Question: While running Spectral Earthquake in SPLOAD line when selected CQC modal combination option no error is reported but when SRSS option is selected runtime error is observed.

Answer: If modes are completely independent, then only SACS can proceed for the SRSS combination. When structure is not producing independent modes, SACS internally calculates the correlation factor. As SRSS combination does not have any correlation factor, SACS will report the error. For dependent modes, CQC is the valid approach of mode combination and SACS will provide the desired results. For further details, refer Section 3.1.3 of SACS Dynamic Response Manual. A snap of the same is attached.