A Study on Integrity Testing for Platform-Pile Systems considering Wave Propagation

Abstract

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.

Integrity Testing of a Platform‐Pile System Using a Sensor Array and Wavenumber Domain Analysis

“…In the traditional LST method, the optimal distance between the striking point and the receiver is 0.5R-0.7 R when the impact location is on the top surface of the pile [12][13][14]. When two receivers are used, the impact location should be on the top surface of the pile cap, and the sensors should be placed on the bending plane relative to the impact location [46,51]. Figure 17 bending plane relative to the impact location, and two vibration modes occur at sensor A i .…”

“…It is assumed in the computational model that the pilesoil system consists of linear elastic materials during LST. We use the (2M)th-order finite-difference scheme to calculate the temporal derivatives of the velocity and stress components and calculate the spatial derivatives with fourth-order staggered finite-difference (SFD) schemes to improve the accuracy [45,46]. e heterogeneous finitedifference scheme is implemented following Moczo et al (2002) [47].…”

“…Zero stress must be satisfied on the free-surface boundaries. e stress imaging technique is used for the free-surface treatments [46,48].…”