This paper is about second-order elastic analysis of sway frame and how linear stiffness ratio of the beam and the column affects second-order internal force.

At the same time, by changing the linear stiffness ratio of the beam and the column to analyse how it affects the second-order internal force.

This paper makes a deep-going study of several key technical issues,such as the rationality of the limit values of longitudinal linear rigidity of bridge piers and the load combinations of longitudinal forces of jointless tracks used on bridge deck.

The mutual relation between the linear stiffness and the bending moment of the fixed end and the slope of the pivoted end could be ascertained based on the straight cantilever beam,and the reduction linear stiffness of the curved beam could be ascertained via this relation.

The secant stiffnesseses of frames and anti-earthquate walls at different deformation stages are determined from experimental data.

frames and aseismic walls models, hence, the secant stiffness of frames and aseismic walls at different deformation stages are determined, the composition of lateral displacements of R.

An element tangent stiffness equation was derived based on the secant stiffness equation of stability function elements with shear deformation effects considered.