Structural Analysis of Geodesic

Domes

Marek+Kubik+report







Project plan

Introduction

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. The domes

had soil packed over them, a condition which was never anticipated in the original design.

The need for a method to model the structural response of the geodesic or “Pabal” dome

was highlighted by Vigyan Ashram, the Non Governmental Organisation (NGO) that

manufactures the domes; this dissertation describes the research into the Pabal dome and

the development of a bespoke finite element analysis (FEA) package capable of running

in Microsoft Excel.

Objectives

Vigyan Ashram locally produces the geodesic domes as do-it-yourself kits for the lowermiddle

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 associated

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 summarised 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 categorised 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 developed,

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.

Upon return of the draft report from the project supervisor, modifications would be

made and the final project submitted on the 29th of April. Additionally, a poster

design for display in the department would be produced and preparation for the

oral exams would occur in this period.


Download
*