【作者】 李伟钊；

【导师】 王宗林；

【作者基本信息】 哈尔滨工业大学 ， 桥梁与隧道工程， 2012， 博士

【摘要】 目前我国公路桥梁总数已超过65万座（混凝土梁式桥约占74%），成为世界第一桥梁大国。据不完全统计，国省县道上的桥梁有42%的桥龄超过10年，有25%的桥龄超过20年。国内公路中小跨径桥梁病害集中暴露期一般在15~20年，大跨径桥梁在6~8年。因此，将有越来越多的公路桥梁出现耐久性降低和承载力不足等问题。为了保证公路建设事业的可持续发展，我国公路建设的重点将逐步由建设转向养护、维修和加固。准确评估桥梁的现有状态是维修加固的基础和依据。目前桥梁评定的手段、方法费时费力，对于桥梁的检测、维修一般都是在桥梁出现明显问题之后才进行，不能做到防患于未然，导致维修加固费用较高。汽车冲击荷载是公路桥梁的主要荷载形式，目前对桥梁的评定主要集中在技术状况及承载力上，很少涉及桥梁的动力工作性能，导致评价结果不全面。桥梁动力测试工作量小、费用低、试验时间短，能重现桥梁的真实运营状态，因此，选择分布较广的混凝土梁式桥开展桥梁动力检测评定技术的研究和实践，探求基于动力测试的桥梁承载力以及动力工作性能评定方法，可避免传统方法的缺点，快速、准确评估桥梁的实际工作状态。目前桥梁动力试验的评价体系尚未成熟。本文围绕如何建立公路混凝土梁式桥动力评定体系这一核心，对所涉及的测试、分析以及评价相关问题进行了研究。主要研究内容及成果概括如下：首先，对桥梁动力特性测试的常规激振方法进行对比分析，确定了跑车、跳车余振法为公路混凝土梁式桥合理的动力特性测试激振方式；理论分析了自由衰减振动响应的特性，引入FFT+FT法对余振信号进行动力特性识别；并给出梁桥动力特性测试、识别的具体方法以及实际工程应用，为梁桥的动力特性评价提供基础。其次，基于Euler-Bernoulli梁讨论了简支梁在弹性支撑、转动约束、轴向力作用以及开口裂缝等因素影响下动、静刚度的变化以及两者之间的相对差异；并通过钢筋混凝土小梁试验对开裂后的结构刚度、阻尼比进行了研究，得到了不同加载等级下动、静刚度以及阻尼比的发展规律。利用有限元方法分析了某3跨连续梁在考虑弹性支座、轴力以及局部损伤等因素影响下动、静刚度的变化以及两者之间的相对差异。通过对桥梁实测数据进行归类分析，得到了各类梁式桥实测动、静刚度之间的关系，并通过桥梁静载试验挠度校验系数常值得到了相应的一阶竖弯频率校验系数范围，由实测频率评价结构的承载能力。针对我国公路正常行驶车辆的车距，根据频率与阻尼比两个参数，提出了结构耗能快慢评价指标以及相应的评价等级。然后，理论分析了简支梁在移动车辆（简化为常量力和简谐力）作用下的静、动响应的频率分布，提出通过频域低通滤波实现对动响应进行动静分离的相关方法。通过有限元方法分析了连续梁桥在移动车辆作用下的静、动响应的频率分布，并把简支梁桥动静分离的方法推广到连续梁桥。结合工程实例介绍了动静分离方法在计算冲击系数、提取振幅以及快速评定桥梁正常使用极限状态承载能力上的应用。接着，对车-桥耦合振动的分析方法进行了研究，为后续的计算分析提供手段。通过概率分布的方法，计算公路桥梁标准图中常规梁桥具有统计意义的动力响应；通过对计算结果的分析，得到了国内公路桥梁竖向加速度、竖向振幅以及冲击系数的合理限值，为评定梁桥的动力响应提供依据。最后，根据动力测试的具体内容，确定本研究的评定内容主要针对于结构的适用性，包括正常使用极限状态承载能力和动力工作性能。提出了基于动力试验的具体综合评定方法，并给出了动力综合评定流程图以及工程应用实例。基于以上分析结果，提出了简单实用的梁式桥动力特性测试、估计方法以及具体的评价方法；提出了动挠度动静分离的具体方法；并得到了动力响应的合理限值；从而确定了基于动力测试的公路混凝土梁式桥工作性能评定具体方法；可对正常使用极限状态承载能力以及动力工作性能进行快速、合理评定。更多还原

【Abstract】 The total number of highway bridges in china is more than650000which is themost of the world at present. The proportion of concrete girder bridge is about74%.According to statistics, the proportion is42%which age is more than10years in thenational, provincial, prefectural highway and25%which age is more than20years.The diseases concentrated exposure period of the domestic short and medium spanbridge is15~20years and long-span bridge is6~8years. Therefore, there will bemore and more highway bridge appearing the problems about durability and bearingcapacity. Highway construction will gradually focus on maintenance, repair andstrengthening from construction to ensure highway construction career sustainabledevelopment.Accurate assessment of the state of existing bridge is the foundation and basisof maintenance and reinforcement. The detection and maintenance commonlycarried out after the bridges have obvious problem because methods to assess bridgestate at present were time-consuming which would lead to higher cost ofmaintenance and reinforcement. Vehicle impact load is the main load form ofhighway bridge. At present the evaluation of bridge is main focus on technicalcondition and bearing capacity, rarely on dynamic performance which results are notcomprehensive. Bridge dynamic testing has the following advantages: small amountof work, short test time and can reappear the real operation state. Thus, choosingthe concrete girder bridge which has wide distribution to research the dynamicevaluation technique and search the bearing capacity and dynamic performanceevaluation method based on dynamic testing would avoid the disadvantages oftraditional methods and provide a way to rapid、accurate evaluate of the actualworking condition of the bridge.At present, the dynamic load tests assessment system of bridge has not yetmature.This paper focus on how to build a dynamic assessment system of highwayconcrete bridge and study the problem related to testing, analysis and evaluationwhich involved in the system. The main research contents and results are as follows:Firstly, vehicle field tests including moving vehicle and jumping vehilcle wereidentified as the reasonable exciting way in the test of dynamic characteristicsthrough the comparation and analysis of the conventional methods. Thecharacteristics of free vibration response are analyzed and the FFT+FT method wereused to identify the dynamic characteristics based on free vibration responses. Thispaper give the process to test and identify the dynamic characteristics and exampleof engineering application. It would provide foundation for dynamic characteristics evaluation of girder bridge.Secondly, the paper analysed the relation of dynamic and static stiffness ofsimple-supported girder under the influence of elastic support、rotational restraint、axial force and open cracks based on the euler-bernoulli beam. RC rectangular beamload tests were carried out to research the change of the dynamic stiffness、staticstiffnrss and damp ratio. There was finite element analysis of continuous beam tostudy the influence in the dynamic and static stiffness of the joints, axial force andpartial damage. The study above provided theoretical basis for using the staticevaluation index to established the dynamic evaluation index. The regressionanalysis of the measured data collected verified the above analysis conclusion andget the regression formula between dynamic and static stiffness. First order verticalbending frequency testing coefficient to evaluate bridge carrying capacityestablished Using the static deflection testing coefficient range in the specification.Dissipating energy evaluation index and corresponding evaluation grade were putforward to evaluate the speed of dissipating vibration energy using frequency anddamping ratio based on the normal spacing of the moving vehicles in highway.Thirdly, frequency distribution of dynamic response of simple-surpported giderbridge under moving vehicle(simplified as a constant force and harmonic force)were analyzed theoretically. Methods to realize separating the dynamic and staticcomposition in dynamic response by frequency domain low-pass filter were putforword. Frequency distribution of dynamic response of continuous gider bridgeunder moving vehicle were analyzed by FEM. separation methods of separation insimple-surpported gider bridge were extend to continuous gider bridge. There wereintroduction of separation methods application in impact factor calculation、amplitude extraction and bearing capacity quickly evaluation combined with theengineering practice.Then, there were reseach on vehicle-bridge coupling vibration analysismethods to provide means for the following calculation. The dynamic response withstatistical significance of conventional highway girder bridges through the methodof probability distribution. The reasonable limits of vertical acceleration, amplitudeand impact factor were discussed to assess the dynamic performance of girderbridge.Finally, the evaluation contents mainly aimed at the applicability of the bridgewhich includes the bearing capacity and dynamic performance. The comprehensivedynamic evaluation system based on dynamic loading test for the concrete girderbridge was put forward. The paper aslo introduced the flow chart of thecomprehensive evaluation system and examples of engineering application.Based on the above analysis results, the simple and practical methods for girder bridge dynamic characteristics test、estimation and evaluation wrer proposed. Theseparation method of the dynamic deflection was put foword. The reasonable limitsof the dynamic response were got. The work performance evaluation methods basedon dynamic testing for the highway girder bridge were established finally, which canbe used to evaluate the serviceability limit state bearing capacity and dynamicperformance quickly and reasonably.更多还原