INVESTIGATION OF CYCLIC BEHAVIOR OF FULL-SCALE TREE-LIKE HOLLOW STRUCTURAL SECTION COLUMNS WITH INFILLED CONCRETE

The cyclic behavior of tree-like hollow structural section (HSS) columns with infilled concrete was experimentally and numerically investigated. A full-scale column, with the height of 3.2 m and the treetop plan dimension of 4 m×3 m, was designed and manufactured according to a practical engineering prototype. The column with a capacity protected reinforced concrete foundation was tested under combined constant axial compression and cyclic lateral loading through a specifically designed setup. The cracking and spalling of the reinforced concrete foundation were observed initially, followed by yielding of the bottom end of the primary branches when the story drift ratio reached 1.00%. The specimen failed by fracture of the full penetration groove welded splices in the petal-shaped trunk embedded in the foundation when the story drift ratio reached 3.00%. A detailed finite element analysis model for the tree-like column was then established and verified. Parametric studies were conducted to investigate the influence of the axial load level, filling range of concrete, steel yield strength, and the height to width ratio of the petal-shaped trunk. Finally, some design considerations were proposed.