Use of Different R and D Coefficients for Upper and Lower Pats of Structures with Basement

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4.3.6. Using Different R and D Coefficients in Upper and Lower Sections of Buildings

In buildings where different R and D coefficients are used in the upper and lower sections , calculations will be made according to the rules given in 4.3.6.1 or 4.3.6.2 . According to the definition given in 3.3.1 , these rules can also be applied in buildings with basements surrounded by rigid walls. Alternatively, calculations can be made according to the rules described in 4.7.5 or 4.8.5 .

With the Equivalent Earthquake Load Method explained in 4.3.6.1 - 4.7 , in the calculation made by considering the entire carrier system ( upper section + lower section );

(a) the top section wherein the structural elements corresponding to the ductility internal forces reduced to upper table (4.1) from the selected R _top and the D _top coefficients and considering the received (X) the natural vibration period prevails in the earthquake direction T _p ^{(X )} 'e substituted by Eq. (4.1) from the calculated Seismic Load Reduction Factor (R _a ) _top will be obtained using.

(b) The reduced internal forces corresponding to the non-ductile behavior of the carrier system elements in the upper section will be obtained by multiplying the internal forces obtained in (a) with the _upper coefficient D.

(c) The equivalent earthquake load reduction coefficient (R _a ) for reduced internal forces corresponding to the ductile behavior of the structural system elements in the _subsection shall be determined by _Sub Equation (4.4) :

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The coefficient ν ^{(X) in} this equation is given below:

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Eq. (4.5 A) 'in the first term ν _top ^(X) , the upper portion from the lower portion ' E transmitted reduced forces, the second term (X) ν _lower ^(X) The subsection 'to calculate the reduced forces generated by its own vibration corresponds to the coefficients used. Seismic Load Reduction Coefficient calculated from Equation (4.1) depending on R _sub and D _sub- coefficients selected from Table (4.1) and T _p ^(X) for the carrier system in _sub- subsection (R _a ) It shows. ν _top ^(X) is defined as the ratio of the base shear force of the upper section to the base shear of the entire load-bearing system ( upper section + lower section ) under unabated seismic loads .

(d) The reduced internal forces corresponding to the non-ductile behavior of the structural system elements in the subsection shall be obtained by multiplying the internal forces obtained in (c) by the equivalent strength excess coefficient defined below :

With the Modal Calculation Methods explained in 4.3.6.2 - 4.8 , the calculation made by considering the entire carrier system ( upper section + lower section ),

(a) All operations in Equation (4.4), Equation (4.5) and Equation (4.6) shall be applied for each n th vibration mode and taking into account the relevant natural vibration period T _n . In the nth mode , instead of the ratio of base shear forces in Equation (4.5b) , the ratio of modal effective masses corresponding to these shear forces in the same mode can also be used (See 4B.1.4 ).

(b) R is _lower <R _top in rigid basement systems which, for all modes of Eq. (4.5b) from the ν _{n, parent} ^(X) 'in case of avoiding to calculate always gives less favorable results ν _{n, parent} ^(X) = 0 can be assumed. In this case, the following simplifications can be made for the subdivision in the n'th mode:

D _sub = 1.5 for basements according to 4.3.2.3 .