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The Code also covers thestrength evaluation of existing concrete structures. Among the subjects covered are: contract documents; inspection; materials; durability requirements; concretequality, mixing, and placing; formwork; embedded pipes; construction joints; reinforcement details; analysis anddesign; strength and serviceability; flexural and axial loads; shear and torsion; development and splices of reinforcement;slab systems; walls; footings; precast concrete; composite flexural members; prestressed concrete; shells and foldedplate members; strength evaluation of existing structures; provisions for seismic design; structural plain concrete; strutand-tie modeling in Appendix A; alternative design provisions in Appendix B; alternative load and strength reductionfactors in Appendix C; and anchoring to concrete in Appendix D.

The quality and testing of materials used in construction are covered by reference to the appropriate ASTM standardspecifications. Uses of the Code include adoption by reference in general building codes, and earlier editions have been widely usedin this manner.

In of test results can be expected to fall below the required these cases, concrete is proportioned using Table 5. The consequences of a available, all available strength tests should be analyzed to localized zone of low-strength concrete in a structure depend obtain the most reliable estimate of the standard deviation on many factors, including: for the concrete being used on that project. Table 5. Standard deviation table, with examples using the equations, is presented in 5.

This is seen in Fig. This value should overdesign increases as the variation, expressed as the not be confused with the number of strength test results used coefficient of variation, rises. These equations all require a reliability factor value z, Table 5. Examples are shown in normal distribution of strength test results, the z value can be Section 5.

The whether the coefficient of variation or standard deviation examples that follow show how different criteria may be equation is used. Numerical examples are presented in both Table 5.

From Table 5. Using Eq. ACI contains variations of these equations. According to Table 5. An alternative Criterion No. These two criteria are equivalent at psi the individual strength test results fall below 0. ACI requires that concrete Because both criteria psi 3. For example, assume deviation of psi 3. The required average strength for this than 2. Individual strength criterion 5. Moving average of three strength tests criterion 5.

Evaluation for mixture submittal purposes; 5. Evaluation of level of control; and 35 MPa —Assume sufficient data exist for which a coefficient 3. Evaluation to determine compliance with specifications. In all cases, standard deviations below the mean.

Applications for routine quality control and compliance overlap considerably. The maximum probability that at least one event 5 7. When evaluating concrete tests, p is the single event For routine building construction, ACI requires at probability of noncompliance with the strength criteria in least one test per day.

There should be one test for every yd3 ACI Without more details, assume the probability of a 50 yd3 40 m3. Testing frequency should satisfy each criterion.

Table 6. Testing more frequently than this occurrence of a noncompliant result given various numbers can slow the construction process. One test The probability for noncompliance is not trivial, even for for every 50 yd3 40 m3 would be appropriate only for the relatively small projects. For example, there is approximately a most critical applications. There is a high probability of such an occurrence will be represented by at least one test.

At least five tests on most projects, and it is a near certainty on large projects, should be conducted for each class of concrete on a given even if variation is due exclusively to random effects and project. Probabilities are reduced somewhat for larger projects due to the effects of interference; however, the 6. Arbitrarily rejecting strength test results that appear too far out of line is not recommended because normal distribution 6.

Discarding test For a particular project, a sufficient number of tests should results indiscriminately can seriously distort the strength be made to ensure accurate representation of the concrete. Occasionally, ACI defines a strength test as the average strength of two the strength of one cylinder from a group made from a or more specimens of the same age fabricated from a sample sample deviates so far from the others that it is considered taken from a single batch of concrete.

Testing frequency can highly improbable. If questionable variations are observed be established on the basis of time elapsed or volume placed. ASTM E provides criteria for rejecting the test result A project where one engineer supervises all concrete for one specimen in a set of specimens. Generally, the result operations provides an excellent opportunity for control and from a single specimen in a set of three or more specimens accurate estimates of the mean and standard deviation with can be discarded if its deviation from a test mean is greater minimum testing.

Once operations are progressing than three times the previously established within-batch smoothly, tests taken each day or shift, depending on the standard deviation Chapter 4.

The result should be investigated volume of concrete produced, can be sufficient to obtain data if its deviation is greater than two times the within-batch that reflect the variations of the concrete as delivered. The standard deviation. The test average should be computed engineer can reduce the number of tests required by the from the remaining specimens. A test, that is, the average project specifications as the levels of control of the producer, of all specimens of a single sample tested at the same age, laboratory, and contractor are established.

To avoid bias, all should not be rejected unless it is likely that the specimens sampling for acceptance testing should be conducted using are faulty. The test represents the best available estimate for randomly selected batches of concrete. Well-established Normally, potential compressive strength and variability methods for setting up charts similar to those about to be of concrete are based on test results using cylinders that have presented are outlined in ASTM MNL 7A.

Test cylinder diameter should be at least Data falling outside established limits indicate something three times the size of the nominal maximum aggregate in has affected the control of the process, and action or interference the mixture.

Concrete specimens made or cured under with the existing process variables to bring it back under nonstandard conditions may provide additional information, control is often required.

These actions or process interference but should be analyzed and reported separately. Specimens limit values are generally established using methods like that have not been produced, cured, or tested under standard those used by this guide, based on contract specifications or conditions may not accurately reflect potential concrete other values at which action should be taken. Frequently, strength. Discrepancies and deviations from standard testing action or interference limits are equal to the acceptance conditions should be noted on strength test reports.

Concrete strength testing at later ages, such as 56, 91, or Figure 6. These charts are combined particularly where a pozzolan, low heat cement, or cement of into one diagram so they can be evaluated simultaneously.

Some structural elements or These charts may not contain all the features of formal structures will not be loaded until concrete has matured longer control charts, but they can be useful to the concrete engineer, than 28 days and advantage can be taken of this strength gain.

Control charts of this type If a design is based on later-age strengths, it may be necessary are strongly recommended for concrete in continuous to correlate with day strength because it is not always production over considerable periods.

Concrete batching plants succession based on casting date, shows the variation between could preestablish this correlation for later reference, even if a pair of cylinders made from the same concrete sample.

The later-age concrete may not be immediately involved it required average strength in Fig. The chart often also includes the specified Many times in the early stages of a job, it is necessary to strength. This chart is useful because it shows all the available estimate the strength of concrete being produced before day data, but it is limited at identifying trends and shifts in data. Reinforcing bars projecting into the element must be identi- See Fig. To meet ACI M , the re- not less than one-third of the total column strip top reinforce- inforcing bars that are to be epoxy-coated shall conform to ment at the support.

A minimum of one-half of all bottom re- the requirements of ACI 3. Suitable coatings steel 2. Bar supports should be made of dielectric material or wire bar supports should be coated with 2.

Structural drawings for structures or elements of concrete, for a minimum distance of 2 in. Re- all of the essential information noted previously for uncoated inforcing bars used as support bars should be epoxy-coated. S1 and S2 concrete. S2 should be specified when fab- rication after galvanization includes only bending. Class 1 3. The plan nor- should be permitted in close proximity to galvanized reinforc- mally is drawn in the upper left corner of the sheet, with the ing bars except as part of a cathodic protection system.

Bars that require special finished bend diam- upper right corner of the drawing. A figure in the supporting eters usually smaller bar sizes for stirrups and ties should reference data section presents a recommended layout.

Maintenance of identification to the point of An arrow indicating the direction of North should be shipment during the galvanizing process is the responsibility placed beside every plan view. Regular tags plus metal tags should be at- 3. The regular tag is often con- breviations for placing drawings are shown in the supporting sumed in the galvanizing process, leaving the metal tag for reference data section.

Zinc-coated galvanized bars are Where unusual details or conditions require use of other identified with a suffix G and a note stating that all bars special symbols or abbreviations, the drawings must pro- marked as such are to be zinc-coated galvanized. Gal- commonly referred to as a schedule.

A schedule is a compact vanized bars must not be coupled to uncoated bars. Zinc- summary of all the bars complete with the number of pieces, coated tie wire or nonmetallic coated tie wire should be used. Although these schedules usually include the made of dielectric material. Epoxy-coated reinforcing bars necessary for the placement and fabrication of the material. The designa- schedules, material lists, and bending details.

They can be tion G is appropriate for galvanized reinforcing bars. The contract documents steel. The same designations should be used ings. Bending details can be shown on a separate drawing in- The described marking systems identify individual, rein- stead of on the placing drawings.

Reinforcing bars 3. Only drawings, the fabricator takes the following steps: bent bars are given a mark to assist the placer in selecting the 1. Prepares placing drawings including bending details ; proper bars for each member. The straight bar size and length 2. Submits placing drawings, if required by the project is its own identification. Prepares bar lists bills of materials ; evation, or section, or can be listed in a schedule.

It is 4. Fabricates reinforcing steel; acceptable practice to detail footings, columns, beams, and 5. Provides coated bars if specified; slabs in schedules. There is no standard format for schedules. Provides bar supports per customer requirements; and They take the place of a drawing, such as a beam elevation, 7.

Tags, bundles, and delivers the fabricated reinforcing and must clearly indicate to the placer exactly where and bars to the job site. It should be noted that the general term fabricator, as used 3. In this regard, it is actually instructions on the contract documents. They also serve as ble building code for information to use in preparing placing the basis for preparing bar lists. Bending details reinforcing steel is detailed, fabricated, and delivered by may be separate or incorporated in the schedule.

The detailer units, which generally consist of building components, such must show number, mark, and size of members; number, size, as footings, walls, columns, each floor, and roof.

A separate and length of straight bars; number, size, mark, and length of placing drawing and bar list are usually made for each com- bent bars and stirrups; spacing of stirrups; offsets of bars; lap ponent. For small structures, all reinforcing steel can be han- splices; bar supports; and any other special information nec- dled as one unit. For large projects, the contractor may desire essary for the proper fabrication and placement of the rein- a unit, such as a single floor, to be divided to correspond with forcing steel.

Overall length of bar; before the detailing is begun. All sections should be kept as 2. Height of hook where such dimensions are controlling; large as practical because it is more economical to detail and 3. Lap splice lengths; fabricate for large units, especially where there is apt to be a 4.

Offset dimensions, if any; and duplication of bars. Location of bar with respect to supporting members 3. Where possible, the same designa- 3. When members alike on the structural The schedule and bending details for slabs are similar to drawings are slightly different on the placing drawings, a those for beams.

If some of the beams marked 2B3 on the structural and reinforcing steel is shown for only one panel of each drawing actually differ from the others, the placing drawing kind. In skewed panels, such as for the quadrant of a circle, would show some of the beams as 2B3 and the others as the bars are fanned out so that they are placed at the required 2B3A. In reinforced-concrete joist floors, there can be so spacing at a specific location, usually at the midspan.

Addi- many variations from the basic joists shown on the structural tional bars around openings, if required, must be shown. Standardized marks are sometimes pretation to the placer. The detailer must show the quantity, used for bars occurring in the same relative position in cul- size, and length or mark of all bars, including dowels, prin- verts. The detailer must also include Any system of letters and numerals is acceptable.

The detailer must clearly show length and by the mark, where the bar is placed in the structure. Schedules are sometimes used for piers, small with the reinforcing steel in the element that is placed first. Highway structural They must be ordered with the element to be available for drawings usually include, when detailed completely, a type placement at the proper time.

These drawings are used by ports specified in the contract documents, including quanti- the fabricator to prepare shop bar lists. These layouts can be shown shown clearly. The contractor should not have to compute on the placing drawing or given by reference to the CRSI Man- any needed dimensions. Drawings must show the dimen- ual of Standard Practice. Support bars, when required, must be sions of concrete protection for all reinforcing steel. For ex- shown clearly and identified on the placing drawings.

Where Unlike the customary practice in the field of reinforced- separate placing drawings are prepared, structural dimen- concrete buildings, many state highway departments prepare sions may be omitted following the same practice as for a combination structural and placing drawing.

The combina- buildings. The placer uses size, spacing, splices, and location of the coated and uncoat- the combination drawing to place the reinforcing bars. High- ed bars in the structure. The bar schedule combined draw- way departments that do not use combination drawings fol- ing must show the number of pieces, size, length, mark of low the procedures of Section 3. This station identification or bridge number abutments, piers, and girders.

The bar list is then similarly must be shown on all bundle tags and shipping papers to fa- subdivided. If the structure is sufficiently large, a separate cilitate proper distribution of reinforcing bars on delivery.

For small, simple structures such as culverts, slab bridges, Reinforcing bars for foundations, piers, abutments, wing manholes, and catch basins, a station number in addition to walls, and slabs are usually shown on plan, section, or eleva- the title description of the structure is sufficient identifica- tion views.

Reinforcing steel can be shown in the simplest tion without dividing the structure into smaller units by fur- and clearest manner, however, the bar list must be a com- ther marking. Larger structures, such as reinforced-concrete deck gird- To be certain that all of the reinforcing steel is properly ers, I-beam bridges, continuous-type bridges, and arches, placed or positioned in a unit, a cross section is frequently re- consist of small units that together make up a complete struc- quired in addition to the plan and elevation of the unit where ture.

These units are referred to as end bents, intermediate the bars are shown. The used widely as a means of securely holding reinforcing steel construction units of unusually long culverts with more than in proper position while the concrete is being placed. Plastic one design of barrel, for varying load conditions or, where coated or stainless legs can be specified to avoid possible construction joints are required across the barrel, can be iden- rusting at points of exposure.

Precast concrete blocks are tified by section numbers. Schedules of reinforcing bars are used in some states, particularly in the western United States.

Support bars, when furnished, should be shown in lots as required. For highway structures, both straight and bent bars are given Where an exposed concrete surface is to receive special an individual mark. The standard hooks Table 1 were devel- the finished surface appearance. The detailer should identify the specified types and was recognized as well. In the Table, the extra length of bar show locations where each is to be used. It is standard practice in the industry to show all bar di- Where the physical conditions of the job are such that ei- mensions as out-to-out and consider the bar lengths as the ther J, A, G, or H of the hook is a controlling dimension, it sum of all detailed dimensions, including Hooks A and G must be so noted on the drawings, schedules, and bar lists.

Controls are anchorage. The most common is to use one of the hooks established by specifying the minimum inside radius or in- shown in Table 1. Types Sl to S6 in Fig. In detailing the anchorage, multiple of the nominal diameter of the bar db. The ratio of diameter of bend to diameter of bar is not a constant because care must be taken that the ends of stirrup hooks that are it has been found by experience that this ratio must be larger turned outward into shallow slabs have adequate cover.

If as the bar size increases. A 6db 6db 19, 22, 25 chart of such standard bar bends is shown in Fig. For straight portions of the bar, the distance is measured to the theoretical intersection of the outside edge line extended to the outside edge line of the adjacent straight portion, or to The inside diameter of bends of welded-wire fabric plain the point of tangency to a curve, from which point the length or deformed for stirrups and ties, as specified by ACI M , shall not be less than 4db for deformed wire larger of the latter is tabulated, as in Types 10 and 11 in Fig.

Bends with in- Truss bar dimensioning is special and is shown in large-scale side diameter of less than 8db shall not be less than 4db from detail in Fig. It also defines cial requirement is established in the contract documents, standard hook Section 7. Any applicable addenda or errata are included with individual documents at the time of purchase.

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The Code covers the design and construction of masonry structures while the Specification is concerned with minimum construction requirements for masonry in structures. The Commentaries are mandatory and are for information of the user only. This Specification is meant to be modified and referenced in the Project Manual.

These items are not eligible for return. The edition can be purchased through the Aci Store, as well as other historical editions. Some of the aci covered in the Code are: The commentaries present background details, committee considerations, and research data used to develop the Aci and Specification.