RC梁四点弯曲加载应力自漏磁信号检测试验

为了给桥梁结构的健康检测提供参考，将金属磁记忆检测技术引入到钢筋混凝土（RC）梁内部钢筋的应力检测当中，进行了钢筋混凝土T形截面梁四点弯曲加载应力自漏磁信号检测试验。利用基于金属磁记忆的三维扫描检测装置采集了试件在不同荷载下的自漏磁信号，并对不同提离高度和多条扫描路径下的磁信号进行分析，得到了钢筋混凝土T形截面梁在不同应力状态下的空间信号规律，提出了利用“法向漏磁场方均根值”来定量计算RC梁纯弯段处钢筋应力的方法。研究结果表明：在钢筋混凝土T形截面梁纯弯段内，钢筋内部应力与“法向漏磁场方均根值”呈线性关系，且函数的拟合优度R²达到0.988 4，拟合值与实测值之间误差微小；随着提离高度的增加，钢筋混凝土T形截面梁在不同荷载下的自漏磁信号曲线逐渐上移，自漏磁信号的分布规律没有显著变化，“法向漏磁场方均根值”与RC梁内部钢筋的应力在纯弯段内仍满足线性关系，试件在不同提离高度下的R²达到0.965；随着扫描路径的改变，钢筋混凝土T形截面梁在不同荷载下的自漏磁信号曲线呈现出相似的规律，且“法向漏磁场方均根值”与RC梁内部钢筋的应力在多条扫描路径上均满足线性变化的关系，在各条扫描路径下R²的平均值为0.959。所提方法可为RC梁内部钢筋应力的无损检测提供新的思路与参考。

Stress Self-leakage Signal Detection Test of RC Beam Under Four-point Bending

To provide a reference for the health detection of bridge structures, metal magnetic memory detection technology was introduced into the stress detection of steel bars inside reinforced concrete (RC) beams, and a four-point bending load stress self-magnetic leakage signal detection test of a reinforced concrete T-shaped cross-section beam was performed. A three-dimensional scanning detection device based on metal magnetic memory was used to collect the magnetic flux leakage signals of the reinforced concrete T-shaped cross-section beams under different loads, the magnetic signals under different lift-off heights and multiple scanning paths were analyzed. Based on the spatial signal law under different stress states, the use of the "root mean square value of the normal leakage magnetic field" was proposed to quantitatively calculate the stress of the steel bar at the pure bending section of the RC beam. The research results show that in the pure bending section of the reinforced concrete T-shaped cross-section beam, the internal stress of the steel bar and the "root mean square value of the normal leakage magnetic field" present a linear relationship, and the goodness of fit of the function R² reaches 0.9884, which is between the fitted value and the measured value. The error obtained was insignificant. Furthermore, with the increase of the lift-off height, the self-leakage signal curve of the reinforced concrete T-section beam under different loads gradually shifts up, and the distribution of the self-leakage signal does not change significantly. The "root mean square value of the normal leakage magnetic field" and the stress of the steel bar inside the RC beam still satisfy a linear relationship in the pure bending section, and the R² of the specimen under different lift-off heights reached 0.965. With the change of the scanning path, the self-leakage signal curves of reinforced concrete T-shaped cross-section beam under different loads show similar results; the "root mean square value of the normal leakage magnetic field" and the stress of the steel bars inside the RC beam satisfy the linear change relationship on multiple scanning paths. The average value of R² for each scanning path was 0.959. This method represents a novel approach for nondestructive testing of the stress of the rebar inside an RC beam.