Περιβάλλουσες Φορτίσεις

The main horizontal seismic force H_X is applied at each diaphragm of a building due to the seismic action along the axis X of the building. This force is applied at the diaphragm’s centre of mass C_M and generates the moment M_CTΧ of magnitude |H_X×e_oY| about the centre of stiffness C_T. The same situation exists  for the Y axis where the corresponding moment M_CTY has a magnitude equal to |H_Y×e_oX|. The sign of seismic forces changes continuously resulting in combinations having either positive or negative values of them. The magnitude of bending moments depends however on the size of the structural eccentricities e_oX, e_oY. The position of the centre of stiffness and thus of the structural eccentricities is examined in §5.4 and in the Appendices C and D.

Figure 6.5-3 B: +1.00EX + 0.30EY		Figure 6.5-4 C: +1.00EX - 0.30EY		Figure 6.5-5 D: +0.30EX + 1.00EY		Figure 6.5-6 E: -0.30EX + 1.00EY
Figure 6.5-7 F: -1.00EX - 0.30EY		Figure 6.5-8 G: -1.00EX + 0.30EY		Figure 6.5-9 H: -0.30EX – 1.00EY		Figure 6.5-10 I: +0.30EX – 1.00EY

Regardless of the C_M, C_T locations the combination A of gravity loads g and q multiplied by the safety factors of actions always exists . For any specific location of C_M, C_T, 8 additional combinations of the seismic forces exist, due to the most probable masses 1.00g+0.30q during the earthquake.