Platform-pile systems are typically used in bridge foundations and seaport structures. These systems are difficult to analyze using a conventional low-strain integrity test (LST) due to periodic oscillations. A staggered-grid finite-difference (SFD) method is proposed for a platform-pile system in soil and verified with ABAQUS and measured data. Different impact locations on the top surface of the platform and the lateral surface of the pile are analyzed, and parallel velocities are obtained at different locations. Choosing an appropriate impact location reduces the influence of the periodic oscillation signal; the impact locations at the center of symmetry are the best choices. At the same impact energy, the impact location should not be outside the cross section of the pile when the impact occurs on the top surface of the platform to achieve a meaningful damage signal. When the impact locations are on the lateral surface of the pile, the interferences are relatively small, and the damage vibration signal can be detected. The material and size of the hammer determine the impact duration and should be chosen to reduce the high-frequency influences and obtain reasonable data for analysis.
Appropriate impact and sensor locations must be chosen in pile integrity tests to prevent three-dimensional effects caused by the torsional and flexural modes. The three-dimensional characteristics cause high-frequency interference, especially in bridge and wharf piles. A method is required to minimize the high-frequency interference without reducing the accuracy of the pile integrity test. A multivelocity integrity test method is proposed based on a sensor array and frequency-wavenumber (FK) domain analysis to eliminate high-frequency interference and reduce the errors in the output of integrity tests of platform-pile systems. FK filtering is performed to eliminate the spatial alias frequency and separate the upward and downward wavefield and the vibration modes in an integrity test of a platform-pile system. The optimum sensor location to minimize the influence of interference signals is at the bending plane relative to the impact location. Using a sensor array reduces the influence of the sensor location on the test results and minimizes the requirements for determining the location of the excitation point and sensors in the traditional low-strain integrity testing (LST) method, thereby improving the applicability of this method.
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