The inverted T-beam bridge system provides an accelerated bridge construction alternative for short-to-medium-span bridges. The system consists of adjacent precast inverted T-beams finished with a cast-in-place concrete topping. The system offers enhanced performance against reflective cracking, and reduces the likelihood of cracking due to time dependent effects. The effects of transverse bending due to concentrated wheel loads are investigated with respect to reflective cracking. Transverse bending moment are quantified and compared to transverse moment capacities provided by a combination of various cross-sectional shapes and transverse connections. A design methodology for transverse bending is suggested. Tensile stresses created due to time dependent and temperature effects are quantified at the cross-sectional and structure level and strategies for how to alleviate these tensile stresses are proposed. Because differential shrinkage is believed to be one of the causes of deck cracking in composite bridges, a study on shrinkage and creep properties of seven deck mixes is presented with the goal of identifying a mix whose long terms properties reduce the likelihood of deck cracking. The effects of differential shrinkage at a cross-sectional level are numerically demonstrated for a variety of composite bridge systems and the resistance of the inverted T-beam system against time dependent effects is highlighted. End stresses in the end zones of such a uniquely shaped precast element are investigated analytically in the vertical and horizontal planes. Existing design methods are evaluated and strut-and-tie models, calibrated to match the results of 3-D finite element analyses, are proposed as alternatives to existing methods to aid designers in sizing reinforcing in the end zones. Composite action between the precast beam and the cast-in-place topping is examined via a full scale test and the necessity of extended stirrups is explored. It is concluded that because of the large contact surface between the precast and cast-in-place elements, cohesion alone appears to provide the necessary horizontal shear strength to ensure full composite action. Live load distribution factors are quantified analytically and by performing four live loads tests. It is concluded that AASHTO's method for cast-in-place slab span bridges can be conservatively used in design. / Ph. D.

The Hampton Roads Bridge-Tunnel is one of the oldest prestressed concrete structures in the United States. The 3.5 mile long twin structure includes the world's first underwater tunnel between two man-made islands. Throughout its 60 years in service, the harsh environment along the Virginia coast has taken its toll on the main load carrying girders. Concrete spalling has exposed prestressing strands within the girders allowing corrosion to spread. Some of the more damaged girders have prestressing strands that have completely severed due to the extensive corrosion. The deterioration has caused select girders to fail the necessary load ratings. The structure acts as an evacuation route for the coast and is a main link for the local Norfolk Naval Base and surrounding industry. Because of these constraints, load posting is not a viable option. Live load testing of five spans was performed to investigate the behavior of the damaged spans. Innovative techniques were used during the load test including a wireless system to measure strains. Two different deflection systems were implemented on the spans, which were located about one mile offshore. The deflection data was later compared head to head. From the load test results, live load distribution factors were developed for both damaged and undamaged girders. The data was also used by the local Department of Transportation to validate computer models in an effort to help pass the load rating. Overall, this research was at the forefront of the residual strength of prestressed concrete girders and the testing of in-service bridges. / Master of Science

Accelerated Bridge Construction (ABC) has gained substantial popularity in new bridge construction and bridge deck replacement because it offers innovative construction techniques that result in time and cost savings when compared to traditional bridge construction practice. One technology commonly implemented in ABC to effectively execute its projects is the use of prefabricated bridge components (precast/prestressed bridge components). Precast/prestressed bridge components are fabricated offsite or near the site and then connected on-site using small volume closure pour connections. Diaphragms are also commonly used to strengthen the connection between certain prefabricated components used in ABC, such as beam elements. Bridges containing closure pour connections and diaphragms can be designed using AASHTO LRFD live-load distribution factor formulas under the condition that the bridge must be sufficiently connected. However, these formulas were developed using analytical models that did not account for the effects of closure pours and diaphragms on live-load distribution. This research study investigates live-load distribution characteristics of precast/prestressed concrete bridges with closure pour connections and diaphragms. The investigation was conducted using finite element bridge models with closure pour joints that were calibrated using experimental data and different configuration of diaphragms. The concrete material used for the closure pour connections was developed as part of a larger project intended to develop high early-strength concrete mixtures that specifically reach strength in only 12 hours, a critical requirement for ABC projects.