Kazutaka Shirai

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

Coupled vibration control (CVC) for adjacent buildings can mitigate the seismic response of the system by properly setting the structural parameters, including the connecting elements. However, optimization of the control effect for CVC structures may be limited when using only positive or zero stiffness at the connecting spring. The present study explores the control effectiveness by passive negative stiffness as a connecting element installed between the mainframe and subframe of CVC structure

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 b

This study aimed to understand the mechanical and interfacial properties of fiber-reinforced geopolymer (FRG) layer on the tension zone of normal concrete. A trial mix of FRG using local materials obtained in Hokkaido was investigated. Compression and splitting tensile tests on the FRG test pieces were conducted under different mixing procedures, constituents, volume fractions of the polyvinyl alcohol fiber, curing conditions, and ages. Flexural tests using FRG-normal strength concrete (NSC) com

This study aimed to understand the optimal characteristics of friction dampers considering sway-rocking (SR) motion in vibration control structures during earthquakes. The nonlinear seismic response was numerically obtained using a six-story reinforced-concrete building model with a friction damper and SR springs and damping elements. The results indicate that the SR case shows a less sensitive response change with increased damper sliding force and shows a higher optimal damper sliding force, c

Past research has shown that negative stiffness may be used to good effect in mitigating the response of seismically excited structures. This has led to the emergence of several new negative stiffness devices of varying sizes, complexity, effectiveness, and practicality. In this study, a passive negative stiffness device composed of curved leaf springs using geometric nonlinearity is presented. The proposed device is designed to be simple and compact so as to be easily installed and exhibits app

The present paper introduces a non-linear seismic response estimation method for reinforced concrete (RC) structures based on random vibration theory. Equivalent linear single-degree-of-freedom systems that have complex stiffness are adopted in order to approximate the displacement-dependent hysteretic characteristics of RC structures. The proposed method uses the transfer functions of the equivalent linear systems, root mean square responses, and peak factors. In contrast with existing approxim

The seismic response behavior and control effects of reinforced concrete (RC) structures incorporating a variable friction damper were numerically investigated in this study. The damper considered was a passive displacement-dependent variable friction device (VFD), whose sliding force decreases as the device displacement increases. A nonlinear response simulation was carried out using a single-degree-of-freedom system model under various input motions. The results showed that the VFD was effecti

This study proposes a method for mounting a tuned mass damper (TMD) at the top of a high-rise building through a fail-safe (FS) mechanism using a friction device to protect against strong earthquakes, such as those with long-period, long-duration ground motions. The control effect by the TMD with the proposed friction FS mechanism in single-degree-of-freedom and 30-degrees-of-freedom (30DOF) building models was numerically investigated by an earthquake response simulation. Also, the response for

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 v