ACI 550.5-18 PDF Download

ACI 550.5-18 is a standard that provides code requirements for the design of precast concrete diaphragms used in structures subjected to earthquake motions. The standard specifically refers to the design provisions of ASCE/SEI 7-16 Section 12.10.3 and ACI 318.

The response of precast concrete diaphragms to earthquake motions relies on the strength, stiffness, and deformation capacities of the connectors and reinforcement at the joints between precast concrete members. The standard focuses on structures assigned to Seismic Design Category (SDC) C, D, E, or F as specified in ASCE/SEI 7. The seismic forces for the design of precast concrete diaphragms, their chords, and collectors are linked to force reduction factors and shear overstrength specified in ASCE/SEI 7-16 Chapter 12 and Chapter 14, respectively.

The shear overstrength is determined based on the design methodology (elastic or ductile) used for the diaphragm. Regardless of the chosen design option, the standard targets elastic response for shear connections under the maximum considered earthquake. The design option to be used depends on the assigned design category, as well as the span and aspect ratio of the diaphragm. Additionally, the selection of the design option is associated with minimum requirements for the tensile deformation capacity of the connections and reinforcement at joints.