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.
Scaffolds Containing Spirulina sp. LEB 18 Biomass: Development, Characterization and Evaluation of In Vitro Biodegradation.
Polymer nanofibers are nanomaterials that can be used as scaffolds in tissue engineering. The objective of this study was to develop, characterize and evaluate the in vitro degradation of a biomaterial consisting of nanofibers produced from biodegradable and biocompatible polymers with potential applications as a scaffold for tissue regeneration and containing Spirulina sp. LEB 18 biomass as the bioactive compound. The polymers used were poly(hydroxybutyrate-co-hydroxyvalerate) and polycaprolactone. The polymeric solutions exhibited sufficiently high viscosity to produce uniform nanofibers with diameters between 335 and 617 nm. The applied conditions were as follows: a voltage of 25 kV, a distance from the capillary to the collector of 120 mm, a capillary diameter of 0.80 mm, and 12% polycaprolactone and a blend of 5% polycaprolactone and 10% poly(hydroxybutyrate-co-hydroxyvalerate). The biomass was incorporated into the nanofibers at a concentration of 3%, and the incorporation was confirmed using confocal microscopy. The nanofibers were characterized using differential scanning calorimetry and thermogravimetric analysis, which showed that the addition of biomass did not alter the thermal properties of the biomaterial. The addition of biomass improved the tensile strength and elongation of the scaffolds compared with those produced with polymers alone. A biodegradation assay showed enzymatic action toward the biomaterial, simulating the behavior of natural tissue. Based on the analysis, it was concluded that the scaffolds that were produced have the potential to be applied in the field of tissue regeneration as biomaterials with pharmacological properties.