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Code Requirements for Nuclear Safety-Related Concrete Structures (ACI 349)

Session 2 – Structural Systems or Elements

This Webinar is sponsored by ACI. The ideas expressed, however, are those of the speakers and do not necessarily reflect the views of ACI or its

committees. The audience is expected to exercise judgment as to the appropriate application of the information.

Please adjust your audio level at this time.

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• For continuing education credit, attendees must purchase the ACI webinar titled “Nuclear Safety-Related Concrete Structures” for $200 ACI members/$250 nonmembers. Attendees that log in with full name and email address, and attend the entire webinar, will receive certificates for each part of the four-part webinar series. Totaling 5 Professional Development Hours (PDH) of continuing education credit. Visit www.ACIeLearning.org and login to access the ACI eLearning site.

• For site license purchasers, if you view the webinar within a group, your name, email address and signature must appear on your organization’s group attendance sign-in sheet.

• Corporate group discounts are available for those attending the live webinar by contacting Claire Hiltz at Claire.Hiltz@concrete.org.

• Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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American Concrete Institute is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this eLearning course will be reported to AIA/CES for AIA members.

The eLearning course based on this webinar is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

• The American Institute of Architects has approved this course for 1 AIA/CES LU/HSW Learning Unit.

The American Institute of Architects has approved this course for 1 AIA/CES LU/HSW learning unit.

ACI is an AIA/CES registered provider.

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• Recognize the scope of structures covered by ACI 349.

• Identify the difference between ACI 318-08 and ACI 349-13.

• Identify the material requirements for design in accordance with ACI 349.

• Understand the basic assumptions and design philosophy behind reinforced concrete design according to ACI 349.

• Identify design and detailing requirements that are specific to nuclear construction.

• Become acquainted with ACI Committee 349 documents:

1) 349.1R-07, Reinforced Concrete Design for Thermal Effects on Nuclear Power Plant Structures;

2) 349.2R-07, Guide to the Concrete Capacity Design (CCD) Method—Embedment Design Examples; and

3) 349.3R-02, Evaluation of Existing Nuclear Safety-Related Concrete Structures.

Learning Objectives:

Code Requirements for Nuclear Safety-Related Concrete Structures (ACI 349)Session 2 – Structural Systems or Elements

Code Requirements for Nuclear Safety-Related Concrete Structures (ACI 349)Session 2 – Structural Systems or Elements

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Dr. Javeed MunshiJaveed Munshi is Senior Principal Engineer and Fellow at Bechtel PowerCorp. in Frederick MD. He has over 25 years of experience in the design,evaluation, and construction of concrete structures, including heavy industrial(fossil, nuclear and renewable) power structures, bridges, buildings,underground structures (tunnels), and environmental concrete structures. Hehas served on expert panels and peer reviewed many projects. He hascontributed to eight books/design aids for concrete, and published over 70papers. He has conducted concrete design seminars and training for theAmerican Concrete Institute (ACI), the Portland Cement Association (PCA),and the Concrete Reinforcing Steel Institute (CRSI). He is Fellow of theAmerican Concrete Institute (ACI), Fellow of the American Society of CivilEngineers (ASCE), and Fellow of the Structural Engineering Institute (SEI).He is also a licensed professional engineer (PE) in New York, Wisconsin andMaryland and a licensed Structural Engineer (SE) in Illinois. He is a memberof ACI 349 and ASME Section III, Div 2. Committees for concrete nuclearstructures.

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Herman L. GravesHerman L. Graves, III, P.E., FACI is a consulting engineer. He worked as aSenior Structural Engineer at the U.S. Nuclear Regulatory Commission(NRC) from 1980 to 2013, where he formulated and managed researchprograms related to nuclear civil/structural engineering.

Mr. Graves has been an ACI member for more than 30 years. He is theimmediate past chairman of ACI Committee 349, “Concrete NuclearStructures,” a member of ACI Committee 355, “Anchorage to Concrete,” anda member of the Committee on Awards for Papers. He was named a Fellowof ACI in 2008, and has contributed to various ACI publications as an authorand technical reviewer. He is a licensed Professional Engineer inWashington, DC and Maryland.

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CODE REQUIREMENTS FOR NUCLEAR SAFTEY RELATED CONCRETE

STRUCTURES

Session 2

By Javeed Munshi, PhD., P.E., F. ACI, F. ASCE

Partha Ghosal, M.S., P.E.

Herman L. Graves, III, M.S.,P.E., F. ACI

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CHAPTER 11SHEAR & TORSION

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SHEAR & TORSIONSHEAR & TORSION

Slabs Without Shear Reinforcement

Shear Reinforcement – U Stirrups

Deep Beams

Strut and Ties

Brackets

Footings

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SHEAR

• Factored Shear Forces Vu

Vu / ≤ Vn

where = 0.85

Reference: Sec. 11.1

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SHEAR

• Nominal Shear Strength

Vn = Vc + Vs

• Shear strength provided by concrete

Vc = 2fc´ bw d

note: ּג = 1.0 normal weight concrete

note: strut and tie design considered in Appendix A.

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349-13 same as 318-08 except sections 11.11.2.3 and 11.11.2.3.1 thru 11.11.2.3.4 added to provide for slabs and footings subject loads producing punching shear forces.

Provisions for Slabs and Footings

Reference 11.11.2.3

Slabs or footings with shear force Vu occurs with membranestresses fm1 or fm2,

Vc = Vc1 + Vc2 (11-34a)

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7SHEAR

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8SHEAR

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Fig. —Concrete shear strength in presence of membrane tensile stresses.

Punching Shear

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Vc1 and Vc2 are:For fm1 tensile and ≤ 0.9ρ1′fy

except factor (2 + 4/βc) shall ≤ 4. For fm1 tensile and > 0.9ρ1′fy

For fm1 compressive and ≥ 125 psi, Vc1 shall be taken as Vc, calculated in accordance with 11.11.2.2 except that in Eq. (11-34), fm1 and b1′ shall be used in place of fpc and bo, respectively.

For fm1 compressive and < 125 psi, Vc1 shall be taken as Vc calculated in accordance with 11.11.2.1 except that b1′ shall be used in place of bo.

Punching Shear

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SHEAR - Summary

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Design of shear reinforcement for Beams

1. Maximum spacing of stirrups s ≤ d/2 (this prohibits cracks between stirrups)

2. Maximum spacing of stirrups s ≤ d/4 if Vu/f - Vc > 4fc´ bw d (this applies only with large stirrups in beams)

3. Minimum value Av ≥ 50 bw s / fy

(this applies only with small stirrups in wide beams)

4. Stirrups are NOT required if bw > 2.5d (Beam thinks it is a slab)

5. When lu / h < 5, such beams are defined as deep beams, and a separate set of rules require the use of both horizontal and vertical bars as shear reinforcement.

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The design for torsion in 318-08 is based on a thin-walled tube, space truss analogy. A beam subjected to torsion is idealized as a thin-walled tube with the core concrete cross section in a solid beam neglected as shown in Fig. R11.5(a). Once a reinforced concrete beam has cracked in torsion, its torsional resistance is provided primarily by closed stirrups and longitudinal bars located near the surface of the member.

Design for torsion

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Fig. 11.5—(a) Thin-walled tube; (b) area enclosed byshear flow path.

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Closed Ties or Stirrups

1.3 ld

Torsion

Full Depth

9 kip Max

Closed Tie or Stirrup

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1. One piece with overlapping 90 or 135 degree end hooks around a longitudinal bar.

2. Two piece with a Class B splice.

3. Neither of the above two are suited for high torsion.

4. Two piece closed stirrup used for torsion.

5. Section 12.13.5 gives lap splice requirements for double U-stirrups or ties (1.3 ld)

6. If 1.3 ld cannot fit, use full splice and limit force in each leg to within 9 kips (18 in. min. depth required)

Closed Ties or Stirrups

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CHAPTER 12DEVELOPMENT AND SPLICE MOSTLY SIMILAR TO ACI 318

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In order to develop bars, bars pulled from concrete encasement or push against concrete:

Failure Modes from Splitting Cracks:

Corner Splitting Bottom Splitting Face Splitting

Need more edge distance Need more bottom cover Bars too close together

P P

Bar Development

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Factors ,, and = 1 with the following exceptions:

= location factor = 1.3 if more than 12 in of concrete is cast below bar. = bar epoxy coating factor = 1.2 to 1.5 if bars are coated. = bar size factor = 0.8 for #6 and smaller bars. = concrete density factor = 1.3 if lightweight concrete is used.

Bar Development

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Grade 60 Bars in fc’ = 4000 psi concrete [Bottom-cast Bars] ,, and λ = 1

Bar size Shortest possible “Usual” case “Worst” case

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10

9

8

7

6

5

4 Multiply these values by 1.3 for Top-cast Bars

3

12 20 30 40 50 60 70 80 90

Basic Development Length d (in)

Bar Development

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Hooked Bars Compression Bars

dh = (1200db/fc’)(fy/60000) dc = 0.02dbfy/fc’ 0.0003dbfy > 8 in

For Grade 60 Bars in Concrete of fc’ = 4000 psi

ldh dh dc Asfy

26.8 #11 26.824.1 #10 24.121.4 # 9 21.419.0 # 8 19.0

Asfy 16.6 # 7 16.6 dc

14.2 # 6 14.2 11.9 # 5 11.99.5 # 4 9.58.0 # 3 8.0

Multiply by 0.7 if side concrete Multiply by 0.75 if bars are cover is more than 2.5 in. enclosed by transverse spiral

No increase is necessary for dh or dc if bars are top-cast bars.

Bar Development

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1. At least one-third of bottom bars required for positive moment must be extended at least 6 in into supports of simply supported beams.

2. At least one-fourth of bottom bars required for positive moment must be extended at least 6 in into supports of continuous beams.

3. At least one-third of top bars required for negative moment must extend beyond the Point of Inflection associated with the negative moment.

4. Continuing bars for flexure must extend beyond the point at which they are required for a distance at least 12db or the depth

of the member d.

Bar Development

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1. Lap splices are restricted to bars #11 and smaller.

2. Class B Tension Splice length shall be 1.3d .

3. Class A Tension Splice length = 1.0 d may be used if:a) Fewer than half of bars are spliced at same

location, or b) Bar stress being developed is less than fy/2.

4. Splices shall be staggered at least 24 in

5. Compression Splice Length shall be (0.0005fy)db or (0.0009fy – 24)db but not less than 12 in.

6. Compression splices within spiral columns may be 75% as long as 5 above, but not less than 12 in.

Bar Splices

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Exception for Gr 75 and Gr 80

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Mechanical Splice

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Mechanical Splice

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Splice

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Mechanical Anchorage

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Mechanical or Welded Splice

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Mechanical or Welded Splice

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1. No. 14 and 18 bars cannot be bundled in beams.

2. If individual bars are cut off within a span, they should be staggered by 40 db.

3. For spacing and cover, a unit of bundled bar must be treated as a single bar with an area equal to the total area of all the bars.

4. A maximum of 4 bars may be bundled.

5. Bundled bars must be enclosed within stirrups or ties.

6. Development length based on individual bars increased by 20% for 3 bar bundle and 33% for 4 bar bundle.

Bundled Bars

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Noncontact lap splices shall be transversely spaced within the smaller of 1/5th required splice length and 6 in.

Noncontact Lap

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CHAPTER 13TWO WAY SLABS

SAME AS IN ACI 318

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One-way slab

Beams provide support for slab to act only

in one direction between beams.

Two-way slab

Beams along all four edges permit slab to

act in both directions between parallel

beams.

Flat plate

Absence of beams forces slab to act in both

directions between lines of columns.

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A

B

TWO-WAY DEFLECTION

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Frame 1 Frame 2 Frame 3 Frame 4

Col. Strip

Col. Strip

Col. Strip

Slab Strip

Col. Strip Col. Strip

Slab Strip

Frame A

Frame B

Frame C

Frame D

Direct Design and Equivalent Frame Method

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1

1

2

2

c1

c1

hs

Col.

Col.

Col.

Torsion member

c2

Torsion constant C = (1-0.63hs/c1)hs3c1/3

Torsion stiffness Kt = 9EcC /[2(1-c2/ 2)3]

Slab-beam value of I is Islab = (1-c2/2 )2c2c13 /12

Equivalent column stiffness = Ke and 1/Ke = 1/Kt + 1/(4Ec Islab) (9.3) The joint shown has 2 torsional members and 2 column members.

Equivalent Frame Procedure

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Equivalent Frame Procedure

ACI318-05, Section 13.7.6 – Arrangement of live load

* Each frame extends from slab centerline to slab centerline or edge of slab.

* Shears and moments along each frame must be determined. Spreadsheet program can be adapted for the analysis of each span of each frame.

* When wL < 0.75wD, assume total load wu acts simultaneously on all spans.

* When wL > 0.75wD, for positive moments assume that 0.75wu acts everywhere.

* When wL > 0.75wD, for negative moments assume that wu acts in span, but 0.75 wu acts on adjacent spans.

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CHAPTER 14WALL DESIGN

SIMILAR TO ACI 318

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Wall Design

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Walls

• Design for Shear

3 cases to consider:Vu ≤ Vc /2

Vc /2 < Vu ≤ Vc

Vu > Vc

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CHAPTER 15 FOOTINGS

349-13 SAME AS 318-08

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Foundation SystemsFoundation Systems

• Basic types of foundation system• Wall footing• Isolated spread footing• Combined footing• Strap footing• Pile footing• Raft or Mat footing

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Footing Design ProcedureFooting Design Procedure

• Calculate footing size based on allowable soil bearing capacity using un-factored combination of loads

• Consider footing thickness and calculate average effective "d"Ave. d ≈ h - 4.0“

• φ factor to check shear strengthφ = 0.85 [Sec. 9.3.2.3]

Reference: Sec. 15.2, 9.3

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CHAPTER 16PRECAST

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GeneralGeneral

16.1—Scope16.1.1 Provisions of Chapter 16 shall apply for design ofprecast concrete members defined as concrete elements cast elsewhere than their final position in the structure.

All provisions of this Code not specifically excluded, and not in conflict with provisions of Chapter 16, shall apply to precast concrete.

Note: ACI 349-13 fully adopted 318-08 guidance.

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CHAPTER 17COMPOSITE CONCRETE

FLEXURE MEMBERS

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GeneralGeneral

17.1—Scope17.1.1 Provisions of Chapter 17 shall apply for design ofcomposite concrete flexural members defined as precast and/or cast-in-place concrete elements constructed in separateplacements but so interconnected that all elements respondto loads as a unit.

All provisions of this code shall apply to compositeconcrete flexural members, except as specifically modifiedin Chapter 17.

50

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GeneralGeneral

• Horizontal shear strength (ties)

• Vnh shall be taken equal to (260 + 0.6ρvfy)λbvd, ≤ 500bvd, where λ is 1.0 for normal weight concrete and ρv is Av/(bvs)

Reference: Section 17.5.3.3

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CHAPTER 18PRESTRESSED CONCRETE

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Chapter 18 ,continued

• The commentary on ACI 318 is applicable to this chapter except references to lightweight concrete and other prestressed reinforcing systems n.a. to nuclear safety related structures are omitted.

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Section 18.1.4 - Service load conditions are defined to be the load combinations of Section 9.2.1 of 349-13 with load factors taken as unity:

(9-1) U = (D+F+RO) + TO

(9-2) U = (D+F+ TO + RO) + (L+H) + CCR + (Lr or S or R)

(9-4) U = (D+F+RO) + (L+H+ Eo)

(9-5) U = (D+F+RO) + (L+H+ W)

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Chapter 18, cont.

• Section 18.13- Post-tensioned tendon anchorage zones

• Same as 318-08 except in Section 18.13.4.2

• ּג = 1.0

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CHAPTER 19SHELLS

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Chapter 19 of ACI 318-08 is intended to provide design provisions for the wide range of shell forms expected to be used for commercial structures. These include thin shells, folded plates, and ribbed shells to name a few. In nuclear safety related concrete structures, the shell forms usually encountered are limited to basic cylinders with dome shapes, having thicknesses not less than 12 in.

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Chapter 19, continued

19.1 – Scope and Definitions

19.1.1 Chapter 19 shall apply for design of shell concreteStructures having thicknesses equal to or greater than 12 inches (2.54cm)

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Chapter 19, continued

19.2.10—Model tests

19.2.10.1 Model tests may be used in support of the

design if they are planned and executed by individuals or laboratories with experience in physical testing.

19.3-Design strength of materials

Specified compressive strength of concrete fc´ at 28

days ≥ 3000psi

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Thank you

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