In this paper, a computational approach using a combination of the upper bound theorem and the bubble-enhanced quadrilateral finite element (FEM-Qi6) is proposed to evaluate bearing capacity factors of strip footing in cohesive-frictional soil. The new element is built based on the quadrilateral element (Q4) by adding a pair of internal nodes to solve the volumetric locking phenomenon. In the upper bound finite element limit analysis, the soil behaviour is described as a perfectly plastic material and obeys associated plastic flow rule following the Mohr-Coulomb failure criterion. The discrete limit analysis problem can be formulated in the form of the well-known second-order cone programming to utilize the interior-point method efficiently. The bearing capacity factors of strip footing and failure mechanisms in both rough and smooth interfaces are obtained directly from solving the optimization problems and presented in design tables and charts for engineers to use. To demonstrate the accuracy of the proposed method, the results of bearing capacity factors using FEM-Qi6 were compared with those available in the literature.
Keywords:
limit analysis; bearing capacity factors; strip footing; SOCP; FEM-Qi6.
A bubble-enhanced quadrilateral finite element for estimation bearing capacity factors of strip footing
