1、ACI 334.3R-05 became effective September 16, 2005.Copyright 2005, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral,
2、 or recording for sound or visual reproductionor for use in any knowledge or retrieval system or device, unless permission in writingis obtained from the copyright proprietors.ACI Committee Reports, Guides, Standard Practices, andCommentaries are intended for guidance in planning,designing, executin
3、g, and inspecting construction. Thisdocument is intended for the use of individuals who arecompetent to evaluate the significance and limitations of itscontent and recommendations and who will acceptresponsibility for the application of the material it contains.The American Concrete Institute discla
4、ims any and allresponsibility for the stated principles. The Institute shall notbe liable for any loss or damage arising therefrom.Reference to this document shall not be made in contractdocuments. If items found in this document are desired by theArchitect/Engineer to be a part of the contract docu
5、ments, theyshall be restated in mandatory language for incorporation bythe Architect/Engineer.334.3R-1Construction of Concrete ShellsUsing Inflated FormsReported by Joint ACI-ASCE Committee 334ACI 334.3R-05This report provides information on the construction of structural concreteshells using an inf
6、lated form. Major facets of the construction process arecovered, including foundations, inflation, monitoring, and backup systems.Other aspects, such as the geometric variations of inflated forms, thickness ofpolyurethane foam, and mixture proportions for shotcrete, are also considered.Keywords: dom
7、e; fabric; inflation; polyurethane foam; reinforcement;shotcrete; thin shell.CONTENTSChapter 1General, p. 334.3R-21.1Introduction1.2Scope1.3History1.4Methods1.5Definitions1.6Preconstruction1.7Work scheduleChapter 2Foundations, p. 334.3R-42.1General2.2Concrete2.3Soil conditions2.4Reinforcement materi
8、al2.5Placement of reinforcement2.6Placement of anchors2.7Concrete placement2.8Foundation dowels2.9Uplift preventionChapter 3Inflated forms, p. 334.3R-63.1General3.2Inflated form material and manufacturing3.3Field layout3.4Form protection3.5Initial stretching3.6Inflation3.7Construction tolerances3.8A
9、ir pressure maintenance3.9Collapse prevention3.10Miscellaneous connections3.11Fabric form repair3.12Polyurethane foam (when used)3.13Preparation3.14Foam application3.15Construction hazardsChapter 4Shotcrete dome, p. 334.3R-94.1General4.2Reinforcement material and size4.3Clear spacing between bars4.4
10、SplicesJohn F. Abel Frederick L. Crandall Luis F. Meyer William C. SchnobrichDavid P. Billington Phillip L. Gould John C. Miller Barry SouthArthur J. Boyt, Jr. Takashi Hara Thomas E. Nelson, Jr. Jason P. SouthJames L. Byrne Michael D. Hunter John K. Parsons Arnold WilsonJohn V. Christiansen Mark A.
11、Ketchum Dale A. Pearcey L. Brent WrightMatthew S. Church Samaan G. Ladkany Ryan E. PooleDavid B. SouthChair334.3R-2 ACI COMMITTEE REPORT4.5Cover4.6Preliminary reinforcement mat (premat)4.7Shell reinforcement4.8Preconstruction shotcrete tests4.9Shotcrete compression tests4.10Proportions and materials
12、4.11Field practice4.12Nozzle operator qualifications4.13Shotcrete operation4.14Discharge time4.15Joints4.16Multi-pass technique4.17Curing4.18Shotcrete placement tolerance4.19Shotcrete damage4.20CompletionChapter 5References, p. 334.3R-135.1Referenced standards and reports5.2Cited referencesCHAPTER 1
13、GENERAL1.1Introduction (Fig. 1.1)For centuries, arched and dome-shaped structures haveefficiently enclosed large clear-span volumes. The strength ofcompound-curved surfaces allowed early builders toconstruct self-supporting thin-shell buildings from a varietyof materials. Due to the tremendous amoun
14、t of time and effortneeded to create the desired shapes, construction of thesethin-shelled structures sometimes spanned several decades.Knowledge of the design and construction of thin-shellconcrete structures has greatly increased over the past 100years, both from research and practical experience.
15、 In thepast 40 to 50 years, the use of inflated forms has allowed shellsto be constructed more economically (South 1990). This newtype of construction process presents new challenges andconcerns. Safety measures and construction tolerances areaddressed in this report for many types of systems usingi
16、nflatable forms.1.2Scope (Fig. 1.2)This report contains the lessons learned in the constructionof thin-shell concrete dome structures using inflated forms.As this method of construction continues to gain popularity,additional research is needed to increase understanding ofthe behavior of this type o
17、f shell so that inflated-form structurescontinue to meet adequate levels of safety and serviceability.Included are construction procedures, tolerances, and designchecks to ensure that the finished structure meets adequatesafety and serviceability levels. This document focusesprimarily on inflated fo
18、rm thin shells using polyurethanefoam as part of the construction process. Many structures arebuilt using fabric forms where the concrete is applieddirectly to the form either from the outside or the inside.These general guidelines apply to all methods.1.3History (Fig. 1.3)Since the early 1940s, sev
19、eral methods of construction usinginflatable forms have been used. These methods includeshotcrete applied to the form exterior, and foam and shot-crete applied to the form interior.In 1942, Wallace Neff received a patent on a system wherethe form was inflated to the shape of the structure, and thent
20、he reinforcing bar and shotcrete were placed on the exteriorof the form (Neff 1942). Dante Bini later developed andreceived a patent on a system where the reinforcement andconcrete were placed on the exterior of the form before it wasinflated. It was then raised by air pressure to form the dome(Fig.
21、 1.4) (Bini 1986).In 1972, Lloyd Turner received a patent on a process inwhich the inflated form was sprayed with foam on the insideto a desired thickness creating a self-supporting foam domeFig. 1.1Faith Chapel Christian Center, Birmingham, Ala.:280 ft (85.35 m) diameter and 72 ft (22 m) tall that
22、includesa 3200-seat sanctuary, classrooms, and an administrationbuilding.Fig. 1.2Price City Works Complex, Price, Utah. Fourdomes: 130 x 43 ft (40 x 13.1 m) fire station; 130 x 43 ft (40x 13.1 m) storage facility; 130 x 43 ft (40 x 13.1 m) mainte-nance shop; and 90 x 40 ft (27 x 12.2 m) office and a
23、dminis-tration building.Fig. 1.3U.S. Borax and Chemical Co., Boron, Calif.: two20,000 ton (18,000 tonne) borax storage domes, 150 x 79 ft(45.7 x 24.1 m).CONSTRUCTION OF CONCRETE SHELLS USING INFLATED FORMS 334.3R-3(Turner 1972). The patent was later reissued with concreteapplied to the interior of t
24、he foam (Fig. 1.5).In 1979, David and Barry South were issued patents on amethod similar to that of Turners (South 1979). Theirmethod differed in that the structure was self supporting onlyafter the shotcrete was in place (Fig. 1.6) (South 1986).All patents for the use of inflated forms in construct
25、ion ofthin shells are now in the public domain with one exception:the Crenosphere, the technique patented by David Southfor the construction of thin shell domes of diameters largerthan 300 ft (91 m) using a cable net restraint system and ribs.When the concrete is placed on the outside of the form, t
26、hecables will be buried in the concrete and function as rein-forcement. When the concrete is placed on the inside of theform, the cables are removed once the structure is solid.Bridges and arch buildings have been built using inflatedforms where inflation forces are restrained by steel hoopsplaced o
27、n the exterior of the inflated form. Some very largedome-type structures have used steel tie-down systems toallow higher inflation pressures.1.4Methods (Fig. 1.7)Inflated-form, thin-wall shotcrete construction hasbecome one of the most common and widely used methodsin the construction of domes. The
28、Monolithic Dome Instituteestimates over 2000 thin shells have been built over the last30 years using the fabric form method, whereas those builtwith conventional forming methods are few in number.Until recently, only a few contractors have possessed the skillsand the equipment necessary to undertake
29、 this type of construc-tion. As architects and engineers are becoming aware of theadvantages of this inflated form method and its use increases,industry design and construction standards are needed.Shotcrete can be placed on the inflated form from eitherthe outside or inside. Some systems use higher
30、 air pressureand the inflated fabric form to support all the loads, whereasothers support some construction loads with a reinforcementlayer and initial layers of shotcrete.Although each method has unique construction chal-lenges, they all have many similar characteristics. Thisreport does not distin
31、guish between the different methods ormake judgments as to the validity of each. It discusses theconstruction factors that are common to all of the inflatedform methods:Inflated form manufacturingshape, size, fabric, andfabrication; Foundation detailsanchor system, uplift prevention,layout, and form
32、 tension;Air pressurebackup system, monitoring, and collapseprevention; andApplied loadslive loads and dead loads.1.5Definitionsbasketthe personnel aerial lift platform that raisesworkers to work on the dome.dead loadsthe fixed weight of a structure plus any fixedloads such as attached equipment, br
33、idges, supports, headhouses, platforms, catwalks, ceilings, and conveyors restingor hanging from the structures.embedsanchor bolts, inserts, pipe sleeves, pipes,conduits, reinforcement, wiring, flashing, instruments, andother devices encased in the concrete.Fig. 1.4Construction of Bini shell. Fig. 1
34、.5Construction of Turner shell.Fig. 1.6Construction of South shell.Fig. 1.7“Eye of the Storm,” Sullivans Island, S.C.: prolateellipse residence80 ft (24.4 m) long, 57 ft (17.4 m) wide,and 34 ft (10.4 m) tall.334.3R-4 ACI COMMITTEE REPORTinflatorthe fan or blower assembly.manometerthe pressure gauge
35、for measuring the airpressure within the inflated form.preliminary reinforcement mat (premat)a grid of No. 3or 4 (No. 10 or 13) bars at approximately 2 ft (0.6 mm) oncenter, which gives the dome additional stiffness and strengthbefore the first layer of structural reinforcement is placed.reboundaggr
36、egate and cement paste that ricochets offthe surface during the application of shotcrete because ofcollision with the hard surface, reinforcement, or otheraggregate particles.shear keya longitudinal notch in the footing that acts asa mechanical shear connector between the dome shell andthe footing.s
37、hotcrete (for construction of thin shells using inflatedforms)generally a mixture of cement, sand, pea gravelwith a maximum aggregate size of 3/8 in. (10 mm), andwater projected at high velocity onto a surface. See ACI506R for more information on shotcrete.1.6PreconstructionAll-weather road access t
38、o the site should be provided forthe constructors personnel and vehicles during construction. The contract documents should provide the general layoutof the dome, including a center point and orientation fordoorways. The preconstruction and construction testingprocedures should be agreed upon betwee
39、n the owner andthe constructor. (The owner usually provides for all testingeither in-house or by use of a testing agency.)1.7Work scheduleMost of the work done inside and outside the dome is frombaskets. Because only a few people can work out of anysingle basket, production can be increased by worki
40、nglonger hours or, on larger structures, using more baskets.When spraying foam or shotcrete, schedules are greatlyinfluenced by weather conditions or how much work that canbe done at once, so flexibility is important in creating thework schedule. The constructor may work one, two, or threeshifts, ar
41、ranging their work to best fit the project require-ments. Job site cooperation is important to assure a quality,safe, and productive project, as well as to minimize the riskassociated with this method of construction (for example,relying on fans to hold up the dome).CHAPTER 2FOUNDATIONS2.1GeneralThe
42、 dome foundation usually consists of a reinforcedconcrete ring-beam footing, circular in plan, rectangular insection, and designed for anticipated loadings and soilbearing conditions. The footing usually acts as a tension ringto resist vertical and internal loads. Design considerationsinclude the si
43、ze of the dome, the occupancy, local buildingcodes, relevant national standards, and soil report (Fig. 2.1)(Billington 1982).The footing ring beam provides the foundation for thefinished structure, anchorage points for the inflated form(Fig. 2.2), the weight to resist the upward pressure of theinfla
44、ted form, and the air seal to prevent the pressurized airfrom escaping. The footing ring can also be used as a tensionring to resist the horizontal thrust of internal loading.2.2ConcreteCertification that the concrete meets ASTM C 94 shouldaccompany each concrete delivery.Concrete properties and han
45、dling should conform toACI 301 and the following:Minimum 28-day compressive strength of 3000 psi(210 MPa);Maximum coarse aggregate size of 1 in. (25 mm);Air entrainment of 6.5 1.5% (these are higher levelsthan in ACI 214R);No added calcium chloride;Water-cement ratio of 0.55 or less; andSlump of 2 i
46、n. (50 mm) minimum to 8 in. (200 mm)maximum at the point of discharge.If placed on aggressive soils, greater strength or chemicalresistance can be achieved by adjusting the mixture propor-tions. For instance, the use of sulfate-resistant cement maybe required.2.3Soil conditionsWhen soil conditions a
47、llow, excavating a trench to therequired dimensions and placing the concrete and reinforcingbars in the trench is acceptable. If trenches are not practical,then wood or metal forms can be used. The top of the footingFig. 2.1Dome edge constructions (Billington 1982).Fig. 2.2A typical anchoring system
48、.CONSTRUCTION OF CONCRETE SHELLS USING INFLATED FORMS 334.3R-5should be formed and finished to final grade and geometryfor proper inflated form attachment.Because the dome is light and the shell is monolithic, it isgenerally tolerant of differential settlement. Spread footingsare normally used, but
49、if the soils do not have adequatebearing capacity, pilings can be used to support the dome.The ring beam and the dome must always be integral. If pilesor columns are used, the ring beam can be set on top of thepiles. The conventional grade beam may not be needed, butthe ring beam is required. If the dome is built or resting uponcolumns and walls, the dome will be able to withstand differ-ential settlement, but the columns and walls may not.The footing trench should be inspected for proper beari
