I have a steel drilling Derrick 240 feet high mounted central to a ship, this is used for drilling for oil. Calculations have been done on the Derrick in regards to reaction forces in different modes of operation(drilling, transit etc). I need to do a vibration analysis of different points on this structure with the figures to hand. I am in the believe that high amplitude >3mm @ 0-50 Hz frequency is expected of this type of structure in operating conditions. How do I calculate the vibration amplitude, frequency range and expected acceleration?