Experimental Study of Dry Joints with Castellated Keys Subjected to Combined Axial, Bending and Shear Forces

Abstract

[EN] The design and execution of the connection between precast concrete segmental elements are critically important since these connections are a discontinuity region whose structural capacity is fundamental for transmitting normal and shear stresses through the joint. The use of dry joints with castellated keys is the most widespread solution used in the construction of fast precast elements. The experimental dry joint programs performed to date have focused on the behavior under direct shear at different confining stress levels applied uniformly along the joint. Axial compression forces simulate the confinement effect between two different joint parts. Design formulations have generally been determined to evaluate the shear capacity of dry joints subjected to uniform confinement. Although the connections in concrete segmental elements are usually subjected to combined axial, bending and shear forces. This communication presents the results of an initial 6-test experimental program performed on conventional concrete dry joint specimens with three shear keys subjected to different eccentric forces and confining stress levels. For this, a test was designed for push-off dry joint specimens subjected to these combined forces, in which it was possible to apply an axial compression force with different eccentric forces to subject the joint to a compression force applied at the central point (uniform confinement throughout the joint) or eccentric compression force, to vary the compression depth (no uniform confinement) and tension zones. This test enabled the analysis of the effect of eccentric compression forces on the joint¿s shear capacity and verified the safety of the existing formulations. The AASHTO (2003) formula was also analyzed to evaluate shear capacity for dry joints subjected to these combined forces.