【作者】 任伟平；

【导师】 强士中；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2008， 博士

【摘要】 各种连接细节的疲劳性能是焊接钢桥研究的热点问题之一。随着运营车辆总重和交通量的不断增加,近些年来焊接钢桥所面临的疲劳问题正日趋严重。本文结合我国焊接钢桥疲劳研究的现状,对焊接钢桥细节的疲劳破坏行为、标准疲劳车荷载模型、变幅车辆荷载作用下的疲劳强度设计曲线和疲劳寿命可靠性评估方法等问题进行了系统深入的研究,最后以两座典型桥梁为工程背景,建立了焊接钢桥细节的疲劳寿命评估程序。本文主要就以下几个方面进行了探讨和研究。全面总结了国内外焊接钢桥中易发生疲劳破坏的典型细节,对其疲劳破坏行为进行了分析,在此基础上提出了焊接钢桥的疲劳设计步骤及需要注意的问题,并就焊接钢桥疲劳裂纹检查和修复方法进行了讨论。在对BS5400、AASHTO以及Eurocode 1等桥梁设计规范的疲劳荷载谱计算方法进行详细介绍和分析的基础上,针对我国现行公路桥梁设计规范未对车辆荷载谱进行明确规定的不足,通过对我国不同地区五条典型国道主干线所进行的车辆状况调查,提出了用于钢桥疲劳累积损伤计算的10种典型车辆荷载模型及出现频率,代表车辆模型包含2类客车和8类货车。为方便应用,通过对不同跨径简支梁和两等跨连续梁的模拟计算,提出了一个适用于我国国道主干线高速公路钢桥的简化疲劳车辆荷载模型,所提出的标准疲劳车模型包含一辆三轴车和一辆四轴车。通过分析证明了本文所提出的标准疲劳车模型能够较好的反映桥梁的实际受力状况,可用于我国国道主干线上的钢桥疲劳计算。依据我国道路交通荷载的调查数据,使用基于LEFM的疲劳寿命评估方法,对焊接钢桥典型细节在随机变幅应力作用下的疲劳寿命曲线进行了研究,运用所编程序对五种交通荷载、四种跨径和四种细节的变幅疲劳寿命曲线进行了模拟计算。通过对计算结果的拟合分析,提出了适合我国实际情况的变幅车辆荷载作用下焊接细节疲劳寿命设计曲线的修正方法。研究了钢桥细节疲劳寿命估算的两种方法:一种是基于S-N曲线的方法,该方法可用于能够明确疲劳强度等级的新建钢桥焊接细节;另一种是基于LEFM的方法,该方法可用于不能明确疲劳强度等级或已存在裂纹的焊接细节。通过分析,提出了这两种分析方法的极限状态方程,参考国内外大量文献资料,确定了各随机变量的统计参数,建立了基于可靠性理论的疲劳寿命评估方法。以张石高速公路石家庄互通式立交主线上一座跨线桥主桥和湛江海湾大桥主桥为例,建立了焊接钢桥连接细节疲劳寿命评估流程,可为焊接钢桥的疲劳设计和养护维修策略制定提供科学决策依据。最后,通过对我国四座大跨径钢箱梁斜拉桥的计算分析,就大跨度钢桥主要受力细节的疲劳问题与桥梁跨径的关系进行了探讨,并得出了一些有益的结论。更多还原

【Abstract】 Fatigue cracks initiated from various connection details are common problems in welded steel bridge structures. Though extensive research has been performed in the past few decades, various fatigue problems are still occurring on a frequent basis. With truck weight increase and traffic volume growth, the fatigue problem in welded steel bridge structures is becoming more and more serious. This dissertation discusses a few most common types of fatigue cracks, and develops two fatigue reliability approaches for estimating fatigue lives of details in welded steel bridges. The main research contents and results are as follows.The dissertation analyses the fatigue failure mechanism of the most common connection details in welded steel bridges, and summarizes the research on fatigue of steel bridges in the world, which give an important reference to fatigue reseach and design of steel bridges in our country.Due to the absence of fatigue vehicle models in current Chinese highway bridge design specifications, the fatigue load models of BS5400, AASHTO, and Eurcode 1 bridge design code are introduced and analysed. Based upon the traffic data collected from five representative national highway sites, the main vehicle types included two types of buses and eight types of trucks for estimating fatigue damage accumulation are developed. The vehicle axle weights, axle spacings, and gross weights are measured with weight-in-motion (WIM) system. The load spectrum data were simulated over analytical bridge models, including simple and two-equally continuous spans. Based on the simulation results, the 3-axle and 4-axle standard fatigue truck models were developed. A discussion of the accuracy of fatigue vehicle models of AASHTO, BS5400, and Eurcodel bridge design code in estimating fatigue damage and the new developed standard fatigue vehicle models also presented.Based upon the load spectrum data collected from some representative national highway sites, the fatigue life curves (S-N curve) of four typical details in welded steel bridges subjected to random, variable-amplitude traffic cycles are computed using linear elastic fracture mechanics (LEFM) approach. Eighty results are finished by utilizing a FORTRAN program that is writted to simulate the random process. Based on the simulation results, the corrected S-N design curves are developed.Two fatigue reliability formulations that can be applied for most details in steel bridges are developed. One model is based on S-N Curve approach which is used for details classified according to fatigue categories in bridge design codes; the other is based on LEFM approach which is used for details not classified according to fatigue categories in bridge design codes. The variables needed for fatigue reliability analysis in either the S-N or the LEFM approaches is also studied and statistics on these variables have been compiled in this dissertation to assist in performing reliability analyses.Through two typical case studies, Shijiazhuang Overbridge in Zhang-Shi highway and Zhanjiang Gulf Bridge, a convenient fatigue evaluation procedure for welded steel bridge structures is developed. The fatigue design and scheduling of inspections and repairs can be performed according to the analytical result.Finally, the relationship between the fatigue life of some key welded details, N, and the main span length, L, is discussed based on analysis for four long-span cable-stayed bridges with steel box-girder.更多还原