Seismic Design Calculation p1 to p9

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API 650 10TH Ed. Addendum 4, Appendix E- Seismic Design ofStorage Tank

NOTATIONS:

Ai Impulsive design response spectrum acceleration coefficient, %gAc Convective design response spectrum acceleration coefficient, %gAv Vertical earthquake acceleration coefficient, %gD Nominal tank diameter, mFa Acceleration-based site coefficient (at 0.20 s period)Fc Allowable longitudinal shell membrane compression stress, MPaFty Minimum specified yield strength of shell course, MPaFv Velocity-based site coefficient (at 0.1 s period)Fy Minimum specified yield strength of bottom an nulus, MpaG Specific gravityGe Effective specific gravity including vertical seismic effects

= G (1 – 0.40Av)H Maximum design product level, mI Importance factor coefficient set by seismic use groupJ Anchorage ratioK Coefficient to adjust the spectral acceleration from 5% to 0.5% damping

= 1.50 unless otherwise specifiedMrw Ring wall moment, NmQ Scaling factor from the MCE to the design level spectral accelerationRwi Force reduction factor for the impulsive mode using allowable stress design

methodRwc Force reduction coefficient for the convective mode using allowable stress design

methodSo Mapped, maximum considered earthquake, 5 % damped, spectral response

acceleration parameter at a period of zero seconds(peak ground acceleration for arigid structure), %g

SDS The design, 5% damped, spectral response acceleration parameter at short periods(T = 0.20 s), %g

SS Mapped, maximum considered earthquake, 5% damped, spectral responseacceleration at short periods (0.20 s), %g

(t) Thickness of the shell ring under consideration, mm(ta) Thickness of the bottom plate under the shell extending at least the distance, L,

from the inside of the shell, less corrosion allowance, mm(tb) Thickness of bottom less corrosion, mm(ts) Thickness of bottom shell course les corrosion allowance, mmT Natural period of vibration of the tank and contents, secondsTC Natural period of the convective (sloshing) mode of behavior of the liquid,

secondsTL Regional-dependent transition period for longer period ground moti ons, secondsTO (0.20Fv/S1) / (FaSS)TS FvS1/FaSSwa Resisting force of tank contents per unit length of shell circumference, N/m

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wt Tank and roof weight acting at base of shell, N/mWc Effective convective (sloshing) portion of the liquid weight, NWi Effective impulsive weight of the liquidWp Total weight of the tank contents based on the design specific gravity of the

product, NWr Total weight of fixed tank roof including framing, knuckles, any permanent

attachments, NWrs Roof load acting on the tank shell, NWs Total weight of tank shell and appurtenances, NXc Height from the bottom of the tank shell to the center of action of lateral seismic

force related to the convective liquid force for ring wall moment, mXi Height from the bottom of the tank shell to the center of action of lateral seismic

force related to the impulsive liquid force for ring wall moment, mXr Height from the top of the tank shell to the roof and roof appurtenances center of

gravity, mXs Height from the bottom of the tank shell to the shell’s center of gravity, m(σc) Maximum longitudinal shell compression stress, Mpa

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Reference Tables

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