Below are the steps involved in adding eigen vectors in the frequency domain in order to get to a time response.

First is getting each of the eigen vectors for each active node for each mode.

Figure 1: Frequency response per mode of node 2 of five element beam

Next is adding the modes together to simulated frequency response function (FRF) for that node.

Figure 2: Frequency response for node 2 of 4 element beam

Third is repeating this process for all of the other nodes.

Figure 3: Frequency Response for 4 element beam

Finally is taking the inverse transform - taking the FRFs back into the time domain.

Figure 4: Time response for 4 element beam