Question

My questions is regarding capturing member dent energy absorbed in a static ship impact analysis. The collapse manual says that IMPACT line is executed only once per collapse run. So, does it mean that member dent energy can be captured at impact on only 1 joint? What if the ship is hitting at multiple joints and we need to capture member dent energy at multiple points during ship impact? Please advise.

Answer

Collapse Advanced currently supports only a single IMPACT input line per analysis. If multiple IMPACT lines are included, the program will only process the last one and ignore the rest.

There are two ways the IMPACT line can be used: 

1. Ship impact mode - Impact Joint specified on the IMPACT line

• The energy absorbed by the structure is computed based on the force and displacement at the single defined impact joint entered on the IMPACT line. 
• Dent energy is calculated only for the member connected to that specific joint.
• Only one impact location is supported in this mode

2. General impact analysis (like Dropped Object) - Impact Joint left blank

• Structural energy absorption is computed at all loaded joints in the impact load case. In other words, we can model multiple-point impact.
• Dent energy calculation is not calculated in this mode.

If you want to model multiple-point impact, you must provide a single IMPACT line with no joint name. However, note that you will not get the dent energy anymore. To obtain dent energy at multiple impact locations, the correct workflow is to perform separate Collapse analyses, each with its own impact joint and dented member. This is the current intended behavior of the software.