Determination of optimal padeye position of modified suction caissons in the sand under monotonic inclined loading

Modified suction caissons (MSCs) acting as floating platform foundations will be subjected to inclined loading induced by wind waves and currents, thus, it is of significance to investigate its inclined bearing capacity. Model tests and numerical simulations were conducted on the MSCs embedded in the sand to study the monotonic inclined bearing behavior. Test results show that the inclined capacity firstly increases, and then, decreases as the padeye position moves downward along the caisson wall. The optimum padeye position corresponding to maximum inclined bearing capacity locates at the 0.5 times the internal compartment length below the lid when the loading angle equals 20 degrees. The contribution of passive suction to the capacity may be ignorable when the loading angle is relatively small, and the passive earth pressure is predominant. It was also found that the increase of the external structure length can improve the inclined bearing capacity compared with the increase of external structure width. The relationship between the ultimate bearing capacity and the padeye position follows a Gaussian function. Considering the external structure dimensions, loading angle, and padeye position, a normalized formula is proposed to determine the ultimate bearing capacity. Finally, the optimal padeye position will be found for the floating platform.