## 6 Conclusions  
The significant optimal intensity measure for offshore jacket platforms that can be used in the seismic probabilistic risk assessments is investigated in this research. A finite element model is developed using OpenSees and validated the model based on previous studies. Two demand parameters; peak acceleration and displacement are considered and obtained from nonlinear time history analysis. Linear regression analysis is performed to observe the correlation between IMs and demand parameters considering four significant indicators: efficiency, proficiency, practicality, and effectiveness. The summarization of the present study is:  
1. The significant IMs (EDA, A95, and PGA) are unrelated to the damping ratio, which is more rational for such structures.
2. As an offshore platform is a mass-sensitive structure and the inertia force influences the performance of selection criteria, the optimality of IM depends on the structure's demand parameter.
3. Based on comparing practicality, efficiency, proficiency, and effectiveness, acceleration-type IMs, i.e., EDA, A95, PGA, are the most optimal IMs because these IMs rank top consistently in all criteria considering maximum acceleration as the demand parameter of the structure. In case of maximum acceleration as EDP, the seismic response of an offshore platform is sensitive to acceleration rather than velocity or displacement.
4. Velocity-type IMs, i.e., HI and VSI, are the two most optimal IMs in all selected categories of optimal IM when maximum displacement as EDP is considered. The platform's response is reactive to velocity instead of acceleration or displacement if the EDP is maximum displacement.
5. A significant IM can improve the accuracy of the computation of seismic performance analysis. For offshore platforms, EDA and A95 parameter perform better than PGA and \(S_{a}\). Moreover, these IMs (EDA and A95) are structure-independent and thus becoming irrelative to the damping ratio.
6. For both cases of peak acceleration and displacement as EDPs, displacement-type IMs (PGD, D\({}_{\text{rms}}\)) are the weakest or least significant IMs subjected to the seismic demand of an offshore platform.  
Conceptualization, S.S.; Methodology, S.S.; Software, S.S.; FEM model and its validation, S.S., M.S.A., and C.S.; Formal analysis, S.S.; Investigation, S.S.; Writing--original draft preparation, S.S.; Writing--review and editing of final draft, S.S., D.K., M.S.A., C.S., and S.G.; Project administration, D.K.; Supervision, D.K.; Funding acquisition, D.K. All authors have read and agreed to the published version of the manuscript.  
Figure 12: Effectiveness comparison.  
**Funding:** This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2018R1A2B2005519). It was also supported by the National University Development Project by the Ministry of Education in 2021.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Some data that support the findings of this study are available from the corresponding author upon reasonable request.  
**Conflicts of Interest:** The authors declare no conflict of interest.