GuideforDesignofAnchorage to Concrete: Examples Using ACI318AppendixD
ReportedbyAClCommittee355
AmericanConcreteInstitute
GuideforDesignofAnchoragetoConcrete: ExamplesUsingACi318AppendixD
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ragetoConcrete: ExamplesUsing 318AppendixD
ReportedbyACICommittee355
Ranjit L Bandyopudhyay Tarek S. AzizPeter J. Carrato’Harry A. ChambersRolf Eligehausen Ronald A. Cook*Sam S. Eskildsen*
Chapter 1--Introduction p.2
Donald F. Meinheit*
Wermer A. F. Fuchs Branko Galunic ueugMichael GongHerman L. Graves III Christopher Heinz*Bruce L Ireland
Decsed.
This guide prerent worked exomples using fhe derign provirioms i ACT 318 Appendix D. Nor oll ditioms re covered in rhese exmples. Theessentils of diret ension direct sher ined esin m sher d the w sitio of eccemric sher as in α brcket or corbel arepresented.
Keywords: anchorage; bined tension amd shear; design examples;eccentric shear; embedded bolts; headed-stud anchors; post-imstalled anchors shear; tension.
CONTENTS
1.i-Introduction1.3-Comentary on seismic requirements for Appendix D 1.2-Discussion on design example problemsof ACI 318-02 and ACI 318-051.4Commentary on seismic requirements for Appendix D of ACI 318-08
are intended for guidance in planning designing. executing. ACI Committee Reports Guides Manuals and Commentariesand inspecting construction. This document is intended for the use of individuals who are petent to evaluate thesignificance and limitations of its content and remendations and who will accept responsibility for the application of thematerial it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Instituteshall not be liable for any loss or damage arising therefrom.
documents. If items found in this document are desired by the Reference to this document shall not be made in contractshall be restated in mandatoey language for incorporation by Architect/Engineer to be a part of the contract documents theythe Architect/Engineer.
J.Bret Turley* Secretary
Richard E Klingner* Anthoey J. LamannaHarry B. Lamcelot IINam-Ho Lee Lee W. MattisRobert R. McGlohn*
1.5-Commentary on notation Appendix D ACI 318-08 and definitions for1.6Anchor designs featured in example problems
Chapter 2-Notation and definitions p.4
2.iNotation 2.2-Definitions
Chapter3-ACI318-05 Appendix D(reprinted) p. 7
Chapter4-Design examples p.35
4.1Example 1: Single headed anchor away from edges subjected to seismic tension4.2-Example 2: Single hooked anchor away from edges4.3-Example 3: Single post-installed anchor in tension subjected to seismic tension4.4--Example 4: Group of headed studs in tension near away from edges4.5Example 5: Single headed bolt in shear near an edge an edge4.6Example 6: Single headed bolt in tension and shear4.7-Example 7: Single post-installed anchor in tension near an edgeand shear near an edge
4.8-Example 8: Group of cast-in anchors in tension and shearwith two free cdges and supplemental reinforcement4.9--Example 9: Group of headed studs in tension near an edge with eccentricity4.10-Example 10: Multiple headed anchor connection4.11-Example 11: Multiple post-installed anchor subjected to moment and shear4.12-Example 12: Multiple headed anchor connection connection subjected to seismic moment and shearsubjected to seismic moment and shear4.13-Example 13: Group of tension anchors on a pier with shear lug
Chapter 5-References p.118
5.1-Referenced standards and reports5.2-Cited references
Appendix A-Tables p.119
Table A.2(a)Bearing area (Apr) for cast-in anchors. Table A.1Materials for headed anchors and threaded rodswith nuts and washers threaded rod with nuts and threaded rodsTable A.2(b)Dimensional properties of bolts and studs Table A.2(c)Dimensional properties of nuts for for determining bearing arca (Abrg)determining bearing area (Abrg)Table A.3Sample data for a post-installed torque- controlled mechanical expansion anchorTable A.4Sample data for a post-installed undercut anchor
CHAPTER1-INTRODUCTION
1.1-Introduction
This guide was prepared by the members of ACI 355 Anchorage to Concrete to provide design examples that demonstrate the provisions of ACI 318-05 Appendix D.Appendix D which was first introduced in ACI 318-02 contains design provisions for determining the strength of anchors based on the Concrete Capacity Design (CCD)its origins in rsearch work done at the University of Stuttgar method for concrete breakout failure. The CCD method hasin Germany (Eligehausen et al. 1987; Eligehausen and Fuchs sity of Texas at Austin in the 1990s (Fuchs et al. 1995). The 1988; Rehm et al. 1992) and was formalized at the Univer-amodel that is based on a breakout prism having an angle of CCD method calculates the concrete breakout strength usingapproximately 35 degrees rather than the traditional 45-degree cone model used since the early 1970s.
Appendix D design provisions are for both cast-in-placeanchors and prequalified post-installed mechanical anchors.Separate design equations are frequently provided because cast-in-place anchors behave differently than post-installedanchors. The provisions for post-installed anchors are only intended for those post-installed anchors that are qualifiedtion requirements in ACI 355.2 are the stanard for qualifying under prehensive testing protocols. The testing and evalua-post-installed anchors used in design with Appendix D.Similar procedures which are expected to be pleted
Table 1.1-List of anchor failure modes
Tension failure mode Shear failure modeConcrete breakout strength Steel strength of anchor Concrete breakout strength Steel strength of anchorConcrete side-face blowout strength Concrete pryout strengthPullout and pll-hrogh srengh
soon are under development for adhesive anchors andconcrete screw anchors.
1.2-Discussion on design example problems
The exam problms preented in this guide werdeveldusing the code provisions in Appendix D of ACI 318-05 which were current at the time the examples were developed. The new provisions of ACI 318-08 will alter the calculationsand results in these examples. Commentary in this guide describes how the new ACI 318-08 provisions modify thedesign results. The ACI 318-08 Appendix D provisionsclarify issues when dealing with earthquake forces ductile failure anchor reinforcement and supplemental reinforcement.
The design approach used in the example problems followsa basic outline of evaluating each potential failure mode in tension and shear for the anchor using the provisions oftion factors that account for the effects of edges eccentricity Appendix D of ACI 318-05. The provisions include modifica-and the presence or lack of cracking in the concrete totypes of failure modes considered are shown in Table 1.1. determine the nominal strengths for each failure mode. The
edge distance anchor spacing and thickness of the concrete In addition to the failure modes in Table 1.1 minimummember are checked to preclude the spliting of concrete.modified by the appropriate modification factors. The The calculated nominal strengths for each failure mode areminimum calculated design strength beesthecontrolling design srength of the anchor or group of anchors.
Appendix D of AC1 318-02 and ACI 318-05 1.3-Commentary on seismicrequirementsfor
“moderate ”d and *high" to describe the levels of seismic risk. ACI 318-02 and ACI 318-05 use the terminology “low *The design strength of anchors that include earthquakeforces and that are located in regions of moderate or high seismic risk are required to be controlled by failure in tension shear or both of a ductile steel element. In addition the design strengths for steel and concrete are reduced by a factorof 0.75. The nonductile concrete failure modes include all theconcrete breakout modes in tension and shear plus the pullout and pull-through failure modes in tension. Nonductile failurecan occur if the steel behaves in a brittle fashion. It is not always possible due to geometric or material constraints todesign the anchorage for a ductile failure. Therefore codeprovisions allow the attachment which the anchor connects to the structure to be considered as the ductile steel element.
Design Examples 1 2 11 and 12 demonstrate the provisionsof Appendix D when earthquake forces are involved. They show the design of the anchors governed by the steel strengthof a ductile steel element according to Section D.3.3.4 of
Table 1.2-Description of design example problems
Design example problem Description of problemEsample Single headed achor m tensio away from edges A single cast-inanch une si ldingmffetedby ees d lcatdinahigh seic region.Eample 2Single hooked anchor in tensin awy fm edges Se polm as Examle I b anhris a L-bol with smilr getry; th int s to shw the inherent lower capacity of the L-bolt pared with the headed boll.Eamle 3Single post-istalled hor tension y from edges Determines the optimum post-installed anchor embedmemt and diameter to support a tension load using amchor qualification testing data.EamGhdshtn Detemines the sri wind ld that can be aplid toa sinl casti an ne a fre dExample 5Single heded bolt in shear near an edpe Example 6Single headed bolt in tension and shear near The same anchr gemtry of Examle 5 is subecled a reverible shear lod anda tension d. by calculating the design sher strength with redctions de to edge effects.EsamSinle post-installe achr intsi d an edge A post-installed anchorear fre ee of cncrete is ubjcted t sher ad nsi sin Ede effets ad tensin/heritionre vadshear near an edge amchor qualification testing data. Edge effects and tension/hear interaction are evalkated. Acolm bse plate withosizeholes is ahored withgroup ofcastin anchorsTeinEsample 8Group of cast-in anchors imtension amd shear with two free edges and supplemental reinforcement amd shear lds are aplied Edge effcts tensi/shear interaction an consideratios fo supplemental reinforcement are evaluated.Example 9-Group of heded stud n tensio near an dpe with ecoentricity A simlaroup fheednch wded tla snEmle4is suptingancc tension load near a free edge of concrete. Unequal force distribution and edge effects in theExample 10-Muliple headed anchor connection anchors are considered. A groupof igt wldd eaded achrs uppots anmbded lat withanccntishadsubjected to seismic moment and shear that produces unequal force distribution among the amchor group. The free edpes require consid- eration of edge effects. Supplemntal reinforment d msion/sharnteraction are evaluat.subjected to seismic moment and shear Example 11Muliple post-installed amchor connection A gropf sipt-stalld net hs sprts ala whncic sismi shed that psalfdsimngtnrounlehrdgrpst are evaluated using sample anchor qualification testing data to povide ductile failre.Tension/shear interaction is evaluated. A group of six headed amchors welded to a plate supports an ecentric seismic shear load thatExample 12-Muliple headed anchor connection subjected to seismic moment and shear produces unequal forcdistrbtion amng e mchor group Plastic deign is used o ealuate ihe anchor and plate strength. Tension/shear interaction is evaluated.Example 13Group of tensioe anchors oen a pier with A cncrete pie supting a columbase with cas-inanchrs is evlld f lre sher and tension forces. Concrele beeakout strength is exceeded and the pier reinforcing stel is used toshear lug Itransfer the tension force. Shear lug design using provisioes of ACI 349 is included.
failure associated with concrete breakout. ACI 318-05 thus avoiding the potential problem of britle
where reinforcing steel is specifically designed to transfer all the anchorage forces into the structure without consideringthe concrete breakout strength. This anchor reinforcement design approach occurs in cases where the concrete breakout strength is insufficient due to geometricrestraints. Example 13 provides information on designing the anchorage using anchor reinforcement. Adding thisnew definition helped to distinguish the term from supple-mentalreinforcement. present in the direction of the load can provide restraint Supplementaland improve ductility for the anchorage. Although supple-mental reinforcement is not explicitly designed to transfer the load it has been experimentally shown to improveductility. thereby allowing an increase in the design strength of the connection through an increase in the phifactor. Examples 8 and 10 demonstrate the use of supple-mental reinforcement.
1.4-Commentary onseismicrequirementsfor Appendix Dof ACi 318-08
requirements for Appendix D stated in Section 1.3 of this Several changes were made from the previous seismiceditions have been correlated in ACI 318-08 to the corre- guide. The levels of seismic risk from previous ACI 318model building codes. The seismic reduction factor of 0.75 sponding design methods categories and zones shown in thethat is applied to the design strength of ductile steel has beeneliminated. For Examples 1 2 11 and 12 which are discussed in Section 1.3 of this guide the removal of this reduction factoefor steel would indicate that a brittle concrete breakout failure would control the design in most cases. Nonductile failuremodes are allowed to control seismic design in ACI 318-08 bybreakout strength. This factor when bined with the imposing an additional reduction factor of 0.4 to the concreterequired seismic reduction factor of 0.75 which is associated with concrete failure modes results in a total reduction of 0.3 and reduces the concrete breakout design strength from the ACI318-05 levels. The intent of reducing the permissible strength is to force the anchorage system to resist the earthquake loadelastically and avoid brittle failure in the concrete.
A new term e.y has been included in ACI 318-08Appendix D to provide a modification factor to increase theof the section h is less than 1.5 basic concrete breakout strength in shear when the thickness
The term for anchor diameter was changed from d to din ACI 318-08 Appendix D.
1.6--Anchor designs featured in example problems
AppendixDACI318-08 1.5-Commentary onnotationanddefinitionsfor
Table 1.2 contains a briefdescription of the anchor designsfeatured in each example problem.
A new definition “anchor reinforcement” has beendefined in ACI 318-08 Appendix D to include the situation
