Novel weak form quadrature elements for second strain gradient Euler-Bernoulli beam theory

Abstract: Two novel version of weak form quadrature elements are proposed based on Lagrange and Hermite interpolations, respectively, for a sec- ond strain gradient Euler-Bernoulli beam theory. The second strain gradient theory is governed by eighth order partial differential equa- tion with displacement, slope, curvature and triple derivative of dis- placement as degrees of freedom. A simple and efficient differential quadrature frame work is proposed herein to implement these classi- cal and non-classical degrees of freedom. A novel procedure to com- pute the modified weighting coefficient matrices for the beam element is presented. The proposed elements have displacement as the only degree of freedom in the element domain and displacement, slope, cur- vature and triple derivative of displacement at the boundaries. The Gauss-Lobatto-Legender quadrature points are assumed as element nodes and also used for numerical integration of the element matrices. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed beam element.