Summary
This paper proposes a data‐driven damage detection method based on fixed moving principal component analysis (FMPCA) to analyze structural dynamic responses and monitor the bridge operational condition and the damage occurrence. The damage indices based on principal components (PCs) and eigenvalues can be calculated continuously by applying a fixed moving window. The length of the moving window is determined by using a new criterion based on the convergent spectrum of cumulative contribution ratio. Numerical simulations and experimental tests in the laboratory on beam bridge models subjected to stochastic loads are conducted to investigate the accuracy and effectiveness of the proposed approach. Both simulation and experimental results indicate that using the FMPCA can well analyze the dynamic vibration data to detect damage or abnormal vibration behavior during the operational condition. It can be used to accurately monitor the time instant of damage occurrence, which is very important in long‐term monitoring of civil engineering structures. The proposed method is successfully applied to analyze the data recorded during an incident that a real large‐scale suspension bridge was slightly scraped by the mast of a sand ship, which further verifies the effectiveness and feasibility of this method in engineering applications. The results also indicate that the bridge was not damaged after the incident but presented a short time abnormal vibration behavior owing to the impact of the ship mast.
Purpose
The purpose of this paper is to describe a simulation and experimental research concerning the effect of recess depth on the lubrication performance of a hydrostatic thrust bearing by constant rate flow.
Design/methodology/approach
The computational fluid dynamics and finite volume method have been used to compute the lubrication characteristics of an annular recess hydrostatic thrust bearing with different recess depths. The performances are oil recess pressure, oil recess temperature and oil film velocity. The recess depth has been optimized. A test rig is established for testing the pressure field of the structure of hydrostatic thrust bearing after recess depth optimization, and experimental results show that experimental data are basically identical with the simulation results, which demonstrates the validity of the proposed numerical simulation method.
Findings
The results demonstrate that the oil film temperature decreases and the oil film pressure first increases and then decreases with an increase in the recess depth, but oil film velocity is constant. To sum up comprehensive lubrication performance, the recess depth of 3.5 mm is its optimal value for the annular recess hydrostatic thrust bearing.
Originality/value
The computed results indicate that to get an improved performance from a constant flow hydrostatic thrust bearing, a proper selection of the recess depth is essential.
Dockless bike-share systems have experienced unprecedented growth in China since 2016. This report investigated the comprehensive nationwide impact of dockless systems in 12 Chinese cities with relatively high bike-share usage and a thriving bike-share economy: Shanghai, Beijing, Guangzhou, Shenzhen, Chengdu, Wuhan, Hangzhou, Nanjing, Xi’an, Jinan, Xiamen and Lanzhou. The study found that, with effective management and safe infrastructure, dockless bike-share systems can be an excellent last-mile urban mobility solution that enhances connectivity to public transit, reduces carbon emissions by replacing motorized trips, and improves public health by preventing thousands of premature deaths.
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