Question

In 3D truss, formula for direct cosine l = _____

(a) x2-x1

(b) \(\frac{x_2}{l_e}\)

(c) \(\frac{x_1}{l_e}\)

(d) \(\frac{x_2-x_1}{l_e}\)

I got this question in an online interview.

This question is from Three Dimensional Trusses topic in section Trusses of Finite Element Method

Answer 1

Right option is (d) \(\frac{x_2-x_1}{l_e}\)

Explanation: A truss is a two node element which allows arbitrary orientation in XYZ co-ordinate system. The 3D truss element can be treated as straight forward generalization of the 2D truss element.