可靠性分析—混凝土桥的结构处理工具（中英文对照）

《可靠性分析—混凝土桥的结构处理工具（中英文对照）》由会员分享，可在线阅读，更多相关《可靠性分析—混凝土桥的结构处理工具（中英文对照）（13页珍藏版）》请在装配图网上搜索。

1、可靠性分析混凝土桥的结构处理工具钢筋混凝土桥结构对多种恶化机制敏感，包括碱趋于和缓行动和氯化物进入。 实际的研究已经被与这些机制和其他问题联系起来承担。 这一直特别在那些案件在过去的大约20年，那些目标是鉴定引起，结果并且发展补救策略。 这已经改进加强的混凝土的理解长期性能并且导致技术的发展增加恶化抵抗。 目前，在一个问题已经被鉴定之后，最共同的方法是行动，被称为重新活跃的维修。 这不可能以前最经济解决办法，在许多场合，维修比比预防处理方法昂贵。 不过，在恶化是明显的之前，拥有人经常不愿意为预防处理方法支付。 处理方法的尽快应用归根结底可能不是这个最佳的解决办法。 综合恶化和性能预测模型化对很

2、重要支持积极计划和检查，试验与维修。 这作为年龄和理由给提供资金的维护变得越来越批判性的基础设施变得越来越重要。性能评价可以被通过调查，测试和正式的计算取得， 最好基于尽可能准确代表结构的状况的场所数据。 以把提前检测的 恶化模型和评价结合起来工具和性能准则(在元素， 结构或者组水平) 基于维护关于与时间有关的性能剖面图的政体变得可能。 这鉴于花费程序的全部妻子特别相关。 可靠性分析已经作为在这个多客观的管理过程里的一件重要的工具出现，这必须考虑到安全，功能性和持续标准。 用简单术语，一个结构或者一个系统的可靠性是取得特别的性能水平的可能性。 可能性或者可能是这个适当的措施，因为全部工程系统对

3、不确定敏感，起因于随便现象和不完全的知识。 在结构工程方面的可靠性分析使与装，材料，恶化，模型化和其他因素相关的不确定的确定数量成为可能。 这些统一到估计在一个结构的使用年限期间达到保证性能水平的可能性的一种方法中。 两个对安全水平的校准来说在规则和标准和改进和精炼评价方法学里，这种方法正越来越被在桥工程使用。 这篇文章的目的是在管理易受到恶化的桥过程中略述它的申请。桥梁性能指标当今英国评价代码关心最后限制说明(ULS)并且不明确要求使用能力所限制的检查说明(ULS)。 可以认为一种现有的结构已经经历SLS在它的生命期间装。 不过，被广泛地相信的挠度的SLS 标准和断裂不完全考虑到那些问题通过

4、恶化矫柔造作。 基于恶化的象弄脏的锈那样的标准，失效并且弄碎需要被认为，因为他们清楚影响桥性能，起作用和金融。 这些经常关于连接管理策略证明有势力的因素。通过明确地考虑到和指定性能水平， 为了建立检查与维修政体适合特别的结构/ 成员工程师知道重要恶化指标。 这些性能水平超时可以改变， 由于在功能，装，例如的结构重要等等方面的变化， 在实际之间的关系和要求性能被用图1 显示的图解概念化。 因此，可靠性分析可能用来阐述性能将超过要求的可能性，因此估计结构的可靠性。 性能测量可能与安全，功能性或者任何其他合适的标准有关解决由氯化物引起的腐蚀这项特别的工程专心于加强的混凝土恶化的一个具体的领域，特别是

5、起因于氯化物进入。 氯化物存在于在冬天在英国使用的除冰的盐。 氯离子迁移虽然使凝固，例如以吸收和扩散。 在合适条件下，他们起动加固酒吧腐蚀。 腐蚀机制产生锈。 金属的被增加的体积，由于锈，导致断裂，失效并且具体的盖子的弄碎。 在更迅速和广泛的加固腐蚀里的这结果。在一个问题已经被鉴定之后，最共同的方法是行动，被称为重新活跃的维修。 这不可能以前最经济解决办法，在许多场合，维修比比预防处理方法昂贵。 不过，在恶化是明显的之前，拥有人经常不愿意为预防处理方法支付。 处理方法的尽快应用归根结底可能不是这个最佳的解决办法。 综合恶化和性能预测模型化对很重要支持积极计划和检查，试验与维修。 这作为年龄和理

6、由给提供资金的维护变得越来越批判性的基础设施变得越来越重要。性能评价可以被通过调查，测试和正式的计算取得， 最好基于尽可能准确代表结构的状况的场所数据。 以把提前检测的 恶化模型和评价结合起来工具和性能准则(在元素， 结构或者组水平) 基于维护关于与时间有关的性能剖面图的政体变得可能。 这鉴于花费程序的全部妻子特别相关。 如果共同不及格，加强在伸缩接头下面位于的混凝土桥元素特别对氯化物攻击敏感。 在英国的公路高架桥通常由交叉梁直接在伸缩接头下面位于的加强的混凝土组成，(参阅图2)。 很多交叉梁已经遭受严厉的加固腐蚀，失效和弄碎。 一典型例子在3 图让看，加固覆盖在哪里交叉梁有失效。一概率恶化模

7、特适合加强零部件被发展的混凝土桥，考虑到这些结构和他们的环境的特性。 它以为扩散和吸收都通过混凝土扮演氯化作用迁移的角色， 在到达交叉梁 表面的除冰的盐的数量方面的变化性和每年这些数量怎样变化。 考虑交叉梁的典型氯化物暴露区域包括：位于破坏的扩大的节点下面的水平表面，这种节点是浸于水中的位于扩大的紧密的节点下面的垂直表面，它通常是暴露在道路中氯化物容易飞溅到的地方等.数据适合很多恶化变量能由实验室而来虽然研究，有相似的数据真正的结构不在。 一个模型的重要的特征是修改最初预言的设备， 基于出版(认为为 早先) 的数据，使用信息和数据从实际结构直接获得。 可靠性分析适合于这个目的好象它能容易包含附

8、加数据，不断改进达到一个性能目标的可能性。 概念与相似不断改进到达准时的可能性当在一火车上时，有刚刚获得一些额外信息关于操作条件在前面。为一个交叉梁 氯化物暴露区域概率的恶化模型生产的典型的结果， 类似于用图3 显示的领域，图4.认为一个40%的开始的门槛被为第一个检查指定， 模型建议它在8 年之后被承担。 假定检查表明相当较少的腐蚀开始(仅仅这些大约占10%)并且把归于， 由于通过场所调查，对具体的盖子比期望高，性能外形的修正的预言可能被产生。 桥管理行动可能然后被照着改变。说明一个限制怎样说明这个区域的剖面图随以为的条件而变。 恶化模式和契约结合起来限制状态方程。 因此， 组成部分有一个目

9、标每年1 * 10-5的名义上的失效概率， 外形1 建议仅仅17到18 年的寿命，而第2 剖面图建议30到31 年。 当与桥的正常的预期寿命相比较时，两个都是短的寿命。 不过，与这些结果有关系的起始条件以为甲板关节从开始已经失败。 当他们被为完整的建筑物发展时，或者，塑造契约强度的表达方式可能是过于保守的。可靠性分析提供对待不确定的一种合理和一致的框架。 这可能是相似的结构可以被通过超时改变的性能外形比较用的一件有用的管理工具。 结果必须被小心解释，并且经得起常识和工程判别法。 敏感性分析被强烈推荐，并且可能被容易执行。很多数据收集和测试在恶化模型过程中做的解释。 假使有与保持安全，可靠基础结

10、构系统相关的费用，这一凝固的努力以勤奋和组织能产生结实的好处在哪里的一地区。说明一个限制怎样说明这个区域的剖面图随以为的条件而变。 恶化模式和契约结合起来限制状态方程。 因此， 组成部分有一个目标每年1 * 10-5的名义上的失效概率， 外形1 建议仅仅17到18 年的寿命，而第2 剖面图建议30到31 年。 当与桥的正常的预期寿命相比较时，两个都是短的寿命。 不过，与这些结果有关系的起始条件以为甲板关节从开始已经失败。 当他们被为完整的建筑物发展时，或者，塑造契约强度的表达方式可能是过于保守的。可靠性分析提供对待不确定的一种合理和一致的框架。 这可能是相似的结构可以被通过超时改变的性能外形比

11、较用的一件有用的管理工具。 结果必须被小心解释，并且经得起常识和工程判别法。 敏感性分析被强烈推荐，并且可能被容易执行。很多数据收集和测试在恶化模型过程中做的解释。 假使有与保持安全，可靠基础结构系统相关的费用，这一凝固的努力以勤奋和组织能产生结实的好处在哪里的一地区。这项特别的工程专心于加强的混凝土恶化的一个具体的领域，特别是起因于氯化物进入。 氯化物存在于在冬天在英国使用的除冰的盐。 氯离子迁移虽然使凝固，例如以吸收和扩散。 在合适条件下，他们起动加固酒吧腐蚀。 腐蚀机制产生锈。 金属的被增加的体积，由于锈，导致断裂，失效并且具体的盖子的弄碎。 在更迅速和广泛的加固腐蚀里的这结果。说明一个

12、限制怎样说明这个区域的剖面图随以为的条件而变。 恶化模式和契约结合起来限制状态方程。 因此， 组成部分有一个目标每年1 * 10-5的名义上的失效概率， 外形1 建议仅仅17到18 年的寿命，而第2 剖面图建议30到31 年。 当与桥的正常的预期寿命相比较时，两个都是短的寿命。 不过，与这些结果有关系的起始条件以为甲板关节从开始已经失败。 当他们被为完整的建筑物发展时，或者，塑造契约强度的表达方式可能是过于保守的。 如果共同不及格，加强在伸缩接头下面位于的混凝土桥元素特别对氯化物攻击敏感。 在英国的公路高架桥通常由交叉梁直接在伸缩接头下面位于的加强的混凝土组成，(参阅图2)。 很多交叉梁已经遭

13、受严厉的加固腐蚀，失效和弄碎。 一典型例子在3 图让看，加固覆盖在哪里交叉梁有失效。总而言之： 这项工作受到公路办事处的的大力支持而得以顺利进行， 所表示的观点意见仅代表作者的想法，并不一定被公路办事处接受或分享。英文翻译Reliability analysis :a structures management tool for concrete bridgesReinforced concrete structures are susceptible to a variety of deterioration mechanisms, including alkali-thaw action

14、and chloride ingress. Substantial research has been undertaken in relation to these mechanisms and other problems. This has particularly been the case over the last 20 years or so, where the objective has been to identify causes, consequences and develop remediation strategies. This has improved und

15、erstanding of long-term behaviour of reinforced concrete and resulted in the development of techniques to increase deterioration resistance.At present, the most common approach is to act after a problem has been identified, known as re-active maintenance. This may not be the most economic solution s

16、ince, in many cases, maintenance is more costly than preventative treatments. However, owners are often reluctant to pay for preventative treatments before deterioration is apparent. Early application of treatments may not be the optimal solution in the long run. Integrated deterioration and perform

17、ance prediction modeling is essential to pro-actively plan and prioritise inspection, testing and maintenance. This becomes increasingly important as infrastructure ages and justification for maintenance funding becomes increasingly critical. Performance assessment can be achieved through surveys, t

18、esting and formal calculations, ideally based on site data that represent, as accurately as possible, the state of the structure. By integrating predictive deterioration models with assessment tools and performance criteria (at element, structure or group level) it becomes possible to base the maint

19、enance regime on time-dependent performance profiles. This is particularly relevant in the context of whole-wife costing procedures.Substantial research has been undertaken in relation to these mechanisms and other problems. This has particularly been the case over the last 20 years or so, where the

20、 objective has been to identify causes, consequences and develop remediation strategies. This has improved understanding of long-term behaviour of reinforced concrete and resulted in the development of techniques to increase deterioration resistance.At present, the most common approach is to act aft

21、er a problem has been identified, known as re-active maintenance. This may not be the most economic solution since, in many cases, maintenance is more costly than preventative treatments. However, owners are often reluctant to pay for preventative treatments before deterioration is apparent. Early a

22、pplication of treatments may not be the optimal solution in the long run. Integrated deterioration and performance prediction modeling is essential to pro-actively plan and prioritise inspection, testing and maintenance. This becomes increasingly important as infrastructure ages and justification fo

23、r maintenance funding becomes increasingly critical.Reliability analysis has emerged as an important tool in this multi-objective management process, which must take into account safety, functionality and sustainability criteria. In simple terms, the reliability of a structure or a system is the pro

24、bability of achieving a particular performance level. Probability or likelihood is the appropriate measure, since all engineering systems are susceptible to uncertainties, arising from random phenomena and incomplete knowledge. Reliability analysis in structural engineering enables quantification of

25、 uncertainties associated with loading, materials, deterioration, modeling and other factors. These are integrated into a method that estimates the probability of reaching the specified performance level during the service life of a structure. The method is increasingly being used in bridge engineer

26、ing, both for calibration of safety levels in codes and standards and improving and refining assessment methodologies. The purpose of this article is to outline its application in managing bridges susceptible to deterioration.Although data for many deterioration variables can be derived from laborat

27、ory studies, there is an absence of similar data real structures. An important feature of the model is the facility to modify initial predictions, based on published (known as prior) data, using information and data obtained directly from the actual structures. Reliability analysis is appropriate fo

28、r this pursose as if it can readily incorporate additional data, updating the probability of reaching a performance target. The concept is analogous to updating the probability of arriving on time whilst on a train, having just obtain some extra information regarding the operating conditions ahead.

29、Typical results produced by the probabilistic deterioration model for a crossbeam chloride exposure zone, similar to the delaminated area shown in Figure 3,are shown in Figure 4.Assuming a threshold of 40% initiation is specified for the first inspection, the model suggests that it should be underta

30、ken after eight years .Assuming that inspection indicates significantly less corrosion initiation (e.g.only about 10%) and attributed, through site investigations, to concrete cover being higher than expected, a revised prediction of the performance profile may be generated .The bridge management ac

31、tions may then be altered accordingly.Figure 5 illustrates how a limit state profile for this zone changes with assumed conditions. The deterioration model has been integrated with bond limit state equations .Thus, assuming that the component has a target nominal probability of failure of 110-5 per

32、year, profile 1 suggests a lifetime of only 17 to 18 years, whereas Profile 2 suggests 30 to 31 years. Both are short lifetimes when compared with the normal life expectancy of bridges. However, initial conditions relating to these results assume that the deck joint has failed from the outset . Alte

33、rnatively ,the expressions for modelling bond strength may be over-conservative ,as they were developed for intact structures.Substantial research has been undertaken in relation to these mechanisms and other problems. This has particularly been the case over the last 20 years or so, where the objec

34、tive has been to identify causes, consequences and develop remediation strategies. This has improved understanding of long-term behaviour of reinforced concrete and resulted in the development of techniques to increase deterioration resistance.At present, the most common approach is to act after a p

35、roblem has been identified, known as re-active maintenance. This may not be the most economic solution since, in many cases, maintenance is more costly than preventative treatments. However, owners are often reluctant to pay for preventative treatments before deterioration is apparent. Early applica

36、tion of treatments may not be the optimal solution in the long run. Integrated deterioration and performance prediction modeling is essential to pro-actively plan and prioritise inspection, testing and maintenance. This becomes increasingly important as infrastructure ages and justification for main

37、tenance funding becomes increasingly critical. Bridge performance criteriaCurrent UK assessment codes are concerned with ultimate limit states (ULS) and do not explicitly require checking of serviceability limit states (ULS). It is assumed that an existing structure has experienced SLS loads during

38、its life. However, the widely accepted SLS criteria of deflection and cracking do not fully take into account the problems posed by deterioration. Deterioration-based criteria such as rust staining, delamination and spalling need to be considered because they clearly influence bridge performance, bo

39、th functional and financial. These often prove the dominant factor with regard to bridge management strategy. By explicitly considering and specifying performance levels, the engineer is aware of the important deterioration indicators in order to establish the inspection and maintenance regime for t

40、he particular structure/member. These performance levels may change over time, due to changes in function, loading, structure importance etc. for example, the relationship between actual and required performance is conceptualized by the diagram shown in Figure 1. Thus, reliability analysis may be us

41、ed to formulate the probability that performance will exceed that required, thereby estimating the reliability of the structure. The performance measure can be related to safety, functionality or any other appropriate criterion. Modeling chloride-induced deterioration This particular project concent

42、rated on one specific area of reinforced concrete deterioration, specifically arising from chloride ingress. Chlorides are present in de-icing salts used in the UK during winter. Chloride ions migrate though the concrete, e.g. by absorption and diffusion. Under suitable conditions, they initiate rei

43、nforcement bar corrosion. The corrosion mechanism produces rust. The increased volume of the metal, due to the rust, leads to cracking, delamination and spalling of the concrete cover. This results in more rapid and extensive reinforcement corrosion.Reinforced concrete bridge elements located below

44、expansion joints are particularly susceptible to chloride attack if the joint fails. Highway viaducts in the UK typically consist of a reinforced concrete crossbeam directly located below the expansion joint,(see Figure 2).Many crossbeams have suffered severe reinforcement corrosion, delamination an

45、d spalling. A typical example is shown in Figure 3, where the reinforcement cover over the crossbeam has delaminated. A probabilistic deterioration model for reinforced concrete bridge components was developed, taking into account the characteristics of these structures and their environment. It ass

46、umes that both diffusion and absorption play a part in chlotide migration through the concrete, the variability in the quantity of de-icing salts reaching the crossbeam surface and how these quantities vary annually. Typical chloride exposure zones considered for the crossbeams include the: Horizont

47、al surface below a failed expansion joint where water ponding can occur vertical surface below a failed expansion joint surfaces below an intact expansion joint, but exposed to traffic spray etc.Although data for many deterioration variables can be derived from laboratory studies, there is an absenc

48、e of similar data real structures. An important feature of the model is the facility to modify initial predictions, based on published (known as prior) data, using information and data obtained directly from the actual structures. Reliability analysis is appropriate for this pursose as if it can rea

49、dily incorporate additional data, updating the probability of reaching a performance target. The concept is analogous to updating the probability of arriving on time whilst on a train, having just obtain some extra information regarding the operating conditions ahead. Typical results produced by the

50、 probabilistic deterioration model for a crossbeam chloride exposure zone, similar to the delaminated area shown in Figure 3,are shown in Figure 4.Assuming a threshold of 40% initiation is specified for the first inspection, the model suggests that it should be undertaken after eight years .Assuming

51、 that inspection indicates significantly less corrosion initiation (e.g.only about 10%) and attributed, through site investigations, to concrete cover being higher than expected, a revised prediction of the performance profile may be generated .The bridge management actions may then be altered accor

52、dingly.Laboratory and site data are essential for improved deterioration modeling and reliability .Much data collection and test interpretations made in the deterioration models. Given the costs associated with maintaining safe, reliable infrastructure systems, this is an area where a concreted effo

53、rt by industry and organizations could yield substantial benefits.Figure 5 illustrates how a limit state profile for this zone changes with assumed conditions. The deterioration model has been integrated with bond limit state equations .Thus, assuming that the component has a target nominal probabil

54、ity of failure of 110-5 per year, profile 1 suggests a lifetime of only 17 to 18 years, whereas Profile 2 suggests 30 to 31 years. Both are short lifetimes when compared with the normal life expectancy of bridges. However, initial conditions relating to these results assume that the deck joint has f

55、ailed from the outset . Alternatively ,the expressions for modelling bond strength may be over-conservative ,as they were developed for intact structures. Concluding remarksReliability analysis provides a rational and consistent framework for treating uncertainties .It can be a useful management too

56、l with which similar structures can be compared through performance profiles which change over time. The results must be interpreted with care, and stand up to common sense and engineering judgement . Sensitivity analysis is strongly recommended, and can be readily performed. Laboratory and site dat

57、a are essential for improved deterioration modeling and reliability .Much data collection and test interpretations made in the deterioration models. Given the costs associated with maintaining safe, reliable infrastructure systems, this is an area where a concreted effort by industry and organizations could yield substantial benefits. AcknowledgementsThis work was performed with the support of the Highways Agency. The views expressed are those of the authors and are not necessarily shared by the Highways Agency.