【作者】 王磊；

【导师】 张建仁； 余钱华；

【作者基本信息】 长沙理工大学 ， 桥梁与隧道工程， 2005， 硕士

【摘要】 既有钢筋混凝土桥梁的时变可靠性分析与评估,是目前桥梁工程界亟待解决的问题。本文结合既有钢筋混凝土桥梁结构的特点,研究了既有钢筋混凝土桥梁构件抗力模糊时变概率模型、荷载模糊概率模型、模糊时变可靠性以及主要构件承载力评估等问题,主要研究内容包括以下几个方面: 1)基于一些学者建立的钢筋截面积和钢筋强度、混凝土强度时变模型,进一步考虑模糊性引入阈值,从而建立了钢筋截面积、钢筋强度、混凝土强度模糊时变概率模型。在此基础上推导了抗力均值模糊随机时变函数和标准差模糊随机时变函数,从而得出抗力模糊时变概率模型。2)针对既有桥梁自重标准值、分布统计参数受很多因素的影响难以用确定性的量值加以准确描述的特点,本文通过将恒载概率模型用模糊正态分布来描述,把既有桥梁恒载的均值和标准差作为模糊随机变量来考虑,利用选取的模糊隶属函数中阈值α的取值变化,来解决既有桥梁恒载分布的统计参数同拟建桥梁相比发生变异的问题。3)为使既有桥梁车辆荷载效应特性更接近实际,在将车辆荷载效应随机过程转化为目标基准期内最大值分布随机变量时,通过更改设计基准期的时间区域为评估目标期,在评估目标期内车辆荷载效应最大值分布采用模糊极值I 型分布,参数采用模糊随机变量形式来进行处理,用随时间变化的隶属函数进行描述,对车辆荷载效应特性进行修正。4)考虑抗力和车辆荷载效应模糊时变性,以及恒载和失效准则的模糊性,针对既有混凝土桥梁模糊时变可靠性计算的特点,将既有钢筋混凝土桥梁看成串联系统,建立了桥梁结构承载能力模糊极限状态方程,将JC 法进行改进计算模糊时变可靠指标β% (t ),并编制相应计算程序分析桥梁使用期内的模糊时变可靠指标随时间和阈值α的变化情况。5)基于模糊数学理论与层次分析(AHP)法相结合原理,把影响既有桥梁构件承载力的既相互关联又相互制约的不确定因素系统化,通过模糊隶属函数将定性描述定量化,从而计算出综合折减系数,再与不考虑材料老化与损伤的有限元计算结果相结合来估算既有钢筋混凝土桥梁构件承载力。更多还原

【Abstract】 Nowadays, time-varying reliability analysis and assessment of existing RC bridge are urgent questions to be solved in bridge engineering circles. This thesis studies the fuzzy time-varying probability model of resistance of the structural member, the fuzzy probability model of load, the fuzzy time-dependent reliability and evaluation for ultimate load carrying capacity of main member for the existing RC bridges according to its characteristic. The main study works are as follows: 1)Based on the existing time-varying model of reinforcement strength and its area, and the time-varying model of concrete strength, this thesis introduces threshold value eulteriorly considering fuzziness to create fuzzy time-varying probability models of these factors. Accordingly, the fuzzy random time-varying functions of mean and standard deviation for resistance are deduced, and fuzzy time-varying probability model of resistance is established. 2)Because normal value and distribution statistic parameters of the existing RC bridges dead load are influenced some factors and difficult to describe with deterministic parameters, this thesis regards probability model of dead load as fuzzy normal distribution function, considers mean and standard deviation of bridges dead load as fuzzy random variable, and uses movement of threshold value αin selected membership function to solve variation of statistic parameter for dead load to compare existing bridges with proposed bridges. 3)In order to make live load of the existing bridges be close to practice, design reference period is altered into evaluation target period, maximum distribution of live load is chose as fuzzy extreme value I distribution pattern in target period, and the parameter is selected as fuzzy random variable described with a time-varying membership function to correct live load effect when random process of live load is transformed into random variable of its maximum value distribution in target reference period. 4)Considering fuzzy time-varying feature of resistance and live load, fuzziness of dead load and failure criterion, according to the character of fuzzy time-dependent reliability for existing bridge, the existing reinforced concrete bridge is regarded as series system, this thesis formulates load carrying capacity fuzzy limit state equation, and JC method is improved on to calculate the fuzzy time-dependent reliability index β|-(t ), and a computing program is developed to analysis variety of fuzzy time-dependent index with time and threshold value α. 5) Based on analysis of some factors resulting in reducing the ultimate load carrying capacity of bridge, this thesis uses fuzzing mathematics and analytic hierarchy process (AHP) to systematize these interrelated and interactional factors, quantifies qualitative description with fuzzy membership function, accordingly presents synthetical reduction coefficient, and then unites with finite element without considering material aging and damage to estimate the ultimate load carrying capacity of the existing RC bridge member.更多还原