Notions of structure

    It is not always necessary to calculate the structure for all 8 combinations. For example, for the analyzed structure symmetrical to the X axis, combination 1 produces in the frame from axis 1 similar effects as combination 2 in the frame from axis 4. Thus, the structure can be calculated only for one of the two combinations. Similarly, it is observed that if the structure is symmetrical and the X-axis face and the Y-axis face, of the 8 combinations represented, only two are sufficient to determine the most unfavorable effects of the seismic action in the structure.

      The 8 seismic combinations must in turn be combined with the combination comprising the gravitational actions with the long-time value. This results in 8 combinations that include seismic and gravitational action. These combinations are called design seismic combinations. In addition, the structure must also be calculated for the fundamental grouping of actions that includes only gravitational actions with maximum probable values ​​(factorized above unit). The general scheme of combinations of actions for structural calculation is given in the following figure.