Interface shear transfer of precast concrete dry joints in segmental columns

Precast dry joints in segmental columns are important to ensure the structural integrity and continuous to transfer both shear and flexural forces. Though dry joints have the concern of durability problems, they are the trend for convenience in site construction and less climate influenced. Ten precast column joint specimens were fabricated and tested under direct shear loading. The failure patterns of solid section keyed specimens were shearing off of male shear keys and diagonal cracks in female shear keys. The failure sequence was from top to lower shear keys. But the failure pattern of hollow section specimens was flexural failure of upper male or lower female shear keys, shearing off of vertical shear keys, and diagonal cracks in vertical female shear keys. The shear force-relative slippage relations of specimens exhibited two or three stages. Higher confinement stress, solid section (or enough key cover concrete thickness), and enough number of keys were essential to maintain high shear strength and ductile responses. Two formulation methods of shear strength prediction formula were deduced. One is based on the failure envelope of uniaxial compression and tension strength of concrete, the other one is based on tension strength Mohr circle only. The proposed formula has comparable prediction precision for the joint shear test database. Shear key shear stress and shear strength contribution were analyzed with the test data. The specimen shear stress transfer and distribution were qualitatively investigated with a two dimensional FE model.