Product(s):	SACS
Version(s):	All
Area:	Fatigue

Problem

How to input scatter diagram in FTCASE? I have a data for 50 years and my jacket design life is 30 years. Should I need to divide the data by 50 or 30?

Solution

Let us walk through this procedure with an arbitrary sample data as following.

To enter the data for scatter diagram, you should be having data for different wave directions, for this case let us assume 0 degree. Similarly, you should be having data for other directions, say another 7 or 11 or any other numbers based on your design wave directions.

So, all together you would be having a combined set of data, and their corresponding cumulative sum (which is 25728 in our case). Based on total number of data (sum of all cumulative sums including all wave directions), how many data falls for 0 degree (here 25728) will provide you a fraction. This fraction you need to enter to the FTCASE line column 11-20, for each wave direction, corresponding to respective FTCASE.

For the frequency of occurrence shall be provided in fraction and total sum of all the frequencies within a FTCASE becomes unity.

Please refer SACS sample problem 08 for SCPER input pattern. You can also check our learning content video on Spectral Fatigue Analysis where SCPER line input is shown.

Regarding time duration of wave scatter data, it is engineers’ choice. However, since wave data frequency (percentage of occurrence in this case) is used as input in SCPER line, no need to divide by time duration of scatter data (in our case it is 50 years)

Period for cycle data is required for deterministic fatigue analysis and should be left blank in case spectral fatigue analysis.