2.2　Symbols

2.2.1　Actions and action effects：

Fji——characteristic value of horizontal earthquake action of the mass point i under the vibration mode j；

Fek——characteristic value of total horizontal earthquake action of structure；

Fi——characteristic value of horizontal earthquake action of mass point i；

Fn——additional horizontal earthquake action on the top；

Gi，Gj——representative value of gravity loads concentrating on mass point i and j respectively；

Geq——representative value of equivalent total gravity loads of structure（equipment）；

SE——earthquake action effect（bending moment，axial force，shearing force，stress and deformation）；

S——fundamental combination of earthquake action effect and other load effects；

SK——effect of characteristic action and load；

SEK——effect of characteristic horizontal earthquake action；

Sj——horizontal earthquake action effect under the vibration mode j；

M——bending moment；

N——axial force；

V——shear force induced by earthquake action.

2.2.2　Resistance and material performance：

Ec——elastic modulus of ceramic bushing；

Kce——bending-resistance rigidity of ceramic bushing；

R——design bearing capacity of structure（equipment）members；

K——rigidity of structure（equipment）members；

σtot——total stress induced by earthquake action and other loads；

σv——failure stress of equipment or material.

2.2.3　Geometrical parameters：

H0——height of gravity center of electrical facility system；

h——height of calculated section from the bottom；

Hi，Hj——effective height at mass points i and j respectively；

hc——height of cementing between ceramic bushing and flange；

Ic——inertia moment of section；

dc——outer diameter of ceramic bushing at the cementing position；

Lc——length of beam；

te——clearance between flange and ceramic bushing.

2.2.4　Calculation coefficients：

ζ——damping ratio of structure；

γ——attenuation coefficient；

η1——adjustment factor of the slope of the linearly declining section in the curve of seismic influence coefficient；

η2——adjustment factor of damping；

γRE——adjustment factor of seismic bearing capacity；

α——horizontal seismic influence coefficient；

αmax——maximum value of the horizontal seismic influence coefficient（the value when the period T=0.0.40αmax corresponds to a dynamic magnification factor of rigid structure of 0）.

2.2.5　Others：

ao——design basic acceleration of ground motion；

g——gravitational acceleration；

a——horizontal acceleration of ground motion time history；

as——maximum horizontal acceleration of ground motion time history；

T——natural period of vibration of system（structure）；

f——fundamental frequency of system（structure）in the test direction；

Tg——characteristic period；

TP——time interval between sine beats；

Xji——relative horizontal displacement of mass point i in X direction under the vibration mode j；

Yji——relative horizontal displacement of mass point i in Y direction under the vibration mode j.