A bridge with precast bridge deck panels was built at the Virginia Tech Structures Laboratory to examine constructability issues, creep and shrinkage behavior, and strength and fatigue performance of transverse joints, different types of shear connectors, and different shear pocket spacings. The bridge consisted of two AASHTO type II girders, 40 ft long and simply supported, and five precast bridge deck panels. Two of the transverse joints were epoxied male-female joints and the other two transverse joints were grouted female-female joints. Two different pocket spacings were studied: 4 ft pocket spacing and 2 ft pocket spacing. Two different shear connector types were studied: hooked reinforcing bars and a new shear stud detail that can be used with concrete girders. The construction process was well documented. The change in strain in the girders and deck was examined and compared to a finite element model to examine the effects of differential creep and shrinkage. After the finite element model verification study, the model was used to predict the long term stresses in the deck and determine if the initial level of post-tensioning was adequate to keep the transverse joints in compression throughout the estimated service life of the bridge. Cyclic loading tests and shear and flexural strength tests were performed to examine performance of the different pocket spacings, shear connector types and transverse joint configurations. A finite element study examined the accuracy of the AASHTO LRFD shear friction equation for the design of the horizontal shear connectors. The initial level of post-tensioning in the bridge was adequate to keep the transverse joints in compression throughout the service life of the bridge. Both types of pocket spacings and shear connectors performed exceptionally well. The AASHTO LRFD shear friction equation was shown to be applicable to deck panel systems and was conservative for determining the number of shear connectors required in each pocket. A recommended design and detailing procedure was provided for the shear connectors and shear pockets. / Ph. D.

An efficient interaction formula and a semi-analytical method are developed for calculating the ultimate strength of steel-elastomer sandwich panels under combined in-plane compression and lateral pressure. By using the Galerkin method and extending the semi-analytical method to clamped sandwich panels, the governing equations of sandwich panels have been solved by the Galerkin method. The material nonlinearity is treated by iteration and a three-dimensional mesh. For the load case of pure lateral pressure, the ultimate strength from the semi-analytical method is similar to that from hinge line theory and finite element analysis (FEA). However, the semi-analytical method requires about as much computation as FEA, and it is therefore not suitable for design. Finite element modeling and nonlinear analysis are performed to calculate the ultimate strength of sandwich panels under combined load. The results agree with experimental results. This verifies the accuracy of the current finite element model. The verified finite element model is used to obtain the results for a large set of sandwich panels with various dimensions and load combinations. The FEA results for pure lateral pressure load cases are used to derive a correction factor for the hinge line formula. Statistical analysis confirms that the generalized hinge line formula gives accurate values of ultimate strength of sandwich panels under pure lateral pressure. Except for the pressure-only FEA data points, the other FEA data points are corrected so as not to count the in-plane load carried by the elastomer core. Based on the corrected FEA data points, a general expression is developed for an interaction equation. The resulting equation has a bias of -0.003 and a standard deviation of 0.029. Since the radius of the interaction curve is close to 1, this standard deviation is of the order of 3%, which shows that the ultimate strength given by the equation is very close to the FEA results. The interaction equation is so simple that the ultimate strength of clamped sandwich panels under combined in-plane compression and lateral pressure can be easily calculated. / Ph. D.

An efficient beam-column approach, using an improved step-by-step numerical method, is developed in the current research for studying the ultimate strength problems of stiffened panels with two load cases: 1) under longitudinal compression, and 2) under transverse compression. Chapter 2 presents an improved step-by-step numerical integration procedure based on (Chen and Liu, 1987) to calculate the ultimate strength of a beam-column under axial compression, end moments, lateral loads, and combined loads. A special procedure for three-span beam-columns is also developed with a special attention to usability for stiffened panels. A software package, ULTBEAM, is developed as an implementation of this method. The comparison of ULTBEAM with the commercial finite element package ABAQUS shows very good agreement. The improved beam-column method is first applied for the ultimate strength analysis of stiffened panel under longitudinal compression. The fine mesh elasto-plastic finite element ultimate strength analyses are carried out with 107 three-bay stiffened panels, covering a wide range of panel length, plate thickness, and stiffener sizes and proportions. The FE results show that the three-bay simply supported model is sufficiently general to apply to any panel with three or more bays. The FE results are then used to obtain a simple formula that corrects the beam-column result and gives good agreement for panel ultimate strength for all of the 107 panels. The formula is extremely simple, involving only one parameter: the product λΠorth2. Chapter 4 compares the predictions of the new beam-column formula and the orthotropic-based methods with the FE solutions for all 107 panels. It shows that the orthotropic plate theory cannot model the "crossover" panels adequately, whereas the beam-column method can predict the ultimate strength well for all of the 107 panels, including the "crossover" panels. The beam-column method is then applied for the ultimate strength analysis of stiffened panel under transverse compression, with or without pressure. The method is based on a further extension of the nonlinear beam-column theory presented in Chapter 2, and application of it to a continuous plate strip model to calculate the ultimate strength of subpanels. This method is evaluated by comparing the results with those obtained using ABAQUS, for several typical ship panels under various pressures. / Ph. D.

This dissertation research was a part of a multi-year research effort, objectives of which were (I) to characterize attentional demands of drivers performing automoltive instrument panel (IP) tasks, (2) to develop a methodology to quantify the driver attentional demands, (3) to examine a variety of factors which influence the visual attentional demand (VAD) and concurrent manual demand (CMD) through a comprehensive review of previous studies and a series of experiments, and (4) to develop a computer program to evaluate contemporary and future automotive IP designs on the basis of their attentional demands. In the first part of this dissertation, an extensive literature review of methodologies and findings concerning automotive IP task performance is presented. Most of the earlier studies reported task completion times (also referred to as response times and transaction times), which did not provide a precise detail of the operation of an instrument. More recent studies, on the other hand, recorded the driver's eye movements while performing an IP task, and measures of VAD were analyzed. Among the variety of methodologies to measure eye movements, the limbus and pupil tracking technique using a commercially available video cassette recorder (VCR) represents an ideal compromise among precision, cost, and size/weight. Combined with the traditional response time measure, the number and average length of glances, which are determined by a frame-by-frame analysis of the eye movement recording tape, allow a quantitative evaluation of driver IP task performance. A series of three experiments conducted in the moving-base driving simulator in the Vehicle Analysis and Simulation Laboratory forms the second part of this dissertation. The objectives of these experiments were (1) to validate the use of the driving simulator for collecting driver performance data on IP tasks, (2) to examine factors which influence the simulated driving workload, e.g., introduction of random crosswind and road curvature, (3) to expand the existing database on conventional IP tasks, (4) to examine the effects of IP macro- and micro-clutter on driver task performance, and (5) to investigate the issues related to control labelling, i.e., random versus sequential labelling and label abbreviation. Some of the important findings from the simulator experiments were (1) the driver IP task performance data collected under the zero crosswind and straight road conditions were found to be acceptably close to those in the in-car, on-road study during the first phase of this research program (Hayes, Kurokawa, and Wierwille, 1988), (2) IP macroclutter, represented by the number of instruments in the IP, was linearly related to the complexity of an IP task, reflected in the number of glances to IP, (3) IP microclutter, represented by the number of controls within an instrument, was linearly related to both complexity (number of glances to IP) and difficulty (average length of glances to IP) of an IP task, and (4) concise and distinct labels were more desirable as they required fewer glances and were located more quickly than their fully spelled counterparts. In the third part of this dissertation, a computer program (IPanalyzer) which was developed to aid automotive IP designers in evaluation of an IP design is discussed. Users of IPanalyzer can obtain driver IP task performance estimates (1) empirically from the existing experimental data, (2) by assessing the difficulty, complexity, and manual demand of a given task, or (3) by decomposing a task of interest into elements and categorizing them by their behavioral characteristics. Instructions for using IPanalyzer are supplemented by detailed descriptions and discussions of the data on which the driver IP task performance estimates are based. Finally, limitations of the current evaluation program are discussed, and a direction for future research and development are suggested. / Ph. D.

A set of experimental tests were performed at Virginia Tech to investigate transverse joints and blockouts on full depth concrete bridge deck panels. The joints were designed on a deck replacement project for a rural three span continuous steel girder bridge in Virginia. Two cast-in-place and four post-tensioned joints were designed and tested in cyclical loading. Each joint was tested on a full scale two girder setup in negative bending with a simulated HS-20 vehicle. The blockouts were built as hollow concrete rings filled with grout and left to shrink under ambient conditions. Thirteen combinations of different surface conditions and grouts were designed to test the bond strength between the materials. The strain profile, cracking patterns, and ponding results were measured for all specimens. A finite element analysis was performed and calibrated with the laboratory results. The cast-in-place joints and the two post-tensioned joints with 1.15 MPa (167 psi) of initial stress experienced cracking and leaked water by the end of the tests. The two post-tensioned joints with 2.34 MPa (340 psi) initial stress kept the deck near a tensile stress of 1.5√(𝑓'c) and performed the best. These transverse joints did not leak water, did not have full depth cracking, and maintained a nearly linear strain distribution throughout the design life. Full depth deck panel may be effectively used on continuous bridges if a sufficient amount of post-tensioning force is applied to the transverse joints. The finite element model provides a design tool to estimate the post-tensioning force needed to keep the tensile stresses below the cracking limit. The blockouts with a roughened surface or an epoxy and a grout equivalent to Five Star Highway Patch grout had the highest bond stresses, did not leak water, and had smaller cracks at the grout-concrete interface than the control samples. A minimum bond strength of 2.5√(𝑓'c) was maintained for all of the specimens with a grout equivalent to Five Star Highway Patch. A pea gravel additive in the grout reduced shrinkage and reduced the bond strength. The finite element model provides a design tool to estimate cracking at the grout-surface interface. / Ph. D.

As the aging bridges and infrastructure within the US continue to deteriorate, traffic delays due to construction will become more and more common. One method that can reduce delays due to bridge construction is to use precast deck panels. Precast deck panels can significantly reduce the overall length of the construction project. The panels can be manufactured ahead of time, and with higher quality control than is possible in the field. One of the reasons precast deck panels are not widely accepted is because of a lack of research concerning the required post-tensioning force, shear stud pocket placement, and proper joint design. In a recent dissertation (Swenty 2009) numerous recommendations were made for joint design, shear stud pocket design, and post-tensioning force for full-depth precast deck panel bridges. Design drawings were included for the replacement of a bridge located in Scott County, Virginia. The research in this report focuses on the short-term and long-term testing of this bridge. The short-term testing involved performing a live load test in which two trucks of known weight and dimensions were positioned on the bridge in order to maximize the negative moment at the joints over the piers and document strains and deflections at a number of other critical locations. The long-term testing involved monitoring the strains within the deck and on one of the six girders for a number of months in order to document the changes in strain due to creep and shrinkage. The results of these tests were compared to 2D beam-line models and to the parametric study results of Bowers' research on prestress loss within full-depth precast deck panel bridges. It was determined that the bridge was acting compositely and that the post-tensioning force was sufficient in keeping the joints in compression during testing. / Master of Science

In this investigation, thirty-six shear walls measuring 8 feet (2.4 m) in width and possessing heights of 8, 9 and 10 feet (2.4, 2.7 and 3.0 m) were subjected to the reversed, cyclic loading schedule of the standard CUREE protocol in order to determine the performance capabilities of shear walls greater than 8 feet (2.4 m) in height sheathed with long panels. Of the thirty-six walls, a total of twelve walls measuring 9 and 10 feet (2.7 and 3.0 m) in height were sheathed with 4 x 8 feet (1.2 x 2.4 m) panels which required additional blocking members between the studs of the frame. Values obtained from the tests performed on these walls provided a direct comparison to those obtained from the walls of equal height, but sheathed with a long panel capable of spanning the entire height of the wall. The capabilities of long panels were investigated when used as the sheathing elements of shear walls with and without a mechanical hold-down device attached to the base of the end stud. An advantage of the long panel was investigated in which it was extended past the bottom plate and down onto the band joist to determine if significant resistance to the uplift present in walls without mechanical hold-down devices could be provided. Also, the effects of orienting the fibers of a 4 x 9 feet (1.2 x 2.7 m) panel in the alternate direction were examined. Average values of the parameters produced by walls sheathed with long panels either matched or exceeded those of its counterpart sheathed with 4 x 8 feet (1.2 x 2.4 m) panels in all configurations except the 10 feet (3.0 m) tall wall without hold-down devices. In fact, 4 x 9 feet (1.2 x 2.7 m) panels increased the performance of 9 feet (2.7 m) tall walls equipped with hold-down restraint significantly. Extending the long panels past the bottom plate and down onto the band joist improved the performance of both 8 and 9 feet (2.4 and 2.7 m) tall prescriptive shear walls significantly. Walls sheathed with panels made of fibers oriented in the alternate direction performed identically to those sheathed with panels of typical fiber orientation until the point of peak load. Once peak load was reached, walls sheathed with panels of alternate oriented fibers failed in a more sudden and brittle manner. / Master of Science

Full-depth precast deck panels are a promising alternative to the conventional cast-in-place concrete deck. They afford reduced construction time and fewer burdens on the motoring public. In order to provide designers guidance on the design of full-depth precast slab systems with their full composite strength, the horizontal shear resistance provided at the slab-to-beam interface must be quantified through further investigation. Currently, all design equations, both in the AASHTO Specifications and the ACI code, are based upon research for cast-in-place slabs. The introduction of a grouted interface between the slab and beam can result in different shear resistances than those predicted by current equations. A total of 29 push off tests were performed to quantify peak and post-peak shear stresses at the failure interface. The different series of tests investigated the surface treatment of the bottom of the slab, the type and amount of shear connector and a viable alternative pocket detail. Based on the research performed changes to the principles of the shear friction theory as presented in the AASHTO LRFD specifications are proposed. The proposal is to break the current equation into two equation that separate coulomb friction and cohesion. Along with these changes, values for the coefficient of friction and cohesion for the precast deck panel system are proposed. / Master of Science

Twenty-four subjects, each having a valid Virginia driver's license (males and females of ages from 20 to 73), read aloud words presented on two displays while driving a simulated vehicle in night-time conditions. The words, emulating printed legends found on automobile instrument panels, were presented in different hues (eight levels), brightnesses (two levels), character sizes (four levels), and word complexities (two levels). The brightness levels had been subjectively determined in a preliminary experiment by subjects representative of the older and younger segments of the driver population. Each of two groups of drivers determined one brightness level that was subjectively equal among the eight hues. For each word presented, six reading and driving performance measures were taken. Also, subjective attractiveness, subjective comfort, and subjective ease of readability of each hue by brightness treatment combination, were measured. Globally, the results tend to indicate that color of illumination per se had a reliable effect on subjective preferences but a negligible effect on reading and driving performance. Brightness had an impact on performance only with the smaller character sizes. For the larger sizes, brightness level as selected by the subjects (in the preliminary experiment) had a negligible effect on performance. Character size had marked effects on both performance and subjective preferences. The two smaller character sizes tested yielded significant performance decrements for older drivers while the two larger sizes yielded best performance and were better accepted by all subjects. Word complexity did show a significant effect on glance time at the displays with all character sizes. The results of the experiment were transformed into a set of guidelines for use in design of automobile instrument panels. A number of recommendations for future research are also included. / Ph. D.

This experiment examined the directional relationships for six types of automobile controls: power mirrors, power windows, manual windows, stalks, generic controls, and power door locks. Two hundred driver-subjects participated in the research. Participants were divided into 4 groups of 50 each, and distributed according to age, gender, and type of vehicle they drove (domestic or foreign). During data collection, subjects were instructed to perform various types of control tasks. For each task, the direction of control activation chosen by the subject was observed and recorded. Frequencies of occurrence were then tabulated to grade the strength of directional stereotypes. In addition, statistical tests were conducted to determine the effects of age, gender, type of vehicle driven, and handedness on subject behavior. Confidence limits were also calculated and tabulated. In general, results showed that most control designs and configurations tested displayed moderate to strong stereotypes. However, weak directional stereotypes did occur whenever a control was angled away from the driver. Weak directional stereotypes were also prominent for manual window and power door !ock conditions. For the power window, the two controls mounted flush with the driver's door resulted in control selection problems (i.e., which control goes with which window), while the push-pull power window control resulted in weak directional stereotypes. The most salient result from the Chi-square statistical tests indicates that foreign car drivers utilize their stalk controls differently than domestic car drivers. Based on the overall results a list of design recommendations and directions for future research is offered. / Master of Science