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Investigation into Circular Steel Tubes with Pitting Corrosion under Axial Compression and Bending Moment

Salehi, Nazanin Fatemeh | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58352 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Moazezi Mehretehran, Alireza
  7. Abstract:
  8. In this research the behavior of Circular Steel Tubes (CSTs) with corrosion under axial force and bending have been studied. There are several factors leading to corrosion in steel structures, especially marine structures that results in strength reduction of whole structure. Steel tubes are widely used in construction of on-shore and off-shore structures such as, oil rigs and platforms, oil and gas transmission lines. Current study focus on strength reduction of steel tubes with “pitting corrosion”. To this end numerical analyses using finite element software, Abaqus, have been performed. Therefore, utilizing verified models, the simultaneous effect of bending, axial load and corrosion on CSTs have been evaluated. According to the performed analyses and in consistence with previous researches, the behavior of CSTs under combined axial compression and bending does affected marginally by dimensional characteristics and yield strength if the member strength govern with plastic hinge formation (plastic resistance of the cross-section). The morphological effect of pits also shows that the pitting depth has the most important influence on the load bearing capacity. Consequently, by conducting parametric study on a sample corroded CST, the reduction in its combined capacity by selecting different pitting depth for mass loss index ranges from 10 to 30 percent has been obtained. Taking into account the AISC360-22 equation in determining the capacity of intact CSTs under combined action of axial load and bending, based on the conducted parametric study, two modification factors have been purposed. It is intended to estimate the load bearing capacity of CSTs with pitting corrosion using down scaling of AISC360-22 equation by the purposed factors. According to obtained results and examination of the purposed method, the maximum difference were found to be 9 percent on safe side. This shows the applicability of the method. In order to enhance the conducted research, it was also purposed to expand the parametric study and making use of machine learning techniques to produce more precise modifications factors
  9. Keywords:
  10. Pitting Corrosion ; Axial Compression ; Bending Moment ; Circular Tubes ; American Institute of Steel Construction 360 (AISC360) ; Circular Steel Tubes (CSTs)

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