Issue: Z-coordinates in results do not match with storey levels

Issue

Z-coordinate values in summary storey results do not match the input values

Meaning

In Storey input, the listed levels are, typically, the Z-coordinate of each floor deck.

In Storey results, the listed coordinates are the position of the mass center of each storey, which includes the mass of the supporting members (half above and half below each floor).

Typically, as the bottom level has no deck, its mass center is located at 1/4 of the height of the storey (mass center of the lower half of the supporting members).

For the top storey, there are supporting members only below the floor, hence the mass center of the storey is located below the deck.

 

See more details in "Validation of modal analysis: specifics for IRS analysis"