Parameters of a structure seismic analysis depend on a seismic code used during calculations of a structure influenced by seismic impact. Select Algerian seismic code RPA 2024 in the New Case Definition dialog or click Parameters in the Analysis Type dialog.
To complete the seismic analysis according to the rules given in a code, define the following parameters:
- Zone - The Seismic zone number given in the code, clause 3.1, the value is assigned according to the choice of seismic zone. For determining design seismic force, the country is classified into seven seismic zones (0 to VI) as shown in Figure 3.1. The selection of the zone determines the value of acceleration parameter A, according to Table 3.2.
- Site - For determining the correct spectrum to be used, the type of soil on which the structure is placed shall be identified by the classification given in clause 3.2, as Soil type S1, S2, S3, S4. The selection of the site determines the value of site parameter S, and characteristic period for spectrum definition T1, T2, T3, according to Table 3.3 and 3.4.
- Importance group - the classification of the structure importance group is given in clause 3.4, and the importance factor I value is assumed according to Table 3.10.
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Quality coefficient - Quality factor is determined according to the Equation (3.23) QF = 1 + Σ Pq depending on criteria classified with Table 3.18. Click Define button to choose Category and not observed criteria, quality factor is calculated accordingly.
- Behavior factor - specify the value of the Behavior factor according to point 3.6. Determine the value according to Table 3.17 depending on the structure type.
The Behavior factor is a reduction factor of the design response spectrum in relation to the elastic response spectrum. You can edit its value after selecting the Design spectrum option.
Note: The behavior factor q reduces the design spectrum; this way it also decreases seismic loads and the resulting internal forces. However, the displacement based on the design response spectrum is multiplied by the behavior factor q. Thus, usually such displacement is not reduced in relation to the elastic response
Spectrum for response analysis method
The Elastic horizontal seismic acceleration is based on the above factors, according to the formula given in clause 3.3.1.
The Elastic vertical seismic acceleration spectrum is determined accordingly by the clause 3.3.1 Equations (3.14).
To avoid explicit nonlinear structural analysis during calculations, a structure's ability to dissipate energy, primarily through its ductile behavior, is considered by performing an elastic analysis based on a response spectrum reduced compared to the elastic one, called the design spectrum. This reduction is achieved by introducing an elastic force reduction factor, called the structural behavior coefficient, R, as well as a penalty factor called the quality factor, QF.
The Design seismic acceleration spectrum is based on the above factors, according to clause 3.3.3.
Additional button Base Shear opens a dialog where you can determine how to scale resulting forces obtained as combinations between dynamic modes. According to clause 4.3.5 base shear estimated by the Response Spectrum Method shall not be less than 80% of the design base shear calculated using a fundamental period Ta as per Equation 4.4. You may choose different options to define fundamental period Ta or design base shear force value. Pay attention that internal forces, stresses and reaction will be scaled so that sum of reaction for quadratic combinations is equal to the design base shear.
In the lower part of the dialog, the Direction definition and Filters buttons are located.
The details concerning this structure analysis method can be found in the mentioned code of standard RPA 2024 D.T.R. - B.C.2.48.
You can examine all the input parameters and spectrum values in the Calculation Notes (open Analysis 
Calculation Notes Simplified/Full Note).