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Approved for public release; distribution is unlimited / The time varying development and structure of Dean vortices were studies using flow visualization. Observations were made over a range of Dean numbers from 40 to 200 using a transparent channel with mild curvature, 40:1 aspect ratio, and an inner to outer radius ratio of 0.979. Seven flow visualization techniques were tried but only one, a wood burning smoke generator, produced usable results. Different vortex characteristics were observed and documented in sequences of photographs space one quarter of a second apart at locations ranging from 85 to 135 degrees from the start of curvature. Evidence is presented that supports the twisting/rocking nature of the flow. / http://archive.org/details/flowvisualizatio00bell / Lieutenant, United States Navy

This thesis reports the design and development of novel voltammetric pH sensors for buffered, low-buffered and unbuffered media. pH sensors in stagnant and hydrodynamic environments were designed and developed for performing measurements using square wave voltammetry. Chapter 1 introduces the motivation of this project, the current development of electrochemical sensors, and the basic theory and techniques of electrochemistry concerned within the thesis. The existing development of carbon-based electrochemical sensors and the application of screen-printing technology in sensor fabrication are highlighted. Chapter 2 introduces the screen-printing technology and the fundamental methods of numerical simulation. In addition, reagents, equipment and software packages used in the thesis are listed in this chapter. In Chapter 3, a novel design of quinone derivative-based pH probes is presented for the application in stagnant weakly buffered media (< 1mM), based on previous studies of quinone compounds in buffered media. The results from the weakly buffered system is consistent with the results in buffered systems. To further extend the application of this design in unbuffered media, a numerical model of a pH-sensitive redox particle immobilised on an electrode was developed, which predicted that the accumulation of hydrogen ions near the electrode is the possible limiting factor for the performance of this design in unbuffered media. To develop a pH-monitoring technology for unbuffered media, Chapter 4 reports on the design, fabrication and testing of different electropolymerised-phenol derivative modified electrodes, which overcome the limitation of hydrogen ions accumulation. The results revealed that 2-(methylthio)phenol graphite resin electrodes have high accuracy (ca. 1% error) in unbuffered media, benchmarked by a commercial glass pH meter. This is the first detailed study on the v application of the economical and scalable technology in pH sensing in unbuffered environment. Chapter 5 presents a unique design of electrochemical pH sensors, free from the need to use a glass reference electrode. This design integrates a pH indicator and an internal reference electrode. Different designs of ferrocene screen-printed electrodes were tested as the internal reference electrode. The nafion-coated ferrocene screen-printed electrode showed stable peak potential in a wide pH range (pH 1 - 12) with good durability (stable in 500+ cycles of test). It was then cross connected with an alizarin electrode, forming the pH sensor free from a glass reference electrode. Chapter 6 describes novel designs of hydrodynamic pH sensors. The design of a microfluidic pH sensor modified by poly-sodium salicylate was firstly demonstrated. The sensor showed a Nernstian response in a wide pH range and, in hydrodynamic conditions, provided improved accuracy in unbuffered media compared to the stagnant state. For more convenient measurements, a novel rocking disc electrode was studied for pH sensing, modified with alizarin and poly-salicylic acid as pH indicators. The electrodes modified by both chemicals showed a Nernstian response in buffered media and the highest accuracy in unbuffered media was reached at 50 rpm.

The primary seismic response mode of freestanding slender building contents is rocking. Rocking is one of the most damaging response modes due to large accelerations at impact and the possibility of toppling. This study investigates the rocking response of contents within fixed-base and base-isolated buildings so that better-informed decisions can be made, either at the design stage for new structures or during the performance evaluation for existing structures, to mitigate the effects of the destructive rocking behaviour and consequently minimize injury, economic loss, and downtime. A 3D model of a hospital building was created in OpenSees and analyzed to obtain floor accelerations for a suite of 20 broadband ground motions. These motions were then used as input to compute the rocking responses of many building contents. The rocking responses were compared and contrasted to determine the effect of the block’s size, slenderness, floor level, and placement within a level. The rocking response of contents in buildings isolated with lead plug and triple friction pendulum bearings were compared to the fixed-base building to determine the effectiveness of isolation as a means to control rocking. Fragility curves were also created for the fixed-base and isolated buildings. The vertical component of the floor accelerations had little effect on the rocking response of contents. The significance of this is that the location of an object on a given story does not affect its rocking response. However, higher vertical accelerations did increase the likelihood of the object lifting off the floor. The rocking response of stocky contents increased from one story to the next, but as the slenderness increased this transition became less evident. Base isolation was found to be effective at reducing both the likelihood to uplift and overturn. The longer period systems provided superior protection despite the long period pulse like motion while the damping of the systems had little effect on the rocking response. / Thesis / Master of Applied Science (MASc) / During an earthquake slender building contents respond by rocking about their edges. Rocking causes damage to sensitive and brittle objects as well as safety hazards if it results in the overturning of heavy objects. One goal of this study was to define the rocking response of rigid contents in a conventional braced frame hospital. In general, larger and stockier objects were less likely to overturn. Also, overturning was more prevalent higher up in the building while the location of an object within a given story had little effect. Another objective was to determine the effectiveness of base isolation, a technique that decouples the motion of the building from the ground using flexible bearings, as a strategy to protect contents that are vulnerable to rocking during an earthquake. This was found to be quite effective at reducing both the occurrence of uplift (the initiation of rocking) as well as toppling.

The major objective of this study is to correlate the rocking foundation performance parameters with their capacity parameters and earthquake demand parameters using the results obtained from 142 centrifuge and shaking table experiments. It is found that seismic energy dissipation and permanent settlement of rocking foundations correlate well with rocking coefficient and Arias intensity of the earthquake, whereas the maximum moment and peak rotation of the foundation correlate well with peak ground acceleration. A numerical model, using the contact interface model available in OpenSees, is developed to simulate the performance of rocking foundations, and it is validated using experimental results. Though the numerical model predicts the moment capacity, seismic energy dissipation, and tipping-over stability of rocking foundations reasonably well, the model appears to overpredict the settlement of foundations. Furthermore, a parametric study showed that settlement reduces as initial vertical stiffness increases and is directly proportional to peak ground displacement.

Earthquakes represent a serious threat to the safety of masonry structures, with failure of these constructions under the influence of seismic action generally occurring via specific, well-documented collapse mechanisms. Analysis and assessment of these collapse mechanisms remains a challenge - while most analysis tools are time-consuming and computationally expensive, typical assessment methods are too simplified and often tend to underestimate the dynamic resistance of the structures. This dissertation aims to bridge the gap between the two through the development of a computational tool for the seismic collapse assessment of masonry structures, which uses rocking dynamics to accurately capture large displacement response, without compromising on computational efficiency. The tool could be used for rapid evaluation of critical mechanisms in a structure in order to prioritise retrofit solutions, as well as for code-based seismic assessment. The framework of the tool is first presented, wherein the rocking equations of motion are derived for a range of different collapse mechanisms, for any user-defined structural geometry, using as a starting point a geometric model of the structure in Rhino (a 3D CAD software). These equations of motion are then exported for solution to MATLAB. As a number of collapse mechanisms take place above ground level, a methodology to account for ground motion amplification effects is also proposed, while in the case of comparison of multiple different mechanisms, an algorithm to automatically detect critical mechanisms is presented. These developments make it possible to rapidly conduct a seismic analysis of structures with complicated three-dimensional geometries. However, the rocking equations of motion utilised thus far assume that the interfaces between the masonry macro-elements are rigid, which is not the case in reality. Thus, a flexible interface model is introduced, where the interfaces are characterised by a finite stiffness and compressive strength. This modelling strategy results in an inward shift of the rocking rotation points, and expressions are derived for these shifting rotation points for different interface geometries. The rocking equations of motion are also re-derived to account for the influence of the continuously moving hinges. However, the new equations tend to be highly non-linear - especially in the case of more complex collapse mechanisms. Thus to reduce computational burden, the semi-flexible interface model is proposed, which accounts for the shifting hinges in a more simplified manner than its fully-flexible counterpart. These new analytical models enable more accurate prediction of the seismic response of real-world structures, where interface flexibility tends to have a significant influence on dynamic response, while material damage in the form of crushing of the masonry also reduces dynamic resistance. The ability of the tool to be used for both seismic analysis and assessment is finally demonstrated by using it to perform a rocking dynamics-based analysis as well as a code-based seismic assessment of the walls of a historic earthen structure.

Gungstolen är en möbel med en säregen relation till sin brukare. Känsloladdad, lite opraktisk men omtyckt. Jag önskar att fler ska få uppleva glädjen och stoltheten i att bidra till skapandet av en möbel. En träram som fylls med personligheten av sin brukare. Kan detta också göra relationen till möbeln starkare? / A rocking-chair is an item of furniture with a peculiar relationship to its user. Emotive, slightly impractical but popular. My wish is that more people will be able to experience the joy and pride of contributing to the creation of an item of furniture. A wooden frame that is filled with the personality of its user. Might this also make the relationship to the rocking-chair even stronger?

Craft is the unification of the work of the hand and the work of the mind through material to produce an object with meaning. A craftsman is he or she who engages in the process of making with conscious intent and engagement with material and a broader scope of people and nature. Today, advances in mechanization and industry have allowed us to embrace a passivity that leaves us disconnected from the world and other people. We can look to craft, particularly with wood, as an antidote for this loss of connection. Through material specificity, the way handwork can offer the maker meaning about the place of the self in the world, and the way in which it illuminates the greater network of people, objects, and nature in which the maker exists, craft is a vehicle by which to produce knowledge otherwise unavailable through today’s methods of production and consumption. Through a personal account of the process of making a rocking chair out of wood and an examination of past and current scholarship surrounding craft and ontological aspects of identity, perception, and experience, the following examination, in conjunction with the actual process of making, aims to create a place for dialogue in the space between aesthetic philosophy and craft, creating a new paradigm for the role and definition of hand work today. It is an inquiry into the relationship between making and the production of knowledge. / text

It is not economical, nor practical, to design structures to remain elastic following a major earthquake event. Therefore, traditional seismic design methodologies require structures to respond inelastically by detailing members to accommodate significant plasticity (“plastic hinge zones”). It can be appreciated that, while life-safety of the occupants is ensured, structures conforming to this traditional design philosophy will be subjected to excessive physical damage following an earthquake. Thus, the direct costs associated with repair and the indirect costs associated with business interruption are expected to be great. Adding to this, structures located within a near-field region, close to a surface rupture, can be subjected to large velocity pulses due to a ground motion characteristic known as forward directivity in which a majority of the earthquake’s energy arrives within a very short period of time. Conventionally constructed systems are, in general, unable to efficiently deal with this ground motion. In the last two decades, advanced solutions have been developed to mitigate structural damage utilising unbonded post-tensioning within jointed, ductile connections, typically combined with hysteretic damping. While there is a growing interest amongst the engineering fraternity towards more advanced systems, their implementation into mainstream practice is slow due to the lack of understanding of unfamiliar technology and the perceived large construction cost. However, even considering such emerging construction technology, these systems are still susceptible to excessive displacement and acceleration demands following a major velocity-pulse earthquake event. In this research, the behaviour of advanced post-tensioned, dissipating lateral-resisting systems is experimentally and analytically investigated. The information learned is used to develop a robust post-tensioned system for the seismic protection of structures located in zones of high seismicity within near-field or far-field regions. A series of uniaxial and biaxial cyclic tests are performed on 1/3 scale, post-tensioned rocking bridge piers, followed by high-speed cyclic and dynamic testing of five 1/3 scale, post-tensioned rocking walls with viscous and hysteretic dampers. The experimental testing is carried out to develop and test feasible connection typologies for post-tensioned rocking systems and to improve the understanding of their behaviour under cyclic and dynamic loading. Insights gained from the experimental testing are use to extensively refine existing analytical modelling techniques. In particular, an existing section analysis for post-tensioned rocking connections is extended to assess the response of post-tensioned viscous systems and post-tensioned connections under biaxial loading. The accuracy of existing macro-models is further improved and a damping model is included to account for contact damping during dynamic loading. A Direct-Displacement Based Design (DDBD) framework is developed for post-tensioned viscous-hysteretic systems located in near-field and far-field seismic regions. The single-degree-of-freedom (SDOF) procedure is generic and has applications in new design and retrofit, while the multi-degree-of-freedom (MDOF) procedure is developed specifically for continuous bridge systems. Detailed design guidelines and flow-charts are illustrated to encourage the knowledge transfer from this report and to promote the use of emerging technology. Combining the information gathered from experimental testing, modelling and design, a probabilistic seismic hazard analysis is performed on three post-tensioned viscous-hysteretic bridge systems. In all cases, the post-tensioned bridge systems are shown to be more feasible than a traditional monolithic ductile bridge. Furthermore, while a post-tensioned hysteretic bridge is shown to be the most economic solution, the viscous-hysteretic system becomes more advantageous as the cost of fluid-viscous-dampers reduces.

This thesis presents a probability model to predict the maximum rotation of rocking bodies exposed to seismic excitations given specific earthquake intensity measures. After obtaining the nonlinear equations of motion and clarification of the boundaries applied to a rocking body to avoid sliding, a complete discussion is provided on the estimation of approximate period and equivalent damping ratio for the rocking motion. Thereafter, instead of using an iterative solution, which was previously proven defective, a new approximate technique is developed by finding the best representative ground motion intensities. Suitable transformation and normalization are applied to these intensities, and the Bayesian Updating approach is employed to construct a probability model. The proposed probability model is capable of accurately predicting the maximum rotation of a symmetric rocking block given displacement design spectra, peak ground acceleration, peak ground velocity, and arias intensity of an earthquake. This probabilistic model along with the approximate capacity of rocking blocks are used to estimate the fragility curves for rocking blocks with specific geometrical parameters. At the end, a comprehensive and practical form of fragility curves and numerical examples are provided for design purposes.