Optimization of dome housing in Sri Lanka

Abstract

The Solid House Foundation uses inflatable hemisperical formwork to build concrete dome dwellings. In this thesis a study is made of possible optimization of this building concept. Main occasion is the increasing price of rebar and the bad availability of rebar in most regions where the SHF is active. As SHF is now involved in a large housing project in Sri Lanka, a first focus is on this region. To have an idea of threads and opportunities in dome building a literature study was made on dome shapes in nature, domes in other cultures, the history of concrete shells built with inflatable formwork and of domes in general. As a result several form-related possibilities were identified that could reduce the tension stress in the shell and thus the amount of reinforcement needed. Also, research on alternative materials for dome building was done. This resulted in several options of which ferrocement was considered the most suitable. The latter from both a cost point of view as from the fact that there is a lot of experience with this easy applicable material in Asia. For the current design half of the material turns out to be used for the foundation of the dome. After some calculations could be concluded that this heavy foundation was required to anchor the uplifting forces of the inflatable formwork. Consequently research has been done on alternative anchorage of the form, resulting in ideas for formwork that does not need anchorage at all. The research phase was rounded off with a study of the climatic circumstances in Sri Lanka. Matching building responses to the climate were studied and applied on dome designs. The conclusions drawn from a structural analyses in the finite element program ANSYS have resulted in a proposal for alternative material use in combination with the currently applied formwork. A design for a ferrocement shell has been made and an experiment is carried out. However to improve issues such as the heavy foundation and the dependency on electricity, a different design of the formwork is required. Therefore possibilities for an alternative design of the formwork are studied and evaluated.