落石冲击速度对双幅式空心薄壁超高墩动力响应影响研究

Effect of Rockfall Impact Velocity on the Dynamic Response of Twin-Deck Hollow Thin-Walled Super-High Bridge Piers

摘要: 西南山区连续刚构桥常采用空心薄壁超高墩，其在施工与运营阶段易遭受落石冲击，结构安全问题突出。为研究落石冲击速度对双幅式空心薄壁超高墩动力响应的影响，本文以某双幅式空心薄壁超高墩连续刚构桥为工程背景，基于LS-DYNA建立1:20缩尺有限元模型，并通过已有钢筋混凝土梁落锤冲击试验对建模方法进行验证；在此基础上，系统分析了不同冲击速度下桥墩的塑性损伤分布、撞击力时程特征及横向位移响应规律。结果表明：随着冲击速度增大，桥墩塑性损伤持续加剧，损伤范围由撞击区逐步向系梁连接区及墩底扩展，撞击力峰值增大、持续时间延长，较高速度下还会出现再次接触现象；此外，随着冲击速度的增大，桥墩横向位移响应显著增大，振动周期增大，残余变形更为明显，表明高速度冲击下结构易进入塑性变形阶段。

Abstract: Continuous rigid frame bridges in mountainous areas of Southwest China commonly adopt hollow thin-walled super-high piers, which are susceptible to rockfall impacts during construction and service stages, posing significant threats to structural safety. To investigate the influence of rockfall impact velocity on the dynamic response of twin-deck hollow thin-walled super-high bridge piers, this study takes a continuous rigid frame bridge with such piers as the engineering background. A 1:20 scaled finite element model was established using LS-DYNA, and the modeling approach was validated against existing drop-weight impact test results of reinforced concrete beams. Based on the validated model, the plastic damage distribution, impact force time-history characteristics, and lateral displacement responses of the piers under different impact velocities were systematically analyzed. The results indicate that with increasing impact velocity, the plastic damage of the pier intensifies and expands from the impact region to the coupling beam connections and pier base. Meanwhile, the peak impact force increases and the contact duration becomes longer, and secondary contact may occur at higher velocities. In addition, the lateral displacement response of the pier is significantly amplified with increasing impact velocity, accompanied by a longer vibration period and more pronounced residual deformation, indicating that the structure is more likely to enter the plastic deformation stage under high-velocity impacts.