The first section of this thesis (Chapter 2) describes the creation and analysis of a database on concrete and masonry dam incidents known as CONGDATA. The aim was to carry out as complete a study of concrete and masonry dam incidents as was practicable, with a greater emphasis than in other studies on the geology, mode of failure, and the warning signs that were observed. This analysis was used to develop a method of very approximately assessing probabilities of failure. This can be used in initial risk assessments of large concrete and masonry dams along with analysis of stability for various annual exceedance probability floods. The second and main section of this thesis (Chapters 3-6) had its origins in the results of Chapter 2 and the general interests of the author. It was found that failure through the foundation was common in the list of dams analysed and that information on how to assess the strength of the foundations of dams on rock masses was limited. This section applies to all applications of rock mass strength such as the stability of rock slopes. Methods used for assessing the shear strength of jointed rock masses are based on empirical criteria. As a general rule such criteria are based on laboratory scale specimens with very little, and often no, field validation. The Hoek-Brown empirical rock mass failure criterion was developed in 1980 for hard rock masses. Since its development it has become virtually universally accepted and is now used for all types of rock masses and in all stress regimes. This thesis uses case studies and databases of intact rock and rockfill triaxial tests collated by the author to review the current Hoek-Brown criterion. The results highlight the inability of the criterion to fit all types of intact rock and poor quality rock masses. This arose predominately due to the exponent a being restrained to approximately 0.5 to 0.62 and using rock type as a predictor of mi. Modifications to the equations for determining the Hoek-Brown parameters are provided that overcome these problems. In the course of reviewing the Hoek-Brown criterion new equations were derived for estimating the shear strength of intact rock and rockfill. Empirical slope design curves have also been developed for use as a preliminary tool for slope design.

Solid-liquid separation is an important unit operation in many industrial processes. Research on the process optimisation and technical advancement of this operation is crucial to ensure a reliable and economical process. Work include developments in filtration theory and understanding of suspension behaviour are constantly investigated to ensure the process reaches the target. / In this work, enhancement in dewatering was quantified with the use of shear. Shear, in this context, is a mechanism used to deform a suspension network such as the action of raking in thickeners. In order to understand the inter-play between shear and dewatering for colloidal networked suspension, the relationship between shear and compression rheology was investigated. / The effect of shear was investigated in two situations, which are the presence of shear during and before dewatering. The former was achieved by applying an electric field to a suspension during (in-situ to) dewatering and the latter was achieved through varying shear condition for flocculated suspensions prior to dewatering. The analysis of dewatering properties was then performed by applying the consolidation theory of Landman and White (Landman et al. 1995; Landman and White 1997). / The materials used in the study were two types of colloidal metal oxide particles namely AKP-30 alumina and Ajax kaolin. They were chosen due to their physical differences such as particle size and shape. The dispersion state of these suspensions from coagulated to dispersed, was fully controlled by manipulation of the particle surface chemistry. This changed the suspension micro-structure. Flocculated suspensions were prepared by the addition of a non-ionic, high molecular weight polyacrylamide to the coagulated AKP-30 alumina suspension. / The study on shear rheology was investigated by employing steady shear and small amplitude oscillatory shear (SAOS) measurements. The use of these two methods allowed quantitative interpretation of a network deformation of a suspension which involved the transition between solid-like behaviour (before yielding) and liquid-like behaviour (after yielding). The network deformation can be characterised as either being of a brittle or ductile type. The use of Lissajous figures also aided the understanding of the deformation. / The shear rheology of the metal oxide suspensions was found to depend critically on the extent of the inter-particle interactions. Both dispersed and coagulated suspensions show different rheological properties. In the case for coagulated suspensions, rheological parameters such as the shear and compressive yield stresses, and elastic modulus plateau value, all scaled, which indicate that these parameters arise from particle interaction. This is in contrast to the understanding of shear rheology on freshly flocculated suspension which is still limited, particularly for concentrations at close the gel point. The shear rheology of flocculated suspension was then compared to that of coagulated suspensions. Various degrees of flocculation conditions were investigated. Network deformation was found to show an identical pattern to that of coagulated suspensions but the network strength was found to increase with shear rate. / The dewatering properties of dispersed and coagulated AKP-30 alumina and Ajax kaolin suspensions were compared. It was found that dispersed suspensions have lower compressibility (i.e. produce a higher final solids concentration at the same applied pressure) and permeability compared to coagulated suspensions. Comparison between the two model suspensions shows that AKP-30 alumina suspensions have better dewatering qualities compared to kaolin suspensions. The effect of flocculation conditions for AKP-30 alumina suspension was found to dramatically affect the settling rate but had only a small effect on dewatering at higher solids. / A combination of dewatering methods was used and they gave excellent results for the prediction of the dewatering characteristics of suspensions for a wide range of solids concentration from close the gel point up to close to the maximum close packed concentration. Finally, electrically enhanced dewatering (EED) for Ajax kaolin suspension was compared to that of normal dewatering. Results showed significant dewaterability enhancement at pressures below 10 kPa. The application of EED was also investigated for an industrial sample of water treatment sludge. Similar results were noted as for Ajax kaolin, with an increase of equilibrium solids concentration and permeability with EED at a given pressure. In this context, EED delivered promising results in improving the dewatering properties of difficult-to-dewater suspensions.

Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on Dec. 15, 2007). Includes bibliographical references (p. 104-109).

An experimental investigation into the direct shear behaviour of steel fibre reinforced composites utilising discrete fibres at pre-defined angles and fibres randomly distributed is described. The direct shear tests encompassed the complete range of loading from its initial application to failure of the double L-shaped push-off specimens. Hooked-ended and straight steel fibres were used in the tests with the fibres oriented at angles of ??75??, ??60??, ??45??, ??30??, ??15?? and 0?? with respect to a plane normal to the loading direction. The embedment lengths of the fibres, related to the total fibre length lf , each side of the shear plane were 0.5lf :0.5lf and 0.25lf :0.75lf . In addition to the single fibre tests, tests were conducted on randomly oriented steel fibre reinforced composites with fibre volumes of 0.005, 0.010, 0.015, and 0.020 with hooked-ended and straight steel fibres. In addition to the tests outlined above, a series of non-destructive tests employing radiographic techniques was carried out to produce photographic images of events taking place of fibres pulling out from a cementitious element. The tests consisted of hooked-ended steel fibres oriented at angles of -60??, -30??, 0??, +30?? and +60?? to the cracking plane and straight fibres oriented at angles of -60??, 0?? and +60??. The non destructive technique allowed the internal behaviour occurring within the specimen along the shear plane to be investigated without impacting on the direct shear tests. The angle of the fibre to the interface plane is an important parameter in determining the behaviour of the fibres under load and for the mode of failure; viz fibre pullout or fibre fracture. The effect of the end hook on behavioural aspects becomes increasingly less significant for more acute fibre angles where bending and snubbing effects become increasingly influential on the load versus displacement behaviour and mode of failure. Contrary to expectations, the fibre embedment length had little influence over the peak loads attained for the discrete fibre tests and, in a number of specimens, fibres pulled out from the longer embedded side. This observation is contrary to the generally accepted assumption that a fibre remains rigidly embedded on the long side and pulls out from short side. The traditional role that uniform bond stresses along a fibre length and friction have played in the description of fibre behaviour is not as significant as previously reported, other effects such as snubbing are more important in anchoring a fibre. Various models need to be revised with this observation in mind. The experimental results and observations from the discrete hooked-ended and straight steel fibres investigation are incorporated in the development of a behavioural model, the Variable Engagement Model II (VEMII). The VEMII describes the behaviour of randomly oriented discontinuous steel fibre reinforced composites loaded in shear. The model is verified against a series of randomly distributed fibre reinforced mortar specimens carried out in this study. Two forms of models are analysed: 1) a model based on the observation of lumped shear stresses at the fibre hook and in the snubbing zone; and 2) a uniform fibre bond stress applied along the embedded part of the fibre. The lumped bond stress approach and the uniform approach were found to give reasonable comparisons with the test data for the hooked-ended fibres but were conservative for the straight fibres. The VEMII confirms the applicability of the uniform bond approach adopted by previous researchers even though it does not correspond to the observations of fibre pullout behaviour of single fibres. The VEMII model provides a versatile approach that can also be applied to hybrid fibre combinations.

An experimental investigation into the direct shear behaviour of steel fibre reinforced composites utilising discrete fibres at pre-defined angles and fibres randomly distributed is described. The direct shear tests encompassed the complete range of loading from its initial application to failure of the double L-shaped push-off specimens. Hooked-ended and straight steel fibres were used in the tests with the fibres oriented at angles of ??75??, ??60??, ??45??, ??30??, ??15?? and 0?? with respect to a plane normal to the loading direction. The embedment lengths of the fibres, related to the total fibre length lf , each side of the shear plane were 0.5lf :0.5lf and 0.25lf :0.75lf . In addition to the single fibre tests, tests were conducted on randomly oriented steel fibre reinforced composites with fibre volumes of 0.005, 0.010, 0.015, and 0.020 with hooked-ended and straight steel fibres. In addition to the tests outlined above, a series of non-destructive tests employing radiographic techniques was carried out to produce photographic images of events taking place of fibres pulling out from a cementitious element. The tests consisted of hooked-ended steel fibres oriented at angles of -60??, -30??, 0??, +30?? and +60?? to the cracking plane and straight fibres oriented at angles of -60??, 0?? and +60??. The non destructive technique allowed the internal behaviour occurring within the specimen along the shear plane to be investigated without impacting on the direct shear tests. The angle of the fibre to the interface plane is an important parameter in determining the behaviour of the fibres under load and for the mode of failure; viz fibre pullout or fibre fracture. The effect of the end hook on behavioural aspects becomes increasingly less significant for more acute fibre angles where bending and snubbing effects become increasingly influential on the load versus displacement behaviour and mode of failure. Contrary to expectations, the fibre embedment length had little influence over the peak loads attained for the discrete fibre tests and, in a number of specimens, fibres pulled out from the longer embedded side. This observation is contrary to the generally accepted assumption that a fibre remains rigidly embedded on the long side and pulls out from short side. The traditional role that uniform bond stresses along a fibre length and friction have played in the description of fibre behaviour is not as significant as previously reported, other effects such as snubbing are more important in anchoring a fibre. Various models need to be revised with this observation in mind. The experimental results and observations from the discrete hooked-ended and straight steel fibres investigation are incorporated in the development of a behavioural model, the Variable Engagement Model II (VEMII). The VEMII describes the behaviour of randomly oriented discontinuous steel fibre reinforced composites loaded in shear. The model is verified against a series of randomly distributed fibre reinforced mortar specimens carried out in this study. Two forms of models are analysed: 1) a model based on the observation of lumped shear stresses at the fibre hook and in the snubbing zone; and 2) a uniform fibre bond stress applied along the embedded part of the fibre. The lumped bond stress approach and the uniform approach were found to give reasonable comparisons with the test data for the hooked-ended fibres but were conservative for the straight fibres. The VEMII confirms the applicability of the uniform bond approach adopted by previous researchers even though it does not correspond to the observations of fibre pullout behaviour of single fibres. The VEMII model provides a versatile approach that can also be applied to hybrid fibre combinations.

The first section of this thesis (Chapter 2) describes the creation and analysis of a database on concrete and masonry dam incidents known as CONGDATA. The aim was to carry out as complete a study of concrete and masonry dam incidents as was practicable, with a greater emphasis than in other studies on the geology, mode of failure, and the warning signs that were observed. This analysis was used to develop a method of very approximately assessing probabilities of failure. This can be used in initial risk assessments of large concrete and masonry dams along with analysis of stability for various annual exceedance probability floods. The second and main section of this thesis (Chapters 3-6) had its origins in the results of Chapter 2 and the general interests of the author. It was found that failure through the foundation was common in the list of dams analysed and that information on how to assess the strength of the foundations of dams on rock masses was limited. This section applies to all applications of rock mass strength such as the stability of rock slopes. Methods used for assessing the shear strength of jointed rock masses are based on empirical criteria. As a general rule such criteria are based on laboratory scale specimens with very little, and often no, field validation. The Hoek-Brown empirical rock mass failure criterion was developed in 1980 for hard rock masses. Since its development it has become virtually universally accepted and is now used for all types of rock masses and in all stress regimes. This thesis uses case studies and databases of intact rock and rockfill triaxial tests collated by the author to review the current Hoek-Brown criterion. The results highlight the inability of the criterion to fit all types of intact rock and poor quality rock masses. This arose predominately due to the exponent a being restrained to approximately 0.5 to 0.62 and using rock type as a predictor of mi. Modifications to the equations for determining the Hoek-Brown parameters are provided that overcome these problems. In the course of reviewing the Hoek-Brown criterion new equations were derived for estimating the shear strength of intact rock and rockfill. Empirical slope design curves have also been developed for use as a preliminary tool for slope design.

The stability of steady-state solutions of the equations governing two-dimensional, homogeneous, incompressible fluid flow are analyzed in the context of shear-flow in a channel. Both the linear and nonlinear theories are reviewed and compared. In proving nonlinear stability of an equilibrium, emphasis is placed on using the stability algorithm developed in Holm et al. (1985). It is shown that for certain types of equilibria the linear theory is inconclusive, although nonlinear stability can be proven. Establishing nonlinear stability is dependent on the definition of a norm on the space of perturbations. McIntyre and Shepherd (1987) specifically define five norms, two for corresponding to one flow state and three to a different flow state, and suggest that still others are possible. Here, the norms given by McIntyre and Shepherd (1987) are shown to induce the same topology (for the corresponding flow states), establishing their equivalence as norms, and hence their equivalence as measures of stability. Summaries of the different types of stability and their mathematical definitions are presented. Additionally, a summary of conditions on shear-flow equilibria under which the various types of stability have been proven is presented. The Hamiltonian structure of the two-dimensional Euler equations is outlined following Olver (1986). A coordinate-free approach is adopted emphasizing the role of the Poisson bracket structure. Direct calculations are given to show that the Casimir invariants, or distinguished functionals, are time-independent and therefore are conserved quantities in the usual sense. / Graduation date: 1990

Thesis (M.S. in civil engineering)--Washington State University, May 2007. / Includes bibliographical references.

The MIDPLY shear wall has been developed to be used as a structural system for severe earthquakes. This type of construction has emerged as a viable alternative to concrete and steel for non-residential buildings. The MIDPLY shear wall utilizes a novel arrangement of sheathing and framing members with a special nailing technique. The MIDPLY joints have a different failure mode from that which is observed in standard shear walls. The study reported in this thesis focuses on the response of the MIDPLY shear wall due to monotonic and cyclic tests; the response of an increase size in the cross-section members of the MIDPLY shear wall; and also the evaluation of the design and performance of hold-down connections at the boundary end studs of the MIDPLY shear wall. Previously tested MIDPLY shear walls showed that the boundary end stud hold-down connection is a very critical component in the performance of the MIDPLY shear wall. After a simplified analysis of 2 possible hold-down connections (see Fig. 7, 8, 9 and 10), hold-down connection #2 was selected as the most viable option since it had the ability to withstand large lateral forces. For non-residential buildings we expect a larger lateral force when compared to residential buildings. Therefore the cross-section of the members in the MIDPLY shear wall was increased and the number of boundary end studs was modified. These measures resulted in an increase in the lateral force capacity with the use of hold-down connection #2. The experimental results were used to verify an analytical model representing the MIDPLY shear wall in load-displacement characteristics. Recommendations and future research will also be discussed to show the way for further performance optimization of the wall system.

No description available.