ACI 550.5M-18 PDF Download

ACI 550.5M-18 is a standard that provides code requirements for the design of precast concrete diaphragms subjected to earthquake motions. This standard specifically focuses on diaphragms used in structures categorized under Seismic Design Category (SDC) C, D, E, or F. The response of these precast concrete diaphragms to earthquake motions is determined by the strength, stiffness, and deformation capacities of the connectors and reinforcement at the joints between the precast concrete members.

The seismic forces applied to the design of these diaphragms are specified in ASCE/SEI 7-16 Section 12.10.3, and the force reduction factors prescribed in ASCE/SEI 7-16 Chapter 12 are considered. The shear overstrength, which is provided by the connections and reinforcement at joints, is also taken into account. The design methodology for the diaphragm, whether it is elastic or ductile, is chosen based on the assigned design category, as well as the span and aspect ratio of the diaphragm.

The selection of the design option is heavily influenced by the minimum requirements for the tensile deformation capacity of the connections and reinforcement at joints. This standard ensures that precast concrete diaphragms are designed to withstand earthquake motions and meet the specified performance criteria outlined in the code. The commentary included in ACI 550.5M-18 provides additional insight and explanations for the code requirements.