ABSTRACT
Generally, an exposed-type column base consists of anchor bolts and an elastic thick base plate. Its restoring force characteristics are observed to be slip-type due to a gap opening up between a nut of the anchor bolt and the base plate, caused by plastic elongation of the anchor bolt. Many studies have shown that slip-type behavior has almost no effect on the response characteristics of upper stories of moment-resisting frames. However, column bases need to have higher energy absorption capacity when the strength of the first story is lower than those of the other stories due to energy concentration in the first story. The first story requires a large story drift angle to absorb the large energy in exposed-type column bases that have slip-type characteristics. A new technique for improving slip-type behavior has been proposed by the authors (Takamatsu, Tamai and Yamanishi 2005). Slip behavior can be decreased by driving a wedge under constant compression with a spring into the gap between the nut and the base plate, thus eliminating the gap generated by the expanded anchor bolt. This exposed-type column base with wedge devices thus shows non-slip-type restoring force characteristics. Slip does not take place and the load in the loading cycles builds up from the origin.
