Fundamental Study on Control of Yield Position of RC Piers

Many of the older RC piers in Japan have stepped sections (referred to as cut-off sections) with a reduced amount of longitudinal reinforcement in response to the cross-sectional force. Figure 1 shows a RC pier with a cut-off section stripped by an earthquake. In this study, the relationship between the seismic yielding coefficient and equivalent natural period for each soil type was investigated based on horizontal cyclic loading tests on specimens simulating piers with cut-off sections. Dynamic response analyses were conducted for the two yielding types obtained from the cyclic loading tests, and the non-linear response spectrum were generated. The results showed that, for a given natural period, piers yielding at a cut-off section may change to piers not yielding at a cut-off section, depending on the ground conditions. This suggests that for a given natural period, it is possible to control damage at the pier bases through ground improvement.