CHAPTER 13 BEAMS - American Concrete Institute

1 ACI 318-14 CHAPTER 13 Code, Approved Version, Revised 2013-07-25. 1 CHAPTER 13 BEAMS . 2. 3 Note: References to chapters that have not yet been approved are noted by the Letter Balloted (LB) version. 4 references to other chapters that have already been approved,All reference to other chapters a Ref to based on LB12-1. 5 Included Changes: 6 CD025. 7 CG035. 8 CE200. 9 CHAPTER Y. 10. 11 Scope 12. 13 Provisions of this CHAPTER shall apply to the design of nonprestressed and prestressed 14 BEAMS . The provisions shall also apply to the design of : < > < >. 15. 16 (a) composite BEAMS of Concrete elements constructed in separate placements but 17 connected so that all elements resist loads as a unit.

2 18 (b) one-way joist systems with additional requirements in accordance with 19. 20 Deep BEAMS shall be designed in accordance with < >. 21 Ref to based on LB12-1. 22. 23 General 24. 25 Materials 26. 27 Design properties for Concrete shall conform to CHAPTER 5. <~>. 28. 29 Design properties for steel reinforcement shall conform to CHAPTER 6. <~>. 30. 31 Connection to other members 32. 33 For cast-in-place beamsconstruction, beam -column joints shall be in accordance 34 withsatisfy the requirements of < >. 35 Ref to based on LB11-3. 36. 37 For precast beamsconstruction, connections shall be in accordance withsatisfy the 38 force transfer requirements ofRef <~>based on LB11-3.

3 To 39. 40 Stability 41. 42 If a beam is not continuously laterally braced, (a) and (b) shall be satisfied: 43. 44 (a) spacing of lateral bracing shall not exceed 50 times the least width of compression 45 flange or face; < >. 1. ACI 318-14 CHAPTER 13 Code, Approved Version, Revised 2013-07-25. 46. 47 (b) spacing of lateral bracing shall take into account effects of eccentric loads. < >. 48. 49 In prestressed BEAMS , buckling of thin webs and flanges shall be considered. If there 50 is intermittent contact between prestressed reinforcement and an oversize duct, member buckling 51 between contact points shall be considered.

4 < >. 52. 53 T- beam construction 54. 55 In T- beam construction, Concrete in the flange and web shall be placed 56 monolithically or made composite in accordance with < > Ref to based on LB11-3. 57. 58 Effective flange width shall be in accordance with < > < > < >. 59 Ref to based on LB11-6. 60. 61 For torsional design according to , the overhanging flange width used to calculate 62 Acp, Ag, and pcp shall be in accordance with (a) and (b): 63. 64 (a) The overhanding overhanging flange width shall include that portion of slab on each side 65 of the beam extending a distance equal to the projection of the beam above or below the 66 slab, whichever is greater, but not greater than four times the slab thickness.

5 < >. 67 < >. 68. 2. 69 (b) The overhanging flanges shall be neglected in cases where the parameter Acp pcp for 70 solid sections or Ag2 pcp for hollow sections calculated for a beam with flanges is less 71 than that calculated for the same beam ignoring the flanges. < >. 72. 73. 74 Design limits 75. 76 Minimum beam depth 77. 78 For nonprestressed BEAMS not supporting or attached to partitions or other 79 construction likely to be damaged by large deflections, overall beam depth h shall not be less 80 than the limits in Table , unless the calculated deflection limits of are satisfied. 81 < >.

6 82. 83 Table Minimum depth of nonprestressed BEAMS Minimum h, in. [1]. Support condition Simply supported /16. One end continuous Both ends continuous /21. Cantilever /8. 2. ACI 318-14 CHAPTER 13 Code, Approved Version, Revised 2013-07-25. [1]. 84 Expressions applicable for normalweight Concrete and fy = 60,000 psi. 85 Minimum h shall be modified by through , as appropriate. 86. 87 For fy other than 60,000 psi, the expressions in Table shall be 88 multiplied by ( + fy/100,000). <Table >. 89. 90 For nonprestressed BEAMS made of lightweight Concrete having wc in the 91 range of 90 to 115 lb/ft3, the expressions in Table shall be multiplied by the 92 greater of (a) and (b): <Table >.

7 93. 94 (a) 95. 96 (b) 97. 98 For nonprestressed composite BEAMS made of a combination of lightweight 99 and normalweight Concrete , shored during construction, and where the lightweight 100 Concrete is in compression, the modifier of shall apply. < >. 101. 102 The thickness of a Concrete floor finish shall be permitted to be included in h if it is 103 placed monolithically with the beam , or if the floor finish is designed to be composite with the 104 beam in accordance with < > Ref to based on LB11-3. 105. 106. 107 Calculated deflection limits 108. 109 For nonprestressed BEAMS not satisfying and for prestressed BEAMS , immediate 110 and time-dependent deflections shall be calculated in accordance with and shall not exceed 111 the limits in < > < > < > < > < >.

8 112. 113 For nonprestressed composite Concrete BEAMS satisfying , deflections occurring 114 after the member becomes composite need not be calculated. Deflections occurring before the 115 member becomes composite shall be investigated unless the precomposite depth also satisfies 116 < >. 117. 118 Reinforcement strain limit in nonprestressed BEAMS 119. '. 120 For nonprestressed BEAMS with Pu < f c Ag , t shall be at least < >. 121. 122 Stress limits in prestressed BEAMS 123. 124 Prestressed BEAMS shall be classified as Class U, T, or C in accordance with 125 < >. 126. 127 Stresses in prestressed BEAMS immediately after transfer and at service loads shall not 128 exceed the permissible stresses in < >.

9 3. ACI 318-14 CHAPTER 13 Code, Approved Version, Revised 2013-07-25. 129. 130 Required strength 131. 132 General 133. 134 Required strength shall be calculated in accordance with the factored load 135 combinations defined in CHAPTER 7 and analysis procedures defined in CHAPTER 8. <~>. 136. 137 For prestressed BEAMS , effects of reactions induced by prestressing shall be 138 considered in accordance with < > <CG034>. 139. 140 Factored moment 141. 142 For BEAMS built integrally with supports, Mu at the support shall be permitted to be 143 calculated at face of support. < >. 144. 145 Factored shear 146.

10 147 For BEAMS built integrally with supports, Vu at the support shall be permitted to be 148 calculated at face of support. < >. 149. 150 Sections between the face of support and a critical section located d from the face of 151 support for nonprestressed BEAMS and h/2 from the face of support for prestressed BEAMS shall be 152 permitted to be designed for Vu at that critical section if (a) through (c) are satisfied: < >. 153 < > < >. 154. 155 (a) Support reaction, in direction of applied shear, introduces compression into the end 156 region of the beam ;. 157. 158 (b) Loads are applied at or near the top surface of the beam .