Jun Tagami

Forced vibration test of a building with semi-active damper system

The authors developed a semi-active hydraulic damper (SHD) and installed it in an actual building in 1998. This was the first application of a semi-active structural control system that can control a buildings response in a large earthquake by continuously changing the devices damping coefficient. A forced vibration test was carried out by an exciter with a maximum force of 100 kN to investigate the buildings vibration characteristics and to determine the systems 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 influence 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 systems performance was identified by a response control test for steady-state vibration. The elements that composed the semi-active damper system demonstrated the specified performance and the whole system operated well. Copyright

Apparatus for accelerating response time of active mass damper earthquake attenuator

A positive vibration suppression apparatus is disclosed, which suppresses vibrations of a building caused by earthquakes or winds by applying a control force to the building. The apparatus comprises a weight provided on the top of the building in a suspended form to reduce friction and an actuator provided between the weight and the building. The vibration suppression apparatus is controlled through sensing of the vibrations of the building and weight by a sensor, whereas for excessive vibrations of the building the vibrations of the weight are made close to the vibrations of the building to protect the apparatus, because the capacity of the vibration suppression apparatus is limited. Further, in an oil hydraulic system for obtaining a great control force, small and large size oil hydraulic pumps connected to respective small and large size electric motors and an accumulator are provided in parallel, so that the apparatus is warmed up at all time for oil hydraulic control with low power consumption. Two or more vibration suppression apparatuses are controlled at the same time according to the shape of the building to cope with torsional and secondary vibration components.

High Performance Passive Damper With Ingenious Hydraulic Valve System

Newly developed ingenious hydraulic valve system (MAIKO-Ben) autonomously controls the flow valve opening between two hydraulic chambers utilizing the pressure balance between them without an external power source. This impressive function can create a passive hydraulic damper with high performance equivalent to that of previously developed semi-active damper that can absorb much more structural vibration energy than a conventional passive damper. This damper works a semi-active damper while remaining passive. First, we explain the self-regulating hydraulic mechanism of this valve system. The flow control valve is activated through the hydraulic power accumulated in rather small buffer placed between the two hydraulic chambers, and produces maximum or minimum damping coefficient based on the pressure balance between them. Second, we present the results of dynamic loading tests conducted on a full-scale prototype damper (maximum force: 2MN) under both sinusoidal waves and non-stationary seismic response waves. It is confirmed that the developed device showed excellent energy dissipation capacity as expected, and also that the damper’s dynamic characteristics could be well simulated through simply modeling the above hydraulic mechanism. According to these results, it is verified that the MAIKO-Ben system has enough promise to be applied to the real buildings.Copyright