不同尺寸双腐蚀缺陷管道剩余强度研究

利用非线性有限元分析方法,对含有不同尺寸的双腐蚀缺陷管道剩余强度进行分析,与实验结果进行对比,验证了非线性有限元法的可靠性。在此基础上,分别研究了轴向间距对不同长度、不同深度双腐蚀缺陷管道剩余强度的影响,计算结果表明：当双腐蚀缺陷轴向间距很小时,不同长度双腐蚀缺陷之间存在完全相互作用,而不同深度双腐蚀缺陷之间不存在完全相互作用;随着双腐蚀缺陷轴向间距系数的增加,不同长度和深度双腐蚀缺陷管道失效压力均呈现明显的对数函数变化形式;当双腐蚀轴向间距系数大于2.5 lS后,不同长度和深度双腐蚀相互作用现象均消失。     

面状腐蚀管道承压能力的仿真分析

埋地原油输送管道经常受到原油、土壤等腐蚀,管道内外壁会出现不同形状的腐蚀缺陷,因此会产生应力集中,并削弱管道承压能力,必须对其进行剩余强度评价.本文应用ANSYS软件对含外壁腐蚀管道进行分析计算,得到不同缺陷尺寸的管道在内压作用下的Mises应力,得出腐蚀参数与等效应力的关系曲线,结果表明,有限元法对于分析管道的剩余强度是可靠的,可为外壁腐蚀管道的安全评价提供较为准确和经济的相关依据.     

城市燃气管道信息管理及剩余强度评价

针对目前城市燃气管道信息管理存在的不足,研究和开发了"管网资料查询系统";详细介绍了燃气管道剩余强度计算方法和分析过程,并对含有腐蚀缺陷的管道进行有限元模拟,分析了不同参数对管道最大等效应力的影响,可为下一步推行城市燃气管道的完整性管理奠定基础。     

埋地管道腐蚀检测与评价技术

介绍了土壤腐蚀环境的检测、管道防腐层检测技术、管体腐蚀损伤检测技术及杂散电流检测技术,探讨了管道剩余强度评价方法及管道剩余寿命预测方法。     

北京市埋地燃气管道安全状况评估系统研究

埋地管道失效引起的突发事故会造成严重的财产损失、人员伤亡和环境破坏,针对管道的事故可能性进行评估．可以明确影响管道安全的主要因素．采取有效的措施减小事故的发生。基于安全评估思想和可靠的数学模型,对管道的腐蚀破坏、外力破坏和误操作破坏进行评估,对含缺陷管道进行剩余强度评价和剩余寿命预测,编制了基于GIS平台的评估软件“北京市埋地燃气管道安全状况评估系统”。利用现场检测数据及调查结果进行安全状况等级的评估,评估结论可靠,能直观显示管道的安全等级并提示薄弱环节,提供维护建议,对评估内容和结果适时进行统计分析,操作简单,实用性强。     

埋地钢管外防腐系统检测和评价技术的研究与应用

采用多频管中电流法、埋地外防腐检测仪、超声波导波技术，对埋地钢质管道外防腐等级、破损位置及阴极保护效果进行检测，并结合埋地钢质管道外腐蚀缺陷评价方法对腐蚀状况进行评价，通过评估以确定管道的剩余强度和剩余寿命。     

X100钢管腐蚀剩余强度评价方法研究

为满足长输油气管道经济性的需求,钢管向着超高级别的方向发展,因此对X100、X120等超高级别钢管的安全性评估具有重要意义。介绍了Modified B31G规范、DNV-RP-F101规范和PCORRC方法中腐蚀管道剩余强度的评价方法,并用这3种方法与有限元法对13组含腐蚀缺陷X100钢管爆破试验数据进行计算分析,定量分析两种参数对失效压力的影响。结果表明,有限元模型预测结果准确性和数据集中性好,适用于X100腐蚀钢管剩余强度的评价。Modified B31G规范和PCORRC方法均有不同的适用范围,而DNV-RP-F101规范已完全不适用。建议在工程实际中遇到Modified B31G规范和PCORRC方法不适用的情况时采用有限元方法。     

挖掘荷载作用下埋地输气管道结构可靠性分析

阐述结构可靠性基本原理,利用ABAQUS软件建立埋地输气管道结构可靠性的有限元分析模型,计算极限挖掘荷载,同Driver方程法极限挖掘荷载进行对比,验证了有限元分析模型可以用来计算管道的极限挖掘荷载。应用有限元分析模型,根据结构可靠性理论,计算各类参数(挖掘荷载、覆土厚度、管道外径、管道壁厚、屈服强度、管道内压)变化时输气管道的可靠性,计算该类参数的敏感性指标。得出在保持其他参数不变的情况下,管道壁厚、屈服强度、覆土厚度增大,管道的可靠性会随之增大;管道外径、管道内压、挖掘荷载增大,管道的可靠性会随之减小。参数对管道可靠性的影响程度由大到小的顺序为管道壁厚、挖掘荷载、管道外径、覆土厚度、屈服强度、管道内压。     

基于马尔可夫链理论的埋地管道腐蚀状态预测

腐蚀是埋地燃气钢管最主要的失效方式之一,管道的腐蚀状态会受到土壤环境的影响而具有复杂性和随机性。文中从管壁受腐蚀后剩余厚度入手确立了应用马尔可夫链预测管道腐蚀状况的模型和步骤,建立转移概率矩阵,得到管道腐蚀状态随时间的变化趋势。基于某燃气管道真实腐蚀数据,采用该模型预测了管道腐蚀状态随时间的变化趋势,预测结果显示管道在运行32年后可能发生穿孔泄漏事故。通过该案例得到的结论对安排管道检测修复策略具有一定指导意义。     

基于GRA-FOA-ELM的腐蚀管道剩余寿命预测

为克服预测腐蚀管道剩余寿命的复杂性、传统方法效果差等问题，提出将灰色关联分析（GRA）和果蝇优化算法（FOA）与极限学习机（ELM）有机融合以建立腐蚀管道剩余寿命预测模型。通过GRA计算管道剩余寿命与腐蚀因素的关联度，优选高关联度因素，降低预测的复杂度；采用FOA优化ELM模型的隐含层阈值及输入权值，预测腐蚀管道剩余寿命。以注水管道腐蚀数据为例进行研究分析，结果表明，相对于BP、ELM模型而言，GRA-FOA-ELM模型的预测精度及泛化性能均得到显著提高，从而为油气管道腐蚀研究提供新思路。     

Inspection and maintenance planning of underground pipelines under the combined effect of active corrosion and residual stress

In this paper, a maintenance policy is proposed for pipelines subjected to active corrosion and residual stress, by taking into account imperfect inspection results. The degradation of the pipeline is induced by uniform corrosion, leading to losses of the pipe wall thickness. Localized corrosion is not considered herein, as neither pitting nor crevice corrosion are strongly influenced by external loading conditions and, hence, are not critical in structural strength considerations. When the corroded layers are removed, strain relaxation occurs, causing a redistribution of residual stresses. In parallel, the inspection is applied to detect the corrosion defects, namely the thickness of the corroded layer, and it has a detection threshold under which no corrosion rate can be measured. Due to uncertainties, each inspection is affected by the probability of detecting small defects and the probability of wrong assessment in terms of defect existence and size. The present work aims at integrating imperfect inspection results in the cost model for corroded pipelines, where the failure probabilities are computed by reliability methods. A numerical application on a gas pipe shows the influence of corrosion rates and residual stresses on the optimal maintenance planning.     

Reliability of corrosion-damaged steel structures using interval probability theory

Engineering decisions concerning the performance of existing structures must be made in the presence of uncertainties. The remaining capacity of corroded steel structures provides a good example of different aspects of uncertainty. These include: an unknown or partially known extent of damage; a variability in loading and an uncertain reserve of structural capacity depending on the mode of failure. The theory of structural reliability has been developed to provide a method of analysis for structural safety. In this paper, methods are proposed to compute the component reliability of corrosion-damaged steel members. The application of a recently developed theory called interval probability theory for system reliability is illustrated using the data obtained from actual samples of corroded beams.     

基于KPCA-FA-ELM 模型的管道剩余寿命预测

针对管道剩余寿命的预测问题,提出了一种基于KPCA-FA-ELM组合模型的预测方法,对腐蚀管道剩余寿命预测模型的构建方法以及预测模型的性能验证方法进行研究。以我国某油田的回注水管道和油气集输管道为例,对本次研究所提出的管道剩余寿命预测方法进行验证。研究表明：本次研究所提出的KPCA-FA-ELM模型在进行油田注水管道剩余寿命预测过程中,其最小相对误差为0.38%,最大相对误差为6.1%,平均相对误差为2.35%,均方根误差为0.207,希尔不等系数为0.011,在进行油气集输管道剩余寿命预测过程中,其评价指标均小于其他模型,因此,该种模型的性能优于其他常见预测模型。     

Prediction of residual strength of corroded tensile steel plates

Recently, the damage due to deterioration of materials in many old steel bridge structures, which causes unavoidable strength reduction, is becoming a serious problem in Japan and all over the world. Therefore the remaining load-carrying capacities must be carefully evaluated in order to understand the feasibility of those steel structures for the current usage and to evaluate the necessity of retrofitting of selected corroded members to strengthen the existing structure. This paper proposes a new method to calculate the remaining yield and tensile strengths by using a concept of representative effective thickness (t_eff) with the correlation of initial thickness (t₀) and the maximum corroded depth (t_c,max), based on the results of many tensile coupon tests of actual corroded plates. Further, the feasibility of establishing of an analytical methodology to predict the residual strength capacities of a corroded steel member with fewer number of measuring points is also discussed.     

受拉侧锈蚀钢纤维-钢筋混凝土管片承载力退化模型研究

近年来,国内外新建盾构隧道与管道工程中采用钢纤维-钢筋混凝土管片愈来愈多,在侵蚀环境下管片钢筋锈蚀的问题突出,提出适用于锈蚀后钢纤维-钢筋混凝土管片的残余承载力计算的方法十分重要。鉴于此,文章根据服役期盾构隧道管片所处环境及受力特征,结合钢筋混凝土结构正截面承载力计算理论,提出受拉侧锈蚀钢纤维 钢筋混凝土管片承载力退化模型,并给出相应的求解流程。同时,分析不同锈蚀率与不同钢纤维掺量下受拉侧锈蚀钢纤维-钢筋混凝土管片承载力曲线,并将该模型理论解与压弯荷载作用下钢纤维-钢筋混凝土管片的同步加速锈蚀室内试验结果进行比较,验证了该模型的适用性和可靠性。主要结论有：①随着钢纤维的掺量增加,混凝土的立方体抗压强度会先增大后减小;②偏心受压管片构件极限弯矩最大值随主筋锈蚀率的增大而不断减小,随钢纤维掺量的增大而不断增大,但增大幅度逐渐减小;极限轴力最大值受主筋锈蚀率的影响不大,但随钢纤维掺量先增大后减小。③主筋锈蚀率与钢纤维掺量对大偏心受压构件的影响均大于小偏心受压构件;界限偏心距随主筋锈蚀率的增大而减小,随钢纤维掺量的增大而增大。     

考虑相关性的地下管网系统抗震可靠度分析方法

城市供水、供气、供热等地下管网是重要的生命线工程系统,由于管网中不同管线的结构属性、场地环境、地震动荷载等参数的相关性,管线结构抗震失效事件存在相关性。文章建立相关失效管网系统抗震可靠度问题的解析模型,给出随机变量相关系数在管线可靠度至管网系统可靠度的传递关系。利用基于Nataf变换和正交变换的一次二阶矩法,建立含相关随机变量的管线结构抗震可靠度解析模型;基于结构体系可靠度理论,求解管线结构失效相关系数;采用网络可靠度算法,计算相关失效管网系统节点连通可靠度。同时,给出基于相关随机变量抽样的Monte Carlo随机模拟解法。算例分析结果表明,在管段结构功能函数起控制作用的随机变量的强相关性,对管网系统可靠度影响较大;与传统的管线失效独立假定相比,管线失效事件的强相关性可使并联管网系统可靠度减小15%以上;管网系统拓扑结构的并联冗余性越高,管线失效相关性对系统可靠度的影响越大。     

受腐蚀结构设计可靠度的实用决策方法

在役受腐蚀钢筋混凝土结构由于受到外界侵蚀介质的影响,其抗力水平随着结构服役时间的推移而处于不断的衰减过程中,在结构使用功能保持不变情况下结构可靠度逐渐降低,因此在确定设计基准期内难以完成预期设计功能。基于结构控制截面的强度衰减规律,从《建筑结构设计统一标准》出发,研究建立了不维修受腐蚀结构综合考虑其直接投资和服役效益的最佳设计可靠度指标的决策方法,对侵蚀性介质环境下工作的建筑结构的可靠性设计提供了一种建设性的理论指导     

Ultimate strength reliability analysis of corroded steel-box girder bridges

Structural reliability theory is a useful tool for estimating the risks associated with deteriorating structures. The aim of this study is to develop and demonstrate a procedure for the assessment of box girder bridge ultimate strength reliability with the degradation of plate members due to general corrosion taken into account. A probabilistic model for ultimate steel-box girder strength is established on the basis of an analytic formula that considers corrosion-related, time-dependent strength degradation. The study involves the selection of representative structures, formulation of limit state functions, development of resistance models for corroded steel-box girders, development of load models, development of a reliability analysis method, reliability analysis of the selected bridges and development of the time-dependant reliability profiles, including deterioration due to corrosion. The results of this study can be used for the better prediction of the service life of deteriorating steel-box girder bridges and the development of optimal reliability-based maintenance strategies.