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 / The inverted T-beam bridge system is a new type of bridge system intended for use in short to medium length bridges. The system was discovered in France in 2004, where a similar type was being used. It was first modified slightly, and adopted in the in Minnesota. In 2012, the system was again modified to increase its strength and its construction speed, and was then adopted in Virginia. The modifications to the system in Virginia focused on the connections between the individual units making up the bridge, and the geometry of each of these units. The focus of this research was to quantify the long-term performance of two of the connection types currently used on bridges in Virginia. This was achieved by subjecting a test specimen to repeated loads in the laboratory at Virginia Tech. The loading used in the laboratory represented the conditions that a real bridge of this type would be subjected to. The research showed that the two connection types performed well under the repeated loading conditions. However, it was concluded that the concrete surfaces which are in contact with one another must be properly roughened, so that the system maintains its strength. The importance of this research is due to the fact that the large costs associated with maintaining the nation’s bridge infrastructure can be substantially reduced due to this system’s quick and simple construction. In addition to this, road users experience less disruption because of the shortened construction times.

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 Virginia Inverted T-Beam bridge system was initially designed to be more durable and economical than other types of bridges. The bridge is constructed by arranging prefabricated beams side-by-side across the span before placing fresh concrete overtop. In the most economical version of the system, the only connection between the beams is the newly placed concrete. For the beams and topping to act together, the bond between them must be strong. Roughening the surface of the prefabricated beams increases the strength of the bond, although different roughening patterns achieve different levels of strength. Past tests of the bridge system have utilized inadequate roughing patterns which lead to low bridge failure loads after many loading cycles. This low-cost configuration is currently only approved for use in low daily traffic areas. The goal of this research was to determine a roughening pattern that would result in a high bridge failure load which would allow the low-cost configuration to be approved for high daily traffic areas. Several roughening patterns were investigated and the patterns producing the highest shear strengths were determined. The best pattern was chosen to be used for the bridge configuration and a sub-section of the bridge was constructed. This specimen was subjected to a loading protocol that simulated the traffic that an actual bridge would be subjected to over its life span. The failure load was then measured and found to be high enough to warrant the use of the specific system in high daily traffic areas.

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