This thesis presents the results of a research project that tested five friction reducing techniques on the bearing ends of precast prestressed concrete bridge girders. The five techniques were the following: an oil coated surface, embedded steel plate with an oil coated surface, embedded steel angle with an oil coated surface, teflon pad, and a wax lubricant.

The avian influenza virus can be transmitted from sick birds to other birds by fecal and oral secretion. Therefore, when birds with avian influenza virus enter domestic bird farms and make contacts, it is possible to carry the virus in and transmit it to domestic birds. Since the outbreak of the avian influenza in Taiwan, most bird farms had set up the screen. Yet, the actual effectiveness of screen coverage rate has not been researched. This study will discuss further regarding the results of different screen coverage rate in preventing wild birds¡¦ entering to poultry farms in Kaohsiung area. Field observations were carried out at the wetlands in Kaohsiung county, including Old Railroad Bridge artificial wetland, Fongshan reservoir and 20 poultry farms which were less than five kilometers away from wetlands from September 2008 to October 2009. Chicken and duck farms were analyzed respectively, and the screen coverage rate was categorized into full, partial and no coverage, respectively. The aims of the study were to investigate the effect of screen coverage on the entrance of wild birds to the farms, and found out the potential bridge species near poultry farms. By observing different levels of screen coverage in poultry farms, migratory birds¡¦ activity, and the contact situation between wild and domestic birds, we can analyze the contact level of high risk species and speculate possible transmission path of the avian influenza, and understand the effectiveness of the screens. Also, showing the correlation between the density of domestic poultry and the number of wild bird enterance. The result showed, in terms of screen with different coverage rates, the number of bird species within the duck farms had significant different in full and no coverage. The number of total birds within the duck and chicken farms with full coverage was significant less than partial coverage. Both in chicken and farms, screen had a great effectively in preventing small sized birds entering, yet not on big sized birds. The density of domestic poultry and the number of wild bird enterance showed negative correlation only in chicken farms with partial coverage. In terms of the wild land birds entering poultry farms, Passeer montanus is the largest species, followed by Hirundo rustica and Streptopelia tranquebarica. As for aquatic birds, it is mainly of Ardeidae, Scolopacidae, Charadriidae and Rallidae. Among all, Passeer montanus, Hirundo rustica, Streptopelia tranquebarica, and Bubulcus ibis are not migratory birds and highly pathogenic avian influenza virus species which move between poultry farms and wetlands. Therefore, they were considered bridge species. Due to the bridge species makes direct contacts with poultry, it might be the spreader of the virus. Decreasing the possibility of wild birds¡¦ contact with poultry is an important mechanism for avian influenza control. Also, based on the model of European Food Safety Authority (ESFA), risk assessments will be conducted on Kaohsiung County wetland¡¦s migratory birds¡¦ highly pathogenic avian influenza virus H5N1 transmission to poultry farms.

A full-depth precast concrete deck system presents several safety, timeline, and cost benefits to the process of constructing a bridge, however the relevant professional codes do not provide dependable design models due to the limited amount of research conducted on the subject. One area lacking design direction is the development of a shear connection between the full-depth precast deck and a precast concrete girder via a pocket-haunch-connector system. Push-off tests are performed to investigate the effects of various pre- and post-installed shear connectors, haunch height, surface roughness, grouping effects, and grout composition as compared to cast-in-place specimens. The experimental results are presented along with a method for normalizing the variations of results by connection yield strength. This method is used to evaluate each connector type and connection parameter investigated. Ensuring sufficient shear reinforcement within the beam near the shear connector anchorage is found to be a vital aspect of holistic design. A simplified design procedure is outlined, the design connection forcedisplacement behavior is shown, and an example problem is solved. Recommendations for additions and modifications to current code and practice are prescribed.

Segmental post-tensioned (PT) bridges are major structures that carry significant traffic. Recent investigations of these bridges have identified voids in their ducts. and some of these exposed strands at these void locations are undergoing corrosion. The corrosion of strands may lead to the failure of tendons. As such, an effective inspection process for identifying these voids is needed. From a literature review, several non-destructive testing (NDT) methods are compared for applicability in inspecting voids in external tendons. The impact echo (IE), ultrasonic pulse velocity (UPV), and sounding inspection methods were selected and assessed for identifying voids in preliminary test setup. The sounding inspection method is further assessed for its effectiveness in identifying voids in a full-scale, external tendon system. The results indicate that the sounding inspection slightly underestimates the size of the voids. However, the inspected size and locations of voids have a close correlation with actual voids in ducts. Thus, the sounding inspection can be an effective tool for identifying voids because of its easy application in the field. Recently, the investigated failures of segmental post-tensioned (PT) bridges called attention to the rehabilitation and mitigation methods of voided ducts in PT structures. Although controversy exists on how to best protect PT tendons from corrosion, filling these voids with grout may be one option. An optimized grouting procedure for repairing these voids is needed how best to protect the strands from corrosive environments. This research investigates three grouting methods for efficiently repairing the voids in PT duct systems. These methods are (1) vacuum grouting (VG), (2) pressure grouting (PG), and (3) pressure-vacuum grouting (PVG). Each method is being evaluated for filling capability, filling performance, and economic feasibility. Also, three different pre-packaged grouts for repair are assessed in this research to propose the most suitable material for repairing voided PT ducts. The results indicate that the PG and PVG methods are more constructible and likely more economical than the VG method. However, the PVG and VG methods seem to be more effective than the PG method in filling the voids. As a result of these tests, the PVG method is recommended for filling voids in tendons. The results also show that C-1 and C-2 grouts have better filling capability than C-3 grout. Although experimental tests using prototype specimens of external PT tendons are performed to propose an effective repair grouting method and material, the experimental conditions cannot cover all voids types, duct types, and other effects of repair grouting methods in the field. Thus, the grout flow in voided ducts is predicted using a commercial Computational Fluid Dynamics (CFD) program. The simulation of the flow is challenging due to the complicated geometry of voided ducts, but the simplified model in this research shows close correlations with experimental results. Thus, various parameters of repair methods and materials are assessed in this research, and the PVG method with grouts having low viscosity exhibited the best performance. If it is determined that filling voids with grout is appropriate and prevents future corrosion, it is recommended that voids in the field be filled using the PVG method with grouts exhibiting low viscosities.

Unknown bridge foundations pose a significant safety risk due to stream scour and erosion. Records from older structures may be non-existent, incomplete, or incorrect. Nondestructive and inexpensive geophysical methods have been identified as suitable to investigate unknown bridge foundations. The objective of the present study is to apply advanced 2D electrical resistivity imaging (ERI) in order to identify depth of unknown bridge foundations. A survey procedure is carried out in mixed terrain water and land environments with rough topography. A conventional resistivity survey procedure is used with the electrodes installed on the stream banks. However, some electrodes must be adapted for underwater use. Tests were conducted in one laboratory experimentation and at five field experimentations located at three roadway bridges, a geotechnical test site, and a railway bridge. The first experimentation was at the bridges with the smallest foundations, later working up in size to larger drilled shafts and spread footings. Both known to unknown foundations were investigated. The geotechnical test site is used as an experimental site for 2D and 3D ERI. The data acquisition is carried out along 2D profile with a linear array in the dipole-dipole configuration. The data collections have been carried out using electrodes deployed directly across smaller foundations. Electrodes are deployed in proximity to larger foundations to image them from the side. The 2D ERI can detect the presence of a bridge foundation but is unable to resolve its precise shape and depth. Increasing the spatial extent of the foundation permits better image of its shape and depth. Using electrode < 1 m to detect a slender foundation < 1 m in diameter is not feasible. The 2D ERI method that has been widely used for land surface surveys presently can be adapted effectively in water-covered environments. The method is the most appropriate geophysical method for determination of unknown bridge foundations. Fully 3D ERI method at bridge sites is labor intensive, time consuming, and does not add enough value over 2D ERI to make it worthwhile.

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The Lead-Acid battery has become the power source of several electron product. The major drawback is that it requires long charging time. This thesis is to design a programmable rapid charger and energy recovery scheme with DSP. Furthermore zero-voltage-switching(ZVS) capability of the adopted asymmetrical half-bridge topology enhances the power density of the charger. The energy recovery cell stores the negative pulse energy into DC bus capacitor temporarily to avoid unnecessary energy consumption in conventional schemes. This thesis is experimentally verified on 12V/7.5Ah nonspillable sealed-lead assembled batteries. According to experimental results, the charger can achieve the goal of rapid charge within 1 hour. Because of using the rapid charge algorithm, it can give different charging section depends on temperature and voltage of battery, and it can adjust the over-temperature and the over-voltage of battery to guarantee the battery be charged safely. In this thesis, a prototype module is implemented with mature protection condition. Some experiments are shown to verify the feasibility of the proposed scheme.

This thesis presents the design and implementation of a single-stage with high power factor asymmetrical half-bridge converter. The main structure combines a boost converter with an asymmetrical half-bridge. An Asymmetrical half-bridge converter has many advantages such as soft-switching properties and fewer components. Therefore it is suitable for DC/DC cell. The boost converter is used in a PFC cell that operating in discontinuous condition mode have innate ability of power factor correction without additional controller. In this thesis, the complete analysis of operation principle and design of controller for the equivalent circuits of a single-stage AC/DC converter in every operating stage have been described in detail. Finally, we construct the single-stage circuit and experimental result show that it can reach the expected goal for power-factor correction.

Jointless bridges are advantageous in removing mechanical joints which are a known cause of bridge deterioration. Elimination of joints provides a smoother riding surface and removes the possibility of de-icing salts penetrating the deck and corroding the deck reinforcing and underlying bridge superstructure. Jointless bridges are traditionally constructed by monolithically casting the entire bridge deck on beams after they have been erected. However, this process requires extensive in-field formwork and lengthy traffic closures. The Texas Department of Transportation proposes a new method of constructing jointless bridges using prefabricated girder-and-deck units connected on-site with cast-in-place closure pours. This new system will expedite construction and reduce disturbances to the traveling public. The objective of this experimental study was to investigate the behavior of the cast-in-place closure pour slab and to determine if it responds to wheel loads in the same way as a traditional monolithic continuous deck. The effects of the cold joints and discontinuous steel details are the focus of the research work.

Delay test in nano-scale VLSI circuits becomes more difficult with shrinking technology feature sizes and rising clock frequencies. In this dissertation, we study three challenging issues in delay test: fault modeling, variational delay evaluation and path selection under process variation. Previous research of fault modeling on resistive spot defects, such as resistive opens and bridges in the interconnect, and resistive shorts in devices, lacked an accurate fault model. As a result it was difficult to perform fault simulation and select the best vectors. Conventional methods to compute variational delay under process variation are either slow or inaccurate. On the problem of path selection under process variation, previous approaches either choose too many paths, or missed the path that is necessary to be tested. We present new solutions in this dissertation. A new fault model that clearly and comprehensively expresses the relationship between electrical behaviors and resistive spots is proposed. Then the effect of process variations on path delays is modeled with a linear function and a fast method to compute coefficients of the linear function is also derived. Finally, we present the new path pruning algorithms that efficiently prune unimportant paths for test, and as a result we select as few as possible paths for test while the fault coverage is satisfied. The experimental results show that the new solutions are efficient and accurate.