Thonstad, Travis ECalvi, Paolo MFarag, Benedikt Fadel2024-10-162024-10-162024-10-162024Farag_washington_0250O_27054.pdfhttps://hdl.handle.net/1773/52452Thesis (Master's)--University of Washington, 2024Macro-synthetic fibers are commonly added to concrete mixtures as secondary reinforce- ment to control temperature and shrinkage cracks in concrete flatwork. The fibers limit the width of cracks that develop in the cast concrete, improving durability and longevity. The fibers also improve the tensile behavior of the material. However, the contribution of macro- synthetic fibers towards the strength of structural elements is generally neglected. A re- cent experimental program tested twelve macro-synthetic fiber-reinforced concrete (PFRC) panels subjected to pure shear loading and explored the contribution of macro-synthetic fibers to shear strength when used in combination with conventional deformed bar shear reinforcement. The tests indicated that, for typical fiber contents (≤ 0.5% by volume), macro-synthetic fibers did not decrease the shear capacity of the panels but reduced crack widths at various load levels. The experimental program provided some evidence that macro-synthetic fibers are beneficial for shear loading but was limited in scope and in the levels of the experimental variables that could be tested.To further investigate the influence of macro-synthetic fibers on shear behavior, a para- metric study was performed using finite element models to extend the experimental results and explore combinations of parameters that were not tested experimentally. A modeling approach was calibrated using the experimental panel data, where a concrete tension soften- ing model was incorporated to capture the strength contribution of the fibers. The modeling approach was validated against a database of PFRC beams from the literature, which was compiled as part of this research. The modeling approach was then used to conduct a parametric study, exploring the monotonic pure shear strength of PFRC panels with over 250 combinations of fiber contents, transverse reinforcement ratios, and concrete compres- sive strengths. The results of the parametric study indicated that macro-synthetic fibers effectively reduced crack widths and enhanced shear strength, depending on the transverse reinforcement ratio and fiber content. Greater benefits were observed for lower transverse reinforcement ratios (≤ 0.25%) and higher fiber contents (> 1.0%), exhibiting slightly dif- ferent trends for the different concrete compressive strengths. The ability of existing empirical equations in model codes and in the literature to predict the shear strength of PFRC structural elements was also evaluated. Most current design codes neglect the contribution of macro-synthetic fibers to the shear strength of structural elements, which resulted in significant underestimation of shear strength. Several empirical equations from the literature provided more reasonable estimates of shear strength for both PFRC beams and panels and were used to propose a fiber-reinforcement term that would modify current code-based shear strength prediction equations. Recognizing the structural benefits of macro-synthetic fibers would increase their use and would lead to more durable and resilient reinforced concrete structures.application/pdfen-USnoneFiber-reinforced concreteMacro-synthetic fibersPolypropylene fibersShear strengthCivil engineeringCivil engineeringThesis