A methodology for transferring principles of plant movements to elastic systems in architecture

Highlights

• Plant movements.

• Kinetic structures.

• Biomimetics.

• Facade shading.

• Compliant mechanisms.

Abstract

In architecture, kinetic structures enable buildings to react specifically to internal and external stimuli through spatial adjustments. These mechanical devices come in all shapes and sizes and are traditionally conceptualized as uniform and compatible modules. Typically, these systems gain their adjustability by connecting rigid elements with highly strained hinges. Though this construction principle may be generally beneficial, for architectural applications that increasingly demand custom-made solutions, it has some major drawbacks. Adaptation to irregular geometries, for example, can only be achieved with additional mechanical complexity, which makes these devices often very expensive, prone to failure, and maintenance-intensive.

Searching for a promising alternative to the still persisting paradigm of rigid-body mechanics, the authors found inspiration in flexible and elastic plant movements. In this paper, they will showcase how today’s computational modeling and simulation techniques can help to reveal motion principles in plants and to integrate the underlying mechanisms in flexible kinetic structures. By using three case studies, the authors will present key motion principles and discuss their scaling, distortion, and optimization. Finally, the acquired knowledge on bio-inspired kinetic structures will be applied to a representative application in architecture, in this case as flexible shading devices for double curved facades.

Introduction

Contrary to the widespread notion that architecture focuses only on the planning of rigid and immovable structures, the increasing use of kinetic structures in our built environment proves that the border between building and machine has already been crossed. A closer look at how buildings are manufactured, constructed, and operated reveals that today’s living spaces have a considerable amount of moving parts and helpful devices that serve a large number of different tasks. Typically, these are mechanical systems that are implemented whenever there is a need for adaptation to internal or external factors through means of spatial adjustments. Once an actuating force is provided, they transform energy into movements that open, close, release, stop, direct, regulate, accommodate, counteract, control or fulfill many other functions. Examples range from simple small-scale applications like valves and flaps to medium-scale applications like doors, windows, blinds, louvers, and shutters to more complex large-scale applications like adaptable facades, retractable roofs, or folding bridges.

Similar to other areas in engineering, kinetic structures in architecture are usually based on the basic construction principles of rigid body mechanics. For design, one can therefore draw from the same engineering knowledge, scientific theories, and wealth of experience that has already provided the basis for many technical achievements. However, there are some profound differences between kinetic structures in industrial machinery and architecture  [1]. Movable structures in architecture are usually produced in small quantities or uniquely designed and manufactured for every application anew. Furthermore, while mechanical devices in the automotive or aviation industry constantly evolve due to extensive test runs and prototypes of various scales, these custom-made architectural devices are already the final product and often have to function at the first attempt. All of these aspects sum up and cause inevitably high planning and acquisition costs. Besides these disadvantages, kinetic structures in architecture are confronted with some particular challenges, which not easily align with the fundamental construction principles normally used in machine design  [1]. The traditional design approach prioritizes uniformity, regularity, and compatibility over individuality and adaptability. As a result, mechanical devices are usually conceptualized as mono-functional and standardized modules whose mechanics conform to a grid of orthogonal axes. A mechanical system like this, however, entails many limitations and is difficult to be applied in other than planar and parallel configurations. Here, adaptation can only be achieved at the expense of additional mechanical complexity, which results in heavy and maintenance-intensive structures. In summary, it can be said that the traditional approach of designing kinetic structures has created some hindering inertia that is difficult to reconcile with the increasing demand for individual technical solutions, as they are particularly sought after in architectural devices.