vadgama, Dom z worków [ Pobierz całość w formacie PDF ]
//-->Department of Architecture & Civil EngineeringA MATERIAL ANDSTRUCTURAL ANALYSISOF EARTHBAG HOUSINGStudent: Nikul VadgamaSupervisor: Dr. Andrew HeathMEng DissertationApril 2010AbstractThe use of earthbags as structural material for housing has grown in popularity over the pastdecade; however, research into its structural behaviour is limited. Current design relies onprevious experience or trial and error. If the use of earthbags as building material is to develop,an understanding into its material properties and structural behaviour is needed. By way ofempirical analysis this dissertation aims to investigate the material mechanics of sand filledearthbags and establish a set of material parameters which will aid the design of earthbagstructures.The dissertation is collaborative with Fielden Clegg Bradley Studios who plan to build earthbaghousing in Namibia. Test parameters for this dissertation have been chosen specifically to helpinform the project, which in turn provides a physical bearing to the experimental programme andanalysis.The behaviour of earthbags under uniaxial compression was investigated. The effect of materialfill level, stack height, addition of stabiliser and bag material on the compressive strength wereexplored. From testing it was concluded that earthbags are unlikely to fail due to compressionwithin a structure. Furthermore the current simplified theoretical model assuming a cross sectionwith lateral semi-circular profiles provides acceptably accurate estimations of the vertical loadcapacity of earthbags.Large scale direct shear box tests were performed to quantify the shear resistance betweenearthbags. Variations in bag material and the inclusion of barbwire were examined. A hessian onhessian interface provided the highest coefficient of friction. The inclusion of barbwire alsoimproved the coefficient of friction between the earthbags are provided an initial cohesion.Load testing on earthbag arches were performed to gain an understanding how the materialparameters affect the structural performance. The addition of 4% cement to the earthbags wasfound to increase the load capacity of the arch by 76% and alter the overall behaviour of the archto a linear elastic structure up to 6kN applied load. The behaviour of an unstabilised arch is non-linear, owing to the flexible nature of the bags. Premature shear failure of the earthbags was notexperienced therefore the addition of barbwire between bags did not affect the load capacity ofthe arch.This dissertation provides an insight into the material and structural behaviour of earthbags. Tofurther establish a set of structural parameters for design, research into the behaviour ofearthbags in defined structural systems should be undertaken.iAcknowledgementsThe author would like to acknowledge the invaluable support and guidance provided by Dr.Andrew Heath during the course of this dissertation, and throughout the author’s undergraduatedegree.Gratitude also extends to Will Bazeley, Neil Price, Brian Purnell, and Sophie Hayward for theirtime and expertise with laboratory experiments.Also thanks extend to Nicola du Pisanie for her enthusiasm and advice throughout thedissertation. For his assistance with laboratory experiments, organisation and motivational workethic the author thanks Ralph Pelly.Finally, to my family and friends for their support throughout.iiContentsAbstract .......................................................................................................................................................... iAcknowledgements ....................................................................................................................................... iiList of Figures ............................................................................................................................................... vList of Tables .............................................................................................................................................. viiList of Symbols and Abbreviations............................................................................................................. vii1Introduction ........................................................................................................................................... 11.11.21.323General Introduction ..................................................................................................................... 1Objective of Dissertation .............................................................................................................. 2Organisation of Dissertation ......................................................................................................... 2Namibia Project .................................................................................................................................... 3Literature Review.................................................................................................................................. 43.13.23.3Introduction to Literature Review ................................................................................................. 4Previous Research into Earthbags ................................................................................................. 4Summary of Literature Review ..................................................................................................... 94Theory ................................................................................................................................................. 114.14.24.2.14.2.24.2.34.34.4Initial Conditions and Assumptions ............................................................................................ 11Compressive Strength of Earthbags ............................................................................................ 11Assuming earthbag cross section as rectangular ................................................................. 12Assuming earthbag cross section with semi-circular lateral edges ..................................... 14Summary of theoretical compressive strength of earthbag ................................................. 16Shear Strength of Earthbags ........................................................................................................ 17Theoretical Earthbag Arch Mechanism ...................................................................................... 185Laboratory Testing .............................................................................................................................. 205.15.1.15.1.25.25.35.45.55.5.1Soil Analysis ............................................................................................................................... 20Sieve Test ............................................................................................................................ 20Shear Box Tests .................................................................................................................. 20Tensile Tests on Bag Material .................................................................................................... 20Compression Tests ...................................................................................................................... 20Shear Tests .................................................................................................................................. 22Arch Test..................................................................................................................................... 23Stabilised Arch Tests .......................................................................................................... 24iii6Results & Analysis .............................................................................................................................. 256.16.1.16.1.26.26.36.3.16.3.26.3.36.3.46.3.56.3.66.46.4.16.56.5.16.5.2Soil Analysis ............................................................................................................................... 25Sieve Tests .......................................................................................................................... 25Shear Box Tests .................................................................................................................. 25Tensile Test on Bag Material ...................................................................................................... 26Compression Tests ...................................................................................................................... 27Three earthbag stack ........................................................................................................... 27Five earthbag stack.............................................................................................................. 30Eight earthbag stack ............................................................................................................ 30Comparison between experimental results with theoretical predictions ............................. 33Sources of error in experimental and theoretical work ....................................................... 36Summary and conclusion of compression tests .................................................................. 37Shear Test of Earthbags .............................................................................................................. 38Shear resistance in earthbag structures ............................................................................... 41Arch Test..................................................................................................................................... 44Earthbag arches loaded at quarter span ............................................................................... 45Summary and conclusion of earthbag arch tests ................................................................. 487Conclusion .......................................................................................................................................... 497.1Future Work ................................................................................................................................ 50Bibliography ............................................................................................................................................... 51Appendix A ................................................................................................................................................. 53Appendix B ................................................................................................................................................. 54Appendix C ................................................................................................................................................. 55Appendix D ................................................................................................................................................. 59Appendix E ................................................................................................................................................. 60Appendices can be found in accompanying C.D.iv [ Pobierz całość w formacie PDF ]