R62 Removal of forms shores and reshoring

In determining the time for removal of forms, consideration should be given to the construction loads and to the possibilities of deflections.6.3 The construction loads are frequently at least as great as the specified live loads. At early ages, a structure may be adequate to support the applied loads but may deflect sufficiently to cause permanent damage. Evaluation of concrete strength during construction may be demonstrated by field-cured test cylinders or other procedures approved by the...

R109 Limits for reinforcement of compression members

10.9.1 Area of longitudinal reinforcement, Ast, for noncomposite compression members shall be not less than 0.01 Ag or more than 0.08Ag. R10.9.1 This section prescribes the limits on the amount of longitudinal reinforcement for noncomposite compression members. If the use of high reinforcement ratios would involve practical difficulties in the placing of concrete, a lower percentage and hence a larger column, or higher strength concrete or reinforcement (see R9.4) should be considered. The...

D62 Concrete breakout strength of anchor in shear

RD.6.2 Concrete breakout strength of anchor in shear D.6.2.1 The nominal concrete breakout strength, Vcb or Vcbg, in shear of a single anchor or group of anchors shall not exceed (a) for shear force perpendicular to the edge on a single anchor RD.6.2.1 The shear strength equations were developed from the CCD method. They assume a breakout cone angle of approximately 35 degrees (See Fig. RD.4.2.2(b)), and consider fracture mechanics theory. The effects of multiple anchors, spacing of anchors,...

1010 Slenderness effects in compression members

10.10.1 Except as allowed in 10.10.2, the design of compression members, restraining beams, and other supporting members shall be based on the factored forces and moments from a second-order analysis considering material nonlinearity and cracking, as well as the effects of member curvature and lateral drift, duration of the loads, shrinkage and creep, and interaction with the supporting foundation. The dimensions of each member cross section used in the analysis shall be within 10 percent of...

Special reinforced concrete structural wall A

Cast-in-place wall complying with the requirements of 21.2.2.3, 21.2.3 through 21.2.7, and 21. 7 in addition to the requirements for ordinary reinforced concrete structural walls. The provisions of 21.8 are intended to result in a special precast structural wall having minimum strength and toughness equivalent to that for a special reinforced concrete structural wall of cast-in-place concrete. Strut An element of a structural diaphragm used to provide continuity around an opening in the...

R811 Joist construction

The size and spacing limitations for concrete joist construction meeting the limitations of 8.11.1 through 8.11.3 are based on successful performance in the past. 8.11.2 Ribs shall be not less than 4 in. in width, and shall have a depth of not more than 3-1 2 times the minimum width of rib. 8.11.3 Clear spacing between ribs shall not exceed 30 in. 8.11.4 Joist construction not meeting the limitations of 8.11.1 through 8.11.3 shall be designed as slabs and beams. 8.11.5 When permanent burned...

Regular polygon shaped columns or pedestals

For location of critical sections for moment, shear, and development of reinforcement in footings, it shall be permitted to treat circular or regular polygon shaped concrete columns or pedestals as square members with the same area. 15.4 Moment in footings R15.4 Moment in footings 15.4.1 External moment on any section of a footing shall be determined by passing a vertical plane through the footing, and computing the moment of the forces acting over entire area of footing on one side of that...

Code

(c) 24 times the diameter of the hoop bar 21.12.4.3 Stirrups shall be placed at not more than d 2 throughout the length of the member. 21.12.5.1 Columns shall be spirally reinforced in accordance with 7.10.4 or shall conform with 21.12.5.2 through 21.12.5.4. Section 21.12.5.5 shall apply to all columns. 21.12.5.2 At both ends of the member, hoops shall be provided at spacing so over a length 1o measured from the joint face. Spacing so shall not exceed the smallest of (a), (b), (c), and (d) (a)...

812 Separate floor finish

8.12.1 A floor finish shall not be included as part of a structural member unless placed monolithically with the floor slab or designed in accordance with requirements of Chapter 17. 8.12.2 It shall be permitted to consider all concrete floor finishes as part of required cover or total thickness for nonstructural considerations. R8.11.8 The increase in shear strength permitted by 8.11.8 is justified on the basis of (1) satisfactory performance of joist construction with higher shear strengths,...

R711 Lateral reinforcement for flexural members

7.11.1 Compression reinforcement in beams shall be enclosed by ties or stirrups satisfying the size and spacing limitations in 7.10.5 or by welded wire reinforcement of equivalent area. Such ties or stirrups shall be provided throughout the distance where compression reinforcement is required. 7.11.2 Lateral reinforcement for flexural framing members subject to stress reversals or to torsion at supports shall consist of closed ties, closed stirrups, or spirals extending around the flexural...

Commentary

R13.7.3.3 A support is defined as a column, capital, bracket, or wall. A beam is not considered to be a support member for the equivalent frame. 13.7.4.1 Determination of the moment of inertia of columns at any cross section outside of joints or column capitals using the gross area of concrete shall be permitted. 13.7.4.2 Variation in moment of inertia along axis of columns shall be taken into account. 13.7.4.3 Moment of inertia of columns from top to bottom of the slab-beam at a joint shall be...

U 14d 17l 17hc4

In Eq. (C-4), where Dor L reduce the effect of H, 0.9D shall be substituted for 1.4D, and zero value of L shall be used to determine the greatest required strength U. C.2.4 For structures that resist F, load due to weight and pressure of fluids with well-defined densities, the load factor for F shall be1.4, and F shall be added to all loading combinations that include L. RC.1.1 In the 2002 code, the load and strength reduction factors formerly in Chapter 9 were revised and moved to this...

R89 Arrangement of live load

For determining column, wall, and beam moments and shears caused by gravity loads, the code permits the use of a model limited to the beams in the level considered and the columns above and below that level. Far ends of columns are to be considered as fixed for the purpose of analysis under gravity loads. This assumption does not apply to lateral load analysis. However in analysis for lateral loads, simplified methods (such as the portal method) may be used to obtain the moments, shears, and...

A5 Strength of nodal zonesRA5 Strength of nodal zones

A.5.1 The nominal compression strength of a RA.5.1 If the stresses in all the struts meeting at a node nodal zone, Fnn, shall be are equal, a hydrostatic nodal zone can be used. The faces of such a nodal zone are perpendicular to the axes of the struts, Fnn fceAnz (A-7) and the widths of the faces of the nodal zone are propor where fce is the effective compressive strength of the concrete in the nodal zone as given in A.5.2 and Anz is

B18104 Redistribution of negative moments in continuous prestressed flexural members

B.18.10.4.1 Where bonded reinforcement is provided at supports in accordance with 18.9, negative moments calculated by elastic theory for any assumed in the deflection under load. Tests have shown that it is not possible to rupture (or even yield) unbonded post-tensioning tendons in two-way slabs before a punching shear fail-ure.B.3-B.8 The use of unbonded tendons in combination with the minimum bonded reinforcement requirements of 18.9.3 and 18.9.4 has been shown to ensure post-cracking...

1067

Where computed tensile stresses, ft, exceed the limits in (b) or (c), additional bonded reinforcement (nonpre-stressed or prestressed) shall be provided in the tensile zone to resist the total tensile force in concrete computed with the assumption of an uncracked section. 18.4.2 For Class U and Class T prestressed flexural members, stresses in concrete at service loads (based on uncracked section properties, and after allowance for all prestress losses) shall not exceed the following (a)...

ACI 318 Building Code and Commentary

3.6.2 An admixture shall be shown capable of maintaining essentially the same composition and performance throughout the work as the product used in establishing concrete proportions in accordance with 5.2. 3.6.3 Calcium chloride or admixtures containing chloride from other than impurities from admixture ingredients shall not be used in prestressed concrete, in concrete containing embedded aluminum, or in concrete cast against stay-in-place galvanized steel forms. See 4.3.2 and 4.4.1. R3.6.3...

R115 Shear strength provided by shear reinforcement

11.5.2 The values of fy and fyt used in design of shear reinforcement shall not exceed 60,000 psi, except the value shall not exceed 80,000 psi for welded deformed wire reinforcement. R11.5.2 Limiting the values of fy and fyt used in design of shear reinforcement to 60,000 psi provides a control on diagonal crack width. In the 1995 code, the limitation of 60,000 psi for shear reinforcement was raised to 80,000 psi for welded deformed wire reinforcement. Research has indi cated that the...

81 Design methods

8.1.1 In design of structural concrete, members shall be proportioned for adequate strength in accordance with provisions of this code, using load factors and strength reduction factors specified in Chapter 9. 8.1.2 Design of reinforced concrete using the provisions of Appendix B, Alternative Provisions for Reinforced and Prestressed Concrete Flexural and Compression Members, shall be permitted. 8.1.3 Anchors within the scope of Appendix D, Anchoring to Concrete, installed in concrete to...

532 Required average strength

5.3.2.1 Required average compressive strength fc'r used as the basis for selection of concrete proportions shall be determined from Table 5.3.2.1 using the sample standard deviation, ss, calculated in accordance with 5.3.1.1 or 5.3.1.2. TABLE 5.3.2.1 REQUIRED AVERAGE COMPRESSIVE STRENGTH WHEN DATA ARE AVAILABLE TO ESTABLISH A SAMPLE STANDARD DEVIATION TABLE 5.3.2.1 REQUIRED AVERAGE COMPRESSIVE STRENGTH WHEN DATA ARE AVAILABLE TO ESTABLISH A SAMPLE STANDARD DEVIATION Required average compressive...

Codecommentary

10.6.2 Distribution of flexural reinforcement in two-way slabs shall be as required by 13.3. 10.6.3 Flexural tension reinforcement shall be well distributed within maximum flexural tension zones of a member cross section as required by 10.6.4. 10.6.4 The spacing of reinforcement closest to the tension face, s, shall not exceed that given by but not greater than 12(40,000 fs), where cc is the least distance from surface or reinforcement or pre-stressing steel to the tension face. If there is...

R44 Corrosion protection of reinforcement

R4.4.1 Additional information on the effects of chlorides on the corrosion of reinforcing steel is given in Guide to Durable Concrete reported by ACI Committee 2014.10 and Corrosion of Metals in Concrete reported by ACI Committee 222.4.11 Test procedures should conform to those given in ASTM C 1218. An initial evaluation may be obtained by testing individual concrete ingredients for total chloride ion content. If total chloride ion content, calculated on the basis of concrete proportions,...

771 Castinplace concrete nonprestressed

The following minimum concrete cover shall be provided for reinforcement, but shall not be less than required by 7.7.5 and 7.7.7 permanently exposed to (b) Concrete exposed to earth or weather No. 6 through No. 18 bars 2 and (c) Concrete not exposed to weather or in contact with ground No. 14 and No. 18 bars 1-1 2 No. 11 bar and smaller 3 4 preclude bundling more than two bars in the same plane. Typical bundle shapes are triangular, square, or L-shaped patterns for three- or four-bar bundles....

R510 Depositing

Rehandling concrete can cause segregation of the materials. Hence the code cautions against this practice. Retempering of partially set concrete with the addition of water should not be permitted, unless authorized. This does not preclude the practice (recognized in ASTM C 94) of adding water to mixed concrete to bring it up to the specified slump range so long as prescribed limits on the maximum mixing time and water-cementitious materials ratio are not violated. Section 5.10.4 of the 1971...

R83 Methods of analysis

R8.3.1 Factored loads are service loads multiplied by appropriate load factors. For the strength design method, elastic analysis is used to obtain moments, shears, and reactions. R8.3.3 The approximate moments and shears give reasonably conservative values for the stated conditions if the flexural members are part of a frame or continuous construction. Because the load patterns that produce critical values for moments in columns of frames differ from those for maximum negative moments in beams,...

N

But not less than zero, where Nu is negative for tension. Nu Ag shall be expressed in psi. (11-6) will exceed the upper limit given by Eq. (11-7) before the value of Mm given by Eq. (11-6) becomes negative. The value of Vc obtained from Eq. (11-5) has no physical significance if a negative value of Mm is substituted. For this condition, Eq. (11-7) or Eq. (11-4) should be used to calculate Vc. Values of Vc for members subject to shear and axial load are illustrated in Fig. R11.3.2.2. The...

TABLE 95b Maximum Permissible Computed Deflections

Flat roofs not supporting or attached to nonstructural elements likely to be damaged by large deflections Immediate deflection due to live load L Floors not supporting or attached to nonstruc-tural elements likely to be damaged by large deflections Immediate deflection due to live load L Roof or floor construction supporting or attached to nonstructural elements likely to be damaged by large deflections That part of the total deflection occurring after attachment of nonstructural elements (sum...

355 Prestressing steel

Plain bars and plain wire are permitted only for spiral reinforcement (either as lateral reinforcement for compression members, for torsion members, or for confining reinforcement for splices). 3.5.5.1 Steel for prestressing shall conform to one of the following specifications (a) Wire conforming to Specification for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete (ASTM A 421) R3.5.5.1 Because low-relaxation prestressing steel is addressed in a supplement to ASTM A 421, which...

R64 Construction joints

For the integrity of the structure, it is important that all construction joints be defined in construction documents and constructed as required. Any deviations should be approved by the engineer or architect. 6.4.2 Immediately before new concrete is placed, all construction joints shall be wetted and standing water removed. R6.4.2 The requirements of the 1977 code for the use of neat cement on vertical joints have been removed, since it is rarely practical and can be detrimental where deep...

R812 Separate floor finish

The code does not specify an additional thickness for wearing surfaces subjected to unusual conditions of wear. The need for added thickness for unusual wear is left to the discretion of the designer. As in previous editions of the code, a floor finish may be considered for strength purposes only if it is cast monolithi-cally with the slab. Permission is given to include a separate finish in the structural thickness if composite action is provided for in accordance with Chapter 17. All floor...

2196 Design forces

The seismic design forces for structural diaphragms shall be obtained from the lateral load analysis in accordance with the design load combinations. ment is intended to control the width of inclined cracks. Minimum average prestress requirements (7.12.3) are considered to be adequate to limit the crack widths in post-ten-sioned floor systems therefore, the maximum spacing requirements do not apply to these systems. The minimum spacing requirement for welded wire reinforcement in topping slabs...

R77 Concrete protection for reinforcement

Concrete cover as protection of reinforcement against weather and other effects is measured from the concrete surface to the outermost surface of the steel to which the cover requirement applies. Where minimum cover is prescribed for a class of structural member, it is measured to the outer edge of stirrups, ties, or spirals if transverse reinforcement encloses main bars to the outermost layer of bars if more than one layer is used without stirrups or ties or to the metal end fitting or duct on...

Commentary R61 Design of formwork

Only minimum performance requirements for formwork, necessary to provide for public health and safety, are prescribed in Chapter 6. Formwork for concrete, including proper design, construction, and removal, demands sound judgment and planning to achieve adequate forms that are both economical and safe. Detailed information on form-work for concrete is given in Guide to Formwork for Concrete, reported by Committee 347.6.1 (Provides recommendations for design, construction, and materials for...

188 Limits for reinforcement of flexural members

18.8.1 Prestressed concrete sections shall be classified as either tension-controlled, transition, or compression-controlled sections, in accordance with 10.3.3 and 10.3.4. The appropriate strength reduction factors, from 9.3.2 shall apply. 18.8.2 Total amount of prestressed and nonpre-stressed reinforcement shall be adequate to develop a factored load at least 1.2 times the cracking load computed on the basis of the modulus of rupture fr specified in 9.5.2.3. This provision shall be permitted...

2199 Construction joints

All construction joints in diaphragms shall conform to 6.4 and contact surfaces shall be roughened as in 11.7.9. R21.9.8 Boundary elements of structural diaphragms For structural diaphragms, the design moments are assumed to be resisted entirely by chord forces acting at opposite edges of the diaphragm. Reinforcement located at the edges of collectors should be fully developed for its specified yield strength. Adequate confinement of lap splices is also required. If chord reinforcement is...

R56 Evaluation and acceptance of concrete

Once the mixture proportions have been selected and the job started, the criteria for evaluation and acceptance of the concrete can be obtained from 5.6. 5.6.1 Concrete shall be tested in accordance with the requirements of 5.6.2 through 5.6.5. Qualified field testing technicians shall perform tests on fresh concrete at the job site, prepare specimens required for curing under field conditions, prepare specimens required for testing in the laboratory, and record the temperature of the fresh...

R72 Minimum bend diameters

Standard bends in reinforcing bars are described in terms of the inside diameter of bend since this is easier to measure than the radius of bend. The primary factors affecting the minimum bend diameter are feasibility of bending without breakage and avoidance of crushing the concrete inside the bend. 7.2.2 Inside diameter of bend for stirrups and ties shall not be less than 4db for No. 5 bar and smaller. For bars larger than No. 5, diameter of bend shall be in accordance with Table 7.2. 7.2.3...

5113 Accelerated curing

5.11.3.1 Curing by high-pressure steam, steam at atmospheric pressure, heat and moisture, or other accepted processes, shall be permitted to accelerate strength gain and reduce time of curing. 5.11.3.2 Accelerated curing shall provide a com-pressive strength of the concrete at the load stage considered at least equal to required design strength at that load stage. 5.11.3.3 Curing process shall be such as to produce concrete with a durability at least equivalent to the curing method of 5.11.1 or...

R14 Approval of special systems of design or construction

Sponsors of any system of design or construction within the scope of this code, the adequacy of which has been shown by successful use or by analysis or test, but which does not conform to or is not covered by this code, shall have the right to present the data on which their design is based to the building official or to a board of examiners appointed by the building official. This board shall be composed of competent engineers and shall have authority to investigate the data so submitted, to...

1

Stiffness reduction factor 4k in Eq. (10-9) and (10-18), and the cross-sectional strength reduction 4-factors. In defining the critical load, the main problem is the choice of a stiffness EI that reasonably approximates the variations in stiffness due to cracking, creep, and the nonlinearity of the concrete stress-strain curve. Eq. (10-11) was derived for small eccentricity ratios and high levels of axial load where the slenderness effects are most pronounced. Creep due to sustained load will...

R183 Design assumptions

18.3.2.1 Strains vary linearly with depth through the entire load range. 18.3.2.2 At cracked sections, concrete resists no tension. 18.3.3 Prestressed flexural members shall be classified as Class U, Class T, or Class C based on ft, the computed extreme fiber stress in tension in the pre-compressed tensile zone calculated at service loads, as follows (b) Class T 7.5 f < ft < 12 f Prestressed two-way slab systems shall be designed as Class U with ft < 6 f'. R18.3.3 This section defines...

R112 Lightweight concrete

Two alternative procedures are provided to modify the provisions for shear and torsion when lightweight aggregate concrete is used. The lightweight concrete modification applies only to the terms containing Jf' in the equations of Chapter 11. R11.2.1.1 The first alternative bases the modification on laboratory tests to determine the relationship between average splitting tensile strength fct and the specified compressive strength fc' for the lightweight concrete being used. For normalweight...

163 Distribution of forces among members

16.3.1 Distribution of forces that are perpendicular to the plane of members shall be established by analysis or by test. 16.3.2 Where the system behavior requires inplane forces to be transferred between the members of a precast floor or wall system, 16.3.2.1 and 16.3.2.2 shall apply. 16.3.2.1 In-plane force paths shall be continuous through both connections and members. 16.3.2.2 Where tension forces occur, a continuous path of steel or steel reinforcement shall be provided.

176 Ties for horizontal shear

17.6.1 Where ties are provided to transfer horizontal shear, tie area shall not be less than that required by 11.5.6.3, and tie spacing shall not exceed four times the least dimension of supported element, nor exceed 24 in. The minimum areas and maximum spacings are based on test data given in References 17.2 through 17.6. 17.6.2 Ties for horizontal shear shall consist of single bars or wire, multiple leg stirrups, or vertical legs of welded wire reinforcement. 17.6.3 All ties shall be fully...

57 Preparation of equipment and place of deposit

5.7.1 Preparation before concrete placement shall include the following (a) All equipment for mixing and transporting concrete shall be clean (b) All debris and ice shall be removed from spaces to be occupied by concrete (c) Forms shall be properly coated (d) Masonry filler units that will be in contact with concrete shall be well drenched (e) Reinforcement shall be thoroughly clean of ice or other deleterious coatings quacy for virtually any type of construction.5.5-5.8 Lower strength may, of...

35

* See ASTM C 33 for tolerance on oversize for various nominal maximum size designations. + These air contents apply to total mix, as for the preceding aggregate sizes. When testing these concretes, however, aggregate larger than 1-1 2 in. is removed by handpicking or sieving and air content is determined on the minus 1-1 2 in. fraction of mix (tolerance on air content as delivered applies to this value.). Air content of total mix is computed from value determined on the minus 1-1 2 in....

12 15 19

Strand is capable of adequate bond. . The precast concrete manufacturer may rely on certification from the strand manufacturer that the strand has bond characteristics that comply with this section. Strand with a slightly rusted surface can have an appreciably shorter transfer length than clean strand. Gentle release of the strand will permit a shorter transfer length than abruptly cutting the strands. The provisions of 12.9 do not apply to plain wires or to end-anchored tendons. The length for...

2111 Members not designated as part of the lateralforceresisting system

21.11.1 Frame members assumed not to contribute to lateral resistance, except two-way slabs without beams, shall be detailed according to 21.11.2 or 21.11.3 depending on the magnitude of moments induced in those members when subjected to the design displacement Su. If effects of Su are not explicitly checked, it shall be permitted to apply the requirements of 21.11.3. For two-way slabs without beams, slab-column connections shall meet the requirements of 21.11.5. 21.11.2 Where the induced...

1817 Posttensioning ducts

R18.16 Corrosion protection for unbonded tendons R18.16.1 Suitable material for corrosion protection of unbonded prestressting steel should have the properties identified in Section 5.1 of Reference 18.26. R18.16.2 Typically, sheathing is a continuous, seamless, high-density polythylene material that is extruded directly onto the coated prestressing steel. R18.16.4 In the 1989 code, corrosion protection requirements for unbonded single strand tendons were added in accordance with the...

145 Empirical design method

14.5.1 Walls of solid rectangular cross section shall be permitted to be designed by the empirical provisions of 14.5 if the resultant of all factored loads is located within the middle third of the overall thickness of the wall and all limits of 14.2, 14.3, and 14.5 are satisfied. 14.5.2 Design axial strength 0Pn of a wall satisfying limitations of 14.5.1 shall be computed by Eq. (14-1) unless designed in accordance with 14.4. where shall correspond to compression-controlled sections in...

1016 Composite compression members

COMMENTARY R10.16 Composite compression members 10.16.1 Composite compression members shall include all such members reinforced longitudinally with structural steel shapes, pipe, or tubing with or without longitudinal bars. R10.16.1 Composite columns are defined without reference to classifications of combination, composite, or concrete-filled pipe column. Reference to other metals used for reinforcement has been omitted because they are seldom used in concrete construction. 10.16.2 Strength of...

135 Design procedures

13.5.1 A slab system shall be designed by any procedure satisfying conditions of equilibrium and geometric compatibility, if shown that the design strength at every section is at least equal to the required strength set forth in 9.2 and 9.3, and that all serviceability conditions, including limits on deflections, are met. 13.5.1.1 Design of a slab system for gravity loads, including the slab and beams (if any) between supports and supporting columns or walls forming orthogonal frames, by either...

R712 Shrinkage and temperature reinforcement

R7.12.1 Shrinkage and temperature reinforcement is required at right angles to the principal reinforcement to minimize cracking and to tie the structure together to ensure its acting as assumed in the design. The provisions of this section are intended for structural slabs only they are not intended for soil-supported slabs on grade. R7.12.1.2 The area of shrinkage and temperature reinforcement required by 7.12 has been satisfactory where shrinkage and temperature movements are permitted to...

A1 Definitions

B-region A portion of a member in which the plane sections assumption of flexure theory from 10.2.2 can be applied. Discontinuity An abrupt change in geometry or loading. D-region The portion of a member within a distance, h, from a force discontinuity or a geometric discontinuity. Deep beam See 10.7.1 and 11.8.1. B-region In general, any portion of a member outside of a D-region is a B-region. Discontinuity A discontinuity in the stress distribution occurs at a change in the geometry of a...

189 Minimum bonded reinforcement

18.9.1 A minimum area of bonded reinforcement shall be provided in all flexural members with unbonded tendons as required by 18.9.2 and 18.9.3. R18.8.3 Some bonded steel is required to be placed near the tension face of prestressed flexural members. The purpose of this bonded steel is to control cracking under full service loads or overloads. R18.9 Minimum bonded reinforcement R18.9.1 Some bonded reinforcement is required by the code in members prestressed with unbonded tendons to ensure...

Reinforcement Standard Hook And Bend

Tie Bar Reinforced Concrete

(d) Where anchorage or development for fy is not specifically required, reinforcement in excess of that required by analysis (As required) (As provided) In 12.5.3(b) and 12.5.3(c), db is the diameter of the hooked bar, and the first tie or stirrup shall enclose the bent portion of the hook, within 2db of the outside of the bend. Fig. R12.5 Hooked bar details for development of standard hooks Fig. R12.5 Hooked bar details for development of standard hooks Fig. R12.5.3(a) Ties or stirrups placed...

1212 Development of negative moment reinforcement

Why The Hook Provided Stirrups

R12.12 Development of negative moment reinforcement 12.12.1 Negative moment reinforcement in a continuous, restrained, or cantilever member, or in any member of a rigid frame, shall be anchored in or through the supporting member by embedment length, hooks, or mechanical anchorage. 12.12.2 Negative moment reinforcement shall have an embedment length into the span as required by 12.1 and 12.10.3. 12.12.3 At least one-third the total tension reinforcement provided for negative moment at a support...

C3 Design strength

C.3.1 Design strength provided by a member, its connections to other members, and its cross sections, in terms of flexure, axial load, shear, and torsion, shall be taken as the nominal strength calculated in accordance with requirements and assumptions of this code, multiplied by the factors in C.3.2, C.3.4, and C.3.5. imum liquid depth, as in ponding of water. See R8.2. For well-defined fluid pressures, the required strength equations become and where D or L reduce the effect of F but for any...

2176 Boundary elements of special reinforced concrete structural walls

Difference Between Tie And Coupling Beam

21.7.6.1 The need for special boundary elements at the edges of structural walls shall be evaluated in accordance with 21.7.6.2 or 21.7.6.3. The requirements of 21.7.6.4 and 21.7.6.5 also shall be satisfied. 21.7.6.2 This section applies to walls or wall piers that are effectively continuous from the base of structure to top of wall and designed to have a single critical section for flexure and axial loads. Walls not Horizontal wall segments in 21.7.4.5 refers to wall sections between two...

RD4 General requirements for strength of anchors

Concrete Pryout

D.4.1 Strength design of anchors shall be based either on computation using design models that satisfy the requirements of D.4.2, or on test evaluation using the 5 percent fractile of test results for the following (a) steel strength of anchor in tension (D.5.1) (b) steel strength of anchor in shear (D.6.1) (c) concrete breakout strength of anchor in tension (D.5.2) (d) concrete breakout strength of anchor in shear (D.6.2) (e) pullout strength of anchor in tension (D.5.3) (f) concrete side-face...

Wall or reinforced pedestal

15.8.1 Forces and moments at base of column, wall, or pedestal shall be transferred to supporting pedestal or footing by bearing on concrete and by reinforcement, dowels, and mechanical connectors. 15.8.1.1 Bearing stress on concrete at contact surface between supported and supporting member shall not exceed concrete bearing strength for either surface as given by 10.17. R15.8 Transfer of force at base of column, wall, or reinforced pedestal Section 15.8 provides the specific requirements for...

R212 General requirements R2121 Scope

Chapter 21 contains provisions considered to be the minimum requirements for a cast-in-place or precast concrete crete members of a structure for which the design forces, related to earthquake motions, have been determined on the basis of energy dissipation in the nonlinear range of response. For applicable specified concrete strengths, see 1.1.1 and 21.2.4.1 21.2.1.2 In regions of low seismic risk or for structures assigned to low seismic performance or design categories, the provisions of...

119 Special provisions for brackets and corbels

Concrete Corbels Uses

R11.9 Special provisions for brackets and corbels 11.9.1 Brackets and corbels with a shear span-to-depth ratio avId less than 2 shall be permitted to be designed using Appendix A. Design shall be permitted using 11.9.3 and 11.9.4 for brackets and corbels with (a) avId not greater than 1, and (b) subject to factored horizontal tensile force, Nuc, not larger than Vu. The requirements of 11.9.2, 11.9.3.2.1, 11.9.3.2.2, 11.9.5, 11.9.6, and 11.9.7 shall apply to design of brackets and corbels....

R194 Shell reinforcement

R19.4.1 At any point in a shell, two different kinds of internal forces may occur simultaneously those associated with membrane action, and those associated with bending of the shell. The membrane forces are assumed to act in the tangential plane midway between the surfaces of the shell, and are the two axial forces and the membrane shears. Flex-ural effects include bending moments, twisting moments, and the associated transverse shears. Limiting membrane crack width and spacing due to...

R165 Structural integrity

16.5.1 Except where the provisions of 16.5.2 govern, the minimum provisions of 16.5.1.1 through 16.5.1.4 for structural integrity shall apply to all precast concrete structures. R16.5.1 The provisions of 7.13.3 apply to all precast concrete structures. Sections 16.5.1 and 16.5.2 give minimum requirements to satisfy 7.13.3. It is not intended that these minimum requirements override other applicable provisions of the code for design of precast concrete structures. The overall integrity of a...

1210 Development of flexural reinforcement General

Bar Cut Off And Anchorage Length

12.10.1 Development of tension reinforcement by bending across the web to be anchored or made continuous with reinforcement on the opposite face of member shall be permitted. 12.10.2 Critical sections for development of reinforcement in flexural members are at points of maximum stress and at points within the span where adjacent reinforcement terminates, or is bent. Provisions of 12.11.3 must be satisfied. 12.10.3 Reinforcement shall extend beyond the point at which it is no longer required to...

R1112 Special provisions for slabs and footings

R11.12.1 Differentiation should be made between a long and narrow slab or footing acting as a beam, and a slab or footing subject to two-way action where failure may occur by punching along a truncated cone or pyramid around a concentrated load or reaction area. Code and Commentary 11.12.1.1 Beam action where each critical section to be investigated extends in a plane across the entire width. For beam action the slab or footing shall be designed in accordance with 11.1 through 11.5. 11.12.1.2...

D52 Concrete breakout strength of anchor in tension

Concrete Breakout Strength

D.5.2.1 The nominal concrete breakout strength, Ncb or Ncbg, of a single anchor or group of anchors in tension shall not exceed Ncbg AT1- Vec, N ed, N c, N cp, NNb (D-5) Nco Factors pec> N, Ped,N, Wc,N, and ycp N are defined in D.5.2.4, D.5.2.5, D.5.2.6, and D.5.2.7, respectively. Anc is the projected concrete failure area of a single anchor or group of anchors that shall be approximated as the base of the rectilinear geometrical figure that results from projecting the failure surface outward...

D1 Definitions

Post Tension Concrete Breakout

Anchor A steel element either cast into concrete or post-installed into a hardened concrete member and used to transmit applied loads, including headed bolts, hooked bolts J- or L-bolt , headed studs, expansion anchors, or undercut anchors. Anchor group A number of anchors of approximately equal effective embedment depth with each anchor spaced at less than three times its embedment depth from one or more adjacent anchors. Anchor pullout strength The strength corresponding to the anchoring...

1214 Splices of reinforcement General

12.14.1 Splices of reinforcement shall be made only as required or permitted on design drawings, or in specifications, or as authorized by the engineer. 12.14.2.1 Lap splices shall not be used for bars larger than No. 11 except as provided in 12.16.2 and 15.8.2.3. 12.14.2.2 Lap splices of bars in a bundle shall be based on the lap splice length required for individual bars within the bundle, increased in accordance with 12.4. Individual bar splices within a bundle shall not overlap. Entire...

R93 Design strength

R9.3.1 The design strength of a member refers to the nominal strength calculated in accordance with the requirements stipulated in this code multiplied by a strength reduction factor which is always less than one. The purposes of the strength reduction factor are 1 to allow for the probability of under-strength members due to variations in material strengths and dimensions, 2 to allow for inaccuracies in the design equations, 3 to reflect the degree of ductility and required reliability of the...

R35 Steel reinforcement

R3.5.1 Fiber reinforced polymer FRP reinforcement is not addressed in this code. ACI Committee 440 has developed guidelines for the use of FRP reinforcement.3.2, 33 Materials permitted for use as reinforcement are specified. Other metal elements, such as inserts, anchor bolts, or plain bars for dowels at isolation or contraction joints, are not normally considered to be reinforcement under the provisions of this code. R3.5.2 When welding of reinforcing bars is required, the weldability of the...

Aci Committee 360.1.9

1.1.2 This code supplements the general building code and shall govern in all matters pertaining to design and construction of structural concrete, except wherever this code is in conflict with requirements in the legally adopted general building code. 1.1.3 This code shall govern in all matters pertaining to design, construction, and material properties wherever this code is in conflict with requirements contained in other standards referenced in this code. 1.1.4 For special structures, such...

Detailed Specficiation Reinforcement Engineering Intro

This commentary discusses some of the considerations of Committee 318 in developing the provisions contained in Building Code Requirements for Structural Concrete ACI 318-05 , hereinafter called the code or the 2005 code. Emphasis is given to the explanation of new or revised provisions that may be unfamiliar to code users. In addition, comments are included for some items contained in previous editions of the code to make the present commentary independent of the previous editions. Comments on...