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Abstract
AbstractThis paper presents numerical and experimental studies on semi‐active seismic response control of structures equipped with variable stiffness and damping structural joints. Such adaptive joints, which are comprised of a shape memory polymer (SMP) core reinforced by an SMP‐aramid composite skin, function as load‐transfer components as well as semi‐active control devices. The SMP core material can transition from a glassy to a rubbery state through thermal actuation resulting in a shift of the structural natural frequencies and a parallel increase of damping ratio, which enables a new semi‐active control strategy. Control performance has been evaluated on a three‐story frame equipped with 12 adaptive joints and subjected to seismic excitations. Full‐transient analysis has shown that when the joints are thermally actuated to the transition temperature (65°C), acceleration and base shear are reduced by up to 62% and 65%, respectively. Shake‐table tests have been carried out on a 1/10‐scale prototype, confirming that through thermal actuation of the adaptive joints the structural damping ratio increases from 2.6% to 11.3% and the first natural frequency shifts by up to 37%. As the structure becomes more flexible, an increase of displacements and interstory drift might occur. However, depending on the seismic excitation, top‐story acceleration and base shear are significantly reduced in the range 43%–50% and 35%–51%, respectively. These results confirm that semi‐active control through thermal actuation of variable stiffness and damping structural joints is effective to mitigate the structure response under seismic excitation.
Highlights
1.1 Previous workAdaptive structures are equipped with sensing, actuation, and control systems to operate optimally under changing load conditions and other environmental actions
This paper presents numerical and experimental studies on semi-active seismic response control of structures equipped with variable stiffness and damping structural joints
Shake-table tests have been carried out on a 1/10-scale prototype, confirming that through thermal actuation of the adaptive joints the structural damping ratio increases from 2.6% to 11.3% and the first natural frequency shifts by up to 37%
Summary
1.1 Previous workAdaptive structures are equipped with sensing, actuation, and control systems to operate optimally under changing load conditions and other environmental actions. Measurement and modeling inaccuracy might, in some cases, cause instability of the structure-control system.[10] Semi-active control systems are generally reliable and retain some of the capabilities of active systems while requiring a small external power source for operation.[2,11,12] Control forces are developed as a result of the structure motion through controlled changes of the mechanical properties of semi-active control devices such as magnetorheological and electrorheological dampers,[13,14] as well as variable stiffness and damping devices.[15,16] Hybrid control systems typically combine passive and active or semi-active control strategies and devices (e.g., hybrid mass dampers). While hybrid control systems are effective to control the dynamic response under a wide range of loading scenarios, such systems are generally complex and may require significant maintenance costs.[17]
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