Wind Force & Moment for API-650 Storage Tanks

Thanks Mr. Abdel Halim Galala,

Your answer is for wind stiffener which are correct. But my question was how to calculate the wind force & moment for api-650 tanks. It is regading below as per api-650 11th edition add-1

5.11 WIND LOAD ON TANKS (OVERTURNING STABILITY)

5.11.1 Wind Pressure

Overturning stability shall be calculated using the wind pressures given in 5.2.1(k).

5.11.2 Unanchored Tanks

Unanchored tanks shall satisfy both of the following uplift criteria:

1. 0.6Mw + MPi < MDL /1.5

2. Mw + 0.4MPi < (MDL + MF)/2

where

MPi

= moment about the shell-to-bottom joint from design internal pressure,

Mw

= overturning moment about the shell-to-bottom joint from horizontal plus vertical wind pressure,

MDL

= moment about the shell-to-bottom joint from the weight of the shell and roof supported by the shell,

MF

= moment about the shell-to-bottom joint from liquid weight. The liquid weight (wL) is the weight of a band of liquid

at the shell using a specific gravity of 0.7 and a height of one-half the design liquid height H. wL shall be the lesser

of 0.90HD

In the above, there are Mw(Wind moment) & Wind force. How to calculate the terms of above. Is there any standard formulas are available.

Free download the attached link for a file in PDF format (10 Pages & 0.086 MB), and it will answer all of your questions.

Link: Storage_Tank_Design_Calculation - Seismic Design & Overturning Moment.

Thanks Mr. Abdel halim Galala.

It is very useful for me.

IS Appendix-V applicable for tank design external pressure having (-5) m bar(g). For that, do we provide vacuum stiffenig ring. Appendix v says as follows

V.1 Scope

This appendix provides minimum requirements that may be specified by the Purchaser for tanks that are designed to operate with external pressure (vacuum) loading as a normal operating condition. This appendix is intended to apply to tanks for which the

normal operating external pressure exceeds 0.25 kPa (0.036 lbf/in.2) but does not exceed 6.9 kPa (1.0 lbf/in.2).

Is normal operating pressure equivalent to design pressure. Can u guide me.

Dear sir

D = Nominal tank dia., ft

H₂ = Height of tank shell, ft

V = Wind velocity, miles/hr.

but we slove the equation : Z = 0.0001 D² H₂ (V / 100)²

Z = f³

Z = f² x f x (miles/hr)/(miles/hr) = f³

How to arrive in.³

^{please clarify}