Correlation Between In-Place Analysis and Reserve Strength Ratio for Fixed Offshore Platforms: A Parametric Assessment

Correlation Between In-Place Analysis and Reserve Strength Ratio for Fixed Offshore Platforms: A Parametric Assessment | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Correlation Between In-Place Analysis and Reserve Strength Ratio for Fixed Offshore Platforms: A Parametric Assessment Ahmed ElHamahmy This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8613399/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Aging fixed offshore platforms increasingly require structural reassessment to support life-extension and modification decisions. Conventional linear in-place analysis provides member-level demand–capacity checks under prescribed load combinations, while nonlinear collapse analysis yields the Reserve Strength Ratio (RSR) as a global indicator of structural redundancy and ultimate capacity. Although both approaches are widely used in offshore engineering practice, their results are often interpreted independently, leading to conservative decisions and potentially unnecessary strengthening measures. This study investigates the correlation between in-place analysis results and RSR values for fixed offshore platforms using a simulated yet engineering-realistic dataset developed in accordance with industry practice and offshore design standards. Fifteen representative jacket platforms with varying configurations, water depths, and structural conditions were assessed using linear in-place analysis and nonlinear pushover collapse analysis. Statistical relationships between RSR and key in-place performance indicators, including maximum member utilization and the percentage of overstressed members, were examined. The results demonstrate a clear inverse trend between RSR and in-place utilization ratios, with platforms exhibiting RSR values exceeding approximately 1.6 generally showing acceptable global and local performance. However, noticeable scatter and isolated exceptions highlight that RSR cannot replace detailed in-place checks. The findings support the use of RSR as a preliminary screening indicator to inform engineering judgment and optimize reassessment strategies for brownfield offshore assets. Fixed offshore platforms In-place analysis Reserve Strength Ratio API RP 2SIM Structural reassessment Offshore integrity Figures Figure 1 Figure 2 Figure 3 1. Introduction A significant portion of the global offshore infrastructure was installed between the 1970s and 1990s and is currently operating beyond its original design life. These aging fixed offshore platforms are increasingly subjected to reassessment due to life-extension requirements, field redevelopment, and the addition of new topside loads. Ensuring structural integrity while minimizing unnecessary strengthening has become a critical challenge for asset owners and engineers. Structural reassessment of fixed offshore platforms is commonly performed using two complementary approaches: linear in-place analysis and nonlinear collapse assessment. Linear in-place analysis evaluates member- and joint-level utilization under prescribed environmental and operational load combinations, while nonlinear pushover analysis evaluates global collapse behavior and determines the Reserve Strength Ratio (RSR), defined as the ratio of ultimate collapse load to design environmental load (API RP 2A; API RP 2SIM) [1,2]. In-place analysis is widely recognized as conservative, as it does not account for redundancy, load redistribution, or post-yield behavior. Conversely, RSR provides valuable insight into the global robustness of a structure but does not directly identify localized overstress or serviceability issues. In practice, it is not uncommon for platforms to exhibit localized overstress in linear analysis while demonstrating substantial global reserve strength in nonlinear collapse simulations [3]. Although design and reassessment standards acknowledge the complementary nature of linear and nonlinear assessments, limited published work has focused on systematically correlating in-place performance indicators with RSR results. Most existing studies address these assessment methods independently, particularly in the context of life extension and integrity management of aging offshore structures [4,5]. Establishing a clearer relationship between local utilization metrics and global reserve strength could support more balanced engineering judgment and cost-effective decision-making. This paper presents a parametric investigation into the relationship between in-place analysis results and RSR values for fixed offshore platforms. Using a simulated but engineering-realistic dataset representative of typical jacket structures, the study aims to identify trends, quantify correlations, and evaluate the potential role of RSR as a preliminary screening indicator for in-place structural adequacy. 2. Methodology 2.1 Overview The study adopts a parametric assessment approach in which a set of representative fixed offshore platforms is evaluated using both linear in-place analysis and nonlinear pushover collapse analysis. Key performance indicators from each analysis are extracted and statistically correlated to investigate underlying trends and practical implications relevant to offshore structural reassessment. 2.2 Platform Representation Fifteen fixed offshore jacket platforms were considered in the study. The platforms were selected to represent typical configurations encountered in shallow-to-medium water depths, including four-legged and six-legged jackets with varying degrees of structural redundancy. Platform age, water depth, and configuration were varied within realistic industry ranges consistent with offshore design and reassessment practice [1,6]. Due to confidentiality constraints associated with real offshore assets, the platform models and results were generated using a simulated dataset calibrated to reflect realistic offshore engineering behavior. The simulated values were selected to be consistent with published literature and industry experience. 2.3 In-Place Analysis Linear elastic in-place analyses were performed for each platform under relevant operational and environmental load combinations. Member demand–capacity ratios (utilization coefficients, UC) were evaluated in accordance with established offshore design criteria as outlined in API RP 2A and ISO 19902 [1,7]. The following in-place performance indicators were extracted: Maximum member utilization ratio Average member utilization ratio Percentage of members with utilization ratios exceeding unity These indicators were selected to capture both peak local demands and overall structural performance. 2.4 Collapse Analysis and RSR Evaluation Nonlinear static pushover analyses were conducted to determine the ultimate collapse capacity of each platform. Environmental loads were incrementally increased until global instability or numerical collapse was observed. The Reserve Strength Ratio (RSR) was calculated as the ratio of collapse load to the corresponding design environmental load. The definition, interpretation, and use of RSR adopted in this study are consistent with the guidance provided in API RP 2SIM for reassessment and modification of existing offshore structures [2]. RSR is treated as a global indicator of redundancy and robustness rather than a replacement for local strength checks. 2.5 Correlation Framework Statistical relationships between RSR values and in-place performance indicators were examined using scatter plots and correlation coefficients. Both Pearson and Spearman correlation measures were considered to capture linear and monotonic trends. The objective was not to develop a deterministic predictive model but rather to identify practical trends that could support engineering judgment during reassessment. 3. Simulated Dataset Description Table 1 summarizes the simulated dataset used in the study. The values were generated to reflect realistic offshore platform behavior, including inherent variability, redundancy effects, and isolated outliers commonly observed in reassessment studies [4–6]. Table 1 Simulated platform characteristics and analysis results (source: Created by Author) Platform Water Depth (m) Jacket Type Platform Age (years) RSR Max UC (In-Place) Members with UC > 1.0 (%) P-01 35 4-leg 28 1.42 1.12 14 P-02 42 4-leg 32 1.55 1.05 9 P-03 48 6-leg 30 1.68 0.98 5 P-04 55 4-leg 40 1.6 1.02 7 P-05 60 6-leg 35 1.75 0.94 3 P-06 65 4-leg 45 1.33 1.18 17 P-07 70 6-leg 38 1.82 0.9 2 P-08 75 4-leg 50 1.28 1.22 18 P-09 80 6-leg 42 1.9 0.88 1 P-10 85 4-leg 48 1.47 1.08 11 P-11 90 6-leg 36 2.05 0.84 0 P-12 58 4-leg 34 1.62 0.99 6 P-13 62 6-leg 29 1.78 0.92 4 P-14 68 4-leg 44 1.36 1.15 15 P-15 72 6-leg 33 1.88 0.89 2 4. Results 4.1 Relationship Between RSR and Maximum In-Place Utilization Figure 1 illustrates the relationship between the Reserve Strength Ratio (RSR) and the maximum member utilization ratio obtained from in-place analysis. An inverse trend is observed, with higher RSR values generally associated with lower in-place utilization ratios. Platforms exhibiting RSR values below approximately 1.4 consistently demonstrate elevated utilization ratios, with several cases exceeding unity. In contrast, platforms with RSR values greater than 1.6 predominantly show maximum utilization ratios below or close to unity, indicating acceptable local structural performance under linear analysis assumptions. 4.2 RSR Versus Percentage of Overstressed Members Figure 2 presents the relationship between RSR and the percentage of members with utilization ratios exceeding unity. A strong monotonic decrease is observed as RSR increases. Platforms with RSR values above approximately 1.7 generally exhibit less than 5% overstressed members, while platforms with RSR values below 1.4 often show overstress in more than 10% of structural members. This behavior highlights the role of global redundancy and load redistribution in mitigating localized overstress, particularly in multi-leg jacket configurations. 4.3 Statistical Correlation Correlation analysis confirms a negative relationship between RSR and maximum in-place utilization. Both Pearson and Spearman coefficients indicate a statistically meaningful inverse trend, consistent with observations reported in previous offshore integrity studies [3,5]. Nevertheless, observed scatter reinforces that RSR alone cannot fully characterize local structural adequacy. 5. Discussion The observed inverse relationship between RSR and in-place utilization reflects the fundamental differences between global and local assessment philosophies. RSR captures the ability of a structure to redistribute loads through alternative load paths following localized yielding or member failure, while in-place analysis evaluates individual members under linear elastic assumptions without accounting for redundancy [3,6]. This observation aligns with API RP 2SIM guidance, which emphasizes that global strength metrics such as RSR should be used to inform, but not replace, detailed member and joint checks during reassessment of existing offshore structures [2]. The results further indicate that four-legged jackets and older platforms are more prone to localized overstress for a given RSR, highlighting the influence of redundancy and aging effects. 6. Practical Implications for Engineering Practice Figure 3 . Proposed RSR-based screening framework for structural reassessment of fixed offshore platforms, indicating indicative risk zones consistent with API RP 2SIM reassessment philosophy. RSR < 1.4: High likelihood of global and local inadequacy; strengthening or detailed reassessment is generally required. 1.4 ≤ RSR ≤ 1.6: Transitional zone requiring careful in-place checks and engineering judgment. RSR > 1.6: Generally indicative of adequate global capacity, with localized overstress typically manageable through targeted mitigation. This framework is consistent with the intent of API RP 2SIM, particularly for modification screening and life-extension assessments [2]. (source: Created by Author) 7. Limitations The study is subject to several limitations. The dataset is simulated and does not represent specific offshore assets. Soil–structure interaction variability, joint capacity, fatigue performance, and nonlinear dynamic effects were not explicitly considered. These limitations should be addressed in future studies using field data and advanced modeling techniques. 8. Future Trends and Recommendations Future work should focus on validating the proposed correlation framework using real reassessment data from offshore platforms. Integration of joint capacity, corrosion degradation models, and pile–soil interaction uncertainty would further enhance reliability. Probabilistic and reliability-based approaches, as well as digital twin implementations, represent promising directions for embedding RSR-based screening into offshore integrity management systems. 9. Conclusions This study examined the relationship between in-place analysis results and Reserve Strength Ratio values for fixed offshore platforms using a simulated parametric dataset. A clear inverse trend was observed, with higher RSR values generally associated with improved local and global structural performance. Platforms exhibiting RSR values exceeding approximately 1.6 typically demonstrated acceptable in-place behavior, although localized overstress may still occur. The results confirm that RSR is a valuable indicator of global robustness but cannot replace detailed in-place analysis. When used appropriately, RSR can support informed engineering judgment and more efficient reassessment strategies for aging offshore assets, consistent with API RP 2SIM guidance. Declarations Availability of data and material All data supporting the findings of this study are publicly available in the cited literature. Ethics Not applicable Consent to Participate Not applicable Consent to Publish Not applicable Clinical Trial Number Not applicable. Competing interests The author declares that there are no competing interests. Funding This research received no external funding. Authors contribution The author is solely responsible for the conception, analysis, writing, and final approval of the manuscript. Acknowledgements Not applicable. Author Information Professional Ph.D. Researcher, Faculty of Graduate Studies for Statistical Research, Cairo University, Giza, Egypt University Email: [email protected] , Personal Email: [email protected] ORCID: https://orcid.org/0009-0009-9547-8966 References American Petroleum Institute (API). API Recommended Practice 2A-WSD: Planning, Designing, and Constructing Fixed Offshore Platforms—Working Stress Design. Washington, DC: API. Available at: https://www.api.org/products-and-services/standards American Petroleum Institute (API). API Recommended Practice 2SIM: Structural Integrity Management of Fixed Offshore Structures. Washington, DC: API. Available at: https://www.api.org/products-and-services/standards Bea RG. Reliability and integrity management of offshore structures. Mar Struct. 2005;18(2):111–34. (No DOI found; no specific article URL available from search results.). Moan T. Life extension of offshore structures. J Offshore Mech Arct Eng. 2010;132(3):030905. Journal homepage. https://asmedigitalcollection.asme.org/offshoremechanics . Jensen JJ, Sørensen JD. Risk-based approaches to structural reassessment of offshore platforms. Mar Struct. 2002;15(2–3):141–62. (No DOI or article URL found through search.). Hellan Ø, Skallerud B. Ultimate strength assessment of jacket platforms under environmental loading. Ocean Eng. 2001;28(7):899–923. (No DOI located; no direct article URL retrieved.). International Organization for Standardization (ISO). ISO 19902: Petroleum and natural gas industries — Fixed steel offshore structures. Geneva: ISO. Available at: https://www.iso.org/standard/37092.html Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8613399","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":587608349,"identity":"f013bc2d-fdd7-49ab-942d-0f7534577083","order_by":0,"name":"Ahmed ElHamahmy","email":"data:image/png;base64,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","orcid":"","institution":"Cairo University","correspondingAuthor":true,"prefix":"","firstName":"Ahmed","middleName":"","lastName":"ElHamahmy","suffix":""}],"badges":[],"createdAt":"2026-01-15 20:08:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8613399/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8613399/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102604610,"identity":"23f02fac-18c0-44cc-bc8e-ad060b035a69","added_by":"auto","created_at":"2026-02-13 13:42:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":74770,"visible":true,"origin":"","legend":"\u003cp\u003eRSR vs Maximum In-place Utilization (source: Created by Author)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8613399/v1/a1e47defa4ba71040187e8c4.png"},{"id":102604611,"identity":"7988a305-61f1-43db-b371-36d00a428884","added_by":"auto","created_at":"2026-02-13 13:42:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":59483,"visible":true,"origin":"","legend":"\u003cp\u003eRSR vs Percentage of Overstressed Members (source: Created by Author)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8613399/v1/6aaae713bdf4632320b34abe.png"},{"id":102604612,"identity":"862d6e35-e921-4c5f-b522-185be8baa4e5","added_by":"auto","created_at":"2026-02-13 13:42:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":278359,"visible":true,"origin":"","legend":"\u003cp\u003eProposed RSR‑based screening framework for structural reassessment of fixed offshore platforms\u003c/p\u003e\n\u003cp\u003e(source: Created by Author)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8613399/v1/3e5cf0059a0e38f577bd57bf.png"},{"id":108491448,"identity":"6e72c4f8-9eb7-411d-9dce-8b3b259680d1","added_by":"auto","created_at":"2026-05-05 09:53:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":623727,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8613399/v1/fd8c7013-b299-4654-a75c-0568974f6198.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Correlation Between In-Place Analysis and Reserve Strength Ratio for Fixed Offshore Platforms: A Parametric Assessment","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eA significant portion of the global offshore infrastructure was installed between the 1970s and 1990s and is currently operating beyond its original design life. These aging fixed offshore platforms are increasingly subjected to reassessment due to life-extension requirements, field redevelopment, and the addition of new topside loads. Ensuring structural integrity while minimizing unnecessary strengthening has become a critical challenge for asset owners and engineers.\u003c/p\u003e \u003cp\u003eStructural reassessment of fixed offshore platforms is commonly performed using two complementary approaches: linear in-place analysis and nonlinear collapse assessment. Linear in-place analysis evaluates member- and joint-level utilization under prescribed environmental and operational load combinations, while nonlinear pushover analysis evaluates global collapse behavior and determines the Reserve Strength Ratio (RSR), defined as the ratio of ultimate collapse load to design environmental load (API RP 2A; API RP 2SIM) [1,2].\u003c/p\u003e \u003cp\u003eIn-place analysis is widely recognized as conservative, as it does not account for redundancy, load redistribution, or post-yield behavior. Conversely, RSR provides valuable insight into the global robustness of a structure but does not directly identify localized overstress or serviceability issues. In practice, it is not uncommon for platforms to exhibit localized overstress in linear analysis while demonstrating substantial global reserve strength in nonlinear collapse simulations [3].\u003c/p\u003e \u003cp\u003eAlthough design and reassessment standards acknowledge the complementary nature of linear and nonlinear assessments, limited published work has focused on systematically correlating in-place performance indicators with RSR results. Most existing studies address these assessment methods independently, particularly in the context of life extension and integrity management of aging offshore structures [4,5]. Establishing a clearer relationship between local utilization metrics and global reserve strength could support more balanced engineering judgment and cost-effective decision-making.\u003c/p\u003e \u003cp\u003eThis paper presents a parametric investigation into the relationship between in-place analysis results and RSR values for fixed offshore platforms. Using a simulated but engineering-realistic dataset representative of typical jacket structures, the study aims to identify trends, quantify correlations, and evaluate the potential role of RSR as a preliminary screening indicator for in-place structural adequacy.\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Overview\u003c/h2\u003e \u003cp\u003eThe study adopts a parametric assessment approach in which a set of representative fixed offshore platforms is evaluated using both linear in-place analysis and nonlinear pushover collapse analysis. Key performance indicators from each analysis are extracted and statistically correlated to investigate underlying trends and practical implications relevant to offshore structural reassessment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Platform Representation\u003c/h2\u003e \u003cp\u003eFifteen fixed offshore jacket platforms were considered in the study. The platforms were selected to represent typical configurations encountered in shallow-to-medium water depths, including four-legged and six-legged jackets with varying degrees of structural redundancy. Platform age, water depth, and configuration were varied within realistic industry ranges consistent with offshore design and reassessment practice [1,6].\u003c/p\u003e \u003cp\u003eDue to confidentiality constraints associated with real offshore assets, the platform models and results were generated using a simulated dataset calibrated to reflect realistic offshore engineering behavior. The simulated values were selected to be consistent with published literature and industry experience.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 In-Place Analysis\u003c/h2\u003e \u003cp\u003eLinear elastic in-place analyses were performed for each platform under relevant operational and environmental load combinations. Member demand\u0026ndash;capacity ratios (utilization coefficients, UC) were evaluated in accordance with established offshore design criteria as outlined in API RP 2A and ISO 19902 [1,7].\u003c/p\u003e \u003cp\u003eThe following in-place performance indicators were extracted:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eMaximum member utilization ratio\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAverage member utilization ratio\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePercentage of members with utilization ratios exceeding unity\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThese indicators were selected to capture both peak local demands and overall structural performance.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Collapse Analysis and RSR Evaluation\u003c/h2\u003e \u003cp\u003eNonlinear static pushover analyses were conducted to determine the ultimate collapse capacity of each platform. Environmental loads were incrementally increased until global instability or numerical collapse was observed. The Reserve Strength Ratio (RSR) was calculated as the ratio of collapse load to the corresponding design environmental load.\u003c/p\u003e \u003cp\u003eThe definition, interpretation, and use of RSR adopted in this study are consistent with the guidance provided in API RP 2SIM for reassessment and modification of existing offshore structures [2]. RSR is treated as a global indicator of redundancy and robustness rather than a replacement for local strength checks.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Correlation Framework\u003c/h2\u003e \u003cp\u003eStatistical relationships between RSR values and in-place performance indicators were examined using scatter plots and correlation coefficients. Both Pearson and Spearman correlation measures were considered to capture linear and monotonic trends. The objective was not to develop a deterministic predictive model but rather to identify practical trends that could support engineering judgment during reassessment.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Simulated Dataset Description","content":"\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes the simulated dataset used in the study. The values were generated to reflect realistic offshore platform behavior, including inherent variability, redundancy effects, and isolated outliers commonly observed in reassessment studies [4\u0026ndash;6].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSimulated platform characteristics and analysis results\u003c/p\u003e \u003cdiv class=\"Credit\"\u003e\u003cp\u003e(source: Created by Author)\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlatform\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWater Depth (m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eJacket Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePlatform Age (years)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRSR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMax UC (In-Place)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMembers with UC\u0026thinsp;\u0026gt;\u0026thinsp;1.0 (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP-15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6-leg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"4. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Relationship Between RSR and Maximum In-Place Utilization\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates the relationship between the Reserve Strength Ratio (RSR) and the maximum member utilization ratio obtained from in-place analysis. An inverse trend is observed, with higher RSR values generally associated with lower in-place utilization ratios.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePlatforms exhibiting RSR values below approximately 1.4 consistently demonstrate elevated utilization ratios, with several cases exceeding unity. In contrast, platforms with RSR values greater than 1.6 predominantly show maximum utilization ratios below or close to unity, indicating acceptable local structural performance under linear analysis assumptions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e4.2 RSR Versus Percentage of Overstressed Members\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the relationship between RSR and the percentage of members with utilization ratios exceeding unity. A strong monotonic decrease is observed as RSR increases. Platforms with RSR values above approximately 1.7 generally exhibit less than 5% overstressed members, while platforms with RSR values below 1.4 often show overstress in more than 10% of structural members.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis behavior highlights the role of global redundancy and load redistribution in mitigating localized overstress, particularly in multi-leg jacket configurations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Statistical Correlation\u003c/h2\u003e \u003cp\u003eCorrelation analysis confirms a negative relationship between RSR and maximum in-place utilization. Both Pearson and Spearman coefficients indicate a statistically meaningful inverse trend, consistent with observations reported in previous offshore integrity studies [3,5]. Nevertheless, observed scatter reinforces that RSR alone cannot fully characterize local structural adequacy.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Discussion","content":"\u003cp\u003eThe observed inverse relationship between RSR and in-place utilization reflects the fundamental differences between global and local assessment philosophies. RSR captures the ability of a structure to redistribute loads through alternative load paths following localized yielding or member failure, while in-place analysis evaluates individual members under linear elastic assumptions without accounting for redundancy [3,6].\u003c/p\u003e \u003cp\u003eThis observation aligns with API RP 2SIM guidance, which emphasizes that global strength metrics such as RSR should be used to inform, but not replace, detailed member and joint checks during reassessment of existing offshore structures [2]. The results further indicate that four-legged jackets and older platforms are more prone to localized overstress for a given RSR, highlighting the influence of redundancy and aging effects.\u003c/p\u003e"},{"header":"6. Practical Implications for Engineering Practice","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Proposed RSR-based screening framework for structural reassessment of fixed offshore platforms, indicating indicative risk zones consistent with API RP 2SIM reassessment philosophy.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eRSR\u0026thinsp;\u0026lt;\u0026thinsp;1.4: High likelihood of global and local inadequacy; strengthening or detailed reassessment is generally required.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e1.4\u0026thinsp;\u0026le;\u0026thinsp;RSR\u0026thinsp;\u0026le;\u0026thinsp;1.6: Transitional zone requiring careful in-place checks and engineering judgment.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eRSR\u0026thinsp;\u0026gt;\u0026thinsp;1.6: Generally indicative of adequate global capacity, with localized overstress typically manageable through targeted mitigation.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThis framework is consistent with the intent of API RP 2SIM, particularly for modification screening and life-extension assessments [2].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(source: Created by Author)\u003c/p\u003e"},{"header":"7. Limitations","content":"\u003cp\u003eThe study is subject to several limitations. The dataset is simulated and does not represent specific offshore assets. Soil\u0026ndash;structure interaction variability, joint capacity, fatigue performance, and nonlinear dynamic effects were not explicitly considered. These limitations should be addressed in future studies using field data and advanced modeling techniques.\u003c/p\u003e"},{"header":"8. Future Trends and Recommendations","content":"\u003cp\u003eFuture work should focus on validating the proposed correlation framework using real reassessment data from offshore platforms. Integration of joint capacity, corrosion degradation models, and pile\u0026ndash;soil interaction uncertainty would further enhance reliability. Probabilistic and reliability-based approaches, as well as digital twin implementations, represent promising directions for embedding RSR-based screening into offshore integrity management systems.\u003c/p\u003e"},{"header":"9. Conclusions","content":"\u003cp\u003eThis study examined the relationship between in-place analysis results and Reserve Strength Ratio values for fixed offshore platforms using a simulated parametric dataset. A clear inverse trend was observed, with higher RSR values generally associated with improved local and global structural performance. Platforms exhibiting RSR values exceeding approximately 1.6 typically demonstrated acceptable in-place behavior, although localized overstress may still occur.\u003c/p\u003e \u003cp\u003eThe results confirm that RSR is a valuable indicator of global robustness but cannot replace detailed in-place analysis. When used appropriately, RSR can support informed engineering judgment and more efficient reassessment strategies for aging offshore assets, consistent with API RP 2SIM guidance.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data supporting the findings of this study are publicly available in the cited literature.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003eClinical Trial Number\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003eThe author declares that there are no competing interests.\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003eAuthors contribution\u003c/p\u003e\n\u003cp\u003eThe author is solely responsible for the conception, analysis, writing, and final approval of the manuscript.\u003c/p\u003e\n\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003eAuthor Information\u003c/p\u003e\n\u003cp\u003eProfessional Ph.D. Researcher, Faculty of Graduate Studies for Statistical Research, Cairo University, Giza, Egypt\u003c/p\u003e\n\u003cp\u003eUniversity Email: [email protected], Personal Email: [email protected]\u003c/p\u003e\n\u003cp\u003eORCID: https://orcid.org/0009-0009-9547-8966\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAmerican Petroleum Institute (API). \u003cem\u003eAPI Recommended Practice 2A-WSD: Planning, Designing, and Constructing Fixed Offshore Platforms\u0026mdash;Working Stress Design.\u003c/em\u003e Washington, DC: API. Available at: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.api.org/products-and-services/standards\u003c/span\u003e\u003cspan address=\"https://www.api.org/products-and-services/standards\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAmerican Petroleum Institute (API). \u003cem\u003eAPI Recommended Practice 2SIM: Structural Integrity Management of Fixed Offshore Structures.\u003c/em\u003e Washington, DC: API. Available at: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.api.org/products-and-services/standards\u003c/span\u003e\u003cspan address=\"https://www.api.org/products-and-services/standards\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBea RG. Reliability and integrity management of offshore structures. Mar Struct. 2005;18(2):111\u0026ndash;34. (No DOI found; no specific article URL available from search results.).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoan T. Life extension of offshore structures. J Offshore Mech Arct Eng. 2010;132(3):030905. Journal homepage. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://asmedigitalcollection.asme.org/offshoremechanics\u003c/span\u003e\u003cspan address=\"https://asmedigitalcollection.asme.org/offshoremechanics\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJensen JJ, S\u0026oslash;rensen JD. Risk-based approaches to structural reassessment of offshore platforms. Mar Struct. 2002;15(2\u0026ndash;3):141\u0026ndash;62. (No DOI or article URL found through search.).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHellan \u0026Oslash;, Skallerud B. Ultimate strength assessment of jacket platforms under environmental loading. Ocean Eng. 2001;28(7):899\u0026ndash;923. (No DOI located; no direct article URL retrieved.).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eInternational Organization for Standardization (ISO). \u003cem\u003eISO 19902: Petroleum and natural gas industries \u0026mdash; Fixed steel offshore structures.\u003c/em\u003e Geneva: ISO. Available at: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.iso.org/standard/37092.html\u003c/span\u003e\u003cspan address=\"https://www.iso.org/standard/37092.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Fixed offshore platforms, In-place analysis, Reserve Strength Ratio, API RP 2SIM, Structural reassessment, Offshore integrity","lastPublishedDoi":"10.21203/rs.3.rs-8613399/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8613399/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAging fixed offshore platforms increasingly require structural reassessment to support life-extension and modification decisions. Conventional linear in-place analysis provides member-level demand\u0026ndash;capacity checks under prescribed load combinations, while nonlinear collapse analysis yields the Reserve Strength Ratio (RSR) as a global indicator of structural redundancy and ultimate capacity. Although both approaches are widely used in offshore engineering practice, their results are often interpreted independently, leading to conservative decisions and potentially unnecessary strengthening measures.\u003c/p\u003e \u003cp\u003eThis study investigates the correlation between in-place analysis results and RSR values for fixed offshore platforms using a simulated yet engineering-realistic dataset developed in accordance with industry practice and offshore design standards. Fifteen representative jacket platforms with varying configurations, water depths, and structural conditions were assessed using linear in-place analysis and nonlinear pushover collapse analysis. Statistical relationships between RSR and key in-place performance indicators, including maximum member utilization and the percentage of overstressed members, were examined.\u003c/p\u003e \u003cp\u003eThe results demonstrate a clear inverse trend between RSR and in-place utilization ratios, with platforms exhibiting RSR values exceeding approximately 1.6 generally showing acceptable global and local performance. However, noticeable scatter and isolated exceptions highlight that RSR cannot replace detailed in-place checks. The findings support the use of RSR as a preliminary screening indicator to inform engineering judgment and optimize reassessment strategies for brownfield offshore assets.\u003c/p\u003e","manuscriptTitle":"Correlation Between In-Place Analysis and Reserve Strength Ratio for Fixed Offshore Platforms: A Parametric Assessment","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-13 13:42:34","doi":"10.21203/rs.3.rs-8613399/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5ca53266-fbe8-45f2-a717-9bb1315550b1","owner":[],"postedDate":"February 13th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-30T11:55:27+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-13 13:42:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8613399","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8613399","identity":"rs-8613399","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}