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This investigation looked at the climatic variables affecting the durability of earth buildings and the relationship between these climatic variables and their laboratory counterparts, with the aim of providing a means whereby performance in the field under known climatic conditions can be predicted by performance in the laboratory. The investigation showed that the major climatic factors influencing the erosion of earth walls due to wind-driven rain are impacting rainfall volume, drop impact velocity (as determined by wind conditions), raindrop size and duration of rainfall. A vertical rain gauge was calibrated with climatic conditions at a test site in Sydney to enable accurate prediction of the volume of water impacting test specimens. In the laboratory, a standard spray test was modified by introducing a commercially available nozzle, which produces a turbulent spray of individual drops, rather than a stream of water. Erosion rates using this apparatus were found to vary significantly with time, and a correction formula was derived from experimental results to enable comparison to be made between field and laboratory results. Erosion rates per unit volume of water were found to be proportional to impacting velocity raised to the power 2.5 and inversely proportional to the median drop diameter raised to the power 1.2. A material factor was defined as the 60 minute erosion mass loss divided by the 60 minute volume of impacting water spray. Field tests were carried out over a period of four years and analysed in relation to the associated laboratory test results. Laboratory testing was carried out on one half of split specimens, the other half being subjected to exposure to the weather at Sydney's International Airport, with regular monitoring of wind and rain records. An empirical model was developed and was used to compare field and laboratory results. This confirmed the importance of impacting volume of water and material factor but in this case the calculated correlation between field and laboratory erosions was not improved by the addition of impact velocity and drop size terms.

M.S. / Biochemistry / The white-rot basidiomycete Phanerochaete chrysosporium produces intracellular soluble and particulate ß-glucosidases and an extracellular ß-glucosidase. The extracellular enzyme is induced by cellulose but repressed in the presence of glucose. The molecular weight of this enzyme is 90,000. The K [subscript m] for -p-nitrophenyl-ß-glucoside is 1.6 x 10[superscript -4] M; the K [subscript 1] for glucose, a competitive inhibitor, is 5.0 x 10[superscript -4] M. The K [subscript m] for cellobiose is 5.3 x 10[superscript -4] M. The intracellular soluble enzyme is induced by cellobiose; this induction is prevented by cycloheximide. The presence of 300 mM glucose in the medium, however, had no effect on induction. The K [subscript m] for p-nitrophenyl- ß -glucoside is 1.1 x 10[superscript -4] M. The molecular weight of this enzyme is about 410,000. Both enzymes have an optimal temperature of 60°C and an E [subscript act] of 9.15 kcal/mole. The pH optima, however, were 7.0 and 5.5 for the intracellular and extracellular enzymes, respectively.

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Ending a relationship is a common and often difficult experience for adolescents and young adults who are dating (Furman & Wehner, 1997). Yet, little is known about how romantic relationships deteriorate prior to breakup (Carver, Joyner, & Udry, 2003; Duck, 1981). The main goal of this study is to develop a definition of relationship deterioration that delineates the process of deterioration, by specifying a beginning and end point of deterioration and identifying characteristics that distinguish deterioration from breakup. Data for this study comes from the University of Texas Tracing Relationships and Commitment study (UT-TRAC), which contains 464 participants (232 heterosexual couples) who graphed changes in commitment over a 9-month period providing reasons describing each change. Deterioration, as defined as declines in commitment, was described by both partners in a romantic dyad in 90 couples whereas 75 individuals described deterioration and their romantic partner did not. A coding manual was created and pilot-tested to measure frequency and intensity of the four characteristics of deterioration in participant’s descriptions of changes in commitment. The current investigation used multi-level modeling separately for couples experiencing deterioration (to control for the dyadic nature of the data) and individuals whose partner did not report declines in commitment. Survival analyses using logistic regressions (Singer & Willett, 2003) were applied to measure how the characteristics of deterioration could predict breakup. Results of the analyses revealed that participants who experienced a breakup were more likely to report relationship deterioration, particularly for couples where both individuals described deterioration. Hierarchical linear models revealed that more frequent amounts of the deterioration characteristics was associated with deterioration as compared to pre-deterioration. However, intensity of the characteristics was not significant in differentiating between deterioration and pre-deterioration. In comparing deterioration with breakup, frequency of the deterioration characteristics predicted breakup only in descriptions of alternative partners, whereas intensity of the all four deterioration characteristics predicted breakup ranging from 37% (more intense scores of relational uncertainty) to 74% (more intense scores of alternative partners for an individual’s partner). Implications of this study will be in terms of commitment theory in order to further understand relationship processes. / text

The creep and shrinkage of concrete and the relaxation of cables cause long-term redistribution of internal forces and time-dependent deformations in concrete structures, steel-concrete composite structures and concrete cable-stayed bridges. They should be properly modelled for accurate prediction of their long-term behaviour and its effect on instantaneous structural responses at service. An equivalent stress relaxation model is proposed for prestressing tendons based on the intrinsic stress relaxation, from which the equivalent creep coefficients can be obtained through a recursive algorithm. Based on the equivalent stress relaxation model, an accurate finite element analysis of time-dependent behaviour by time integration has been devised considering concrete creep, concrete shrinkage and cable relaxation. Concrete members are modelled by beam-column elements while tendons are modelled by truss elements with nodes connected to the beam axis by perpendicular rigid arms. It is found that the proposed relaxation model with time integration can provide a reliable method as well as benchmark solutions for time-dependent analysis. The numerical results obtained indicate that the interactions among these factors should be properly considered in analysing the long-term performance of concrete bridges. Although time integration provides a reliable method for time-dependent analysis, both the computing time and memory requirement increase drastically with the number of time steps as the time-dependent strains of concrete and tendons within a time interval depend on the loading history up to that time. It is therefore necessary to develop a more efficient method to conduct time-dependent analysis. The relaxation-adjusted elasticity modulus is introduced on the basis of equivalent creep coefficients of tendons. Then, an efficient tendon sub-element is put forward to cope with cables with arbitrary profiles. Finally, a more general single-step method is devised using the classical age-adjusted elasticity modulus to account for external loading and creep effect, the shrinkage-adjusted elasticity modulus to consider shrinkage effect and its interaction with concrete creep, and the relaxation-adjusted elasticity modulus to consider the effect of cable relaxation based on the finite element method. The numerical results obtained indicate not only the accuracy of the single-step method but also the significance of interaction among various time-varying factors. Based on the time integration or single-step method, a systematic method is developed to monitor the long-term variations of dynamic properties of cable-stayed bridges taking into account various time-varying factors and geometric nonlinearities. Numerical studies show that, although geometric nonlinearities tend to reduce the natural frequencies, the time-dependent behaviour of concrete more than offsets it and tends to increase the natural frequencies in the long run. A generic method is further presented to investigate the long-term dynamic response of vehicle-bridge interaction systems taking account of time-dependent behaviour. The vehicles are represented by a combination of mass-spring-damper systems while the bridge is modelled by finite elements. The surface roughness of bridge deck is simulated by spectral representation method and introduced to the coupled system properly. Based on the method, the individual and combined effects of various time-varying factors are studied in detail using various numerical examples. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

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External sulfate attack is a complex process that can result in concrete structures deteriorating prematurely. This dissertation describes a comprehensive evaluation of factors influencing external sulfate attack and includes both laboratory and field investigations. Significant emphasis was placed on evaluating the sulfate resistance of mortar and concrete containing high-calcium fly ash (Class C fly ash as per ASTM C 618). This investigation showed that these fly ashes generally reduced the sulfate resistance of mortar and concrete, but that sulfate resistance was possible through the incorporation of other supplementary cementing materials (silica fume and ultra fine fly ash) into these mixtures. Another key area of emphasis in this project was the correlation between accelerated laboratory tests and outdoor exposure site performance. The behavior of concrete exposed to various sulfate salts (sodium, magnesium, and calcium) was evaluated, both in static immersion tests and in outdoor sulfate trenches. It was found that the distress outdoors was exacerbated by physical sulfate attack, especially when concrete was exposed to sodium sulfate. It was found that lowering the water-tocementitious ratio (w/cm) and incorporating appropriate dosages of suitable supplementary cementing materials improved resistance to both chemical and physical forms of sulfate attack. Lastly, a comprehensive study of bridges throughout Texas discovered concrete structures suffering from possible external sulfate attack. The use of analytical techniques such as x-ray diffraction (XRD) and scanning electron microscopy (SEM) were used throughout the study to determine the presence of hydration products that may form with mortars and concrete specimens. Findings from this research will be implemented in specifications in Texas for the use of Class C fly ash use in concrete in areas that may have sulfate soils and groundwater.

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