水平2方向地震動を受ける鋼製橋脚の耐震安全性に関する実験的研究

Abstract

本研究では，水平2方向地震動を受ける鋼製橋脚の耐震安全性上の相違を検討するために， 9種類の正方形補剛断面鋼製橋脚に対して，静的繰返し実験，非線形振動解析，水平1方向および水平2方向ハイブリッド実験を行った. これらの実験及び解析結果を用い，鋼製橋脚が水平2方向地震力に独立および同時作用されたときの最大耐力，応答変位を比較し，水平2方向地震動に対する鋼製橋脚の耐震安全性を検討した.水平2方向地震動を受ける鋼製橋脚は，その最大荷重が，平均的に1方向載荷時の約85%となり，応答変位は平均的iこ1方向載荷時の1.25倍となった.水平2方向地震動の同時作用を無視すると，橋脚耐力の過大評価，応答変位の過小評価などのことを明らかにした.

In this study, static cyclic loading tests, uni-directional hybrid tests, uni-directional nolinear seismic simulation using curve approximate hysteretic model developed for steel piers and bi-directional hybrid tests are conducted to clarify seismic performance of steel bridge piers under bidirectional ground motion excitation. Nine bridge models applying 3 types of bridge pier specimens and 3 ground type conditions are designed based on the current seismic design specification. The response of these bridge models under uni-and bidirectional ground motions are obtained by pseudodanamic tests and numerical simuations. By comparing these tests and simulation results, it is found that the bridge piers could be collapsed under bi-direction ground motions, which are regarded as safe under uni-directional loading. Under the bidirectional seismic action, the capacity of steel piers degrades to averagely 84%, and their response displacement increases 20% more than the values obtained by convential uni-directional loading.