超高车辆撞击下预应力混凝土梁损伤机理及损伤评估方法研究

The safety problem of bridge superstructure collision caused by over-height vehicle is one of the important factors in the process of bridge design and maintenance. It is of great difficulty for damage assessment of bridge after impact due to the accidental load and the dynamic nonlinearity of the collision process. Based on a full-scale lateral impact test of a prestressed concrete girder conducted by the applicant, the dynamic responses and the damage mechanism of the bridge during vehicle lateral impact will be investigated in this project by combining numerical simulation with theoretical analysis methods. Then, the damage assessment criterion in terms of residual flexural capacity is established. Based on the refined numerical simulation analysis, the quantitative relationship of the damage states of the girder under different vehicle mass and impact velocity is obtained and the damage levels of the bridge will be proposed. Finally, based on the numerical simulation results and the numerical fitting method, the failure curves of the prestressed concrete girder under different initial impact energies are drawn, and the influence of the geometrical and structural parameters of the girder on the failure curves will be studied. Thus, the damage assessment diagram applicable to the prestressed concrete beams is proposed to realize the vehicle-bridge impact damage assessment. The research results of this project will provide important references for damage assessment and design of the bridge superstructure against over-height vehicles.

超高车辆撞击桥梁上部结构引发的安全问题是桥梁设计与维护过程中需考虑的重要因素之一。荷载的偶然性与碰撞过程的动力非线性特征给桥梁受撞击后的损伤评估带来了巨大的困难。本项目以申请人所开展的足尺预应力混凝土梁侧向撞击试验为基础，拟采用数值模拟与理论分析相结合的方法，考察车辆碰撞对桥梁动态响应的影响规律，探究车辆侧向撞击过程中桥梁的损伤破坏机理；随后，以梁体剩余抗弯承载力为判据建立桥梁侧向撞击下的损伤评估准则，基于精细化数值模拟分析，获取不同车辆质量、碰撞速度下梁体损伤程度的量化关系，并建立桥梁损伤分级评判标准；最后，基于数值模拟结果与数值拟合方法，绘制预应力混凝土梁不同撞击初始能作用下的破坏失效曲线，探究构件几何与构造参数对破坏失效曲线的影响规律，从而提出适用于预应力混凝土梁的损伤失效评定图法，实现车桥碰撞损伤评估。本项目研究结果将为超高车辆撞击桥梁上部结构损伤评估及防撞设计提供参考依据。

超高车辆撞击立交桥或跨线桥所引起的桥梁安全问题已成为现有桥梁设计与管理过程中需考虑的重要问题之一。本项目围绕车辆撞击桥梁上部结构损伤评估问题，开展了精细化有限元模拟，采用单一变量参数化分析方法，揭示了不同工况下预应力混凝土桥梁在超高车辆撞击下的动态响应和损伤破坏机理；对预应力混凝土桥梁在撞击作用下的损伤过程进行详细分析并计算了不同工况下的局部撞击力数值，结合各个工况下混凝土塑性损伤因子及结构整体的位移和变形来评估预应力混凝土桥梁在超高车辆撞击下的局部及整体损伤状况；为提出快速、全面的损伤评估体系，定义了基于剩余抗弯承载力的结构损伤指数，研究了不同车辆参数和桥梁参数对被撞击混凝土构件损伤破坏程度的影响规律，并建立了桥梁损伤分级评判标准；绘制出不同撞击初始能下的预应力混凝土构件的破坏失效曲线图，建立了预应力混凝土桥梁的损伤评估体系。本项目的研究可为超高车辆撞击下桥梁上部结构的损伤评估和防撞设计提供参考依据。