The theory of nonlinear behavior of biaxially loaded short and slender composite columns is used to study the load-deformation and moment-curvature of four pin-ended composite column specimens tested under axial compressive load and biaxial bending moments in a single curvature. The accuracy of the test results is verified by comparison with analytical results obtained by a method of analysis that includes the nonlinear material properties of concrete and steel and covers the ascending and descending branches of the linear segmented column specimen. A computational method is presented to model the analytical behavior of the biaxially loaded composite column. Its validity is verified by the comparisons with other analytical methods, and the results of experimental tests from four different authors.

A generalized interaction equation for the analysis and design of composite columns is presented. Its validity is verified by comparing the results of existing design examples and some test results with the results obtained from the equation.

A comparative review of the available design methods currently being used in the United States is presented. Their major differences, compatibilities and inconsistences are highlighted and discussed.

Finally some design recommendations are proposed for the analysis and design of biaxially loaded concrete-encased composite columns.