Non-slip-type restoring force characteristics of an exposed-type column base

This paper describes an experimental study on exposed-type column bases with new restoring force characteristics. Generally, an exposed-type column base consists of elastic/plastic anchor bolts and an elastic thick base plate. The restoring force characteristics of these column bases are observed to be slip-type due to the gap between the nut of the anchor bolt and the base plate, caused by the plastic elongation of the anchor bolt. These restoring force characteristics can be governed by elastic/plastic anchor bolts, an elastic/plastic base plate and/or a gap between the nut and the base plate. In particular, the gap between the nut and the base plate can be eliminated by means of a new device consisting of a wedge compressed by a spring and a counter-wedge. To show the fundamental characteristics of the new column base, two kinds of specimens were tested. The conclusions obtained are as follows. (1) The cyclic characteristics of conventional column bases with elastic/plastic anchor bolts and an elastic base plate became slip-type. (2) The cyclic characteristics of column bases with the gap between nut and base plate eliminated by use of the device became non-slip-type, that is, linear from the origin at each loading step.