Abstract: A transient system is discussed in detail. The concept of equivalent tensile stiffness is introduced according to the result that the vertical load is proportional to the cubic of the dimensionless vertical displace- ment. The value of the equivalent tensile stiffness is exactly equal to the structural stiffness under the horizontal loads. Based on the finite deformation theory, the relation between the vertical load and displacement for asym- metric structures in the Lagrange coordinate system is given. The uniform relationship between the load and displacement can be obtained by ignoring the horizontal displacement.