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1、ACI 373R-97 became effective May 8, 1997. Copyright 1997, 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 oral, or r
2、ecording 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 designing, plan- ning, exec
3、uting, and inspecting construction. This document is intended for the use by individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Con- crete Insti
4、tute disclaims any and all responsibility 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 contract documents. If items found in this document are desired by the Architect/Engineer to be a part of t
5、he contract docu- ments, they shall be restated in mandatory language for in- corporation by the Architect/Engineer. 373R-97-1 FOREWORD This report provides recommendations for the design and construction of circular prestressed concrete structures (commonly referred to as “tanks”) post-tensioned wi
6、th circumferential tendons. These thin cylindrical shells of either cast-in-place or precast concrete are commonly used for liquid and bulk storage. Vertical post-tensioning is often incorporated in the walls as part of the vertical reinforcement. Recommendations are applicable to circumferential pr
7、estressing achieved by post-tensioning tendons placed within the wall or on the exterior surface of the wall. Procedures to prevent corrosion of the prestressing elements are emphasized. The design and con- struction of dome roofs are also covered. Keywords: circumferential prestressing; concrete; c
8、orrosion resistance; domes; floors; footings; joints; loads (forces); prestressed concrete; pre- stressed reinforcement; reinforcing steel; roofs; shotcrete; shrinkage; tanks; temperature; tendons; walls. CONTENTS Chapter 1General, p. 373R-97-2 1.1Introduction 1.2Objective 1.3Scope 1.4History and de
9、velopment 1.5Definitions 1.6Notation Chapter 2Materials, p. 373R-97-5 2.1Concrete 2.2Shotcrete and filler materials 2.3Admixtures Design and Construction of Circular Prestressed Concrete Structures with Circumferential Tendons Reported by ACI Committee 373 Associate and Consulting ACI 373 Committee
10、Members who contributed to the development of this report: James R. Libby Chairman Steven R. Close Secretary Robert T. Bates Bradley Harris Dennis C. Kohl Daniel W. Falconer Frank J. Heger Gerard J. McGuire G. Craig Freas Thomas L. Holben Hoshi H. Presswalla Amin Ghali Richard R. Imper Morris Schupa
11、ck Charles S. Hanskat Arthur M. James Troels Brondum-Nielsen Ib Falk Jorgensen Miroslav Vejvoda ACI 373R-97 2.4Grout for bonded tendons 2.5Reinforcement 2.6Tendon systems of tank wall and domes 2.7Waterstop, bearing pad 2.8Epoxy injection 2.9Epoxy adhesives 2.10Coatings for outer surfaces Chapter 3D
12、esign, p. 373R-97-8 3.1Strength and serviceability 3.2Floor and footing design MANUAL OF CONCRETE PRACTICE373R-97-2 3.3Wall design 3.4Roof design Chapter 4Construction procedures, p. 373R-97- 19 4.1Concrete 4.2Shotcrete 4.3Forming 4.4Nonprestressed steel reinforcement 4.5Prestressing tendons 4.6Tole
13、rances 4.7Seismic cables 4.8Waterstops and sealants 4.9Elastomeric bearing pads 4.10Sponge rubber Fillers 4.11Cleaning and disinfection Chapter 5Acceptance criteria for liquid- tightness of tanks, p. 373R-97-23 5.1Testing 5.2Acceptance criteria 5.3Visual criteria 5.4Repairs and retesting Chapter 6Re
14、ferences, p. 373R-97-23 6.1Recommended references 6.2Cited references CHAPTER 1GENERAL 1.1Introduction The design and construction of circular prestressed con- crete structures using tendons requires specialized engineer- ing knowledge and experience. This report reflects over four decades of experi
15、ence in designing and constructing circular prestressed concrete structures with tendons. When designed and constructed by knowledgeable individuals, these struc- tures can be expected to serve for fifty years or more without requiring significant maintenance. This report is not intended to prevent
16、development or use of new advances in the design and construction of circular prestressed concrete structures. This report is not intended for application to nuclear reactor pressure vessels or cryo- genic containment structures. This report describes current design and construction practices for ta
17、nks prestressed with circumferential post-ten- sioned tendons placed within or on the external surface of the wall. 1.2Objective The objective of this report is to provide guidance in the design and construction of circular prestressed concrete structures circumferentially prestressed using tendons.
18、 1.3Scope The recommendations in this report are intended to sup- plement the general requirements for reinforced concrete and prestressed concrete design, materials and construction, given in ACI 318, ACI 301 and ACI 350R. This report is concerned principally with recommenda- tions for circular pre
19、stressed concrete structures for liquid storage. The recommendations contained here may also be applied to circular structures containing low-pressure gases, dry materials, chemicals, or other materials capable of creat- ing outward pressures. The recommendations may also be applied to domed concret
20、e roofs over other types of circular structures. Liquid storage materials include water, wastewa- ter, process liquids, cement slurry, petroleum, and other liq- uid products. Gas storage materials include gaseous by- products of waste treatment processes and other gaseous ma- terial. Dry storage mat
21、erials include grain, cement, sugar, and other dry granular products. The recommendations in this report may also be applica- ble to the repair of tanks using externally applied tendons. Design and construction recommendations cover the fol- lowing elements or components of tendon tanks: a. Floors P
22、restressed Concrete Reinforced Concrete b. Floor-Wall Joints Hinged Fixed Partially Fixed Unrestrained Changing Restraint c. Walls Cast-in-Place Concrete Precast Concrete d. Wall-Roof Joints Hinged Fixed Partially Fixed Free e. Roofs Concrete Dome Roofs with Prestressed Dome Ring (1) Cast-in-place C
23、oncrete. (2) Shotcrete. Other Roofs (1) Prestressed Concrete. (2) Reinforced Concrete. f. Wall and Dome Ring Prestressing Methods Circumferential (1) Individual high-strength strands in plastic sheaths or multiple high-strength strand tendons in ducts positioned within the wall and post-tensioned af
24、ter placement and cur- ing of the wall concrete, as shown in Fig. 1.1. (2) Individual or multiple high-strength strands and, less frequently, individual high-strength bar tendons, pre- stressed after being positioned on the exterior surface of the wall. Vertical (1) Individual or multiple high-stren
25、gth strand or indi- vidual high-strength bar tendons, enclosed in sheathing or ducts within the wall, anchored near the wall joints at the bottom and top of the wall. (2) Pretensioned high-strength strands in precast panels. 373R-97-3CIRCULAR PRESTRESSED CONCRETE STRUCTURES 1.4History and developmen
26、t The late Eugene Freyssinet, a distinguished French engi- neer generally regarded as the father of prestressed concrete, was the first to recognize the need to use steels of high qual- ity and strength, stressed to relatively high levels, in order to overcome the adverse effects of concrete creep a
27、nd shrink- age. Freyssinet successfully applied prestressing tendons to concrete structures as early as the late 1920s. The earliest use of circumferential tendon prestressing in the United States is attributed to the late W. S. Hewett in 1923. He designed and had built several reservoirs using cir-
28、 cumferential rods and turnbuckles. A 1932 concrete stand- pipe in Minneapolis, MN20 prestressed by tendons, designed with the Hewett System is still in use and in good condition. In the early 1950s, following methods used successfully in Europe for a number of years, several circular prestressed co
29、ncrete tanks were constructed in the United States using post-tensioned high tensile-strength wire tendons embedded in the tank walls. The post-tensioned tendons in most early “tendon tanks” were grouted with a portland cement-water mixture after stressing to help protect them against corrosion and
30、to bond the tendons to the concrete tank walls. Others were unbonded paper-wrapped individual wire or strand ten- dons that depended on a grease coating and the cast-in-place concrete for their corrosion protection. Later, the use of un- bonded tendons with corrosion-inhibiting grease coatings and p
31、lastic sheaths became more common. Most of the early tendon tanks constructed in the U.S. followed the common European practice of vertically prestressing the tank walls to eliminate or control horizontal cracking. This crack control helped prevent leakage of the contents and corrosion of the prestr
32、essing steel. Several hundred tendon-stressed tanks (with bonded and unbonded tendons) have been constructed in the United States. 1.5Definitions 1.5.1 Core wallThat portion of a concrete wall that is circumferentially prestressed. Does not include the shotcrete covercoat in an externally post-tensi
33、oned tank. 1.5.2 Joint restraint conditionsBottom and top bound- ary conditions for the cylindrical shell wall. Examples are shown in Fig. 1.2 and 1.3. 1.5.2.1 HingedFull restraint of radial translation and negligible restraint of rotation. 1.5.2.2 FixedFull restraint of radial translation and full
34、restraint of rotation. 1.5.2.3 Partially fixedFull restraint of radial translation and partial restraint of rotation. 1.5.2.4 UnrestrainedLimited restraint of radial transla- tion and negligible restraint of rotation (free). 1.5.2.5 Changing restraintA joint may be of a different type during and aft
35、er prestressing. An example is a joint that is unrestrained (free) during prestressing but is hinged after prestressing. The change in joint type is a result of grout in- stallation that prevents radial translation after prestressing. 1.5.3 Membrane floorA thin, highly reinforced, slab- on-grade des
36、igned to deflect when the subgrade settles and still retain liquid-tightness. 1.5.4 Shotcrete coverPneumatically-applied mortar covering external tendons. 1.5.4.1 Tendon coatThe part of a shotcrete cover in con- tact with the circumferential prestressing. 1.5.4.2 Body coatThe remainder of the shotcr
37、ete cover. Figure 1.1Typical tendon layout Figure 1.2Typical base restraint details MANUAL OF CONCRETE PRACTICE373R-97-4 1.5.4.3 CovercoatThe tendon coat plus the body coat. 1.5.5 TendonA steel element such as bar or strand, or a bundle of such elements, used to impart compressive stress to concrete
38、 through prestressing. In pretensioned concrete the tendon is the steel element alone. In post-tensioned con- crete, the tendon includes the complete assembly consisting of end anchorages and/or couplers, prestressing steel and sheathing or ducts completely filled with a corrosion inhibit- ing mater
39、ial. 1.5.5.1 AnchorageIn post-tensioning, a device used to anchor the tendon to the concrete member. 1.5.5.2 Bonded tendonA prestressing tendon that is bonded to the concrete either directly or through grouting. In a bonded tendon the prestressing steel is not free to move rel- ative to the concrete
40、 after stressing and grouting. 1.5.5.3 Circumferential tendonA tendon that is placed around the tank circumference, as shown in Fig. 1.1. 1.5.5.4 CouplerA device used to connect two pieces of a tendon. 1.5.5.5 Prestressing steelHigh-strength steel used to prestress concrete, commonly seven-wire stra
41、nds, bars, or groups of strands. 1.5.5.6 SheathingEnclosures, in which post-tensioning tendons are encased, to prevent bonding during concrete placement and to help protect the strand from corrosion. The enclosures are generally referred to as ducts when used for grouted multiple strand tendons. 1.5
42、.5.7 Unbonded tendonA tendon that is not bonded to the concrete section. In an unbonded tendon the prestressing steel is permanently free to move (between fixed anchorag- es) relative to the concrete. 1.5.5.8 RollerA short cylindrical segment, usually in- cluding a central concave shaped portion, Fi
43、g. 1.4, placed under an external tendon to space the prestressed element away from the core wall and reduce friction by rolling along the surface as the tendon is elongated.19 1.6Notation Ac = area of concrete at cross section considered, sq. in. Ag = gross area of unit height of core wall that resi
44、sts circumferential force due to prestressing, sq. in. Agr = gross area of wall that resists externally applied circumferential forces, such as backfill, sq. in. Aps = area of prestressed reinforcement, sq. in. As = area of nonprestressed reinforcement, sq. in. Ast = total area of reinforcement, pre
45、stressed plus nonprestressed, sq. in. D = dead loads, or related internal moments and forces Ec = modulus of elasticity of concrete under short-term load, psi. Eci = modulus of elasticity of concrete at age ti, psi. Es = modulus of elasticity of reinforcement, assumed to be the same for prestressed
46、and non-prestressed reinforcement, psi. fc = specified compressive strength of concrete, psi. fci = specified compressive strength of concrete at time of prestressing, psi. fci = the initial stress in the concrete at time ti, immediately after prestress- ing (negative for compression), psi. fg = spe
47、cified compressive strength of shotcrete, psi. fpu = specified tensile strength of prestressing strands, wires or bars, psi. fre = intrinsic relaxation of prestressed reinforcement that occurs in a ten- don stretched between two fixed points (constant strain level equal to initial strain), psi. The
48、intrinsic relaxation depends upon the type and quality of the prestressed reinforcement and the initial prestress level in the steel. Use the prestressing ten- don manufacturers relaxation data projected to age 50 years. Reference 13 also contains information on this subject. fy = specified yield st
49、rength of nonprestressed reinforcement, psi. F = loads or related internal moments and forces due to weight and pres- sures of fluids with well defined densities and controllable max- imum heights h = thickness of wall, in. hd = thickness of dome shell, in. H = loads or related internal moments and forces due to weight and pres- sure of soil, including water in soil, or stored granular materials Fig. 1.3Typical free top details Fig 1.4Roller for external prestressing 373R-97
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