thanks a lot for your reply .
I have another question. Do I get any advantage (using Time history analysis instead of static) for such problems involving large impact loads that last only few milli seconds as in case of wave slamming?

The magnitude that we see here can lead to high stresses (beyond the elastic limit).

I am treating it as an accident load and checking it against min (1.5 Sy or 2.4 Sh).

can any one state the advantage. Thanks.