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Residual Ultimate Buckling Strength of Steel Stiffened Panels Subjected RESIDUAL ULTIMATE BUCKLING STRENGTH OF STEEL STIFFENED PANELS SUBJECTED TO CORROSION DAMAGE A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment Of the Requirements for the Degree Master of Science Elijah Fox May, 2017 RESIDUAL ULTIMATE BUCKLING STRENGTH OF STEEL STIFFENED PANELS SUBJECTED TO CORROSION DAMAGE Elijah Fox Thesis Approved: Accepted: Advisor Department Chair Dr. Anil Patnaik Dr. Wieslaw K. Binienda Committee Member Interim Dean of the College Dr. Craig Menzemer Dr. Donald J. Visco Committee Member Dean of the Graduate School Dr. Ping Yi Dr. Chand Midha Date 2 ACKNOWLEDGEMENTS I would like to thank my mother, Janice, and my siblings, Kivie and Nakita. Without my families support over all of these years, I would not have been able to complete my degree. My mother has always been strong and has taught me so many fundamentals which I live by; I just want to thank her for making me the man I am today. My family has always been so supportive, loving, and has done anything they could to help me succeed and because of this, I am forever grateful. I owe a special thank you to my amazing life partner, Marisa. She has been in my life since my first day of college and I would not have been able to make it without her love and support throughout these years. She is still by my side through all of the trials and tribulations life has thrown at me over the past seven years and words could not express how appreciative I am of all of her help. Lastly, I would like to thank Dr. Anil Patnaik for the opportunity to pursue my master’s degree at The University of Akron. Over the last few years, his help and guidance has been invaluable and I will forever be appreciative for that. Dr. Patnaik has allowed me to explore worlds beyond structural engineering and has allowed me to broaden my knowledge beyond my focus of study. In addition, I would like to thank all of my colleagues at The University of Akron who have helped me over the process of my research. 3 ABSTRACT Corrosion is a naturally occurring electro-chemical process that causes damage in the form of surface material deterioration on metal structures. In many industries, particularly naval ships, it is common to assess the corrosion damage of structural components primarily based on visual inspection with limited or no structural stress analysis. Premature replacement of such components can prove expensive over time while delayed replacement of these components might be a safety concern. The overall goal in the assessment of remaining life is to relate thickness loss in the system to the performance of individual structural elements in order to better predict the remaining life of the structure. This methodology will be applied to some of the structural steel configurations that are of importance in naval applications. Corrosion damages on naval ships are mainly categorized as: uniform (general) corrosion, pitting corrosion, non-uniform, and grooving corrosion. This proposed study will investigate the effects of various intensities of uniform corrosion on the remaining ultimate buckling strength of stiffened panel under combined loading. While visual inspection of uniform (general) corrosion may be used industry wide, without qualitative research to support the quantitative data collected during visual inspection, this technique can prove un-reliable. This is due to the inability to accurately measure the thickness loss of the corroded surface. The objective of this study is to understand the relationship between increased levels of uniform corrosion and the decrease in remaining ultimate buckling strength of stiffened panel while being subjected to combined axial compression and lateral pressure. As a continuing effort to understand the various other forms of corrosion, we are tasked with developing a method to produce pitting and grooving 4 corrosion in a laboratory setting. In order to achieve this objective, a series of finite element analysis (FEA) models are conducted for stiffened panels subjected to combined loading with and without uniform corrosion damage. The FEA software package called ABAQUS is used to conduct these analyses. ASTM A572 grade 50 structural steel is the material used for the experimental testing and FEA models. Accelerated corrosion was performed on fabricated stiffened panels using the B117 method outlined in American Society for Testing and Materials (ASTM). The non-corroded and corroded stiffened panel specimens are mechanically tested under axial compression and the result are compared with the FEA results and industry guidelines. The FEA results and the experimental panel test data will provide a basis for developing a preliminary method to predict the remaining ultimate buckling strength of stiffened panels exposed to uniform corrosion under combined loading conditions. Based on the correlation between increased corrosion damage and the load of ultimate strength, the goal of this researched is to also act as a precursor to future works and help aid in the development of a visual inspection rating tool supported by qualitative data and/or modify preexisting design codes to include corrosion damage. 5 Table of Contents CHAPTER 1. INTRODUCTION .............................................................................................................................................................14 1.1 Problem Statement .................................................................................................................................................................. 15 1.2 Objectives ..................................................................................................................................................................................... 17 CHAPTER 2. CORROSION BACKGROUND RESEARCH .............................................................................................................19 2.1 Corrosion Definition and Chemistry .................................................................................................................................. 19 2.2 Types of Corrosion .................................................................................................................................................................... 24 2.2.1 Uniform (General) Corrosion ...................................................................................................................................24 2.2.2 Non-Uniform (Localized) Corrosion .....................................................................................................................27 2.2.3 Pitting Corrosion ...........................................................................................................................................................28 2.2.4 Grooving Corrosion ......................................................................................................................................................29 2.2.5 Galvanic Corrosion .......................................................................................................................................................30 2.3 Effects of Corrosion on Steel Structures and Members .............................................................................................. 32 2.4 Inspection and Controlling Corrosion Damage ............................................................................................................ 35 2.4.1 Inspections .......................................................................................................................................................................35 2.4.2 Visual Rating System ...................................................................................................................................................39 2.5.3 Corrosion Prevention and Mitigation Methods ...............................................................................................41 CHAPTER 3. LITERATURE REVIEW ................................................................................................................................................48 3.1 Structural Steel .......................................................................................................................................................................... 48 3.2 Stiffened Panels ......................................................................................................................................................................... 50 3.2.1 Stiffener .............................................................................................................................................................................55 3.3 Basic Ship Hull Structures ..................................................................................................................................................... 56 3.4 Load Distribution ...................................................................................................................................................................... 58 3.5 Stiffened Panel Failure Mode ............................................................................................................................................... 61 3.6 Factors that Affect the Ultimate Buckling Strength ................................................................................................... 67 3.7 Stiffened Panel Finite Element Analysis (FEA) modeling.........................................................................................
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