## General Mechanical

#### Multi-Point Response Spectrum

• lleonart
Subscriber
Hello, I am new to Ansys software and i am just about to begin using the student softwarenI am a student and currently studying the seismic response of a long span bridge. As we know, for a long span bridge, the conventional response spectrum, where ground motion is assumed to be uniform throughout the span, may not be applicable anymore. Thus, the use of Time History Analysis or Multiple-Support Response Spectrum (MSRS) is needed. Right now, i am focusing more on MSRS. This MSRS is based on the fundamental principle of random vibration theory and properly accounts the spatial variation of ground motion. Now I am looking for a software that is capable of doing this type of analysis and I found out that Ansys has this Multi-point Response Spectrum. So my questions are.n Is Multi-Point Response Spectrum of Ansys the same as the MSRS ?nWhat combination rule do the Multi-Point Response spectrum use to compute for the peak response of the structure?nIs there a manual or reference available out there where i can study this Multi-Point Response Spectrum?nnThank you n
• Daniel Shaw
Ansys Employee
A1: YesnA2: whatever combination rule that you specify.nA3: See Chapter 6 in the MAPDL Structure Analysis Guide (part of the Ansys Help System)nnn
• lleonart
Subscriber
Thank you for your response. nI've read the Chapter 6 for MPRS. I also like to add, is there a way where we can see the empirical formulas used by the Ansys. As I have noticed, Ansys uses SRSS, CQC, ROSE for combination rule in determining the mean peak response. Although in other literature, the combination rule use for MPRS consider the coherency function, cross-correlation equations, PSD etc., you may refer to Der Kiureghian's MSRS. So i just want to know if the combination rule by Ansys will automatically consider those additional parameters I have stated above or does the software follows the same procedure as Der Kiureghian's?.Thank you!nnThe combination rule for the mean of the absolute peak response (by Der Kiureghian)n