South Africa: Design & Construction Criteria for Domes in Low-Cost Housing
Introduction:
This dissertation investigates the different design & construction considerations involved when building a masonry dome. A detailed shape investigation was undertaken in order to summarize the best-shaped dome structures. General recommendations are given for the shapes that produce the least tension and the most useable space. The effects of openings, temperature loading, and wind loading were considered and finite element analysis of the final structure was undertaken. It was found that regions of high tension exist around openings, especially under temperature loading, and materials suitable to resisting this tension were investigated (fiber plaster, chicken wire mesh, and wire wrapping around openings).
Aims of the Investigation:
The main objectives of this dissertation are:
To identify the optimal shaped dome structure that can be used in low cost housing
To investigate the important design criteria with regard to domes
To utilize affordable materials (compressed earth blocks) that can be acquired in remote areas
To investigate different methods of dome construction
To construct a durable, architecturally and structurally efficient low cost dome house
A Brief History of the Dome:
Domes have been used throughout the ages as a housing form, or an element of a housing form (roof structure). African and aboriginal societies built domes by planting branches in the ground and weaving the dome shape. The dome shape has also been used historically to span large distances, as reinforced concrete and steel have been relatively recent developments on the historical scale. The Moguls, Egyptians, Byzantines and Romans used domes and vaults extensively.
Fiber Reinforced Soil Crete Blocks for the Design & Construction of Low-Cost Housing:
This investigation focused on the production of fiber reinforced cement stabilized blocks. The objective was to study different types of soil, curing processes and reinforcements, in order to identify the most important parameters in the production of strong, durable blocks. The project was undertaken by the University of the Witwatersrand and the Lausanne Federal Institute of Technology (EPFL). This report was useful to this project as it provided design information about the Hydra Form earth block. Tests were performed to determine dry compressive strength, flexural strength, tensile strength and the modulus of elasticity of the blocks.
Domes in Low-Cost Housing:
This investigation involved the construction of a dome shaped low-cost house in a rural area close to Maputo, Mozambique. Figure 1.6 shows the final product of this investigation. The study sought to prove the viability of this type of structure for the use of low-cost housing. Furthermore, the study was aimed at achieving a self-construction solution, using local materials to construct the dome.
The Design & Construction Tlholego Eco-Village:
The Design & Construction Thholego Eco-Village is situated in the North West Province of South Africa. A masonry dome was built above a cylinder wall (to eaves height), and the structure was used as a kitchen for the local community. Cracking was also observed. Poor waterproofing, shrinkage and thermal cracking was postulated as the cause of cracking.
Architectural Considerations for Design & Construction:
This section deals with a few key architectural issues which need to be addressed when building any structure. The issues discussed can be summarized under the following headings:
• Shape
• Structural Strength
• Rain Penetration & Damp Proofing
• Thermal Performance
• Lighting
• Internal Arrangement of Walls
• Overall Aesthetics
Conclusion:
The objectives of this investigation were to identify the optimal shaped dome structure that can be used in low cost housing; to identify the important design & construction criteria with regard to masonry domes; to utilize affordable materials (compressed earth blocks) that can be acquired in remote areas in the design of the dome; to investigate different methods of dome construction and to construct a durable, architecturally and structurally efficient low cost dome home.