Largest portion of the bridge stock in almost any country and bridge owning organisation consists on ordinary bridges that has short or medium spans and are now deteriorating due to aging, etc. Therefore, it is becomi...Largest portion of the bridge stock in almost any country and bridge owning organisation consists on ordinary bridges that has short or medium spans and are now deteriorating due to aging, etc. Therefore, it is becoming an important social concern to develop and put to practical use simple and efficient health monitoring systems for existing short and medium span (10 - 30 m) bridges. In this paper, one practical solution to the problem for condition assessment of short and medium span bridges was discussed. A vehicle-based measurement with a public bus as part of a public transit system (called “Bus monitoring system”) has been developed to be capable of detecting damage that may affect the structural safety of a bridge from long term vibration measurement data collected while the vehicle (bus) crossed the target bridges. This paper systematically describes how the system has been developed. The bus monitoring system aims to detect the transition from the damage acceleration period, in which the structural safety of an aged bridge declines sharply, to the deterioration period by continually monitoring the bridge of interest. To evaluate the practicality of the newly developed bus monitoring system, it has been field-tested over a period of about four years by using an in-service fixed-route bus operating on a bus route in the city of Ube, Yamaguchi Prefecture, Japan. The verification results thus obtained are also described in this paper. This study also evaluates the sensitivity of “characteristic deflection”, which is a bridge (health) condition indicator used by the bus monitoring system, in damage detection. Sensitivity of “characteristic deflection” is verified by introducing artificial damage into a bridge that has ended its service life and is awaiting removal. As the results, it will be able to make a rational long-term health monitoring system for existing short and mediumspan bridges, and then the system helps bridge administrators to establish the rational maintenance strategies.展开更多
Modem dynamic tests such as networked collaborative pseudo-dynamic testing （PDT） provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT...Modem dynamic tests such as networked collaborative pseudo-dynamic testing （PDT） provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT systems established in China and abroad are introduced, including a detailed description of the first networked collaborative platform that involved the construction of a standardized demonstration procedure for networked collaborative PDT. The example is a multi-span bridge with RC piers retrofitted by FRP, and a networked structural laboratory （NetSLab） platform is used to link distributed laboratories located at several universities together. Substructure technology is also used in the testing. The characteristics, resource sharing and collaborative work of NetSLab are described, and the results illustrate that use of the NetSLab is feasible for studying the dynamic performance of multi-span bridge structures.展开更多
提出了基于局部均值分解(LMD)的同步电机参数辨识方法。采用LMD从短路电流中提取直流电流和基波电流,然后分别采用稳健回归最小二乘和Prony算法对直流电流和基波电流进行辨识,进而获得同步电机参数。以理想突然短路电流信号为例,通过仿...提出了基于局部均值分解(LMD)的同步电机参数辨识方法。采用LMD从短路电流中提取直流电流和基波电流,然后分别采用稳健回归最小二乘和Prony算法对直流电流和基波电流进行辨识,进而获得同步电机参数。以理想突然短路电流信号为例,通过仿真分析了滑动平均跨度与LMD循环次数和电流相对均方误差的关系,确定了滑动平均跨度。高信噪比(30 d B)时,由于LMD具有平滑滤波功能而无模态混叠现象发生。低信噪比(15 d B)时,提出了基于前置滑动平均LMD的短路电流分离方法,可有效获取直流电流和基波电流分量。较之经验模态分解(EMD),基于LMD的理想突然短路电流分解效果更好。仿真结果表明,与EMD方法相比,所提方法受噪声影响较小,参数辨识精度更高。展开更多
文摘Largest portion of the bridge stock in almost any country and bridge owning organisation consists on ordinary bridges that has short or medium spans and are now deteriorating due to aging, etc. Therefore, it is becoming an important social concern to develop and put to practical use simple and efficient health monitoring systems for existing short and medium span (10 - 30 m) bridges. In this paper, one practical solution to the problem for condition assessment of short and medium span bridges was discussed. A vehicle-based measurement with a public bus as part of a public transit system (called “Bus monitoring system”) has been developed to be capable of detecting damage that may affect the structural safety of a bridge from long term vibration measurement data collected while the vehicle (bus) crossed the target bridges. This paper systematically describes how the system has been developed. The bus monitoring system aims to detect the transition from the damage acceleration period, in which the structural safety of an aged bridge declines sharply, to the deterioration period by continually monitoring the bridge of interest. To evaluate the practicality of the newly developed bus monitoring system, it has been field-tested over a period of about four years by using an in-service fixed-route bus operating on a bus route in the city of Ube, Yamaguchi Prefecture, Japan. The verification results thus obtained are also described in this paper. This study also evaluates the sensitivity of “characteristic deflection”, which is a bridge (health) condition indicator used by the bus monitoring system, in damage detection. Sensitivity of “characteristic deflection” is verified by introducing artificial damage into a bridge that has ended its service life and is awaiting removal. As the results, it will be able to make a rational long-term health monitoring system for existing short and mediumspan bridges, and then the system helps bridge administrators to establish the rational maintenance strategies.
基金The Key Project of the Major Research Plan of Natural Science Foundation of China Under Grant No.90715036the Key Project of the Natural Science Foundation of China Under Grant No.50338020
文摘Modem dynamic tests such as networked collaborative pseudo-dynamic testing （PDT） provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT systems established in China and abroad are introduced, including a detailed description of the first networked collaborative platform that involved the construction of a standardized demonstration procedure for networked collaborative PDT. The example is a multi-span bridge with RC piers retrofitted by FRP, and a networked structural laboratory （NetSLab） platform is used to link distributed laboratories located at several universities together. Substructure technology is also used in the testing. The characteristics, resource sharing and collaborative work of NetSLab are described, and the results illustrate that use of the NetSLab is feasible for studying the dynamic performance of multi-span bridge structures.
文摘提出了基于局部均值分解(LMD)的同步电机参数辨识方法。采用LMD从短路电流中提取直流电流和基波电流,然后分别采用稳健回归最小二乘和Prony算法对直流电流和基波电流进行辨识,进而获得同步电机参数。以理想突然短路电流信号为例,通过仿真分析了滑动平均跨度与LMD循环次数和电流相对均方误差的关系,确定了滑动平均跨度。高信噪比(30 d B)时,由于LMD具有平滑滤波功能而无模态混叠现象发生。低信噪比(15 d B)时,提出了基于前置滑动平均LMD的短路电流分离方法,可有效获取直流电流和基波电流分量。较之经验模态分解(EMD),基于LMD的理想突然短路电流分解效果更好。仿真结果表明,与EMD方法相比,所提方法受噪声影响较小,参数辨识精度更高。
