【作者】 闫磊；

【导师】 贺拴海；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2010， 博士

【摘要】 桥梁结构可靠度一直是本领域研究的热点问题之一,桥梁设计规范的演变、荷载等级的修订、概率极限状态设计思想的推广使得可靠度理论越来越向工程应用的方向发展。对于服役桥梁结构而言,受到各种环境荷载及不断增长的车辆荷载与交通流的作用使得结构安全性评估成为当前亟待研究的课题。目前关于结构可靠度的研究多停留在理论阶段,如何面向工程应用将可靠度理论的研究成果实用化,成为本文研究的出发点。本文依托西部交通建设科技项目“西部地区在役砼梁桥结构体系时变可靠度分析与评价方法的研究(2007 318 822 31)”及“桥梁设计荷载与安全鉴定荷载的研究(2008 31849404)”,主要针对服役PC桥梁可靠度评估及RC桥梁加固后可靠度分析方法展开研究,主要的研究内容与成果如下：针对承载能力状态下PC桥梁构件的评估,借鉴现有的耐久性研究成果及相关规程,构造了服役PC桥梁构件受剪和受弯的抗力概率模型。模型考虑了桥梁结构验算系数、承载能力恶化系数、砼截面折减系数、钢筋锈损率、锈蚀钢筋强度降低系数、锈蚀钢筋与砼协同工作系数、管道偏差修正系数、砼强度修正系数；同时考虑了抗力参数测试不定性影响的随机变量及抗力计算模式不定性影响的随机变量。构造了基于评估基准期的汽车荷载效应及人群荷载效应的概率模型,给出了构件承载力可靠度的分级标准,从而建立了服役PC桥梁构件承载能力极限状态可靠度的评估方法。针对正常使用极限状态下的服役PC桥梁全预应力构件及A类构件,以应力失效准则为依据,利用可靠度方法对主梁正截面上下缘有效应力抗力概率模型、恒载效应概率模型、汽车和人群荷载效应概率模型进行了研究,提出了可靠度评估流程并给出了最低可靠指标,建立了PC桥梁构件正常使用可靠度的评估方法。首次利用自主开发的预应力钢束张力测试仪采集了有效预应力的随机样本,对钢束有效预应力的分布规律和统计参数进行了研究。经χ2检验,有效预应力统计参数KEP服从正态分布,即KEP-N(0.97,0.09)。以分位值0.75为依据给出KEP的代表值为0.91，为服役PC桥梁构件正常使用状态的可靠度评估提供了重要依据。以服役RC桥梁构件时变可靠度理论为基础,采用可视化编程工具Visual Basic 6.0开发了可靠度评估系统V1.1,简化了服役RC桥梁可靠性评估的过程。通过对某高速公路上连续一周的车流数据进行统计分析,得到了车重的统计分析结果。利用MATLAB开发了基于实测车辆数据的随机车流模拟程序。给出了以R/(γOγRS)为依据的服役桥梁可靠度评估方法。利用可靠度方法对《公路桥梁加固设计规范》(JTG/T J22-2008)的矩形截面受弯构件的粘帖纤维布及钢板加固进行了分析,以Monte-Carlo法模拟随机样本获得了纤维布加固后的统计参数为：μKR,M =1.713,σKR,M=0.545,δKR,M=0.318；钢板加固后的统计参数为：μKR,M =1.696,σKR,M=0.545,δKR,M=0.320。通过研究发现两种片材加固后构件可靠指标分布规律大致相同,受加固后抗力变异性增大的影响其可靠指标略低于规范的标准。汽车运行状态对中小跨径桥梁可靠度影响较大,当ρ=0.1及2.5时的随着汽车荷载等级的提高其设计安全裕度不断增大,而ρ=1状态下,当汽车荷载效应提高0.5倍时可靠指标最大,以此得出提级加固汽车荷载等级的最优界限。针对加固后构件可靠指标的离散性,提出了以可靠性修正系数γβ来调整安全裕度的方法,通过分析计算给出了不同状况下的γβ值,p越大则γβ越大,反之亦然。采用以上研究成果,对一座服役PC及RC桥梁构件进行了可靠度评估及加固后可靠度的分析,验证了本文提出的方法。更多还原

【Abstract】 Bridge reliability always is one of the concerned problems in this field. Evolvement of design code for bridge, emending of load grade and extension of probabilistic limit state design concepts are accelerating the application process of reliability method. It’s an urgent issue to study that evaluates the existing bridge’s safety because of the increasing traffic flow and vehicle load. At present, research on reliability mainly remains at theory stage, application achievement is not abundant, which is the target of this dissertation.In this dissertation, reliability for the existing pre-stressed bridge and the reinforced concrete bridge were studied respectively based on the western assignment of Ministry of Communications-"Research and assessment method of time-reliability for the existing concrete bridge in west region"(2007 318 822 31) and "Research for design load and safety indentified load of bridge"(2008 318 494 04), the fruitful results are as follows:Based on the research results of durability and correlation regulations, the resisting force probabilistic model in the service pre-stressed concrete bridge was established for it’s resisting of cut and bent, which considered bridge structure checking calculation coefficient, bearing capacity worsening coefficient, concrete section reduction coefficient, steel bar rust damages rate, rusts away steel bar intensity step-down ratio, rusts away steel bar and concrete joint operation coefficient, pipeline deviation correction coefficient, concrete intensity correction coefficient, testing influence random variable, computation pattern uncertainty influence random variable. Probabilistic model of vehicle load and crowd load effect were established based evaluation base period. And the classification principle of bearing capacity reliability was presented, furthermore, the evaluation method for bearing capacity reliability of PC bridge remembers was put forwarded.For the full pc and A-class components under serviceability limit state, the stress-resisting probabilistic model, the dead load effect probabilistic model, the vehicle load and the crowd load effect probabilistic model was established. Assessment process and the limit reliability index was put forward due to the stress failure rule. And the evaluation method for pc bridge stress reliability was presented.Random samples were collected by means of a special instrument named Stretching Force Tester for prestressing strand. Distribution and statistical parameters of effective prestress was studied based on sample collection for actual bridge. Byχ2 identifying, the KEP obeys normal distribution, KEP-N(0.97,0.09). Under the condition ofα=0.75, the representative value is 0.91, which can provide conference for reliability assessment.The reliability assessment system (V1.1) was designed by Visual Basic 6.0 according to the reliability theory of concrete bridge, which simplized the procession of evaluation for the existing bridge.Based on the statistical analysis of random traffic flow date from a domestic highway, a program was designed to simulate the random traffic flow model by means of MATLAB. And the reliability assessment method was put forward on the bases of R/(γOγRS).According to the code of Specifications for Strengthening Design of Highway Bridge (JTG/T J22-2008), the reliability of steel strengthening and fiber strengthening bending members were computed. Random samples were simulated by means of Monte-Carlo method. The statistical parameters of fiber strengthening bending members wereμKR,M=1.713,σKR,M=0.545,δKR,M=0.318, and the statistical parameters of steel strengthening wereμ’KR,M=1.696,σ’KR,M=0.543,δ’KR,M=0.320. The reliabilities of steel strengthening and fiber strengthening bending members were approximately same, and the reliability indexs were slightly lower than the code, which resulted from the increasing of variability of strengthening bending members. The reliabilities of medium-small span bridges were influented deeply by the vehicle operation states, and the bridges’designing safety degree increased with the growth of vehicle load grade under the condition ofρ=0.1 and 2.5. Ifρ=1, the reliability reached maximum when the increasing range of vehicle load effect was 0.5, so the optiomal boundary was concluded. For the discreteness of strengthened member reliability, correction coefficient was put forward to adjust the safety degree of bridge, theγβwas obtained through a solving program in this dissertation, the results showed thatγβincreased with p, and vice verse.The menthod of evaluation and analysis were applicated to an PC bridge and an strengthened RC bridge by the research fruits upwards. And it was verified in this dissertation.更多还原