Local buckling behaviour of pultruded FRP composite sheet piles subjected to uniform pressure

The buckling behaviour of fibre reinforced polymer (FRP) sheet pile panels subjected to a uniform lateral pressure was investigated. Based on the previous full scale tests by Shanmugan in year 2003 (Shanmugan, 2004), the critical load at buckling initiation was first determined through experimental data analysis, and the theoretical modeling was then followed in an attempt to predict the buckling initiation and understanding the failure mechanism. The behavior of the panels loaded in upright position and inverted position was studied.; The local buckling of the compressive flanges was monitored by the strain measurements, which demonstrated that when tested in upright position, the panel failed immediately after local buckling of compressive flange, and when tested in inverted position, the panels could be able to carry the load into post buckling region. The stresses and corresponding axial forces at buckling were calculated by the classical beam flexure formula but taking into consideration the reduction of flexure rigidity and neutral axis shifting. The axial force calculated from the beam flexure formula was comparable with that from stain gauge measurements. The axial force was not uniformly distributed along the width of the compressive flange at upright position and was about zero at the free edge. When tested in inverted position, the neutral axis distance and the flexure rigidity kept almost as a constant. The sheet pile panels were with a uniform axial force along the width of the compressive flange.; An analytical modeling was performed to predict the buckling initiation. The buckling of the panel was simplified as the buckling of the compressive flange with various boundary conditions. The differential equation of the compressive flange was established based on the assumption that the flange was subjected to an in-plane axial force and an out-of-plane lateral pressure simultaneously. It was found that the lateral pressure did not have direct effect on the critical load. It was the compressive axial force that determined the local buckling of the flange. Kollar's explicit expressions were also applied but only valid for long plate loaded by uniform axial force.; The buckling load obtained by solving the differential equation for the inverted panel compared well with that from the experimental results. However, for the flange in a pile at an upright position, the theoretical prediction was far less than the experimental value which might be attributed to the non uniform axial force on the flange. Energy method was applied to estimate the range of the buckling load of a plate loaded by a linearly distributed axial force. The upper bound value was obtained from fixed boundary condition and the lower bound from simply supported assumption. The experimental result was found in between the two bounds and was in favour of the lower bound as a conservative estimation of critical load for upright panel.