Hi,
Got few questions regarding on COLLAPSE module outputs in SACS:
1. Why is the total energy absorbed (by local member, structure and ship) can be more than 100% (see below listing snapshot)? Where does extra 0.9872% energy comes from? It seems like conservation energy theory is violated.
Is it possible for the program to end the calculation if total absorbed energy yet to reach 100%? In one of my other example, I saw it was terminated at 60%.
2. where is the below impact force comes from?in model file, I have applied a static -8660kN (x-direction) and -5000kN (y-direction) force at the impact joint. Why does the output shows smaller values?
Appreciate your help to solve my confusion.
Static Ship Impact analysis applies a load and incrementally increases the load until the kinetic energy of the vessel is absorbed. The load steps to achieve this are manually defined by the user and will not necessarily result with an exact 100% absorption percentage. Essentially this report is saying that the structure can absorb at least 100% of the required energy. Theoretically you could increase the load until the structure collapses and calculate a reserve strength ratio based upon the ratio between the ultimate load factor and the 100% absorption load factor. You could try tweaking the load increment to see the effect this has on the absorption %.
The energy absorption can terminate before 100% for a few reasons. If the structure collapses and/or cannot converge the analysis will stop. However, you should get warning/error messages when this occurs. Also, if the defined load and load factor is not large enough the analysis will end. You can try increasing the load factor in your collapse input file to see if you can get the analysis to reach 100%.
With regards to item 2, both loads are off by a factor of 2.38 (1/0.42). Is your initial load factor a fraction of the defined load condition?
Regards,
Geoff