The Texas Department of Transportation (TxDOT) uses precast, prestressed concrete panels (PCPs) as stay-in-place formwork for most bridges built in Texas. The PCPs are placed on the top flanges of adjacent girders and topped with a 4-in. cast-in-place (CIP) slab. This thesis is directed towards identifying and quantifying the serviceability implications of reducing the deck reinforcement across the interior spans of CIP-PCP decks. The goal of this research is to understand how the PCPs influence cracking and crack control in the CIP slab and to make recommendations to optimize the top mat reinforcement accordingly. Several tests were conducted to evaluate the performance of different top mat reinforcement arrangements for ability to control crack widths across PCP joints. The longitudinal reinforcement was tested using a constant bending moment test, a point load test, and several direct tension tests. Because of difficulty with the CIP-PCP interface during the longitudinal tests, direct tension tests of the CIP slab only were used to compare the transverse reinforcement alternatives. Prior to testing, various top mat design alternatives were evaluated through pre-test calculations for crack widths. Standard reinforcing bars and welded wire reinforcement were considered for the design alternatives. During this study, it was found that the tensile strength of the CIP slab is critical to controlling transverse crack widths. The CIP-PCP interface is difficult to simulate in the laboratory because of inherent eccentricities that result from the test specimen geometry and loading conditions. Furthermore, the constraint and boundary conditions of CIP-PCP bridge decks are difficult to simulate in the laboratory. Based on the results of this testing program, it seems imprudent to reduce the longitudinal reinforcement across the interior spans of CIP-PCP decks. The transverse reinforcement, however, may be reduced using welded wire reinforcement across the interior spans of CIP-PCP decks without compromising longitudinal crack width control. A reduced standard reinforcing bar option may also be considered, but a slight increase in longitudinal crack widths should be expected. / text

Corrosion of embedded reinforcement is the leading form of deterioration affecting the integrity of reinforced and prestressed concrete bridge members around the world. If undetected, corrosion can limit the service life of the bridge and lead to expensive repairs. The research team at the University of Texas at Austin has developed a new class of passive wireless corrosion sensors. The noncontact (NC) sensor platform provides an economical and nondestructive means for detecting corrosion initiation within concrete. The sensor is powered through the inductive coupling to an external mobile reader that can be handheld or mounted on a vehicle. It is envisioned that the four-dollar sensor will be embedded in concrete during construction and interrogated sporadically over the service life of the structure. The sensor output can be used to detect corrosion initiation within concrete and is expected to enhance the quality information collected during qualitative routine bridge inspections. The NC sensor prototype consists of a resonant circuit that is inductively coupled to a sacrificial transducer. Corrosion of the sacrificial element alters the measured sensor response and is used to detect corrosion within concrete. Electrochemical evaluations were conducted to ensure that the sacrificial element exhibited identical response as the reinforcement steel. In addition, the results of extensive experimental parametric studies were used in conjunction with circuit and electromagnetic finite element models to optimize the NC sensor design. Long-term exposure tests were used to evaluate the reliability of the passive noncontact sensors. Sensors were embedded in reinforced concrete specimens and successfully detected the onset of corrosion in the adjacent reinforcement. Unlike the traditional corrosion evaluation methods, such as half-cell potentials, the sensors output was insensitive to environmental variations. / text

Bridges with orthotropic steel decks have been built across the world over the past 60 years because they provide high strength and stiffness at a relatively low cost. However, a number of these bridges have sustained fatigue fractures. The investigation described in this thesis was carried out in order to identify cost-effective fatigue crack mitigation techniques by using the deck surfacing to reduce the stresses in the steel deck. Epoxy asphalt with an expanded metal mesh was investigated with small- and large-scale laboratory tests. Finite element analyses were also performed. The small scale tests conducted at different temperatures and loading frequencies showed that asphalt stiffness increased with decreasing temperature and faster loading. The expanded metal mesh in the epoxy asphalt layer noticeably increased asphalt stiffness. In the large scale tests and finite element analyses, critical loading positions to cause stress concentrations at the fatigue prone rib-to-deck welded connections were determined with different tyre configurations. The stress reduction due to the deck surfacing was estimated for the critical loading positions. The full scale test specimen was subjected to actual truck tyres. With the effectiveness of mitigation techniques for fatigue cracks on orthotropic steel bridge decks known, a probability-based fatigue lifetime evaluation methodology using Monte Carlo simulation was developed. The deck surfacing effects with seasonal and hourly temperature variations were considered. The fatigue lifetime extension using the epoxy asphalt was quantified. For a particular bridge, cost-effective maintenance scenarios were investigated. A simple calculation method for fatigue lifetime was introduced for engineers or bridge owners to assist understanding of decision support tool concepts.

Maintenance and repair of deteriorating civil infrastructure are global problems requiring significant attention and resources. Accurate measurements of civil infrastructure enable lower repair and rehabilitation costs if mitigation techniques are deployed at earlier stages of deterioration. This research describes an infrastructure inspection solution to scan concrete bridge decks for internal cracking at high speeds. Internal cracking within bridge decks, known as delamination, is a particularly difficult defect to identify because it is often not detectable through visual inspection. State-of-the practice testing approaches involve the use of slow and subjective manual sounding techniques and costly lane closures. The need for an improved testing approach has led to decades of research investigating the use of acoustic impact-echo testing to detect bridge deck delaminations. The research presented here consists of a study of the acoustic radiation patterns of delamination defects when they are impacted. Acoustic data were collected on an in-service bridge deck and compared to acoustic data collected on defects in decommissioned bridge deck slabs and on simulated delaminations. This study examined cases of ideal and non-ideal delaminations on the in-service bridge deck and identified characteristics of non-ideal delaminations. An apparatus consisting of a high-speed impact-echo platform and recording suite was designed and constructed. Using this towed apparatus, an order-of-magnitude increase in scanning speed was obtained over other reported methods. Significant design effort was employed to achieve synchronization between different sensing devices using networked computer systems. Analysis was also developed to process and automatically classify acoustic responses to determine the presence and location of delaminations. Demonstrated performance against ground truth data obtained on an in-service bridge deck includes an achievement of approximately 90% probability of detection with only a 2% false alarm rate within 0.30 m. Because of the need to classify acoustic data when ground truth may not be obtainable, a new outlier rejection algorithm, which robustly removes outliers for classification on both simulated and field test data, was also developed. These contributions advance state-of-the-art bridge inspection and also lay the groundwork for additional studies of bridge deck deterioration processes. The framework also demonstrates how a tedious, subjective, and manual inspection process can be automated using advanced excitation tools, signal processing, and machine learning.

Nondestructive evaluation of civil infrastructure is increasingly important in the modern world to assess structures, predict longevity, and prescribe rehabilitation or replacement. For concrete bridge decks, one emerging diagnostic technique is vertical electrical impedance (VEI) testing, which is a nondestructive evaluation technology that quantitatively assesses the cover protection offered to steel reinforcement. Because VEI testing is still a relatively new approach to bridge deck inspection, additional studies are needed to increase the interpretability of VEI data. This thesis increases VEI interpretability with two advances. The first advance, presented in Chapter 2, offers an analytical model for interpreting VEI measurements of cracked bridge decks. The analytical model allows crack depth to be predicted from VEI measurements. The second advance, presented in Chapter 3, offers an interpretation of VEI measurements within the context of other, more typical, nondestructive bridge deck measurements. Surface cracks cause a significant acceleration of chloride ingress towards the steel reinforcement because they provide a direct path for chlorides to penetrate the concrete cover and corrode the steel. Estimating the depth of these cracks enables better prediction of chloride loading and influences predictions of service life. An invertible analytical model for VEI measurements of cracks based on a cylindrical dipole approximation is presented. This model is validated with numerical simulations, laboratory experiments, and destructive field tests performed on concrete parking garage decks. Inversion of the model permits depth estimation of cracks and a quantitative interpretation of VEI measurements for this specific concrete defect. An additional study was performed on a newly constructed bridge deck in Midvale, Utah, that was subject to an unexpected rainstorm during construction. Several forms of nondestructive testing, including VEI testing, were performed on the deck. Statistical analysis of the tests permitted assessment of the bridge deck. Comparing VEI testing with these other NDT methods has not been done before, and the results of this work will assist those who are unfamiliar with VEI with interpretation of VEI data in the context of other, more typical NDT techniques.

The use of precast concrete deck panels is becoming increasingly popular for bridge construction and rehabilitation in the state of Utah and across the country. It allows for the use of full depth concrete deck panels but removes the long construction times of traditional cast-in-place methods. One of the challenges to the use of precast deck panels is the transverse deck panel joints that exist between the panels. These joints are unreinforced using traditional methods and therefore are the weakest section of the bridge. In many situations the joint will fail and water seeps through and can damage the bridge superstructure. Post-tensioning of precast decks has become the standard. The post-tensioning provides reinforcing through the joints, reducing the cracking that occurs. Additionally, the post-tensioning provides pressure along the joint and closes cracks that have occurred, therefore preventing water from leaking through to the superstructure and damaging it. The Utah Department of Transportation uses post-tensioning cables that run along the length of the bridge deck, applying pressure on the joints. One of the problems with using this method is it does not allow for the replacement of a single deck panel should the need arise. Utah State University has been researching a new post-tensioned connection that would allow for the replacement of a single deck panel. The “curved bolt” connection connects each deck panel to adjacent panels, providing reinforcement and post-tensioning along the joint. Laboratory testing was undertaken to investigate the effects of single panel bridge rehabilitation on the existing deck system.

Moveable bridges in Florida typically use open steel grid decks due to the weight limitations. However, these decks present rideability, environmental, and maintenance problems, for they are typically less skid resistant than a solid riding surface, create loud noises, and allow debris to fall through the grids. Replacing open steel grid decks that are commonly used in moveable bridges with a low-profile FRP deck can improve rider safety and reduce maintenance costs, while satisfying the strict weight requirement for such bridges. The performance of the new deck system, which includes fatigue and failure tests were performed on full-size panels in a two-span configuration. The deck has successfully passed the preliminary strength and fatigue tests per AASHTO requirements. It has also demonstrated that it can be quickly installed and that its top plate bonds well with the wear surface. The thesis also describes the analytical investigation of a simplified finite element approach to simulate the load-deformation behavior of the deck system for both configurations. The finite element model may be used as a future design tool for similar deck systems. Loadings that were consistent with the actual experimental loadings were applied on the decks and the stresses, strains, and the displacements were monitored and studied. The results from the finite element model showed good correlation with the deflection and strain values measured during the experiments. A significant portion of the deck deflection under the prescribed loads is induced by vertical shear. This thesis presents the results from the experiments, descriptions of the finite element model and the comparison of the experimental results with the results from the analysis of the model.

No description available.

<p>Bridge deck deterioration due to chloride-induced pitting corrosion of steel reinforcement is a common occurrence. Because rust decreases the cross-sectional area of reinforcing bars, corrosion of bridge deck reinforcement directly reduces the structural capacity of the bridge deck. A typical NDT method for assessing the possibility of corrosion at the top reinforcement level is ground-penetrating radar (GPR). The goal of the study is to investigate the effect of reducing the cross-sectional area of the reinforcing bar on deck strength due to corrosion. Flexural and shear failure were considered in the analysis. In conclusion, typical corrosion of reinforcement was not found to cause a bridge deck to collapse after testing the flexure with the yield line method, the one-way and two-way shears with AASHTO LRFD Bridge Design Specifications (2020), and the one-way shear with ACI 318 (2019). </p>

Shallow geothermal energy (SGE) systems are becoming increasingly popular due to both their environmental and economic value. By using the ground as a source and sink for thermal energy, SGE systems are able to more efficiently heat and cool structures. However, their utility beyond structural heating and cooling is being realized as their applications now extend to slab and pavement heating, grain and agricultural drying, and swimming pool temperature control. Relatively recently, SGE systems have been combined with deep foundations to create a dual purpose element that can provide both structural support as well as thermal energy exchange with the subsurface. These thermo-active foundations provide the benefits of SGE systems without the additional installation costs. One of the novel applications of thermo-active foundations is in bridge deck deicing. Bridge decks experience two main winter weather related problems. The first of which is preferential icing, where the bridge freezes before the adjacent roadway because the bridge undergoes hastened energy loss due to its exposed nature. The second problem is the accelerated deterioration of concrete bridge decks resulting from the application of salts and other chemicals that are used to prevent accumulation and/or melt the frozen precipitation on roads and bridges. By utilizing the foundation of a bridge as a mechanism by which to access the shallow geothermal energy of the subsurface, energy can be supplied to the deck during the winter to melt and/or prevent frozen precipitation. An experimental ground-source bridge deck deicing system was constructed and the performance is discussed. Numerical models simulating the bridge deck and subsurface system components were also created and validated using the results from the numerical tests. Furthermore, the observed loads that result in a foundation from bridge deck deicing tests are shown. In order to better design for these loads, tools were developed that can predict the temperature change in the subsurface and foundation components during operation. Mechanisms by which to improve the efficiency of these systems without increasing the size of the borehole field were explored. Ultimately this research shows that SGE can effectively be used for bridge deck deicing. / Ph. D.