Development of dissipative embedded columns base connections for mitigating column axial shortening

This paper proposes an innovative design concept for embedded column base (ECB) connections featuring wide flange steel columns. The developed ECB connection achieves a non-degrading hysteretic response up to lateral drift demands associated with low probability of occurrence earthquakes. Column residual axial shortening due to local buckling is also minimized. 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 behaviour of the steel column from that of the RC foundation through the use of a debonding material layer wrapped around the embedded column portion. 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 testing as well as complementary finite element simulations. Both experiments and simulations demonstrate that the proposed 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.