Tensile strength and failure mechanism of internal diaphragms in wide flange beam-to-box column connections with concrete filling

This paper presents a verification of tensile strength and failure mechanism of internal diaphragms in wide flange (WF) beam-to-box column connections with and without concrete filling. The flexural load transfer mechanism from the beam flange to column was locally evaluated based on a plate-to-box column connection with an internal diaphragm. The objective of this study is to establish an efficient design method for the internal diaphragms in WF-beam-to-box column connections. First, theoretical and experimental approaches were used to evaluate a strength equation considering the effects of the plate-to-column width and column width-to-thickness ratios and concrete filling. Finally, the cyclic performance of the WF-beam-to-box column connections was numerically assessed to validate the design and response of the internal diaphragms. The results showed that concrete filling was able to improve the connection strength by approximately 30% compared to that without concrete filling. It was also confirmed that the plate-to-column width and column width-to-thickness ratios did affect the tensile strength of the connection and must be considered in the strength equation. More importantly, the response of an internal diaphragm designed using the proposed equation in this study was validated and confirmed by both the experiment and the numerical evaluation.