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1、ACI 550.1R-01 became effective September 14, 2001. Copyright 2001, 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, written, or o
2、ral, 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 Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, designin
3、g, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept re- sponsibility for the application of the material it contains. The American Concret
4、e Institute disclaims any and all re- sponsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in con- tract documents. If items found in this document are de- sired by the Architect/Engineer to b
5、e a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. 550.1R-1 Emulating Cast-in-Place Detailing in Precast Concrete Structures ACI 550.1R-01 This report provides engineers with a practical guide for detailing precast concrete s
6、tructures that should meet building code requirements in all seis- mic regions by emulating cast-in-place reinforced concrete design. This report also provides information that shows how emulative precast con- crete structures can address any or all of the provisions in accordance with ACI 318-99, i
7、ncluding those of Chapter 21, if special attention is directed to detailing the joints and splices between precast components. Keywords: ductility; elastic design; emulation; flexural strength; joint; precast concrete; precast detailing; reinforcement. CONTENTS Chapter 1Introduction, p. 550.1R-2 Cha
8、pter 2General design procedures, p. 550.1R-2 2.1Selecting a structural system 2.1.1Shear walls 2.1.2Box structures 2.1.3Moment-resisting frames 2.1.4Dual systemsframes and shear walls 2.2Ductility and hinges 2.3Design and analysis procedures 2.3.1Moment frames 2.3.2Shear walls Chapter 3System compon
9、ents, p. 550.1R-6 Chapter 4Connection of precast elements, p. 550.1R-7 4.1Connections in wall systems 4.2Connections in frame systems 4.3Other connectionsfloor diaphragms 4.4Special materials and devices Chapter 5Guidelines for fabrication, transportation, erection, and inspection, p. 550.1R-14 Chap
10、ter 6Examples of emulative precast concrete structures, p. 550.1R-15 Chapter 7Summary and conclusions, p. 550.1R-15 Reported by Joint ACI-ASCE Committee 550 Robert AustinJohn T. Guthrie Cliff Ohlwiler* Donald BuettnerNeil M. HawkinsMichael G. Oliva Clinton Calvert Mohammad Iqbal* Victor F. Pizano-Th
11、omen Te-Lin “Terry” Chung Francis J. Jacques Sami H. Rizkalla Ned Cleland* L. S. Paul JohalKhaled A. Soudki Thomas J. DArcyKen Luttrell John F. Stanton* Alvin C. Ericson* Rafael MaganaP. Jeffrey Wang Melvyn GalinatLesile D. Martin C. E. Warnes* Michael Goff Vilas Mujumdar* Chair The committee acknow
12、ledges C. E. Warnes contribution for providing the initial information on emulation to the committee. *Members of ACI 550 subcommittee who prepared this report. Subcommittee chair. Deceased. 550.1R-2ACI COMMITTEE REPORT Chapter 8References, p. 550.1R-15 8.1Referenced standards and reports 8.2Cited r
13、eferences 8.3Other references CHAPTER 1INTRODUCTION Emulative detailing is defined as designing connection systems in a precast concrete structure so that its structural performance is equivalent to that of a conventionally designed, cast-in-place, monolithic concrete structure (Ericson and Warnes 1
14、990). Emulative detailing is different than jointed design where precast elements are separated from each other but are connected with special jointing details like welded or bolted plates. As commonly applied, the term “emulation” refers to the design of the vertical or horizontal elements of the l
15、ateral-force-resisting system of a building. Emulative detailing of precast concrete structures is applicable to any structural system where monolithic reinforced concrete would also be appropriate, regardless of seismic region (Precast/Prestressed Concrete Institute 1999). Design practice in some c
16、ountries with a high seismic risk, such as New Zealand and Japan, follow design codes that address precast concrete designed by emulation of cast- in-place concrete design. Performance of joints and related details of emulative precast concrete structural concepts have been extensively tested in Jap
17、an. Because emulative precast concrete structures have been constructed there for over three decades, emulative methods for seismic design are widely accepted. Until recently, this practice has not been formally followed in the U.S. Typical details showing proportional dimensions, as well as reinfor
18、cing steel, are schematic only and are provided solely to demonstrate the interactivity of the jointing essentials. All connection details will be subject to structural analysis and compliance with contemporary code requirements. At the time of this writing, splicing reinforcing bars by welding or l
19、apping was not permitted by code whenever the bars were subjected to stresses beyond the actual yield points of the reinforcing steel being used. According to certain tests of mechanical splices reported by the California Department of Transportation (Noureddine, Richards, and Grottkau 1996), concer
20、n was expressed about staggering of mechanical splices of reinforcing bars. Staggering is not required by current and developing codes. Only reinforcing bar details essential to make the illustra- tion more understandable are shown to avoid congestion and provide clarity. Other reinforcing steel tha
21、t would typically be incorporated into a conventional design is intentionally not shown. The specification and delineation of reinforcing bars or strand sizes and locations, layers, types, and numbers is the responsibility of the designer. CHAPTER 2GENERAL DESIGN PROCEDURES A large body of technical
22、 information is available for the design of cast-in-place reinforced concrete structures, and extensive research and development is on-going for all types of cast-in-place concrete technology. Numerous text- books have been written about the behavior and design of cast-in-place reinforced concrete.
23、Design procedures and ex- amples for cast-in-place reinforced concrete are available (Cole/Yee/Schubert and Associates 1993). Building codes are regularly revised to reflect new research and technology developments, and the results are incorporated into teaching and working practice (Uniform Buildin
24、g Code; ACI 318). This knowledge for designing reinforced cast-in-place con- crete structures is readily applicable to the design of emula- tive precast concrete. The analysis and design of cast-in-place reinforced con- crete structures is based on the premise that the entire system behaves monolith
25、ically as a unit. A cast-in-place concrete structure is actually built section by section with joints be- tween the concrete placements because of limitations in con- crete placing, construction procedures, or both. Due to the continuity of the reinforcement and specific requirements for constructio
26、n joints, the structure performs as a unit. The principal element of the emulative detailing of precast con- crete is to detail a precast structure that will exhibit structural behavior similar to that of a cast-in-place structure. Construction joints, whether in prefabricated or cast-in- place conc
27、rete structures, should be located and detailed to ensure transmission of induced forces and loads in both the concrete and reinforcing steel. For precast concrete, emula- tive construction joints will likely occur at the same loca- tions as dry joints in the structural elements. Joints will usually
28、 be located at the ends of beams and columns, at both the ends and sides of floor elements, and at the joints be- tween wall elements. The essential differences between cast-in-place reinforced concrete and emulative, reinforced, precast concrete relate to field connections and assembly of the prefa
29、bricated elements. Prefabricated elements have additional design requirement for stripping, transportation, and erection loads imposed on them, but the structural analysis and element design is essentially the same for both types of construction. Using emulative methods for connecting precast concre
30、te elements, the detailing process will follow three general steps: 1. The desired structural system for resisting gravity and lateral loads is selected. A separate gravity-load-resisting frame can be combined with lateral-load-resisting shear walls, or both functions can be accomplished with moment
31、- resisting frames. System selection is often controlled by the height of the building and the span of the components as well as architectural requirements. 2. Design and detail the structure to meet the requirements of the applicable building code as if it is to be constructed of monolithic cast-in
32、-place reinforced concrete, keeping in mind that the structure will be divided into structural elements of sizes and shapes that: Are suitable for plant fabrication; Are capable of being transported; and Can be erected by cranes available to the contractor. 3. Organize the structure on paper into ty
33、pical precast ele- ments of appropriate sizes and shapes to meet the foregoing criteria. Then design and detail the appropriate connections to satisfy the requirements of the applicable building code to EMULATING CAST-IN-PLACE DETAILING IN PRECAST CONCRETE STRUCTURES550.1R-3 allow the precast elemen
34、ts to be reconnected in a way that emulates a monolithic system. The manufacture and construction of precast structures will normally follow five steps: 1. Manufacture the precast structural elements with code- compliant mechanisms for splicing the structural reinforcing bars to provide continuity o
35、f the reinforcement throughout the structure; 2. Transport the prefabricated elements to the project site if they are cast offsite; 3. Erect and temporarily secure each individual precast element; 4. Connect the reinforcing bars between the precast con- crete elements by completing the splices; 5. C
36、onnect the precast concrete elements with grout or concrete closures; and 6. Reshore horizontal elements as required. 2.1Selecting a structural system Selecting an appropriate structural system, such as shear walls, box structures, moment-resisting frames, and dual systems for both lateral and gravi
37、ty loads, can be the most important step in achieving an economical, structurally sound design. Essentially, four types of structural elements addressed in model codes are used in combination to form complete building systems. Horizontal elements include beams and slabs. Vertical structural elements
38、 include walls and columns or combinations of both horizontal and vertical elements, such as cruciform elements. These elements can be combined in various configurations to form commonly recognized lateral-load-resisting systems, such as shear walls and moment-resisting frames. Emulative detailing p
39、rinciples apply to all of them. With precast concrete, the designer has the option to select only those frames or walls necessary to resist loads under the code requirements. For seismic conditions, the elements of the gravity load frame need only meet the requirements of ACI 318-99, Section 21.9 (f
40、rame members not proportioned to re- sist forces induced by earthquake motions) and the require- ment that each precast member be connected to adjacent members. This requirement can impose additional engineer- ing considerations even when using emulation detailing. 2.1.1 Shear wallsShear walls resis
41、t forces in the struc- ture parallel to the plane of the wall. Because of the relatively large depth of the wall members in-plane, significant lateral stiffness is provided. Structures that have shear walls as the principal lateral-load-resisting elements usually perform better under earthquake load
42、ing than moment frame structures. There were failures in various degrees in six structures of Northridge. Three parking garage structures used precast elements. The other three were in cast-in-place concrete. Shear walls were intact in both systems (Iverson and Hawkins 1994). There were failures in
43、various degrees in six concrete structures at Northridge. Three of the parking structures used precast elements. Three were cast-in-place concrete. Two parking garages using PCI-recommended jointing details for double tee floor systems suffered floor diaphragm failures. Shear walls were intact on bo
44、th. The International Building Code, IBC 2000, based on the National Earthquake Hazards Reduction Program (NEHRP) (Building Seismic Safety Council 1997) recommended pro- visions, recognizes two classifications of shear walls. “Ordi- nary shear walls” are walls designed in accordance with ACI 318 Cha
45、pters 1 through 18. This includes Chapter 16 on pre- cast concrete with provisions for structural integrity. Ordi- nary shear walls are permitted in buildings in seismic performance categories: A, B, and C. These requirements do not include the seismic detailing provisions of Chapter 21. Systems bra
46、ced with ordinary shear walls are assigned a re- sponse modification factor, R, of 4.5 for load-bearing wall systems, and 5 for shear walls bracing a vertical frame. The second classification of shear walls in the IBC 2000 is “Special Shear Walls.” These walls meet the requirements for ductile detai
47、ling included in ACI 318-99, Section 21.6, “Special reinforced concrete structural walls and coupling beams.” Systems braced with special shear walls are assigned a response modification factor of 5.5 for load-bearing wall systems, and 6 for shear walls bracing a vertical frame. Special shear walls
48、are used in buildings in seismic performance categories: D, E, and F. Although not required for regions of lower seismic risk, engineers can design special shear walls for these conditions for their increased integrity, strength, and ductility, and for the reduction of base shears afforded by the hi
49、gher R factors. For ordinary precast shear walls, emulation does not pro- vide specific benefit. The level of strength and ductility re- flected by the R factors only requires the standard details used with precast and tilt-up construction. For special shear walls, however, only those walls that meet the ACI 318 Chapter 21 requirements are recognized. Precast walls, then, need to em- ulate the performance and detailing of monolithic cast-in- place walls using the rules that were developed for cast-in- place construction. At this time, the only altern