跨中受落石冲击的拱形护桥明洞力学响应

Mechanical Responses of Arched Protection Shed of Bridge under Rock-fall Impaction on Midspan of Rooftop

为了解落石冲击下拱形护桥明洞的力学响应特征,以高铁双线拱形护桥明洞为研究对象,采用动力有限元方法,分析质量为2 000 kg的球形落石,从50 m垂直高度处沿不同方向冲击结构顶部跨中时结构的力学响应。研究表明:冲击过程中结构的受力不利部位与冲击前自重作用下相同,上部结构的拱顶、拱脚内侧、边墙墙脚外侧和下部结构桩基的柱顶内侧和柱脚外侧等部位是受力不利部位,且桩基的外侧立柱受力要大于内侧立柱;冲击过程中结构荷载效应变化率以垂直冲击最大,沿结构纵向45°次之,沿结构侧向45°最小;在本次计算范围内,所设计的拱形护桥明洞结构最大应变率小于1×10-3s-1,属准静态力学范围,落石最大侵彻缓冲层深度为0.9 m,而设计的缓冲层厚度为2 m,同时最大、最小应变值均在材料极限应变范围内,说明结构可以承受本次分析工况下的落石冲击;经缓冲层将落石冲击力传递到结构顶部的冲击荷载主要集中在拱顶中部,宽度占结构顶部总宽度的16.7%,拱顶中部承受了整个冲击荷载的44.9%。

In order to learn of the mechanical responses characteristics of arched protection shed of bridge under rock-fall impaction,the action effects of structure are analyzed by dynamic finite element method.The results show that:1)The parts of the superstructure such as crown top,inner side of arch springing and outside of sidewall feet and the substructure′s pile foundation top and foot joint bear large load both before and after rock-fall impaction;and the load on outside piles are larger than that inside piles.2)The magnification rate of the load effect along vertical direction is larger than that 45°along vertical direction;and that 45°along lateral direction is the smallest.3)The maximum strain rate of the structure caused by rock-fall impaction is less than 1×10-3 s-1,which is within the range of quasi-statics scope;the maximum rock-fall penetration depth into buffer layer is 0.9 m,while the design buffer layer is 2 m in depth;the maximum and minimum strain of the structure are within the limit scope of material,which shows that the structure can bear the rock-fall impaction.4)The impaction load acting on the structure top mainly concentrates on the central part of the crown top whose area takes 16.7%of the whole top while bearing 44.9%of the impact load.