Response spectrum dynamic details

Unlike most other analysis options derived results from a response spectrum analysis cannot be derived from the basic response spectrum results. Instead the derived modal results must be calculated and then these combined.

Definition

Storey drifts

Storey drifts can be specified at various locations. A storey drift is identified by a name, a location in the global xy plane and a list of storeys that are included. By specifying storeys it is possible to carry out drift calculations where storey levels may be different in different parts of the structure.

Relative nodal displacements

In a response spectrum analysis relative displacements cannot be calculated from the difference in the response displacements at the nodes but need to be calculated from the relative modal displacements. The relative nodal displacement is specified by a name, a pair of nodes and an axis for the output.