Strengthening of Weak Story Moment Frames Using a Rocking System with Tendons

Abstract eng:
This paper proposes a rocking system to limit the residual deformation of moment-resisting frames in order to improve the immediate occupancy performance and reduce the rehabilitation cost. The system consists of a rocking column and a set of tendons to provide the existing frame with extra stiffness in the entire range of deformation, which provides the existing frame a re-centering capability and a limited level of residual deformation. In this study, a parametric study is conducted with a series of time-history analyses. The stiffness of the rocking column and the stiffness and position of the tendons are taken as the major parameters. It is observed that the rocking column, with a stiffness of about 1.0 times that of the weak story, and the tendons attached at the roof, with a stiffness of 0.05 times that of the weak story, are able to provide the optimal performance with a maximum residual story drift angle of 0.5%, the practical tolerance for occupancy. In the implemented substructure online hybrid test, the existing frame is to be simulated numerically and the rocking system tested physically. The experimental results show that the maximum residual story drift angle never exceeds 0.5%, demonstrating the feasibility of the proposed rocking system.

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