The experimental study reported upon in this thesis focused on the development of physical data characterizing the behavior of single-shear, laterally-loaded connections when loaded up to and beyond capacity (i.e., maximum resistance). Specimens included a wide array of connection configurations common in wood construction. All connections were tested monotonically in tension under displacement-controlled loading, parallel to the grain. Results of these tests are presented and discussed. Test variables of nailed connections included nail diameter, side member material type, and side member thickness. Test variables of bolted connections included bolt diameter, commercial species grouping of the main and side members, and main member thickness. Conclusions drawn from this research include mechanics-based explanations of numerous connection response trends observed with respect to test variables. Additionally, observed factors of safety and over-strengths of current design values are quantified on a capacity-basis. / Master of Science

Laboratory tests were performed to investigate the liquefaction susceptibility of uncemented calcareous sands. A series of isotropically consolidated undrained monotonic and cyclic triaxial tests were performed using the Playa Santa sand from Porto Rico. Playa Santa sand is a poorly graded calcareous clean beach sand composed of angular particles with large intra-granular voids. A series of consolidated undrained triaxial tests were performed with the Playa Santa sand remolded to a variety of relative densities and consolidated under a range of confining pressures. In addition, cyclic triaxial tests were performed at a confining pressure of 100 kPa and three sets of relative densities (20%, 40% and 60%). Generation of excess pore pressure under different levels of cyclic loading was established. As a result, relationships were developed to relate the number of cycles required for triggering of liquefaction to cyclic stress ratio. It was seen that the Playa Santa sand was less susceptible liquefaction than quartzitic sands of the same relative density remolded and tested under similar conditions. / Master of Science

This thesis will present the experimental and numerical analysis of composite sandwich structures under monotonic and fatigue loading. The sandwich skins were made of fiberglass and the core used was a closed cell PVC foam. Initial delaminations were introduced into the sandwich structures during manufacturing to see the effect of delamination size on the ultimate strength and monotonic fracture. Fiberglass rods, called shear keys, added to the foam core to determine whether or not they increased the strength of the test specimens. Furthermore, shear key locations were also varied and their effects noted. The fixed rate static behavior for all of the above cases listed were determined. The fatigue life and behavior were determined for sandwich structures with no initial delamination, 0.5 inch initial delamination, and 0.5 inch initial delamination with a shear key 0 inch from the delamination depth. The fatigue specimens were tested at various percentages of the ultimate monotonic failure loads to determine the fatigue life. A static numerical analysis was performed using Abaqus/CAE 6.7.1 to observe at the monotonic behavior of the test specimens with no initial delamination and with 0.5 inch initial delamination. The sandwich structures with an initial delamination and/or a shear key in the foam core experienced over a 70% reduction in the ultimate monotonic failure load. The two delamination lengths had no significant effect on the ultimate monotonic failure load, but the presence of an initial delamination corresponded to a material response dominated by plastic behavior. The experimental testing also showed that the location of the shear key in the sandwich structure had little effect on the monotonic strength, but moving the shear keys further away from the back edge of the delamination caused a reduction in strength. The monotonic testing determined that composite sandwich structures containing shear keys had approximately a 7% reduction in the monotonic failure load of test specimens with an initial delamination. Numerical analysis results matched the ultimate failure loads within 5% for the test specimens with a 0.5 inch an initial delamination and within 15% for the test specimens with no initial delamination. The fatigue testing showed that sandwich structures containing shear keys had life reduction of approximately 33%. Preliminary experiments involved with rotating the shear keys 90° showed increased ultimate monotonic failure loads of the composite sandwich structures by as much as 30%. Future funding and research would be necessary to verify the increased structural performance of the newly oriented shear keys.

Rapid delivery of backfill to support underground openings attracted many mines to adopt paste backfilling methods. As a precaution to prevent liquefaction and to improve the mechanical performance of backfills, a small portion of a binder is added to the paste to form the cemented paste backfill (CPB). Recently, adding sand to mine tailings (MT) in CPB mixes has attracted attention since it enhances the flow and mechanical characteristics of the pastefill. This thesis investigates the effects of adding sand to CPB on the undrained mechanical behavior of the mixture (CPBS) under monotonic and cyclic loads. Liquefaction investigations took place at the earliest practically possible age. Beyond this age, the present research focused on characterizing the evolution of stiffness and obtaining the values of the stiffness parameters that could be useful for designing and modeling backfilling systems. The liquefaction investigation involved monotonic compression and extension triaxial tests. Neither flow nor temporary liquefaction was observed for all cemented and uncemented specimens under monotonic compression, while temporary liquefaction was observed for all specimens under monotonic extension. The addition of binder and sand to MT was found to slightly strengthen the pastefill in compression while weakening it in extension. Under cyclic loading, the addition of sand negatively impacted the cyclic resistance. However, binder was found to be more effective in the presence of sand. All specimens exhibited a cyclic mobility type of response. The evolution of effective stiffness parameters for two CPB-sand mixtures was monitored in a non-destructive triaxial test for five days. Self-desiccation was found to not be influential on the development of early age stiffness. Moreover, a framework is suggested to predict the undrained stiffness at degrees of saturation representative of the field. The credibility of the proposed test in providing stiffness parameters at representative strain levels of the field was verified.

Rapid delivery of backfill to support underground openings attracted many mines to adopt paste backfilling methods. As a precaution to prevent liquefaction and to improve the mechanical performance of backfills, a small portion of a binder is added to the paste to form the cemented paste backfill (CPB). Recently, adding sand to mine tailings (MT) in CPB mixes has attracted attention since it enhances the flow and mechanical characteristics of the pastefill. This thesis investigates the effects of adding sand to CPB on the undrained mechanical behavior of the mixture (CPBS) under monotonic and cyclic loads. Liquefaction investigations took place at the earliest practically possible age. Beyond this age, the present research focused on characterizing the evolution of stiffness and obtaining the values of the stiffness parameters that could be useful for designing and modeling backfilling systems. The liquefaction investigation involved monotonic compression and extension triaxial tests. Neither flow nor temporary liquefaction was observed for all cemented and uncemented specimens under monotonic compression, while temporary liquefaction was observed for all specimens under monotonic extension. The addition of binder and sand to MT was found to slightly strengthen the pastefill in compression while weakening it in extension. Under cyclic loading, the addition of sand negatively impacted the cyclic resistance. However, binder was found to be more effective in the presence of sand. All specimens exhibited a cyclic mobility type of response. The evolution of effective stiffness parameters for two CPB-sand mixtures was monitored in a non-destructive triaxial test for five days. Self-desiccation was found to not be influential on the development of early age stiffness. Moreover, a framework is suggested to predict the undrained stiffness at degrees of saturation representative of the field. The credibility of the proposed test in providing stiffness parameters at representative strain levels of the field was verified.

A multi-agent system consists of a collection of agents that interact with each other to fulfil their tasks. Individual agents can have different motivations for engaging in interactions. Also, agents can possibly recognise the goals of the other participants in the interaction. To successfully interact, an agent should exhibit the ability to balance reactivity, pro-activeness (autonomy) and sociability. That is, individual agents should deliberate not only on what they themselves know about the working environment and their desires, but also on what they know about the beliefs and desires of the other agents in their group. Multi-agent systems have proven to be a useful tool for modelling and solving problems that exhibit complex and distributed structures. Examples include real-time traffic control and monitoring, work-flow management and information retrieval in computer networks. There are two broad challenges that the agent community is currently investigating. One is the development of the formalisms for representing the knowledge the agents have about their actions, goals, plans for achieving their goals and other agents. The second challenge is the development of the reasoning mechanisms agents use to achieve autonomy during the course of their interactions. Our research interests lie in a model for the interactions among the agents, whereby the behaviour of the individual agents can be specified in a declarative manner and these specifications can be made executable. Therefore, we investigate the methods that effectively represent the agents' knowledge about their working environment (which includes other agents), to derive unrealised information from the agents' knowledge by considering that the agents can obtain only a partial image of their working environment. The research also deals with the logical reasoning about the knowledge of the other agents to achieve a better interaction. Our approach is to apply the notions of modality and non-monotonic reasoning to formalise and to confront the problem of incomplete and conflicting information when modelling multi-agent systems. The approach maintains the richness in the description of the logical method while providing an efficient and easy-to-implement reasoning mechanism. In addition to the theoretical analysis, we investigate n-person argumentation as an application that benefits from the efficiency of our approach.

Thesis (Ph. D.)--State University of New York at Buffalo, 2002. / Includes bibliographical references (p. 167-186). Also available in print.

Thesis (M.S.)--University of Nevada, Reno, 2008. / "May, 2008." Includes bibliographical references (leaves 63-64). Online version available on the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 116-120).

Master of Science / Department of Civil Engineering / Asadollah Esmaeily / The accuracy and applicability of the existing stress-strain models for concrete confined by Carbon Fiber Reinforced Polymer (CFRP) were analytically and experimentally explored. This investigation includes major parameters affecting the stress-strain response of confined concrete, including the loading pattern and protocol. It has been observed and reported that the experimentally recorded stress-strain relationship of the same specimen will be different if the loading protocol of the test is switched from displacement control to load control. In the experimental phase of this study, four standard 6" by 12" concrete cylinders were constructed using the same concrete batch for consistency. Three two-inch strain gauges were affixed equally spaced at mid-height on the surface of the specimen in the longitudinal direction, and two two-inch strain gauges were applied in the lateral direction at mid-height opposite each other. CFRP was then impregnated with a two-part epoxy and applied externally in two continuous layers, with an overlap. During the first phase of the experimental program, the tests were conducted with a constant load rate or with a constant displacement rate. The data was collected from externally mounted strain gauges and potentiometers positioned on the opposite sides of the cylinder in the longitudinal direction. Since the capacity of the existing actuator in the structural lab was less than the required failure level of the specimens, a nutcracker-like device was constructed to increase the mechanical advantage of the test frame in the second phase of the experimental program. In this phase, all tests were conducted in displacement control. Various models were selected to be studied from a large number of existing models that propose to determine the stress-strain relationship of concrete. Analytical predictions of the models were compared against the experimental data. Results show that some of the models provide a reasonable prediction of the real performance of the specimen. However, in general, predictions are different from the real performance for most models.