The objective of this research is the evaluation of shear behavior of full-scale reinforced concrete T-beams strengthened with carbon fiber reinforced polymer (CFRP) sheets and CFRP anchors. Although the CRFP material has high tensile strength, premature failure due to debonding CFRP sheets prevents utilizing that strength. The use of CFRP anchors prevents this failure, so the CFRP sheets are able to reach ultimate strain. The current shear design is based on plasticity, which assumes that all steel (ductile material) stirrups, across the critical section yield at ultimate. However the strain in the CFRP (brittle material), is essential to estimate the shear contribution of CFRP. To evaluate the validity of CFRP strengthening for shear, 24 tests were conducted with several parameters including shear-span-to-depth ratio, depth of beams, different transverse reinforcement ratios, and the layout of CFRP strips. In addition, a simple shear behavior model was developed to explain the differences between ductile and brittle material. From test observation, the use of CFRP anchors resulted in U-wrap application to perform like continuous wrapping which implies that a CFRP strip reached rupture strain because the anchors prevented debonding failure. However, all FRP strips did not rupture simultaneously because the strain distribution across a critical crack was not uniform. The average strain across the critical crack was about 0.005. Therefore a conservative value of effective strain (0.004) was selected for design purposes. In addition, when a beam is strengthened with CFRP, interactions between the contributions of the CFRP, steel or concrete must be taken into account. Factors ka, ks, and kf were introduced in the proposed shear design equations. Factor ka reflects the change in the material contributions as the shear span to depth ratio (a/d ratio) changes in deep beams. Factors ks and kf account for the change in steel or CFRP shear contribution due to the change in the critical crack angle as well as the interactions between the steel and FRP transverse reinforcement. As the amount of either steel or FRP material increase, the efficiency of the other material decreases. / text

This thesis is a product of the U.S. Army Corp of Engineer's desire to develop a more accurate procedure for estimating the load capacity of an in-service T-beam bridge. A bridge type that is a stumbling block for U.S. Army field engineers due to the unknown amount and placement of the flexural reinforcement in the T-beam girder cross-sections. Personnel from the U.S. Army Corp of Engineer's Waterways Experiment Station in cooperation with personnel from Virginia Tech conceived a procedure that is potentially more accurate, can be quickly executed in the field, and is relatively easy to use by field engineers. In general, the procedure provides a method for transition between the quantity of flexural reinforcement in a reinforced concrete T-beam and the member's actual moment of inertia. Specifically, the goal of this thesis is to evaluate the accuracy of selected, effective moment of inertia models as a component in the proposed analysis procedure. The accuracy of the selected models is evaluated with test data generated from a testing program detailed herein, which load tested full-scale reinforced concrete T-beams. The test specimens were subjected to a closely-spaced, tandem-axle load configuration, a load configuration typical of military equipment. / Master of Science

In recent years, artificial neural networks (ANNs) have been employed for estimation and prediction purposes in many areas of civil/structural engineering. In this thesis, multilayered feedforward backpropagation algorithm is used for the approximate analysis and calibration of RC T-beam bridges and modeling of bridge ratings of these bridges. Currently bridges are analyzed using a standard FEM program. However, when a large population of bridges is concerned, such as the one considered in this project (Pennsylvania T-beam bridge population), it is impractical to carry out FEM analysis of all bridges in the population due to the fact that development and analysis of every single bridge requires considerable time as well as effort. Rapid and acceptably approximate analysis of bridges seems to be possible using ANN approach. First part of the study describes the application of neural network (NN) systems in developing the relationships between bridge parameters and bridge responses. The NN models are trained using some training data that are obtainedfrom finite-element analyses and that contain bridge parameters as inputs and critical responses as outputs. In the second part, ANN systems are used for the calibration of the finite element model of a typical RC T-beam bridge -the Manoa Road Bridge from the Pennsylvania&rsquo / s T-beam bridge population - based on field test data. Manual calibration of these models are extremely time consuming and laborious. Therefore, a neural network- based method is developed for easy and practical calibration of these models. The ANN model is trained using some training data that are obtained from finite-element analyses and that contain modal and displacement parameters as inputs and structural parameters as outputs. After the training is completed, fieldmeasured data set is fed into the trained ANN model. Then, FE model is updated with the predicted structural parameters from the ANN model. In the final part, Neural Networks (NNs) are used to model the bridge ratings of RC T-beam bridges based on bridge parameters. Bridge load ratings are calculated more accurately by taking into account the actual geometry and detailing of the T-beam bridges. Then, ANN solution is developed to easily compute bridge load ratings.

The inverted T-beam bridge system is a bridge construction technique that follows accelerated bridge construction processes. The system was discovered in France and first adopted in the U.S. by the Minnesota Department of Transportation. In 2012 the system was modified and adopted by Virginia, with research being carried out at Virginia Polytechnic Institute and State University (Virginia Tech). The research focused on multiple items involving the system, but the most relevant one is that regarding the transverse bending behavior of the system for different geometries, and joint types between adjacent precast beam members. The study found that using a joint system without any mechanical connection between adjacent beams was most efficient, and gave adequate performance under monotonic loading. The study recommended cyclic load testing be carried out on this joint type, as well as a welded joint similar to those found in decked bulb-T systems. The research contained herein presents the setup and results of this testing. From the work it was found that the no-connection joint behaves adequately under cyclic loading at service loads, however surface roughening between precast and cast-in-place concrete must be adequate. The welded connection behaves well, granted the surfaces to be welded are properly prepared. From these results it is recommended to evaluate different surface roughening techniques, and repeat the cyclic testing using the best. The surface roughening technique chosen should be used to provide guidance on this aspect of construction with inverted T-beams. / Master of Science

This thesis investigates the impact of interface surface treatment methods for use in the Virginia Inverted T-Beam bridge system. The specific system consists of precast beams with thin bottom flanges placed next to one another, with a cast-in-place slab on top. Previous research has shown that the strength of this system after cyclic loading is highly dependent upon the shear strength of the interface between the precast and cast-in-place sections, especially for the adhesion-based connection configuration. The approval of this bridge system for use in bridges with high daily traffic volumes hinges on the verification of its strength and durability for a 50-year lifespan. The shear strength of ten different surface textures was tested using push-off tests to determine which interface roughening methods would prove adequate for use in the bridge system. The strength was found to depend on both the amplitude and the geometry of the undulations on the beam-to-slab interface. Using this information, a texture was selected for a new trial of the adhesion-based connection configuration, and a test specimen was constructed. After completing cyclic loading to simulate the design life of the bridge, it was found that the system achieved a strength similar to previous monotonically loaded specimens. It was concluded that the bridge is safe for use in high daily traffic areas provided that a surface roughening with adequate shear strength is used. / Master of Science

The deterioration of highway bridges and structures and the cost of repairing, rehabilitating, or replacing deteriorated structures is a major issue for bridge owners. An aging infrastructure as well as the need to upgrade structural capacity for heavier trucks adds to problem. Life-cycle cost analysis (LCCA) is a useful tool for determining when the deployment of fiber-reinforced polymer (FRP) composite components is an economically viable alternative for rehabilitating deteriorated concrete bridges. The use of LCCA in bridge design and rehabilitation has been limited. The use of LCCA for bridges on a project level basis has often been limited to the non-routine design of major bridges where the life-cycle cost model is customized. LCCA has historically been deterministic. The deterministic analysis uses discrete values for inputs and is fairly simple and easy to do. It does not give any indication of risk, i.e. the probability that the input values used in the analysis and the resulting life-cycle cost will actually occur. Probabilistic analysis accounts for uncertainty and variability in input variables. It requires more effort than a deterministic analysis because probability distribution functions are required, random sampling is used, and a large number of iterations of the life-cycle cost calculations are carried out. The data needed is often not available. The significance of this study lies in its identification of the parameters that had the most influence on life-cycle costs of concrete bridge and how those parameters interacted. The parameters are: (1) Time to construct the new bridge; (2) traffic volume under bridge (when applicable); (3) value of time for cars; and (4) delay time under the bridge during new bridge construction (when applicable). Using these parameters the analyst can now “simulate” a probabilistic analysis by using the deterministic approach and reducing the number of iterations. This study also extended the use of LCCA to bridge rehabilitations and to bridges with low traffic volumes. A large number of bridges in the United States have low traffic volumes. For the highway bridge considered in the parametric study, rehabilitation using FRP had a lower life-cycle cost when compared to the new bridge alternative.

Non-contact lap splices placed within a single concrete placement are often used and have been studied in previous research projects. However, non-contact lap splices used with each bar in a different concrete placement such that there is a cold joint between the bars, have not been investigated. This situation is found in the repair of adjacent box beam bridges and in the construction of inverted T-beam systems, among others. It is vital to understand whether the same mechanisms are present across a cold joint with two different types of concrete as are present in traditional non-contact lap splices. In this research, eight T-beam specimens with non-contact lap splices were tested. The spacing between the bars, the splice bar blockout length, and presence of transverse bars were varied to study the effectiveness of the splices. The beams were tested in four point bending so that the splice region was under constant moment and the tension forces in the spliced bars were constant. End and midspan deflections were measured along with surface strain measurements at midspan and at the quarter span points, top and bottom. Gap openings were also measured at the ends of the blockouts. The main conclusions found from this research are that beams containing non-contact lap splices were able to develop nominal capacity with the bar spacing less than or equal to 4 in. and the blockout between 17 and 20 in. long. Extending the blockouts and adding transverse bars underneath the splices did not add to the capacity. / Master of Science

Most of the reinforced concrete systems are monolithic. During construction, concrete from the bottom of the deepest beam to the top of slab, is placed at once. Therefore the slab serves as the top flange of the beams. Such a beam is referred to as T-beam. In a floor system made of T-beams, the compressive stress is a maximum over the web, dropping between the webs. The distribution of compressive stress on the flange depends on the relative dimensions of the cross section, span length, support and loading conditions. For simplification, the varying distribution of compressive stress can be replaced by an equivalent uniform distribution. This gives us an effective flange width, which is smaller than the real flange width. In various codes there are recommendations for effective flange width formulas. But these formulas are expressed only in terms of span length or flange and web thicknesses and ignore the other important variables. In this thesis, three-dimensional finite element analysis has been carried out on continuous T-beams under different loading conditions to assess the effective flange width based on displacement criterion. The formulation is based on a combination of the elementary bending theory and the finite element method, accommodating partial interaction in between. The beam spacing, beam span length, total depth of the beam, the web and the flange thicknesses are considered as independent variables. Depending on the type of loading, the numerical value of the moment of inertia of the transformed beam crosssection and hence the effective flange width are calculated. The input data and the finite element displacement results are then used in a nonlinear regression analysis and two explicit design formulas for effective flange width have been derived. Comparisons are made between the proposed formulas and the ACI, Eurocode, TS-500 and BS-8110 code recommendations.

Als Ergänzung für die Lehrbriefe des Instituts für Massivbau der TU Dresden zu den Grundlagen des Stahlbetons (Teil 1 und 3 sowie Übungen Teil 1 bis 3) werden hier Bilder von Versuchsreihen vorgestellt, die am Lehrstuhl für Stahlbeton, Spannbeton und Massivbrücken der TH/TU Dresden, aus dem das heutige Institut für Massivbau hervorging, innerhalb verschiedener Forschungsarbeiten von 1956 bis 1965 entstanden. Neben dem Einblick in die damaligen Arbeitsweisen und Möglichkeiten sind vor allem die zahlreichen Bruchbilder geeignet, sich in das Tragverhalten des Stahlbetons hineinzudenken. Diese Überlegungen gaben den Ausschlag dafür, das vorhandene Bildmaterial noch einmal zu ordnen und mit kurzen Erläuterungen zu versehen, um es so nochmals für Lehre und Forschung nutzbar zu machen.

Als Ergänzung für die Lehrbriefe des Instituts für Massivbau der TU Dresden zu den Grundlagen des Stahlbetons (Teil 1 und 3 sowie Übungen Teil 1 bis 3) werden hier Bilder von Versuchsreihen vorgestellt, die am Lehrstuhl für Stahlbeton, Spannbeton und Massivbrücken der TH/TU Dresden, aus dem das heutige Institut für Massivbau hervorging, innerhalb verschiedener Forschungsarbeiten von 1956 bis 1965 entstanden. Neben dem Einblick in die damaligen Arbeitsweisen und Möglichkeiten sind vor allem die zahlreichen Bruchbilder geeignet, sich in das Tragverhalten des Stahlbetons hineinzudenken. Diese Überlegungen gaben den Ausschlag dafür, das vorhandene Bildmaterial noch einmal zu ordnen und mit kurzen Erläuterungen zu versehen, um es so nochmals für Lehre und Forschung nutzbar zu machen.