The load distribution and deformation of offshore piles in Incheon grand bridge are investigated, based on experimental tests and a numerical analysis. Special attention is given to the consideration of flexural rigidity in laterally loaded piles. Rigid- and flexible- pile analyses were conducted for comparison. A framework for determining the soil spring (p-y curves) is proposed from field and laboratory model tests. A numerical analysis that takes into account the proposed p-y curves was performed for major parameters on pile flexibility such as pile diameter, the length and the subgrade soil reaction. Based on the analysis, it is shown that there are significantly differences in bending moments and lateral displacements in flexible piles rather than rigid piles. Through the comparative studies, it is found that the p-y curves influences much more on the behavior of a flexible pile than of a rigid pile and thus the magnitude and distribution of the p-y curves highly influences on the pile behavior when the pile is designed as a flexible pile.