2013.01.09 - aci appendix d - updates for aci 318-11

ACI Appendix D – Updates for ACI 318-11

By Mark Bartlett, PE

RLG Consulting Engineers

SE University, January, 2013 www.LearnWithSEU.com

Topics to be covered

Review of Appendix D (ACI 318-02, 05, 08) Very brief review

Major 2011 Updates to Appendix D Adhesive Anchors Adhesive Anchors Seismic Revisions Installation and Inspection of Anchors

What does IBC 2009 say about anchors?

How to correctly specify post-installed anchors

2

REVIEW OF APPENDIX D

(ACI 318-02, 05, 08)


3

Appendix D – D.2.2

Strength design method for anchorage to concrete

CIP anchors CIP anchorsHeaded bolts, Hooked bolts, Headed studs,

4

Appendix D – D.2.2

Post-installed anchorsUndercut anchors, Expansion anchors

(Sleeve anchors and Wedge anchors) and Adhesive anchors (new in 2011)Adhesive anchors (new in 2011)

Post-installed Anchors must undergo pre-qualification testing ACI 355.2 for mechanical anchors

ACI 355.4 for adhesive anchors

5

Appendix D – D.2.2 Anchors not covered

Specialty inserts

Through-bolts

Screw-type anchorsScrew-type anchors

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

Grouted anchors (not the same as adhesive anchors)

Powder or pneumatic actuated nails

6

ACI 318 - Appendix D

Strength design method for anchorage to concrete (i.e. Nu ≤ ΦNn or Vu ≤ ΦVn)

Nu & Vu – Ultimate capacities determined from service loads multiplied by load factorsservice loads multiplied by load factors

Nn & Vn – Nominal capacities determined from equations

Φ – Strength reduction factor based on factors such as failure mode, supplemental reinforcement and anchor category

7

Appendix D Design Equations & Failure Modes

Design equations check multiple failure modes Steel capacity (Tension and Shear)

Concrete breakout capacity (Tension and Concrete breakout capacity (Tension and Shear)

Pullout/Pull-through capacity (Tension)

Concrete Pryout (Shear)

Concrete side-face blowout (Tension for CIP anchors only)

Bond Strength (Tension for Adhesive Anchors only)

8

Tension Equations

Steel (D.5.1)Nsa = nAse,N futa

Concrete Breakout (D.5.2)Ncbg = ANc/ANco(Ψec,N Ψed,N Ψc,N Ψcp,N Nb)Ncbg = ANc/ANco(Ψec,N Ψed,N Ψc,N Ψcp,N Nb)

Pullout/Pull-through (D.5.3)Npn = Ψc,P Np

Concrete Side-face Blowout (D.5.4)Nsb = (160ca1√Abrg)λ√f’c

Bond Strength (D.5.5)Nag = ANa/ANao Ψec,Na Ψed,Na Ψcp,Na Nba

9

Shear Equations

Steel (D.6.1)Vsa = n 0.6 Ase,V futa

Concrete Breakout (D.6.2) Concrete Breakout (D.6.2)Vcbg = AVc/AVco (Ψec,V Ψed,V Ψc,V Ψh,V Vb)

Concrete Pryout (D.6.3)Vcpg = kcp Ncb

10

Effects of Reinforcement

Anchor Reinforcement (D.4.2.1) Where anchor reinforcement is provided in

accordance with D.5.2.9 and D.6.2.9, calculation of the concrete breakout strength in accordance with the concrete breakout strength in accordance with D.5.2 and D.6.2 is not required.

Refer to sections D.5.2.9, RD.5.2.9, D.6.2.9 and RD.6.2.9 for specific requirements

11

Effects of Reinforcement

Supplemental Reinforcement (D.4.2.1) Configuration and placement similar to anchor

reinforcement

Not specifically designed to transfer the full design Not specifically designed to transfer the full design load from the anchors into the structural member (ex. stirrups for shear reinforcement)

Condition A – with supplemental reinforcement

Condition B – without supplemental reinforcement

Explicit design of supplemental reinforcement is not required (RD.4.3)

12

Phi (Φ) factors- Section D.4.3Failure Mode

CIP

0.75CIPSide Face Blowout

Brittle

0.75Use Condition B

DuctileSteel

ShearTension ShearTension

Condition BCondition AФ Factor

Anchor Property

0.75

0.75 0.75

0.65

0.65 0.60

0.70 0.70

0.70 0.70

13

Pryout

Pullout

Cat. 3Cat. 2

Cat. 1

CIP

Breakout

Cat. 3Cat. 2

Cat. 1

CIP

Cat. 3Cat. 2

Cat. 1

CIP

0.75 0.75

0.75 0.75

0.65 0.75

0.55 0.75

Use Condition B

Use Condition B

0.70 0.70

0.65 0.70

0.55 0.70

0.45 0.70

0.70 0.70

0.65 0.700.55 0.70

0.45 0.70

0.70 0.70

0.65 0.70

0.55 0.70

0.45 0.70

What about Bond Failure?

Post-Installed Anchor Category

Category 1 Low sensitivity to installation and high reliability

Category 2 Medium sensitivity to installation and medium

reliability

Category 3 High sensitivity to installation and lower reliability

Determined from testing per ACI 355.2 Mechanical anchors only

14

Interaction of Tension and Shear - Section D.7

15

Interaction of Tension and Shear - Section D.7

If Vua ≤ 0.2ΦVn full tension allowed

If Nua ≤ 0.2ΦNn full shear allowedIf Nua ≤ 0.2ΦNn full shear allowed

OtherwiseNua Vua

ΦNn ΦVn

+ < 1.2

16

MAJOR 2011 UPDATESADHESIVE ANCHOR ADDITION


17

Biggest Change to Appendix D

Like mechanical anchors, you still need input from manufacturers

Adhesives in Appendix D

from manufacturers

More than just design equations Assumptions regarding installation conditions

Installation by trained personnel

18

Section D.2.2Minimum concrete age of 21 days at the time

of anchor installation


of anchor installation Moisture issue, not strength

Cover this information in your general notes and specs

Common that anchors are installed prior to 21 days

19

Section D.3.5Horizontal or upwardly inclined installations

and anchors subjected to sustained tension


and anchors subjected to sustained tension loading must satisfy D.4.1.2 (45% capacity reduction) Satisfy Installer certification and inspection

requirements per D.9.2.2 – D.9.2.4

These installations will be more expensive

20

Section D.3.640% reduction in lightweight concrete (20% for

expansion and 0% for CIP and undercut)


Section D.3.7 f’c < 10,000 psi for CIP f’c < 8,000 psi for Post-installed

Difficulty of expanding wedge type anchors in very high strength concrete (VHSC)

Adhesive bond strength negatively affected in VHSC

21

Section D.4.1.2Adhesive anchors resisting sustained tension

loads 0.55 ФNba > Nua,s

Adhesive in Appendix D

0.55 ФNba > Nua,s

Nba : Basic bond strength in tension per D.5.5.2

Nua,s: Factored sustained tension load

Sustained tension loads (hanging loads) are especially critical

22

Section D.5.5: Bond strength of adhesive anchor in tension

N = A /A Ψ Ψ N (D-18)


Na = ANa/ANao Ψed,Na Ψcp,Na Nba (D-18) Single Anchor

Nag = ANa/ANao Ψec,Na Ψed,Na Ψcp,Na Nba (D-19) Group of anchors

23

ANa: Influence area for a group of adhesive anchors

Adhesives in Appendix DNag = ANa/ANao Ψec,Na Ψed,Na Ψcp,Na Nba

anchors

ANao: Influence area for a single anchor ANao= (2cNa)2

cNa = 10da√(τuncr/1100)

da = anchor diameter

τuncr: bond stress (per testing / manuf.)

24

Ψec,Na : Modification for eccentric loading


Ψed,Na : Modification for edge effects

Ψcp,Na : Modification for adhesive anchors designed for uncracked concrete without supplementary reinforcement to control splitting

25


26

Manufacturer’s InfoPermitted Embedment Depth Range

27

Minimum Concrete ThicknessCritical and Minimum

Edge DistanceMinimum Anchor Spacing

Manufacturer’s InfoSteel Strength in Tension

28

Concrete Breakout Strength in Tension

Temperature Range during service life (interior or exterior conditions)

29

Continuous or Periodic Inspection

Dry or Water-saturated Concrete

Strength reduction factors (Φ factor)

Software

Use itSimpson

Hilti

PowersPowers

Free downloads

30

MAJOR 2011 UPDATESSEISMIC REVISIONS


31

Appendix D Seismic

Section D.3.3.1Additional requirements if Seismic Design

Category is C, D, E or F

Section D.3.3.2 Section D.3.3.2Appendix D does not apply for anchors

located in a plastic hinge

Section D.3.3.3Post-installed anchor must pass simulated

seismic testing

32

Appendix D Seismic

Section D.3.3.4.1 If seismic forces are less than 20% of total

tensile force, the extra requirements of section D.3.3.4.3 are not necessaryD.3.3.4.3 are not necessary

Section D.3.3.4.2 If seismic forces are more than 20% of total

tensile force, the extra requirements of section D.3.3.4.3 are necessary

33

Appendix D Seismic

Section D.3.3.4.3 Without reading the commentary, this section

is hard to followis hard to follow

Anchors and their attachments must satisfy one of options (a) through (d)

This section is trying to prevent brittle failures from occurring during a seismic event

34

Appendix D Seismic

Section D.3.3.4.3 (a)Transmit tensile loads via a ductile steel

element.Upset

element.

35

Upset Threads

Appendix D Seismic

Section D.3.3.4.3 (b) Ductile yielding of the attachment

Section D.3.3.4.3 (c) Anchor capacity limited by a non-yielding attachment

like a wood sill plate

Section D.3.3.4.3 (d) Anchors designed for maximum tension obtained

from design load combinations that include E with Eincreased by Ωo

36

Appendix D Seismic

Section D.3.3.4.4 25% reduction to anchor

tensile strength for all failure modes (except steel) given modes (except steel) given in table D.4.1.1

Assume concrete is cracked unless demonstrated that it remains uncracked

37

Appendix D Seismic

Section D.3.3.4.5When anchor reinforcement is provided, no

reduction in anchor tensile strength is reduction in anchor tensile strength is required

D.5.2.9 requires a 25% reduction in the design of the anchor reinforcement

38

Appendix D Seismic

Section D.3.3.5.1 If seismic forces are less than 20% of total

shear force, the extra requirements of section D.3.3.5.3 are not necessaryD.3.3.5.3 are not necessary

Section D.3.3.5.2 If seismic forces are more than 20% of total

shear force, the extra requirements of section D.3.3.5.3 are necessary

39

Appendix D Seismic

Section D.3.3.5.3 Shear “ductile” requirements similar to the ones for

tension loads

(a) ductile yield mechanism in the attachment (a) ductile yield mechanism in the attachment

(b) anchors designed for the maximum shear that can be transmitted to the anchors by a non-yielding attachment

(c) Anchors designed for maximum shear obtained from design load combinations that include E with Eincreased by Ωo

40

Appendix D Seismic

Section D.3.3.5.4 When anchor reinforcement is provided, no reduction

in shear strength is required

Section D.3.3.6 Section D.3.3.6 Anchors subject to both tension and shear shall be

designed to satisfy D.7 (interaction equation) with tensile strength calculated from D.3.3.4.4 (25% reduction)

Section D.3.3.7 Anchor reinforcement must be ASTM A615 Grades

40 and 60 or ASTM A706 Grade 60 41

Appendix D Seismic

Section D.3.4 Adhesive anchors installed horizontally or upwardly

inclined shall be tested per ASTM 355.4 for sensitivity to installation directionto installation direction

Section D.3.5 For adhesive anchors subjected to sustained tension

loading, D.4.1.2 (45% reduction) shall be satisfied

Installer certification and inspection requirements shall be in accordance with D.9.2.2 through D.9.2.4

42

Appendix D Seismic

Section D.3.6 Modification factor for lightweight concrete

CIP and undercut anchor concrete failure – 1.0λ

Expansion and adhesive anchor concrete failure - 0.8λ Expansion and adhesive anchor concrete failure - 0.8λ

Adhesive anchor bond failure – 0.6λ

Section D.3.7 f’c max is 10,000 psi for CIP and 8,000psi for PI

43

MAJOR 2011 UPDATESINSTALLATION AND INSPECTION

OF ANCHORS


44

Appendix D Section D.9

Section D.9.1 Anchors shall be installed by qualified

personnel in accordance with the contract documents.contract documents.

The contract documents shall require installation of post-installed anchors in accordance with the Manufacturer’s Printed Installation Instructions (MPII).

Installation of adhesive anchors shall be performed by personnel trained to install adhesive anchors. 45


Section D.9.2 Installation of anchors shall be inspected in

accordance with section 1.3 (Inspection) and accordance with section 1.3 (Inspection) and the general building code.

Adhesive anchors shall be subject to the following additional requirements (sections D.9.2.1 through D.9.2.4)

46


Section D.9.2.1 The contract documents shall specify proof loading

where required in accordance with ACI 355.4.

The contract documents shall also specify all The contract documents shall also specify all parameters associated with the characteristic bond stress used for the design including:

minimum age of concrete

concrete temperature range

moisture condition of concrete at time of installation

type of lightweight concrete (if applicable)

requirements for hole drilling and preparation

47


Section D.9.2.2 For horizontal and upwardly inclined adhesive

installations, the installer shall be certified by an ACI/CRSI Adhesive Anchor Installer Certification ACI/CRSI Adhesive Anchor Installer Certification Program or equivalent.

Section D.9.2.3 Acceptability of other certifications is the responsibility

of the licensed design professional.

48


Section D.9.2.4Horizontal and upwardly inclined installations

require continuous special inspectionrequire continuous special inspection

Inspector shall be specially approved for that purpose by the building official

49

IBC 2009 SECTION 1912


50

IBC 2009 Section 1912

Anchorage to Concrete – Strength DesignCIP anchors, expansion anchors and

undercut anchors “shall be designed in undercut anchors “shall be designed in accordance with Appendix D of ACI 318”

“The strength design of anchors that are not within the scope of Appendix D of ACI 318…shall be in accordance with an approved procedure.” Concrete screws, specialty inserts, etc.

51

Poll Question

Where do you currently specify the requirements for post-installed concrete anchors?

A. Specifications onlyA. Specifications only

B. General Notes only

C. Details only

D. Specs and Details

E. General Notes and Details

F. Specs, General Notes and Details

52

HOW TO PROPERLY SPECIFY

CONCRETE ANCHORS


53

Specifying Concrete Anchors

SpecificationsAdd a dedicated section for concrete anchors

Include both CIP and PI anchors Include both CIP and PI anchors

Sample specs can be downloaded from either Simpson or Hilti Download both and use the best parts of each one

Useful for legal reasons, but how practical is the information?

54


General NotesAdd a dedicated section for concrete anchors

Include both CIP and PI anchors Include both CIP and PI anchors

Sample general notes can be downloaded from either Simpson or Hilti These will probably not include the requirements

called out in Appendix D section D.9.2.1 minimum age of concrete, concrete temperature range,

moisture condition of concrete at time of installation, etc.

55


Details If possible, stay generic; If not, be very

specific about the anchorspecific about the anchor

Refer back to the general notes or specifications for additional information

Create a standard “anchor detail” and refer to it when possible

56


Good Term

Torque-Controlled Anchor A little wordy, but accurate

Adhesive Anchor

Bad Term

Expansion Anchor / Exp. Bolt Too generic

Epoxy Anchor Referenced in App. D;

includes rod and adhesive

Structural Adhesive Threaded rod separate

Threaded Rod Refer to General Notes for

ASTM designation

Not all adhesives are epoxies; not all epoxies are structural

Epoxy Grout or Grout Grouted anchors are different

Bolt Too generic; bolts are not fully

threaded

57


58


59


60


61


Type of threaded rod is not called out

GC may feel that he can GC may feel that he can determine the “Or Equal” alternative

62

Specifying Concrete Anchors “Drill & Epoxy Grout” is too

open ended

Older adhesives have not been tested per ACI 355.4 and are not allowed

63

not allowed Simpson SET and AT

Hilti HY 150 and RE 500

Powers Power-Fast

Acceptable versions Simpson SET-XP & AT-XP

Hilti HY150 MAX-SD & RE500-SD

Powers PE1000+ and AC100+ Gold

Specifying Concrete Anchors 8” embed. is too deep

“Exp. Bolt” is too generic

Older “Exp. Bolts” not tested per ACI 355.2 and

64

are not allowed per code Simpson Wedge-All

Hilti Kwik Bolt 3

Powers Power-Stud

Acceptable versions Simpson Strong-Bolt 2

Hilti Kwik Bolt TZ

Powers Power-Stud+ SD1


“Exp. Bolt” again Not a big deal here

¾” Exp. Bolt gets:

65

¾” Exp. Bolt gets: ≈ 5,000 lbs. tension

≈ 18,000 lbs. shear

Overkill ½” anchor acceptable

Summary

Adhesive Anchors added to Appendix D

Seismic provisions re-written

New installation and inspection New installation and inspection requirements

Proper anchor specifying is critical

Fix that stair stringer detail

66

Questions

67


By Mark Bartlett, PE

RLG Consulting Engineers

SE University, January, 2013 www.LearnWithSEU.com


2013.01.09 - aci appendix d - updates for aci 318-11

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