ACI550.2R-13
DesignGuideforConnectionsin PrecastJointedSystems
Reported byJointACl-ASCECommittee550
AmericanConcreteInstitute
DesignGuidefor ConnectionsinPrecastJointedSystems
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Desi signGuideforConnectionsinPrecastJointed Systems
ReportedbyJointACI-ASCECommittee550
Thomas J. D'Arcy Chair
Ned M. Cleland Te-Lin ChungWilliam K. Doughty Alvin C. EricsonMelhvyn A. Galinat Harry A. Gleich
Vilas S. Mujumdar Kenneth A. LutrellClifford R. Ohlwiler Frank A. NadcaaVictor F. Pizano-Thomen Jose I. Restrepo
Mario E. Rodriguez Sami H. RizkallaJoseph C. Sanders John F StantonP.Jefsey Wg Cloyd E. Warnes
Mohammad S. Habib Neil M. HawkinsAugusto H Holmberg L. S. Paal JohalEmily B. Lorenz Jason J. Krohn
The proper detailing and design of precast concrete connectionsare essential to the performance of α precast concrete stractare. This guide provides informatioe on design detiing nd constrction of connections benween precast members in jointed systems inclueding momenr frame and strctural wal systems.
3.5-Debonding p. 7
SYSTEMS p.7 CHAPTER4-PRECAST CONCRETEFLOOR
4.1Precast systems p. 74.2-Precast for diaphragms p. 7
Keywords: bolting: coenection; debonding; ductility: erection; momentframe; peecast; pretopped: post-tensioning; structural walls; welding.
CHAPTER 5-LATERAL-LOAD-RESISTING SYSTEMS p. 8
CONTENTS
5.1Structural walls p. 85.2-Structural walls with large openings p. 85.3-Moment frames p. 8
CHAPTER1-INTRODUCTIONAND SCOPE p.2
1.2-Scope p. 2 1.1-Introduction p. 2
CHAPTER6-CONNECTIONS p.10
CHAPTER 2-NOTATION AND DEFINITIONS p.2
6.1-Strength p. 106.2Ductility p. 106.3-Volume change amodation p. 11 6.4Durability p. 116.5Fire resistance p. 11 6.6Constructibility p. 116.7-Aesthetics p. 116.8-Seismic requirements p. 11 6.9-Tolerances p. 116.10-Vertical connections p. 11
2.1-Notation p. 22.2-Definitions p. 2
CHAPTER 3-GUIDELINES FOR DESIGN p.3
3.1-Classes of connections p. 33.2-Principles of connection design p. 33.3--Anchorage to concrete p. 5 3.4Welding p. 5
intended for guidance in plnning designing executing and ACI Committee Reports Guides and Commentaries areinspeting construction. This dcment is intended for the use of individuals who are petent to evaluate the significanceand limitations of its content and remendations and who will accept responsibility for the application of the material itcontains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shallnot be liable for any loss or damage arising therefrom.
CHAPTER7-ERECTIONCONSIDERATIONS p.13
CHAPTER 8-WELDING CONSIDERATIONS p.13
8.1Steel assemblies p. 13
Reference to this document shall not be made in contractthe Architect/Engineer to be a part of the contract documents documents. If items found in this document are desired byby the Architect/Engineer. they shall be restated in mandatory language for incorporation
8.2-Galvanized steel p. 138.3-Stainless steel p. 148.5Welding practices for epoxy-coated material p. 15 8.4Reinforcement p. 14
CHAPTER 9-GROUTING p.15
CHAPTER 10-REFERENCES p. 15
CHAPTER 1-INTRODUCTION AND SCOPE
1.1-Introduction
vidually fabricated ponents. Because of the segmental Precast concrete structural systems are posed of indi-individual ponents are required to support the design nature of precast concrete construction connections betweenloads. Connections are also required to acmodate defor-mations including rotations and strains.
1.1.1 Connection methodsPrecast ponents areponents by reinforcement that protrudes from each connected by one of two methods. The first method connectsponent end spliced using proprietary hardware or bylap-splicing with a small quantity of cast-in-place concrete to plete the connection. This method is referred to asemulation or a wet connection because it involves field- placed cast-in-place concrete and mimics the behavior ofcast-in-placed monolithic structures. The second more-nents by welding bolting post-tensioning or doweling mon method of connection is dry and connects po-tions are typically less stiff than their connecting precast without using field-placed concrete. Because dry connec-ponents deformations tend to be concentrated in theconnections.
Connections should allow for easy and economicalponent casting and assembly fabrication erection le ance and crection tolerances. They should also tolerateanticipated deformation without significant loss of strength.
into five groups: 1.1.2 Connection groups-Connections are categorized
hollow core members placed on a beam ledge 1) Gravity load transferGravity loads alone such as
2) Shear transferEither vertical shear horizontal shear or both such as a double-tce flange-to-flange connection
3) Moment transferThe tension and pressionprecast moment frame and its foundation forces created by moment such as a connection between a
4)Structural integrity-Code-prescribedacmodations integrity forces; typically a connection with bination
such as moments and shear 5) Combination connection-A bination of loads
In all cases the load paths and extemal loads are accm-modated in all elements of connections (Fig. 1.1.2).
Tying all precast members to each adjacent member isessential for structural integrity as required by Chapter 16 of ACI 318-11. Such connections however should not be sorigid as to prevent member rotation or volume change strainswhen required.
1.2--Scope
2.1-Notation
2.2-Definitions
Fig. 1.1.2Wall panel to foundarion connection.
design of connections between precast concrete ponents This guide provides information on the characteristics andand between precast ponents and cast-in-place construc-tion. The proper detailing and design of precast concrete connections are essential to the performance of a precastconcrete structure.
This guide describes typical precast jointed systems andtheir conection types performance and characteristics and provides remendations for design and construc- tion. Three classes of connections are identified and theircharacteristic and key design considerations given. Also included are guidelines for designing connections and theiranchorage a description of precast systems typical lateral- load-resisting systems key design considerations and recsenpiso upm eods upnoug suanbs uo
CHAPTER 2-NOTATIONAND DEFINITIONS
= deflection amplification factorf = specified pressive strength of concrete psi (MPa)R response modification factor= strength reduction factor
ACI provides a prehensive list of definitions througho terminology.. Definitionsprovided hereinplement that resource.
precast members designed to either display significant flex- deformable connectiona class of connection betweenexpeted deformations. ibility or to yield without losing strength when subjected to
ductile connection-a class of connection betweenprecast members designed to yield and show stable hyster-reversed cyclic deformations. etic force-deformation response when subjected to expected
precast members intersect. joint-the location in a precast structural system where
gravity-only member-a member of a framing systemo jo μd jou s! pue speo Ara Xqueu soddns 1e lateral-load-resisting system.
employs a thickened top flange on precast members (typi- pretopped systema precast flooring system thatcally double tees) provided in place of field-placed topping.
precast members in which the connection between precast strong conneetiona class of connection betweenence yielding when subjected to expected deformations.
Fig. 3.1.1Precast moment frame with connection made incolumn cway froem becm-to-cofmn joints.
CHAPTER 3-GUIDELINES FOR DESIGN
connecting plate. Ductile connections can also be made withsplicing reinforcing bars by lapping or using proprietary splice sleeves. There should be sufficient strain capacity tosustain resistance through the required movement.
3.1-Classes of connections
Selection of the connection type between precast po-nents is essential to precast concrete design. Connectiontypes should be identified early in the design process based on their expected role in the structural system. Yielding ofin response to severe forces such as earthquakes. Designers reinforcement is mon in reinforced concrete structuresshould consider the location of inelastic deformation inponents and design them to acmodate the defor- mations without loss of service strength. The joint regionsplace for yielding in frames. In emulative concrete construc- dtion they are rendered ductile by the prescriptive detailingThree classes of connections are described: strong ductile requirements of the Intermational Building Code (IBC 2006).and deformable.
deformations when the structure displaces. For example a 3.1.3 Deformable-Deformable connections undergoprecast beam bearing on a rubber pad on a corbel allous rotation with little longitudinal resistance. Although rotationoccurs the vertical load-carrying strength is not impaired.The gravity-only members and connections in many seismic-resistant structures-precast and otherwiseshouldact this way. In the 1994 Northridge earthquake a number of connections lost their integrity because they relied on gravityto remain in place (Iverson and Hawkins 1994). Under ahorizontal load unseating of deformable connectors should be prevented; therefore where movement is expected some the connection’s vertical support is maintained but lateral measure of restraint is required. Note that in Fig. 3.1.3 movement is limited by the threaded rod in the sleeve.
3.1.1 Srrong-Strong connections use a hierarchicaldesign approach to ensure yielding and strain hardening willnot have to display ductile response. The absolute strength take place away from the connection. Strong connections dois less important than the ratio of capacity to demand. An example is a one-piece beam and column precast po-nent connected at midspan of the beam. When the seismicseo oddns u eus ae uedsp e suo yielding occurs in the precast beam at the column face. Thisapproach is not employed as frequently as other solutions. The concept of creating strong joints to force yielding inthe precast members away from the joint although feasible is typically used where jointing occurs at frame inflection points (Fig. 3.1.1).
3.2-Principles of connection design
its function has been defined. Use of the three classes of An appropriate connection detail can be designed onceconnections enables the designer to plan the behavior ofthe structure rather than using distributed toughness in the structure to cover all potential behaviors as is largely done in cast-in-place construction.
To achieve that goal seven design principles (3.2.1through 3.2.6) are remended in this guide
1) Relate connections to the system
2) Provide a plete load path through the system
3) Avoid ecentricities in load paths where possible
icant deformation capacity are detailed in regions where 3.1.2 DucrileDuctile connections which possess signif-inelastic deformations concentrate to form a part of theseismic-load-resisting system. Ductile connections display stable hysteresis loops when subjected to reversed cyclicyielding and cyclic strain hardening occurring at the connec- loading. Their design follows a strength hierarchy to ensuretion only. Such connections can be welded; however thestrength of welds and embeds need to be stronger than the
4) Use capacity design to control the behavior of theconnection (PCI Committee on Connection Detail 1995 1998) which is the preferred method; however strut and tie design methodology is also employed in precast concretedesign practice with good results and performances
5) Provide for ductility where needed6) Account for energy dissipation where required7) Consider constructibility.
