No description available.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains vi, 76 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 60-61).

The search for a better method of analyzing skew arches and rigid frames has gone on for years. During that time many theories were presented, most of which were an improvement or a simplification of previous methods. However, no exact analytical solution, based on classical plate theory, for the analysis of skewed plates as found in rigid-frame bridges had been developed prior to this thesis. As previously mentioned, the complete solution is being presented in three separate theses. This thesis contains all the equations needed for the analysis that arise from considering the extensional forces acting in the skewed slab. All the equations have been given in the form of an infinite series. These equations, together with the ones for the other parts of this problem, must be expanded for a few terms, combined and solved. Due to the size and number of equations involved, the only practical solution would involve the use of a modern high-speed computer. Since Virginia Polytechnic Institute has a computer of this type, the entire analysis could he completed at the college. Once the results are obtained, a comparison can be made with the experimental analysis referred to in the thesis. / Master of Science

The focus of this research was primarily on corrosion of the reinforcing steel (rebars) in bridge decks. It has been estimated that over $20 billion is required to repair or rehabilitate corrosion induced deficient bridge decks and that the cost is rising at the rate of $0.5 billion annually. Corrosion occurs when there is a sufficiently high concentration of chloride ions at the top rebar mat. The principal source of chloride ions is from the deicing salts applied on the decks during winter. More than 9 million tons of deicing salts are consumed each year in the U.S.A. As corrosion products have a larger volume than steel, corrosion causes cracking and spalling of the deck. Concrete laboratory specimens with rebars were cast and subjected to a chloride environment. The corrosion potential and rate were monitored with Cu-CuSO₄ half-cell and the 3LP device, respectively. When active corrosion had been initiated, the specimens were treated in six ways, one being the 'control'. Two overlay types and polymer impregnation were used in all combinations as treatment methods. The specimens which were impregnated were grooved and dried to 230 °F prior to impregnation and polymerization. The post-treatment corrosion rates were appreciably reduced. Mortar cubes were made, dried to different temperatures between room temperature and 600 °F, impregnated and polymerized. The cubes were then vacuum saturated and their resistivity obtained. They were then cut, dried to 220 °F and the effects of drying temperature was evaluated using a Mercury Porosimeter and a Scanning Electron Microscope. The cubes were subjected to a chloride environment and subsequent chloride content was determined. The results suggested that a lower drying temperature was sufficient for effective impregnation. Other laboratory specimens were dried to 150 °F and 180 °F and impregnated as before. The post treatment corrosion rates supported the conclusions determined in the cube study. / Master of Science

No description available.

Thesis (M.S. in Engineering)--University of Texas at Austin, 2009. / Title from PDF title page (University of Texas Digital Repository, viewed on Aug. 10, 2009). Includes bibliographical references (leaves 119-120).

The research presented in this dissertation focuses on the material characterization of ultrahigh performance fiber reinforced concrete (UHP-FRC) at both the microscopic and macroscopic scales. The macroscopic mechanical properties of this material are highly related to the orientation of the steel fibers distributed within the matrix. However, the fiber orientation distribution has been confirmed to be anisotropic based on the flow-casting process. The orientation factor and probability density function (PDF) of the crossing fiber (fibers crossing a cutting plane) orientation was obtained based on theoretical derivations and numerical simulations with respect to different levels of anisotropy and cut planes oriented arbitrarily in space. The level of anisotropy can be calibrated based on image analysis on cut sections from hardened UHP-FRC prisms. Simplified equations provide a framework to predict the mechanical properties based on a single fiber-matrix interaction rule selected from existing theoretical models. Along with the investigation of the impacts from different curing methods and available post-cracking models, a versatile parameterized uniaxial stress-strain constitutive model was developed and calibrated. The constitutive model was implemented in a finite element analysis software program, and the program was utilized in the preliminary design of moveable bridge deck panels made of passively reinforced UHP-FRC. This deck system was among the several alternatives to replace the problematic steel grid decks currently in use. Based on experimental investigations of the deck panels, failure occurred largely in shear rather than flexure during bending tests. However, this shear failure is not abrupt and usually involves large deformation, large sectional rotation, and wide shear cracks before loss of load-carrying capacity. This particular shear failure mode observed was further investigated numerically and experimentally. Three-dimensional FEM models with the ability to reflect the interaction between rebar and concrete were created in a commercial FEM software to investigate the load transfer mechanism before and after bond failure. Small-scale passively reinforced prisms were tested to verify the conclusions drawn from simulation results. In an effort to improve the original design, several shear-strengthened deck panels were tested and evaluated for effectiveness. Finally, methods and equations to predict the ultimate shear capacity iii were calibrated. A two-dimensional frame element based complete moveable bridge finite element model was built for observation of bridge system performance. The model contained the option to substitute any available deck system based on a subset of pre-calibrated parameters specific to each deck type. These alternative deck systems include an aluminum bridge deck system and a glass fiber reinforced plastic (GFRP) deck system. All three alternatives and the original steel grid deck system were evaluated based on the global responses of the moveable bridge, and the advantages and disadvantages of adopting the UHP-FRC deck system are quantified.

The purpose of this research was to evaluate the performance history of continuous bridge decks in the State of Georgia, to determine why the current design detail works, to recommend a new design detail if necessary, and to recommend the maximum and/or optimum lengths of continuous bridge decks. The continuous bridge decks have continuous reinforcement over the junction of two edge beams with a construction joint for crack control. The current technical literature and current practices and design procedures were synthesized and summarized. GDOT maintenance reports were reviewed, and field evaluations were conducted to determine the performance of the continuous deck detail. The effects of bridge movement due to thermal strains, shrinkage, and live loads were considered in the analytical studies to better understand the demands placed on the GDOT continuous deck detail. A summary of the design and length recommendations was provided upon completion of the research.

The highway network in the United States, specifically reinforced concrete bridges, is deteriorating at a rapid rate. It is known that chloride-induced corrosion of the reinforcing steel is one of the major causes of the deterioration of concrete bridge decks. Numerous bridge deck protection and overlay systems have been developed to reduce the deterioration rate caused by chloride-induced corrosion. This study investigated the service life of untreated concrete bridge decks and four bridge deck overlay systems: low-slump-dense concrete (LSDC), latex-modified concrete (LMC), micro-silica concrete (MSC), and preformed membranes with hot-mix asphalt overlays (PM-HMA). The research plan consisted of organizing and analyzing data obtained in a 1991 field survey of 52 bridges from various locations in the nation. The field survey was conducted to gather information on existing conditions of untreated and rehabilitated bridge decks. Corrosion measurements were taken to assess the performance of each technique. Statistical models that predict the percent of deterioration on a bridge deck and the corrosion rate for each technique were developed from the field survey data. The components of a deterioration model were combined to define the service life for each bridge deck overlay system and for untreated concrete bridge decks. Other service life estimates for untreated bridge decks and bridge deck overlay systems were also compared. Based on the statistical analysis and service life comparisons, a service life estimate was recommended for predicting the service life for three of the bridge deck overlay systems. / Master of Science