SUMMARYThe Active Variable Stiffness (AVS) system is proposed as a seismic response control system. It actively controls structural characteristics, such as stiffness of a building, to establish a non-resonant state against earthquake excitations, thus suppressing the building's response. It consumes a relatively small amount of energy and maintains the safety of the building in moderate to severe earthquakes. In order to accumulate practical data and investigate them, a building has been constructed as a trial. This paper describes the applied system, the control algorithm, verification of stiffness selection, results of tests for verifying system characteristics, some observed earthquake records and simulation analyses. Responses in controlled and uncontrolled states have been compared to show the effectiveness of the proposed system.
SUMMARYThis paper presents the "rst application of a semi-active damper system to an actual building. The Semi-active Hydraulic Damper (SHD) can produce a maximum damping force of 1000 kN with an electric power of 70 W. It is compact, so a large number of them can be installed in a single building. It is thus possible to control the building's response during a severe earthquake, because a large control force is obtained in comparison with a conventional active control system. This paper outlines the building, the control system con"guration, the SHD, the control method using a Linear Quadratic Regulator, the response analysis results of the controlled building, and the dynamic loading test results of the actual SHD. The simulation analysis shows that damage to building can be prevented in a severe earthquake by SHD control. The dynamic loading test results of the SHD are reported, which show that the speci"ed design values were obtained in the basic characteristic test. The control performance test using simulated response time histories, also shows that the damping force agrees well with the command. Finally, it is con"rmed that the semi-active damper system applied to an actual building e!ectively controls its response in severe earthquakes.
SUMMARYA numerical method has been developed for the dynamic analysis of a tall building structure with viscous dampers. Viscous dampers are installed between the top of an inverted V-shaped brace and the upper beam on each storey to reduce vibrations during strong disturbances like earthquakes. Analytically, it is modelled as a multi-degree-of freedom (MDOF) system with the Maxwell models. First, the computational method is formulated in the time domain by introducing a "nite element of the Maxwell model into the equation of motion in the discrete-time system, which is based on the direct numerical integration. Next, analyses for numerical stability and accuracy of the proposed method are discussed. The results show its numerical stability. Finally, the proposed method is applied to the numerical analysis of a realistic building structure to demonstrate its practical validity.
SUMMARYThe authors developed a semi-active hydraulic damper (SHD) and installed it in an actual building in 1998. This was the "rst application of a semi-active structural control system that can control a building's response in a large earthquake by continuously changing the device's damping coe$cient. A forced vibration test was carried out by an exciter with a maximum force of 100 kN to investigate the building's vibration characteristics and to determine the system's performance. As a result, the primary resonance frequency and the damping ratio of a building that the SHDs were not jointed to, decreased as the exciting force increased due to the in#uence of non-linear members such as PC curtain walls. The equivalent damping ratio was estimated by approximating the resonance curves using the steady-state response of the SDOF bilinear hysteretic system. After the eight SHDs were jointed to the building, the system's performance was identi"ed by a response control test for steady-state vibration. The elements that composed the semi-active damper system demonstrated the speci"ed performance and the whole system operated well.
SUMMARYThe active variable sti ness (AVS) system is proposed as a seismic response control system. It actively controls structural sti ness of a building to establish a non-resonant state against earthquake excitations, thus suppressing the building's response. It consumes a relatively small amount of energy and maintains the safety of the building in moderate to severe earthquakes. In order to accumulate and analyse practical data, a building was constructed as a trial structure about ten years ago. This paper describes the control algorithm, the applied system, some observed earthquake records, veriÿcation of control e ectiveness based on simulation analyses, and some issues concerning system maintenance. Through earthquake observations, it was conÿrmed that the system could select the appropriate sti ness that assures a non-resonant state, which results in a minimum response.
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