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Numerical models for stress analysis of non-uniform corroded tubular members under compression
Vu Dan Chinh,Hà Thi Thu Nguyên 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.4
In re-assessing the Jacket-type fixed steel structures, the current standards often allow the simplicity of corrosion sections using local buckling or equivalent section approach to applying empirical formulae of frame stress and resistance analyses. However, those approaches can lead to significant errors for non-uniform corroded frames in a specific area, including force distribution, stress, and allowable strength of the tubular section, compared to the actual cases. This paper investigates a suitable approach to determine the actual stress on non-uniform corroded tubular frames under compression through the nonlinear ABAQUS model by considering the effect of large deformation on the frame axis and the frame section. There are 3 scenarios of interest. In the 1st and 2nd scenarios with simple corrosion cases, the stress ratios using the numerical model and theoretical formulae correspond to the calculation of allowable strength reduction ratios in standards. However, scenario 3, which describes non-uniform corroded sections based on survey data, provides considerable differences in results. Therefore, it proves the reliable and effective results when using this method to analyze the resistance of the actual corroded section in the Jacket platforms.
Numerical Study on Ultimate Strength of Non-uniform Corroded Tubular T-joints under Compression
Vu Dan Chinh,Hà Thi Thu Nguyên 한국정밀공학회 2023 한국정밀공학회지 Vol.40 No.9
The literature states that the existing guidelines mainly focus on the ultimate strength of uniform corroded joints in the Jacket-type re-assessment. However, joints are non-uniformly corroded in different shapes in reality. Results derived from theoretical equations in these scenarios are significantly different from the actual capacity of the frame joints. This paper studies the influences of thickness and corroded area on the T- joint’s ultimate strength for a chord based on the numerical model ABAQUS. Numerical results show the effects of location and dimension at corroded areas on the tubular joint ultimate strength. Moreover, this research proposes a new formula based on API to estimate the strength of T-joints connected with non-uniform corroded compressive braces in certain conditions. This equation is validated by comparison of the numerical simulation in independent cases.