跨海大桥主墩桩基钢护筒腐蚀损伤识别

跨海大桥主墩桩基施工过程中采用的钢护筒被保留作为桩基的外层,容易受到海洋环境的腐蚀破坏。提出一种基于插值曲率模态指纹库比对的桩基损伤识别方法,为解决测试数据不完备的问题,采用三次样条函数几何插值得到扩展后的桩基振型,然后在扩展振型的基础上采用中心差分计算得到曲率模态指标。以金塘大桥为工程背景,建立索塔-基础多尺度有限元模型,考虑海水腐蚀造成桩基钢护筒局部损失情况,以损失减薄区域的位置、轴向长度、深度为损伤参数,设置多种损伤工况样本,计算并建立基于插值曲率模态的桩基损伤识别指纹库,最后通过指纹库以外损伤工况与库内样本比对的方式,验证损伤识别效果。研究表明,为保证三次样条函数几何插值得到扩展振型对真实振型的拟合精度,至少需要沿桩基均布6个位移插值点。通过指纹库比对,能够准确识别桩基钢护筒减薄区域的位置与轴向长度。

Damage Identification for Corroded Steel Pile Casing of the Cross-ocean Bridge

Although numerous damage identification methods have been proposed and applied to detect stiffness degradation location in superstructures of bridge, damages on bridge substructures are seldom covered. A damage identification approach based on fingerprint match for database of vibration curvature mode indicators is proposed to identify corrosion in pile steel casing of the cross ocean bridge. Marine environment may easily corrode the steel pipe and causes the peeling of pile surface. Refined multi-scale FE models were developed to simulate the damage of the towel base of Jintang Bridge in China. The damage location, axial damage length and damage depth of the corroded zone on the steel casing were extracted. Cubic-spline interpolation and central difference method were adopted to obtain the pile vibration curvature modes in all damage cases for a small number of displacement points. The corresponding damage identification fingerprint database was then established. Numerical experiments indicate that at least six interpolated points are necessary to obtain the accurate pile vibration mode, which is the base for deriving the curvature mode indicator. The location and axial length of the corroded zone in the steel pile casing can be accurately determined by matching the indicator database with a damage-unknown case.