Ye Xiao-Wei, Su You-Hua, Xi Pei-Sen
Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China.
Sensors (Basel). 2018 Feb 7;18(2):491. doi: 10.3390/s18020491.
In this paper, a fiber Bragg grating (FBG)-based stress monitoring system instrumented on an orthotropic steel deck arch bridge is demonstrated. The FBG sensors are installed at two types of critical fatigue-prone welded joints to measure the strain and temperature signals. A total of 64 FBG sensors are deployed around the rib-to-deck and rib-to-diagram areas at the mid-span and quarter-span of the investigated orthotropic steel bridge. The local stress behaviors caused by the highway loading and temperature effect during the construction and operation periods are presented with the aid of a wavelet multi-resolution analysis approach. In addition, the multi-modal characteristic of the rainflow counted stress spectrum is modeled by the method of finite mixture distribution together with a genetic algorithm (GA)-based parameter estimation approach. The optimal probability distribution of the stress spectrum is determined by use of Bayesian information criterion (BIC). Furthermore, the hot spot stress of the welded joint is calculated by an extrapolation method recommended in the specification of International Institute of Welding (IIW). The stochastic characteristic of stress concentration factor (SCF) of the concerned welded joint is addressed. The proposed FBG-based stress monitoring system and probabilistic stress evaluation methods can provide an effective tool for structural monitoring and condition assessment of orthotropic steel bridges.
本文展示了一种基于光纤布拉格光栅（FBG）的应力监测系统，该系统应用于一座正交异性钢桥面板拱桥。FBG传感器安装在两种易发生疲劳的关键焊接接头上，用于测量应变和温度信号。在被研究的正交异性钢桥的跨中及四分之一跨处，围绕纵梁与桥面板以及纵梁与横梁区域总共部署了64个FBG传感器。借助小波多分辨率分析方法，给出了施工期和运营期公路荷载及温度效应引起的局部应力行为。此外，采用有限混合分布方法结合基于遗传算法（GA）的参数估计方法，对雨流计数应力谱的多模态特性进行建模。利用贝叶斯信息准则（BIC）确定应力谱的最优概率分布。此外，采用国际焊接学会（IIW）规范中推荐的外推法计算焊接接头的热点应力。研究了相关焊接接头应力集中系数（SCF）的随机特性。所提出的基于FBG的应力监测系统和概率应力评估方法可为正交异性钢桥的结构监测和状态评估提供有效工具。
