OF THE BEHAVIOR OF FREE-STANDING
This thesis investigates the behavior of free-standing gabion walls in areas of mild seismicity. To investigate this behavior, three walls of varying internal cable patterns were constructed at a quarter-scale. These walls were tested with a mass shaker, and mode shapes, tone extractions, and damping ratios were calculated. A modal analysis was conducted using design spectra created from a suite of seven earthquakes from countries bordering Kenya. The corresponding lateral forces to these spectral displacements were found, and the restoring eccentricities from the soil restoring force were backed out through a summation of moments. All analysis was experimentally done due to the complexity of properly modeling the wall system for a secondary analytical comparison. This process was done under the assumption of linear behavior. Similarly, the criteria for failure involved the eccentricity of the restoring soil force exceeding the kern distance (assuming elastic behavior)—criteria that all three of the wall specimens met. However, further research into the nonlinear behavior of this wall type is suggested for future conclusions on free-standing gabion wall behavior.
Analysis of Stabilized Adobe in Rural East Africa
ANALYSIS OF STABILIZED ADOBE IN RURAL EAST AFRICA Grace Ying Yu Chen This project seeks to assist people in rural East Africa by proposing sustainable building methods which implement affordable and durable adobe bricks for construction. Adobe, one of the oldest sustainable building materials in the world, is strong when dry but lacks structural integrity when exposed to moisture. Chemical additives such as cement and lime are added into the adobe mix to protect the brick against moisture decomposition. Once the chemicals are added and the mix is formed into a brick, a stabilized adobe brick is formed. Cement, a stabilizer, is locally available in East Africa, but is generally unaffordable for families in rural areas. Lime is also locally available and costs about half the price of cement. This project investigates reducing the amount of cement to produce an economical and stabilized brick. The tested brick mixes, measured by volume, were • 10% cement • 5% cement • 5% cement+5% lime • 7% lime with sand • 7% lime with clay only • 10% lime with sand After testing these bricks by water jet, submersion, modulus of rupture, and compression, the 5% cement+5% lime mix and the 7% lime with clay mix proved to be viable options for economical and durable bricks. Analysis of Stabilized Adobe in Rural East Africa v The second half of this project contains summaries of research related to stabilized adobe and other soil building methods. A literature search shows that lime mixed with soil containing small particles rich in calcium carbonate and quartz produces proper cementation in the mix called carbonation.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.