Design of Precast Diaphragm Chord Connections for In-Plane Tension Demands

This paper discusses the design and modeling of a welded chord connection commonly used in pretopped precast double tee panels. In conventional design, the chord is intended to achieve its tension strength based on the axial capacity of the anchorage bars. An experimental study has shown that premature failure of the weld and flexure of the bar may occur, significantly reducing the tension capacity of the connection. A detailed finite-element model is developed and verified with experimental data and used for a parametric investigation. The results indicate that a ductile chord connection, with predictable capacity, can be achieved through concentric placement of the welds relative to the anchorage bar. Variations in faceplate thickness and weld throat are found to alter the load path but do not prevent premature failure. Mechanical debonding of the anchorage bars is found to significantly enhance the deformability of the connection. These findings are incorporated in a force and displacement based design procedure for the chord connection; an example is included for illustration.