In many hydroelectric projects there is a need to safely dissipate the energy associated with the elevation of the water surface. When the flow is not passing through the turbines, bypass valves are often used. A valve that is commonly used is the fixed-cone valve. Fixed-cone valves, also known as Howell-Bunger valves, are devices often used to safely reduce flow energy at dams with medium to high heads. The valve directs the outflow into a conical hollow jet, which requires a large area for energy dissipation. The flow is controlled by an adjustable sleeve, also known as the gate which surrounds the valve and requires minimal power for operation even for large valves. Depending on the installation, the conical jet may need to be controlled by installing a fixed stationary hood or other structure to contain and direct the conical jet. While the hood reduces the spray, the use of the hood causes the formation of a concentrated hollow jet having a high velocity. To eliminate the hollow jet and dissipate much of the associated energy, the hood can have interior baffles. If the hood is not precisely placed relative to the valve, a phenomenon, known as backsplash, will occur. Backsplash is when a significant amount of water exits the upstream end of the hood. Backsplash is a concern for operators because it can prevent access to the valve during operation and can flood valve vaults. Because the use of fixed-cone valves and baffled-hoods are becoming more popular, the need for guidelines to correctly position the hood relative to the valve will benefit both engineers and contractors. In some hydroelectric sites, submerging the fixed-cone valve is used to control the spray and dissipate energy. Submerging the valve can have can produce violent flow conditions which can cause damage to a structure or heavy erosion. The use of a submerged fixed-cone valve is rarely used, and a submerged valve used with a baffled-hood has never been constructed. The study performed shows that the use of a baffled hood with a fixed-cone valve in submerged conditions performs well. The results may lead the way for more submerged fixed-cone valves in the future.

For life to arise from non-life, a metabolism must emerge and maintain itself, distinct from its environment. One line of research seeking to understand this emergence has focused on models of autocatalytic reaction networks (ARNs) and the conditions that allow them to approximate metabolic behavior. These models have identified reaction parameters from which a proto-metabolism might emerge given an adequate matter-energy flow through the system. This dissertation extends that research by answering the question: can dynamically structured interactions with the environment promote the emergence of ARNs? This question was inspired by theories that place the origin of life in contexts such as diurnal or tidal cycles. To answer it, an artificial chemistry system with ARN potential was implemented in the dissipative particle dynamics (DPD) modeling paradigm. Unlike differential equation (DE) models favored in prior ARN research, the DPD model is able to simulate environmental dynamics interacting with discrete particles, spatial heterogeneity, and rare events. This dissertation first presents a comparison of the DPD model to published DE results, showing qualitative similarity with some interesting differences. Multiple examples are then provided of dynamically changing flows from the environment that promote emergent ARNs more than constant flows. These include specific cycles of energy and mass flux that consistently increase metrics for ARN concentration and mass focusing. The results also demonstrate interesting nonlinear interactions between the system and cycle amplitude and period. These findings demonstrate the relevance that environmental dynamics has to ARN research and the potential for broader application as well.

This research examines the seismic energy dissipation potential of steel structures by focusing on new types of specially engineered cladding-to-frame connections. Traditional connection details consist of rigid restraints of cladding panels, resulting in seismic design that only considers the panel self-weight with connection design left up to the precast fabricators and typical details. It is postulated that by considering these elements to actively participate in building response a more efficient and resilient structure could be designed which accurately captures the effects of non-structural cladding elements on building behavior. In this preliminary research, two mechanisms to dissipate seismic energy using engineered cladding systems are presented. Analysis results on a reference steel building indicate that demands on structural elements may be significantly reduced.

Understanding the deformation mechanisms and the impact forces generated by landslides on structures is essential for risk assessment and improving the design of mitigation measures. This thesis studies the effect of different basal sliding characteristics of biplanar compound landslides on the post-failure mechanics and the interaction with rigid structures. The Material Point Method (MPM), an advanced numerical tool capable of simulating large deformations, captures the whole instability and the impact process. A simple geometry of a biplanar compound landslide is considered with two different types of biplanar slope transitions along the basal surface – sharp transition (or "kink" geometry) and curved transition (with different radii). A comprehensive parametric study with more than 280 simulations is performed to analyze the landslide post-failure behavior in terms of the radii of transition, the basal friction angle, the distance to the rigid wall, the roughness of the rigid wall, and the scale of the landslide. The results are presented in terms of maximum impact force on the rigid wall and final runout (in the absence of the wall). Results show that the basal characteristics impact the landslide kinetics and energy dissipations, which in turn, influence the impact forces on the rigid wall as well as the final runout of the landslide. The basal friction amplifies the influence of slope geometry on maximum impact forces. In addition, the maximum impact force from numerical results is compared with the predictions from existing semi-empirical approaches. Finally, a preliminary empirical framework is proposed to incorporate the effects of basal sliding characteristics of compound landslides into predicting impact forces on retaining walls. / Master of Science / Landslides and slope failures are a major problem in the geotechnical field that causes significant damage to lives and infrastructure worldwide. It, therefore, becomes essential to understand the mechanisms and the deformation patterns from the standpoint of assessing the impact on infrastructure near the landslide. This thesis studies the effects of the geometry of compound landslides on the maximum impact forces exerted on a rigid structure at a given distance from the landslide. It uses the Material Point Method (MPM), a numerical method that simulates problems involving large deformations. MPM allows the study of the entire instability process from failure initiation to final runout and impact against barriers. Several theoretical models of generic landslides of different radii of slope transition, friction on the sliding surface, and different distances from the wall are presented to study the effects of these parameters on the maximum impact force exerted on the wall. Along with this, the effects of the scale of a landslide on the impact forces are also analyzed. Based on the results, an empirical framework is proposed to help calculate maximum impact forces on a vertical rigid wall while incorporating the basal failure surface characteristics.

Light-framed wood structures generally have satisfied the life safety objective of the current seismic design approach. The main source of energy dissipation in such structures is the inelastic behavior of the connectors connecting framing and sheathing elements. Wood framed structures when subjected to strong ground excitations experience structural and non-structural damage which may incur large repair/replacement costs or may even render the structure out of service. Thus, it is very important to apply techniques to mitigate the seismic response of the light-framed structures and avoid large monetary losses. It is proposed to use commercially available permanent magnets, incorporated in the form of passive friction dampers, to dissipate a part of input energy induced due to strong ground motions, thereby reducing the inelastic energy dissipation demand of the lateral load resisting system. The force of attraction between the permanent magnet and ferromagnetic material like steel was utilized to produce the required friction resistance. A sliding wall configuration consisting of flexible permanent magnets and steel plates sandwiched between the plywood sheets was analyzed for its effectiveness in mitigating the response of a two story wood shear wall structure. The structural analysis program SAP2000 was used to perform nonlinear dynamic analysis of the finite element models generated using the meshing algorithms incorporated into 'WoodFrameMesh'. Nonlinear link elements available in SAP2000 were used to model the friction between the flexible magnet sheet and the steel plate. The effects of various modeling parameters on the solution of the nonlinear analysis were studied so as to arrive at appropriate values to represent the friction problem. Also the friction damped structure was analyzed to study its forced and free vibration characteristics. Further, the responses of the friction damped structure and the undamped structure were compared when subjected to different ground accelerations. The response of the friction damped structure was also compared to that of the structure in which the proposed friction dampers were replaced by normal shear walls. A huge reduction in the response of the friction damped structure was observed when compared to the response of the undamped structure. The friction damped structure was also analyzed for different values of modal damping ratios. Over all about 60-80% of the input energy was dissipated by friction damping in all the cases. The slip resistance of a flexible permanent magnet sheet was also verified in the laboratory. Above all the magnetic properties of commercially available permanent magnets and the effects of strong permanent magnets on human health were also studied. / Master of Science

No / This paper presents analytical technique and simplified formulas for the calculations of cracking, yield and ultimate moments of different cases as well as deflections of ECC-concrete composite beams reinforced with steel bars. The technique is based on the simplified constitutive models of materials, strain compatibility, perforce bond of materials and equilibrium of internal forces and moment. Experimental testing of eleven ECC-concrete composite beams reinforced with steel bars is also presented. All beams tested had the same geometrical dimensions but different steel reinforcement strength and ECC thickness. The proposed formulas showed good agreement with the experimental results of various moment values and deflections. A parametric analysis shows that yield and ultimate moments increase with the increase of concrete strength in case of compression failure but, essentially, remain unchanged in case of tensile failure. With increasing the tensile resistance, for example by increasing ECC height replacement ratio, reinforcement ratio, strength of steel reinforcement and ECC, ultimate curvature and energy dissipation increase in case of tensile failure and decrease in case of compressive failure. On the other hand, ductility and energy dissipation ratio decrease with the increase of reinforcement ratio and strength, but, essentially, remain unchanged with increasing the height replacement ratio and strength of ECC. / National Natural Science Foundation of China (51678514, 51308490), the Natural Science Foundation of Jiangsu Province, China (BK20130450), Six Talent Peaks Project of Jiangsu Province (JZ-038, 2016), Graduate Practice Innovation Project of Jiangsu Province (SJCX17-0625) and the Jiangsu Government Scholarship for Overseas Studies.

In this study a modern hydrocode, blastFoam, that was designed for multi-phase compressible flow problems with applications suited for high-explosive detonation was investigated for underwater explosion (UNDEX) events. The problem of over-prediction for long-term UNDEX bubble behavior in modern hydrocodes that is known to be due to neglected secondary energy-loss mechanisms is evaluated. A single secondary energy-loss mechanism is established as the most significant loss mechanism that is being disregarded in current hydrocodes. The leading secondary energy-loss mechanism is formulated into a computational model that modifies the Jones-Wilkins-Lee (JWL) equation of state (EOS). Explanation and guidance for implementing the model in an Finite Volume Method (FVM) Eulerian-based hydrocode is provided. Through this research this thesis aims to improve long-term UNDEX bubble behavior prediction. Which is apart of a larger effort to improve numerical and computational predictions of UNDEX-induced structural ship response. / M.S. / Predicting the bubble dynamics of an underwater explosion (UNDEX) event is of great importance for the survivability of America’s warships. Shock waves from high-energy explosives are destructive to anything and everything nearby. Therefore, the design and development of military machinery rely on the accurate predictions of computational simulations. Computational solvers must be able to simulate the initial propagating shock waves from an underwater explosion, as well as the smaller following shock waves from the oscillating UNDEX bubble. Current incompressible solvers neglect the important compressible effects needed to predict the behavior for the UNDEX bubble oscillation cycle. If America’s Navy cannot predict the long-term damaging effects that a warship may encounter from an UNDEX bubble, then America’s warships and crew could not survive at battle. This study considers the assumptions used to simplify current UNDEX computational solvers in order to investigate and organize a compressible long-term simulation model. This model improves the multi-pulse bubble dynamic predictions for an UNDEX event, and will in return help design a long-term battle-ready warship for America’s future warfare.

Structural fuses are ductile elements of a structure that are designed to yield and protect the surrounding members from damage, and then be replaceable after a major seismic event. A promising type of seismic structural fuse consists of a steel plate with engineered cutouts leaving a configuration of shear-acting links remaining. There have been several studies on various cutout patterns for shear-acting structural fuses including butterfly-shaped links, hourglass-shaped links, elliptical holes, and link shapes obtained from topology optimization. In most cases, the links are designed to undergo flexural yielding as it is believed to exhibit more ductility than other limit states. However, computational and experimental studies on the shear yielding limit state are limited. Additionally, the transition between shear dominated and flexural dominated limit states has not been previously investigated. Hence, a systematic and thorough study on the different limit states of these structural fuse shapes is necessary to provide better understanding on the structural behavior of each shape and accurately predict the controlling limit state during a seismic event. In addition, a previous study recognized that delaying shear buckling while promoting yielding is a way to improve the seismic performance of shear-acting structural fuses. However, the resulting new topologies were not experimentally validated. Furthermore, the computational study revealed that large localized plastic strain is one major challenge for these optimized configurations which might lead to potential for fracture. With the goals of filling the gaps in previous research, a computational and experimental program was conducted to (1) understand seismic performance of five structural fuse shapes, (2) develop a new ductile structural fuse shape with both buckling and fracture resistance, and (3) create design guidelines for practical design. This study consisted of the following parts (a) Creation of a new structural fuse shape called the Tied Butterfly Shape, (b) An experimental program with 20 specimens categorized into five groups including the shape created using topology optimization to resist buckling, the new shape called Tied Butterfly Shape, the butterfly shape, the hourglass shape and the elliptical holes, (c) Use of finite element models to better understand and interpret test data, (d) Two computational parametric studies conducted to investigate the effect of geometrical parameters on structural behavior of the optimized shape and Tied Butterfly Shape, (e) Development of design recommendations for each structural fuse shape. The computational and experimental results reported in this dissertation demonstrate that these structural fuse shapes are capable of improving the seismic performance of buildings. The presented design recommendations allow designers and researchers to continue exploring these structural fuse shapes. / Doctor of Philosophy / Structural fuses are ductile elements of a structure that are designed to yield and protect the surrounding members from damage, and then be replaceable after a major seismic event. Several studies on various cutout patterns for shear-acting structural fuses including butterfly-shaped links, hourglass-shaped links, elliptical holes, and link shapes obtained from topology optimization, reported that they offer several advantages for use in structural systems. Nevertheless, systematic studies on key limit states of these structural fuse shapes are limited. In addition, some analytical results have not been validated by experiments. The research work provides a comprehensive study on these structural fuse shapes. First, generalized design equations are derived using plastic mechanism analysis and key limit states of these structural fuse shapes are investigated. Second, an experimental program was conducted to further understand the cyclic behavior of these shapes associated with each limit state (i.e flexural yielding, shear yielding, lateral torsional buckling, transition between the flexural and shear yielding limit states). Then, nonlinear finite element modeling was implemented to validate against experimental results and provide better understanding of the behavior of the specimens which is not obvious during the test. Lastly, design recommendations are developed for each structural fuse shape.

Energy dissipation in systems with linear viscoelastic damping is examined. It is shown that in such viscoelastically damped systems the use of additional dissipation mechanisms (such as boundary velocity feedback or thermal coupling) may not improve the rate of energy decay. The situation where the viscoelastic stress relaxation modulus decreases to its (positive) equilibrium modulus at a subexponential rate, e.g., like (1 + t)^-x + E, where α > 0, E > 0 is examined. In this case, the nonoscillatory modes (the so-called creep modes) dominate the energy decay rate. The results are in two parts. In the first part, a linear viscoelastic wave equation with infinite memory is examined. It is shown that under appropriate conditions on the kernel and initial history, the total energy is integrable against a particular weight if the kinetic energy component of the total energy is integrable against the same weight. The proof uses energy methods in an induction argument. Precise energy decay rates have recently been obtained using boundary velocity feedback. It is shown that the same decay rates hold for history value problems with conservative boundary conditions provided that an <i>a priori</i> knowledge of the decay rate of the kinetic energy term is assumed. In the second part, a simple linear thermo-viscoelastic system, namely, a viscoelastic wave equation coupled to a heat equation, is examined. Using Laplace transform methods, an integral representation formula for <i>W(x,s</i>), the transform of the displacement <i>w(x, t)</i>, is obtained. After analyzing the location of the zeros of the appropriate characteristic equation, an asymptotic expansion for the displacement <i>w(O,t)</i> is obtained which is valid for large <i>t</i> and the specific kernel <i>g(t) = g</i>(–) + δtη-1 [over]Î (η), 0 < η < 1. With this expansion it is shown that the coupled system tends to its equilibrium at a slower rate than that of the uncoupled system. / Ph. D.

Discontinuous deformation analysis (DDA) is a newly developed simulation method for discontinuous systems. It was designed to simulate systems with arbitrary shaped blocks with high efficiency while providing accurate solutions for energy dissipation. But DDA usually exhibits damping effects that are inconsistent with theoretical solutions. The deep reason for these artificial damping effects has been an open question, and it is hypothesized that these damping effects could result from the time integration scheme. In this thesis two time integration methods are investigated: the forward Euler method and the Newmark method. The work begins by combining the Newmark method and the DDA. An integrated Newmark method is also developed, where velocity and acceleration do not need to be updated. In simulations, two of the most widely used models are adopted to test the forward Euler method and the Newmark method. The first one is a sliding model, in which both the forward Euler method and the Newmark method give accurate solutions compared with analytical results. The second model is an impacting model, in which the Newmark method has much better accuracy than the forward Euler method, and there are minimal damping effects. / Master of Science