2.2.1 Action and action effect
F t ——design value of hoop tension per unit height of ringwall;
F t0 ——design value of hoop tension per unit height of outside ringwall;
f a ——modified characteristic value of subgrade bearing capacity;
F k ——vertical force transferred to foundation top surface from the upper structure corresponding to nominal load combination;
G k ——combined self-weight of foundation and weight of soil on foundation;
g k ——nominal value of the vertical linear distributed load transferred to ringwall top from bottom of tank shell;
M R ——Sliding resistant moment;
M s ——Sliding moment;
P k ——average pressure value at foundation bottom surface corresponding to nominal load combination;
P 0 ——additional pressure at the calculation bottom surface of tank foundation corresponding to quasipermanent combination of load effects;
S ——final settlement of subgrade;
Δ S i ′——settlement of No.ith stratum soil layer within the range of calculated depth;
Δ S n ′——Calculated value of deformation for the soil stratumΔ Z ,which is taken upward from the calculated depth.
2.2.2 Calculation indicators
E s i ——compression modulus of No.ith soil layer under the bottom of tank foundation;
E s0.1-0.2 ——compression modulus of subgrade soil under pressure at 100kPa-200kPa;
f ak ——characteristic value of subgrade bearing capacity;
f y ——design value of tensile strength of ordinary steel rebars;
γ c ——gravity of ringwall;
γ L ——gravity of service fluid stored in tank;
γ m ——average gravity of the packing material of each layer inside ringwall;
γ w ——Gravity of water.
2.2.3 Geometric parameters
A ——tank foundation bottom surface area;
A s 、 A s0 ——sectional area of circumferential rebars per unit height respectively of ringwall and outside ringwall;
b ——width of ringwall;
b 1 ——distance from the inner side of outside ringwall to the inner side of tank shell wall;
D t ——inner diameter of tank bottom shell;
H ——height from tank bottom to outside ringwall bottom;
h ——height of ringwall;
h L ——height from ringwall top to the maximum fluid(medium)level in tank;
h w ——height from ringwall top to the maximum water level in tank;
i ——slope;
R ——radius of center line of ringwall or outside ringwall;
R h ——inner radius of outside ringwall;
R t ——inner radius of tank bottom shell.
2.2.4 Calculation coefficients and others
K ——lateral pressure coefficient at ringwall;
α - i ——coefficient of average additional stress;
β ——coefficient of the width extended from tank shell into ringwall top;
γ ——component coefficient of self-weight of tank;
γ 0 ——Importance factor;
γ Qm ——component coefficient of the packing material self-weight in each layer inside ringwall;
γ Qw ——component coefficient of water self-weight;
ψ s ——empirical coefficient for settlement calculation.