ABSTRACT

However, API does not specify the actual level of ground motion to be used and thus, the selection of return periods for the SLE and the DLE are left at the owner’s descretion.

Furthermore, there is a potential inconsistency in the use of the API guidelines, which is related to the widespread selection of the DLE ground motions as twice of the SLE level (i.e., DLE = 2.0 × SLE). API mentions in Section 2.3.6.d that“No ductility analysis of conventional jacket-type structures with 8 or more legs is required if the structure is to be located in an area where the intensity ratio of [DLE] to [SLE] is 2 or less…and the following conditions are adhered to in configuring the structure and proportioning members:…” after which the “DLE = 2.0 × SLE” rule has developed. To the author’s best knowledge, API does not state this as a general requirement for defining the DLE ground motion.