Part 1: General

Part 2: Loads & Analysis

Part 3: Members

Part 4: Joints/Connections/Anchors

Part 5: Earthquake Resistance

Part 6: Materials & Durability

Part 7: Strength & Serviceability

Part 8: Reinforcement

Part 9: Construction

Part 10: Evaluation

REFERENCES & Appendices

Heads up: There are no amended sections in this chapter.
This chapter shall apply to the design and detailing of cast-in-place beam-column and slab-column joints.
Beam-column joints shall satisfy the detailing provisions of 15.3 and strength requirements of 15.4.
Beam-column and slab-column joints shall satisfy 15.5 for transfer of column axial force through the floor system.
If gravity load, wind, earthquake, or other lateral forces cause transfer of moment at beam-column joints, the shear resulting from moment transfer shall be considered in the design of the joint.
At corner joints between two members, the effects of closing and opening moments within the joint shall be considered.
If a beam framing into the joint and generating joint shear has depth exceeding twice the column depth, analysis and design of the joint shall be based on the strut-and-tie method in accordance with Chapter 23 and (a) and (b) shall be satisfied:
(a) Design joint shear strength determined in accordance with Chapter 23 shall not exceed ϕVn calculated in accordance with 15.4.2.
(b) Detailing provisions of 15.3 shall be satisfied.
A column extension assumed to provide continuity through a beam-column joint in the direction of joint shear considered shall satisfy (a) and (b):
(a) The column extends above the joint at least one column depth, h, measured in the direction of joint shear considered.
(b) Longitudinal and transverse reinforcement from the column below the joint is continued through the extension.
A beam extension assumed to provide continuity through a beam-column joint in the direction of joint shear considered shall satisfy (a) and (b):
(a) The beam extends at least one beam depth h beyond the joint face.
(b) Longitudinal and transverse reinforcement from the beam on the opposite side of the joint is continued through the extension.
A beam-column joint shall be considered to be confined for the direction of joint shear considered if two transverse beams satisfying (a), (b), and (c) are provided:
(a) Width of each transverse beam is at least three-quarters of the width of the column face into which the beam frames
(b) Transverse beams extend at least one beam depth h beyond the joint faces
(c) Transverse beams contain at least two continuous top and bottom bars satisfying 9.6.1.2 and No. 3 or larger stirrups satisfying 9.6.3.4 and 9.7.6.2.2
For slab-column connections transferring moment, strength and detailing requirements shall be in accordance with applicable provisions in Chapter 8 and Sections 15.3.2 and 22.6.
Beam-column joints shall satisfy 15.3.1.2 through 15.3.1.4 unless (a) through (c) are satisfied:
(a) Joint is considered confined by transverse beams in accordance with 15.2.8 for all shear directions considered
(b) Joint is not part of a designated seismic-force-resisting system
(c) Joint is not part of a structure assigned to SDC D, E, or F
Joint transverse reinforcement shall consist of ties, spirals, or hoops satisfying the requirements of 25.7.2 for ties, 25.7.3 for spirals, and 25.7.4 for hoops.
At least two layers of horizontal transverse reinforcement shall be provided within the depth of the shallowest beam framing into the joint.
Spacing of joint transverse reinforcement s shall not exceed 8 in. within the depth of the deepest beam framing into the joint.
Except where laterally supported on four sides by a slab, column transverse reinforcement shall be continued through a slab-column joint, including column capital, drop panel, and shear cap, in accordance with 25.7.2 for ties, 25.7.3 for spirals, and 25.7.4 for hoops.
Development of longitudinal reinforcement terminated in the joint or within a column or beam extension, as defined in 15.2.6(a) and 15.2.7(a), shall be in accordance with 25.4.
Longitudinal reinforcement terminated in the joint with a standard hook shall have the hook turned toward mid-depth of the beam or column.
Joint shear force Vu shall be calculated on a plane at mid-height of the joint using flexural tensile and compressive beam forces and column shear consistent with (a) or (b):
(a) The maximum moment transferred between the beam and column as determined from factored-load analysis for beam-column joints with continuous beams in the direction of joint shear considered
(b) Beam nominal moment strengths Mn
Design shear strength of cast-in-place beam-column joints shall satisfy:
ϕVnVu
ϕ shall be in accordance with 21.2.1 for shear.
Vn of the joint shall be calculated in accordance with Table 15.4.2.3.
Table 15.4.2.3—Nominal joint shear strength Vn
Column Beam in direction of Vu Confinement by transverse beams according to 15.2.8 Vn, lb[1]
Continuous or meets 15.2.6 Continuous or meets 15.2.7 Confined
Not confined
Other Confined
Not confined
Other Continuous or meets 15.2.7 Confined
Not confined
Other Confined
Not confined
[1]λ shall be 0.75 for lightweight concrete and 1.0 for normalweight concrete.
Effective cross-sectional area within a joint, Aj, shall be calculated as the product of joint depth and effective joint width. Joint depth shall be the overall depth of the column, h, in the direction of joint shear considered. Effective joint width shall be the overall width of the column where the beam is wider than the column. Where the column is wider than the beam, effective joint width shall not exceed the lesser of (a) and (b):
(a) Beam width plus joint depth
(b) Twice the perpendicular distance from longitudinal axis of beam to nearest side face of the column
If fc' of a floor system is less than 0.7fc' of a column, transmission of axial force through the floor system shall be in accordance with (a), (b), or (c):
(a) Concrete of compressive strength specified for the column shall be placed in the floor system at the column location. Column concrete shall extend outward at least 2 ft into the floor system from face of column for the full depth of the floor system and be integrated with floor concrete.
(b) Design strength of a column through a floor system shall be calculated using the lower value of concrete strength with vertical dowels and transverse reinforcement as required to achieve design strength.
(c) For beam-column joints laterally supported on four sides by beams of approximately equal depth that satisfy 15.2.7 and 15.2.8(a) and for slab-column joints supported on four sides by the slab, it shall be permitted to calculate the design strength of the column using an assumed concrete strength in the column joint equal to 75 percent of column concrete strength plus 35 percent of floor system concrete strength, where the value of column concrete strength shall not exceed 2.5 times the floor system concrete strength.
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