摘要:
现代社会中,城市桥梁时常面临意外爆炸和恐怖袭击等带来的爆炸威胁,目前针对桥梁在爆炸荷载下的响应研究尚不充分,尤其是远距离爆炸荷载。为探究远距离爆炸荷载作用下城市连续梁桥的动力响应和破坏机理,首先采用LS-DYNA建立了远距离爆炸荷载加载方法和流固耦合数值计算方法。基于典型连续梁桥结构,建立精细化数值计算模型,分析了不同爆炸场景下桥梁的响应过程和典型破坏模式,并进一步研究了爆炸距离、爆炸当量、冲击角度对结构响应和破坏的影响。结果表明:连续梁桥在响应过程中呈现出上部结构抬升、下部结构弯曲和桥墩整体倾斜等特征,冲击波流场演化引起的结构前后表面压差以及桥梁的连续特性是影响响应过程的关键因素;远距离爆炸下,连续梁桥发生湿接头破坏、墩柱贯穿式破坏和盖梁弯曲破坏等典型破坏模式;随着冲击角度和比例距离增大,将导致上部结构抬升量减小、桥墩倾斜程度下降,并且抬升与倾斜响应对比例距离的变化更加敏感。本文研究可为桥梁结构爆炸响应分析和抗爆设计提供有价值的分析方法和机理参考。
Abstract:
In modern society, urban bridges often encounter blast threats caused by accidents and terrorist attacks. Moreover, the research on the response of bridges under blast loads is insufficient, especially for far-field blast loads. To investigate the dynamic response and failure mechanisms of urban continuous beam bridges under far-field blast loads, this study established a method for simulating far-field blast loading and a fluid-structure interaction method implemented using the LS-DYNA explicit dynamics code. Subsequently, the refined numerical model of a typical continuous beam bridge was set up to analyze the response processes and typical failure modes under different blast scenarios. Further studies were conducted on the effects of stand-off distance, charge weight and impact angle on structural responses and failures. The computational results explicitly show that continuous beam bridges exhibit a unique set of characteristic deformation features throughout the dynamic responses, including superstructure uplift, substructure bending, and piers tilt. The pressure differential caused by the evolution of blast waves at the front and back surfaces of the bridge, combined with the integrality of the bridge structure, are the key factors influencing the dynamic response process. Under far-field blast, continuous beam bridges typically appear wet-connectors shear failure, piers penetrating damage, and bent caps bending failure. Parametric analyses revealed that both the magnitude of superstructure uplift displacement and the degree of pier tilt undergo a significant decrease as the blast impact angle and scaled distance progressively increase. Moreover, for scaled distance and impact angle, the bridge structural response (the superstructure uplift and pier tilt) is more sensitive to variations scaled distance. The research obtained the response and failure results of continuous beam bridges under far-field blast loads with different blast quantity, blast distances and impact angles. This study provides valuable analytical methods and failure mechanism references for blast response analysis of bridge structure and anti-blast design.