Impact Loads due to wave slamming on horizontal members of the hull structure are of considerable interest in the context of very light and optimized structure, as found on Naval Vessel and other high speed vessels. These Slamming Loads are highly dynamic in nature, which is characterized by very short duration of the load, usually 10–20 milli-seconds, with a peak value for even a shorter duration. Therefore, a dynamic analysis is required to study the response of the structure, which is susceptible to slamming. Also, considering the extreme load response with a small probability of occurrence, certain amount of permanent deformation can be accepted. This paper presents the systematic transient dynamic analysis carried out for almost 2000 cases and proposes a method based on this study, for design of structures subjected to slamming loads. A Dynamic Load Factor, which converts the dynamic load into an equivalent static load, is introduced, after which a simple static analysis would yield the same results as that obtained from the dynamic analysis. Further, the paper also provides a method for calculating the plate thickness, given any slamming load, acceptable value of permanent deformation, and in-plane stress.