基于层析成像的服役刚构桥接缝混凝土无损检测方法

Non-destructive Testing Method of Joint Concrete in Service Rigid Frame Bridge Based on Tomographic Image

大跨度连续刚构桥接缝工作状态会显著影响桥梁的纵向刚度分布,从而改变结构受力。目前,接缝部位混凝土尚缺少针对性的无损检测手段。为探明实际结构中接缝混凝土缺陷状况,基于走时分析的图像重建原理,建立了离散慢度模型,并使用代数重建算法(ART)求解,重建接缝内部缺陷图像,提出了针对接缝混凝土的超声无损检测方法。结合在役大跨度连续刚构桥上部结构拆除工程,针对实际工程场景设计了6层超声传感器布设方案,建立了6×8路径信息矩阵,通过ART算法求解,对接缝质量状况进行了无损检测,并与有损取芯结果进行了对比分析。实桥检测试验表明:提出的基于图像重建原理的大跨度连续刚构桥接缝质量超声检测方法具有较高准确性。结合桥梁上部结构拆除工程,在对桥梁接缝的49处有损取芯检测基础上,初步建立了基于声时值的接缝混凝土内部缺陷评价标准。

The working condition of joints in long-span continuous rigid frame bridges has a significant impact on the longitudinal stiffness distribution of the bridge,which in turn changes the structural loadbearing behavior.At present,there was a lack of targeted nondestructive testing methods for concrete at joints.A novel approach by developing a discrete slowness model that leverages the principles of travel time analysis and image reconstruction was introduced.The algebraic reconstruction algorithm(ART)was utilized to solve for the reconstruction of the internal defect image of the expansion joint.In conjunction with the dismantling of the upper structure of an operational long-span continuous rigid frame bridge,a six-layer ultrasonic sensor configuration appropriate for the engineering context was designed.A 6×8 path information matrix is established,and the ART algorithm is employed to non-destructive test the quality of the expansion joint concrete.The efficacy of this method is validated through comparative analysis with results from destructive core sampling.Field tests conducted on the bridge corroborate the high precision of the proposed ultrasonic non-destructive testing method,based on image reconstruction principles,for evaluating the integrity of expansion joints in long-span continuous rigid frame bridges.Further,drawing from the destructive core sampling of 49 locations of the bridge joints,a preliminary standard for assessing the internal defects in joint concrete predicated on acoustic travel time values is proposed.