Tadashi Nasu

Active response control of buildings for large earthquakes - seismic response control system with variable structural characteristics

This paper presents two types of active seismic-response control systems with variable structural characteristics, developed with the objective of ensuring that the safety and function of buildings are not impaired by large earthquakes. The systems are characterized by the active seismic-response control of large-scale civil engineering structures during large earthquakes, using only nominal amounts of energy. One system is the non-resonant active variable stiffness (AVS) system. The results of applying this system to an actual building and confirming its effectiveness through seismic observation are given. Additionally, the results from a simulation analysis evaluating the effectiveness of the system if applied to a high-rise building are also included. Then a brief outline is given of the other system, the active variable damping (AVD) system.

Time synchronized wireless sensor network and its application to building vibration measurement

Network based wireless sensing has become an important area of research and various new applications for remote sensing are expected to emerge. One of the promising applications is structural health monitoring of building or civil engineering structure and it often requires vibration measurement. For the vibration measurement via wireless network, time synchronization is indispensable. In this paper, we introduce a newly developed time synchronized wireless sensor network system. The system employs IEEE 802.11 standard based TSF counter and sends the measured data with the counter value. It enables consistency on common clock among different wireless nodes. We describe the accuracy evaluation by simulation studies when the size of nodes increased. The hardware and software specifications of the developed wireless sensing system are shown. The experiments were conducted in a three-story reinforced concrete building and results showed the system performs more than sufficiently.

IEEE 802.11-Based Wireless Sensor System for Vibration Measurement

Network-based wireless sensing has become an important area of research and various new applications for remote sensing are expected to emerge. One of the promising applications is structural health monitoring of building or civil engineering structure and it often requires vibration measurement. For the vibration measurement via wireless network, time synchronization is indispensable. In this paper, we introduce a newly developed time synchronized wireless sensor network system. The system employs IEEE 802.11 standard-based TSF-counter and sends the measured data with the counter value. TSF based synchronization enables consistency on common clock among different wireless nodes. We consider the scale effect on synchronization accuracy and evaluated the effect by taking beacon collisions into account. The scalability issue by numerical simulations is also studied. This paper also introduces a newly developed wireless sensing system and the hardware and software specifications are introduced. The experiments were conducted in a reinforced concrete building to evaluate synchronization accuracy. The developed system was also applied for a vibration measurement of a 22-story steel structured high rise building. The experimental results showed that the system performed more than sufficiently.

Time synchronized wireless sensor network for vibration measurement

Network based wireless sensing has become an important area of research and various new applications for remote sensing are expected to emerge. One of the promising applications is structural health monitoring of building or civil engineering structure and it often requires vibration measurement. For the vibration measurement via wireless network, time synchronization is indispensable. In this paper, we introduce a newly developed time synchronized wireless sensor network system. The system employs IEEE 802.11 standard based TSF counter and sends the measured data with the counter value. It enables consistency on common clock among different wireless nodes. We describe the accuracy evaluation by simulation studies when the size of nodes increased. The hardware and software specifications of the developed wireless sensing system are shown. The experiments were conducted in a three-story reinforced concrete building and results showed the system performs more than sufficiently.

IEEE 802.11 timing synchronization based wireless sensor system for vibration measurement

Network based wireless sensing has become an important area of research and various new applications for remote sensing are expected to emerge. One of the promising applications is structural health monitoring of building or civil engineering structure and it often requires vibration measurement. For the vibration measurement via wireless network, time synchronization is indispensable. In this paper, we introduce a newly developed time synchronized wireless sensor network system. The system employs IEEE 802.11 standard based TSF counter and sends the measured data with the counter value. TSF based synchronization enables consistency on common clock among different wireless nodes. We consider the scale effect on the synchronization accuracy and the effect is evaluated by stochastic analysis and simulation studies. A new wireless sensing system was developed and the hardware and software specifications are shown. The experiments were conducted in a reinforced concrete building and results showed that the system performed more than sufficiently.