Hi,

I am studying the response spectrum analysis with CAESARII. I found some strange description about summation method of response. The grouing method and ten percent method show different equation and description. For example, grouping method said "the response of any modes which have frequencies within 10% of each other first be added together absoultely, with the results of each of these groups then combined with the remaining individual modal results using the SRSS method". The equation said different meaning.

The equation said that results of all mode are summed using square. The group modes are summed absoultley with each other mode.

My questions are

1. The square sum should be used to sum the other mode that are not included in the grouping?

2. The absoultely sum should be sum with one by one not multiply with each other?

Please give me a piece of advice.