Conventional concentrically-braced frame (CBF) systems have limited drift capacity before brace buckling and related damage leads to deterioration in strength and stiffness. Self-centering concentrically-braced frame (SC-CBF) systems have been developed with increased drift capacity prior to initiation of damage. SC-CBF systems are intended to minimize structural damage and residual drift under the design basis earthquake.
The behavior of SC-CBF system differs from that of a conventional CBF system in that the SC-CBF columns are designed to uplift from the foundation at a specified level of lateral loading, initiating a rigid-body rotation (rocking) of the frame. Vertically-oriented post-tensioning bars resist uplift and provide a restoring force to return the SC-CBF columns to the foundation (self-centering the system).
This thesis considers an SC-CBF configuration that includes two sets of columns: the SC-CBF columns, which uplift from the foundation, and the adjacent gravity columns, which do not uplift. Lateral-load bearings between the columns at each floor level transfer the inertia forces from the gravity columns (which are connected to the floor diaphragm) to the SC-CBF (which is not directly connected to the floor diaphragm). Friction at the lateral-load bearings increases the overturning moment capacity of the SC-CBF and dissipates energy under cyclic loading.
A parametric study of SC-CBFs with friction-based energy dissipation elements is presented in this thesis. Nonlinear static and dynamic analyses of SC-CBFs with different coefficients of friction at the lateral-load bearings are presented to illustrate the effect that changing the coefficient of friction has on the design, behavior, and dynamic response of SC-CBF systems.