Abstract:
Passive structures react effectively to only one dominant loading condition. Adaptive structures in contrast can deal with multiple loading conditions and unanticipated events at the same time. Truly adaptive civil structures do not exist. Concrete structures can be made adaptive through variable prestressing. Design concepts for an adaptive prestressed concrete girder are formulated in this research. Loading conditions and desired capabilities of the proposed system are defined. The system architecture is composed of sensors, a monitoring and control scheme, and actuators. These system components perform state identification, decision-making, and implementation of actions. Each system component is assigned requirements that are necessary to deal with all loading conditions in an appropriate way. Existing sensor technologies are explained and evaluated with respect to their capabilities to fulfill their functional requirements. A monitoring scheme is designed to interpret data assessed by the sensors for state identification. Adaptive control systems cannot be designed with conventional control algorithms. New control decision systems such as neural nets, expert systems, and fuzzy logic systems are needed for this task. Here, these systems are presented in general as forms of adaptive control. For each loading condition of the proposed system, a control strategy is developed. For the control of fluctuating live loads, a fuzzy logic based control scheme is proposed. Criteria for the selection of actuator technologies are given, and candidate actuator technologies are described and evaluated. Lastly, the problems associated with integrating the system components into a single system are discussed.
Description:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (leaves 93-96).
