Structural design in the post-effective length era

Before the publication of several new codes for structural design of steel structures in recent years, design of structures is based on the linear analysis and the effective length method, which relies on a nonexistent or erroneous assumption of buckling at undeformed geometry. After the publication of the several codes including the Eurocode-3 (2005), LRFD (2005) and the Hong Kong Steel Code (2005), interestingly all in 2005, a new method based on the equilibrium at deformed configuration emerges as a replacement of the old effective length method. In theory, the second-order and advanced analysis can be used for any structural forms but calibration for imperfections against coded and experimental results is essential for safety. Its application to various structural forms and materials has been successful with advantages of this new method manifested. This paper summaries the new design method on two structural forms as transmission line towers and steel, concrete and composite portal frames.