In Appendix C of the 1999 SEAOC Blue Book, the text refers to "the effective
first mode weight, which would be on the order of 0.7W" (under "Dynamic
Response Modification"). What is the basis for this statement? Why is the
"effective weight" less than W for the first mode? Is this further explained
anywhere else in the Blue Book or other available references?
William C. Sherman
Camp Dresser & McKee, Inc.