Dynamic behaviour and redundancy of adaptive truss structures

This paper presents the work about research concerning structural optimisation with the use of adaptability to create structures that adapt to different environmental conditions. Using flexible structures inspired by nature, in combination with active control of structures (helping the structure when needed) will result in minimal material use and will contribute to an enriched engineering and architecture. The current status is that in general buildings are build unsustainable and inefficient. Stiff and static objects are built with a lot of materials while the external environment acting on it is highly dynamic and changes in time and loading type, -level and -location. Also structures are overdesigned for most of its working live because the dominating design parameter, which require the high amount of material, are very rare occurring. To improve this, buildings must be designed as adaptive structures, capable to react in a specific way to the environmental circumstances of that moment and in that way increase their efficiency. The generally used optimisation of static structures is therefore within this research extended by passive adaptive and active adaptive optimisation. Structures with higher deformation acceptance can react in a passive adaptable way which can reduce the load impact and the development of internal forces. With active adaptability the structural behaviour can be specifically controlled in a local or global way and further optimised. Combining the passive and active adaptability can result in an even further structural optimisation allowing the structure to act as a passive structure up to a certain threshold. Above this threshold the active control can be increased in relation to the impact of the varying external environment to control deformation and/or internal forces. The aim of one of the presented case studies to expose the main (dis-)advantages of an adaptive structure using a realistic case study. This case study is a high-rise (slender) office building where the stability in the slender direction is governed by six stability frames. Over two third of the total steel weight is localized in these stability frames, where the stiffness was a decisive issue. These facts make the stability frame in this building a potential ideal application for an adaptive structure. Global and local non-linear stability, safety issues and whole live energy use is studied and compared between passive and active structural behaviour. The study made clear that adaptive structures can have big advantages, and could develop towards a more logical way of designing and realizing a building in the future. For this research is needed. The second case study deals with the dynamic behaviour of adaptive truss structures: However, minimising the cross sectional areas also reduces the mass and stiffness of the adaptive structure. This makes adaptive structures more susceptible to resonance effects which can limit the material savings. In this research, the effect of the weight and stiffness reduction on resonance effects has been studied and confirmed. Multiple methods have been developed which employ adaptability to reduce resonance effects. The results show that dynamic active adaptability can be used to reduce resonance effects in adaptive structures further extending the limits on material savings.