ACI 421.2R-10 PDF Download

The ACI 421.2R-10 standard addresses the issue of brittle punching failure in flat plate-column connections. This type of failure can occur when shear forces are transferred between slabs and columns, combined with unbalanced moments. During an earthquake, the significant horizontal displacement of a flat plate-column connection can induce additional slab shear stresses, potentially leading to collapse.

The standard references past earthquakes where flat plate structures have failed due to punching shear, such as the 1985 Mexico earthquake and the 1994 Northridge, CA, earthquake. It emphasizes the importance of designing flat plate-column connections to prevent brittle punching shear failure, even when an independent lateral-force-resisting system is provided. The goal is to ensure the connections can accommodate the moments and shear forces associated with the displacements that occur during earthquakes.