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  1. sme75

    API 650 Anchor Chair Design Loads

    Section 5.12.6 refers to AISI Steel Plate Eng. Data for a guide on the design of anchor chairs. In this reference it recommends using 1.5 times the bolt load for the chair design. In section E.6.2.1.2 of API 650 it states that the anchor attachment design load is to be 3 times the bolt load...
  2. sme75

    Q235 vs Q345 Strength?

    Ian, If deflection is the source of your problem, a higher strength steel will not fix it. You will need to add stiffness to the piece to limit the deflection. It could also be just a bad paint job.
  3. sme75

    API 650 - Section F.4.1

    To add to the above question - If a tank has a 304 stainless shell and is reinforced with a carbon steel angle are you required to automatically use the lower yield strength of the stainless steel for the maximum pressure calculation even if the area of the carbon steel is say three times the...
  4. sme75

    API 650 - Section F.4.1

    The equation for the maximum design pressure was modified with the 2008 addendum. The variable Fy is described as the lowest minimum specified yield strength of the materials in the roof-to-shell junction. Is the value of Fy to be taken at the design temperature of the tank?
  5. sme75

    NFPA 68

    Lets say one has a bin with set dimensions and vent area. NFPA 68 can then be used to determine a value for Pred that allows the design conditions to work. Now what is the design pressure that should be used for the bin? Assume that deformation of the bin is not allowed. According to 6.3.1.2...
  6. sme75

    ASCE7-05 Redundancy Factor

    I am looking for opinions on what the appropriate redundancy factor would be for a tank supported by six legs with cross bracing. The seismic design category for the location is D. This would be a nonbuilding structure and in section 15.6 this factor is allowed to be taken as 1.0. My...
  7. sme75

    API 650 section 5.4.2

    Can anyone provide some background on the requirement of the bottom plate to project a minimum of 2" past the outside of the shell? I earlier editions of API 650 this distance was only required to be 1". Does anyone know the reason for increasing the distance?
  8. sme75

    Standard F&D Head

    Are standard F&D heads typically used for a pressure vessel of up to 25 psi? If so, what formulas should be used to calculate the required thickness? Looking at the ASME formulas and the small knuckle radius typically found on the standard heads, seems to indicate that the M factor will be...
  9. sme75

    Section E.6.1.4, API 650

    I noticed that the coefficients on the equations for Ni and Nc have changed between Addendum 4 of the 10th edition and the 11th edition. Does anyone know the reason for the change and what effects the changes have on the calculated loads? Also, in equation E.6.1.4-4B two new variables are...
  10. sme75

    0.6D + 0.7E

    So is this a check to simply address overturning stability? Do we need to review the soil bearing pressures for a footing that is subjected to a vertical load and a moment? By reducing the dead load, the eccentricity is increased and will require a larger footing than would be required to...
  11. sme75

    0.6D + 0.7E

    Lets say that an analysis of a frame gives you an uplift force at the base of a column for the load combination of 0.6D + 0.7E. Now to size the footing are you required to multiply the weight of the footing and any soil above it by 0.6 to calculate the uplift resistance?
  12. sme75

    Wind Design Pressures

    Design pressures at wall corners and roof edges calculated per ASCE 7 are to be applied over a distance a. This is listed as 0.1 x width, 0.4h, minimum of 3 feet. In the 1997 UBC this used to be limited to a maximum of 10 feet. Is ther a similar maximum now in ASCE 7?
  13. sme75

    API 650 Appendix V

    In section V.1 of the appendix it states that it is intended to apply to tank with a normal operating external pressure exceeding 0.25 kPA, but less than 6.9 kPa. What about when the tank has an operating external pressure of 0.0 kPa and a design external pressure greater than 0.25 kPa? The...
  14. sme75

    API 650 Supported Cone Roof

    You design parameters will dictate whether or not a center column is necessary, but if you do not have significant internal or external design pressures there is no reason that a center column would be required. Assuming that this is a new tank, a diameter of 15 meters can easily be spanned...
  15. sme75

    Pressure vessel stiffener rings

    The Pressure Vessel Handbook by Eugene F. Megyesy should give you what you need to check for the external pressure and fit your budget
  16. sme75

    tank roof uplift

    Thanks for the discussion. I will look into the latest addendum of API 650, I have been waiting for it to come out to at least close the gap between ASCE and it on the seismic loads. It looks like they have also addressed this issue as well
  17. sme75

    tank roof uplift

    Tankdude, I have already done what you describe and this is not what I am asking. I am asking if there is any requirement to design the roof for a vertical uplift force due to wind. This would act similar to an internal pressure and lift up on the roof. This is typical in building design...
  18. sme75

    tank roof uplift

    I agree that this is overly conservative and that the tank is not going to go anywhere, however I can't seem to convince the foundation designer/customer that this is the case. They want to see sliding calculations for an empty tank with wind uplift on the roof. The tanks are anchored for...
  19. sme75

    tank roof uplift

    IFRs, In this case the roof is a 15 degree cone with external stiffeners. Do you feel that coefficients for a domed roof would apply in this situation? As JStephen mentioned, API, AWWA, and ASCE all give lateral design forces, but do not address uplift on the roof of tanks. The question...
  20. sme75

    tank roof uplift

    Is it typical to dsign for an uplift, due to wind, on the roof of storage tanks? API 650 and AWWA D-100 do not seem to address the topic, they just give a formula for the lateral load. In fact the anchorage calculations in section 3 of API 650 do not include an uplift due to wind in table...

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