GALCIT Colloquium

Designing structures with minimal environmental impact is now a serious concern in the construction sector. Active control has been used in civil engineering for a variety of purposes. The most widespread application so far has been in vibration control. The potential of using adaptation to save material mass has been investigated by some but whether the energy saved by using less material makes up the energy consumed through control and actuation is a question that has so far received little attention.

Senatore et al. formulated a new methodology to design minimum energy adaptive structures [1, 2]. This design method synthesises structural configurations that are optimum hybrids between a passive and a fully active structure to minimise the structure whole-life energy comprising an embodied part in the material and an operational part for adaptation to loading. Instead of using more material to cope with the effect of loads, strategically located active elements redirect the internal load path to homogenise the stresses and change the shape of the structure to keep deflections within required limits. To ensure the embodied energy saved this way is not used up to by actuation, the adaptive solution is designed to cope with ordinary loading events using only passive load bearing capacity while relying on active control to deal with larger events that have a smaller probability of occurrence. Several configurations have been studied ranging from a catenary arch bridge to a tower building supported by an exoskeleton structure [3]. The research to date has demonstrated that up to 70% reduction in whole-life energy is achievable for slender structures [4]. Recent work has investigated the efficacy of structural adaptation through large shape changes [5] as well as the use of materials with variable stiffness properties [6]. When large shape changes are employed, the structure is designed to 'morph' into optimal shapes as the load changes. In addition, large shape changes can be employed to change the structure dynamic characteristics to reduce the response in case of dangerous resonance conditions. Simulations have shown that there is potential to further reduce the whole-life energy with respect to adaptive structures limited to small shape changes as well as to optimised passive structures [7].

A large-scale prototype has been successfully tested validating key assumptions and numerical predictions. The structure, a slender 6m (length) x 0.8m (width) x 0.16m (depth) (37.5:1 span to depth) cantilevered truss, is 80% lighter than an equivalent passive one because it can change its shape in real-time to maintain serviceability conditions showing zero deflection under loading thus achieving an apparent infinite stiffness [8]. This prototype was exhibited at various key institutions amongst with University College London, the International Association for Shell and Spatial Structures symposium (IASS) and a well-known gallery space called "The Building Centre" situated in central London [9].

References

[1] G. Senatore, P. Duffour, S. Hanna, F. Labbe and P. Winslow, "Adaptive Structures for Whole Life Energy Savings," International Association for Shell and Spatial Structures (IASS), vol. 52, no. 4 December n. 170, pp. 233 - 240, 2011.

[2] G. Senatore, P. Duffour, P. Winslow, S. Hanna and C. Wise, "Designing adaptive structures for whole life energy savings," in Research and Applications in Structural Engineering, Mechanics & Computation: Proceedings of the Fifth International Conference on Structural Engineering, Mechanics & Computation, Cape Town, 2013.

[3] G. Senatore, P. Duffour and P. Winslow, "Energy and Cost Analysis of Adaptive Structures: Case Studies," Journal of Structural Engineering (ASCE), vol. 144, no. 8, p. 04018107, 2018.

[4] G. Senatore, P. Duffour and P. Winslow, "Exploring the Application Domain of Adaptive Structures," Engineering Structures, vol. 167, pp. 608-628, 2018.

[5] A. Reksowardojo, G. Senatore and I. F. C. Smith, "Actuator layout optimization for adaptive structures performing large shape changes," Lecture Notes in Computer Science, vol. 10864, 2018.

[6] G. Senatore, Q. Wang, H. Bier and P. Teuffel, "The Use of Variable Stiffness Joints in Adaptive Structures," in International Association for Shells and Spatial Structures, Hamburg, 2017.

[7] A. Reksowardojo, G. Senatore and I. F. C. Smith, "A new method to design structures that adapt to loads via large shape changes," in International Association for Shell and Spatial Structures (IASS), Boston, 2018.

[8] G. Senatore, P. Duffour, P. Winslow and C. Wise, "Shape Control and Whole-Life Energy Assessment of an "Infinitely Stiff" Prototype Adaptive Structure," Smart Materials and Structures, vol. 27, no. 1, p. 015022, 2018.

[9] G. Senatore, "Gennaro Senatore Exhibitions," 2018. [Online]. Available: http://www.gennarosenatore.com/exhibitions/.