This paper describes an integrated experimental and analytical research program on the development of a new type of friction damper for unbonded post-tensioned precast concrete building moment frame structures in seismic regions. Previous research has shown that these structures have desirable seismic characteristics such as a self-centering capability and an ability to undergo large nonlinear lateral displacements while sustaining little damage; however, the displacements during a severe earthquake may be larger than acceptable. To reduce the seismic displacement demands, the proposed friction dampers are placed locally at selected beam-to-column joints of a frame, and dissipate energy through the displacements that occur as a result of gap opening between the precast beam and column members. Large scale beam-column specimens with and without dampers were tested under reversed cyclic loading. In addition, isolated friction damper tests were performed to evaluate the effects of dynamic loading rate on the damper behavior. The results show that the dampers can be designed to provide a significant amount of supplemental energy dissipation to a frame, while the self-centering capability of the structure is preserved. The dampers also reduce the beam deterioration under cyclic lateral loading. The experimental results are used to develop an analytical model for friction-damped precast frames.
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