Description of the research
The aim of deployable structures for shading applications is to reduce the energy consumption of buildings by adapting their form and orientation to regulate the heat gains. The developing of elastic deformation patterns with large displacements and the use of responsive materials for actuation can outperform classical manual and motorised systems (venetian blinds, planar slats, screen blinds, louvers and fins). Indeed, a limited number of pivots reduces the maintenance costs, and complex elastic deformations can meet the shading requirements for various sun positions and facade orientations.
(Charpentier 2014) tried to used bi metallic systems to modify the shading actively. (Charpentier 2015) build and analysed a structure in CFRP bio inspired. (Adriaenssens 2014) proposed multi-dimensional optimisation according to the structural efficiency and the shading potential. The active part can be for instance a shape memory alloy element (Hannequart 2017). Kinematic strategies in plants and engineering have been compared (Charpentier 2017).
- Deployable structures
- Active Bending
The Potential of Shape Memory Alloys in Deployable Systems – a Design and Experimental Approach – P. Hannequart et al. (2017)
Hannequart P., Peigney M., Caron J-F., Baverel O., Viglino E.
This study focuses on deployable systems actuated by shape memory alloys in the perspective of designing adaptive sun shading devices for building facades. We first set the context of smart materials for adaptive facades and underline the remarkable characteristics of shape memory alloys for mechanical actuation purposes. After outlining the constraints on the integration of this material into deployable structures, we introduce three different prototypes actuated by shape memory alloy wires. They have been fabricated and tests have been carried out on two of them. Finally, we present some perspectives on the use of these actuators for solar shading systems in façade engineering
Kinematic amplification strategies in plants and engineering – V. Charpentier, P. Hannequart et al. (2017)
Charpentier V., Hannequart P., Adriaenssens S., Baverel O., Viglino E. and Eisenman S.
While plants are primarily sessile at the organismal level, they do exhibit a vast array of movements at the organ or sub-organ level. These movements can occur for reasons as diverse as seed dispersal, nutrition, protection or pollination. Their advanced mechanisms generate a myriad of movement typologies, many of which are not fully understood. In recent years, there has been a renewal of interest in understanding the mechanical behavior of plants from an engineering perspective, with an interest in developing novel applications by up-sizing these mechanisms from the micro- to the macro-scale. This literature review identifies the main strategies used by plants to create and amplify movements and anatomize the most recent mechanical understanding of compliant engineering mechanics.
The paper ultimately demonstrates that plant movements, rooted in compliance and multi-functionality, can effectively inspire better kinematic/adaptive structures and materials. In plants, the actuators and the deployment structures are fused into a single system. The understanding of those natural movements therefore starts with an exploration of mechanisms at the origins of movements. Plant movements, whether slow or fast, active or passive, reversible or irreversible, are presented and detailed for their mechanical significance. With a focus on displacement amplification, the most recent promising strategies for actuation and adaptive systems are examined with respect to the mechanical principles of shape morphing plant tissues.
Large displacements and the stiffness of a flexible shell – V. Charpentier et al. (2015)
V. Charpentier, S. Adriaenssens, O. Baverel
The design of static thin shell structures can be carried out using analytical and numerical approaches. Recently, thin shells have been studied for their flexibility, which can be beneficial for adaptive systems. However flexible systems involve large displacements and precise kinematics. The analysis of flexible shell systems is challenging due to the nonlinearities induced by these large displacements. This study addresses the nonlinear behaviour and stress-stiffening effects caused by large displacements in a 0.80 m-long carbon fibre reinforced plastic shell consisting of two monolithically connected lobes. The structural behaviour of this system is investigated both numerically and experimentally. Following the analysis framework, the non-linear effects of the large displacements on the shell stiffness are numerically determined using eigenvalue analysis and the displacement response to external loading on deformed shell configurations. The numerical displacement results are compared with results obtained in the experimental study. In conclusion, our study shows that the stiffness of the shell system under study increases 113% during deformation. More precisely, we establish that this change in stiffness is governed by the presence of tensile stresses in the shell surface due to deployment rather than by the change of the system’s geometry.
International Journal of Space Structures
Dialectic Form Finding of Passive and Adaptive Shading Enclosures – S. Adriaenssens et al. (2014)
S. Adriaenssens, L. Rhode-Barbarigos, A. Kilian, O. Baverel, V. Charpentier, M. Horner
Form finding describes the process of finding a stable equilibrium shape for a system under a specific set of loads, for a set of boundary conditions and starting from an arbitrary initial geometry. However, form finding does not traditionally involve performance constraints such as energy-related criteria. Dialectic form finding is an extension of the process integrating energy-related design aspects. In this paper, dialectic form finding is employed as an approach for designing high performance architectural systems, driven by solar radiation control and structural efficiency. Two applications of dialectic form found shading enclosure structures, a passive and an active one, are presented. The first application example is a site-specific outdoor shading structure. The structure is based on a louver system designed to provide protection from ultraviolet radiation over a pre-defined target only when required, promoting natural lighting and ventilation. The second application example is a shape-shifting modular facade system that adapts its opacity in response to environmental fluctuations. The system can thus improve the environmental performance of a building. Moreover, the system explores elastic deformations for shape changes, reducing actuation requirements. These examples highlight the potential of the dialectic form-finding strategy for the design of high performance architectural integrated structures.
Modeling the mechanical behavior of complex shaped bimetallic elements – V. Charpentier et al. (2014)
V. Charpentier, L. Rhode-Barbarigos, S. Adriaenssens and O. Baverel
Elements composed of bimetallic materials have been around for decades providing actuation through thermal elastic deformations in devices such as thermostats (e.g. domestic appliances), compensation for temperature changes in clock mechanisms as well as electrical circuit breakers. However, recent architectural projects such as “Bloom” by Doris K. Sung (2011) have extended their use in large-scale applications and highlighted their potential as actuation devices in adaptive structures. For the implementation of bimetallic elements in large-scale and complex-shaped implementations, a combination of existing theory, experimental testing and numerical modeling is required. This paper focuses on modeling the behavior of bimetallic elements with complex shapes. Three bimetallic elements selected for their anticipated deformed shapes and potential architectural implementations are investigated numerically and experimentally. Through a parametric study, the geometry of the elements is found to significantly affect their behavior. Geometry can be thus effectively used to trigger large deformations in bimetallic elements. However, for complex shaped elements the influence of geometrical parameters is not always easy to predict. This study extends current knowledge on bimetallic elements for more complex shapes providing support for their implementation in novel adaptive architectural applications.
CST2014: The Twelfth International
Conference on Computational Structures
Technology Naples, Italy
Prototype of a shading device actuated by shape memory alloy wires, realized for the Design Modelling Symposium (Versailles, September 2017). See (Hannequart 2017). Photo credit : Ioan Levi