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Reliability-Based Design Criteria for Infrastructure Systems -A New Look

机译：基础设施系统基于可靠性的设计标准-新外观

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The existing reliability-based codes for structural design must rely on "calibration" in specifying the required level of safety. This means that the safety level underlying a reliability-based design will be the same as that of the current traditional code-based design. In other words, reliability does not contribute to the decision on the required safety level for the design of structures or infrastructure systems. It relies on what is in existing codes of structural design. Proposed is an alternative for the development of reliability-based design in which the decision on the required safety level does not depend on "calibration"; instead, it is based on acceptable risk or risk-averseness. For this purpose, uncertainties are divided into two broad types - namely, the aleatory and the epistemic types. The aleatory type is associated with the variability in the observed information (or data-based), whereas the epistemic type is associated with one's inability to accurately estimate or predict reality (i.e., knowledge-based). The two types of uncertainties, can and should be treated separately; in either case, the same probability principles are required and adopted. The effects of the aleatory type is represented in terms of a failure probability, whereas due to the effects of the epistemic type the relevant failure probability, or safety index, becomes a random variable. Values within this random variable correspond to different confidence levels. To ensure adequate safety level of structures, a high confidence level would be appropriate (e.g., the 90% or 95% confidence). Observe that the mean value of the safety index (obtained with the existing total uncertainty approach) is associated with a 50% confidence level which is obviously too low for ensuring safety of structures; thus, the need for calibration. The proposed approach is illustrated with examples of the design of simple structural elements. Also the safety levels of major infrastructure systems are examined for the purpose of identifying the confidence levels underlying current engineering practice.
机译：现有的基于可靠性的结构设计规范必须在指定所需安全级别时依靠“校准”。这意味着基于可靠性的设计所基于的安全级别将与当前传统的基于代码的设计所基于的安全级别相同。换句话说，可靠性不会影响结构或基础设施系统设计所需的安全级别。它依赖于现有结构设计规范中的内容。对于基于可靠性的设计的开发，提出了一种替代方案，其中对所需安全级别的决定不取决于“校准”；相反，它基于可接受的风险或规避风险。为此，不确定性分为两种大类型-即偶然型和认知型。偶然的类型与观察到的信息的可变性相关（或基于数据），而认知的类型与个人无法准确估计或预测现实的相关性（即基于知识）相关。这两种类型的不确定性可以并且应该分别处理；无论哪种情况，都需要并采用相同的概率原理。偶然类型的影响以失败概率表示，而由于认知类型的影响，相关的失败概率或安全指数成为随机变量。此随机变量中的值对应于不同的置信度。为了确保结构具有足够的安全级别，较高的置信度级别是适当的（例如90％或95％的置信度）。注意，安全指数的平均值（通过现有的总不确定性方法获得）与50％的置信度相关，该置信度显然太低，无法确保结构的安全性；因此，需要进行校准。通过简单结构元素的设计示例说明了所提出的方法。此外，还检查了主要基础设施系统的安全级别，目的是确定当前工程实践基础的置信级别。

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