山区桥墩抗滚石冲击的双腔椭圆偏心包裹结构研究

山区桥梁墩柱因刚性大而抗冲击效果差，常被滚石冲击损毁，但目前还缺乏有效防治措施。为此，在科学解析滚石对桥墩的弹塑性冲击破坏机理的前提下，基于耗能减震理论提出了一种充填泡沫铝的双腔椭圆偏心桥墩包裹抗冲击结构。继而综合MTS试验数据，采用动力有限元技术对滚石冲击下桥墩防护新结构的动力响应进行计算和分析，并优化结构设计。结果表明:定向椭圆偏心包裹泡沫铝层可显著延长冲击历时，降低冲击荷载，其结构形式经济高效；包裹层厚度适当增加有利于控制墩柱对冲击的动力响应，但过厚也会因结构整体性增大而弱化甚至降低防护效果；双腔充填的"外薄外密"模式最利于控制桥墩塑性应变和冲击挠度，耗能效果更好。总体上，新结构可大幅降低滚石的最大冲击力，保证桥墩结构安全运行。

STUDY ON ELLIPTIC ANTI ROCK-FALL IMPACT STRUCTURE WITH DOUBLE ENERGY DISSIPATION LAYERS WRAPPING UP PIER ECCENTRICALLY IN MOUNTAINS

The pier of common bridge in mountain areas can be easily damaged under rock-fall impact due to its high stiffness. However, there is lack of effective measures to protect it. Based on the study of elastic-plastic mechanism of rock-fall impact on pier, and according to energy dissipation theory, an elliptic structure with two cavities filled with aluminum foam is proposed. By combining the MTS test resutls, the dynamic response and optimized design of the new structure is analyzed by dynamic finite element method. The results show the elliptic structure wrapping up pier eccentrically can weak impact efficiently and enhance system safety economically. Meanwhile, the thicker aluminum foam layer would dissipate more impact energy. However, when the layer is too thick, large rigidity of structure is induced. In addition, among the different filled modes, the structure with a thin outer layer and filled with large intensity aluminum foam can control plastic deformation and pier deflection very well. The new structure can keep the safety by weakening the impaction and dissipating energy significantly.