Structural Analysis of Geodesic Domes
This is an extensive document relating to the structural analysis of geodesic domes used in India. Its author, Marek Kubik submitted this paper as his final year project at Durham University School of Engineering.
The complete document (click here to download it in PDF format) demonstrates various techniques and approaches, a rare glimpse for most of us not accustomed to the details involved in such an analysis. Below you can read the paper’s abstract and summary.
Abstract
A project to house 40 families in the Maharashtra region of India which began in January 2005 was halted shortly after it commenced due to concerns over the loading applied to a series of geodesic domes which form a large portion of the whole complex. Vigyan Ashram, the organisation that manufactures the domes, issued a request for the development of an affordable computer program that would allow them to model the structural response of the domes. The ensuing research into the design of the geodesic domes and the development of a spreadsheet based finite element package are the subject of this dissertation.
Objectives
Vigyan Ashram locally produces the geodesic domes as do-it-yourself kits for the lower- middle class of both rural and urban populations. The original design was adopted in the aftermath of the 1993 Killari earthquake, aiming to provide durable, low cost housing capable of withstanding the earthquakes, rains and winds of India for those that lost their homes.
Of the 120 geodesic dome kits supplied to the Water Bank housing project, 40 were planned to be subterranean and were therefore affected. Vigyan Ashram, together with another NGO, engINdia, asked for research into the geodesic dome’s current incarnation to be carried out. The Water Bank project highlighted the need for a method of modelling the structural response of geodesic domes, as an assessment of the loading encountered by the domes would allow recommendations to be made as to how the design could be adapted to accommodate the expected loading.
Vigyan Ashram’s main desire was for a structural analysis package without the asso- ciated licensing costs, to allow their science and technology centre to assess the geodesic dome’s structural response in-house. This would provide significant long term benefits for Vigyan Ashram, removing the need for outsider aid with such design problems in the future. If appropriate, students at Vigyan Ashram would also use the developed method to further their understanding of structural behaviour.
It was hoped that a reliable method of analysis would increase the number of potential uses of the structure and hence its market demand, benefiting both the community and the business that manufactures the dome, which was founded and run by an ex-student of Vigyan Ashram.
The objectives of this project may be summarized as follows.
1. The development of a method of finite element analysis for geodesic dome structures
using Microsoft Excel 2003. The program needed to provide a user friendly format that gave the user the opportunity to define a geometry, select appropriate material properties and apply a variety of loading conditions. It was required to output information about nodal displacements and forces in the elements.
2. The assessment of the dome joints used in the structure to determine their design limits. Based on these findings, a relationship between material parameters and the ultimate failure strength of the connections was to be developed.
3. The development of an additional spreadsheet that would allow the user to calculate all the relevant dome fabrication details - how many different struts are required, how long they are, how many bolts are required for sufficient connection strength etc.
Project timeline
This project was to be carried out over a period of 28.5 weeks – from the end of September through to mid-May. A Gantt chart breakdown of the project plan may be found in Appendix A, with all the major project deadlines highlighted
Work was broadly categorized into three phases.
• Phase I: Initial research and planning; lasting from September through to January, culminating in the submission of the literature review. In this phase, background reading and discussion with Vigyan Ashram would lead to the development of a list of objectives and a project plan. Additionally, preparation work for the later tension testing work would be scheduled, including the submission of a risk assessment and the production of engineering drawings to fabricate the required dome joints.
• Phase II: Data collection; overlapping with Phase I, from December to the end of April. Here, experimental work would be carried out and the spreadsheets devel- oped, culminating in the submission of a draft version of the final report.
• Phase III: Project conclusions; from April until the concluding oral exam in May.
