Improved Strength Model for Interior Flat Plate–Column Connections Subject to Unbalanced Moment

A numerical study of interior flat plate–column connections subjected to unbalanced moments was performed by using nonlinear finite element analysis. The distribution and strength of the eccentric shear and flexural moment that develop at the connections were studied. The results showed that the distribution of the eccentric shear stress was different from those specified in current design codes, and the eccentric shear strength was significantly affected by the flexural moment acting at the same critical section. Based on the findings, an improved design method for the interior flat plate–column connections was developed and was verified by the comparisons with existing test results. These comparisons showed that the proposed design method predicted the punching shear strength of the connections subject to unbalanced moments better than the current design methods.