Nonlinear model simulating load–deformation relationship of flat plate structures

• To develop a nonlinear static analysis method of flat plate structures.
• To develop a practical 3-D method for flat plate with irregular column layout.
• For comprehensive understanding of failure mechanism of slab-column connections.
• To improve the prediction of load-deformation relation of slab-column connections.

In this study, an analytical method for flat plate systems subjected to lateral load was developed for application to nonlinear static analysis. In the case of flat plate systems, it has been recognized that the structural damages developed by gravity and lateral load are concentrated at their slab–column connections. To investigate such behavioral characteristics of the connections, three independent nonlinear hinges were introduced with simulating flexural, shear, and torsional nonlinearity. The behavior of the nonlinear hinges was defined by using backbone curves based on current design codes of KCI 2012 and ACI 318-11. The columns and slabs, excluding the slab–column connections, were modeled by elastic line and plate elements. For verification, the proposed analytical method was applied to existing test specimens subjected to unbalanced moment. The analysis results showed that the proposed method can simulate the entire load–deformation behavior of the test specimens, including the strength and deformation capacity. In addition, parametric studies were performed with respect to primary test parameters: column aspect ratio, gravity load ratio, effective depth, reinforcement ratio, slab length, and boundary condition. The effect of these primary test parameters on the structural behavior of the flat plate systems was also investigated.