In the light of the characteristics of pedestrian-induced vibration comfort evaluation of long-span footbridges, a real-time evaluation system of pedestrian-induced footbridge vibration comfort was developed based on Android platform for the first time. The system is composed of data acquisition subsystem, management center subsystem and Android mobile client. On the basis of collecting pedestrian-induced vibration signals by using the built-in high-precision acceleration sensor, space coordinate transformation algorithm was used to the dynamic signal acquisition process, transformation from smartphone’s coordinate system to the inertial coordinate system was achieved. Wavelet transformation was used to isolate gravity from the raw signals, the aim of this paper is to develop a real-time evaluation system. The system was tested on Guangzhou Gangding Footbridge, the field test results show that the comfort degree obtained from the system was identical with the truth, which demonstrates that the real-time vibration comfort evaluation system is scientific and effective, it makes up for the vacancy of real-time evaluation of pedestrian-induced footbridge vibration comfort.
In bridge construction, geometry control is critical to ensure that the final constructed bridge has the consistent shape as design. A common method is by predicting the deflections of the bridge during each construction phase through the associated finite element models. Therefore, the cambers of the bridge during different construction phases can be determined beforehand. These finite element models are mostly based on the design drawings and nominal material properties. However, the accuracy of these bridge models can be large due to significant uncertainties of the actual properties of the materials used in construction. Therefore, the predicted cambers may not be accurate to ensure agreement of bridge geometry with design, especially for long-span bridges. In this paper, an improved geometry control method is described, which incorporates finite element (FE) model updating during the construction process based on measured bridge deflections. A method based on the Kriging model and Latin hypercube sampling is proposed to perform the FE model updating due to its simplicity and efficiency. The proposed method has been applied to a long-span continuous girder concrete bridge during its construction. Results show that the method is effective in reducing construction error and ensuring the accuracy of the geometry of the final constructed bridge.
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