Effect of anchors on the seismic performance of exposed column-base plate weak-axis connections

The number and magnitude of earthcorrquakes are increasing in South Korea. However, unreliable exposed column-base plate connections of low-rise steel buildings are still easily found in the field. Therefore, based on intensive field inspection, six large-scale exposed column-base plate weak-axis connection specimens were examined, under both axial compression and lateral cyclic loading, to develop stable and reliable column-base plate joints in the weak-axis direction. From the test results of the first set of specimens, it was found that the seismic performance of field-representative specimens was quite poor due to a "rocking" phenomenon observed between the base plate and concrete foundation because of the severe residual plastic deformation of round-section anchor bolts. To reduce the rocking phenomenon, a second set of specimens was fabricated and evaluated. By using an eight threaded anchor-layout, the rocking phenomenon was substantially reduced. Therefore, it is strongly recommended to use eight threaded anchors in three rows in order to enhance seismic performance, rather than four in two rows, for exposed column-base plate weak-axis connections.