Do Analysis with Mode Combining Method
The Mod Modal Combination Method is chosen for the building as a result of the necessity to be analyzed with the modal analysis method in accordance with Table 4.4 of TBDY 2018.
Since the building has basement storys, it is difficult to provide sufficient mode numbers, the mass participation rate of 95%, to be taken into consideration in the Mod Modal Combination Method for the entire upper section above the rigid basement walls and the lower section containing the basement floors. For this reason, in TBDY 2018 4.8.5.1, two stage analysis is done with modal calculation methods.
In this method, the upper part of the building and the lower part with basement are modeled together as a common structural system and two stage analysis is done. In both load cases, a mass participation ratio of 95% should be achieved.
There are two stages in the analysis of the upper section and the basement floors, as the building consists of special sherawallsherawalls. The first stage is the hinged modeling of the columns from the lower and upper ends, and the second stage is the monolithic modeling of the elements.
In addition, due to the dynamic method of solving Torsional Eccentricity Effect in the program, 4 modal analyzes are made for each stage.
In accordance with TBDY 2018 4.5.10.4 article, it is applied in a full rigid solution to determine torsional eccentricity effect inslabs in slabs with semi-rigid diaphragm adopted as a shell.
Due to all seismic code requirements listed above, a total of 20 modal analyzes are made for this building and the internal forces to be used for the design are determined.
Upper Section Analysis (First Stage
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In the first load model, a common structural system model is established, that is, the entire structure is modeled. The masses of the basements are taken as '0' and their stiffness is used in the mathematical model, while both the mass and stiffness of the basement floors are included in the mathematical model. As a result of this analysis, internal forces are obtained in both the upper section and the basement floor elements.
First of all, the item summaries of the analyzes made with the symbols used by the program are explained in the table below.
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