A numerical model for column to foundation joint with un-bonded high strength steel bars in grouted sleeves

The present work deals with the experimental and numerical results of an innovative column to foundation connection for precast concrete elements. The joint is characterized by the use of high strength steel threaded bars in grouted sleeves to allow the bending moment to be transferred from the column to the foundation. The connecting bars are wrapped with plastic duct to allow the system to develop the lateral displacement capacity required during the seismic event. Furthermore, the un-bonded length is able to reduce the strain rate in the bar which can cause the premature fatigue failure of the steel bars. The work aims at developing a simple fem model to describe the cyclic behavior of a precast column connected to a cast in situ foundation by means the tested joint, by setting the non-linear behavior of the assembly in a non-linear spring at the base of the joint. The model accurately approximates the specimen experimental behavior.