Separation and extraction of bridge dynamic strain data

Through comparing the measured data of dynamic strains due to loading and temperature by the stain gauge and temperature sensor at the same location, the information in the strain data was divided into three parts in the frequency domain by using the defined index named power spectral density (PSD)-ratio index. The three parts are dominated respectively by temperature varying, stresses, and noises and thus can be distinguished from the determined the separatrix frequencies. Also, a simple algorithm was developed to separate the three types of information and to extract the strain caused mainly by structural stresses. As an application of the proposed method, the effect of strain deformation and noises on the fatigue assessment was investigated based on the separated data. The results show that, the determined values of separatrix frequencies are valuable for the monitoring data from other bridges. The algorithm is a multiresolution and hierarchical method, which has been validated as a simple and effective method for data analyses, and is suitable for the compression and preprocessing of the great amount monitoring data and easy to be integrated into the structural health monitoring (SHM) soft system. The strain due to temperature varying attributes a little to the errors of fatigue assessment; however, the noises or random disturbance existed in the monitoring data have much responsibility for the errors, and the main reason is that the random disturbance shifts the real strain/stress amplitude picked up by real structural stress or strain.     

钢桥面沥青混合料铺装应变动态响应实测研究

掌握钢桥面沥青混合料铺装层在车载作用下的真实力学特性对桥面铺装体系设计有重要意义,而现阶段现场桥面铺装层的力学实测数据仍偏少,尤其缺乏对铺装层不同温度下服役时力学特性的长期监测。为此,该研究对钢桥面双层SMA混合料铺装进行现场实桥加载试验,实测铺装层在低温、中温、高温3种服役温度下的应变响应数据。试验结果表明,钢桥梯形肋正上方铺装层混合料在中低温服役状态下主要承受压应变的作用,而在高温服役时则主要承受拉应变的作用;动载作用过程中铺装层底纵向应变会出现拉压应变交替作用的现象,而横向应变只体现为拉应变或压应变的形式;加载车行驶速度对混合料的应变极值均有明显的影响,加载车低速行驶时混合料层底横向及纵向变形最为显著。同时,研究利用加载试验中铺装层应变响应时程曲线,计算不同加载状态下混合料对应的加载频率数值,计算结果可为钢桥面铺装混合料室内试验中加载频率参数的确定提供参考。     

高应变动力检测桥梁基桩极限承载力

阐述了高应变法测量基桩极限承载力的基本原理，并运用高应变CASE法和CCWAPC程序相校核，对桥梁基桩极限承载力进行了抽样实测，结果证实满足设计要求。     

GPS-RTK数据滤波降噪识别桥梁动态位移序列研究

桥梁结构的健康监测是桥梁安全的重要保障。监测数据的滤波降噪识别桥梁动态位移序列是健康监测数据处理的重要内容。以自锚式悬索桥天津市富民桥为背景,在交通不封闭的情况下对富民桥的动态响应进行连续的实时监测,通过GPS传感器采集结构振动位移原始数据。采用Ⅰ型切比雪夫高通滤波器和自相关函数的模态分解算法(EMD)进行滤波降噪,提取的桥梁结构实际振动波形,获取桥梁结构频率为0. 83 Hz。研究结果表明,该方法与有限元分析得出的结果非常接近,GPS-RTK数据滤波降噪识别桥梁动态位移序列可靠。     

直桥与弯桥动力特性对比分析

针对直桥与弯桥的动力力学性能,采用大型通用有限元软件ANSYS分别对直线桥,连续弯桥,墩梁固结弯桥建立空间模型,并对其进行模态振型,频率分析,阐述了直、弯桥在动力力学性能上的差异,指出弯桥整体性不如直线桥好.     

谈桥面铺装层对高速公路桥梁受力性能的影响

以监测技术为背景,研究了一种以应变监测为信息来源的横向分布状态指标,通过该指标,来提早判断梁式桥的横向连接状态,为桥梁大修提供决策依据。通过某桥的实际例子,验证了该方法的可行性。     

人行天桥动力性能研究

结合福州某环形天桥管养工作,对该人行天桥的动力性能和人致振动的舒适性开展探讨,通过动力测试及有限元模型分析,结果表明竖向基频低于3Hz,引起行人不适,建议通过增强天桥主梁刚度或设置减震措施,同时避免在天桥上设置广告而增加自重。     

基于应变监测的梁式桥横向分布状态指标研究

以监测技术为背景,研究了一种以应变监测为信息来源的横向分布状态指标,通过该指标,判断梁式桥的横向连接状态,为桥梁大修提供决策依据。通过某桥的实际例子,验证了该方法的可行性。     

斜拉桥动力分析综述

简述了对斜拉桥进行固有振动分析和动力反应分析的必要性，就斜拉桥的动力特性、风振性能、抗震性能进行了计算分析，以促进斜拉桥的研究，从而为桥梁的发展做贡献。     

石川河大桥静动载试验分析

结合石川河大桥工程实例,介绍了荷载试验的测点布置,讲述了荷载试验的加载工况及加载车辆,分析研究了静载试验结果及动载试验结果,为评价桥梁的承载力提供了依据。     

中承式钢管混凝土拱桥调查与动力特性分析

中承式钢管混凝土拱桥作为一种新型的桥梁型式应用广泛。在统计分析国内已建成的100余座中承式钢管混凝土拱桥的基本资料基础上,得出了跨径、矢跨比、边主跨比、矢高比、宽跨比和拱轴线型等设计参数的常用范围;根据统计得到的典型桥例为基准,采用MIDAS有限元软件分析桥例的结构动力特性;对典型桥例进行结构动力特性参数分析,得到了各设计参数对结构动力特性的影响规律。     

钢筋混凝土工字桥梁的建模与动力分析

本文设计了两种截面的钢筋混凝土工字梁,并对使用的两座预应力混凝土梁桥的动力特性进行了对比分析。两座桥的长度、宽度和主梁深度相同。然而,第一座桥使用了六个传统窄翼缘型工字梁,而第二座桥仅使用了四个宽翼缘型工字梁。桥梁对动荷载的响应是借助于复杂的有限元模型获得的。对桥梁进行了模态和时程分析,以确定两座桥梁的动态特性、行为和响应。获得了桥梁的动力特性和挠度,并对不同主梁和跨度的桥梁进行了比较。有限元模型的输出表明,虽然宽翼缘型工字梁梁数较少,但其挠度小于传统窄翼缘型工字梁的相应值。     

在役混凝土桥梁结构的动态可靠性评估分析

介绍了钢筋混凝土桥梁构件的动态可靠性评估方法,初步分析了荷载效应概率模型、结构抗力概率模型以及抗力的影响因素,提出动态可靠性理论也可以作为可靠性的预测方法,可以使人们获得任意时点的可靠度,从而应用于桥梁结构的可靠性评估.     

土的动力Hardin-Drnevich模型小应变特性及其阈值应变研究

以Hardin-Drnevich模型的双曲骨架曲线为基础,采用Masing准则构造其滞回圈,形成小应变土体动力耗散函数.然后从热力学基本定律出发,分析其对应的屈服面及能量耗散特性.发现筑坝堆石类无黏性材料的动力特性存在2个阈值应变,定义为第一和第二阈值应变.两个阈值应变将土体动力特性分成3段.当土体的动应变小于第一阈值应变时,土体屈服为常摩擦系数的摩擦耗散控制;当土体动应变介于第一、第二阈值应变之间时,土体屈服为变摩擦系数的摩擦耗散控制;当土体动应变大于第二阈值应变时,土体屈服除摩擦机制外还存在剪胀等土体结构改变的效应.土体的2个阈值应变主要受最大动剪切模量系数及指数控制,无黏性土的摩擦角对其也有一定影响.两个阈值应变均随最大动剪切模量系数及指数的增大而减小.     

土的动力Hardin-Drnevich模型小应变特性及其阈值应变研究

以Hardin-Drnevich模型的双曲骨架曲线为基础,采用Masing准则构造其滞回圈,形成小应变土体动力耗散函数。然后从热力学基本定律出发,分析其对应的屈服面及能量耗散特性。发现筑坝堆石类无黏性材料的动力特性存在2个阈值应变,定义为第一和第二阈值应变。两个阈值应变将土体动力特性分成3段。当土体的动应变小于第一阈值应变时,土体屈服为常摩擦系数的摩擦耗散控制;当土体动应变介于第一、第二阈值应变之间时,土体屈服为变摩擦系数的摩擦耗散控制;当土体动应变大于第二阈值应变时,土体屈服除摩擦机制外还存在剪胀等土体结构改变的效应。土体的2个阈值应变主要受最大动剪切模量系数及指数控制,无黏性土的摩擦角对其也有一定影响。两个阈值应变均随最大动剪切模量系数及指数的增大而减小。     

谈公路桥梁动载试验在桥梁检测中的应用

对某高速公路桥梁动载试验的内容作了介绍,论述了截面测试和测点布置的方法,并对动载试验在桥梁检测过程中的应用方法进行了研究,指出桥梁动载试验在桥梁检测与评估、桥上荷载识别、疲劳试验等过程中具有广阔的应用前景。     

斜拉桥动力特性的参数化研究

结合具体工程实例，着重从重力特性的角度，对斜拉桥的几种结构体系进行了分析比较，给出了它们的自振特点和影响规律，以促进斜拉桥振动特性的研究，从而为斜拉桥的设计提供参考。     

Damage detection method for large structures using static and dynamic strain data from distributed fiber optic sensor

A method for damage detection applicable to large slender steel structures such as towers of large-scale wind turbines, long-span bridges, and high-rise buildings is presented. This method is based on continuous strain data obtained by distributed fiber optic sensor (FOS) and neural network (NN) analysis. An analytical model for cracked beam based on an energy balance approach was used to train a NN. The continuous static strains and the natural frequencies obtained from the distributed FOSs were used as the input to the trained NN to estimate the crack depths and locations. An experimental study was carried out on a cracked cantilever beam to verify the present method for damage identification. The cracks were inflicted on the beam, and static and free vibration tests were performed for the intact case and the damage cases. The distributed FOSs were used to measure the continuous strains. The damage estimation was carried out for the 5 damage cases using the NN technique. It has been found that the identified crack depths and locations agree reasonably well with the inflicted cracks on the structure.     

矮塔斜拉桥动力特性分析

以安邦河斜拉桥为背景,借助有限元分析软件Midas/Civil,采用子空间迭代法对其进行了计算,得出了该桥的自振特性,计算结果可为该桥后期运营过程中的健康检测与维修提供参考,同时,为进一步认识矮塔斜拉桥的动力性能起参考作用。     

Wind induced dynamic response of the Wye bridge

As part of the research effort to improve the understanding of the effect of wind on bridges, the Transport and Road Research Laboratory (TRRL) has measured the wind-induced dynamic response of the 235 m span cable stayed box girder bridge that carries the M4 motorway over the River Wye. Measurements are presented which were made during the winter months of 1977 and 1978, using automatic recording equipment developed at TRRL.

The main wind-induced vibration frequency measured was at 0.46 Hz, which corresponds to the first bending mode. The response occurs mainly when the wind speed is in the range 7–8 m/s and the direction is close to normal to the bridge. This agrees with wind tunnel section tests but the maximum amplitudes predicted in the laboratory have not been attained to date. The strong dependence of vibration amplitude on wind speed, showing a peak in the range 7–8 m/s is characteristic of vortex shedding excitation. The problem of predicting the likelihood of the bridge response from wind speed data is discussed.

Finally, the effect on the fatigue life of the structure is discussed. It is shown that it is most unlikely that wind-induced oscillations will contribute to a significant shortening of the fatigue life of the bridge.