Energy Absorption Process during Dropped Object Analysis using SACS Collapse Advanced

I performed a dropped object analysis for object mass 0.41 mT falling from a height of 5 m height which is equivalent to energy 20 kJ. SACS energy graph shows 17.9 kJ energy was absorbed by the structure during drop object impact process.

The question then arises where is the reminder 2.1 kJ has gone? 

2.1 kJ is a energy leakage due to plasticization of members in the structural model?

What does SACS collapse module considers to arrive at net energy calculations in non-linear dynamic analysis?

Please clarify.

Grating_DRP_2.zip

Regards

Srikanth Vasa

Sr. Structural Engineer

  • Most likely the energy is lost due to damping. Try reducing the damping to ~0 (it will need to have some value above 0) and see if that changes the output for this chart.

    Note that the dropped object analysis calculates the energy absorption based upon the linear elastic structure in the dynamic response analysis and then Collapse analyzes the non-linear response to that linear elastic response. So this graph, which I believe is produced by dynamic response will not include any energy absorbed due to plastic deformation of the structure.