Browsing by Subject "Concrete structures"
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Item Performance of fiber-reinforced plastic (FRP) wrapped reinforced concrete elements in a corrosive environment(2006-05) Karpate, Harshda Shriram; Fowler, David W.; Jirsa, J. O. (James Otis)Corrosion presents one of the greatest threats to the durability of reinforced concrete structures, yet it is also one of the least understood components of the design process for most engineers. The nation's infrastructure is rapidly deteriorating due to years of abuse and fatigue. Therefore, several economic and reliable solutions have been developed to repair the existing damage and extend the design life of structures at risk of corrosion. One popular method for protecting concrete structures from corrosion is the use of fiber-reinforced plastic (FRP) composite wraps. The premise is a simple one: placing an impermeable barrier around the surface of the concrete should prevent harmful substances such as chlorides from entering and corroding the imbedded reinforcing steel. However, little is known about the long-term effectiveness in preventing corrosion in reinforced concrete structures. The FRP wrap may in fact prevent the chlorides from passing through the concrete, however, the same principle might cause chlorides to be trapped beneath the surface and accelerate corrosion. In this study, the long-term behavior of laboratory specimens exposed to an aggressive chloride-rich environment were examined. This project was designed to develop a greater understanding of the long-term effects of FRP wrapping in preventing corrosion in reinforced concrete structures. Although TxDOT project 0_1774 involves both rectangular and cylindrical specimens, the focus of this thesis is on the specific impact of FRP wraps on partially wrapped versus unwrapped columns. The specimens included in this study are comprised of a wide range of construction parameters. However, despite the multitude of varying mix designs a noticeable trend has emerged as a result of this research.Item Seismic Fragility Analysis and Loss Estimation for Concrete Structures(2012-02-14) Bai, Jong WhaThe main objective of this study is to develop a methodology to assess seismic vulnerability of concrete structures and to estimate direct losses related to structural damage due to future seismic events. This dissertation contains several important components including development of more detailed demand models to enhance accuracy of fragility relationships and development of a damage assessment framework to account for uncertainties. This study focuses on concrete structures in the Mid-America region where a substantial seismic risk exists with potential high intensity earthquakes in this geographic region. The most common types of concrete structures in this area are identified based on the building inventory data and reinforced concrete (RC) frame buildings and tilt-up concrete buildings are selected as case study buildings for further analysis. Using synthetic ground motion records, the structural behavior of the representative case study buildings is analyzed through nonlinear time history analyses. The seismic performance of the case study buildings is evaluated to describe the structural behavior under ground motions. Using more detailed demand models and the corresponding capacity limits, analytical fragility curves are developed based on appropriate failure mechanisms for different structural parameters including different RC frame building heights and different aspect ratios for tilt-up concrete structures. A probabilistic methodology is used to estimate the seismic vulnerability of the case study buildings reflecting the uncertainties in the structural demand and capacity, analytical modeling, and the information used for structural loss estimation. To estimate structural losses, a set of damage states and the corresponding probabilistic framework to map the fragility and the damage state are proposed. Finally, scenario-based assessments are conducted to demonstrate the proposed methodology. Results show that the proposed methodology is successful to evaluate seismic vulnerability of concrete structures and effective in quantifying the uncertainties in the loss estimation process.