Ground penetrating radar (GPR) technology has been used for the past 20 years for a variety of applications to assess transportation infrastructure. However, the main issue after all these years remains: "How well does GPR work and under what conditions?" Results show that GPR works well for some situations, but is not an appropriate tool for other situations. It is not used currently on a routine basis by the US Departments of Transportation (DOTs) due mainly to difficulties encountered with data interpretation. Data interpretation difficulties are mainly attributed to the fact that images obtained from the reflected signals are not photographs of the features that are beneath the surface being investigated. The images show the amplitude of the radar-reflected signals from the interfaces with different dielectric properties. Therefore, a considerable amount of experience and operator skill may be required to correctly interpret sub-surface radar results. To better understand reflected GPR signals, this research was conducted with the following objectives: to determine the dielectric properties of concrete over the used GPR frequency range; to synthesize the reflected air-coupled radar signals and compare them with measured waveforms; to model and study the effects of simulated defects in concrete on the reflected air-coupled and ground-coupled radar signals; and to validate the research results in the field by predicting layer thicknesses of flexible pavements and detecting moisture in flexible pavement systems. Several concrete slabs, 1.5x1.5 m, were constructed with known thicknesses, simulated defects, and different reinforcement configurations. The concrete mixes included four different bridge deck mixes and one concrete pavement mix used in the State of Virginia. Results have shown that the dielectric constant of concrete is frequency and mix dependent. However, modeling the reflected signals using an average complex dielectric constant over the entire radar frequency range led to modeled waveforms comparable to the measured waveforms. Although air- and water-filled voids did distort the reflected waveforms, a model was developed to predict the reflected waveforms from the simulated defects. Reinforcement was found to affect the reflected waveforms only when it was oriented in a direction perpendicular to the GPR antennas. A model was also developed to predict the GPR waveforms obtained from flexible pavements. This model could be used in a procedure to measure layer thicknesses more accurately by including losses that occur inside the pavement materials. Two different case studies, where a ground-coupled GPR system was used to locate moisture at different layers, have led to the conclusion that the ground-coupled GPR is a feasible tool to detect moisture inside pavements. / Ph. D.

The corrosion protection performance of epoxy-coated reinforcing steel (ECR) was evaluated in 18 concrete bridge decks in Virginia in 1997. The decks were 2 to 20 years old at the time of the investigation. The concrete bridge deck inspections included crack survey and cover depth determination in the right traffic lane. Maximum of 12 cores with the top reinforcement randomly located in the lowest 12th percentile cover depth and 3 cores with the truss bars were drilled from each bridge deck. The concrete core evaluation included visual examination and determination of carbonation depth, moisture content, absorption, percent saturation and chloride content at 13 mm depth. Rapid chloride permeability test was also performed for the surface and base concrete on samples obtained from cores containing truss bars. The ECR inspection consisted of visual examination and damage evaluation, coating thickness and adhesion determination. The condition of the steel underneath the epoxy coating was also evaluated. Adhesion loss of the epoxy coating to the steel surface was detected for 4 years old bridge decks. The epoxy coating had debonded from the reinforcing bar before the chloride arrival. Visible signs of a possibility of a corrosion process underneath the coating suggest that ECR will not provide any or little additional service life for concrete bridge decks in comparison to black steel. Other systems, which will provide longer protection with a higher degree of reliability against chloride induced corrosion of steel in concrete, should be considered. / Ph. D.

Two 7" deep FRP deck panels were manufactured and tested in a controlled service environment. The deck panels were 15' by 5' in plan, and were composed of ten 15' long, 6" by 6" by 3/8" standard pultruded FRP tubes. The tubes were sandwiched between two 3/8" thick standard pultruded FRP plates. The material constituents of the FRP were E-glass fibers in a polyester matrix. When subjected to two strength tests, the first deck panel exhibited a safety factor with respect to legal truck loads of greater than 10. The second deck was subjected to AASHTO design loads, and under a simulated HS-25 axle plus impact the deck exhibited a maximum deflection of L/470. Upon completion of the laboratory testing, the second deck was placed in the field for further study. The maximum strain recorded during field testing was approximately 600 microstrain, which is less than 15% of the ultimate tensile strain of the FRP in its weakest direction. After being subjected to approximately 4 million load cycles (assuming 100,000 5-axle truck crossings per month) over a period of 8 months, the deck exhibited no loss in stiffness. In two post-service strength tests, the second deck exhibited a safety factor with respect to legal truck loads of greater than 8 and greater than 13. / Master of Science

This thesis presents research completed on the experimental performance of two 6 3/4 in thick bridge deck panels fabricated by the Stongwell Corporation of Bristol, Virginia. The panels are made of off-the-shelf, pultruded glass fiber-reinforced polymer elements, bonded and mechanically fastened together. The testing involved laboratory stiffness tests performed on one deck panel which afterwards, was placed in a field test site at the I-81 Troutville Weigh Station facility. The daily truck traffic over the deck panel at this site is approximately 5400 vehicles. The second deck panel was constructed as a prototype to test benefits of steel thru-rod mechanical connectors. Further, a rubber tire loading patch was developed for the laboratory stiffness and strength tests performed on this second specimen to investigate modes of failure. Both decks made use of a hook bolt type connection to steel support beams in order to reduce damage seen in previous methods of connection. / Master of Science

A model to determine the time to first repair and subsequent rehabilitation of concrete bridge decks exposed to chloride deicer salts that recognizes and incorporates the statistical nature of factors affecting the corrosion process is developed. The model expands on an existing deterministic model using statistical computing techniques, including resampling techniques such as the parametric and simple bootstrap. Emphasis was placed on the diffusion portion of the diffusion-cracking model, but advances can be readily included for the time for corrosion deterioration after corrosion initiation. Data collected from ten bridge decks built in Virginia between 1981 and 1994 was used to model the surface chloride concentration, apparent diffusion coefficient, and clear cover depth. Several ranges of the chloride corrosion initiation concentration, as determined from the available literature, were investigated. The time to first repair and subsequent rehabilitation predicted by the stochastic model is shorter than the time to first repair and subsequent rehabilitation predicted by the deterministic model, but is believed to more accurately reflect the true nature of bridge deck deterioration. The model was validated using historical service life data for 129 bridge decks built in Virginia between 1968 and 1972. The time to rehabilitation predicted for the set of bridge decks built between 1981 and 1994 by the stochastic model was approximately 13 years longer than the normalized time to rehabilitation projected for the bridge decks built between 1968 and 1972 using historical data. The increase in time to rehabilitation for the newer set of bridge decks was attributed to a reduction in the specified maximum water/cement ratio and increase in clear cover depth. / Master of Science

The primary objective of this project was to test a full-scale prototype of an actual bridge deck containing GFRP bars as the top mat of reinforcement. The purpose of the tests was to verify that the design would resist the loads for which it was designed and provide assurance that the deck would not unexpectedly fail due to the use of this new material. Behavior of the bridge and deck, such as failure load, failure mode, cracking load, crack widths, deflections, and internal stresses, were examined. Four tests were performed on the deck, all of which tested the deck in negative moment regions. From the tests, it was concluded that the design of the deck was very conservative and that unexpected failure should be of no concern. The secondary objective of this project was to comment on the construction of a bridge deck reinforced with GFRP bars and to note its advantages and disadvantages along with a critique of the current state-of-the-art of designing bridge decks with FRP reinforcement. It was found that the advantages of construction with GFRP bars far outweighed the disadvantages, and that the placing of the top mat of GFRP bars was much easier than the placing of the bottom mat of steel bars. It was also concluded that the current state-of-the-art of designing bridge decks reinforced with GFRP is, for the most part, inaccurate in its prediction of behavior and that more research is needed to create more accurate design equations and procedures. Although current methods do not result in accurate predictions of behavior, they do, as mentioned above, result in conservative designs. / Master of Science

Approved for public release, distribution unlimited / This research will be used to evaluate the feasibility of robotically, or remotecontrolled firefighting nozzles aboard air-capable ships. A numerical model was constructed and analyzed, using the program CFD-ACE, of a fire hose stream being deflected by the influence of a crosswind, tailwind, or headwind. The model is intended to predict the reach of the fire hose stream, indicate the distribution pattern, and estimate the volume of fire fighting agent available at the end of the stream. Preliminary results for a two fluid cross flow model have been obtained. / US Navy (USN) author.

As pontes de madeira com tabuleiro multicelular protendido são uma das mais recentes tecnologias usadas na construção das modernas pontes de madeira. Nesta tese é realizado o estudo teórico e experimental do comportamento estrutural destas pontes. Os principais métodos de cálculo são apresentados e discutidos. A investigação experimental foi realizada em dois modelos reduzidos em escala 1:3 com as mesmas dimensões externas mas diferente quantidade de nervuras. Os modelos foram ensaiados com diferentes posições de carregamento enquanto os deslocamentos, deformações e forças nas barras, eram monitorados. Os resultados obtidos demonstraram que os modelos de Placa Ortotrópica Equivalente e Elementos Finitos podem ser empregados para o dimensionamento das pontes de madeira com tabuleiro multicelular protendido. O método de Viga Equivalente pode ser empregado desde que utilizado o correto Fator de Distribuição de Carga. Os estudos realizados neste trabalho, indicam a viabilidade da utilização deste sistema estrutural para pontes com vãos de 12 a 25 m / Timber bridges with multicellular prestressed decks is one of the most recent technology for modern timber bridges construction. In this thesis the theoretical and experimental study of the structural behavior of these bridges is accomplished. The main calculation methods are introduced and discussed. Two reduced models on scale 1:3, with the same external dimensions but different number of webs, were used for the experimental investigation. The models were tested with different load positions meanwhile displacements, strains and bar forces were measured. The obtained results have show that either model of Equivalent Orthotropic Plate or Finite Elements can be used for the design of this type of bridge. The Equivalent Beam model can also be employed as long as the correct Load Distribution Factor is chosen. The accomplished studies demostrate that this structural system is viable for bridges with span from 12 to 25 m

Structures made of chromated copper arsenic (CCA) have been shown to leach arsenic into the surrounding soil. Soil cores were taken adjacent to six CCA decks at 0, 15, 60 and 300 cm from the deck at depths of 0–10, 10–20, and 20–30 cm, and were analyzed for soil arsenic concentrations. Median soil arsenic concentrations ranged from 1.8 μg/g at a depth of 10–20 cm and a distance of 300 cm to 34.5 μg/g at a depth of 0–10 cm and a distance of 30 cm. Soil arsenic concentrations taken at depths of 0–10 and 10–20 cm decreased as distance from the deck increased. Soil arsenic concentrations close to the deck were higher at lower soil depths and at homes with greater deck wipe arsenic concentrations. Age of deck and slope of land had significant effects on the differences in arsenic concentrations between samples taken at different distances when evaluated in models by themselves, but not in models adjusting for deck wipe concentrations. Size of deck and bulk density of soil did not have significant effects on soil arsenic concentrations.

Throughout the United States accelerated bridge construction is becoming increasingly popular to meet growing transportation demands while keeping construction time and costs to a minimum. This research focuses on eliminating the need to form full-depth concrete bridge deck overhangs, accelerating the construction of concrete bridge decks, by using full-depth precast prestressed concrete deck panels. Full-depth precast overhang panels in combination with cast-in-place (CIP) reinforced concrete are experimentally and analytically investigated to assess the structural performance. Experimental loaddeformation behavior for factored AASHTO LRFD design load limits is examined followed by the collapse capacity of the panel-to-panel seam that exists in the system. Adequate strength and stiffness of the proposed full-depth panels deem the design safe for implementation for the Rock Creek Bridge in Fort Worth, Texas. New failure theories are derived for interior and exterior bridge deck spans as present code-based predictions provide poor estimates of the ultimate capacity. A compound shear-flexure failure occurs at interior bays between the CIP topping and stay-in-place (SIP) panel. Overhang failure loads are characterized as a mixed failure of flexure on the loaded panel and shear at the panel-to-panel seam. Based on these results design recommendations are presented to optimize the reinforcing steel layout used in concrete bridge decks.