Single Column Test - Test#5 - Cyclic with Asymmetrical Loading Histories

An experimental program that consists of six quasi-static and two hybrid tests was conducted to study and quantify the inelastic behavior of deep steel wide flange column sections up to collapse. The tests were performed on 1:8 scaled W36X652 column sections. Two monotonic and four cyclic quasi-static tests were carried out. The monotonic loading protocols consist of interstory drift ratio, rotation, as well as constant and variable compression axial load histories. The cyclic loading protocols consist of symmetric and unsymmetric histories of interstory drift ratio, rotation at the tip of the column, and levels of axial load that vary between tension and compression. These protocols are meant to simulate the demands experienced by first-story corner columns in tall steel moment-resisting frame structures.

A three-actuator test setup at NEES@ Buffalo lab was utilized for this experiment. For the quasi-static tests, a displacement-controlled horizontal actuator was used to impose the lateral displacement at the tip of the column. Two vertical actuators were used to impose both axial force and rotation demands. One of the vertical actuators was forced-controlled and the other one displacement-controlled.

In the current experiment, a symmetric cyclic lateral displacement and rotation were imposed at the tip of the specimen simultaneously with a variable axial load. In addition, pairs of increasing amplitude cycles were interrupted by a pair of smaller amplitude trailing cycles.

In the current experiment, unsymmetrical drift and rotation loading histories were applied to induce a ratcheting-type response in the column. ). Increasing levels of axial force (fluctuating between tension and compression) were applied until the yield drift value of the column was achieved. From that point on, the axial load cycled between constant levels of tension (27%, 47 kips) and compression (57%, 83 kips). The axial force was applied out-of-phase with the drift demand at the tip of the column.