Experimental and analytical study on stiffened steel segment of hybrid structure

• Ultimate capacity and buckling mode of stiffened steel segments has been experimentally investigated.
• 3D FE models of stiffened steel segments considering initial imperfections and residual stress were established and verified.
• Theoretical analysis based on the principle of stationary potential energy was carried out.

Hybrid structures which innovatively and reasonably combine two different materials in longitudinal direction have been applied world-widely, such as hybrid girder, hybrid pylon and hybrid arch skewback. The hybrid structure segment generally consists of steel stiffened segment, concrete strengthened segment and hybrid joint. In order to investigate ultimate capacity and buckling mode of steel stiffened segment in hybrid structure, model tests on five different specimens have been carried out. The test results indicated that embedded T-reinforcing stiffeners had the best axial stiffness, while the out-plane stiffness, ultimate capacity and local stress concentration of circumscribed π-reinforcing stiffeners were best among the three traditional reinforcing stiffeners. Besides, the methods of extending reinforcing stiffener web and adding diaphragms on the end of reinforcing stiffeners not only obviously improved both axial and out-plane stiffness but also increased ultimate capacity and reduced local stress concentration. Five three-dimensional finite element (FE) models of steel stiffened segments considering initial imperfections and residual stress were established. Theoretical analysis based on the principle of stationary potential energy was carried out. The reduced parameters based on FE analysis results were consistent with those from tests and theoretical analysis and tended to be conservative at a safety level. The presented overall investigation may provide reference for the design and construction of stiffened steel segment in hybrid structure.