Regarding Structural Health Monitoring (SHM) for seismic acceleration, Wireless Sensor Networks (WSN) is a promising tool for low-cost monitoring. Compressed sensing and transmission schemes have been drawing attention to achieve effective data collection in WSN. Especially, SHM systems installing massive nodes of WSN require efficient data transmission due to restricted communications capability. The dominant frequency band of seismic acceleration is occupied within 100 Hz or less. In addition, the response motions on upper floors of a structure are activated at a natural frequency, resulting in induced shaking at the specified narrow band. Focusing on the vibration characteristics of structures, we introduce data compression techniques for seismic acceleration monitoring in order to reduce the amount of transmission data. We carry out a compressed sensing and transmission scheme by band pass filtering for seismic acceleration data. The algorithm executes the discrete Fourier transform for the frequency domain and band path filtering for the compressed transmission. Assuming that the compressed data is transmitted through computer networks, restoration of the data is performed by the inverse Fourier transform in the receiving node. This paper discusses the evaluation of the compressed sensing for seismic acceleration by way of an average error. The results present the average error was 0.06 or less for the horizontal acceleration, in conditions where the acceleration was compressed into 1/32. Especially, the average error on the 4th floor achieved a small error of 0.02. Those results indicate that compressed sensing and transmission technique is effective to reduce the amount of data with maintaining the small average error.
Wireless sensor networks (WSNs) technologies have attracted much attention to collect damage information in a natural
disaster. WSNs to monitor temperature or humidity usually collect data once in some seconds or some minutes. Since
structural health monitoring (SHM), meanwhile, aims to make a diagnosis for the state of a structure based on detected
acceleration, WSNs are a promising technology to collect acceleration data. One concern to employ WSNs in SHM is to
detect phenomena at a high sampling rate under energy-aware condition. In this paper, we describe a model for seismic
acceleration monitoring, configured with multi-layer networks: WSNs, a wireless distribution system (WDS) and a
database server, where the WDS is mainly operating in a wireless local area network (WLAN). Examining the
performance in the test bed for the monitoring system, the results showed the system was capable of collecting
acceleration at a rate of 100 sampling per second (sps) even in the fashion of intermittent operation, and capable of
storing data into a database. We also suggest that the method using intermittent operation with appropriate sampling rate
is effective in providing a long time operation for the system by considering in the response motion of a structure.