McMahon, Joshua A (2016-12). Experimental Investigation of Steel Fiber Reinforced Concrete as Supplemental Reinforcement in Bridge Decks. Master's Thesis.
Thesis
Research on fiber reinforced concrete has been ongoing since the 1960's. The current state of knowledge of SFRC demonstrates the benefits of the fibers in regards to the ductility, energy dissipation, and strength improvements of the reinforced concrete matrix. However, further validation of SFRC as supplemental or alternative reinforcement needs to be conducted before bridge deck designs using SFRC may be utilized. The interaction between FRC and steel reinforcement needs to be identified as current practice in the United States and Canada require positive reinforcement as an anti-progressive collapse mechanism regardless of the reinforcement or concrete matrix detailing. Low dosages of fibers could also be used to satisfy service requirement while steel reinforcement satisfies the strength requirements. As a result, the behavior of a SFRC deck under service conditions must also be investigated. The lack of practical, large scale experiments and a simple and reliable method for accurately determining the tensile residual stress for SFRC has prevented the adoption of building codes regarding SFRC in the United States. This research identified the possible use of steel fiber reinforced concrete (SFRC) in bridge decks as supplemental reinforcement. A case study analysis was conducted to identify how the performance of SFRC was influenced by the bridge deck geometry, steel reinforcement ratio, and SFRC residual strength. The analysis shows that the addition of fibers permits a reduction of traditional steel reinforcement while achieving design requirements. Findings of the theoretical study was verified in an experimental parameter study of individual SFRC slab-strips subjected to four point bending tests. The slab-strips investigated the depth of the bridge deck, the ratio of steel reinforcement, and its location in the cross-section. The load-deformation and crack patterning of the slab-strips describe the strength and failure behavior of SFRC. A full-scale bridge deck was designed and tested using AASHTO LRFD design procedures and the results of the slab-strip tests. A yield line analysis was conducted on the bridge deck results to show the benefits of SFRC with respect to theoretical predictions. Based on the results of each phase of testing, design recommendations are provided to predict the capacity of SFRC slabs.
