Title:Consolidate Self-Anchored Tanks
Date:July 29, 2013
Contact:Name : Don Comire
Company : Eastman Chemical Co.
Phone : (423) 229-3172
E-mail :
Purpose:Consolidate E.7.1. Anchorage and E.7.1.1 Self Anchored Tanks detailing requirements into section E.6.2.1.1 as E.6.2.1.1.3 and E.6.2.1.1.4, respectively.
Source:Ken Erdmann comment on ballot item 650-753 during Spring 2013 ballot cycle to delete E.7.1.2 since its contents have been moved to 5.12.5 and E.6.2.1.2.
Revision:0
Impact:The business impact of this item is neutral.
Background/Rationale:Situate existing API-650 Standard information next to other existing relevant sections, specifically for Self-anchored tank requirements. E.7.1 discusses anchorage where SDS > 0.05g, E.7.1.1 is SELF ANCHORED, and E.7.1.2 is MECHANICALLY ANCHORED. E.7.1.2 balances E.7.1.1, so to drop E.7.1.2 entirely because 650-753 moved its technical contents to 5.12.5 and E.6.2.1.2., E.7.1 and E.7.1.1 should likewise be moved to E.6.2.1.1.3 and E.6.2.1.1.4 by this new Agenda Item 650-1003. Further the consolidation effort by moving existing E.7.3.1 to E.6.2.1.1.5. Relocate existing E.7.9 Shell Support to be the new E.7.1, keeping all subsequent sections numbered as currently printed in section E.7 Detailing Requirements, from E.7.2 through E.7.8. (except for E.7.3.1 which is moving in its entirety).
Proposal:Additions shown in red, existing text in black. Deletions shown by blue strikethrough.
E.6.2.1.1.3 Tanks At GradeTanks at grade are permitted to be designed without anchorage when they meet the requirements for self-anchored
tanks listed in E.6.2.1.1.
E.6.2.1.1.4 Butt Welding Required for Annular Plates
For tanks in SUG III and located where SDS=0.5g or greater, butt-welded annular plates shall be required. Annular plates exceeding 10 mm (3/8 inch) thickness shall be butt-welded. The weld of the shell to the bottom annular plate shall be checked for the design uplift load.
E.6.2.1.1.5 Method for Estimating Tank Uplift
The maximum uplift at the base of the tank shell for a self-anchored tank constructed to the criteria for annular plates (see E.6.2.1.1) may be approximated by Equation E.6.2.1.1.5-1:
In SI units: yu = 12.10FyL2 / tb (E.6.2.1.1.5-1a)
Or, in US Customary units: yu= FyL2 / 83300tb (E.6.2.1.1.5-1b)
where tb = calculated annular ring t hold-down.
E.7.1 ANCHORAGE SHELL SUPPORT
Tanks at grade are permitted to be designed without anchorage when they meet the requirements for self-anchored tanks in this appendix.
The following special detailing requirements shall apply to steel tank mechanical anchors in seismic regions where SDS>0.05g.
Self-anchored tanks resting on concrete ring walls or slabs shall have a uniformly supported annulus under the shell. The foundation must be supplied to the tolerances required in 7.5.5 in order to provide the required uniform support for Items b, c, and d below. Uniform support shall be provided by one of the following methods:
- Shimming and grouting the annulus.
- Using fiberboard or other suitable padding.
- Using double butt-welded bottom or annular plates resting directly on the foundation. Annular plates or bottom plates under the shell may utilize back-up bar welds if the foundation is notched to prevent the back-up bar from bearing on the foundation.
- Using closely spaced shims (without structural grout) provided that the localized bearing loads are considered in the tank wall and foundation to prevent local crippling and spalling.
E.7.1.1 Self Anchored
For tanks in SUG III and located where SDS=0.5g or greater, butt-welded annular plates shall be required. Annular plates exceeding 10 mm (3/8 inch) thickness shall be butt-welded. The weld of the shell to the bottom annular plate shall be checked for the design uplift load.
E.7.1.2 Mechanically Anchored
See 5.12 and E.6.2.1.2 for requirements for mechanically anchoring a tank.
E.7.3.1 Method for Estimating Tank Uplift
The maximum uplift at the base of the tank shell for a self-anchored tank constructed to the criteria for annular plates (see E.6.2.1) may be approximated by Equation E.7.3.1-1:
In SI units: yu = 12.10FyL2 / tb (E.7.3.1-1a)
Or, in US Customary units: yu = FyL2 / 83300tb (E.7.3.1-1b)
where tb = calculated annular ring t hold-down.
E.7.9 SHELL SUPPORT
Self-anchored tanks resting on concrete ringwalls or slabs shall have a uniformly supported annulus under the shell. The foundation must be supplied to the tolerances required in 7.5.5 in order to provide the required uniform support for Items b, c, and d below. Uniform support shall be provided by one of the following methods:
- Shimming and grouting the annulus,
- Using fiberboard or other suitable padding
- Using double butt-welded bottom or annular plates resting directly on the foundation, Annular plates or bottom plates under the shell may utilize back-up bars welds if the foundation is notched to prevent the back-up bar from bearing on the foundation.
- Using closely spaced shims (without structural grout) provided that the localized bearing loads are considered in the tank wall and foundation to prevent local crippling and spalling.