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The modal combination method is applied separately for both stages . It is also applied in two stages in accordance with the Article 4.3.4.4 of the TBDY, in the systems with no-beam slab that includes a basement, Modal Response Spectrum Analysis of Structures with Basement Buildings with Modal Analysis .
In the picture below , moment values occurring in the columns as a result of the earthquake calculation with the modal combination method of a building with no beams are shown. The calculation on the left side of the image is the results obtained as a result of the first stage calculation (both ends of the columns are articulated). As can be seen, there is no moment value because the two ends of the columns are hinged. The calculation on the right is the results of the second stage calculation. As you can see, as the columns are connected monolithically, moments occur at the column ends.
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All elements are designed according to the most unfavorable case of internal forces occurring under all the loading combinations described above.
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