ICH Anchorage to Concrete Seminar 3-19-2015 Anchorage to Concrete Seminar ... • ACI 355.4-11, qualification of Post-installed Adhesive Anchors in Concrete and Commentary

ICH Anchorage to Concrete Seminar Santiago, Chile

19 – 20 Marzo 2015

March 2015 1

Buenos días!2

www.sgh.com

Anchorage to ConcreteACI 318-11 Appendix DACI 318-14 Chapter 17

Neal S. Anderson, P.E., S.E.

Staff ConsultantSimpson Gumpertz & Heger, Chicago, [email protected]

Member ACI 318 – Structural Concrete Bldg. CodeChair 318B – Anchorage & Reinforcement

Seminar Materials Seminar slides handout

Other good reference material• ACI 318-11, Chapter 2 and Appendix D

• ACI 355.2-07 Qualification of Post-installed Mechanical Anchors in Concrete and Commentary

• ACI 355.4-11, qualification of Post-installed Adhesive Anchors in Concrete and Commentary

• ACI SP-17, ACI Design Handbook, Vol. 2

• SP-283, Understanding Adhesive Anchors: Behavior, Materials, Installation, Design

• Code justification technical references

4

Seminar Handout

5 6


19 – 20 Marzo 2015

March 2015 2

ACI 318-14

318–11 Appendix D

318-14 Chapter 17

D. 17.7

The Master Key

318-14 Resource CenterTransition Key: 318-14 to 318-11

Technical changes made to more than 200 individual provisions

11 12


19 – 20 Marzo 2015

March 2015 3

ACI SP-17 (11) Design Examples

13

ACI SP-283 (10) Anchorage Symposium Papers

14

PCA Notes on ACI 318-11 Building Code (EB712)

15

LIBRE

Free Reinforced Concrete Publications

16

Objectives

Recognize the types of anchors and qualification requirements that can be designed using the provisions of ACI 318-11 - Appendix D

Learn to apply the anchor design provisions of Appendix D of ACI 318-11

Understand the importance of selecting qualified post-installed mechanical and adhesive anchors

Work through Design Examples

17

Outline

Types of anchors covered by ACI Behavior background for anchors Case studies of failures ACI 318-11 Appendix D provisions

• Tension design• Shear design• Combined tension – shear design• Splitting requirement• Design for moment (eccentric shear)

Qualification standards Installer certification

18


19 – 20 Marzo 2015

March 2015 4

19

DEFINITIONS

Embedment

AttachmentAnchor

Load actions

Embedmentdepth

ANCHOR TYPES

Cast-in, post-installed mechanical, post-installed adhesive anchors

20

Malleable-iron and cast-steel, circa. 1909

“Rawl” expansion anchor, circa 1938

21

Types of Anchors

Grouted

Undercut Expansion

Cast-in-Place

Covered by ACI 318-11

Adhesive Grouted

BondedMechanical

Not Covered by ACI 318-11

Screw

22

Cast-in Anchors

hef = effective embedment depth

hef

23

Post – Installed Mechanical Types Undercut Anchors (Multiple Types [6])

Pre-DrilledUndercut

Cone Anchor Sleeve

TensileForce

hef

hef = effective embedment depth 24

Post – Installed Mechanical Types Displacement – Controlled

Expansion Anchors

(1) Drop-In Fastener (2) Self-Drilling (3) Stud Fastener Fastener

hefhef hef

hef = effective embedment depth


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25

Post - Installed Mechanical TypesTorque - Controlled

Expansion Anchors

(1) Heavy Duty (2) Wedge Fastener (3) Sleeve Fastener Sleeve Fastener

hefhef hef

hef = effective embedment depth 26

Post – Installed Concrete Screws

Concrete screw anchor• Drill undersize hole• Screw cuts threads in concrete

27

Other Post – Installed Anchors

Powder actuated - installed by shooting anchor into concrete

Expanding lead shield

Bonded Anchors

Adhesive anchors Grouted anchors Of the two bonded anchor types, ACI 318-11

currently provides design rules for only Adhesive Anchors

So, what is the difference?

28

Grouted Anchors Hole diameter > 1.5 x bar diameter

• Cementitious or polymer binders with filler• Generally vertical installations (although

some firms like AMBEX have developed horizontal)

• Typically headed anchor rods or reinforcing bars used

29

Zamora, N. A., Cook, R. A., Konz, R., and Consolazio, G. R., Behavior and Design of Single, Headed and Unheaded, Grouted Anchors, ACI Structural Journal, American Concrete Institute, V. 100, No. 2, March-April 2003, pp. 222-230.

Cook, R. A., Burtz, J. L., Design Guidelines and Specifications for Engineered Grouts used in Anchorages and Pile Splice ApplicationsReport No. BC 354 RPWO #48 Florida Department of Transportation , Tallahassee, FL, August 2003, 119 pp.

Adhesive Anchors Hole diameter < 1.5 x bar diameter

• Frequently used • Covered by ACI 318-11• Typically polymer binders but cementitious

fillers mixed with polymer available

30


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March 2015 6

Adhesive Anchor Materials

31

Adhesive Anchor Materials Epoxy Acrylates

• Resins – Part A; Curing agent – Part B• Almost no shrinkage during curing

Polyesters• Short shelf life; Degrade with exposure to

sunlight; can polymerize without catalysis Vinyl esters

• Faster curing than epoxies slower than polyesters Hybrid systems

• Cement improves stiffness at high temperature• Negligible material shrinkage

32

33

Relative Bond Stress ComparisonAdhesive and Grouted

1800

2342

1659

2259

1780

2850

2663

447

793

1631

2227

1450

2314

1627

2480

2013

2564

334

1656

2104

3055

3040

2306

2579

2872

2586

2901

2946

1063

0

1000

2000

3000

4000

A B C D E F G H I J K L M N O P Q R S T 1 2 3 4 5 6 7 8 9

Product

Ave

rag

e U

nif

orm

Bo

nd

Str

es

s, [

ps

i]

Adhesive uncr mean = 1850 psi [12.7 MPa]

Grouted uncr mean = 2590 psi [17.9 MPa]

Adhesive Grouted

BACKGROUNDHistory of code anchorage design

34

35

History – Early Concrete Breakout Model – Circa 1961

Courtois ACI SP - 22

Concrete Breakout Models

36

45o about 35o

45o cone model 35o cone modelConcrete Capacity Design Model

Concretefracturesurface


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March 2015 7

37

Differences Between Models

CCD

45o Failure Angle 35 o Failure Angle

45o Cone

Nc = kc,45 fc’ hef2 Nc = kc,CCD fc’ hef

1.5

38

45o Cone Breakout Prediction

0

1

2

3

4

5

0 50 100 150 200

Effective Embedment , mm

Obs

erve

d /

Pre

dict

ed

Mean = 1.642COV = 0.338

45o cone method

Single anchor behavior

39

CCD Breakout Prediction

0

1

2

3

4

5

0 50 100 150 200

Effective Embedment, mm

Obs

erve

d /

Pre

dict

ed

Mean = 0.994COV = 0.196

CCD method

Single anchor behavior

40

Failure Angle

0

10

20

30

40

50

0 100 200 300 400 500Embedment length ( mm )

Fai

lure

ang

le (

degr

ees)

n = 11n = 9 n = 6

hef

hef

Failure angle

45o cone

41

History of ACI Anchorage Design ACI 318 Appendix D

Prior to 2002• Model codes (UBC), ACI 349 (Nuclear Structures) • Industry guidelines – PCI Design Handbook• Considered only cast-in-place anchors in uncracked

concrete• Only steel failure and concrete breakout considered

breakout based on 45 – degree cone model

2002 : ACI 318-02 Appendix D published• Cast – in and post – installed mechanical anchors• CCD Method (35 - degree pyramid model)• Cracked concrete

History of ACI 318 Appendix D

2011: ACI 318-11 Appendix D • Includes bonded anchors but only adhesive

anchors (polymeric adhesives)

• Places more emphasis on time-dependent loading

• Defines installation orientation

• Introduces Manufacturer’s Printed Installation Instructions (MPII)

• Introduces a new design model to code based on work of Eligehausen, Cook, and Appl

42


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43

35o failure angle rather than 45o

Default design case – cracked rather than uncracked concrete

Non-uniform stress distribution around an anchor close to an edge

Uneven distribution of load on anchors in a group (eccentricity)

Summary Concrete Capacity Design (CCD)

44

CCD Method Addresses Cracking

Concrete does crack due to• Applied loads• Restrained shrinkage and thermal movement

ACI 318 Appendix D and Qualification Standards (ACI 355.2 and ACI 355.4)• Test to evaluate how well mechanical and

adhesive anchors perform in cracks • Crack width as wide as the thickness of a

fingernail [0.30 mm]

45

Effects of Cracking

F

Uncracked concrete

Cracked concrete

Plane of crack

F

Compression strut

Tension tie

Cracking reduces tensile breakout capacity

46

Anchors Affected by Cracking

Welded Headed Studs

Behavior in uncracked and cracked concrete

47

Anchors Drastically Affected by Cracking

Displacement controlled post-installed anchors

Behavior of fully and partially expanded anchors in uncracked and cracked concrete

ADHESIVE ANCHOR BOND FAILURE

48

Anchor Adhesive Concrete

N

N

hef


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49

Background of Concrete Failures

Concrete Breakout Failure

Adhesive Anchor Failure Modes

Adhesive Anchor and Sustained Loads

Adhesive Anchor Failure Modes

50

Concrete cone failure

Bond failures

Adhesive/substrate Adhesive/threaded Mixed

Anchor steel

failure

Adhesive Bond Behavioral Models

Bond failure• Uniform bond stress

• Elastic bond stress

Combined cone/bond failure

51

Uniform Bond Failure Model

52

Nbond

hef

da

Nbond = da hef

da = diameter of anchor rodhef = embedment depth = average bond stress

Elastic Bond Stress Model

53

do = hole diametermax = maximum bond stress at surface’ = elastic stiffness property of systemhef = embedment depth

maxuniform

Nu = max do [ (√do /’ ) tanh {’(hef ) / √do }]

Combined Cone-Bond Model

54

do = hole diameter’ = elastic stiffness property of systemkc = coefficient for breakout

max = maximum bond stress at surfacehef = total embedment depthhcone = depth of breakout cone

Nu = Ncone + Nbond

Nu = kc h2cone √fc’ + max do [ (√do /’ ) tan {’(hef – hcone ) / √do }]


19 – 20 Marzo 2015

March 2015 10

Uniform Bond Model and Tests

55

0

100

200

300

400

500

600

0 10000 20000 30000 40000 50000 60000

Lo

ad (

KN

)

measured loads

mean - uniform bond model

5% fractile - uniform bond model

Bond Area (A b ) (mm2)

Only 17 of 891 data points below 5% fractile (1.9%)

Why Uniform Bond Stress Works

56McVay, Cook, Krishnamurthy (1996)

Bond stress at adhesive/concrete interfacewith increasing load

SecondaryShallow Cone

Bond Failure and Breakout Failure

57

Bond failure

Breakoutfailure

58

Influence of Cracked Concrete

0.30mm

ADHESIVE ANCHORS AND SUSTAINED LOADS

59

Case Studies

Creep failure

Boston -90 “Big Dig” Tunnel

Central Artery/Tunnel (CA/T)

July 10, 2006

Ceiling Panel Collapse

60


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March 2015 11

Boston “Big Dig” Tunnel

61

NTSB

NTSB = National Transportation Safety Board

Failure Sequence

62


63

NTSB

64

Boston Tunnel Decision

The Application

Choice

The Rejected Solution

The Aftermath

Hanger plate

One hanger

was found an

inch below

the ceiling,

another

half an

inch

low.

Hanger rod connects to ceiling


65

NTSB

Poor Installation(photos from NTSB and newspaper files)

66

Red area is adhesive not bonded to concrete


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March 2015 12

Anchors Not Qualified for Sustained Loads

(FHWA Laboratory Testing)

67

Fast Set

Standard Set

NTSB Findings

NTSB – Cause: poor creep resistance of fast-set adhesive anchors subjected to sustained tension load

NTSB – Conclusion: insufficient understanding by designers and lack of standards on adhesive anchors in sustained tension

NTSB – Conclusion: unlikely that all the adhesive anchors were installed in a manner that would ensure maximum anchor performance

68

Atlanta 17th Street BridgePedestrian Walkway Canopy Collapse

August 13 , 2011

69

Canopy-Fence Structure Epoxy adhesive anchors

• 7/8-in [22 mm] diameter

• Core drilled holes: 1 1/8 in. [32 mm]

• 4 anchors per frame

• Anchored to outside (south) face of concrete parapet through flange in column assembly

• No specification for anchor material or adhesive system

• No specification for hole diameter or embedment depth Sufficient embedment to develop tension

service load of 4,000 lb. [17.8 kN] per anchor

Canopy Failure August 13, 2011 at 11:20 PM

• Approximately 7 years after construction

190 ft. [623 m] long section of canopy-fence detached from south parapet and fell onto roadway below

19 canopy support frames along east end fell

No injuries and only minor vehicle damage reported

GDOT immediately removed remaining canopy structure on south side

Parapet wall

Visual Assessment of Anchor Holes Videoscope observations


19 – 20 Marzo 2015

March 2015 13

Laboratory Investigation

Assessment of adhesive material• Epoxy based material

• Poor mixing

• Poor proportioning

• Incomplete filling of holes

Core 55d split for visual assessment

Laboratory Observations

74

Published Report Conclusions Primary causes of failure related to

epoxy anchor adhesive:• Poor resistance to long-term creep

• Sustained tensile loading

Secondary causes• Disproportionate mixing of adhesive components

• Incomplete mixing of adhesive components

• Inclusion of air voids

• High temperature in service

Conclusion not fully justified

Japan Sasago Tunnel

Ceiling Panel Collapse

December 2 , 2012

76

Japan Sasago Tunnel

Sasago Tunnel about 59 miles [90 km] west of Tokyo

Opened in 1977

Early glass capsules

Ceiling collapse -December 2, 2012

77

Cross Section

Single center support

Panel dimensions

• 16 feet long [5 m]

• 4 feet wide [1.2 m]

• 3 inches thick [8 cm]

• Weigh 2,400 lbs [10.7 kN]

78


19 – 20 Marzo 2015

March 2015 14

Ceiling Anchors Overhead installation

79

Collapse Consequences

9 motorists killed Design, construction, and inspection records

confiscated Entire tunnel anchor system inspected Was it solely a creep (time-dependent)

failure or installation?

80

Conclusions

Report indicated that ceiling collapse caused by multiple reasons• Found significant number of anchors not

installed properlyPoorly installed anchors did not perform as-designed

Found designer did not consider a differential pressure load on dividing wall • Center wall may have been loaded to more than

twice design load

81

Case Study Summary

Anchors in each case study failed because of sustained loading – TIME EFFECTS

Anchors also found to have installationdefects• Incomplete mixing of adhesive• Voids in adhesive around the anchor rod• Unclean holes

Under designed for the loads

82

TIME

Investigations of the creep behavior of adhesives

83

Sustained Load Characteristics of Adhesive Anchor Products

84


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March 2015 15

Incremental Load Rate Short-term Test

Load held for 2 minutes

Sustained Load – Creep Test Setup

86

Creep Test Results at Different Bond Stress Levels

See appendix G for all creep curves

Failure

Stable

42 days -standard sustained load test

88%MSTL

68-75% MSTL

57% MSTL

36-45% MSTL

Mean Short Term Load (MSTL)

Creep Stress vs. Time-to-Failure

Intersects 5 min at 75%

Short-term tests%

of M

ean

Sho

rt-t

erm

Loa

d S

tre

ngth

Tests conducted at 1100 F (420 C)

Bottom Line on Sustained Loads

Keep bond stress at an appropriate lower level

Design Life: 50 years, 100 years? Temperature Expectations: Indoor, Outdoor? ACI 318-11 & ACI 355.4-11: 50 years with up

to 10 years of this at 110 oF [43 oC]

89Data plot courtesy of Hilti AG

Creep Test on 16mm Capsule Anchor

ACI 318-11 APPENDIX D CODE

90


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March 2015 16

SCOPE OF ACI 318-11

Appendix D

91 92

ACI 318-11 Appendix D, ACI 355.2-07and ACI 355.4-11

ACI 318-11 Section 8.1.3 (Analysis and Design –General Considerations) • Makes Appendix D mandatory for design of anchorage

to concrete ACI 318-11 Section 3.8.7 (Materials)

• Makes qualification by ACI 355.2-07 mandatory for post-installed mechanical anchors designed according to Appendix D

ACI 318-11 Section 3.8.7 (Materials) • Makes qualification by ACI 355.4-11 mandatory for

post-installed adhesive anchors designed according to Appendix D

93

D.2.1 - Scope

Anchors used to transmit tension, shear, or combinations thereof

Safety levels (load and - factors) for in-service conditions

Not intended for • Short-term handling

• Construction loads

• Fatigue

• Blast (impact)

94

D.2.2 - Scope . . .

Included in scope:• Cast-in anchors

• Post-installed mechanical expansion anchors

• Post-installed adhesive anchors

95

D.2.2 - Scope . . .

Not included :• Specialty inserts – coil loops

• Through-bolts

• Multiple anchors connected to single plate at the embedded end of the anchors

• Grouted anchors - coming

• Concrete screws - coming

96

. . . D.2.3 & D.2.4 : Scope

Post-installed mechanical and adhesive anchors do not have a generically predictable pullout capacities

Post-installed mechanical and adhesive anchors must be qualified by testing according to ACI 355.2 and ACI 355.4

Seismic load effects covered in Appendix D


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97

D.3.1 & D.3.2 – General Requirements

Factored loads from elastic analysis• Load combinations by § 9.2 and by § D.4.4

Plastic analysis permitted if ductile steel elements used in the anchor • Must consider deformation compatibility and

ductility of anchor (more information later) Must consider group effects (see § D.3.1.1

table)

D.3.3 - Seismic Design Requirements

Seismic load effects covered • Applicable to Seismic Design Categories (SDC)

C, D, E, and F

• Anchors must pass the seismic test protocol in the qualification standards - ACI 355.2 and ACI 355.4

• No special requirements for SDC A and B

Multiple options exist for seismic design –discuss details after covering other sections of Appendix D

98

99

D.3.4 & D.3.5 – General Requirements

Adhesive anchors installed horizontally or upwardly inclined• Must be qualified by ACI 355.4

• Must be installed by certified installer when subjected to sustained load

D.3.6 – Lightweight Concrete Lightweight concrete modification factor, a

Modification factor• Cast-in and undercut concrete failure: a = 1.0 • Expansion and adhesive anchors concrete failure: a = 0.8

• Adhesive anchor bond failure: a = 0.6 1.0 excluded

determined by Section 8.6.1 1.0 normal weight 0.85 sand-lightweight 0.75 all-lightweight

100

101

D.3.7 – Concrete Strength

Code equations are valid for :• fc 69 MPa for cast-in anchors• fc 55 MPa for post-installed anchors

Post-installed anchors in concrete with fc > 55 MPa must be tested according to ACI 355.2 or ACI 355.4

102

D.4.1 – Failure Modes in Tension

Yield and fracture of anchor steel Concrete breakout Pullout / pull-through Concrete side-face blowout Bond failure for adhesive anchors

• Sustained loading limit for adhesive anchors0.55 Nba > Nua,sustained (Eqn. D – 1)

Splitting failure must be precluded (§ D.8)

Weakest Governs


19 – 20 Marzo 2015

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103

D.4.1 – Failure Modes in Shear

Yield and fracture of anchor steel Concrete breakout Concrete pryout

Splitting failure must be precluded (§ D.8)

Weakest Governs

104

D.4.2 – Nominal Strength

Design models must be in substantial agreement with test results

Nominal design strength is based on 5 % fractile of basic individual anchor strength• 90% confidence that 95 % of actual strengths

will exceed nominal strength

105

Objective of Code Requirements

Load

Resistance

Load and Resistance Magnitudes

Pro

bab

ility Limit probability

of failure toacceptable level

106

Calculation of 5% Fractile Conduct large number of tests Derive an average equation Determine 5% fractile “design” resistance

value

5 % Fractile

Average (Mean) Strength Statistical parameters

•Average (mean)

•Standard deviation

•Coefficient of variation

•Number of samples

Test Capacity

Fre

qu

ency

Characteristic value“Nominal Design

Strength”

107

D.4.2.1 Supplementary and Anchor Reinforcement

Supplementary reinforcement • Reinforcement that acts to restrain the concrete

breakout but is not designed to transfer the full design load (Condition A, higher Φ’s)

Anchor Reinforcement• Reinforcement used to transfer full design load

• Anchor reinforcement takes the user out of Appendix D and into the reinforcing bar development length rules of Chapter 12

108

Anchor Reinforcement for Tension

Note : Reinforcement perpendicular to direction of load is not effective in shear friction


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109

Anchor Reinforcement as Noted in §D.4.2.1

Chapter 12

Anchor reinforcement used when concrete breakout strength by Appendix D is insufficient – concrete breakout will occur

Increasing for concrete breakout does not help

Use the provisions of ACI 318-08 Chapter 12 , and splice anchors to reinforcement to resist the design actions

A strength reduction factor of 0.75 is used in design of anchor reinforcement

110

Anchor Reinforcement for Shear

Anchor reinforcement has to be in the direction of the applied force and near the point of crack initiation

111

D.4.2.2 – Size Limitation(any anchor type)

For concrete breakout only

• Diameter 4 in [102 mm]

• No limitation on hef

Updated for 2011(was ≤ 50mm)

Updated for 2011(was 635mm)

D.4.2.3 – Embedment Depth Limitations For Adhesive Anchors

Limits of embedment depth for adhesive anchors

4 da ≤ hef ≤ 20 da Design using bond model of § D5.5

satisfactory

112

DESIGN FOR TENSIONACI 318 Appendix D - Section D.5

113

Photograph courtesy of Ambex

114

D.5 – Design for Tensile Loading

D.5.1 – Steel Strength D.5.2 – Concrete Breakout Strength D.5.3 – Pullout Strength D.5.4 – Concrete Side-face Blowout Strength

• D.5.4 Applies to headed anchors only

D.5.5 –Bond Strength of Adhesive Anchors• D.4.1.2 Limit on sustained load magnitude


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Tension Design

Designer must consider the following tension failure modes for adhesive anchors: • Steel failure

• Concrete breakout failure

• Bond failureSustained load (creep) failure

115

Why so many failure modes to check for a single design case?

For the best solution• Must look at all the

failure modes individually

But can the design be simplified?• Can the designer go

back to using manufacturer design tables?

116

117

Can it be simplified?

Yes, it can be simplified! We could develop one equation with all the

failure modes just like the development length equations in Chapter 12 • Development length equation incorporates:

steel strength, splitting, bond, and closely spaced bars are all in one equation

• Must have minimum ℓd = 300 mm

118

Consequences of simplification

Anchors are usually installed perpendicular to the member not parallel like reinforcing bars

The simplified “one-equation” approach to anchor design will result in a need for increased member thickness.

Try telling the owner that you need to double the slab thickness so that you can do an easy design!

Increased structural depth

Development for reinforcing bar

Using simplified “one-equation” approach for anchor design

Evaluation of each potential failure mode for anchors

Steel Failure Mode - Tension

Steel rupture

119

Nsa = Ase futa (D – 2)

futa < 1.9 fyfuta < 860 MPa

Concrete Breakout Failure Mode –Tension Cone Breakout

Courtesy of University of Stuttgart


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March 2015 21

FracturedConcrete

Model reflecting actual behavior

Embedment Depth

Model used in design

Cone Breakout Model

121

N N

122

Concrete Breakout (Tension)

NnNn

Single anchor not near an edge

Single anchor near an edge

Spacing > 3hef

hef

Edge distance>1.5 hef

Concrete Breakout (Tension)

123

Anchor group with over lapping breakout cones

Spacing < 3hef

D.5.2.1 - Concrete Breakout Strength of Anchor Group (Tension)

Accounts for post - installed anchor (splitting)

Accounts for cracking

Accounts for edge effects

Accounts for eccentricity

Accounts for projected area of failure surface Basic single anchor strength

Applies to only anchors in tension

Ncbg = (ANc /ANco ) ec,N ed,N c,N cp,N Nb (D-4)

124

D.5.2.2 - Basic Single Anchor Breakout Strength

Single anchor in tension in cracked concrete

Nb = kc a (fc’)1/2 (hef )3/2 (D – 6)

kc = 10 for cast - in anchors

kc = 7 for post - installed anchors

a = Lightweight concrete modification factor

Note: an adhesive anchor should be considered like a post-installed anchor even though there are no wedging forces developed at embedded end for concrete breakout

125

User Friendly CCD Design Model for Concrete Breakout – Projected Area ANco

hef

1.5hef

1.5hef

1.5hef

Plan ViewElevation

ANco = 9hef

1.5hef

Nn

1.5hef 1.5hef

2

350

126


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March 2015 22

Concrete Breakout with Groups and Edges - Projected Area ANc

ca1 s1 1.5hef

1.5hef

Ca2

s2

ef1 h0.3s

efa2 h5.1c ef2 h0.3s

efa1 h5.1c

Limit

127

Corner

ANc ≤ nANco

128

D.5.2.6 – No Cracking Influence

Uncracked Concrete (ft < fr at service load)• Cast-in anchors: c,N = 1.25

• Post-installed anchors: c,N = 1.40 where kc = 7 in Eq. (D - 6)

• When product evaluation testing is based on ACI 355.2 or 355.4 and the anchors are used in cracked and uncracked concrete, then : kc and c,N are determined from the evaluation report

• When product evaluation testing is used to determine kc,uncr then: c,N = 1.00

D.5.5.1- Bond Strength of Adhesive Anchor Adhesive Group

Nag = (ANa /ANao) ec,Na ed,Na cp,Na Nba (D-19)

Tension failure = Bond failure < Concrete failure

129

Accounts for splitting



Accounts for projected area of influence areaBasic single anchor bond strength

D.5.5.2. - Basic Bond Strength

Single anchor in cracked concrete

Nba = a cr da hef (D-22)

cr = 5% fractile result in cracked concrete from ACI 355.4

a = Lightweight concrete modification factor for adhesive anchors

a,lightweight = 0.6 normal [0.6 factor not applicable for normal-weight concrete]

130

h ef-

incr

easi

ng

s -

cons

tant

h ef-

cons

tant

s

–de

crea

sing

da

hef

hef

da

da

hef

s

da

s

da

s

da

Adhesive Anchor Group Failure

131

s

s

s

Influence Area for Single Adhesive Anchor

132


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March 2015 23

Critical Spacing and Edge Distance

Cast-in-place and post-installed mechanical anchors• ACI 318-11

scritical = 2ccritical = 3.0 hef

Bonded anchors• ACI 318-11

scritical = 2ccrtical

where: ccritical = cNa = 10 da (uncr / 7.6)1/2 (D – 21)

133

Critical Spacing and Edge Distance for Adhesive Anchors

1390 psi [9.9 MPa]

2850 psi [19.6 MPa]

Eligehausen, Cook, Appl (2006)

Influence Area for Bond Failure of Adhesive Anchor Groups (ANa)

ca1 s1 cNa

cNa

Ca2

s2

1 2 s

a2 cNac

22 cNas

a1 cNac

Limit

cNa

ANa < n ANao

Corner

135

D.5.2.2 – No Cracking Influence

Where conditions indicate that there is no cracking under service conditions

Use uncr instead of cr

uncr - comes from manufacturers product qualification sheet (ACI 355.4)

136

D.5.2.4 & D.5.5.3 - Eccentricity Effect

For anchor groupsec,N = 1 / (1 + [2e’N / 3hef ]) (D – 8)ec,Na = 1 / (1 + [e’N / cNa ]) (D – 23)

where e'N s/2

Biaxial tension eccentricity

ec,N = (ec ,N)x (ec, N)y

ec,Na = (ec ,Na)x (ec, Na)y

137

Calculation of Eccentricity

138


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D.5.2.5 and D.5.5.4 Edge Effects

If ca,min > 1.5 hef or cNa

edN or edNa = 1.0 (D–8 / D-24)

If ca,min < 1.5 hef or cNa

ed,N = 0.7 + 0.3 (ca,min / 1.5 hef) (D – 10)ed,Na = 0.7 + 0.3 (ca,min / cNa) (D – 25)

139

ca,min

140

D.5.2.3 - Anchors Close to 3 or 4 Edges

Where 3 or more edge distances 1.5 hef

Use hef in code equations containing hef equal to the larger of :

• ca,max / 1.5, and• (1 / 3) maximum spacing between anchors

where ca,max = maximum distance from anchor to edge

141

Determine Fictitious Embedment Depth, hef'

Fictitiously move the actual concrete breakout surface toward the free surface of concrete until it first contacts the free surface

Consider a square concrete pier :

hef

hef'

Actual concrete breakout surface

Fictitious concrete breakout surface,by § D.5.2.3

142

Reason for Fictitious Embedment Depth, hef’

In the equation for calculating ANco, hef appears in the denominators of the single and group design equations for concrete breakout strength, and the denominator increases as a function of hef

2

In the basic single anchor concrete breakout strength, hef

appears in the numerators of the single and group equations and the numerator increases as a function of hef

1.5

If hef' is not determined in accordance with § D.5.2.3, the result is an overly conservative prediction for concrete breakout strength

143

AssumedFailure Surface

4 in.

Expected Failure Surface

Nn

9 in.

6 in.

5.5 in.

5 in.

Point A

Expected Failure Surface Assumed Failure Surface

5.5 in.h’

ef

h’ef

Fictitious h’ef Larger of

ca,max/1.5 = 6/1.5 = 4 in.

s/3 = 9/3 = 3 in.

Fictitious Embedment, hef’

144

D.5.2.7 – Post-installed Anchors in Uncracked Concrete Without

Supplementary Reinforcement

cp,N is a modifier accounting for splitting

If ca,min cac

cp,N = cp,Na = 1.0 (D-11) & (D-26)

If ca,min < cac

cp,N = ca,min / cac ≥ 1.5 hef / cac (D-12)cp,Na = ca,min / cac (D-27)

where cac is defined in § D.8.6

For cast-in-place anchors cp,N = 1.0

ca,min = Minimum edge distance


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145

D.5.3 – Pullout Strength

Straightened out L-bolt anchor(pullout)

Npn

146

D.5.3 – Pullout Strength

Npn = c,P Np (D-13)

Headed stud / bolt

Np = 8 Abrg fc' (D-14)

J - bolt or L - bolt

Np = 0.9 fc' eh da (D-15)

where 3 da eh 4.5 da

147

Bearing Area Abrg

Abrg

148

Distance eh for L - and J - bolts

eh

da

149

D.5.3 – Pullout Strength Post-installed Anchors

For post - installed expansion and undercut anchors , Np cannot be calculated using generic formulas Np must be based on results of tests

performed and evaluated per ACI 355.2

150

D.5.3.6 – Pullout Strength Cracking Modifiers

Uncracked Concrete c,p = 1.4• (ft < fr at Service Load)

Cracked Concrete c,p = 1.0


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151

D.1 - Definitions

Side - Face Blowout Strength

The strength of fasteners with deeper embedment but thinner side cover corresponding to concrete spalling on the side face around the embedded head while no major breakout occurs at the top concrete surface

Applies to cast-in-place anchors only

Side–face Blowout Failure

Local side-face blowout caused by bearing pressure (stress) of head on concrete (should be ~8fc’) producing lateral force

Nsb = 1/ Nb

• Lateral force (Nsb) a function of the tension force on anchor

• depends on the bearing pressure beneath the head

153

D.5.4.1 – Side-face Blowout

Single headed anchor with deep embedment , close to edge ( ca1 < 0.4 hef )

Nsb = 13 (ca1) (Ab)0.5 (fc’)0.5 (D-16)

If perpendicular edge distance ca2 < 3 ca1 , modify Nsb by :

( 1 + ca2 / ca1 ) / 4

where 1.0 ca2 / ca1 3.0154

D.5.4.2 – Side-face Blowout

For multiple headed anchors with deep embedment , close to edge (hef > 2.5 ca1) or (ca1 < 0.4 hef) and s < 6 ca1

Nsbg = [1 +s / (6ca1)] Nsb (D-17)

where

s = distance between outer anchors along edge

Nsb is from Eq. (D - 16) without modification for perpendicular edge distance (ca2)

155

D.8.6 – Critical Edge Distance, cac

Post-installed Anchors

Without tension test data from ACI 355.2 or ACI 355.4:

- Adhesive anchors ≥ 2 hef

- Undercut anchors ≥ 2.5 hef

- Torque-controlled anchors ≥ 4 hef

- Displacement-controlled anchors ≥ 4 hef

D.4.3 - Phi Factors - Tension

Steel failures• Ductile steel = 0.75• Brittle steel = 0.65

Concrete breakout and adhesive bond failures•

156

Condition A Condition B

Category 1 0.75 0.65




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D.5.5.2 - Code Guidance for Bond Stress Design

Environment Concrete moisture

Peak service temperature

cr uncr

Outdoor Dry to fully saturated

79o C 1.4 MPa 4.5 MPa

Indoor Dry 43o C 2.1 MPa 7.0 MPa

157

For sustained tension load, multiply table cr and uncr values by 0.4

For seismic design in SDC C, D, E, and F, multiply table cr value by 0.8 and uncr value by 0.4

DESIGN FOR SHEARACI 318 Appendix D - Section D.6

159

Photograph courtesy of Hilti AG

160

D.6 – Design for Shear Loading

D.6.1 – Steel Strength D.6.2 – Concrete Breakout Strength D.6.3 – Concrete Pryout Strength

Note: No special code clauses for the shear design of adhesive anchors

161

D.6.1 – Steel Failure ( Shear )

Concretecrushing

Void

Shear force

Vn

Steel Failure - Shear

Void behind the anchor

163

D.6.1.2 – Steel Strength (Shear)

(b) Cast-in headed and hooked anchor bolts, and post-installed anchors (including adhesive anchors) without sleeves extending through shear plane

Vsa = (0.6 )Ase,V futa (D - 29)

where futa 1.9 fya

890 MPa- With built-up grout pads, use 0.8 Vsa


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164

D.6.2 – Concrete Breakout (Shear)

Edge distance

Vn

Concrete Breakout (Shear)

Concrete Breakout (Shear)

167

D.6.2.2 – Basic Single Anchor Concrete Breakout (Shear)

Single anchor in shear in cracked concrete

e = hef for anchors with uniform stiffness over hef

e 8 da

e = 2 da for torque - controlled expansion anchors with a distance sleeve separated from expansion sleeve

Expansion sleeve

Distance sleeve

Vb = 0.6a (e / da)0.2 da

0.5 fc’ 0.5 (ca1)

1.5 (D -33)

D.6.2.2 – Basic Single Anchor Concrete Breakout (Shear)

Single anchor in shear in cracked concrete

Vb = 3.7 a (fc’)0.5 (ca1)

1.5 (D - 34)

Use the smaller of D-33 or D-34

168

Shear Breakout Test Database(no limit on anchor diameter)

169

Data point with new equation

Fit of new ACI 318-11provisions

Data point with old equation Fit of old provisions

Diameter da (in)

Vte

st/

Vp

red

icte

d


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170

Front view

Vn

Edge of concrete

Plan view

Vn

hef

Side section

ca1

35o

1.5ca1 1.5ca1

1.5ca1

1.5ca1

1.5ca1AVco

AVco = 2 (1.5ca1) (1.5ca1)= 4.5(ca1)2

(D-32)

Projected Area for Single-Anchor Shear Breakout

171

D.6.2.1(b) – Concrete Breakout Strength of Anchor Group (Shear)

Vcbg = (AVc / AVco) ec,V ed,V c,V h,V Vb (D-31)

Accounts for projected area of failure surface



Accounts for cracking

Accounts for thickness

Basic single anchor strength

172

AVcca1

1.5ca1 1.5ca1s1

Vn

ha

AVc = (2 x 1.5ca1 + s1)ha

If ha < 1.5ca1 and s1 < 3ca1

Projected Area for Shear Breakout (Groups)

173

ca1ha

AVc

If ha < 1.5ca1

AVc = (2 x 1.5ca1) x ha

Vn /2

Vn /2

1.5ca1 1.5ca1


174

ca1

AVc

1.5ca1 1.5ca1

Vn

ha

If ha < 1.5ca1

AVc = (2 x 1.5ca1)ha


175

D.6.2.4 – Anchors Close to 3 or 4 Edges

Where 3 or more edge distances 1.5 ca1 Effective ca1 used in Eq. (D - 30) through (D - 39) must not exceed the largest of :• ca2 / 1.5• ha / 1.5• ( 1 / 3 ) maximum spacing between anchors


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176

D.6.2.4 – Anchors Close to 3 or 4 Edges

c’a1

9 in. 8 in.

Vn

Point A

5 in. 7 in.

Assumed Failure Surface for Limiting ca1

ca1 =12 in.

Expected Failure Surface

Shear Parallel to Free Edge

Concrete breakout

ca2 = 4da

178

D.6.2.1(c)-(d) – Shear Parallel to Edge

Vn perp

2Vn perp

Actual Compute

Compute shear strength perpendicular to edge, Vn perp

Based on testing, shear strength parallel to edge = 2 Vn perp

179

D.6.2.1(c)-(d) – Concrete Breakout Strength (Shear)

For shear force parallel to edge (ed,V = 1 )• Vcb = 2 [ Vcb per Eq. (D-30)]• Vcbg = 2 [ Vcbg per Eq. (D-31)]

At corner, use smaller of :• Shear strength perpendicular to edge• Shear strength parallel to edge

D.6.2.5 – Eccentricity Effect

180

Edge of concrete

ca1

D.6.2.5 – Eccentricity Effect

For anchor groups

consider only anchors resisting shear in direction of load, that is, shear perpendicular or shear parallel to free edge

181

ec,V = 1 / (1+ 2ev’ / 3ca1) (D-36)


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182

D.6.2.6 Side-Edge Effect

ca1

Vn

1.5ca1ca2

D.6.2.6 – Side-edge Effect

If ca2 1.5 ca1

ed,V = 1.0 ( D - 37 )

If ca2 < 1.5 ca1

183

( D - 38 )ed,V = 0.7 + 0.3 ( ca2 / 1.5 ca1)

184

For uncracked concrete (ft < fr ) at service load c,V = 1.4

For Cracked Concrete

• c,V = 1.0 No reinforcement * or < No. 12 bar

• c,V = 1.2 With reinforcement * No. 12 bar

• c,V = 1.4 With reinforcement * No. 12 bar

( enclosed within stirrups w / spacing 100 mm)

* Edge or Supplementary Reinforcement

D.6.2.7 – No Cracking Effect

185

D.6.2.7 – No Cracking Effect

c,V = 1.0

c,V = 1.2

c,V = 1.4

D.6.2.8 – Correction for Thickness

Testing fact – concrete breakout strength in shear not linear with member thickness as breakout model would predict and can provide higher capacities

If ha < 1.5 ca1 , that is, when the breakout projects to the bottom of the slab, then an addition correction is needed

h,V = ( 1.5 ca1 / ha ) 0.5 (D – 39)

186 187

D.6.3 – Concrete Pryout

Vn


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Concrete Pryout - Shear

189

D.1 - Definitions

Concrete Pryout Strength

The strength corresponding to formation of a concrete spall behind a short , stiff anchor with an embedded base that is displaced in the direction opposite to the applied shear force

190

D.6.3 – Concrete Pryout

Single Anchor Vcp = kcp Ncp (D - 40) Group of Anchors Vcpg = kcp Ncpg (D - 41)

where:

• kcp = 1.0 for hef < 64 mm.

• kcp = 2.0 for hef 64 mm

• Ncp = Na computed from Eq. (D - 18)

• Ncpg smaller of Nag [Eq. D - 19] and Ncbg [Eq. D - 4]

D.4.3 Phi-factors - Shear

Steel failure• Ductile steel, shear loads = 0.65• Brittle steel, shear loads = 0.60

Concrete breakout and adhesive bond failure• Shear loads, Condition A = 0.75• Shear loads, Condition B = 0.70

191

193

D.7 - Tension / Shear Interaction

Nu

Nn

0.2 Nn

0.2 Vn Vn

Vu

[Nua /Nn ] 5/3 + [Vua /Vn ]

5/3 = 1.0

[Nua /Nn ] + [Vua /Vn ] = 1.2

(D – 42)

D.7 – Tension / Shear Interaction The values used in the denominator of the

interaction equation are the required strengths determined in § D.4.1.1 or § D.3.3.3 (seismic)

194


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D.7 – Tension / Shear Interaction

What happens if anchor reinforcement is used?

This means that if you design anchor reinforcement for either tension or shear, or both, the interaction equation does not have to be checked

195

SPLITTING FAILURES

196

197

Concrete Splitting Failure – Prescriptive

NnNn

NnNn

Design Method for Splitting Failure Mode of Adhesive Anchors, ACI SP-283 Paper No. 6 by Jorg Asmus

Concrete Splitting Failure

199

D.8 – Preclude Splitting Failure

At design stage, specific products may not be known

In absence of supplementary reinforcement for crack control, Section D.8 sets minimum requirements for cover, spacings, member thickness

Lesser values are permitted per ACI 355.2 and ACI 355.4

200

D.8.3 – Edge Distance

Post - Installed Anchors

Edge distance must exceed the largest of :

Cover per Section 7.7 Twice the maximum aggregate size Minimum edge distance for product per

ACI 355.2 and ACI 355.4


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201

D.8.3 – Minimum Edge Distance


Without product – specific information from ACI 355.2 or ACI 355.4:

- Adhesive anchors ≥ 6da

- Undercut anchors ≥ 6da

- Torque – controlled anchors ≥ 8 da

- Displacement – controlled anchors ≥ 10 da

D.8.5 – Minimum Thickness

Expansion & Undercut Anchors

Without product - specific information from ACI 355.2 :

• hef must not exceed the larger of

2 / 3 member thickness

member thickness minus 4 in.

202

203

D.8.6 – Critical Edge Distance, cac


Without tension test data from ACI 355.2 and ACI 355.4 and without supplementary reinforcement to control splitting :

- Adhesive anchors ≥ 2 hef

- Undercut anchors ≥ 2.5 hef

- Torque-controlled anchors ≥ 4 hef

- Displacement-controlled anchors ≥ 4 hef

204

D.9 – Anchor Installation and Inspection

§ D.9.1• Anchors to be installed by qualified personnel• Installation in accordance with Manufacturer’s

Printed Installation Instructions (MPII) § D.9.2

• Extensive installation, inspection, and proof load requirements

SEISMIC CONSIDERATIONS

Chilean Earthquake February 27, 2010 - 8.8 magnitude

205

D.3.3 - Seismic Design Requirements

Seismic load effects covered • Applicable to Seismic Design Categories

(SDC) C, D, E, and F § D.3.3.2 – Anchors in plastic hinge zones

excluded § D.3.3.3 - Post-Installed Anchors shall be

qualified for earthquake loading per ACI 355.2 or ACI 355.4 Simulated Seismic Tests

206


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March 2015 35

Simulated Seismic Tests

Tension Shear

207

50%75%

Neq = 0.5 No,mean Veq = 0.5 Vo,mean

50%75%

208

D.3.3 – Seismic Design Requirements (Tension)

§ D.3.3.4.2 – Anchors carrying tension in structures assigned to SDC C, D, E, or F• If

The tensile component of the strength-level earthquake force is equal to or less than 20% of the total factored anchor tensile force associated with same load combination

• Then

Design using the normal design procedure in § D.5 and § D.4.1.1

209


D.3.3.4.2 - Anchors carrying tension in structures assigned to SDC C, D, E, or F• If

The tensile component of the strength-level earthquake force is exceeds 20% of the total factored anchor tensile force associated with same load combination

• Then

Design using rules in § D.3.3.4.3 and anchor design tensile strength is determined by § D.3.3.4.4

210


§ D.3.3.4.3 - Anchors carrying tension and their attachments shall satisfy one of the options (a) through (d)

(a) Ensure anchor ductility, that is, use 1.2 times the nominal steel strength, provide a stretch length

(b) Anchor designed for tension force associated with expected strength of the metal attachment

(i) Anchor design by § D.3.3.4.4

(c) Design for maximum tension which can be transmitted by a non-yielding attachment


(d) Design for maximum tension obtained from load combination with E, but with E increased by o


(ii) Recommended o about 2.5

211

D.1 - Stretch Length

212


§ D.3.3.4.4 - Anchor Design Tensile Strength

a) 0.75Ncb or 0.75Ncbg (need not be calculated if anchor reinforcement is used)

b) 0.75Npn

c) Nsa for single anchor or most highly stressed

d) 0.75Nsb or 0.75Nsbg

e) 0.75Na or 0.75Nag


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213

D.3.3 – Seismic Design Requirements (Shear)

§ D.3.3.5.1 – Anchors carrying shear in structures assigned to SDC C, D, E, or F• If

The shear component of the strength-level earthquake force is equal to or less than 20% of the total factored anchor shear force associated with same load combination

• Then

Design by § D.6 and § D.4.1.1

214


§ D.3.3.5.2 - Anchors carrying shear in structures assigned to SDC C, D, E, or F• If

The shear component of the strength-level earthquake force is exceeds 20% of the total factored anchor shear force associated with same load combination

• Then

Design by § D.3.3.5.3 and anchor design shear strength is determined by § D.6


§ D.3.3.5.3 – Anchors carrying shear and their attachments shall be design using one of the options (a) through (c)

(a) Ensure ductile yielding mechanism in attachment

(b) Design for the maximum shear that can be transmitted by non-yielding attachment

(c) Design for maximum shear obtained from load combination with E, but with E increased by o

(i) Anchor design by § D.4.1.1

(ii) Recommended o about 2.5

215 216

D.3.3.7 – Seismic Anchor Reinforcement

Anchors in structures assigned to SDC C, D, E, or F• Use deformed bar reinforcement

• ASTM A615 Grades 280 and 420 satisfying 21.1.5.2(a)(b) (Grades 520 and 550 not permitted)

• ASTM A706 Grade 420 (Grade 550 not permitted)

Tension

Shear

DESIGN FOR MOMENT (ECCENTRIC SHEAR)

217

Photograph courtesy of Hilti AG

218

Using ACI 318-11 Appendix D for Designs Involving Moment (Eccentric shear)

Effect of baseplate flexibility on:• Design tensile anchor forces in connections with

multiple rows of anchors

• Design moments in baseplates

Effect of friction on design shear forces in anchors


19 – 20 Marzo 2015

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219

Base Plate Flexibility Plane sections do not remain plane – beam

theory is not exactly correct, but close enough

For design purposes, bound the solution

• To size the anchors for tension, assume a flexible baseplate. This gives the smallest internal lever arm, and the largest design axial forces in the anchors

• To size the baseplate, assume a rigid baseplate. This gives the largest distance from the assumed location of the compression reaction to the critical point on the baseplate

220

Flexible Base Plate . . .

x = 0 (conservative for anchor tension)x = plate thickness (a reasonable assumption)x = Mp / C (reality for a flexible baseplate)

221

. . . Rigid Base Plate

This assumption is conservative for computing the design moment in the baseplate, because it places the compressive reaction at the tip of the baseplate

222

Effect of Friction on Design Shear Forces in Anchors

Regardless of baseplate flexibility, most shear resistance is provided by friction

ACI 318 - 11 conservatively neglects friction

If friction is neglected, assume that the shear is transferred by the anchors closest to the nearest free edge

If friction is assumed to exist, use = 0.4 and assume that the shear is transferred to the anchors closest to the compression resultant

223

Multiple Rows of Anchors Load Distribution :

Loads in anchors are distributed according to stiffness (elastic design) or strength (plastic design)

Kinematics :Deformations of each anchor must be consistent with the deformations of the attachment

Embedment

T1T2 C = T1 + T2

C

V1 V2 V3

V = V1 + V2 + V3 + C

Attachment Anchor

V

224

Summary –Calculating Anchor Design Forces

Baseplate rigidity: flexible or rigid Elastic approach: anchor forces vary linearly

with distance from axis of rotation; capacity governed by critical anchor

Plastic approach: anchor forces are limited by anchor capacity; redistribution among anchors is possible if anchors are ductile; sufficient embedment is required to develop anchor capacity


19 – 20 Marzo 2015

March 2015 38

ACI QUALIFICATION TESTING STANDARDS

ACI 355.2 :Qualification of Post-Installed Mechanical Anchors in Concrete and Commentary

ACI 355.4 :Qualification of Post-Installed Adhesive Anchors in Concrete and Commentary

226 227

Scope of ACI 355.2 and ACI 355.4 355.2 Post-installed mechanical anchors

• Undercut anchors• Torque-controlled expansion anchors• Displacement-controlled expansion anchors

355.4 Post-installed adhesive anchors • Only polymeric adhesives

Conventional cast-in anchors do not require qualification (headed bolts, rods with nuts, J- and L-bolts, welded headed studs)

228

ACI 355.2 and 355.4 Prescribes Four Types of Tests

Identification tests

Reference tests

Reliability tests

Service-condition tests

229

Qualification - General Requirements

Concrete• Low- and high-strength concrete:

Low [17-24 MPa] High [45-55 MPa]

Cracked and uncracked concrete • Static tests• Crack-width cycling

Seismic cycling Evaluation by an Independent Testing and

Evaluation Agency (ITEA)

230

ACI 355.2 and 355.4 Identification Tests

Check conformance to product description• Generic or trade name• Anchor element

DimensionsPhysical propertiesTensile strengthHardnessCoatings

• Identification markings

• Quality-control requirements

Additional ACI 355.4 Identification Tests

Check conformance to product description• Adhesive components

Fingerprinting of adhesive materials

231


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232

ACI 355.2 and 355.4Reference Tests

Objective - establish baseline performance of anchors for comparison with Reliability and Service-condition tests

Objective - establish characteristic anchor performance data

For Uncracked Concrete• Tension tests in low- and high-strength concrete

For Cracked Concrete, add :• Crack width [0.3 mm] expected under service loads

233

Setup for Static Testing in Cracked Concrete

Splitting tool

234

ACI 355.2 and 355.4Reliability Tests

Objective - evaluate the reliability of the anchor for safe and effective behavior • Measure the sensitivity to changes in the

reference test installation and under adverse service condition characteristicsCrack widthDrill-bit diameterRepeated loadingCrack-width cycling

Cracked Concrete Testing

235

236

Setup for Crack Cycling Test Additional ACI 355.4 Reliability Tests

Sensitivity to hole cleaning Sensitivity to moisture

• Dry installation• Water-saturated installation• Water-filled installation• Submerged installation

Sensitivity to mixing effort Sensitivity to freeze and thaw cycling Sensitivity to sustained load Sensitivity to installation direction

237


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Hole Cleaning – Dry Concrete

238

Method of hole cleaning

Bo

nd

str

ess

ca

pa

city

, %

Influence of Moisture

0

5

10

15

20

25

30

35

A B C D E F G H I J K L M N O P Q R S T

Ave

rage

Uni

form

Bo

nd S

tre

ngth

, M

Pa

DRY HOLE (BASELINE)

DAMP HOLE

WET HOLE

239

Sustained Load – Creep Test Setup

240

Adhesive Mixing

241

Incomplete mixing – nonuniform color Completely mixed material

242

ACI 355.2 and 355.4 Category Classification

Classify anchor based on ratio between performance in reliability and reference tests

% of Reference Capacity

Category 1 80 or above Category 2 70 - 79 Category 3 60 - 69(anchor not unqualified below 60unless penalty taken)

243

ACI 355.2 and 355.4Service-Condition Tests

Determine basic data required to predict the performance of anchors under service conditions• Verify full concrete capacity in a corner with

edges located 1.5 hef away• Establish minimum spacing and edge distances

to preclude splitting on during installation (torqueing) and tension loading

• Seismic tension• Establish shear capacity of anchor steel (may be

calculated)


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Additional ACI 355.4 Service-Condition Tests

Verify anchor behavior under• Elevated temperature installation• Curing time at low temperatures • Resistance to alkalinity• Resistance to sulfur

244

Influence of Temperature

245

ACI 355.2 and 355.4 Evaluation Report

Independent Testing and Evaluation Agency • Evaluates test results• Issues a report classifying the anchor for use

with ACI 318 Appendix D Bond Stress in the Evaluation Report is the

5% fractile including effects of all variables

246

Evaluation Report Data

247

INSTALLERCERTIFICATION

ACI 318-11 D.9.2

248

Courtesy of Hilti AG

Adhesive Anchor Installer Certification

A New ACI 318-11 Requirement

249

D9.2.2, D9.2.3, and D.9.2.4


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How Did We Get Here (Part 1)?

Adhesive anchors • Versatile connection in the engineer’s toolbox• Installation to follow Manufacturer’s

instructions Design parameters now codified

• Structural design• Material performance

250

How Did We Get Here (Part 2)?

2006 Boston experience revealed many issues . . . . • Manufacturer’s instructions vary• Structural design procedures had not been

formulated • Material performance consistency was somewhat

established in International Code Council-Engineering Service – Acceptance Criteria 58 (ICCC-ES AC58)

• Installation is not easy NTSB Report – misses real and primary

cause251

“use its building codes, forums, educational materials, and

publications to inform design and construction agencies of the potential

for gradual deformation in anchor adhesives under sustained tensile-

load applications”

NTSB Recommendation to ACI How Did We Get Here (Part 3)?

To get approval of adhesive anchors by ACI Committee 318, certification was imperative • Critical connections• Installation can be plagued with errors• On par with structural welding

Design provisions + product qualifications + installer certification

= quality and serviceable anchorages

253

Factors Influencing Bond Strength

Drilling method

Hole cleaning

Mixing

Installation• Wet concrete

• Submerged

Shelf life

Hole Diameter

Embedment depth

Temperature

Freezing and thawing

Chemicals • Alkalinity

• Sulfur

Sustained loading

Fatigue / seismic

Fire

Cracked concrete

Curing

Many factors are installer dependent – Certification necessary

ACI’s Response to NTSB

ACI 318-11 Building Code, addresses adhesive anchors

ACI has a standard for adhesive anchors (ACI 355.4) “Acceptance Criteria for Qualification of Post-Installed Adhesive Anchors in Concrete and Commentary”

Partnered with the Concrete Reinforcing Steel Institute (CRSI) to identify criteria for an Adhesive Anchor Installer (AAI) and develop a certification program


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Appendix D, Section D.9.2.2

D.9.2.2 — Installation of adhesive anchors horizontally or upwardly inclined to support sustained tension loads shall be performed by personnel certified by an applicable certification program. Certification shall include written and performance tests in accordance with the ACI / CRSI Adhesive Anchor Installer Certification program, or equivalent.

256

Façade Attachment(sustained tension in downhand application)

257

MHinge or hard

welded connection

Appendix D, Section D.9.2.3

D.9.2.3 — The acceptability of certification other than the ACI / CRSI Adhesive Anchor Installer Certification shall be the responsibility of the licensed design professional.

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Summary

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Ap

pen

dix

D -

Des

ign

Adhesive Anchor Installer Certification

Objective: Get classroom and practical training Show minimum level of competencyBe tested and certified by a trade association

And you ask, “Why do we need Certification?”

Actual hidden camera on a jobsite


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Adhesive Systems

Nozzle mixing

• Zigzag type of nozzle tube

Capsule

• Insert in hole, break packaging, and mix

Bulk mixed

• Component A

• Component BNot included in program

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Quickly, Program Consists of: Training

• Classroom instruction

• Exposure to equipment and practice

75 question written examination• Closed book, 90 minutes

A performance examination for• Vertical Down

• Vertical Overhead - Piston Plug

• Vertical Overhead - Retaining Cap

Installation Training Materials

264

Terminology

Manufacturers Printed Installation Instructions (MPII)

Provides detailed instruction specifically required for the product being used. Includes items such

as storage temperatures, assembly of system, hole drilling and preparation, injection of product,

setting of anchors, gel time, cure time.

Adhesive Anchor Installer Criteria

Ability to read, comprehend, & execute anchor installation instructions

Assess ambient conditions, condition of concrete, materials, equipment, & tools

Determine when to proceed with installation or get additional guidance from supervisor

Pass written & practical exams Certification is valid for 5 years


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Local Certification Examinations

ACI Local Sponsoring Groups (LSGs) to• Support local training by manufacturer

Following a MPII is essential

• Maintain equipment and provide manpower

• Train the examiners

Conduct the 2-part examination

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Performance Specifics

Downhand vertical position (1)• Concrete cylinder (block)

• Hole clean-out procedures

• Random choice of product

Overhead vertical position (2)• Acrylic tube

• Hole filling imperative

• Cap & piston plug systems

269

Vertical Down or Downhand

Hole depth Perpendicularity of hole Hole cleaning technique Initial discharge of adhesive product Adhesive dispensing Rod / bar installation

270

Hole Drilling

Hole normal to surface

Correct depth

Removal of concrete dust spoil

Downhand – Depth Verification

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Hole Cleaning

Brush for each hole diameter

Brush sized for multiple hole diameter range

Nylon or steel

Mechanical means

Hand tool means

Wire Brush

SDS Chuck


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Hole Cleaning Hole Cleaning

Hole Cleaning Adhesive Anchor Bond Failure

Poor hole cleaning was the culprit for this failure

278

At a minimum –

( Blow – Brush – Blow )

Downhand – Injection Prep

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Nozzle Mixed System

280

Mixing & Express Material

281

Downhand - Injection

282

Downhand - Insertion of Rod

283

Installation – All Thread

284

Installation – Reinforcing Bar

285


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Overhead Vertical

Tube of finite length & diameter Blind installation Adhesive dispensing

• Straight or flexible despensing tube• Proprietary systems

286

Horizontal and Upwardly Inclined Installation (Overhead Vertical)

Tube of finite length & diameter Blind installation Adhesive dispensing

• Straight or flexible dispensing tube

• Proprietary systems

287

Blind Horizontal Installation - Practice

Pumping action of hand

Withdrawal of injection tube

288

Blind Filling in Tube

Poor filling

Poor filling

Better filling

289

Not as easyas it looks

Overhead Test – Simulation Tube

290

1 in. x 8 in. long simulated hole

Pumping action of hand

Withdrawal of insertion tube

• User speed

• Proprietary gizmo

Testing Set-up

291


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Testing Set-Up Blind Insertion & Injection - 1

Piston plug system

293

Blind Insertion & Injection - 2

Bottom cap system

294

Testing Set-Up

Overhead – Retaining Cap

Adhesive installation technique is important !

Overhead – Retaining Cap


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Overhead – Retaining Cap Overhead – Retaining Cap

Overhead – Retaining Cap Overhead – Retaining Cap

Evaluation of Overhead Tests Evaluation of Overhead Tests

• Cutting of Hardened Test Specimens

• Initial Pilot – all were sectioned

• Second Pilot all were cut longitudinally

• Size and location of voids are key

• Grading rubric


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Evaluation of Overhead Tests

• Longitudinal cutting of hardened test specimens

• Size and location of voids are visually examined

• There is a rubric of acceptance

AAI Certification Review

Manufacturer training Written test

• Environmental conditions

• Equipment / materials

• OSHA issues

Performance test• Downhand vertical into concrete

• Vertical overhead into a tube

Certification good for 5 years305

SPECIFYING ANCHORSSuggestions for information to show on drawings

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Specifying Adhesive Anchors

Strongly suggest presentation on record drawings

Drawings and specs. get separated after the job

Can incorporate info. into specs.

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Adhesive Materials (Notes 1 – 3)

List of adhesive products• Must meet ACI 355.4• No bulk-mixed materials permitted

Furnish as a complete system List assumptions:

• τ cr = (cracked concrete bond stress)

• τ uncr = (uncracked concrete bond stress)

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Anchor Materials (Notes 4 – 6)

List of anchor product types• All - thread• Stainless rod• Hardware

Reinforcing bars• Only A615, A706, or A995 permitted

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General Installation (Notes 7 – 11)

Concrete strength > 17 MPa Concrete age of at least 21 days

• This is NOT a strength requirement !!• Moisture content issue

Temperature of substrate & material Anchor stick-out minimum?

310

Installation Technique (Notes 12 – 14)

Trained and / or certified installers• Submit qualifications

What anchors need certified installers?• Suggested designation of (CERT)

311


Furnish all equipment Hole drilling

• Rotary impact hammer drill• Cored holes too smooth

Hole cleaning• Follow the MPII !!• Some variation of BBB• Protect from contamination

312


Use the nozzle that came with the product• Full length nozzle• No hardened material within

Clean anchors

DO NOT DISTURB( . . . the anchors)

313

Field Quality Control (Notes 24 – 28)

Inspection• Horizontal to upwardly inclined

• Sustained tension

• Continuous inspection required by ACI 318 for overhead installation

Proof testing Criteria for pass / fail Frequency of added testing, if failure

occurs

314

Tension Proof Testing Suggestions –Adhesive Anchors

2 x allowable service load ~ 0.7 characteristic bond strength ~ 0.5 average ultimate bond strength

• Note that the allowable service load is used, not the calculated service load

80 percent of the rod steel yield strength

Obviously use whichever is smaller

Short-term loadingSilva, J. and Mattis, L. [2011], Special Inspection Guidelines for Post-installed Anchors, Concrete Anchor Manufacturers Association (CAMA), St. Charles, Missouri, June, 13 pp. (available from the CAMA website)

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¿Preguntas?(Questions?)

¡Gracias!(Thank you)

Documents

ICH Anchorage to Concrete Seminar 3-19-2015 Anchorage to Concrete Seminar ... • ACI 355.4-11, qualification of Post-installed Adhesive Anchors in Concrete and Commentary