Practical Considerations in Modal Transient Response Analysis and Response Spectrum Superposition

Practical guidelines for transient response calculation and peak response estimation for linear structural dynamic systems are described and illustrated. The response spectrum of the dynamic excitation environment is utilized to clearly define the low frequency dynamic response range and the high frequency quasi-static response range. Low frequency dynamic behavior is described by superposition of modal transient responses in that range while high frequency quasi-static behavior is approximated by residual vector response. For the task of peak response estimation, a sensible “vectored” approach to modal response spectrum superposition is introduced. This technique is shown to provide a more reliable estimate than currently popular summation approaches.