Assessing the Ultimate bearing capacity of the composite shell annular foundation in cohesionless soil

The foundation shape effects on the stress distribution induced in the soil. Moreover, it has influence on the failure mechanism of the soil. For these reasons, it plays an important role in the ultimate load capacity of the foundation. Due to lack of materials, the new design methods attempts to utilize the least amount of material and achieve the maximum efficiency. If shell elements are employed in foundations, and the interaction effects are considered, their required cost can be reduced. This paper aims to compare the performance of the composite annular shell foundation with that of the annular one. For this purpose, the ultimate load capacity and the settlement of these foundations are experimentally modeled for various shell angles. Findings prove that the ultimate load capacity of the composite foundations are more than that of the annular one. Furthermore, it is observed that increasing the shell angle reduces the ultimate load capacity. Moreover, the shell efficiency factor is decreased by increasing the soil relative density. This phenomenon shows that the shells perform more appropriately in low-density soils. Additionally, a novel relation is proposed for predicting the ultimate load capacity of the composite shell. It is worth emphasizing that adding the edge beam to composite foundations improve its performance in settlements during failure. Moreover, the efficiency of foundations with edge beams is more than the ones without beam in soils with any density. Hence, usage of shells in annular foundation enhance its ultimate load capacity.