The deterioration of the nation's civil infrastructure has prompted the investigation of numerous solutions to offset the problem. Some of these solutions have come in the form of innovative materials for new construction, whereas others have considered rehabilitation techniques for repairing existing infrastructure. A relatively new system that appears capable of encompassing both of these solution methodologies is the Sandwich Plate System (SPS), a composite bridge deck system that can be used in both new construction or for rehabilitation applications. SPS consists of steel face plates bonded to a rigid polyurethane core; a typical bridge application utilizes SPS primarily as a bridge deck acting compositely with conventional support girders. As a result of this technology being relatively new to the bridge market, design methods have yet to be established. This research aims to close this gap by investigating some of the key design issues considered to be limiting factors in implementation of SPS. The key issues that will be studied include lateral load distribution, dynamic load allowance and deck design methodologies. With SPS being new to the market, there has only been a single bridge application, limiting the investigations of in-service behavior. The Shenley Bridge was tested under live load conditions to determine in-service behavior with an emphasis on lateral load distribution and dynamic load allowance. Both static and dynamic testing were conducted. Results from the testing allowed for the determination of lateral load distribution factors and dynamic load allowance of an in-service SPS bridge. These results also provided a means to validate a finite element modeling approach which would could as the foundation for the remaining investigations on lateral load distribution and dynamic load allowance. The limited population of SPS bridges required the use of analytical methods of analysis for this study. These analytical models included finite element models and a stiffened plate model. The models were intended to be simple, but capable of predicting global response such as lateral load distribution and dynamic load allowance. The finite element models are shown to provide accurate predictions of the global response, but the stiffened plate approach was not as accurate. A parametric investigation, using the finite element models, was initiated to determine if the lateral load distribution characteristics and vibration response of SPS varied significantly from conventional systems. Results from this study suggest that the behavior of SPS does differ somewhat from conventional systems, but the response can be accommodated with current AASHTO LRFD bridge design provisions as a result of their conservativeness. In addition to characterizing global response, a deck design approach was developed. In this approach the SPS deck was represented as a plate structure, which allowed for the consideration of the key design limit states within the AASHTO LRFD specification. Based on the plate analyses, it was concluded that the design of SPS decks is stiffness-controlled as limited by the AASHTO LRFD specification deflection limits for lightweight metal decks. These limits allowed for the development of a method for sizing SPS decks to satisfy stiffness requirements. / Ph. D.

In the supply chain there are three components: transportation method, the pallet, and the packaging. Traditionally, there has been a poor understanding of the way that pallet design can impact the supply chain. There are historical studies that illustrate the importance of investigating how box stacking pattern, unit load type, unit load size, and containment can impact the pallet's performance. However, there have been no studies that have investigated the impact of drums and plastic pails on pallet performance. The goal of the current research study was to investigate how plastic pails and drums affect pallet bending and the distribution of the pressure on the top surface of the pallet. The investigation was conducted using four different support conditions commonly found in warehouses: racking across the width and length, single stacking, and double stacking. The results of the investigation indicated that for most support conditions, loading the pallet with plastic pails or drums results in a significant reduction in deflection when compared to a uniformly distributed load. The maximum observed reduction in pallet deflection was 85% when testing with drums in the double stack condition and 89% when testing with plastic pails in the single stack condition. The large reductions in deflection could indicate that the pallets were over-designed for the unit load that they were supporting. Pressure mat distribution images collected during the experiment display a load bridging effect where the stress of the drums and pails are redistributed to the supported sides of the pallet. The data also show that drums made of different materials distribute the pressure onto the pallet in a significantly different manner. / Master of Science / Wood pallets are crucial to the supply chain that delivers the goods and objects that sustain our economy. Every product order or product that is seen in stores was sent through the supply chain. The supply chain is made up of three major interacting components, the material handling system, the packaging, and the pallet. By further understanding the interaction between these components, pallet and packaging designers can better utilize materials and maximize the efficiency of the supply chain. There is a need to understand how different types of packages interact with the pallet to effectively design pallets and to potentially reduce costs and material usage. Historical studies focused on investigating how corrugated boxes affect pallet performance. They mainly focused on the effect of corrugated box size, flute type, stretch wrapping and containment, and the influences that pallet design have on pallet performance. Past studies identified that packages on the top of the pallet could create a bridging between the packages that can reduce the stresses on the pallet and consequently increase its load capacity. By using this load bridging effect for their advantage, pallet designers can design pallets that are safer, cheaper, and be more environmentally friendly since current wood pallets are designed under the assumption of a uniformly distributed, rather than bridged, load. The goal of the current study was to investigate how the load bridging effect created by pails and drum affects the deflection of the pallet in the floor stacked loading condition. The investigation was conducted using four different support conditions commonly found in warehouses such as racking across the length, racking across the width, single stacking, and double stacking. The results of the investigation indicated that for most investigated support conditions, the interaction between pails and drums causes an increase in load bridging which significantly reduces the bending of the pallet. The reductions reached a maximum of 85% when testing with drums in the double stack condition and 89% when testing with plastic pails in the single stack condition. The large reductions in deflection could indicate that the pallets were over-designed for the unit load that they were supporting.

In recent decades there has been a rapidly growing demand for high quality, uninterrupted power. In light of this fact, this study has addressed some of the causes of poor power quality and control strategies to ensure a high performance level in inverter-fed power systems. In particular, specific loading conditions present interesting challenges to inverter-fed, high power systems. No-load, unbalanced loading, and non-linear loading each have unique characteristics that negatively influence the performance of the Voltage Source Inverter (VSI). Ideal, infinitely stiff power systems are uninfluenced by loading conditions; however, realistic systems, with finite output impedances, encounter stability issues, unbalanced phase voltage, and harmonic distortion. Each of the loading conditions is presented in detail with a proposed control strategy in order to ensure superior inverter performance. Simulation results are presented for a 90 kVA, 400 Hz VSI under challenging loading conditions to demonstrate the merits of the proposed control strategies. Unloaded or lightly loaded conditions can cause instabilities in inverter-fed power systems, because of the lightly damped characteristic of the output filter. An inner current loop is demonstrated to damp the filter poles at light load and therefore enable an increase in the control bandwidth by an order of magnitude. Unbalanced loading causes unequal phase currents, and consequently negative sequence and zero sequence (in four-wire systems) distortion. A proposed control strategy based on synchronous and stationary frame controllers is shown to reduce the phase voltage unbalance from 4.2% to 0.23% for a 100%-100%-85% load imbalance over fundamental positive sequence control alone. Non-linear loads draw harmonic currents, and likewise cause harmonic distortion in power systems. A proposed harmonic control scheme is demonstrated to achieve near steady state errors for the low order harmonics due to non-linear loads. In particular, the THD is reduced from 22.3% to 5.2% for full three-phase diode rectifier loading, and from 11.3% to 1.5% for full balanced single-phase diode rectifier loading, over fundamental control alone. / Master of Science

A pressurized arch-shell structural component made of flexible material is considered. The component is inflated with high internal pressure. The behavior of similar types of structures, such as a pair of leaning pressurized arches and pressurized arch-supported membrane shelters, has been investigated in the past. More recently, several types of pressurized structures have been incorporated as part of the framework for a variety of structural systems. Particularly, the U.S. Army has been investigating the use of large lightweight and transportable pressurized arch-shell structures to be used as maintenance shelters for vehicles, helicopters, and airplanes. The formulated equations using thin shell theory are applied to a pressurized arch-shell component. A numerical investigation based on the Rayleigh-Ritz method is utilized to determine the behavior of arch-shells under various types of loading. The types of loading include a uniformly distributed vertical load representing snow, a wind load, and a horizontal side load distributed along the arc length. Deflections, stress resultants, and moments at various locations are computed for two types of shapes: circular and non-circular arch-shells. / Master of Science

Yes / This paper presents a method of generating realistic electricity load profile data for the UK domestic buildings. The domestic space heating and domestic hot water have been excluded in this study. The information and results of previous investigations and works that is available in public reports and statistics have been used as input data when modeling of domestic energy consumption. A questionnaire survey was conducted to find out what occupants do in different times of the day in order to get probabilistic estimates of usage of electrical household. The daily energy demand load profile of each appliance can be predicted using this method. A measured data set is also applied for comparison, and verification. Our analysis shows that the generated load profiles have a good agreement with real data. The daily load profile from individual dwelling to community can be predicted using this method.

No / This paper presents the structural behaviour of cold-formed steel cassette wall panels subjected to in-plane shear loads. To understand the influence of configuration, lining material and connector arrangement on the overall shear behaviour of typical cassette wall panels, different lining materials, fastener spacing and positions, edge stiffeners and specific boundary conditions were assumed in the numerical simulations. The comparison and analysis presented in this paper demonstrate typical effect factors to the load-bearing capacity of selected wall panel systems. In particular, the effect of wall opening to the structural shear behaviour of wall panels is highlighted.

The optimization of pallet design in today’s competitive supply chain is imperative to reduce costs and improve sustainability. With over two billion pallets in circulation in the United States, most packaged products are handled using unit loads and the interactions between the unit load components are not being considered in the pallet design process. This study aims to investigate the effect of the interlocking of layers and the pallet stacking patterns on pallet bending. This effect is part of a greater encompassing observed behavior known as load bridging, where a redistribution of the stresses on the pallet dependent on the characteristics of the load is generated. The bending of the unit load was measured under four common support conditions, warehouse racked across the width and length, fork tine support across the width and floor stacking. Five different pallet stacking patterns were then analyzed, comparing different interlocking levels, from column stacking to fully interlocking. It was identified that interlocking the layers causes a reduction in pallet deflection of up to 53% versus column stacking, and is more significant on lower stiffness pallets. The stacking patterns and interlocking levels also presented an effect on pallet deflection, albeit only for very low stiffness pallets when supported on its weakest components. A relationship between the observed results and a ratio of load and pallet stiffness was conducted, suggesting that when the load on the pallet is not significantly high in relation to the stiffness, load bridging won’t be observed. These results provide a guideline on improving pallet design and help furthering the understanding of the load bridging effect. / Master of Science / The optimization of pallet design in today’s competitive supply chain is imperative to reduce costs and improve sustainability. With over two billion pallets in circulation in the United States, most packaged products are handled using unit loads and the interactions between the unit load components are not being considered in the pallet design process. This study aims to investigate the effect of the interlocking of layers and the pallet stacking patterns on pallet bending. This effect is part of a greater encompassing observed behavior known as load bridging, where a redistribution of the stresses on the pallet dependent on the characteristics of the load is generated. Tests were conducted to measure the pallet bending performance under common scenarios, evaluating the effect of five different pallet stacking patterns. It was identified that when the layers of a unit load are interlocked, the pallet presents lower deflection (up to 53%). A relationship between the observed results and a ratio of load and pallet stiffness was conducted, suggesting that when the load on the pallet is not significantly high in relation to the stiffness, load bridging won’t be observed. These results provide a guideline on improving pallet design and help furthering the understanding of the load bridging effect.

A group of researchers, engineers, and government transportation officials have teamed up to design two bridges with simply-supported FRP composite structural beams. The Toms Creek Bridge, located in Blacksburg, Virginia, has been in service for six years. Meanwhile, the Route 601 Bridge, located in Sugar Grove, Virginia, has been in service for two years. Researchers have conducted load tests at both bridges to determine if their performance has changed during their respective service lives. The key design parameters under consideration are: deflection, wheel load distribution, and dynamic load allowance. The results from the latest tests in 2003 yield little, yet statistically significant, changes in these key factors for both bridges. Most differences appear to be largely temperature related, although the reason behind this effect is unclear. For the Toms Creek Bridge, the largest average values from the 2003 tests are 440 me for service strain, 0.43 in. (L/484) for service deflection, 0.08 (S/11.1) for wheel load distribution, and 0.64 for dynamic load allowance. The values for the Route 601 Bridge are 220 me, 0.38 in. (L/1230), 0.34 (S/10.2), and 0.14 for the same corresponding paramters. The recommended design values for the dynamic load allowance in both bridges have been revised upwards to 1.35 and 0.50 for the Toms Creek Bridge and Route 601 Bridge, respectively, to account for variability in the data. With these increased factors, the largest strain in the toms Creek Bridge and Route 601 Bridge would be less than 13% and 12%, respectively, of ultimate strain. Therefore, the two bridges continue to provide a large factor of safety against failure. / Master of Science

A structure comprised of two arches that lean against each other at the apex is considered. The arches are thin shells with internal pressure. This type of structure with solid arches has been used in bridges, such as the Gateway Arch Bridge in Columbus, Indiana, U.S.A., the Monongahela River Bridge in Pittsburgh, Pennsylvania, U.S.A., and a pedestrian bridge at the Pacific Tower in Paris, France. A series of leaning arches was incorporated in the frame of the Museum of the Moving Image, a temporary structure in London, England, during 1992-1994. Pressurized arch-shells made of a flexible material have been utilized as part of the framework for some transportable tent-like structures. The behavior of a pair of pressurized leaning arch-shells with various tilt angles, boundary conditions, and loads is investigated numerically. Several types of loads are considered, including uniformly-distributed vertical loads applied over all or half of the structure (representing snow), and wind loads on the structure. The arches are pinned or fixed to the ground. Deflections, vibrations, and stability of the structures are investigated using the finite element method. The effect of the tilt angle on the response is examined, and buckling may occur for some tilt angles under vertical loading. This type of structure has not been used widely, but may be effective for various applications. / Master of Science

Most of the techniques that have been applied to the short-term load forecasting problem fall within the time series approaches. The exception to this has been a new approach based on the application of expert systems. Recently several techniques have been reported which apply the rule-based (or expert systems) approach to the short-term load forecasting problem. However, the maximum lead time used for these forecasts has not gone beyond 48 hours, even though there is a significant difference between these algorithms in terms of their data base requirements (few weeks to 10 years). The work reported in this dissertation deals with two aspects. The first one is the application of rule-based techniques to weekly load forecast. A rule-based technique is presented that is capable of issuing a 168-hour lead-time load forecast. The second aspect is the development of a comprehensive load forecasting system that utilizes both the statistical and rule-based approaches. This integration overcomes the deficiencies that exist in both of these modeling techniques. The load forecasting technique is developed using two parallel approaches. In the first approach expert information is used to identify weather variables, day types and diurnal effects that influence the electrical utility load. These parameters and hourly historical loads are then selectively used for various statistical techniques (e.g., univariate, transfer function and linear regression). A weighted average load forecast is then produced which judiciously combines the forecasts from these three techniques. The second approach, however, is free of any significant statistical computation, and is based totally on rules derived from electric utility experts. The data base requirement for any of these approaches do not extend more than four weeks ol hourly load, dry bulb and dew point temperatures. When the algorithms are applied to generate seven-day ahead load forecasts for summer (August) and winter (February) the average forecast errors for the month come under 3%. / Ph. D.