Ductility and damage evaluation of post-tensioned concrete beams with hybird FRP tendon

FRP (fiber-reinforced-polymer) has been identified as an ideal candidate material of choice to reinforce the concrete structural elements due to its superior corrosion resistance as well as excellent specific strength in comparison to steel. However, the linear-elastic material property of FRP tendon may result in lack of structural ductility for concrete members. This research project concentrated on improving structural ductility of post-tensioned concrete elements by employing pseudo-plastic hybrid FRP tendons. To achieve this objective, a type of hybrid FRP rod with bilinear stress strain behavior was developed by combining carbon and glass fibers. Its mechanical characteristics of the rods were evaluated through tensile tests. The suitability of the core shell approach was verified for manufacturing of the hybrid rods enhanced ductility and strain capacity for the carbon-glass hybrid composite.; Overall experimental investigations and theoretical analysis in assessing the performance of post-tensioned concrete beams with the developed hybrid FRP tendon were performed. Experimental results indicated promising ductile characteristics for the hybrid carbon-glass FRP tendon materials. The ductility indices of the post tensioned beams were determined to be in the range of 2.5 to 3.3 for beams with hybrid FRP tendons.; The experimental program also included damage assessment of the developed hybrid FRP tendon by way of a single channel fiber optic acoustic emission (AE) sensor. The acoustic emission technique was employed for real-time determination of the progressive damage due to rupture of fibers. Moreover, the spectral energies of the frequency spectrum from the AE signals were employed for assessment of the state of damage in the rods. Spectral energies distinguish between the carbon and glass fiber ruptures. This differentiation of signals provides information about the condition and the state of health of the hybrid rod.; Using expansive cement as matrix, a new bond type of anchorage system for gripping the hybrid FRP tendons was also developed based on a continuation from an earlier study. This study includes works in understanding the mechanical behavior and for determining the development length of the anchorage. Methodologies were developed for the measurement of pressures generated by the expansive cement, and the strain distribution in the anchorage zone during loading of the tendon. These methodologies were employed for the determination of bond development length, bond strength, and the coefficient of friction between the anchorage and the mortar matrix in the anchorage system.