基于标准化水平残余位移的沉入式钢圆筒防波堤抗震性能研究

STUDY ON THE ASEISMIC PERFORMANCE OF EMBEDDED STEEL CYLINDER BREAKWATER FOR BACKFILL SAND FOUNDATION BASED ON NORMALIZED RESIDUAL HORIZONTAL DISPLACEMENT

根据国际航运协会《港口结构抗震设计指南》、日本港口结构震害调查结果和钢圆筒结构特点,将标准化水平残余位移作为沉入式钢圆筒防波堤的抗震性能指标,同时运用振动台试验和数值模拟研究了回填砂地基防波堤的动力特性,并评估了防波堤的抗震性能。结果表明,当设计地震动为1.7 m/s2时回填砂地基防波堤处于可服役状态,设计地震动为3.2 m/s2时防波堤处于可修复状态,不满足防波堤性能等级为S的要求,建议在设计中考虑远场地震和近场地震对防波堤抗震性能的影响。振动台试验研究发现当地震波加速度峰值为3.2 m/s2时筒外回填砂由于液化导致其对防波堤的侧向力改变,防波堤试验模型发生明显的倾斜现象,建议在地基加固设计过程中重点考虑筒外回填砂。当地震波加速度峰值为1.7 m/s2和3.2 m/s2时,钢圆筒筒壁应力最大值随高度的增加均呈现减小的趋势,同时钢圆筒防波堤存在两处薄弱环节,分别位于筒底及泥面处,因此结构设计时应优先考虑。

It was defined that normalized residual horizontal displacement was the aseismic performance index of an embedded steel cylinder breakwater according to aseismic design guidelines for port structures(PIANC),as well as to the statistical results of seismic damage for port structures in Japan and to the characteristics of a steel cylinder structure.Meanwhile,the dynamic characteristics of breakwater for backfill sand foundation were studied by a shaking table test and numerical simulation,and the aseismic performance of a breakwater was evaluated.The study results show that a breakwater is serviceable under design earthquake motion 1.7 m/s2 and repairable under design earthquake motion 3.2 m/s2,which do not satisfy the demand of grade S for the breakwater,and it is suggested that the effect of far-field and near-field earthquakes is considered in the design of aseismic performance for a breakwater.The slip phenomenon is obvious for backfill sand outside the cylinder under the peak ground acceleration 3.2 m/s2 through a shaking table test,and the breakwater model tilts by the reason of the change of the lateral force due to liquefaction of backfill sand outside the cylinder,it is thusly advised that backfill sand outside the cylinder should be considered in the process of design for foundation reinforcement.The stress maximum for the wall of a steel cylinder both decrease gradually with increasing height for the peak ground acceleration 1.7 m/s2 and 3.2 m/s2,and there are two weak points on the bottom and mudline of the cylinder wall,structural design should be thusly considered as priority.