【作者】 时玉平；

【导师】 程永春；

【作者基本信息】 吉林大学 ， 道路与铁道工程， 2013， 博士

【摘要】 桥梁结构自振频率是桥梁设计、检测、监测以及损伤识别工作中最为常用的参数之一。测试到的桥梁结构自振频率会因外界环境因素改变而发生一定的变异，有关研究资料表明，外界环境因素引起的自振频率变异值有时会淹没桥梁结构自身损伤引起的自振频率变化值。温度是导致桥梁结构自振频率发生变异的主要因素之一，目前国内外学者们在此方面的研究工作才刚刚起步，温度对桥梁结构自振频率的影响机理、影响规律以及剔除方法等方面还没有得到确定的研究结论。因此开展桥梁结构自振频率的温度效应分析，形成从测试到的自振频率中剔除温度影响的有效方法是十分必要的。对于混凝土桥梁结构，混凝土材料的力学性能直接决定着桥梁结构动力性能。因此混凝土材料力学性能在不同温度条件下体现的变异性可能是导致桥梁自振频率变化的一个重要原因。国内外科研工作者们在温度对混凝土力学性能影响方面开展了一些基础性的研究工作。研究成果主要集中在极高或极低温度条件下混凝土材料力学性能的变异性。但针对桥梁结构是室外环境温度导致野外桥梁混凝土力学性能的变化。另一方面，针对不同类型混凝土材料温度对其力学性能的影响规律不尽相同。在桥梁结构中，简支梁和连续梁是常见的两种结构形式，在非线性温度梯度作用下简支梁中会存在温度自应力，连续梁中会存在温度自应力和温度次应力，从而使结构的振动初始状态发生了一定的改变。这种结构振动初始状态的改变是如何导致自振频率改变的，还需要进一步的深入研究。吊杆拱桥的索力大小及分布情况对全桥的受力性能具有重要的影响，可以认为吊杆拱桥的索力状态将决定着该类桥梁结构的运营安全性和使用舒适性，因此准确的掌握索力状态是十分必要的。想要及时的掌握索力状态信息，最为有效的手段便是构建索力监测系统，对全桥索力进行实时监测。索力监测系统中数据传输模块可以采用有线或无线两种方式，无论采用何种传输方式，传输的数据都是海量的，这样容易大致系统瘫痪或难以从海量数据中获取有效信息。因此，需要对传输的数据进行甄别，对传输数据进行有效控制，只对有效数据进行传输，这正是需要解决的问题之一。索力状态评价模块需要从采集到的动力响应中分析出索力，进而对索力进行评价，评价一般分为单索索力状态评价和全桥索力状态评价两个层面。有关研究资料表明，外界环境温度对索力的测试值具有一定的影响，有时温度引起的索力变化都能够淹没索力的实际变化值。寒冷地区具有年平均温差大，且昼夜温度差别明显等特点，因此这种现象在寒冷地区的索力测试过程中尤其明显。因此无论哪个层面的索力状态评价，都需要考虑温度对索力的影响。在桥梁结构（尤其是大跨径柔性桥梁结构）自振频率的测试过程中，环境温度、湿度、通行车辆以及风载等都有可能导致测试到的自振频率发生变异。有关研究资料表明，不同的频率阶次（不同的振动形式）受到各因素影响的程度是不同的，并且各因素对自振频率的影响是一个复杂的非线性过程。要对测试频率的温度效应进行分析，必须在桥梁结构的多阶振动中找到那阶或那几阶自振频率主要受温度的影响。在确定了主要受温度影响的频率阶次后，更为重要的任务便是如何从依据实测数据建立环境温度与桥梁结构自振频率的关系。进而形成有效的环境温度影响的剔除算法，以便从测试到的自振频率中分析出温度的影响。由于各因素对自振频率的影响存在一定的耦合，因此从中找到主要受环境温度影响的频率阶次是十分困难的。温度对自振频率的影响是一个复杂的非线性过程，形成有效的剔除温度影响的方法也是一项十分艰巨的任务。本文依托863国家高科技研究发展计划项目“季节冻土区大范围道路灾害参数监测与辨识预警系统研究（2009AA11Z104）”和高等学校博士学科点专项科研基金项目“基于多元温度场的桥梁模态频率修正方法研究（20090061110036）”，针对桥梁自振频率温度效应分析及寒冷地区吊杆索力监测系统构建进行研究，主要开展了以下研究工作：1、测定了在-20℃-60℃条件下混凝土的立方体抗压强度、轴心抗压强度、弹性模量、劈裂抗拉强度以及泊松比等几项力学参数。采用广义最小二乘方法对测试数据进行了统计分析，归纳分析了温度对各项力学参数的影响规律。2、形成了日照温度场作用下简支梁自振频率的计算方法，提出了基于随机子空间方法的连续箱梁桥自振频率分析方法。3、采用灰色关联分析等理论，形成了对海量数据的甄别方法，对传输数据能够进行有效控制，进而构建了一套索力监测系统。采用神经网络方法对单索索力进行分析、评价。基于灰色关联分析和支持向量机算法等理论，形成了全桥索力分析、评价方法。单索索力状态评价方法和全桥索力状态评价方法度能够有效的剔除外界环境温度的影响。4、以一座三跨吊杆拱桥为工程依托，首先采用相关性分析来从多阶自振频率中找到主要受温度影响的频率阶次。接着采用粒子群优化神经网络算法对测试数据进行分析，建立温度与自振频率的关系，进而形成温度影响剔除方法。更多还原

【Abstract】 The natural frequencies are the most common parameters in bridge design, detection,monitoring and damage identification. The bridge natural frequencies measured can alter asthe changes in external environmental factors. Related data show that the changes in naturalfrequencies aroused by external environmental factors can cover those caused by damage.Temperature is the main factor leading to the changes in the natural frequencies. At present,the scholars at home and abroad set about the researches in this respect, however, until nowthere is no conclusion about the mechanism, influencing laws and the excluding methods oftemperature affection on the bridge natural frequencies. Therefore, it’s necessary to form theeffective method in excluding temperature effects from the measured natural frequencies.To the concrete bridge structure, the mechanical property of the concrete material directlydetermines the structural dynamic performance. So the variability of the concrete materialmechanical property under different temperatures may lead to the changes in the bridgenatural frequencies. The scholars at home and abroad conducted some basic researches onthe mechanical property changes caused by the temperature. Research results concentrate onthe changes in the concrete material mechanical property in the extreme high temperature orthe extreme low temperature. But the bridges are structures affected by the outdoorenvironment temperature. On the other hand, the influencing laws of different concretematerials on the mechanical properties are not the same.In bridge structures, simply-supported and continuous beams are the most commonstructure styles. Under the nonlinear temperature gradient, simply-supported beam may havethe thermal self-restraint stress, and continuous beams may have the thermal self-restraintstress and secondary temperature stress, which change the structure vibration initial state.And how the changes in vibration initial state lead to the changes in the natural frequenciesshould be researched further.The values and distribution of the cable forces of tied arch bridge has significant effects onthe mechanical property of the whole bridge. It’s believed that the cable force statedetermines the operational safety and the comfort in use of this kind of bridge. So it’snecessary to accurately master the cable force bridge. In order to timely grasp the cable forcestate, the most effective method is to build the monitoring system of cable force to conduct real-time monitoring of the whole cable forces. To the data transmission module, there aretwo kinds of transmission methods. They are wired and wireless methods. No matter whichmethod, the data transmitted are giant, which may easily lead to system breakdown and thedisability to acquire effective information from the giant data. Therefore, it’s necessary toeffectively screen and control the data transmitted, which is one of the problems with urgentneed to be solved. The cable force condition evaluation module analyzes the cable forcesfrom the collected dynamic responses, and then evaluates the cable forces. The evaluationsinclude the single cable force state evaluation and the whole bridge cable force stateevaluation. Related data show that the external environmental temperature has someinfluences on the cable forces measured. Sometimes, the changes caused by the temperaturecan drown the real changes of the cable forces. In chill regions, the temperature range greatlyin a year and in a single day. Therefore, the problem is especially obvious in the cable forcetests in the chill regions. So no matter which kind of cable force evaluation, the temperatureshould be taken into consideration.In the testing process of the natural frequencies of the bridge, especially the large-spanflexible bridge, the environmental temperature, moisture, traffic and the wind load maycause the changes in the natural frequencies. Related data show that each factor influencedifferent frequency modes and vibration styles in different extent. And each factor influencesthe natural frequencies in a non-linear process. In order to analyze the measured thermaleffect, the natural frequency modes of the bridge which are mainly affected by thetemperature should be picked out from the multiple frequency modes. After determining thefrequency mode mainly affected by the temperature, the next assignment more important isto establish the relationship between the environmental temperature and the bridge naturalfrequencies based on the measured data. Then form the excluding algorithm of the effectiveenvironmental temperature, so as to analyze the temperature effects from the naturalfrequencies measured. Because different factors have a coupling effects on the naturalfrequencies, it’s difficult to find out the frequency mode mainly affected by the temperature.The effects of temperature on natural frequencies are a complex nonlinear process, it’s achallenge to establish the method excluding temperature effects.Relying on the National High Technology Research and Development Program ofChina(863Program)“Research on the System for Monitoring, Identification andEarly-warning of Wide Range Road Hazards in Seasonal Frozen Soil” and the SpecializedResearch Fund for the Doctoral Program of Higher Education Project “Study on the Bridge Modal Frequency Updating Technique Based on the Multiple Temperature Fields(20090061110036)”,and this paper conducts the following researches to analyze thetemperature effects on bridge natural frequency and monitoring system construction offorces in hangers in chill region:1. The cube compressive strength, axial compressive strength, modulus of elasticity, tensilesplitting strength and Poisson’s ratio are measured under the temperature of-20℃-60℃. Thegeneralized least squares method is applied to conduct statistical analysis on the measureddata and conclude the influencing law of temperature on each mechanical parameter.2. The natural frequency calculation method of simply-supported beam is formed underthe solar radiation, and the natural frequency analysis method for continuous box girderbridge is present based on the SSI.3. Grey relational analysis theory is used to form the screening method for the massivedata and effectively control the data transmission, then establish a cable force monitoringsystem. Neural network method is applied to analyze and assess the single cable force. Andthe analysis and assessment for all the cable forces are formed based on the grey relationaltheory and the support vector machine arithmetic. Both the single cable bridge stateassessment method and the whole bridge cable force assessment method can effectively getrid of the effects of external environment.4. Based on the project of a three-span tied arch bridge, reduction of dimensionality isconducted to the influencing factors by means of nonlinear principal component analyticalmethod, and the frequency mode mainly affected by the temperature is picked out from themultiple natural frequencies combined correlation analysis. Then the measured data areanalyzed by means of the grey particle swarm optimization neural network algorithm toestablish the relationship between temperature and the natural frequencies, and then form themethod to get rid of the temperature.更多还原