ML19259C745
| ML19259C745 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/05/1979 |
| From: | Barker D HOUSTON LIGHTING & POWER CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| ST-HL-AE-359, NUDOCS 7908150104 | |
| Download: ML19259C745 (4) | |
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rl it E!ectdc Tower July 5,1979 L/ 3 pp fA RO Box F20 ST-HL-AE-339 Houston. Texas 77001 SFit :
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Director, Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive, Suite 1000 A.lington, Texas 75102
Dear Sir:
South Texas Project Units 1 5 2
['ocket Mos. STN 50 '98, STN 50-499 IE Bulletin No. 79-02, Revision 1 Bulletin No. 79-02, Revisior 1, received June 25,1979, has been reviewed by Houston Lighting, Power Ccmpany. The requirements of the Bulletin have been addressec, and the appropriate procedures are being followed. Those being deve aped in response to the Bulletin are described in the enclosed attachment.
If you have any questions, please contact us.
Very truly yours,
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D. G. Barker, Manager Soutn Texas Project PLW/bp Attach: ent cc:
Director, '4RC Office of Inspection & Enforcement C. Thrash (Baker & 20tts)
R. Gordon Gooch (Caker & Sotts)
J. R. Newran (Lowenstein, Newman, Reis, Axelrad & Toll)
A. J. Granger R. A. Fra:ar
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Recly to NRC IE Bulietin 79-02 Rev. 1 Item 1.
The flexible behavior of a base plate causes the concrete expansion anchor bolt to experience a higher load than an externally applied tensile lead, HL&P procedure to assess the prying force is as follows:
a.
The prying force is calculated using the equation for A490 bolts gnen on page 4-81 of the AISC Nnual r;f Steel Con-str action (Seventh Edition).
b.
The design prying force is determined by mult' plying the above force by a factor of 1.5.
Item 2.
Only wedge and sleeve-type anchors are allowed to be used at the South Texas Project.
The minimum f actor of safety used between the bolt design Icad and the bolt ultimate capacity from static load tests is 4.0.
This is consistent with the requirement of the IE Bulletin 79-02 Rev. 1.
The effects of shear-tension interaction minimum, edge distance and bolt spacing are taken into account in the following manner:
a.
Shear-Tension Interacticn Allowable working loads for ccmbined tension and shear are checked to satisfy the following interaction equation:
T S
acclied acclied l.0 T
b
~
allowable allowable Where T and S are allowable pure tensile and shearf8rb65hr$spectigpybb$tethattheallowableworking loads are not increased for accidental or severe envirccmental conditions.
b.
Edge Distanca anc Bolt Spacing The minimum concrete edge distance (i.e., the distance to tne edge of the concrete frcm the center-line of :ne ex:ansion bolt) is deter-iced frca the fciicwing considerations:
i) Tension:
f 20 \\
Edge distance ut
=
i So (f ' gh ii) Shear:
D
'ut Edge distance
=
7.5(f')
c Where:
0 = ncminal diameter of anchor, in.
n.w-
$ f.s 4 Y l-
f'
= specified compressive strength of concrete, c
psi.
f
= minimum specified tensile strength of anchor ut steel, psi.
If the bolt is under ccmbined shear and tension, the higher of the above two values governs.
The expressicns of edge distances are obtained frca Section 8.7.1.1 of Reference 1.
The minimum spacing between two expansion bolts is normally twice the embedment length. Minimum embedment length is determined as the greater of the folicwing two considerations:
i) 4.5 times the diameter of bolt.
The embedment de,th is such that the wedges of the expansion ii) n bolts are in the confined areas between or benind the rebars.
Under such ccnditions no redustion in ultimate bolt strength is deemed necessary.
Bolt strength is reduced en a straight-line basis down to 50% at a spacing equal to the embedment length (see Ref. 2).
In no case will spacing less than the embedment depth be allcwed.
Item 3.
Safety-related piping systems are analyzed for dynamic loads such as seismic loadings, water harrer, steam hamner, safety relief valve discharge, etc.
Equivalent static pipe support design leads are then determined for the above Icads as applicable. The anchor bolts are thus designed to withstand these loads. A test program for wedge and sleeve type anchor bolts (Ref. 3) has concluded that the dynamic load capacities of such expansion bolts are about tne same as their corresponding static load capacities.
However, as an added measure of conservatism, en safety-related piping systems the factor of safety of 4.0 given in response to Question No. 2 above is increased to 5.0 to account for the effect of cyclic loads.
Item 4.
Cn STFEGS, no expansicn anchcr bolts have been installed en safety-related piping systems at the present time.
GC procedures are being establisned to document tnat the design requirements are met for each expansicn anchor bcit, i.e., to include cyclic leads and Colt prelcad.
The bol: preload is to be equal to or greater than the design load.
Each bolt will have a special marking which specifies its design size and type.
Note that no shell type anchor bolts are used on STPEGS.
A static Testing Drogram in the field to verify the load capacity of belts is also being developed in conformance to this Bulletin.
The installation of expansien anchors for safety-relate? piping systems will not c;mrence until the QC ard static Testing Pr: grams are established. o :_ %,
d O C Ks i hJ
Re fe rences_:
1.
Proposed Additien to:
Code Recairerents for Nuclear Safety-Related Ccncrete Structures (ACI 309-76), Reported by ACI Committee 349; as publisr.ed in ACI Journal, August 1973.
2.
Standard for Testino Anchors in Concrete, Expansion Anchor Manufacturers Institute, Inc., New York.
3.
Drilled-In Excansion Bolts Under Static And Alternetino Load, a report prepared for Hanford Engineering Ceveleprent Lacoratory, Richlard, Washington by Eechtel Pcwar Corporation, San Francisco, California, Report No. BR-5853-C-4, January 1975. ; + ~ <, e -,
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