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2.2.1 Earthquake action and action effect:
F —Earthquake action of the electrical equipment（structure）；
m —Mass of the electrical equipment；
m i —Mass concentrated at mass point i under operating conditions；
M —Bending moment；
T —Natural vibration period of the structure；
T g —Characteristic period of ground motion；
σ —Tensile（compression）stress；
τ —Shear stress；
g —Acceleration of gravity.
2.2.2 Material performance
E —Modulus of elasticity of the material；
K —Lateral rigidity of the system；
σ —Tensile（compression）stress；
τ —Shear stress；
［ σ ］—Design allowable stress；
［ τ ］—Design allowable shear stress.
2.2.3 Geometric parameters:
A —Area of cross section；
d —ID of circumferential cross section；
D —OD of circumferential cross section；
H —Height of the structure；
H i —Calculated height of mass point i ；
I —Second axial moment of area；
W —Modulus of section；
Z —Area moment of inertia.
2.2.4 The factors and coefficients used in calculations:
k —Unbalance factor；
α —Seismic influence factor；
α max —Maximum seismic influence factor；
β —Floor dynamic magnification factor；
λ —Rigidity reduction coefficient；
r —Modal participation coefficient.