Base CONNECTION TYPE

1.     CONNECTION TYPE

Column base connections can be classified into three general types :– deeply embedded, shallowly embedded and exposed.

Deeply embedded type base connections  are constructed by directly embedding the column into a reinforced concrete foundation and, if desired, attaching it to a grade beam. The significance of the base plate and anchor rod components depend on the embedment depth. For columns with very deep embedment lengths, moments and forces are resisted mostly by bearing of the column against the concrete. With proper concrete detailing, embedded type configurations can provide a high flexural stiffness end condition (i.e. assumed as ideally fixed) and the full plastic flexural capacity of the column can easily be obtained .( Nakashima & Igarashi (1986) indicates that, for deep embedment lengths, the presence of anchor rods or base plates has little effect on the moment-rotation response of the connection. In addition, it was determined that a plastic hinge in the steel column may be developed even without the use of concrete reinforcement.

Shallowly embedded connections  are typically installed in a small pocket within the concrete foundation and later covered with plain concrete or grout. The small amount of plain concrete or grout cover may not contribute much to strength and stiffness of the connection for axial tension or flexural loading. However, the strength and stiffness in shear may be significantly high due to bearing between the base plate and concrete/grout pocket. Steel reinforcing bars may be placed over the base plate to develop additional strength and stiffness . the initial flexural stiffness and maximum strength of the connection may be significantly greater than similar exposed column base types Cui et al. (2009).