Comparison of Modal Superposition Methods for Response Spectrum Analysis

When calculating spectrum response of a box frame, it was discovered that the re sults depended greatly on the chosen methods of modal superposition. This thesis discusses several methods for calculating the response spectrum of a box frame under conditions of vibration with FEA methods. Focusing on this box frame, the results got from the modal superposition methods are compared against that got f rom time-history analysis, thereby some suggestions in choosing superposition me thods are given, as a ground for further calculations.