The default setting is to use the resonant simplified (fast) calculation with all nodes considered as an excitation node and the response calculated at the vertical DOF at the excited node only. This is generally the fastest combination to get reasonable results calculated for the entire floor. This combination generally captures the most critical effects in each region, but doesn’t well pick up the extent of the response in each critical region. This is because the worst case response at some nodes near the critical nodes would be from excitation of the nearby critical node and not from self-excitation. However, the default setting is very recommended for daily design use for structures that are not vibrationally sensitive. In order to better pick up the critical effects of the entire region, the "Response Nodes" setting could be changed to Vertical DOF at all nodes, but there will normally be a considerable increase in runtime.

For structures that are vibrationally sensitive or if a higher degree of accuracy is desired, the modal analysis method is recommended. Because this method is computationally expensive, it is generally necessary to use it in conjunction with other settings to speed up the calculation time. One such example is to use the simplified method to evaluate the floor as a whole, then excite and evaluate a subset of the structure using modal analysis. This can be accomplished by using the “Critical Nodes” option and setting the Excitation response factor threshold to avoid exciting non-critical nodes, by drawing excitation areas to take advantage of known areas of excitation like corridors and hallways, or a combination of the two.