桥面预应力钢索病害GPR正演及应用

Forward Modeling and Application of GPR for Bridge Deck Prestressed Tendon Disease

为预防桥梁老化导致的灾害,采用探地雷达对其可能存在的病害进行快速、全面、定期体检测,是一种有效且低成本的方法。基于时域有限差分法,建立了探地雷达桥面二维正演模型,讨论了桥面上部不同规格钢筋网对下部预应力钢索雷达信号响应的影响,研究分析了在上部钢筋网的影响下,预应力钢索周围存在空洞及裂缝病害的雷达信号特征,并比较了完好钢索与缺陷钢索中心处的单道雷达波形的特征。结果表明:上部钢筋网间隔越小,产生的绕射干扰作用对下部钢索位置的确定及缺陷的雷达响应影响越大;空洞缺陷的存在会使预应力钢索雷达响应的双曲线弧顶位置有所上升,而破碎层及裂缝缺陷会使预应力钢索雷达响应的双曲线弧顶位置有所下降;实践应用表明探地雷达能很好对单层钢筋网桥面下的钢索进行定位,但是对于钢筋锈蚀、混凝土炭化等病害的检测还有待进一步研究。

In order to prevent the disasters caused by aging bridges,it is an effective and economical method to use ground penetrating radar to detect the potential problems.Through using the finite-difference time-domain method of GPR Max 2D simulation software to analyze the data gathered by ground penetrating radar,two-dimensional forward model of the bridge deck is established.The influence of different specifications of mesh reinforcement on the radar signal response of the lower prestressing cable is discussed.The author analyzed the signal characteristics of the lower prestressing cable which surrounded by voids and cracks under the influence of reinforcing mesh in upper deck.The author compared the single-channel radar waveforms of defective prestressing cable and normal prestressing cable.The results show that the smaller the spacing of the upper steel mesh,the greater the influence of the resulting diffraction interference on the determination of the position of the lower cable and the radar response of the defect.The existence of void defects will increase the hyperbolic arc top position of the prestressed steel cable radar response,while the broken layer and crack defects will reduce the hyperbolic arc top position of the prestressed steel cable radar response.Practical application shows that the ground penetrating radar can well locate the steel cables under the single-layer steel mesh bridge deck,but the detection of steel corrosion,concrete carbonization and other diseases needs further research.