Search

Wireless sensor networks usually suffer from the issue of time synchronization discrepancy due to environmental effects or clock management collapse. This will result in time delays between the dynamic responses collected by wireless sensors. If non-synchronized dynamic response data are directly used for structural modal identification, it leads to the misestimation of modal parameters. To overcome the non-synchronization issue, this study proposes a time synchronization approach to detect and correct asynchronous dynamic responses based on frequency domain decomposition (FDD) with frequency-squeezing processing (FSP). By imposing the expected relationship between modal phase angles extracted from the first-order singular value spectrum, the time lags between different sensors can be estimated, and synchronization can be achieved. The effectiveness of the proposed approach is fully demonstrated by numerical and experimental studies, as well as field measurement of a large-span spatial structure. The results verify that the proposed approach is effective for the time synchronization of wireless accelerometer sensors. [ABSTRACT FROM AUTHOR]

In this paper, a customized wireless sensor system (WSS) for structural health monitoring is developed toward large-scale spatial structures. Spatial structures are widely used in large public buildings which generally house thousands of people, therefore the safety of the buildings is a major concern for structural engineers. One of the characteristics of spatial structures is their steel construction and the material is homogeneous throughout. So the strain is commonly the most distinct parameter to indicate status of the structure. Another characteristic of spatial structures is their large-area scale, which brings problem for traditional wired monitoring systems, so an effective wireless sensor network (WSN) for structural monitoring is in urgent demand. Considering those features, the WSS development mainly focused on the sensor selection, hardware design and network customization. In this paper, a vibrating wire sensor is selected for strain measurement because of its stable, durable and anti-electromagnetic properties. For other parameters measurement, some commercial sensor products with digital signal output are adopted. Following the principle of modularization and extendibility, the hardware design is mainly based on the realization of several functional modules. All along, energy efficiency and measurement accuracy are the core design objective. The WSN is classified into four different types of topologies from basic to complex ones. They all have the common working mechanism, namely the collected data transfers via several relay from sensor nodes to sink nodes. Different types of networks are to be customized according to the configuration and scale of different structures. Finally, two typical applications are discussed in detail to verify the feasibility of the system. It can be concluded that the customized WSS is effective and durable, and well satisfies the requirement of structural status monitoring for large-scale spatial structures. Collected data have also shown that the structural stress variation is obvious under the effect of construction process and some other factors. [ABSTRACT FROM AUTHOR]

With the aid of self-developed wireless sensors of structural stress and temperature, long-term measurement of stress and temperature was applied to steel structure of the National Stadium. Based on the measured data, this paper analyzes the distribution of the temperature field, and according to the non-uniformity of the temperature field, the actions of temperature field consists of two parts, uniform and non-uniform. Then this paper studies the performance of the structure under temperature action, during which a comparison was made between the actions of uniform and non-uniform temperature field. With the measured data throughout a whole year, it is indicated that: 1) there is obvious difference between different parts of the structure, and also, the temperature of the structure differs from the air temperature; 2) the stress variation was notable under uniform temperature field action, and the member stress is linear to its temperature ; 3) the non-uniform temperature field makes the stress variation grow larger. At some parts such as the top chords, stress variation caused by non-uniform temperature field is larger than that caused by uniform temperature field action. [ABSTRACT FROM AUTHOR]

• A dictionary is proposed for CS of wind speed using correlation. • A new sliding window is used considering lag, and window size is suggested. • The performance is evaluated using two large-scale spatial structures. • The performance is compared with Fourier basis and linear interpolation. • The influences of relevant critical parameters are comprehensively explored. The real-time wind monitoring is widely used to evaluate the wind effect on the large-scale spatial structures. Wireless sensor network (WSN) is usually the first choice for the large-scale spatial structures to collect wind monitoring data because of its super-large size. Compressive sensing (CS) has great potential in solving the energy problem of WSN and reduces the difficulty in transmission of massive data based on sparsity. However, wind signals are often not naturally sparse on the traditional bases (e.g., Fourier basis). This paper proposes a new method of constructing a dedicated dictionary for wind speed signals using the time-shift strategy. With this proposed dictionary, the signals can be compressed by random sampling and recovered by ℓ 1 -norm sparse regularization. The performance of the improved CS methodology is evaluated using two large-scale spatial structures. The results show that the proposed CS methodology has better performance than the traditional CS algorithm with the Fourier basis and the linear interpolation method. Furthermore, the influences of the relevant critical parameters (regularization parameter, lag, sliding window size, and compression ratio) of the improved CS methodology are comprehensively explored. [ABSTRACT FROM AUTHOR]