This thesis examines what makes a building valuable enough to keep regardless of what happens within it or where it is. A generic vacant lot in Dartmouth, N.S., ensures that these qualities are derived primarily from the architecture rather than its site. By housing three very different building programs, an auto body shop, small school and church, the design is challenged to become resilient to significant change. The thesis draws on ideas of building permanency - polyvalencey and frame theory (Leupen), as well as adaptability - building layers and strategic over-dimensioning (Brand). Valuable permanency is achieved by creating a building that is both full of purpose and purposeless at the same time. Furposefully, it is achieved through the use and correct arrangement of common forms, spatial sizes, a diversity of spatial types, as well as a high degree of self-maintenance of climate and construction. The purposeless qualities of proportion, craft and light help give the building its enduring character.

The process of designing cementitious layers (weakly and strongly cemented) against fatigue distress in road structures is well accepted. Research and field investigations with the aid of the Heavy Vehicle Simulator (HVS) revealed, however, that almost all weakly cemented subbase layers undergo non-traffic and traffic¬associated cracking and eventually degradation of the cemented material into a granular state (post-cracked phase). It is therefore very important to analyse these layers in the post-cracked phase and to incorporate the results of this analysis in the design, for both new and rehabilitation designs. The investigations revealed that the rate of degradation of these materials is largely dependent on traffic loading and the moisture conditions within the pavement layers. The purpose of this study is to investigate the behaviour of weakly cemented subbase layers in road structures mainly under a bitumen base between 90 mm and 140 mm thick. This behaviour includes both pre-cracked and post-cracked phases. It is shown that the fatigue life of bitumen base layers is mainly governed by the condition of the weakly cemented subbase layers. In Chapter 1 a brief historical review is given of the development of fatigue distress criteria of the cementitious layers. It is shown that the maximum horizontal tensile strain at the bottom of these layers is the main distress criterion in the pre-cracked phase. Unconfined compressive strength and durability requirements are also discussed. Some aspects of the current design methods are outlined in Chapter 2. The concept of equivalent granular states in the post-¬cracked phase of cementitious layers was derived from HVS test findings. However, before this document no behavioural prediction models were available to quantify accurately the post-cracked state of these layers. The actual mechanisms of distress were also not clear. In Chapter 3, a detailed investigations and analysis of ten dif¬ferent HVS tests at four different sites in Natal are discussed. The purpose of the analysis, is firstly to illustrate the powerful method of full-scale accelerated HVS-type testing and secondly to indicate the importance of the upper subbase layer, the initial condition of the in-situ structure, the importance of water condi¬tions within the pavement structure, and finally the different states of behaviour of this type of road structure, including predictions of future behaviour based on linear elastic theory. The characteristics of the weakly cemented upper subbase layer are shown to be of paramount importance in the final behaviour of these structures. In Chapter 4 a method of analysing the behaviour of mainly weakly cemented layers in the post-cracked phase is proposed. This method arises from the HVS testing discussed in Chapter 3, and may be regarded as the most important improvement on the current method discussed in Chapter 2. The analysis incorporates the determination of the effective elastic moduli of weakly cemented subbase layers, including both the wet and the dry periods during the structural design period of these layers. In Chapter 5 the effect of relatively weak interlayers within asphalt base structures is discussed and evaluated. The analysis incorporates the relative position and thickness of the inter layer during both wet (low modulus) and dry (high modulus) conditions. A summary and detailed discussion, together with recommendations for future research, are given in Chapter 6. The need for the incorpo¬ration of durability (erodibility) criteria for weakly cemented materials is also discussed. More research should be done on the effects of accelerated curing compared with normal curing methods. This investigation includes aspects of soil-lime-cement reactions together with delayed compaction techniques to reduce shrinkage cracking. The need for better quality control as well as improved construction techniques for weakly cemented materials is also discussed. This thesis also contains two appendices. In the first of these detailed photographic records of the different HVS tests and performances are given. In the second appendix an example of an input computer program to plot the three dimensional behavioural model is given. / Dissertation (MEng)--University of Pretoria, 2009. / Civil Engineering / unrestricted

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Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 68-69).

Internal waves are ubiquitous features in coastal marine environments and have been observed to mediate vertical distributions of zooplankton in situ. Internal waves create fine-scale hydrodynamic cues that copepods and other zooplankton are known to sense, such as fluid density gradients and velocity gradients (quantified as shear deformation rate). The role of copepod behavior in response to cues associated with internal waves is largely unknown. The objective is to provide insight to the bio-physical interaction and the role of biological versus physical forcing in mediating organism distributions. We constructed a laboratory-scale internal wave apparatus to facilitate fine-scale observations of copepod behavior in flows that replicate in situ conditions of internal waves in a two-layer stratification. Three cases were chosen with density jump of 0.75, 1.0, and 1.5 sigma-t units. Analytical analysis of the two-layer system provided guidance to the target forcing frequency needed to generate a standing internal wave with a single dominate frequency of oscillation. Flow visualization and signal processing of the interface location were used to quantify the wave characteristics. The results show a close match to the target wave parameters. Marine copepod (mixed population of Acartia tonsa, Temora longicornis, and Eurytemora affinis) behavior assays were conducted for three different physical arrangements: (1) no density stratification, (2) stagnant two-layer density stratification, and (3) two-layer density stratification with internal wave motion. Digitized trajectories of copepod swimming behavior indicate that in the control (case 1) the animals showed no preferential motion in terms of direction. In the stagnant density jump treatment (case 2) copepods preferentially moved horizontally, parallel to the density interface. In the internal wave treatment (case 3) copepods demonstrated orbital trajectories near the density interface. Further analysis showed that the copepods swim closer to the interface in the presence of internal waves.

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Much work is presently being done concerning small scale heterogeneities in the earth's crust. These heterogeneities range from pores in sedimentary rocks up to fluctuations in the density and seismic constants of the earth's crust with scale lengths of kilometers. The ability to study and quantify these heterogeneities using seismic methods would be a major advance in the earth sciences. Physical modeling has been shown to be a useful technique for investigating various aspects of wave propagation. In this thesis, two physical modeling experiments (one three-dimensional and one two-dimensional) are used to investigate the scattering of seismic waves from small scale heterogeneities and the changes in seismic velocity and apparent attenuation resulting from this scattering. The effects of both isotropic and anisotropic scattering on velocity and apparent attenuation are calculated. These experimental results are compared to theoretical results. The theory used for isotropic scattering for the three-dimensional experiment is a modified version of Wu's single scattering theory, where instead of calculating the scattering for a single scatterer using the Born approximation, the exact results for scattering from a cylindrical shape are used. While the results for compressional waves and both components of shear waves compare reasonably well for small scatterer volume fractions, at larger scatterer volume fractions, where the need for multiple scattering is more likely, the results for all waves do not compare as well. Many theories used to test anisotropic scattering predict changes in velocity rather than changes in apparent attenuation. The velocity changes are used primarily in this work due to geometrical focusing by a seismic lens that biases the amplitudes (and hence the estimates of apparent attenuation) at low frequencies where most theories predict apparent attenuation. Velocities are calculated from the data using travel times and low frequency phase shifts for the compressional waves and for one component of the shear waves measured in this two-dimensional experiment. Theories that are used to predict compressional and shear wave velocities for both isotropic and anisotropic scatterers are based on a fractional volume method (isotropic), two crack methods (isotropic and anisotropic), and a finely layered method (anisotropic). The isotropic experimental results have much larger, non-linear changes in the velocities than do the isotropic theoretical results. The anisotropic experimental results have similar shapes to both theoretical anisotropic methods for compressional waves and to the theoretical anisotropic crack method for shear waves. Attenuation is computed using log spectral ratios and compares as well with the theoretical results as can be expected within the limits set. A method using anisotropic apparent attenuation to help quantify the scatterers is developed for use with field data. / Graduation date: 1987