Seismic eva‎luation of the Damaged Offshore Platform in the Persian Gulf (Case Study: Resalat Platform)

1/1/1900 12:00:00 AM

Offshore platforms are one of the most vital lifelines of the economies of countries, an‎d they consist of numerous important structures that are critical to the classification of such facilities. Most of the platforms built in Iran have reached the end of their useful life an‎d need reeva‎luations to continue functioning. The platform under study is located in the Resalat oil field in the Persian Gulf, which was constructed more than 60 years ago. Throughout its life, the platform has experienced numerous changes an‎d damages, some of which are listed in the Dullam inspection report conducted in 2001, detailing the extent of these damages. Over the years, the Resalat oil field platform has sustained damage, including corrosion, flooding of components, loss of protection, an‎d marine organism buildup on platform members. In this study, the platform under investigation has been modeled using the SACS software, an‎d different types of damages, as outlined in the inspection report, have been applied to the model. This research explores various damage mechanisms, the applied damage to offshore platforms, damage modeling, methods of repair an‎d strengthening the structure, seismic changes according to the two codes API2019 an‎d API2005 within the Persian Gulf region, an‎d the behavior assessment of the damaged Resalat platform under seismic pressure. After performing dynamic analyses an‎d incremental load analysis using the SACS software, in accordance with both codes, the analysis results indicate that, according to API2019, the Unity Check (UC) of most of the platform’s components is above one an‎d has entered a critical condition. However, according to API2005, only the UC of certain members, especially in the splash zone, is above one. Furthermore, the analysis of the joints in the platform shows that according to API2019, 43 out of 48 joints, where more than two elements are connected, have a UC greater than one. However, based on API2005, only 19 joints out of the 48 joints have a UC above one. The analysis of the piles in the soil under seismic load reveals that according to API2019, all four piles are under both compressive an‎d tensile forces with a UC higher than one. However, according to API2005, only piles number three an‎d four had a UC slightly above one under compressive load. Based on the results, the stored strength in accordance with API2019 has significantly decreased due to the increased seismic acceleration in the Persian Gulf region, with the value falling below 1.6. In contrast, API2005 shows that the stored strength remains above 1.6, which is acceptable. Additionally, the results indicate that plasticity first occurred in the piles in the soil an‎d other vertical an‎d horizontal elements in the splash zone.

سـازههاي دريايي , سـكوي درياي آسـيب ديده , اثر لرزهاي , ضـريب مقاومت ذخيرهاي , آيين نامه API

Offshore Platform , Damaged Offshore Platform , Seismic Effect , Reserve Resistance Coefficient , API Regulations

Ghazale Talakoub

Dr. Naser Shabakhty