Dissipative Embedded Column Bases for Enhanced Seismic Performance of Steel Moment Resisting Frames

This paper presents an innovative design concept for embedded column base (ECB) connections. The developed ECB connection achieves a non-degrading hysteretic response. In the proposed ECB connections, the dissipative zone is shifted into the embedded portion of the steel column inside the reinforced concrete (RC) foundation. This is achieved by lowering the flexural strength of the embedded column portion by reducing the column flange width, by keeping the RC foundation elastic, and by decoupling the flexural behavior of the steel column from that of the RC foundation. A debonding material layer that is wrapped around the embedded column portion is used for this purpose. Nonlinear geometric instabilities of the embedded column portion are prevented because of the surrounding concrete, which realizes a stable energy dissipation mechanism. The proposed concept is validated through large-scale quasi static cyclic testing as well as complementary finite element simulations. These demonstrate that the dissipative ECB connections behave as intended. More specifically, the proposed dissipative ECB connections do not experience flexural strength deterioration of the connection up at least to 4 % rads and they minimize column axial shortening.