ML17309A075

La - (External_Sender) FW: Deformation RAIs

ML17309A075
Person / Time
Site:	Seabrook
Issue date:	06/07/2017
From:	- No Known Affiliation
To:	Division of Operating Reactor Licensing
References
17-953-02-LA-BD01
Download: ML17309A075 (9)

Text

1 SeabrookLANPEm Resource From:

Greene, Joshua <Joshua.Greene@nexteraenergy.com>

Sent:

Wednesday, June 07, 2017 11:05 AM To:

Poole, Justin

Subject:

[External_Sender] FW: deformation RAIs Attachments:

DeformationRAIs_draftResponse_001.pptx From: Ryan M. Mones [1]

Sent: Wednesday, June 07, 2017 10:53 AM To: Greene, Joshua

Subject:

deformation RAIs CAUTION - EXTERNAL EMAIL Ryan M. Mones Staff II - Structures SIMPSON GUMPERTZ & HEGER l Engineering of Structures and Building Enclosures 41 Seyon Street, Building 1, Suite 500 Waltham, MA 02453 781.907.9000 main 781.907.9263 direct 781.907.9009 fax www.sgh.com Send Files

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6/7/2017 11:04:48 AM From:

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www.sgh.com Draft Response and Talking Points for Deformation Draft RAIs June 2017

ACI 318-71 Sections Referenced in Draft RAI ACI 318-71 Section 8.6:

- This section is related to redistribution of negative bending moment in a continuous member - it is not directly applicable to the CEB wall. However, this section will be used for other Seabrook structures conforming to this requirement.

ACI 318-71 Section 19.3.1:

- In the CEB analysis, demands are first computed using elastic analysis with uncracked section properties, consistent with 19.3.1.

• Thin shells are typically defined by their membrane (in-plane) behavior when away from supports and geometric complexities. However, the loading on the CEB causes out-of-plane deformation, and localized moment redistribution related to out-of-plane effects are considered.

• The moment redistribution used in the CEB evaluation simulates local nonlinear behavior and cracking. Chapter 19 of ACI 349-01,

-06, and -13 permit use of nonlinearity.

• ACI 318-71 Section 8.5.3.1 allows cracked section stiffnesses to be used. This is not considered in the CEB analysis.

DRAFT RESPONSE TO DEFORMATION DRAFT RAIs 2

ACI 349-01, ACI 349-06, ACI 349-13 DRAFT RESPONSE TO DEFORMATION DRAFT RAIs 3

Displacement Controlled Loading

• ASR demands are displacement controlled. These demands are self-relieving. This means that the demands reduce as the structure deforms. This self-relieving effect is not accounted for in an elastic analysis.

- For the CEB:

• Internal ASR expansion is simulated as an imposed strain of the CEB wall. This strain is restrained by other regions of the wall with less ASR expansion and external boundary conditions.

• the ASR of concrete fill imposes a displacement-controlled out-of-plane movement which is simulated by a pressure in the analysis.

DRAFT RESPONSE TO DEFORMATION DRAFT RAIs 4

Moment Redistribution Validation

• Validation of the moment redistribution method is documented in Appendix L of the CEB evaluation.

• The validation compares the moment redistribution approach used in the evaluation to a more detailed approach using nonlinear spring elements.

• Example problems are specific to the CEB structure.

• The validation shows that the method used in the CEB calculation matches well with the more detailed approach.

DRAFT RESPONSE TO DEFORMATION DRAFT RAIs 5

Ductility Evaluation

• The ductility of the reinforcement at locations of moment redistribution is checked using moment curvature evaluations in Appendix O.

• The highest ductility demand is 3.5, corresponding to a reinforcement strain of 0.7%. This is well below the strain limit of 7.0% for Grade 60 bars at fracture (ASTM Standard A615-78).

DRAFT RESPONSE TO DEFORMATION DRAFT RAIs 6

Draft Deformation RAI 2

• A minimum threshold factor of 1.2 is initially targeted for practicality of threshold monitoring.

• The extent of moment redistribution is based on ACI 318-71 Section 8.6 for continuous members.

• For other cases of moment redistribution, reinforcement strains are compared to a strain limit of 7% per ASTM Standard A615-78.

DRAFT RESPONSE TO DEFORMATION DRAFT RAI 2 7