The frequency is calculated by a simplified method using the following equation:

Fz 18/sqrt (deflection) the deflection is based on the full composite section using the short term modular ratio under Dead Load and 10% of the Live Load. Ig may be increased 10% to account for increased stiffness of the beam under dynamic loading, such as for the effects of continuity. If the size fails the specified limit, a larger size will be used when optimizing beam sizes. A value of 0.0 specified for the minimum frequency means that there is no minimum limit on the frequency; specify 0.0 if the simplified vibration approach is not to be used.