The Characterization and Control of Shape Memory Alloy Cables for Reinforcement of Engineered Cementitious Composite Beams
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This thesis reports the innovative work of improving engineered cementitious composite (ECC) beams using superelastic Nitinol shape memory alloy (SMA) cables. Nitinol is the most popularly used SMA and superelastic Nitinol cable possesses many attractive features, such as large recoverable strain, large load bearing capacity, among others. To understand the characteristics of the Nitinol cable, a series of experiments were conducted to derive its key parameters, which was not provided by the manufacturer. A sliding mode based robust controller was designed and tested to ensure the accurate force control of the Nitinol cable during the process of post-tensioning of the ECC beam. In this research, the shape memory effect of the same superelastic Nitinol cable when its temperature was below its martensite finish temperature was used to post-tensioning the ECC beam with a pre-loaded force. Experiments demonstrated that the ECC reinforced with the superelastic Nitinol cable with a pre-loaded force greatly increases the load bearing and self-repairing capacities of the ECC beam without sacrificing its ductility.