Investigation of Composite Action on Seismic Performance of Weak-axis Column-tree Moment Connections

This paper presents an experimental study on a developed weak-axis column-tree moment connection subjected to horizontal cyclic loading. In order to study possible positive or negative effect of a composite slab on the seismic performance of the proposed connection, six cruciform specimens were designed and constructed in pairs, where one specimen was bare steel joint and the other involved a composite slab. The standard, cover-plate, and material-changed connection details were considered. The test program is described in detail, and then the structural behavior of test specimens is discussed based on the test data. The tests revealed that although designed with 50% degree of shear connection, the concrete slab still caused obvious upward shift of the neutral axis and increase the strain demand on the bottom flange. But it is clear from the comparison of results that the composite joint specimens performed slightly better than the bare steel counterparts in terms of load-displacement hysteretic curves and energy dissipation capacity, as the concrete slab could effectively enhance the stability of the steel beam and delay the deterioration of the strength and stiffness. The cover-plate connection appears to be one of the more promising moment connection schemes which are able to deliver a much higher level of stability and energy dissipation capacity. The maximum magnitude of slab-steel beam interface slip was less than 0.5 mm, indicating that the concrete floor slab and steel beam could work well together under 50% partial shear connection.