Self variable stiffness system for optimal seismic response of RC frame with concrete braces

The purpose of this paper is the study of RC fully braced frame showing that its concrete braces change the stiffness of the frame and provide its optimal seismic response. The frame itself controls its behavior, attenuating the seismic response through autonomous disengagement of its concrete braces in tension. The advantage of the physical non-linearity of the brace material (concrete) in compression is also taken into account. Additionally the influence of the vertical static loading is studied. The system has several levels of seismic control, which it selects for its optimal response to a given earthquake. All the above factors significantly reduce (over 50% as well be shown in paper) the seismic forces and dynamic displacements, and create an optimal scheme of the structure. A total of seven schemes of a six story braced frame were analyzed numerically from full bracing through unbraced frame. One of these schemes is optimal to the given earthquake. It can be concluded that the proposed bracing system adopts the optimal state of the RC frame. As a result maximum energy dissipation can be achieved and the seismic forces can be reduced significantly. The main difference between the proposed system and existing ones is that it arrives at the optimal state by itself, without external energy input.