1、Code Requirements for the Design of Precast Concrete Diaphragms for Earthquake Motions (ACI 550.5-18) and Commentary (ACI 550.5R-18) Reported by Joint ACI-ASCE Committee 550 ACI 550.5-18 An ACI Standard First Printing June 2018 ISBN: 978-1-64195-017-6 Code Requirements for the Design of Precast Conc
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14、damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. 1 ACI
15、550.5-18 was adopted June 6, 2018, and published June 2018. Copyright 2018, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, writ
16、ten, or oral, or recording for sound or visual reproduc- tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. ACI 550.5-18 Code Requirements for the Design of Precast Concrete Diaphragms for Earthquake Motions (ACI 5
17、50.5-18) and Commentary (ACI 550.5R-18) An ACI Standard Reported by Joint ACI-ASCE Committee 550 Larbi M. Sennour*, Chair Lance Osborne, Secretary Suzanne Aultman Roger J. Becker* Te-Lin Chung Ned M. Cleland* Manuel Conde Fuentes Thomas J. DArcy* William K. Doughty Semeh Ibrahim El Ashri Alvin C. Er
18、icson Mostafa Mohamed Gad Alla Harry A. Gleich Neil M. Hawkins Augusto H. Holmberg L. S. Paul Johal Jason J. Krohn* Emily B. Lorenz Kenneth A. Luttrell Vilas S. Mujumdar Clay J. Naito* Clifford R. Ohlwiler Victor F. Pizano-Thomen Charles L. Pizzano Jose I. Restrepo* Sami H. Rizkalla Mario E. Rodrigu
19、ez* Joseph C. Sanders* James Schroder John F. Stanton P. Jeffrey Wang Cloyd E. Warnes Michael H. Weber *Diaphragm Subcommittee members who developed this code Diaphragm Subcommittee Chair Special thanks to S. K. Ghosh and S. Nakaki for their contributions to this standard. This standard describes co
20、de requirements for the design of precast concrete diaphragms subject to earthquake motions where used under the design provisions of ASCE/SEI 7-16 Section 12.10.3 and ACI 318. The response of precast concrete diaphragms under earthquake motions depends primarily on the strength, stiffness, and defo
21、rmation capacities of the connectors and the reinforce- ment at joints between the precast concrete members. The seismic forces specified in ASCE/SEI 7 for the design of precast concrete diaphragms, their chords, and collectors in structures assigned to Seismic Design Category (SDC) C, D, E, or F ar
22、e tied to force reduction factors specified in ASCE/SEI 7-16 Chapter 12, and to the shear overstrength provided by the connections and the rein- forcement at joints specified in ASCE/SEI 7-16 Chapter 14. The shear overstrength depends on the design methodology, elastic or ductile, used for the diaph
23、ragm and targets elastic response for the maximum considered earthquake for shear connections regard- less of the design option selected. The design option that can be used depends on the assigned design category and on the span and aspect ratio of the diaphragm. The selection of the design option i
24、s associated with minimum requirements for the tensile deformation capacity of the connections and the reinforcement at joints. Keywords: connections; diaphragms; earthquake-resistant structures; precast concrete; seismic design.CONTENTS CHAPTER 1GENERAL, p. 3 1.1Introduction, p. 3 1.2Scope, p. 4 1.
25、3Structural drawings, p. 4 1.4Units, p. 5 CHAPTER 2NOTATION AND DEFINITIONS, p. 6 2.1Notation, p. 6 2.2Definitions, p. 6 CHAPTER 3REFERENCED STANDARDS, p. 8 CHAPTER 4GENERAL CONSIDERATIONS, p. 9 4.1General design considerations, p. 9 4.2Materials, p. 9 4.3Minimum thickness, p. 9 4.4Tolerances, p. 9
26、CHAPTER 5DESIGN FORCES, SEISMIC DEMAND LEVELS, AND ANALYSIS, p. 11 5.1General, p. 11 5.2Diaphragm seismic design force, p. 11 5.3Diaphragm seismic demand level, p. 12 5.4Diaphragm nominal shear strength, p. 13 5.5Diaphragm modeling and analysis, p. 15 CHAPTER 6DIAPHRAGM DESIGN OPTIONS, p. 17 6.1Gene
27、ral, p. 17 6.2Elastic design option, p. 20 6.3Basic design option, p. 20 6.4Reduced design option, p. 20 CHAPTER 7DIAPHRAGM CONNECTIONS AND REINFORCEMENT AT JOINTS, p. 21 7.1General, p. 21 7.2Connection classifications, p. 21 7.3Deformed bar reinforcement, p. 22 7.4Special inspection, p. 22 R8COMMEN
28、TARY REFERENCES AND ACRONYMS, p. 23 R8.1References, p. 23 R8.2Acronyms, p. 23 American Concrete Institute Copyrighted Materialwww.concrete.org 2 DESIGN OF PRECAST CONCRETE DIAPHRAGMS FOR EARTHQUAKE MOTIONS (ACI 550.5-18) AND COMMENTARYR1GENERAL R1.1Introduction Precast concrete diaphragms are extens
29、ively used for parking structures and residential and commercial build- ings. Those diaphragms frequently consist of large precast, prestressed concrete members such as double-tee (DT) or hollow-core (HC) members. Double-tee members are connected to one another through discrete mechanical connection
30、s or by reinforcement that crosses the joint between members. Industry practice is to use these DT diaphragms in an untopped condition in buildings assigned to SDC A and B, and in a topped condition in buildings assigned to SDC C, D, E, or F. Hollow-core members are primarily used in an untopped con
31、dition in buildings assigned to SDC A and B. Design requirements for precast concrete diaphragms are covered by the general provisions of ACI 318. However, unless a precast concrete diaphragm includes a topping that meets all the prescriptive requirements for diaphragms in Chapter 18 of ACI 318-14,
32、the precast concrete diaphragm cannot be designed directly using that chapter. For DT diaphragms made composite with a topping or without a topping, structural integrity and force transfer within the diaphragm are provided by the discrete web and chord connections that join the individual precast co
33、ncrete members. If a precast concrete diaphragm made composite with a topping or without a topping is to provide a struc- tural system with an earthquake loading performance equal to or exceeding that of a comparable cast-in-place concrete diaphragm, accurate knowledge of the strength, stiffness, an
34、d deformability of the individual connections used in the diaphragm is needed. Results from tests on individual connections in accordance with ACI Standard 550.4-18 are needed to obtain the information on stiffness, shear strength, tensile strength, and tensile deformation capacity required for the
35、design of connections and reinforcement at joints for precast concrete diaphragms satisfying the lateral load performance requirements of this standard, Section 12.10.3 of ASCE/SEI 7-16, and Chapter 18 of ACI 318-14. Post-earthquake reconnaissance following the 1994 North- ridge earthquake (Iverson
36、and Hawkins 1994) revealed that when precast concrete diaphragms with topping of 3 in. or less were subjected to significant earthquake motions, the topping was likely to crack along the edges of the precast concrete members. Consequently, reinforcement crossing the edges was susceptible to damage a
37、nd the degree of susceptibility increased as the aspect ratio for the diaphragm increased and as the larger dimension of the diaphragm between seismic-force-resisting vertical elements increased. Those observations on the behavior of large precast concrete diaphragms resulted in a comprehensive rese
38、arch study (Fleischman 2014) to develop better design models for precast concrete diaphragms and comprehensive studies of the strength and deformation capacity of diaphragm connec- tions. In the improved design methodology resulting from that research, the choice of connection type is tied to the te
39、nsion deformations and shear overstrength needed in the diaphragm to achieve the required design performance. CHAPTER 1GENERAL 1.1Introduction 1.1.1 Consistent with ACI 318 requirements for analysis, this standard specifies expected performance and design requirements for precast concrete diaphragms
40、 subject to earthquake loading. This standard is meant to replace the design procedure for precast concrete diaphragms for struc- tures assigned to Seismic Design Category (SDC) C, D, E, or F that was developed and accepted for use by ASCE/SEI 7-16 in Section 14.2.4. The procedure described herein a
41、nd that of ASCE/SEI 7-16 supplement the provisions of Chapter 18 of ACI 318-14 and do not supplant them. 1.1.2 The procedure described herein may also be used for precast concrete diaphragms in structures assigned to SDC B. American Concrete Institute Copyrighted Materialwww.concrete.orgDESIGN OF PR
42、ECAST CONCRETE DIAPHRAGMS FOR EARTHQUAKE MOTIONS (ACI 550.5-18) AND COMMENTARY 3Where connections with limited deformation capacity are used, the earthquake design forces need to be higher than for ductile connections. The choice of the appropriate over- strength that should be used in diaphragm des
43、ign requires detailed knowledge of the strength and deformation capaci- ties of the diaphragm connections for the differing combi- nations of force and deformation experienced by the connections. R1.3Structural drawings Reinforcement details in the vicinity of the connectors and the means and proced
44、ures by which the connections between the precast concrete members are completed affect the performance of the connection. Details should be speci- fied completely, including tolerances, and fully documented on the structural drawings for the diaphragm. 1.2Scope 1.2.1 This standard shall apply to pr
45、ecast concrete diaphragms and collectors that are part of the seismic-force- resisting system in structures assigned to SDC C, D, E, or F. It is permissible to use this standard for the design of the same elements in structures assigned to SDC B. 1.2.2 This standard shall apply to precast concrete d
46、iaphragms, including a) through c): a) Diaphragms that consist of a cast-in-place composite topping slab with a thickness of less than 3 in. on precast concrete members b) Diaphragms that comprise precast concrete members with end strips formed by either a cast-in-place composite topping or edge bea
47、ms c) Diaphragms of interconnected precast concrete members without cast-in-place concrete topping. 1.3Structural drawings Structural drawings for precast concrete diaphragms shall show all features of the members into which the connec- tors or reinforcement at joints are cast that are essential to
48、the intended seismic performance of the diaphragms and all details of the connections or reinforcement at joints essential for attainment of that intended performance. Essential details shall include: a) The anchorage of the connectors and reinforcement at joints into the precast concrete member b)
49、The procedures and materials by which the connection between connectors in adjacent members shall be made and the tolerances that are acceptable c) Supplemental reinforcement that shall be included in the precast concrete members to ensure that the performance of the member under earthquake loading does not materially affect the measured response of the connections between members d) The methods to be used to ensure composite action, as specified in the design, between topping and precast concrete member e) The connection of the collectors and
