模糊数学在桥梁结构损伤评估系统中的应用

桥梁安全性能评估对保证公共交通安全意义重大。现应用模糊数学理论对桥梁损伤度评估法进行了研究。采用二级模糊综合评价的方法建立了桥梁评估的数学模型。在此模型中利用了专家经验所确定的各指标权重,使得评估更合理、科学。实例证明有效、可行。

模糊综合评估在桥梁损伤评估中的应用

针对桥梁损伤评估中目标和影响因素的模糊性,应用模糊数学中的模糊综合评估方法,通过建模、分级,确定各级因素域及权重,得出各级评价向量,定出桥梁整体结构损伤度。最后根据最大隶属原则和非对称贴近度法等两种方法评估出桥梁损伤等级。从应用于大庆市庆虹桥的实际检测评估中证明,此评估方法是合理可行的。

基于模糊层次分析法的战时桥梁损伤等级评定研究

应用了基于模糊数学理论的评估法对桥梁损伤等级的评定进行了研究。首先用二级模糊综合评价的方法建立了桥梁评估的数学模型,并用损伤度来衡量桥梁结构或构件的损伤程度;然后采用分项工程、分部工程、单位工程逐级评定的方法对整座桥梁损伤等级进行评定;最后通过对一座受损桥梁进行损伤等级综合评定说明这种方法的适用性。利用模型评价结果,可针对性采取措施,提高战时桥梁抢修效率。

模糊数学评判方法在桥梁结构受损状态评定中的应用

运用模糊数学中的模糊评判方法,建立结构损伤度函数及隶属函数模型,结合专家提供的各评估对象的因素权重,对在役桥梁结构损伤的状态进行模糊综合评判,通过比较桥梁损伤度隶属函数值的大小来确定其对应的受损程度等级。结合实例分析结果表明,糊数学评判方法可以较好地运用于桥梁结构受损状态评判,且其评判结果与中国公路桥梁管理系统(简称CBMS)应用软件计算的结果一致。

一种桥梁评估专家系统的设计和实现

桥梁评估是桥梁维修和加固的重要依据。以桥梁评估专家系统为例 ,具体阐述了一种利用VC ++对模糊推理专家系统实现的方法。讲述了这个专家系统所依据的 2种评估方法 :结构损伤度评估方法和承载力评估法。重点阐述了知识库的知识表示和推理机的实现。给出了整个系统的构成和评估流程图。实际工程应用表明 ,该专家系统具有良好的工程应用性。

既有铁路桥梁状态评估指标体系和方法研究

基于大量学者关于桥梁结构状态评估的研究成果,建立既有铁路桥梁结构状态评估指标体系。在总结国内外桥梁状况评估分级和评定标准的基础上,提出基于可靠度理论的既有铁路桥梁状态评估标准。根据层次分析法原理,计算出评估体系的综合集成权值,并结合模糊理论,定义结构平均损伤度,从而形成一套新的基于可靠度理论的既有铁路桥梁状态评估方法。最后,给出一个既有铁路桥梁状态评估实例说明所提出方法的实现过程。

Damage warning of suspension bridges based on neural networks under changing temperature conditions

This paper aims at successive structural damage detection of long-span bridges under changing temperature conditions.First,the frequency-temperature correlation models of bridges are formulated by means of artificial neural network techniques to eliminate the temperature effects on the measured modal frequencies.Then,the measured modal frequencies under various temperatures are normalized to a reference temperature,based on which the auto-associative network is trained to monitor signal damage occurrences by means of neural-network-based novelty detection techniques.The effectiveness of the proposed approach is examined in the Runyang Suspension Bridge using 236-day health monitoring data.The results reveal that the seasonal change of environmental temperature accounts for variations in the measured modal frequencies with averaged variances of 2.0%.And the approach exhibits good capability for detecting the damage-induced 0.1% variance of modal frequencies and it is suitable for online condition monitoring of suspension bridges.

Influence of Copper Stress on Ultra-structure of Wheat Seedlings

Transmission Electron Microscope (TEM) Technology was used to investigate the effect of 25,100 and 200 mg/kg copper on ultra-structure of root tip and leaf blade of wheat. Result showed that serious damage was found with Copper of 25,100 and 200 mg/kg. Plasmolysis,concentrated cytoplasm,chloroplast inflation,lamellar structure disturbance,capsule disappearance and disintegration,mitochondria structures ambiguity and vacuolization were all symptoms under Cu stress. There were positive correlation between concentration of coper stress and the degree of injury,and the degree of injury of copper were different in different organelles. Mitochondria were the most sensitive organelles,and there was patient difference in the same organelles of different parts.

Damage alarming of long-span suspension bridge based on GPS-RTK monitoring

Structure damage identification and alarming of long-span bridge were conducted with three-dimensional dynamic displacement data collected by GPS subsystem of health monitoring system on Runyang Suspension Bridge.First,the effects of temperature on the main girder spatial position coordinates were analyzed from the transverse,longitudinal and vertical directions of bridge,and the correlation regression models were built between temperature and the position coordinates of main girder in the longitudinal and vertical directions;then the alarming indices of coordinate residuals were conducted,and the mean-value control chart was applied to making statistical pattern identification for abnormal changes of girder dynamic coordinates;and finally,the structural damage alarming method of main girder was established.Analysis results show that temperature has remarkable correlation with position coordinates in the longitudinal and vertical directions of bridge,and has weak correlation with the transverse coordinates.The 3%abnormal change of the longitudinal coordinates and 5%abnormal change of the vertical ones caused by structural damage are respectively identified by the mean-value control chart method based on GPS dynamic monitoring data and hence the structural abnormalities state identification and damage alarming for main girder of long-span suspension bridge can be realized in multiple directions.

Damage identification of steel truss bridges based on deep belief network

To improve the accuracy and anti-noise ability of the structural damage identification method,a bridge damage identification method is proposed based on a deep belief network(DBN).The output vector is used to establish the nonlinear mapping relationship between the mode shape and structural damage.The hidden layer of the DBN is trained through a layer-by-layer pre-training.Finally,the backpropagation algorithm is used to fine-tune the entire network.The method is validated using a numerical model of a steel truss bridge.The results show that under the influence of noise and modeling uncertainty,the damage identification method based on the DBN can identify the accurate damage location and degree identification compared with the traditional damage identification method based on an artificial neural network.

Damage Identification in Footbridges from Natural Frequency Measurements

The present study aims to develop a robust structural damage identification method that can be used for the evaluation of bridge structures. An approach for the structural damage identification based on the measurement of natural frequencies is presented. The structural damage model is assumed to be associated with a reduction of a contribution to the element stiffness matrix equivalent to a scalar reduction of the material modulus. A computational procedure for the direct iteration technique based on the non-linear perturbation theory is proposed to identify structural damage. The presented damage identification technique is applied to the footbridge over the Slunjcica River near Slunj to demonstrate the effectiveness of the proposed approach. Using a limited number of measured natural frequencies, reduction in the stiffness of up to 100% at multiple sites is detected. The results indicate that the proposed approach can be successful in not only predicting the location of damage but also in determining the extent of structural damage.