My textbook says for mode combination, the peak value $r$ of each response quantity is determined by combining the peak values $r_n$ of the modal contributions to the same response quantity.
From what I understand, this means that we have to calculate the response (be it displacement, the difference in displacement, the forces or moment) for each mode first, before we apply the modal combination method such as SQSS, CQC and ABS in order to obtain the total response.
This is also verified by the numerical example in the textbook.
However, in the textbook example, all the members are 1-element members, easy to interpret the above clause in the textbook. What about members (beams, columns) that are of more than one element? In FEM we often create a single member out of multiple elements.
Do we combine the element response into member response on per mode basis first, before we combine all the member modal responses into total member response?
Or do we combine the total modal response for each element, and then only combining the element response into member response?
In other words, is the modal combination done at element level or at structural member level?