ML20128K083

Forwards Summary of Currently Unanswered Cable Tray Support Design Review Questions.Questions & Effect on Design May Be Answered More Efficiently as Part of Dynamic Analyses Conducted on Selected Sys

ML20128K083
Person / Time
Site:	Comanche Peak
Issue date:	02/12/1985
From:	Williams N CYGNA ENERGY SERVICES
To:	George J TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
References
84056.041, NUDOCS 8507100474
Download: ML20128K083 (16)

Text

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101 Cahfornia Street. Suite 1000. San Francisco. CA 941115894 415 397-5600 February 12, 1985 84056.041 Mr. J. B. George Project General Manger Texas Utilities Generating Company Comanche Peak Steam Electric Station Highway FM 201 Glen Rose Texas 76043

Subject:

Cable Tray Support Review Questions Comanche Peak Steam Electric Station Independent Assessment Program - Phase 4

. Job No. 84056

Dear Mr. George:

We have reviewed our correspondence and telecon files to ascertain the status of the cable tray support review questions asked to date. Attachment A contains a sunnary of currently unanswered cable tray support design review questions.

Additional questions may be asked as we complete our documentation of the TUGC0/Gibbs & Hill responses to previous questions and evaluate the responses to the attached questions. Perhaps some of these questions and their relative effect on design adequacy nay be answered more efficiently as part of the dynamic analyses being conductd on selected systems. Please advise us of any questions being addressed as part of that effort.

If there are any questions while preparing responses, please call.

Very truly yours, N. H. Williams

. Project Manager NHW/rmk cc: Mr. S. Burwell (USNRC)

Mr. S. Treby (USNRC)

Mr. D. Wade (TUGCO)

Ms. J. van Amerongen (EBASC0/TUGCO)

Mrs. J. Ellis (CASE)

Mr. R. Ballard (G&H)

Mr. R. Kissinger (TUGCO)

P BQ P

San . .. ,6.s o Boston Chicago Richland

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Mr. J. B. George February 12. 1985 84056.041 Page 1 of 13 ATTACHENT A CABLE TRAY SUPPORT REVIEW QUESTIONS

1. EMBEDDED PLATES

References:

(1) Gibbs & Hill Specification 2323-SS-30, Revision 1 "Struc-tural Embedments," Appendix 4 (2) TRW Nelson Division, Design Data 10. "Embedment Properties of Headed Studs," 1977 (3) Gibbs & Hill calculations SCS-113C, Set 1, sheets 18-19,

. 42-46

- (4) Gibbs & Hill drawing 2323-5-0919, Revision 3 Several cable tray supports within Cygna's review scope are attached to embedded strip plates. These supports are Types SP-7 with brace, SP-7 and Detail F (drawing 2323-El-0601-01-5), which is similar to a multiple SP-7 support. Each of these supports consists of channel sections canti-levered from the embedded plate. These supports resist vertical, trans-verse, and, in the case of Detail SP-7 with brace, longitudinal tray loa ds. The connection between the cantilevered channels and the embedded plate is an all-round fillet weld. Such a connection provides full moment transfer.

The design of the embedded plates for the support types listed above was performed in 1979. In 1981, Gibbs & Hill specification 2323-55-30 revi-sion 0, " Structural Embedments," was issued. Appendix 4 of this specifi-cation lists the criteria and allowables for attachments to embedded strip plates. , Revision 1 of this specification (Reference [1]) did not I alter the criteria or allowables for embedded plates. Cygna has noted l that the criteria listed in the referenced appendix are more stringent l than those used in the original design of the embedded plates for the support types listed above.

Cygna requests a confirmation of the assumptions used in the generic

! embedded plate analysis. Gibbs & Hill has stated that a factor of safety of two was used in the analysis. Rigid plate assumptions as well as prying action effects were also considered. Cygna has calculated the allowable stud tensile loads based on values and reduction procedures reported in Reference (2) above and on a factor of safety of two. The t

values calculated by Cygna were identical to the allowable loads for

! point loadings applied along the plate centerline at stud points. This indicates to Cygna that prying action has not been considered in the

! development of embedded plate allowables.

I

Mr. J. B. George February 12, 1985 84056.041 Page 2 of 13 L ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS With regard to the design of the embedded plate connections for the sup-port types listed above, Cygna has noted several inconsistencies between the designs and the criteria reported in Specification 2323-SS-30, Revi-sions 0 and 1. The embedded plate connections that are used for the listed support details are moment resisting connections. Section 3.4 of Reference (1) above states that pin connections are to be used for load transfer to embedded plates. This section also requires that when a mo-ment is to be transferred, the embedded plate connection must be stiff-ened. Further restrictions on moment transfer are listed in Section 4 Gibbs & Hill has stated that all moment connections must be evaluated per

- these sections. Cygna has not seen any evidence that such evaluations were performed for the cable tray supports listed above.

Sheets A4-1 through A4-9 of Appendix 4, reference (1), list the allowable values for various locations of applied point loads. Section 3.1 lists various reductions for locations other than those shown in the Appendix sheets 1-9. These reductions include interpolation of allowable values for attachment locations between the midspan and stud pairs along the longitudinal plate centerline. Interpolation of plate allowables is also required for attachment points between the longitudinal centerline and the stud lines at the plate edge. In addition, a 40 percent reduction is required for end-span loadings. It appears that none of the above reductions was considered in the design of the embedded plates for the listed details.

Section 3.3 notes that the full allowables shown on sheets A4.2 and A4.4 are applicable only when the attachment is within i 3/4 inches of the longitudinal plate centerline. The centerline tolerances allowed in Ref-erences 3 and 4 for beam connections of Details SP-7 and SP-7 with brace, are 1-1/2 inches and 2-1/2 inches for eight and ten inch plates, respectively. A 1-1/2 inch tolerance is allowed for the brace connec-tions of Detail SP-7 with brace. These tolerances exceed those specified in Section 3.3, even though the full allowables were used.

Please provide Cygna with the following:

1. Documentation which evaluates the effect of prying action on embed-ded plates and studs;

Mr. J. B. George Februa ry 12, 1985

- 84056.041 Page 3 of 13 ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS

2. Documentation and justification for the acceptability of the monent connections for Details SP-7, SP-7 with brace and Detail F; and

3. Documentation which verifies that the details listed in question 2 above meet the criteria set forth in Appendix 4 of Reference 1.

2. AFFECT OF TWO-!NCH THICK ARCHITECTURAL TOPPING ON HILTI BOLT EftBEDt1ENT LENGTH

References:

O (1) TUGC0 SDAR-CP-80-05 dated 8/8/80 (2) Brown & Root Instruction CEI-20. Revision 9 (3) CMC 6114, Revision 4, dated 10/12/83, Support No. 2998 (4) CMC 85720. Revision 0, dated 2/2/83, Support No.13080 Two cable tray supports within Cygna's review scope, support numbers 2998 and 13080, use floor mounted base plates. These supports are located in areas where 2" thick architectural topping is present. A walkdown was performed to verify that sufficient Hilti anchor bolt embedment was pro-vided. Based on the length code stamped on the exposed ends of the in-stalled Hilti Super Kwik bolts and the measured projection, (i.e., the distance from the floor slab to the top of the bolts), the bolts in-stalled are not of sufficient length to provide the minimun embedment specified in References (3) and (4) for these supports.

Cygna calculated minimum embedment length before torquing for these two supports as follows:

t

Mr. J. B. George February 12, 1985 84056.041 Page 4 of 13 ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS Embedment = (bolt length) - (topping) - (bolt projection) + (nut thickness)

Support Bolt Bolt Projection Minimum Embedment No. Code Length Above Slab Calculated Required 2998 U 13" 4-3/8" 7-7/8" 8-1/2" 13080 X 16" 4-1/4" 11" 13-1/8" Cygna was provided with a copy of Reference (1) above, when this concern was first discussed with TUGCO. The corrective action indicated in Ref-erence (1) requires a case-by-case evaluation of all Hilti bolts in- '

stalled in areas with two-inch topping. Cygna interprets this as apply-ing only to bolts installed before the date of Reference (1). Since both floor mounted supports within Cygna's scope were installed after that date, they would not have been included in the evaluation.

Reference (1) also indicates that Reference (2) above was revised to reflect the effect of topping on embedment length. Section 3.1.7.1.2 of reference (2) states:

" Expansion bolts which have less than the specified designed embedment length into structural concrete but greater than the values indicated above in 3.1.7.1.1 shall be evaluated by the responsible design engineer. If found to be acceptable "as-is," appropriate design change documents shall be issued. If found to be unacceptable, the expansion bolt shall be reworked in accordance with 3.1.7.1.1 a or b."

Assuming that this criteria was followed for the installation of support numbers 2998 and 13080, the Quality Control inspection travelers should show that the "specified designed embedment length" was not met, and that an evaluation was performed by the " responsible design engineer."

Please provide copies of the existing design change documentation for these supports indicating the acceptability of the reduced embeddent length. If no documentation exists, please assess the impact of this issue on other floor mounted supports in the areas where two-inch topping is used.

Mr. J. B. George Februa ry 12, 1985 84056.041 Pa ge 5 of 13 ATTAC K NT A CABLE TRAY SUPPORT REVIEW QUESTIONS

3. CONTROLLING LOAD CASE FOR ONE-BOLT BASE ANGLE ANALYSIS

References:

(1) Gibbs & Hill Drawings: 2323-S-0903, Detail 1 2323-S-0908 2323-S-0909 (2) Conference Report dated 11/14/84, 2:15 p.m.; Bhujang, Chang, Berry, Horstman and Russ

, (3) THE Calculation by J.C.C. dated 11/15/84, " Investigation

, of Single Clip Angle" (4) Gibbs & Hill Calculation Binder SCS-215C, Set 4 During the discussion regarding the analysis of Detail 1, one-bolt base angle connections, as noted in Reference (2) above, Gibbs & Hill was to determine the controlling load case for this connection, i.e., the max-imum loads. The calculations provided, Reference (3) above, use the loads from a B-2 type support, but do not provide any comparison to show that this is the controlling case. Based on Cygna's review of existing calculations, it appears that other support types may develop larger loads for this connection detail. An example of a support type with larger loads is case E-4, per Reference (4) above, sheets 16-20.

Please provide documentation indicating the controlling load case for the one-bolt base angle and an analysis considering these loads.

4. WORKING POINT DEVIATION CALCULATIONS Cygna has reviewed the Gibbs & Hill working point analysis performed in March and April 1984. This review identified problems with boundary conditions (unjustified restraint of frames in the longitudinal direction) and the effects of closely spaced modes. Gibbs & Hill revised the working point analysis to correct these discrepancies and resubmitted them to Cygna for review. Based on discussions with site personnel, Cygna understands that any work associated with the closure of the working point study has been suspended until the NRC mandated as-built program is completed. Cygna, however, has concerns about the analysis

Mr. J. B. George February 12, 1985 84056.041 Page 6 of 13 ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS and its application which would not be addressed by an as-built program alone.

The working point study establishes cut-off elevations below which the supports may be considered acceptable for given working point deviations. This evaluation is based on assuned accelerations, 8'-6" tray spans, enveloping aspect ratios, and maximum permissible working point deviations. Above these elevations, Gibbs & Hill evaluated the supports on a case-by-case basis using design documents only. No consideration was given to trays where the unit weight exceeded 3S lb/sf

- due to added fire protection or to the as-built support configuration as

- reflected by applicable CMC's and DCA's. Cygna has identified spans up to 12 feet (reference Cygna letter 84056.019 dated 8/10/84) in length which indicates that there would be a problem in justifying the qualification of trays below a given elevation using an assumed 8'-6" spa n. Further, for supports located above the cut-off elevation where the map drawing shows spans greater than 8 feet, an additional 6" installation tolerance must also be considered.

The effect of possible variations in aspect ratio, fire protection weight and actual working point deviations must be considered in the same manner as the above concerns regarding span violations. Further, Quality Control's use of a working point deviation criteria as the sole means of ensuring compatibility with the Gibbs & Hill analysis will not unto itself ensure design adequacy.

Please indicate the plan of action TUGC0 will use to resolve this issue.

5. DETAILS F-H, DRAWING 2323-El-0601-01-S AND SP-7, EFFECTS OF SMALLER WELD SIZE AND UNDERRUN

Reference:

(1) Conference Report dated 11/17/84, 8:00 a.m.; Cha ng ,

Huang, Horstman, Russ and Williams From the referenced conference report:

i 4

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Mr. J. 8. George Februa ry 12, 1985

. 84056.041 Page 7 of 13 ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS "Cygna has reviewed the Gibbs & Hill calculations which address the change in fillet weld size (3/16" vs.1/4") for Details F-H. Cygna has noted that when the effects of eccentric loads are considered, the welds appear to be overstressed. The Gibbs & Hill calculations did not consider these effects. Gibbs & Hill inquired if the member was also overstressed. Cygna responded that for a 4'-9" cantilever length details SP-7 and F-H there is a resulting 4% over-stress. Cygna provided the following list of details which appear to exhibit overstress conditions in the weld and/or

, member.

For 3/16" fillet weld without underrun:

(a ) Details F-H without brace with 30" tray and maximum moment arm.

(b) SP-7 attached to embedded plate with 24" and 30" trays.

(c) SP-7 with brace attached to embedded plate with 24" and 30" trays. (Gibbs & Hill noted that allowable tray spans for embedded plates is 7'-6".)

(d) Details F-H attached to embedded plate with 24" and 30 " trays.

For 3/16" fillet weld with 1/32" underrun for all tray sizes:

(a ) Details F-H.

, (b) Details F-H attached to embedded plate.

(c) SP-7 attached to embedded plate.

(d) SP-7 with brace attached to embedded plate.

i Potential member overstress examples include:

(a ) Details F-H with 30" tray.

(b) Details F-H attached to embedded plate.

, (c) SP-7 attached to embedded plate.

l (d) SP-7 with brace attached to embedded plate."

i

Mr. J. B. George February 12, 1985

. 84056.041 Page 8 of 13 ATTACMMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS U

Please indicate the plan of action TUGC0 will use to address the potential weld and member overstresses indicated above.

6. WELD DETAIL FOR CONNECTION OF CHANNELS TO CLIP ANGLES

References:

(1) Gibbs & Hill Drawings: 2323-S-0901

. 2323-S-0902

. 2323-5-0903 (2) Brown & Root Drawing FSE-00159 (3) Conference Report, dated 11/17/84, 8:00 a.m. ; Chang, Huang, Horstman, Russ and Williams (4) Conference Report, dated 12/19/84, 9:30 a.m. ; Keiss, Warner, Mercer, van Amerongen, Horstman and Russ (5) Gibbs & Hill Calculation Binder SCS-215C, Set 2 (6) Gibbs & Hill Calculation Binder SCS-122C, Set 3 (7) Gibbs & Hill Calculation Binder SCS-146C, Set 1 (8) CMC 82988, Revision 0, dated 11/15/82, Revision 1, dated 3/7/83 and Revision 2, dated 7/11/84 (9) DCA 20228, Revision 0, dated 4/10/84 and Revision 1, dated 4/30/84 (10) RFIC EH-1842, dated 11/5/82 A review of the cable tray support design drawings, Reference (1), showed that no minimum length is specified for the weld attaching a support channel to the angle section used as a base plate. Suppcrt types for which the weld length is not specified include Details 1, 4 B, C, D.

Case SP-7 plan, etc. The hanger assembly drawings, Reference (2), typi-cally indicate the distance between the face of concrete and the end of the channel to be 1-1/4", but specify no tolerance for this dimension.

The 1-1/4" dimension results in a 3-3/4" lap between the channel and an L5 x 5 x 3/4.

Referring to the discussion in Reference (4), TUGC0 indicated that the 1-1/4" dimension was used as a maximum distance for installations where the channel was attached on the outside of the angle (Type II). It was also

Mr. J. B. George February 12, 1985 84056.041 Page 9 of 13 ATTACHE NT A CA8LE TRAY SUPPORT REVIEW QUESTIONS used as a minimum distance for installations where the channel was at-tached on the inside of the angle (Type I). (Due to the internal radius on the angle, a member can not be attached any closer than "k" from the heel of the angle, e.g., k = 1-1/4" for L6 x 6 x 3/4 and L5 x 5 x 3/4.)

If the channel laps into the fillet at the corner, it does not lie flat against the leg of the angle and a gap will result. Mr. Warner assured Cygna that the weld fit-up inspection prevents this from occurring and that the weld inspection assures that the proper weld, including end returns, is installed.

~

If 1-1/4" is used as the minimum distance for Type I connections, the resulting weld length could be less than 3-3/4". In Gibbs & Hill's eva-luation of weld size underrun, a weld length of 3-3/4" was used per Ref-erence (6) for the standard connection details and per Reference (7) for SP-7 and SP-7 with brace. The use of a shorter weld length could result in an overstress in the welds used in this detail. Per Reference (10),

clarification on this natter was requested by site personnel and as a result CMC 82988 [ Reference (8)] was issued to give specified tolerances on the connecting weld length. CMC 82988 was issued in November 1982, by which time the nejority of the Unit 1 cable tray supports had already been installed.

Further review by Cygna noted that due to the radius at the toe of an angle section, a gap will exist between the web of a channel and the an-gle section at the toe. (See Figure 1.) In order to achieve a 3-3/4" weld length and the necessary return, the fillet weld must bridge this ga p. Cygna believes that without the use of a special welding procedure, a fillet weld will not achieve its full effective throat at this location, and thus the weld section properties will be less than considered in the design calculations.

Plese provide the following:

• The documentation fron engineering used by Brown & Root to establish the 1-1/4" distance between the face of concrete and the end of channel shown on FSE-159 drawing sheets. This was previously requested in the Reference (4) conference report,

Mr. J. B. George February 12, 1985 84056.041 Page 10 of 13 ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS e The installation tolerance for the connecting weld length that was used prior to the issuance of CMC 82988 and provide assurance that a minimum weld length of 3-3/4" was always provided.

• The welding procedure which applies to performing a fillet weld over the gap between the channel and the toe of the angle section or documentation to show the acceptability of the connection.

7. WELD DETAILS AFFECTED BY GENERIC CHANGE DOCUMENTATION

References:

O (1) CMC 58338, Revision 0 (2) Gibbs & Hill Calculation Binder SCS-122C, Set 3 (3) Conference Report dated 11/17/84, 8:00 a.m.; Chang, Huang, Russ, Horstman and Williams As discussed in the referenced conference report, Cygna indicated that in order to evaluate the effect of the use of 1/4" fillet welds for cable tray support fabrication, generic CMC's and DCA's which address changes in welding requirements must be reviewed. Cygna provided a list of CMC's and DCA's affected by this concern, but noted that the list should be checked for completeness.

During additional review, Cygna located CMC 58338, which may be effected by this concern. This CMC allows an alternate weld pattern to be used for the connection between the beam and hanger members. An evaluation of the weld pattern using a horizontal run along with top and bottom flanges of the (C x 7.25 results in an approximate 20% reduction in tne torsional modulus compared to the value used in the weld evaluation per Reference (2). The CVC for this CMC indicates that no calculations were required.

Please provide the following:

• Justification for the adequacy of this alternate weld pattern, taking into account the potential of weld size underrun and the use of 1/4" weld size for this connection detail.

Mr. J. B. George February 12, 1985 84056.041 Page 11 of 13 ATTAC MENT A CABLE TRAY SUPPORT REVIEW QUESTIONS

• The status of Gibbs & Hill's investigation into the effect of the reduced weld size on the design review of the generic CMC's and DCA's for weld details.

8. INSTALLATION TOLERANCES FOR CABLE TRAY SUPPORTS

References:

(1) DCA 20228, Revision 1 (2) DCA 9738. Revision 3 (3) Specification 2323-SS-16B DCA 9738 provides the following revision to specification 2323-SS-16B:

9.6 TOLERANCE

9.6.1 In general, all structural steel work shall be plumb and level within the tolerance 1:500.

9.6.2 Hangers for electrical raceway systems shall be installed within following tolerances. The cumulative effect of rolling (mill),

fabrication and erection tolerances shall not exceed those given below:

• A hanger shall be considered plumb if the angle between the longitudinal axis of the main member (s) of the hanger is at right (90') angles to the supporting surface (ceiling or floor). A tolerance of a 2',

unless otherwise noted, shall be acceptable provided the integrity of the supported raceway system and its attachments to the hanger remains intact.

e Hangers supported on vertical surface (wall, column, side of a beam, etc.) shall be considered level with maximun tolerance of 1/2" in 10 feet.

Mr. J. 8. George February 12, 1985 o 84056.041 Page 12 of 13 ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS

• Use of extreme boundaries of such tolerances may be at times aesthetically unacceptable and the owner or its representative way provide stricter tolerances on case by case basis.

Cygna is concerned by the potential effects of the

• 2* tolerance for the plumbness of the hanger on the axial load carrying capacity of the mem-ber. For a typical 12'-0" high support, 2* slope results in a 5" offset of the lower end of the hanger. This offset could result in additional

, bending stresses in the vertical members when axial loading is consid-o ered.

Please provide the following:

e A copy of the design review calculations for DCA 9738 considering the effect of the 2' tolerance on support design.

e The procedure used by the responsible engineer to determine if a finer tolerance is needed to assure that the " integrity of the supported raceway system and its attachment to the hanger remains intact."

9. DETAIL "5", DRAWING 2323-S-0905, SUPPORT NO. 3136

References:

(1) CMC 8229. Revisions 0 - 13 I (2) Gibbs & Hill Calculation Binder SAB-1341, Set 3 Cygna review of the " Design Review" Calculations for CMC 8229, Reference (2), indicated that there are several potential errors in these calcula-tions. Cygna provided a list of questions and comments, pertaining to these calculations, to Mr. B. K. Bhujang on October 20, 1984. No re-sponse has been received from Gibbs & Hill.

Please provide Cygna with the status of this review.

Mr. J. B. George February 12, 1985 84056.041 Page 13 of 13 ATTACHMENT A CABLE TRAY SUPPORT REVIEW QUESTIONS

10. DETAIL "H". DRAWING 2323-El-0601-01-S, SUPPORT NO. 734

References:

(1) Brown & Root Drawing FSE-00159, Sheet 734 (2) CMC 164, Revision 4 (3) Conference Report, dated 10/27/84, 9:15 a.m. ; Keiss, van Amerongen, Chang, Huang, Russ, and Williams Responding to the discussion in the referenced conference report, Cygna

. noted that this support has deviated from the generic design for detail H .

. without brace by rotating one of the channels 90' from the standard orientation. Heavy duty clamps were installed per Reference (2). No consideration was given to the additional of longitudinal loads to this support. The conclusion from Reference (3) was for TUGC0 to provide Cygna with calculations evaluating this support's as-built condition.

Please provide the calculations generated by TUGC0 in response to the discussion.

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