Prestress in Nature and Technics
Licentiatavhandling, 2019
The thesis begins with a discussion about central concepts such as stress and stiffness. Stiffness can be understood as the sum of elastic stiffness and geometric stiffness and the latter is differently influenced by the presence of tensile or compressive stresses. Only structures that are statically indeterminate are possible to prestress so that the stress pattern is affected. The terms externally-equilibrated and auto-equilibrated prestressed structures are introduced.
The design of load-bearing structures for architecture requires a collaboration between architects and engineers and the conditions for a successful collaboration is reflected upon. Prominent design cultures are highlighted and the one this research is linked to is described.
A collection of historic and contemporary examples of prestressed structures is presented. The focus is architectural applications but examples from other realms are also included. From this collection, a framework for prestressed structures is proposed and discussed which considers five perspectives. The first explores the historical knowledge development. The second is devoted to structural mechanical modes of actions where material behaviour, member actions and structural systems are discussed. The third highlights computational strategies and those appropriate for early stage design are distinguished from those suitable for late stage verification. The fourth perspective seeks to establish objectives for why prestress is used. The fifth perspective leads to suggestions for strategies for how the prestress is achieved.
Three papers are included. Paper A presents a numerical method for the form finding of prestressed gridshells consisting of both compressed and tensioned members. Paper B describes a structural design process where methods usually applied by architects are used by structural engineers. The work resulted in the construction of a temporary pavilion consisting of a post-tensioned wooden gridshell called the Wood Fusion Pavilion. Paper C explores under what conditions an unloaded shell formed of a closed surface unattached to any supports can contain a state of membrane stress which can be induced by prestressing. It is concluded that a torus can be prestressed, but there must almost certainly be more to explore.
Geometrical stiffness
Prestress
Form finding
Architecture
Structural design
Stress pattern
Engineering
Conceptual design
Författare
Alexander Sehlström
Chalmers, Arkitektur och samhällsbyggnadsteknik, Arkitekturens teori och metod
Sehlström, A., Isaksson, J., Skeppstedt, M., Lund, M., Ander, M., Gustafsson, J., Williams, C. J. K., Olsson, K-G. Embracing design methods from architects for conceptual design of structures
Unloaded prestressed shell formed from a closed surface unattached to any supports
Form and Force - IASS Symposium 2019 and Structural Membranes 2019,;Vol. 2019(2019)p. 167-174
Paper i proceeding
On multi-objective topology optimization and tracing of Pareto-optimal structures
Övrigt konferensbidrag
The use of virtual work for the formfinding of fabric, shell and gridshell structures
Proceedings of the Advances in Architectural Geometry conference 2018,;(2018)p. 286-315
Paper i proceeding
Moving Mesh and Image Registration in FEniCS
Proceedings of 30th Nordic Seminar on Computational Mechanics – NSCM30,;(2017)p. 180-183
Övrigt konferensbidrag
Ämneskategorier
Arkitekturteknik
Arkitektur
Geometri
Matematisk analys
Utgivare
Chalmers
SB-H4, Sven Hultins gata 6
Opponent: Adj. prof. Dr. Roberto Crocetti, KTH, Sweden