Abstract: According to the Classical Lamination Theory, this paper deduced the effective flexural rigidity of cap-beam with the relationship between the internal force and strain when the beam are under the pure bending state. Then, the effective flexural rigidity was used to deduce the axial critical load and the natural frequency of this beam. Finally, the finite element method was used to verify the formula, providing a reference for the application of the cap-type and other section types of composite beam in engineering.

Key words: cap-beam, effective flexural rigidity, axial critical load, natural frequency