Page Comparison

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Notation

d_b = nominal diameter of bar, wire, or prestressing strand, in
f_c^'₌ specified compressive strength of concrete, psi
√fc‘ = square root of specified compressive strength of concrete, psi
f_y = specified yield strength of nonprestressed reinforcement,psi
l_d = development length in tension of deformed bar, deformed wire, plain and deformed welded wire reinforcement, or pretensioned strand, in.
l_dc = development length in compression of deformed bars and deformed wire, in.
l_dh = development length in tension of deformed bar or deformed wire with a standard hook, measured from outside end of hook, point of tangency, toward critical section, in.
l_dm = the required development length if bar is not entirely embedded in confined concrete, in.
s = center-to-center spacing of items, such as longitudinal reinforcement, transverse reinforcement, tendons, or anchors, in.
λ = modification factor to reflect the reduced mechanical properties of lightweight concrete relative to normalweight concrete of the same compressive strength

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Beam-Column Joint Transverse Reinforcement

According to ACI 15.3.1.1, beam-column joints should satisfy ACI 15.3.1.2 , 15.3.1.3 and 15.3.1.4 unless all three conditions are satisfied:

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Beam-Column Joint for Earthquake-Resistant Structures

Ordinary moment frames

All the conditions described above are valid for joints of ordinary moment frames.

Intermediate moment frames

All the conditions described above are valid for joints of intermediate moment frames.

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• For Grade 60 or S420, the smaller 8d_b of the smallest longitudinal bar is enclosed and 8 in.

• For Grade 80, the smaller 6d_b of the smallest longitudinal bar is enclosed and 6 in.

• One-half of the smallest cross-sectional dimension of the column.

Special moment frames

All the conditions described above are valid for joints of intermediate moment frames.

According to ACI 18.8.3.1, Beam-column joint transverse reinforcement should satisfy ACI 18.7.5.2, ACI 18.7.5.3, ACI 18.7.5.4, and ACI 18.7.5.7, except as permitted in ACI 18.8.3.2.

According to ACI 18.8.3.2, the amount of transverse reinforcement required by ACI 18.7.5.4 can be reduced by one-half, and the spacing required by ACI 18.7.5.3 can be increased to 6 in. within the overall depth h of the shallowest framing beam where the following conditions are satisfied:

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According to ACI 18.8.3.3, if beam-column joint confinement is not provided by a beam framing into the joint, longitudinal beam reinforcement outside the column core should be confined by transverse reinforcement passing through the column. This transverse reinforcement spacing should satisfy the requirements of ACI 18.6.4.4. Also, this transverse reinforcement should satisfy the requirements of ACI 18.6.4.2 and ACI 18.6.4.3.

Development Length of Bars in Tension

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