Editorial: Design and Control of Adaptive Civil Structures

Abstract

The environmental impact of buildings and civil infrastructure has become an important topic owing to significant non-renewable material use and the greenhouse gas emissions (GHG) that are required for sourcing, extraction, component manufacturing, transport, fabrication and operation. This Research Topic investigates new design strategies, control methods and applications for structures that adapt to loading events and other environmental actions through sensing and actuation. Actuation is most often implemented at the component scale. Strategic integration of active components enables modification of structural behavior under loading to fulfill control objectives. When included during design, adaptation enables a significant improvement in performance because the structure can sense and react to change of external stimuli and thus it can operate optimally under different conditions. Adaptation is carried out in various ways. For example, the inherently adaptive features of natureinspired compound elements are integrated into structures to reduce the response under seismic excitations and to mitigate the onset of instability in long-span structures (Chenaghlou et al.). Variable stiffness and damping properties of components made of viscoelastic material (e.g., shape memory polymers) have been investigated in the form of structural joints for vibration control. Actuation through thermal energy causes a significant stiffness reduction and a parallel increase of damping which results in the shift of the structure natural frequencies and an increase in damping ratios. This semi-active control strategy is effective for multi-story buildings and bridges under various excitations such as pedestrian/vehicular traffic and earthquakes (Wang et al.). In Kelleter et al. numerical and experimental studies are carried out on concrete beams equipped with multiple disc-shaped fluidic actuators. Controlled expansion of the fluidic actuators enables the reduction of bending-induced stress and compensation of displacements. Adaptation has been investigated to design multifunctional façade components. In Neuhaus et al. experimental studies have been carried out on the integration of ionic electroactive polymer actuators (IEPA) in adaptive membrane building skins. Actuation of small apertures provides ventilation control and humidity regulation. At the same time, the embedded devices work as sensors for load monitoring. Experimental studies show the potential and limitations of IEPA for adaptive building skins. Integration of linear actuators into truss and frame structures enables the implementation of many control strategies. Generally, controlled length changes of the actuators allow for the internal force flow and the structural shape to be manipulated to fulfill a control objective. In Cai et al. this strategy has been employed for shape control as well as locomotion of tensegrity structures. A formulation based on genetic algorithms and dynamic relaxation is developed to determine optimal control commands for shape control of a double-layered tri-prism tensegrity structure, as well as optimal gaits andmotion paths of a sixstrut locomotive tensegrity structure. Edited and reviewed by: Branko Glisic, Princeton University, United States