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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

Across the State of Texas and many other areas of the world, relatively young concrete structures have developed signs of premature concrete deterioration. Large cracks form on the surface of the concrete due to expansive forces from alkali-silica reaction (ASR) and delayed-ettringite formation (DEF). The goal of this project is to assess the effect of ASR/DEF on the trapezoidal box beam bridges in the US 59 corridor and Katy Central Business District (CBD) HOV lanes in Houston, TX. Five dapped-end beams were rejected during the casting process and have been in storage at a local precast yard for nearly fifteen years. These beams have been subject to accelerated deterioration and represent the potential severity of the ongoing ASR/DEF distress within the dapped end regions of the in-service trapezoidal box beams. The results from five load tests, corresponding strut-and-tie models, and forensic investigation are used to provide insights into the relationship between the severity of the deterioration and the capacity margin. / text

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Adjacent precast, prestressed box beam bridges have a history of poor performance and have been observed to exhibit common types of deterioration including longitudinal cracking, concrete spalling, and deterioration of the concrete top flange. The nature of these types of deterioration leads to uncertainty of the extent and effect of deterioration on structural behavior. Due to limitations in previous research and understanding of the strength of deteriorated box beam bridges, conservative assumptions are being made for the assessment and load rating of these bridges. Furthermore, the design of new box beam bridges, which can offer an efficient and economical solution, is often discouraged due to poor past performance. Therefore, the objective of this research is to develop improved recommendations for the inspection, load rating, and design of adjacent box beam bridges. Through a series of bridge inspections, deteriorated box beams were identified and acquired for experimental testing. The extent of corrosion was determined through visual inspection, non-destructive evaluation, and destructive evaluation. Non-destructive tests (NDT) included the use of connectionless electrical pulse response analysis (CEPRA), ground penetrating radar (GPR), and half-cell potentials. The deteriorated capacity was determined through structural testing, and an analysis procedure was developed to estimate deteriorated behavior. A rehabilitation procedure was also developed to restore load transfer of adjacent beams in cases where shear key failures are suspected. Based on the understanding of deterioration developed through study of deteriorated adjacent box beam bridges, improved inspection and load rating procedure are provided along with design recommendations for the next generation of box beam bridges.