水平冲击作用下非新建桥梁桩基动力响应及损伤特性

Dynamic Response and Damage Characteristics of Non-newly-built Bridge Pile Foundation Under Horizontal Impact

涉水桥梁在建成服役过程中不可避免产生病害,同时船舶撞击下的桥梁下部结构极易受损,继而引发安全事故。为研究船撞作用下非新建桥梁桩基的动力响应与损伤特性,对陕西省汉江一桥96根涉水桩基病害进行了潜水探查,明确了非新建桥梁桩基的病害情况,建立了基于层次分析法的非新建桥梁桩基病害评价体系,将评价结果与现场探查分析结果进行了对比;制作了新建、病害与病害加固3类单桩试件,使用自制摆锤冲击装置对3类单桩试件进行了水平冲击试验,对比分析了3类单桩试件在同一水平冲击荷载下的冲击力、混凝土应变、位移、加速度的动力响应特性及桩身损伤。研究结果表明:建立的非新建桥梁桩基病害评价体系可有效反映汉江一桥服役状态,结构完整度较高且使用功能正常;单桩的冲击过程可分为峰值冲击、系统分离与次生冲击3个阶段;桩周土楔的形成与发展使得桩周土横向土抗力降低,进而影响桩基抗冲击能力;仅对病害桩基的地面露出段加固处理,对降低病害桩基在承受水平冲击荷载的破坏影响程度有限,加固效果不显著。研究成果可为涉水非新建桥梁防撞设计与施工提供参考。

Bridges crossing water bodies inevitably suffer from damage or defects during service,and the substructure of the bridge is easily damaged by ship impacts,which can lead to safety accidents.To study the dynamic response and damage characteristics of non-newly-built bridge pile foundations under ship collision,a diving exploration of 96 pile foundations of the Han River Bridge in Shaanxi Province was conducted,based on which the damage level of the non-newlybuilt bridge pile foundations was clarified.The analytic hierarchy process was used to establish a system for evaluating the pile foundation defects of the Han River Bridge,and the evaluation results were compared with the analysis results of on-site exploration.Three types of single pile specimens(new,diseased,and diseased reinforcement)were prepared.A custom-built pendulum impact device was used to conduct horizontal impact tests on three types of single pile specimens,and the dynamic response characteristics of the impact force,concrete strain,displacement,acceleration,and pile damage of the three types of single pile specimens under the same horizontal impact load were compared and analyzed.The results indicate that the established non-newlybuilt bridge pile foundation damage evaluation system can effectively identify the service status of the Han River Bridge with high structural integrity and normal functional use.The impact process of a single pile can be divided into three stages:peak impact,system separation,and secondary impact.The formation and development of soil wedges around piles reduce the lateral soil resistance,which in turn affects the impact resistance of pile foundations.Only the reinforcement of the exposed ground section of the diseased pile foundation has a limited impact on reducing the damage caused to the pile foundation under horizontal impact loads,and the reinforcement effect is not significant.The findings of the study can provide a reference for the design and construction of collision prevention structures for non-newly-built bridges crossing water bodies.