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Effects of Bond Deterioration Due to Corrosion on Seismic Performance of Reinforced Concrete StructuresKivell, Anton Richard Lean January 2012 (has links)
Reinforced concrete structures deteriorate throughout their lifetime. This is particularly apparent in structures subjected to aggressive environments, which results in corrosion of reinforcing steel. Designers make allowances for accelerated deterioration in these environments in an attempt to ensure the durability of the structure. To combat corrosion, improved concrete characteristics and additional concrete cover are used to increase the protection provided by concrete to reinforcing. In spite of these measures, cracking of structures in service and from natural hazards can limit the effectiveness that these measures provide. Ultimately, this results in structures suffering from corrosion, which affects their strength, stiffness, and ductility. While strength reduction can be associated directly with a reduction in bar area, impacts on stiffness and ductility are associated with more complex mechanisms, one of which is bond deterioration. A key assumption in reinforced concrete design is that there is perfect bonding between steel reinforcing and surrounding concrete to allow for strain compatibility to be assumed. Perfect bond does not exist and diminished bond performance due to corrosion deterioration further violates this assumption, the effects of which are not fully understood.
This thesis investigates the effects of bond deterioration due to corrosion on the seismic performance of reinforced concrete structures. 60 monotonic and cyclic pull-out tests were undertaken on corroded reinforced concrete specimens, with corrosion levels ranging from 0% to 25% reinforcing mass loss. Additional tests were also conducted on specimens with variations in the amount of confining steel to simulate losses in confinement associated with corrosion of confining steel. Experimental results were used to develop corrosion and confinement dependent cyclic bond-slip model.
The proposed bond-slip model was then used to modelling pull-out of reinforcing bars detailed in accordance with New Zealand design standard NZS3101. Analyses were performed at a range of corrosion levels, levels of confinement, and uncorroded bond strengths. These showed that pull-out of reinforcement occurred at as little as 8% corrosion in low strength, unconfined conditions.
Multi-spring modelling of standard reinforced concrete columns, representing a bridge pier to foundation connection, was performed at the full range of deterioration with allowance for bond slippage. These analyses showed significant reductions in stiffness occurring with increased corrosion levels as well as reduced ductility and possible pull-out of reinforcement.
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Comparative geomorphology of two active tectonic structures, near Oxford, North CanterburyMay, Bryce Derrick January 2004 (has links)
The North Canterbury tectonic setting involves the southward propagating margin of easterly strike-slip activity intersecting earlier thrust activity propagating east from the Alpine Fault. The resulting tectonics contain a variety of structures caused by the way these patterns overlap, creating complexities on the regional and individual feature scale. An unpublished map by Jongens et al. (1999) shows the Ashley-Loburn Fault System crossing the plains from the east connected with the Springfield Thrust Fault in the western margins, possibly the southern limit of the east-west trending strikeslip activity. Of note are two hill structures inferred to be affected by this fault system. View Hill to the west, is on the south side of this fault junction, and Starvation Hill further east, was shown lying on the north side of a left stepover restraining bend. During thrust uplift and simple tilting of the View Hill structure, at least two uplift events post date last Pleistocene aggradation accounting for variations in scarp morphology. Broad constraints on fault dip and the age of the displacement surface suggest that slip-rates are in the order of 0.5 mm/year. East from View Hill, the strike-slip fault was originally thought to curve northeast, around the southeast of Starvation Hill. But there is neither evidence of a scarp, nor other clear evidence of surface faulting at Starvation Hill, which poses the question of the extent to which folding may reflect both fault geometry and fault activity. Starvation Hill is a triangular shape, with a series of distinctive smooth, semi-planar surfaces, lapping across both sides of the hill at a range of elevations and gradients. These surfaces are thought to be remnants of old river channels, and are indicative of tilting and upwarping of the hill structure. 3D computer modelling of these surfaces, combined with studies of the cover sequence on the hill, resulted in inferences being drawn as to the location of hinge lines of a dual-hinged anticline and an overview of the tectonic history of the hill. This illustrates the potential to apply topographical and geomorphic studies to the evolution of geometrically complex structures Starvation Hill is interpreted to be the result of two fault-generated folds, one fault trending north, the other, more recent fault, trending east. These two faults are thought to be sequentially developed segments of the original fault zone inferred by Jongens et al. (1999) but with reinterpreted location and mechanism detail. The presence of two faults has resulted in overprinted differential uplift of the structure, which has been significantly degraded, especially in the southwest corner of the hill. The majority of the formation of the northerly trending structure of Starvation Hill is inferred to be pre-Otiran, with uplift of the later east trending structure continuing into the late Pleistocene and Holocene.
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Real-time Cycle-slip Detection and Correction for Land Vehicle Navigation using Inertial AidingKaraim, MALEK 07 May 2013 (has links)
Processing GPS carrier-phase measurements can provide high positioning accuracy for several navigation applications. However, if not detected, cycle slips in the measured phase can strongly deteriorate the positioning accuracy. Cycle slips frequently occur in areas surrounded by trees, buildings, and other obstacles. The dynamics experienced by the GPS receiver in kinematic mode of navigation also increases the possibility of cycle slips. Detection and correction of these cycle-slips is essential for reliable navigation. One way of detecting and correcting for cycle slips is to use another system to be integrated with GPS. Inertial Navigation Systems (INS), using three-axis accelerometers and three-axis gyroscopes, is integrated with GPS to provide more reliable navigation solution. Moreover, INS was utilized in the past for GPS cycle slip detection and correction. For low cost applications, Micro-Electro-Mechanical-Systems (MEMS) accelerometers and gyroscopes are used inside INS. For land navigation, reduced inertial sensor system (RISS) utilizing two accelerometers, one gyroscope, and the vehicle odometer was suggested. MEMS-based RISS has the advantage of using less number of MEMS-based gyroscopes and accelerometers thus reducing the overall cost and avoiding the complex error characteristics associated with MEMS sensors. In this thesis, we investigate the use of MEMS – based RISS to aid GPS and detect and correct for cycle slips. The Kalman filter was employed in centralized fashion to integrate the measurements from both GPS and RISS. This thesis research also offers a new threshold selection criterion resulting in a more robust cycle slip detection and correction. The proposed method was tested in different scenarios of road tests in land vehicle. Results show accuracy
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improvement over the conventional double differenced pseudoranges-based integrated system. Moreover, the adaptive selection criterion of the detection threshold proposed in this thesis improves the detection rate, especially in the case of small-sized cycle slips. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2013-05-06 18:11:57.076
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Modelling evolution of anisotropy in metals using crystal plasticityChaloupka, Ondrej 03 1900 (has links)
Many metals used in modern engineering exhibit anisotropy. A common
assumption when modelling anisotropic metals is that the level of anisotropy is
fixed throughout the calculation. As it is well understood that processes such as
cold rolling, forging or shock loading change the level of anisotropy, it is clear
that this assumption is not accurate when dealing with large deformations.
The aim of this project was to develop a tool capable to predict large
deformations of a single crystal or crystalline aggregate of a metal of interest
and able to trace an evolution of anisotropy within the material.
The outcome of this project is a verified computational tool capable of predicting
large deformations in metals. This computational tool is built on the Crystal
Plasticity Finite Element Method (CPFEM). The CPFEM in this project is an
implementation of an existing constitutive model, based on the crystal plasticity
theory (the single crystal strength model), into the framework of the FEA
software DYNA3D® .
Accuracy of the new tool was validated for a large deformation of a single
crystal of an annealed OFHC copper at room temperature. The implementation
was also tested for a large deformation of a polycrystalline aggregate comprised
of 512 crystals of an annealed anisotropic OFHC copper in a uniaxial
compression and tension test. Here sufficient agreement with the experimental
data was not achieved and further investigation was proposed in order to find
out the cause of the discrepancy. Moreover, the behaviour of anisotropic metals
during a large deformation was modelled and it was demonstrated that this tool
is able to trace the evolution of anisotropy.
The main benefit of having this computational tool lies in virtual material testing.
This testing has the advantage over experiments in time and cost expenses.
This tool and its future improvements, which were proposed, will allow studying
evolution of anisotropy in FCC and BCC materials during dynamic finite
deformations, which can lead to current material models improvement.
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MODELING PARTICLE FILTRATION AND CAKING IN FIBROUS FILTER MEDIAHosseini, Seyed Alireza 22 July 2011 (has links)
This study is aimed at developing modeling methodologies for simulating the flow of air and aerosol particles through fibrous filter media made up of micro- or nano-fibers. The study also deals with modeling particle deposition (due to Brownian diffusion, interception, and inertial impaction) and particle cake formation, on or inside fibrous filters. By computing the air flow field and the trajectory of airborne particles in 3-D virtual geometries that resemble the internal microstructure of fibrous filter media, pressure drop and collection efficiency of micro- or nano-fiber filters are simulated and compared with the available experimental studies. It was demonstrated that the simulations conducted in 3-D disordered fibrous domains, unlike previously reported 2-D cell-model simulations, do not need any empirical correction factors to closely predict experimental observations. This study also reports on the importance of fibers’ cross-sectional shape for filters operating in slip (nano-fiber filters) and no-slip (micro-fiber filters) flow regimes. In particular, it was found that the more streamlined the fiber geometry, the lower the fiber drag caused by a nanofiber relative to that generated by its micron-sized counterpart. This work also presents a methodology for simulating pressure drop and collection efficiency of a filter medium during instantaneous particle loading using the Fluent CFD code, enhanced by using a series of in-house subroutines. These subroutines are developed to allow one to track particles of different sizes, and simulate the formation of 2-D and 3-D dendrite particle deposits in the presence of aerodynamic slip on the surface of the fibers. The deposition of particles on a fiber and the previously deposited particles is made possible by developing additional subroutines, which mark the cells located at the deposition sites and modify their properties to so that they resemble solid or porous particles. Our unsteady-state simulations, in qualitative agreement with the experimental observations reported in the literature, predict the rate of increase of pressure drop and collection efficiency of a filter medium as a function of the mass of the loaded particles.
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Investigation of the slip modulus between cold-formed steel and plywood sheathingMartin, Geoff January 1900 (has links)
Master of Science / Department of Architectural Engineering and Construction Sciences / Kimberly Waggle Kramer / Bill Zhang / Cold-formed steel members quickly are becoming a popular material for both commercial and
residential construction around the world. Their high strength to weight ratio makes them a
viable alternative to timber framing. In most cases cold-formed steel is used as a repetitive
member in floor, wall, or roof assemblies. Structural sheathing is used in conjunction with the
framing members in order to transfer loads between individual members. This sheathing is
connected mechanically to the cold-formed steel through a variety of methods. The most
common method uses screws spaced at close intervals, usually between 6 to 12 inches on center.
When such assemblies are constructed, load is transferred from the sheathing through the
connectors into the cold-formed steel, forming a composite assembly in which load is transferred
and shared between two materials, providing a higher strength and stiffness over individual
members themselves. The amount of load that can be transferred is dependent on the amount of
slip that occurs when the assembly is loaded. This slip value describes the amount of composite
action that takes place in the assembly. The amount of slip can be described by a value called
the slip modulus. The composite, or effective, bending stiffness can be calculated using the slip
modulus. In current design of cold-formed steel composite assemblies this composite action is
not being taken into account due to a lack of research and understanding of the composite
stiffness present in these assemblies. Taking composite action into account can lead to decreased
member sizes or increased spacing of members, thereby economizing design. Furthermore,
improved understanding of the effective stiffness can lead to more accurate design for vibrations
in floor systems. This thesis tests cold-formed steel plywood composite members in an effort to
verify previously established slip modulus values for varying steel thicknesses and establishes
new values for varying fastener spacings. The slip modulus values obtained are used to calculate
effective bending stiffness values in an effort to prove that composite action should be utilized in
design of cold-formed steel composite assemblies.
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The influence of fastener spacing on the slip modulus between cold formed steel and wood sheathingLoehr, Weston January 1900 (has links)
Master of Science / Civil Engineering / Hani G. Melhem / Bill Zhang / Composite action is the joint behavior of two elements connected or bonded together. It is a phenomenon that is utilized in several applications throughout engineering. Previous studies have shown that cold formed steel (CFS) sheathed with structural wood panels exhibits a degree of partial composite action behavior. However currently in the design process, CFS and wood sheathing systems are considered separately in a non-composite manner due to the absence of sufficient supporting data. These systems can include the floors, roofs, and walls of a building. In order to determine the level of composite action present, the slip modulus is needed. The slip modulus describes the relationship between the shear force and the displacement exhibited by two elements in a composite system. The scope of this research is to determine the influence of fastener spacing on the slip modulus and provide a foundation of information to fully define the composite action between CFS and wood sheathing.
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The effect of voltage dips on wound rotor induction motors used in slip energy recovery drives – implications for convertersDavies, Simon Quail 31 October 2006 (has links)
Student Number : 0004041J -
MSc dissertation -
School of Electrical and Information Engineering -
Faculty of Engineering / Slip energy recovery (SER) drives are used extensively in industry as they offer cost effective speed control of large wound rotor induction motors. The biggest disadvantage associated with the use of SER drives is the vulnerability of the rotor circuit converters to power system disturbances such as voltage dips. The failure of converters as a result of voltage dips is a problem associated with the use of these particular drives.
The aim of this research is to better understand the stresses on rotor circuit converters as a result of voltage dips at the terminals of the motor. The rotor transients developed by a wound rotor induction motor are investigated for a range of three phase and single phase voltage dips. Simulations conducted in the Alternative Transients Program (ATP) supplement measurements conducted on a simplified SER circuit. The results confirm that voltage dips cause significant stresses on the converters in the rotor circuit. Good correlation was obtained between simulated and measured results. This work allows for a better understanding of the response of wound rotor induction motors to voltage dips and identifies the threat that voltage dips impose on the SER rotor circuit converters.
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COMPUTATIONAL AND EXPERIMENTAL INVESTIGATION ON THE WETTING BEHAVIOR OF DROPLET-FIBER SYSTEMSAziz, Hossain 01 January 2019 (has links)
Interaction of a liquid droplet and a fiber or layer of fibers is ubiquitous in nature and in a variety of industrial applications. It plays a crucial role in fog harvesting, coalescence filtration, membrane desalination, self-cleaning and fiber based microfluidics, among many others. This work presents a quantitative investigation on the interactions of a droplet with a fiber or layers of fibers. More precisely, the present work is focused on 1) predicting the effects of fiber’s size and material on its ability to withhold a droplet against external forces and on the liquid residue left on the fiber after the droplet detachment, 2) predicting the outcome of two fibers competing to attract the same droplet, and 3) predicting the wetting stability of a droplet deposited on a layer of electrospun fibers. This work is comprised of series of computational and experimental studies for mutual validation and/or calibration. The simulations were conducted using the Surface Evolver code and the experiments were devised using a ferrofluid and a magnet.
We also investigated the drag reduction performance of fibrous coatings because of its close connection with droplet-fiber interaction. We started by studying the drag reduction performance of a superhydrophobic granular coating because of its geometrical simplicity. We modeled the flow of water over the granular coating and studied the effects of hydrostatic pressure and microstructural properties on the drag reduction performance of the coating. We then examined the drag reduction performance of a lubricant infused surface with trapped air made of layers of parallel fibers (FLISTA). A mathematical model was developed to predict the shape of the water-lubricant interface and lubricant-air interface under a given hydrostatic pressure. This information was used to solve the flow field over the coating in a Couette configuration to find the effects of hydrostatic pressure and microstructural properties of the coating on its drag reduction performance.
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The situational language intervention programme (SLIP) : the theoretical background and outline of the programmeHall, Phillip, n/a January 1988 (has links)
The general aim of the thesis is to show how The Situational Language Intervention Programme (SLIP) was formulated in order to include the
critical factors of: the cognitive abilities and linguistic
characteristics of the intellectually handicapped; pragmatics, semantics
and syntax and the four models of language acquisition; the criteria
that guide language intervention programme development; the use of
precise and systematic teaching methods that stimulate the use of
language in the students' environment. The general objective of both
SLIP and this thesis is to show how to increase moderately to severely
intellectually handicapped adolescents' language-communication through
the appropriate use of the forms of language applied to its functions in
a specific range of situations.
Chapter Two of the thesis is concerned with the cognitive abilities of
intellectually handicapped people and the implications of intellectual
handicap on communication and language development. In addition it
discusses, stage by stage, the positive and negative markers of language
acquisition. These markers illustrate to the teacher the signs of
linguistic retardation at each stage of language learning.
The contents of Chapter Three provide an outline of the four models of
language acquisition, i.e. Pragmatic, Semantic/Cognitive,
Psycholinguistic/Syntactic and Behavioural. Those models contribute to
our understanding of how language develops and illustrate to us the
complex nature of language acquisition. In addition, this discussion
documents the past and current research viewpoints and draws our
attention to the limitations that existing theories have in providing a
"full�blown" model of language acquisition. Furthermore, Chapter Three
is stating that the recent analysis of language-training for
communication disordered and intellectually handicapped students has
shown that a more balanced study of the semantic and pragmatic factors in
language acquisition is emerging. This chapter is urging teachers to
re-analyze, re-evaluate and modify their language intervention programmes
by integrating the syntactic, semantic and pragmatic factors.
Both the contents of Chapters Two and Three are demonstrating that it is
necessary to address the theoretical viewpoint and academic findings both
of which are important aspects of the role of the interventionist. They
have to be addressed if the teacher is to make judgments concerning the
efficacy of different models in attaining certain goals. Such factors
govern the utilization and integration of certain approaches and
procedures.
The contents of Chapters Four and Five discuss how the language
interventionist can lead the intellectually handicapped student into
increased language usage and communicative competence. Chapter Four is
concerned with the current critical issues and developments in:
curriculum and programme design for the moderately/severely
intellectually handicapped adolescent; criteria to guide programme
development and direction of language intervention; direct instruction
techniques; augmentative communication systems and their basic programme
guidelines.
Chapter Five outlines the framework of the Situational Language
Intervention Programme (SLIP) which was designed and implemented by the
author. The content and procedures utilized by SLIP are greatly
influenced by the contents of Chapters Two, Three and Four. This
influence is demonstrated in the discussion concerning SLIP's: aims and
objectives; content and design decisions; selection of forms to be
taught; sequencing; teaching procedures and methods of instruction.
Chapter Five also discusses the implementation of SLIP.
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