Effect of Grouting in Jacket Type Offshore Platforms Pile-Leg Interaction in Nonlinear Range of Deformation

The annulus between the pile and leg in jacket type offshore platforms may be filled with cement grout mainly to reduce horizontal deflections, inhibit corrosion, and increase the energy absorption capacity. This paper discusses an approach, which can be used to demonstrate an enhanced structural performance due to the both presence and lack of grouted piles. The compressive stress-strain response of the grout has been derived from the performed experiments. Having this response, the fiber beam column post-buckling element in the commercial code, DRAIN-3DX, was being used to investigate the behavior of grouted and ungrouted jackets and also the relative pile-leg interaction. It is therefore concluded that in the cases where the existing structure is ungrouted or incompletely grouted, adequate grouting can be considered as a relatively inexpensive method to improve the strength and performance of the structure. In fact, the cement filling of a tubular member increases its overall strength and also provides additional stability. The lateral force-deformation curves are equivalents for the cases where the axial force is less than 30% of the yielding force, $Pyielding$⁠. However, as the axial force increases, the grouted portal element gradually gives a much better performance compared to the ungrouted element. By increasing the axial force, the lateral hysteretic behavior deteriorates in both grouted and ungrouted cases; however, this deterioration is more severe in the case of an ungrouted portal element.