Investigating the Durability of Structures by Dana Saba Bachelor of Engineering, McGill University, Montréal, 2011 Submitted to the Department of Civil and Environmental Engineering in Partial Fulfillment of the Requirements for the Degree of Master of Engineering in Civil and Environmental Engineering at the Massachusetts Institute of Technology June 2013 © 2013 Massachusetts Institute of Technology. All rights reserved. Signature of Author: Department of Civil and Environmental Engineering May 10th, 2013 Certified by: Jerome J. Connor Professor of Civil and Environmental Engineering Thesis Supervisor Certified by: Rory Clune Massachusetts Institute of Technology Thesis Reader Accepted by: Heidi Nepf Chair, Departmental Committee for Graduate Students 2 Investigating the Durability of Structures by Dana Saba Submitted to the Department of Civil and Environmental Engineering in May 10, 2013, in Partial Fulfillment of the Requirements for the Degree of Master of Engineering in Civil and Environmental Engineering Abstract The durability of structures is one of primary concerns in the engineering industry. Poor durability in design may result in a structure losing its performance to the extent where structural integrity is no longer satisfied and human lives are at stake. Moreover, the associated costs of maintenance and repair due to inadequate design considerations are high. Thus, designing for durable structures not only helps sustain our infrastructure, it also reduces future costs. This thesis identifies the key factors that define and impact durability, with particular attention paid to the effect of material choice on overall durability. This follows a study of the different deteriorating mechanisms that wood, steel and reinforced concrete undergo over time, and the different enhancement techniques used to reduce the adverse effects of these mechanisms. Finally, a comparison study is carried out comparing the different material properties of wood, steel and concrete and the effect of using alternative materials on cost and quantity of material used. This further enhances the understanding of the impact that the design choices make, during the early stages of the project, on the overall durability of the structure. Keywords: Durability, material, deterioration, enhancement Thesis Supervisor: Jerome J. Connor Title: Professor of Civil and Environmental Engineering Thesis Reader: Rory Clune Massachusetts Institute of Technology 3 4 Acknowledgements I would like to thank Professor Jerome Connor for his guidance and constant support throughout my time at MIT. Thanks also to Rory Clune for his time and guidance which I greatly appreciate, especially knowing he had his own thesis to write. His motivation and encouragement were the driving forces of my writing process, without which this work would not have been possible. Moreover, thanks to Pierre Ghisban for his endless help and support, and Pamela Siska and Mays Chami, for proofreading my work and providing me with feedback. Last but not least, I would like to thank my family and friends for their constant support and patience, my sister Maria for always being there for me, and my classmates at MIT who made this year an unforgettable experience. Dana Saba 5 6 Table of Contents List of Figures ........................................................................................................................................ 9 List of Tables ........................................................................................................................................ 13 1 Chapter 1 Overview .................................................................................................................... 15 1.1 Introduction ........................................................................................................................................ 15 1.2 Thesis Outline ..................................................................................................................................... 17 2 Chapter 2 Durability .................................................................................................................. 19 2.1 Definition ............................................................................................................................................. 19 2.2 Outlining durability in a design problem .................................................................................. 22 2.3 Factors affecting the durability of structures .......................................................................... 23 2.4 National Standards and Guides ..................................................................................................... 26 2.4.1 British Standard, BS7543 ............................................................................................................................. 27 2.4.2 Canadian Standards, S478 ............................................................................................................................ 28 2.5 Discussion ............................................................................................................................................ 30 3 Chapter 3 Materials and Technology .................................................................................... 33 3.1 Wood ...................................................................................................................................................... 34 3.1.1 Wood as a structural material ...................................................................................................................... 34 3.1.2 Deterioration Mechanisms ........................................................................................................................... 35 3.1.3 Enhancement Techniques ............................................................................................................................. 39 3.1.3.1 Chemical Enhancement .......................................................................................................................................... 40 3.1.3.2 Physical Enhancement ............................................................................................................................................ 42 3.1.4 Discussion .......................................................................................................................................................... 44 3.2 Concrete ................................................................................................................................................ 45 3.2.1 Concrete as a structural material ................................................................................................................ 45 3.2.2 Deterioration Mechanisms ........................................................................................................................... 48 3.2.3 Enhancement Techniques ............................................................................................................................. 52 3.2.3.1 Chemical Enhancement .......................................................................................................................................... 53 3.2.3.2 Physical Enhancement ............................................................................................................................................ 54 3.2.4 Discussion .......................................................................................................................................................... 55 3.3 Steel ........................................................................................................................................................ 56 3.3.1 Steel as a structural material ........................................................................................................................ 56 3.3.2 Deterioration Mechanisms ........................................................................................................................... 58 3.3.3 Enhancement Techniques ............................................................................................................................. 60 3.3.3.1 Chemical Enhancement .......................................................................................................................................... 61 3.3.3.2 Physical Enhancement ............................................................................................................................................ 62 3.3.4 Discussion .......................................................................................................................................................... 63 3.4 Material Comparison ........................................................................................................................ 64 3.4.1 Factors affecting properties of wood ........................................................................................................ 64 3.4.2 Factors affecting properties of steel .......................................................................................................... 65 3.4.3 Factors affecting properties of concrete ................................................................................................... 67 3.4.4 Numerical Model ............................................................................................................................................. 69 3.4.4.1