ACI 550.3M

Description / Abstract: This Standard defines requirements for a certain type of hybrid special moment frame composed of precast concrete beams jointed at their connections to columns that are continuous past those joints. Whereas these frames do not satisfy all of the prescriptive requirements of 21.5 through 21.7 of ACI 318M-11, analyses, tests, and reporting requirements in accordance with ACI 374.1 have established dependable and predictable strength, energy dissipation, stiffness, and drift capacities for characteristic beam-column configurations of the frames described in this Standard. Such special moment frames are permitted for structures assigned to SDC D, E, or F in accordance with 21.8.4 of ACI 318M-11.

The intended user of this Standard is a licensed design professional experienced in earthquake-resistant design and precast concrete design and construction.

The requirements of this Standard supplement those of ACI 318M-11 and the general building code, and shall govern in all matters pertaining to the design and construction of the hybrid special moment frames described in this Standard, except wherever this Standard is in conflict with requirements of the legally adopted general building code.

The requirements described in this Standard are for hybrid special moment frames with:

1. Equal moment strengths for the top and bottom energydissipating bars that cross the interface between the precast beam and column; and

2. Post-tensioning tendons that are unbonded from anchor to anchor and concentrically located within the cross section of the beam.

All precast and reinforced concrete components and systems for the moment frames, and the associated gravity load frames, shall be designed to satisfy the requirements of ACI 318M-11 except as modified by this Standard.

The special inspection requirements of 1.3.5 of ACI 318M-11 shall be satisfied for all precast and reinforced concrete components and systems for the special moment frames.