# Modified Inverse First Order Reliability Method (I-FORM) for Predicting Extreme Sea States.

## Abstract

Environmental contours describing extreme sea states are generated as the input for numerical or physical model simulation s as a part of the stand ard current practice for designing marine structure s to survive extreme sea states. Such environmental contours are characterized by combinations of significant wave height ( ) and energy period ( ) values calculated for a given recurrence interval using a set of data based on hindcast simulations or buoy observations over a sufficient period of record. The use of the inverse first - order reliability method (IFORM) i s standard design practice for generating environmental contours. In this paper, the traditional appli cation of the IFORM to generating environmental contours representing extreme sea states is described in detail and its merits and drawbacks are assessed. The application of additional methods for analyzing sea state data including the use of principal component analysis (PCA) to create an uncorrelated representation of the data under consideration is proposed. A reexamination of the components of the IFORM application to the problem at hand including the use of new distribution fitting techniques are shown to contribute to the development of more accurate a nd reasonable representations of extreme sea states formore »

- Authors:

- Publication Date:

- Research Org.:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

- Sponsoring Org.:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)

- OSTI Identifier:
- 1157595

- Report Number(s):
- SAND2014-17550

537505

- DOE Contract Number:
- AC04-94AL85000

- Resource Type:
- Technical Report

- Country of Publication:
- United States

- Language:
- English

### Citation Formats

```
Eckert-Gallup, Aubrey Celia, Sallaberry, Cedric Jean-Marie, Dallman, Ann Renee, and Neary, Vincent Sinclair.
```*Modified Inverse First Order Reliability Method (I-FORM) for Predicting Extreme Sea States.*. United States: N. p., 2014.
Web. doi:10.2172/1157595.

```
Eckert-Gallup, Aubrey Celia, Sallaberry, Cedric Jean-Marie, Dallman, Ann Renee, & Neary, Vincent Sinclair.
```*Modified Inverse First Order Reliability Method (I-FORM) for Predicting Extreme Sea States.*. United States. doi:10.2172/1157595.

```
Eckert-Gallup, Aubrey Celia, Sallaberry, Cedric Jean-Marie, Dallman, Ann Renee, and Neary, Vincent Sinclair. Mon .
"Modified Inverse First Order Reliability Method (I-FORM) for Predicting Extreme Sea States.". United States.
doi:10.2172/1157595. https://www.osti.gov/servlets/purl/1157595.
```

```
@article{osti_1157595,
```

title = {Modified Inverse First Order Reliability Method (I-FORM) for Predicting Extreme Sea States.},

author = {Eckert-Gallup, Aubrey Celia and Sallaberry, Cedric Jean-Marie and Dallman, Ann Renee and Neary, Vincent Sinclair},

abstractNote = {Environmental contours describing extreme sea states are generated as the input for numerical or physical model simulation s as a part of the stand ard current practice for designing marine structure s to survive extreme sea states. Such environmental contours are characterized by combinations of significant wave height ( ) and energy period ( ) values calculated for a given recurrence interval using a set of data based on hindcast simulations or buoy observations over a sufficient period of record. The use of the inverse first - order reliability method (IFORM) i s standard design practice for generating environmental contours. In this paper, the traditional appli cation of the IFORM to generating environmental contours representing extreme sea states is described in detail and its merits and drawbacks are assessed. The application of additional methods for analyzing sea state data including the use of principal component analysis (PCA) to create an uncorrelated representation of the data under consideration is proposed. A reexamination of the components of the IFORM application to the problem at hand including the use of new distribution fitting techniques are shown to contribute to the development of more accurate a nd reasonable representations of extreme sea states for use in survivability analysis for marine struc tures. Keywords: In verse FORM, Principal Component Analysis , Environmental Contours, Extreme Sea State Characteri zation, Wave Energy Converters},

doi = {10.2172/1157595},

journal = {},

number = ,

volume = ,

place = {United States},

year = {Mon Sep 01 00:00:00 EDT 2014},

month = {Mon Sep 01 00:00:00 EDT 2014}

}