The effect of corrosion defects on the burst pressure of pipelines

The loss of metal in a pipeline due to corrosion usually results in localized pits with various depths and irregular shapes on its external and internal surfaces. The effect of external corrosion defects was studied via a series of small-scale experiments and through a nonlinear numerical model based on the finite element method. After calibration was conducted, based on the experimental results, the model was used to determine the burst pressure as a function of material and geometric parameters of different pipes and defects. This paper briefly summarizes these results, which are subsequently used to develop a simple procedure for estimating the burst pressure of corroded pipes.     

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.     

Probabilistic modeling of structural deterioration of reinforced concrete beams under saline environment corrosion

For existing reinforced concrete structures exposed to saline or marine conditions, there is an increasing engineering interest in their remaining safety and serviceability. A significant factor is the corrosion of steel reinforcement. At present there is little field experience and other data available. This limits the possibility for developing purely empirical models for strength and performance deterioration for use in structural safety and serviceability assessment. An alternative approach using theoretical concepts and probabilistic modeling is proposed herein. It is based on the evidence that the rate of diffusion of chlorides is influenced by internal damage to the concrete surrounding the reinforcement. This may be due to localized stresses resulting from external loading or through concrete shrinkage. Usually, the net effect is that the time to initiation of active corrosion is shortened, leading to greater localized corrosion and earlier reduction of ultimate capacity and structural stiffness. The proposed procedure is applied to an example beam and compared to experimental observations, including estimates of uncertainty in the remaining ultimate moment capacity and beam stiffness. Reasonably good agreement between the results of the proposed procedure and the experiment was found.     

First-order reliability method-based system reliability analyses of corroding pipelines considering multiple defects and failure modes

A methodology that employs the first-order reliability method is proposed to evaluate the time-dependent system reliability of a segment of a pressurised steel pipeline containing multiple active corrosion defects. The methodology considers the leak and burst failure modes of the pipe segment and takes into account the correlations among limit state functions at different corrosion defects. The methodology involves first constructing two linearised equivalent limit state functions for the pipe segment in the standard normal space and then evaluating the probabilities of leak and burst of the segment incrementally over time based on the equivalent limit state functions. The applicability and accuracy of the proposed methodology is illustrated through system reliability analyses of three pipeline examples, each containing ten active corrosion defects whose growth over time is characterised by the linear, nonlinear and homogeneous gamma process-based models.     

Indicators for inspection and maintenance planning of concrete structures

Based on an idea introduced by Benjamin and Cornell (1970. Probability, statistics and decision for civil engineers. New York: McGaw Hill) and previous works by the authors it is demonstrated how condition indicators may be formulated for the general purpose of quality control and for assessment and inspection planning in particular. The formulation facilitates quality control based on sampling of indirect information about the condition of the considered components. This allows for a Bayesian formulation of the indicators whereby the experience and expertise of the inspection personnel may be fully utilized and consistently updated as frequentistic information is collected. The approach is illustrated on an example considering a concrete structure subject to corrosion. It is shown how half-cell potential measurements may be utilized to update the probability of excessive repair after 50 years. Furthermore in the same example it is shown how the concept of condition indicators might be applied to develop a cost optimal maintenance strategy composed of preventive and corrective repair measures.     

Stability loss of thin-walled cylindrical tubes, subjected to longitudinal compressive forces and external corrosion

The paper is devoted to investigation of stability loss of thin-walled elastic circular cylindrical pipes subjected to simultaneous action of longitudinal compressive forces and uniform corrosion from outside. The pipe is treated as a thin closed elastic circular cylindrical shell which can be described within Kirchhoff–Love approximation. The critical time of stability loss of the pipe is found, using the upper critical load value for static stability loss of the pipe, not subjected to corrosion, and the law of corrosion rate. Numerical results were obtained for pipes, made from steel and aluminum with different initial wall thickness.     

The limits to deregulation of entry and expansion of the US gas pipeline industry

US consumers of natural gas have enjoyed significant benefits as the pricing of the commodity has been deregulated. Thanks in large part to the success of deregulation of the natural gas commodity, US federal regulators have embarked upon a wide-ranging programme of eliminating barriers to entry and expansion of natural gas pipelines, which have traditionally been regulated as natural monopolies. As a result, there is now significant excess capacity in the natural gas transmission sector, without measurable benefits to consumers.     

大型箱涵管接口渗漏检测方法及判别标准的探讨

大型污水工程中的箱涵管接口渗漏检测,是目前迫切要解决的技术课题。文中详细介绍了研制开发移动式检测装置对箱涵管接口进行渗漏检测的方法, 确定检测技术标准在实测与理论上的分析和探讨。     

受荷状态下盾构隧道管片锈蚀劣化破坏过程研究

为研究服役期盾构隧道衬砌结构性能衰退演变规律,从隧道结构长期处于水土荷载和周围离子侵蚀环境耦合作用下的特点出发,根据服役盾构管片压弯荷载受荷特征,采用弯矩、轴力导入的方式,等效地模拟盾构隧道管片的实际受力状态,结合围堰式的电化学加速锈蚀方式,研发了可实现压弯受荷状态下进行盾构管片加速锈蚀劣化的试验系统,重点分析不同工况下盾构隧道管片锈蚀劣化发生发展规律。主要结论有：未锈蚀管片裂缝形态主要以受拉横向裂纹为主;未加载锈蚀管片在锈蚀阶段仅产生顺筋锈胀裂纹,裂纹宽度体现出先增大后趋于稳定的特点,加载破坏阶段锈蚀区混凝土在锈胀裂纹和受拉裂纹共同作用下将出现混凝土局部剥离与错动现象;压弯受荷状态下,管片裂缝的扩展是钢筋锈蚀与外加荷载共同作用的效果,管片受拉裂纹与锈蚀裂纹体现出相伴发生发展的规律,管片承载能力存在较大降低。研究成果可为设计基准期内盾构隧道管片衬砌结构长期安全性能评价提供重要参考。     

对建筑工程质检工作管理与实施的探讨

建筑工程质检对于整个项目的开展与进行有着重大的价值和意义,所以应当加强对问题的分析,以促进实践效应的增强。文章详细分析了现代化的建筑工程质检工作开展对策,希望能为今后建筑工程质检管理水准及效益的增强奠定坚实的基础。     

某建筑底部框架-抗震墙结构的检测鉴定

某学校的食宿楼,由于要获得底部的大空间作为食堂,故采用了底部框架-抗震墙结构。文章介绍了用中小学校舍抗震鉴定标准对该房屋的结构进行结构检测与抗震安全性鉴定。     

对桥梁桩基试验和检测的研究

在现代经济的带动下,桥梁建筑工程发展的也越来越壮大,桥梁建设的项目也越来越多。目前,桥梁建筑已经步入了一个新的阶段。本文就桥梁桩基试验和检测的基本概况、桩基的分类以及相关的检测方法做了一些阐述,希望对大家有所帮助。     

对建筑工程质检工作管理与实施的探讨

建筑工程质检对于整个项目的开展与进行有着重大的价值和意义,所以应当加强对问题的分析,以促进实践效应的增强。文章详细分析了现代化的建筑工程质检工作开展对策,希望能为今后建筑工程质检管理水准及效益的增强奠定坚实的基础。     

GPS外业数据质量的影响因素及质量检查

本文首先对影响 GPS 外业观测质量的因素进行了分析,并介绍了TEQC的使用情况。对西宝和成贵两个项目GPS数据进行了预处理,获取了数据质量信息,直接反映出外业数据的真实质量情况,这后续计算成果的真实性、可靠性更有把握。     

新形势下工程质量检测机构诚信发展的实践与思考

近年来,检验检测行业"放管服"改革不断深化,国家建立了"双随机一公开"的新型监管机制,各行业主管部门及行业协会也正在对检验检测机构开展信用评价,以期通过对信用信息的收集和利用,引导检验检测行业树立诚信发展的理念。本文通过对工程质量检测行业存在的信用风险和在新形势下的外部环境分析,结合既往诚信实践,对工程质量检测机构诚信体系的建立和发展提供了参考意见。     

Influence of hydronium,sulfate, chloride and other non-carbonate ions on hydrogen generation by anaerobic corrosion of granular cast iron

Permeable reactive barriers are successfully applied for the removal of various contaminants. The concomitant reduction of hydrogen ions and the subsequent formation of hydrogen gas by anaerobic corrosion lead to decreased pore volume filled with water and thus residence times, so called gas clogging. Long term column experiments were conducted to elucidate the impact of ubiquitous water constituents on the formation of hydrogen gas and potential passivation due to corrosion products. The collected gas volumes revealed a relation to the hydronium concentration (pH) but were only slightly increased in the presence of chloride and sulfate and not significantly influenced in the presence of phosphate, silicate, humic acid and ammonium compared to deionized water. Significant gas volumes within the reactive filling were verified by gravimetry. The presence of nitrate completely eliminated hydrogen formation by competition for electrons. Solid phase analyses revealed that neither chloride nor sulfate was incorporated in corrosion products in concentrations above 0.1 weight percent, and they did not alter the formation of mainly magnetite in comparison to deionized water.     

建筑消防要求及消防监督检查发展

建筑消防直接关系到人们的财产安全和生活稳定,因此就要求消防监督检查人员必须要能够熟练操作基础消防设施。本文就我国目前建筑设施要求和消防监督检查人员应具备的基本能力进行了具体地探讨。     

建筑消防要求及消防监督检查发展

建筑消防直接关系到人们的财产安全和生活稳定，因此就要求消防监督检查人员必须要能够熟练操作基础消防设施。本文就我国目前建筑设施要求和消防监督检查人员应具备的基本能力进行了具体地探讨。     

Computational framework for risk-based planning of inspections,maintenance and condition monitoring using discrete Bayesian networks

This paper presents a computational framework for risk-based planning of inspections and repairs for deteriorating components. Two distinct types of decision rules are used to model decisions: simple decision rules that depend on constants or observed variables (e.g. inspection outcome), and advanced decision rules that depend on variables found using Bayesian updating (e.g. probability of failure). Two decision models are developed, both relying on dynamic Bayesian networks (dBNs) for deterioration modelling. For simple decision rules, dBNs are used directly for exact assessment of total expected life-cycle costs. For advanced decision rules, simulations are performed to estimate the expected costs, and dBNs are used within the simulations for decision-making. Information from inspections and condition monitoring are included if available. An example in the paper demonstrates the framework and the implemented strategies and decision rules, including various types of condition-based maintenance. The strategies using advanced decision rules lead to reduced costs compared to the simple decision rules when condition monitoring is applied, and the value of condition monitoring is estimated by comparing the lowest costs obtained with and without condition monitoring.