of testing to better understand the effect a submerged anchor installation has on the pullout strength of epoxy anchors. Two different epoxies were tested at embedment depths of two, four, and six bar diameters. These tests utilized three distinct installation procedures under dry and submerged conditions. The testing program occurred over five phases, with the final round used in analysis consisting of 24 anchor pullout tests. These tests showed that the presence of water did not have an effect on the epoxy bond when anchor holes were cleaned dry and installed underwater, but it did have a significant impact on the ability to consistently clean each anchor when it was submerged.
19

Analytical and Experimental Studies of Drag Embedment Anchors and Suction Caissons

Beemer, Ryan 2011 May 1900 (has links)
The need for experimental and analytical modeling in the field of deep water offshore anchoring technologies is high. Suction caisson and drag embedment anchors (DEA) are common anchors used for mooring structures in deep water. The installation process of drag embedment anchors has been highly empirical, employing a trial and error methodology. In the past decade analytical methods have been derived for modeling DEA installation trajectories. However, obtaining calibration data for these models has not been economical. The development of a small scale experimental apparatus, known as the Laponite Tank, was developed for this thesis. The Laponite Tank provides a quick and economical means of measuring DEA trajectories, visually. The experimental data can then be used for calibrating models. The installation process of suctions caissons has benefited from from a more rational approach. Nevertheless, these methods require refinement and removal methodology requires development. In this thesis, an algorithm for modeling suction caisson installation in clay has been presented. An analytical method and modeling algorithm for removal processes of suction caissons in clay was also developed. The installation and removal models were calibrated to field data. These analytical and experimental studies can provide a better understanding of installation of drag embedment anchors and the installation and removal of suction caissons.
20

Experimental testing of pure translation and rotation loading of drag anchors

Ganjoo, Karan 21 December 2010 (has links)
Mobile offshore drilling units are being used in the Gulf of Mexico to produce oil and gas. Anchoring systems such as drag embedment anchors and vertically loaded anchors are used to keep these units in place. Past mooring system failures due to hurricanes in 2004 and 2005 initiated a need to better understand the performance of these anchors to in-plane and out-of-plane loading conditions. In-plane and out-of-plane loading cause the anchor to translate or rotate in the directions of its six degrees of freedom. Behavior and holding capacity of the anchors when loaded in each of is six degrees of freedom are important in understanding and predicting their behavior. An experimental program was devised to investigate the behavior of anchors in pure translation and rotation loading. The scaled-model anchors were embedded at a measured depth in a soil bed of clay with an undrained shear strength between 10 and 20 psf and then loaded to failure. A rotation testing frame was designed to impose rotational loading in the yaw, roll and pitch directions. Test results from the experimental program are consistent and repeatable. The bearing factors for pure bearing fell well within the range of existing experimental and analytical studies on simple plates. Bearing factors for in-plane and out-of-plane shear and for all rotations are higher than those for simple plates due to presence of the shank. When the resistance is normalized by area of the fluke, the wider model provide greater normalized resistance to yawing, similar normalized resistance to pitching and rolling and less normalized resistance to bearing and shearing. It was concluded that the holding capacity of an anchor in its six degrees of freedom depends largely on its geometry, including the fluke and the shank. / text

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