18.9. Modal Combination Techniques

Try these first

1. 1.

   What does SRSS stand for?

   Hint

   Think about combining squares of values.

2. 2.

   When would you use the CQC method?

   Hint

   Consider phase relationships.

3. 3.

   Which method is used when the modal frequencies are well-separated?

   • SRSS
   • CQC
   • Both

   Hint

   Think about their separation in terms of correlation.

4. 4.

   The CQC method is necessary for which type of scenarios?

   • True
   • False

   Hint

   Recall what phase relationships affect.

5. 5.

   Given three modal responses: R1 = 10, R2 = 7, and R3 = 5; apply both the SRSS and CQC methods if ρ_12 = 0.5, ρ_13 = 0.3, ρ_23 = 0.4.

   Hint

   Set up the systems cleanly to ensure correlation checks are accounted for.

6. 6.

   If a building's two closest modes show high correlation, discuss how it could affect your selection of SRSS vs CQC.

   Hint

   Think about the phase and how strongly they interact with each other.