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A friction damper with displacement dependent variable damping force characteristics was developed. The damper was designed to decrease damping force when damper displacement exceeded a predetermined value. Therefore, the damper is ideal for aseismic retrofit of existing skyscraper buildings in preparation for long-period earthquake ground motions expected to occur in the near future. Dynamic loading tests were conducted on a full-scale steel frame with a brace-type variable friction damper to verify the damper performance. The damper exhibited on-target characteristics, stable performance, and a high endurance capacity under cyclic loadings.

Summary This paper presents an experimental study on the performance of a shear‐sliding stud‐type damper composed of multiple friction units with high‐tension bolts and disc springs. A numerical evaluation of the response reduction effects achieved by the stud‐type damper is also presented. In dynamic loading tests, the behavior of stud‐type multiunit friction damper specimens was investigated. Three different full‐scale damper specimens, which were composed of five, six, or seven friction units with two or four sliding surfaces, were incorporated into loading devices for testing. The stud‐type friction dampers demonstrated stable rigid‐plastic hysteresis loops without any remarkable decrease in the sliding force even when subjected to repetitive loading, in addition to showing no unstable behavior such as lateral buckling. The damper produced a total sliding force approximately proportional to the number of sliding surfaces and friction units. The total sliding force of the stud‐type damper can thus be estimated by summing the contributions of each friction unit. In an earthquake response simulation, the control effects achieved by stud‐type dampers incorporated into an analytical high‐rise building model under various input waves, including long‐period, long‐duration and pulse‐like ground motions, were evaluated. A satisfactory response reduction was obtained by installing the developed stud‐type dampers into the main frame without negatively impacting usability and convenience in terms of building planning.

In this study, the behavior of a passive displacement-dependent variable friction damper (VFD) was evaluated. The energy response behavior of a VFD specimen was investigated by conducting full-scale dynamic loading tests.Full-scale tests demonstrated that the VFD specimen produced a lower sliding force when the device response exceeded a predetermined displacement, resulting in a decreased dissipated energy ratio as the displacement increased.The VFD specimen exhibited stable energy response behavior as well as a stable friction sliding force and friction coefficient under sinusoidal, seismic response, and 100-cycle loadings. The energy response of the VFD specimen was almost independent of the loading frequency. Moreover, a response simulation was conducted using a two-dimensional 30-story nonlinear mainframe model with brace-type VFDs under various input motions, including observation records and long-period, long-duration waves. From the numerical simulations, the peak story drift in the case with brace-type VFDs was not significantly greater than in the case with conventional friction dampers (FDs).The dissipated energy ratios of the mainframe and dampers in the case with the VFDs were approximately identical to those in the case with the FDs. In comparison with conventional FDs, VFDs can produce a lower peak story shear force and axial compressive force in the lowest-story columns at the device installation span.

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