2.2.           Selecting Target Modes

A critical component in any modal test is determining which modes will be measured and compared with analysis results. These are often referred to as target modes, and since all the analysis procedures presented here depend on a particular set of target modes we offer a brief discussion of methods for selecting these modes.

Often the target modes are separated into different sets. Primary target modes are the most important modes. These modes are critical to the accurate representation of the structure, and the highest level of scrutiny is applied to them. Secondary modes are less important, and typically lower accuracy requirements are applied to these modes. In some cases a set of tertiary modes are also identified. These modes are tracked, but typically no particular accuracy goals are applied to them.

There are three sets of criteria that are often used to select target modes as outlined below: