Browsing by Author "Harris, Devin K."

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    Characterization of Punching Shear Capacity of Thin Uhpc Plates
    Harris, Devin K. (Virginia Tech, 2004-12-15)
    UHPC (ultra-high performance concrete) is a relatively new type of concrete that exhibits mechanical properties that are far superior to those of conventional concrete and in some cases rival those of steel. The main characteristics that distinguish UHPC from conventional reinforced concrete are the improved compressive strength, the tensile strength, the addition of steel fibers, and the resistance to corrosion and degradation. The mechanical properties of UHPC allow for smaller, thinner, lighter sections to be designed while strength is maintained or improved. The use of UHPC has been limited to a few structural applications due to the high cost of the materials and the lack of established design guidelines. A proposed material model based on material and finite element models has served as the foundation of this research effort. The model was used to minimize the dimension of an optimum section in order to limit the material usage and maximize the performance. In the model, the top flange served as the riding surface and contained no reinforcing steel to resist shear. The lack of steel reinforcement allowed for the possibility of a punching shear failure to occur from the application of a point load such as a wheel tire patch load. The model and optimized section served as the foundation for this research, the characterization of punching shear capacity of thin UHPC plates. A total of 12 UHPC slabs were tested to failure to determine the boundary between a flexural failure and a punching shear failure. The variables considered were the slab thickness and loading plate dimensions. The results of the testing were compared to existing models for punching shears and other failure modes, with varying success. The test results aided in the development of a design equation for the prediction of punching shear in UHPC slabs. After evaluation of the test results, recommendations are made as to which model predicts the punching shear capacity of UHPC slabs and the minimum slab thickness required to prevent a punching shear failure.
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    Lateral Load Distribution and Deck Design Recommendations for the Sandwich Plate System (SPS) in Bridge Applications
    Harris, Devin K. (Virginia Tech, 2007-10-29)
    The deterioration of the nation's civil infrastructure has prompted the investigation of numerous solutions to offset the problem. Some of these solutions have come in the form of innovative materials for new construction, whereas others have considered rehabilitation techniques for repairing existing infrastructure. A relatively new system that appears capable of encompassing both of these solution methodologies is the Sandwich Plate System (SPS), a composite bridge deck system that can be used in both new construction or for rehabilitation applications. SPS consists of steel face plates bonded to a rigid polyurethane core; a typical bridge application utilizes SPS primarily as a bridge deck acting compositely with conventional support girders. As a result of this technology being relatively new to the bridge market, design methods have yet to be established. This research aims to close this gap by investigating some of the key design issues considered to be limiting factors in implementation of SPS. The key issues that will be studied include lateral load distribution, dynamic load allowance and deck design methodologies. With SPS being new to the market, there has only been a single bridge application, limiting the investigations of in-service behavior. The Shenley Bridge was tested under live load conditions to determine in-service behavior with an emphasis on lateral load distribution and dynamic load allowance. Both static and dynamic testing were conducted. Results from the testing allowed for the determination of lateral load distribution factors and dynamic load allowance of an in-service SPS bridge. These results also provided a means to validate a finite element modeling approach which would could as the foundation for the remaining investigations on lateral load distribution and dynamic load allowance. The limited population of SPS bridges required the use of analytical methods of analysis for this study. These analytical models included finite element models and a stiffened plate model. The models were intended to be simple, but capable of predicting global response such as lateral load distribution and dynamic load allowance. The finite element models are shown to provide accurate predictions of the global response, but the stiffened plate approach was not as accurate. A parametric investigation, using the finite element models, was initiated to determine if the lateral load distribution characteristics and vibration response of SPS varied significantly from conventional systems. Results from this study suggest that the behavior of SPS does differ somewhat from conventional systems, but the response can be accommodated with current AASHTO LRFD bridge design provisions as a result of their conservativeness. In addition to characterizing global response, a deck design approach was developed. In this approach the SPS deck was represented as a plate structure, which allowed for the consideration of the key design limit states within the AASHTO LRFD specification. Based on the plate analyses, it was concluded that the design of SPS decks is stiffness-controlled as limited by the AASHTO LRFD specification deflection limits for lightweight metal decks. These limits allowed for the development of a method for sizing SPS decks to satisfy stiffness requirements.
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    Use of a Sandwich Plate System in a Virginia Bridge
    Cousins, Thomas E.; Murray, Thomas M.; Harris, Devin K. (Virginia Center for Transportation Innovation and Research, 2009-05-01)
    The deterioration of the nation's civil infrastructure has prompted the investigation of numerous solutions to the problem. Some of these solutions have come in the form of innovative materials for new construction, whereas others have considered rehabilitation techniques for repairing existing infrastructure. A relatively new system that appears capable of encompassing both of these solution methodologies is the sandwich plate system (SPS), a composite bridge deck system that can be used in both new construction or for rehabilitation applications. SPS consists of steel face plates bonded to a rigid polyurethane core; a typical bridge application utilizes SPS primarily as a bridge deck acting compositely with conventional support girders. As a result of this technology being relatively new to the bridge market, design methods have yet to be established. This research aims to close this gap by investigating some of the key design issues considered to be limiting factors in implementation of SPS. The key issues that will be studied include lateral load distribution, dynamic load allowance, and deck design methodologies. With SPS being new to the market, there has been only one bridge application, limiting the investigations of in-service behavior. The Shenley Bridge, located near Quebec, Canada, was tested under live load conditions to determine in-service behavior with an emphasis on lateral load distribution and dynamic load allowance. Both static and dynamic testing was conducted. Results from the testing allowed for the determination of lateral load distribution factors and dynamic load allowance of an in-service SPS bridge. Results from this study suggest that the behavior of an SPS does differ somewhat from conventional systems, but the response can be accommodated with current AASHTO Load and Resistance Factor Design (LRFD) provisions as a result of their conservativeness. In addition to characterizing global response, a deck design approach was developed in this research project. In this approach, the SPS deck was represented as a plate structure, which allowed for the consideration of the key design limit states within the AASHTO LRFD specification. Based on the plate analyses, it was concluded that the design of SPS decks is stiffness-controlled as limited by the AASHTO LRFD specification deflection limits for lightweight metal decks. These limits allowed for the development of a method for sizing SPS decks to satisfy stiffness requirements