No description available.

The 7th German-Japanese Bridge Symposium, July 30-August 1, 2007 Osaka, JAPAN (GJBS07), full paper + extended abstract (p.142-143)

A half-zone experimental set-up was used to study the effects of various liquid bridge and helium flow parameters on the onset of thermocapillary convection in silicone oil liquid bridges. Experiments confirmed that helium flow has a stabilizing effect, with the effect increasing with helium velocity. Furthermore, helium flow in the same direction as surface flow due to Marangoni convection had a more stabilizing effect than countercurrent flow. It was established that increasing helium temperature has a mixed effect, producing a less stable bridge at low helium flow rates, but a more stable flow pattern at higher helium flow rates. Finally, it was confirmed that decreasing the cold disk temperature results in a decrease in critical temperature difference.

An investigation was performed for live load forces applied to soil-steel structures under shallow backfill depths, specifically a long span deeply corrugated box culvert. The work was also relevant to other types of flexible buried structures and loading scenarios. The investigation involved the application of both a robust experimental testing process and the development of 3-D finite element models. Full scale live load tests, performed in Dorchester NB, were executed to obtain a large sample of experimental data. The testing program was designed specifically to fully characterize the structural response of a long span box culvert to CHBDC design truck live loads. The program included live load testing at six different backfill depths with 21 unique truck positions per lift, with instrumentation at four separate rings. The experimental data was used to assess and calibrate the finite element models being developed to predict structural effects. The finite element software package ADINA was used to model the test structure in 3-D. The basics of model development, such as element types, boundary conditions, loads, and other analysis options were discussed. An orthotropic shell modeling approach to accurately describe the corrugated plate properties was developed. A number of soil constitutive models, both linear and nonlinear, were examined and evaluated. The data obtained from experimental testing was compared to the results obtained by the finite element modeling and the various soil models were evaluated. A parametric study was performed examining the sensitivity of modeling parameters. The impact of various assumptions made regarding the model was quantitatively established. The thesis provided guidance on the 3-D modeling of soil-steel structures allowing future researchers to study the factors which were significant to their design and field applications.

The traditional bridge evaluation process contains uncertainty that affects management decisions. Numerical models require assumptions regarding structural response, and code load models are inherently conservative to ensure uniform applicability. This research investigated how structural monitoring could reduce uncertainty in the evaluation and management process. Targeted instrumentation was implemented on the MacKay Bridge. Controlled load testing was conducted to refine an existing numerical model. Long-term monitoring was completed to compare extreme in-situ traffic effects with the Canadian Highway Bridge Design Code. Throughout the project, accuracy of information collected was a priority; deviation from code recommendations requires absolute confidence in the data. Outputs from controlled testing indicated that the existing numerical model for load distribution and structural response required minimal tuning. Long-term testing indicated that actual load effects are less than code requirements. Results from this thesis show that structural monitoring can reduce uncertainty in structural evaluation and management decisions for infrastructure.

This thesis investigates the architectural role of green belts and recreational zones as one solution to urban sprawl, ultimately creating healthier, more livable cities. A list of concepts and guidelines will be derived from both historical and modern green belt efforts, for the development of a more livable city in the 21st century. These concepts will then be tested as a tool on the city of Halifax. The concepts and guidelines will be used in the development of a green belt master plan. The plan will connect Halifax through existing and proposed parks and recreation. Secondly, it will develop a series of networks and connections enhancing the ability for alternate methods of transportation into and out of the urban core, facilitated by the design of a pedestrian bridge. Finally, a second design will support the existing program of mountain biking and create a unique architectural cycling experience for both the user and the observer.

A half-zone experimental set-up was used to study the effects of various liquid bridge and helium flow parameters on the onset of thermocapillary convection in silicone oil liquid bridges. Experiments confirmed that helium flow has a stabilizing effect, with the effect increasing with helium velocity. Furthermore, helium flow in the same direction as surface flow due to Marangoni convection had a more stabilizing effect than countercurrent flow. It was established that increasing helium temperature has a mixed effect, producing a less stable bridge at low helium flow rates, but a more stable flow pattern at higher helium flow rates. Finally, it was confirmed that decreasing the cold disk temperature results in a decrease in critical temperature difference.

This thesis is concerned with the seismic design of bridge piers. Particular attention is given to lifeline bridges with reinforced concrete hollow columns. Development of an analytical model to predict the stress-strain behaviour of reinforcing steel under dynamic cyclic loading is presented. Model predictions agreed well with previous tests on mild and high strength steel specimens. A generalised stress-strain model for plain or confined concrete under dynamic cyclic axial compression loading is presented. To verify the model, axial compression tests were carried out on 15 circular columns with spiral reinforcement, 16 rectangular walls and five square columns with rectilinear hoops. Theoretical predictions compared well with the experimental behaviour of the near full size specimens. A ductile design methodology for lifeline bridges is presented. Inelastic response spectra for "maximum credible" earthquake motions were derived for structures with concrete columns. These design spectra can be used to assess ductility demand of column hinges. Using the steel and concrete stress-strain models, a theoretical model is developed to predict the lateral load-deformation behaviour, and thus ductility capability, of reinforced concrete columns under axial load and cyclic flexure. Design charts are prepared to enable the rotational capacity of columns with confined concrete to be assessed. Finally, an experimental investigation into the seismic performance of ductile hollow reinforced concrete columns is described. Four specimens, 40 percent full size, containing different amountsof confining steel in the plastic hinge zone were subjected to a constant axial load and cyclic lateral displacements. An assessment of the effect of axial load and the amount of confining steel on the rotational capacity of the plastic hinge is made. The specimens performed satisfactorily, obtaining member ductilities between 6 and 8, without any significant strength degradation under cyclic loading. Predictions from the proposed lateral load- deformation model are found to compare well with the experimental results.

No description available.

The development of a DC-DC converter for use in a proposed range of one to ten kilowatt off-line power supplies is presented. The converter makes good use of established design practices and recent technical advances. The thesis begins with a review of traditional design practices, which are used in the design of a 3kW, 48V output DC-DC converter, as a bench-mark for evaluation of recent technical advances. Advances evaluated include new converter circuits, control techniques, components, and magnetic component designs. Converter circuits using zero voltage switching (ZVS) transitions offer significant advantages for this application. Of the published converters which have ZVS transitions the phase shift controlled full bridge converter is the most suitable, and assessments of variations on this circuit are presented. During the course of the research it was realised that the ZVS range of one leg of the phase shift controlled full bridge converter could be extended by altering the switching pattern, and this new switching pattern is proposed. A detailed analysis of phase shift controlled full bridge converter operation uncovers a number of operational findings which give a better and more complete understanding of converter operation than hitherto published. Converter design equations and guidelines are presented and the effects of the new improvement are investigated by an approximate analysis. Computer simulations using PSPICE2 are carried out to predict converter performance. A prototype converter design, construction details and test results are given. The results obtained compare well to the predicted performance and confirm the advantages of the new switching pattern.