This paper proposes a simplified I-D numerical model to simulate the distortion of a thin-walled tubular pile during installation. The most common deformation modes have been found by using modal analysis, and incorporated into a 1-D finite element model. To establish the accuracy of the simplified model of the distorted pile, free-standing piles with open ends and initial imperfection are considered here. Comparison with 3-D finite element analysis shows that numerical analysis using the newly developed 1-D model can accurately predict the response of a thin-walled pile under both static and dynamic loading.
During the installation of thin-walled tubular piles with open ends, the cross-section of the cylinder sometimes becomes distorted. One of the common lateral deformation forms is that the pile becomes elliptical at the tip. The ellipticity produces additional soil pressure on the pile. Further driving then increases the distortion of the cross-section. Eventually, the pile tip becomes completely closed. Recently, numerical studies of tubular pile driving analysis focused on the penetration of the pile, either with close ends (Simona, 1985; and Deeks, 1992), or with open ends (Smith et al., 1986; and Randolph, 1990; and Liyanapathirana, 1998). These tubular piles are all considered axi-symmetric. For piles with cross-sectional distortion as described above, the axi-symmetric condition can not be used. 3-D numerical analysis is currently the only way to simulate this behaviour, which is time consuming. To develop a simplified numerical model to simulate the behaviour of thin-walled tubular piles, Cai and Decks (1999) developed a new 1-D finite element model to simulate this behaviour under the assumption of bi-symmetry and no initial deformation.