Development of improved exposed column-base plate strong-axis joints of low-rise steel buildings

Abstract Due to increasing seismic risk, seismic design has become mandatory even for low-rise structures in Republic of Korea since December 2017. However, it is not difficult to find undesirable exposed column-base plate strong-axis joints of low-rise steel buildings in the field. Such undesirable connections might not have sufficient capacity and stability under earthquake. Therefore, a series of experiments were carried out to develop improved exposed column-base plate strong-axis joints of low-rise steel buildings. In total, seven large-scale column-base plate strong-axis connection specimens were investigated under both axial compression and lateral cyclic loading. It was found that the hysteretic behavior of such improper joints typically used in the field was unstable due to a “rocking” phenomenon between a base plate and concrete foundation by large plastic residual deformation of anchor bolts. To overcome the rocking phenomenon, efforts were made to develop enhanced connections. Based on the test results, considerably improved and stable hysteretic behavior without the rocking phenomenon was obtained by using eight threaded anchor bolts. However, further study is needed to assess the effect of eight threaded anchor bolts on the seismic performances of more various connections.