Question:

I have to check DNV criteria for accidental load drop. How do I prepare the limits?

Answer:

The RESIDUAL RATIO limit can be used. This limit looks at the ratio of the areas before and after equilibrium.

LIMIT RES RATIO FROM 0 TO RA0 OR FLD > 1.4

Also, you could include a limit for the 15 degrees at equilibrium after hook load drop:

LIMIT ANGLE AT EQU < 15

The procedure would be,

1. Establish the crane with hook load heeling to starboard. For example,

BOOM "HOOK LOAD" 10, 0, 0, 12, 100, 90, 45
BOOM "COUNTER WEIGHT" 30, 0, 0, 14, 6, -90, 0
SOLVE

2. Drop the hook load:

DELETE "HOOK LOAD"

3. Run the RA curve to port:

RA 0, -2, ..., -30 /LIM:ATT

There is also a sample run file, CRANEDNV, that demonstrates this.