钢筋混凝土柱式桥墩落石冲击分析方法

为研究落石冲击对钢筋混凝土(RC)桥墩安全性能的影响,建立一种考虑截面抗剪能力率相关性的RC柱式墩崩塌落石撞击损伤状态评价方法.首先,通过与钢筋混凝土梁落锤实验结果对比验证数值模拟方法可靠性,考虑桩基与土层相互作用建立了彻底关大桥下部结构落石撞击有限元模型.其次,以KC模型修正的Priestley公式描述混凝土动载抗剪强度,以剪力破坏参数定义截面损伤等级,分析墩柱截面不同撞击场景下的损伤状态.最后,进行混凝土抗压强度、墩柱截面面积、箍筋间距、墩柱长细比参数敏感性分析.结果表明:全局平均等效静力方法应用于落石撞击荷载静力简化存在缺陷,在高冲击强度场景下衰减段长持时使得等效静力偏低;引入墩柱截面抗剪能力率相关性能够更准确地描述落石冲击损伤状态;增大墩柱截面面积和提高箍筋配筋率能够有效地降低RC柱式桥墩落石撞击损伤.

Analysis method for the reinforced concrete column piers subjected to rockfall impact

To investigate the performances of reinforced concrete columns under rockfall impact, a damage state analysis method for RC columns is proposed by considering the strain rate effect of dynamic shear capacity. Firstly, the accuracy and predicting capacity of proposed FE model are validated with a drop weight test, and then a FE model of the substructure of Chediguan Bridge is established regarding the interaction between piles and soil layers. Secondly, the static shear capacity of RC columns is considered by the equations presented by Priestley, and the strain rate effect of the concrete is described by K&C model. Then, a series of cases are conducted to obtain the damage degree of RC columns subjected to varying impact conditions. Finally, the effect of sectional area of columns, transverse reinforcement ratio, concrete strength and the slenderness ratio on the shear damage degree of the columns are examined through a parametric analysis. Results show that the global average method exhibits a disadvantage since the descent stage of rockfall impact force-time history has a longer duration, it would lead to a low equivalent static load under high impact strength. The proposed analysis approach can more accurately evaluate the damage state of RC columns subject to rockfall impact by considering dynamic shear capacity. The parametric analysis results show that the increasing of the sectional area and transverse reinforcement ratio inordinately reduce the damage level of RC columns.