Applicability of low-yield-strength steel for ductility improvement of steel bridge piers

An experimental investigation on the use of low-yield-strength (LYS) steel to improve the ductility capacity of box-shaped steel bridge piers is presented in this paper. Five specimens in which the lowest cross section was fabricated with LYS steel plates were tested under cyclic lateral loads. Sectional configurations and the thickness of LYS steel plates of the specimens were taken as the main test variables. An additional specimen that does not have LYS steel plates was also tested as a benchmark specimen. The test results revealed that the specimens with stiffened LYS steel segment having proper thickness have greater ductility and energy absorption capacity. The stiffened specimens with much thinner plates are vulnerable to sudden brittle failure whereas those with much thicker plates are undesirable due to the excessive strength. The unstiffened specimens with thick LYS steel plates have enough strength but the ductility is not sufficient. In some cases, the increase in the member strength due to the great cyclic strain-hardening characteristic of LYS steel could be partly balanced by a local buckling deformation.