Proceedings Article | 30 March 2009
KEYWORDS: Shape memory alloys, Actuators, Control systems, Smart structures, Earthquakes, Error analysis, Sensors, Quantum efficiency, Differential equations, Telecommunications
Elevated civil structure systems, such as communication towers and water tanks, are prone to higher mode vibration and
earthquake induced damages. To mitigate damages, however, the structures are retrofitted with conventional (e.g. steel
casing) and/or emerging techniques (e.g. smart structures). Smart structure entails integration of system behavior, control
design and actuators. In this paper, utility of smart structures is illustrated through an elevated water tank concrete
column. The concrete column is modeled as a continuous system, using the Lagrangian formulation, and linear quadratic
regulator (LQR) is used for the control system, and shape memory alloy (SMA) for actuation. The water tank is excited
with the 1940 El-Centro earthquake record. A sensitivity analysis is performed on the controller error and penalizing
constants, as well as actuator location and angle of the connection. The four control variables that can be analyzed for
the controller are: Rr, Qr, Re, and Qe, which are the control penalty, error penalty, measurement noise and process noise,
respectively. The connection height on the beam and angle of the actuator is also analyzed for optimal performance.
From the sensitivity analysis, the most efficient controller configuration is identified for further analysis of the structure.
Optimal actuator configuration can be found based on the reduction of displacement versus the amount of energy used. It
has been shown that using the SMA, the seismic demand on the concrete column is reduced using the SMA.
