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Additional Eccentricity Modelling

  • As required by , the earthquake calculation is made automatically in every 4 cases by shifting the storey masses by 5%.

  • In accordance with Article (b) , the horizontal earthquake loads are calculated automatically by shifting (+) and (-) 5%.

  • In modeling the additional eccentricity effect, any of the static and dynamic methods that comply with the regulation can be used for analysis. Method selection is under user control. - Additional eccentricity effect is defined in order to take into account possible uncertainties in the effect of earthquake ground motion on the building and in the stiffness and mass distribution of the structural system . - In case floor slabs are modeled as rigid diaphragm in their own plane according to

(a) According to , an earthquake calculation will be made in the direction of each earthquake based on the floor mass defined in the floor mass center ( main node point ) .

(b)     Horizontal seismic loads affecting the center of the storey mass ( main node ) will be shifted by + 5% and - 5% of the floor dimension perpendicular to the earthquake direction considered, and earthquake calculation will also be made for these cases.

(c)    seismic analysis of 4/7 in case of 'according to instead of shifting the modeling For ease of seismic loading, the floor mass center ( master node ) effect the lateral force F i A (X) with Eq. (17.4) with the additional layers torsion ' It is appropriate to consider. 

Here e indicates 5% additional eccentricity. 

(d)   seismic analysis of 8.4 according to the case of modal method instead of shifting the seismic loads in terms of modeling simplicity, the floor mass center ( master node ) is defined times the mass of m i with, floor mass moment of inertia m 'or Eq. (4.18) It is convenient to add the increment Δ m given by . - In case earthquake calculation is made under the effect of unidirectional earthquake according to 4.7 or 4.8.2 , additional eccentricity is taken into consideration for each direction. If the calculation is made under the effect of two-directional earthquakes acting simultaneously according to 4.8.3 , the eccentricities for both directions will be applied separately. - In case floor slabs are modeled with two-dimensional plate ( membrane ) finite elements to contain the degrees of freedom related to the displacements in their own planes according to

(a)   With this model created, earthquake calculations will be made without the effect of eccentricity, and internal forces and displacements will be obtained in floors and bearing system elements other than floors. The sizes obtained for flooring will be taken into consideration in flooring design.

(b) In  order to consider the eccentricity effect, the rigid diaphragm assumption will be made for in-plane finite element degrees of freedom and the storey mass centers will be shifted as defined in . A second earthquake calculation based on rigid diaphragm modeling will be made to determine the effect of additional eccentricity on structural system elements other than slabs and beams. 

(c) For structural   system elements other than slabs and beams, the design essential internal forces and displacements will be determined as the envelope (unfavorable) of those obtained in (a) and (b) .

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