Structural reliability theory is concerned with the rational treatment of uncertainties in structural engineering and with the methods for assessing the safety and serviceability of civil engineering and other structures. It is a subject which has grown rapidly during the last decade and has evolved from being a topic for academic research to a set of well-developed or developing methodologies with a wide range of practical applications.
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结构可靠性理论与合理地处理结构工程中不确定性因素有关，也与评价土木工程结构和其他结构的安全性和适用性的方法有关。结构可靠性理论是在最近十年中迅速发展起来的一门学科，它已经从学术研究的课题发展成为在实际中广泛应用的，比较可行的一整套方法。
Uncertainties exist in most areas of civil and structural engineering and rational design decisions cannot be made without modelling them and taking them into account. Most loads and other structural design parameters are rarely known with certainty and should be regarded as random variables or stochastic processes, even if in design calculations they are eventually treated as deterministic. Some problems such as the analysis of load combinations cannot even be formulated without recourse to probabilistic reasoning.
大多数土木工程领域中都存在着不确定性因素，若不将它们模型化并加以考虑，就不可能有合理的设计决策。大多数的荷载和结构的其他设计参数几乎都不是确定性的量，它们都应该被看作是随机变量或随机过程，即使在设计的计算中最后是按确定性的量处理的。像荷载组合分析这一类问题，如果不依赖于概率推理，甚至连公式也列不出来。
Until fairly recently there has been a tendency for structural engineering to be dominated by deterministic thinking, characterized in design calculations by the use of specified minimum material properties, specified load intensities and by prescribed procedures for computing stresses and deflections. This deterministic approach has almost certainly been reinforced by the very large extent to which structural engineering design is codified and the lack of feedback about the actual performance of structures. For example, actual stresses are rarely known, deflections are rarely observed or monitored, and since most structures do not collapse the real reserves of strengths are generally not known. In contrast, in the field of hydraulic systems, much more is known about the actual performance of, say, pipe networks, weirs, spillways etc., as their performance in service can be relatively easily observed or determined.
直到最近，依然存在着用确定性的思想支配结构工程的倾向，其特征是在设计的计算中利用规定的最低材料性能、规定的荷载强度和特定的步骤来计算应力和挠度。由于结构工程设计已编辑成规范，而且缺乏结构实际性能反馈，这无疑在很大程度上加强了这种确定性方法的应用。例如，实际的应力几乎是不知道的，挠度很难观测或监视，而且由于大多数结构不会毁坏，实际的强度储备一般是不知道的。反之，在水力学系统领域中，例如管路网络，堤坝和溢洪道等的实际性能大多数是知道的，因为它们在使用中的性能比较容易观测或确定。
Most structural design is undertaken in accordance with codes of practice, which in many countries have legal status, meaning that compliance with the code automatically ensures compliance with the relevant clauses of the building laws. Structural codes typically and properly have a deterministic format and describe what are considered to be the minimum standards for design, construction and workmanship for each type of structure. Most codes can be seen to be evolutionary in nature, with changes being introduced or major revisions made at intervals of 3-10 years to allow for; new types of structural form, the effects of improved understanding of structural behaviour, the effects of changes in manufacturing tolerances or quality control procedures, a better knowledge of loads, etc.
大多数的结构是按照实用的规范进行设计的，这些规范在许多国家有着法律上的地位，这意味着遵照规范就自动遵循了建筑法令的有关条款。结构规范通常有标准的确定格式，并对各种结构的设计、施工和工程质量应当具有的最低标准作了描述。可以认为，大多数规范实质是在发展的，考虑到新型结构的出现，对结构性能的进一步了解，制造的容许偏差或质量控制方法的变化，对荷载的进一步了解等，每隔3～10 年就要对规范作一些修改或作出重大的修订。
The lack of information about the actual behaviour of structures combined with the use of codes embodying relatively high safety factors can lead to the view, still held by some engineers as well as by some members of the general public, that absolute safety can be achieved. Absolute safety is of course unobtainable; and such a goal is also undesirable, since absolute safety could be achieved only by deploying infinite resources.
由于缺乏有关结构的实际性能资料，加之使用安全系数比较高的规范，从而使得一些工程师及某些公众仍然坚持认为绝对安全是可以达到的。绝对安全当然是不可能得到的；这样的目标也是不符合需要的，因为绝对安全只有调用无限多的资源才能达到。
It is now widely recognized, however, that some risk of unacceptable structural performance must be tolerated. The main object of structural design is therefore to ensure, at an acceptable level of probability, that each structure will not become unfit for its intended purpose at any time during its specified design life. Most structures, however,have multiple performance requirements,commonly expressed in terms of a set of serviceability and ultimate limit states, most of which are not independent; and thus the problem is much more complex than the specification of just a single probability.
但是，现在普遍认为，必须容许不令人满意的结构性能所造成的某种风险。因此，结构设计的主要目标是，在可接受的概率水平上，保证每一结构在规定的设计使用期间内能够满足预期的用途。然而，大多数结构具有多种性能要求，这些要求通常由一组适用性和主要的极限状态来表示，它们大多数不是相互独立的；因此，这个问题比仅仅是一种可能性的情况要复杂得多。
There is a need for all structural engineers to develop an understanding of structural reliability theory and for this to be applied in design and construction, either indirectly through codes or by direct application in the case of special structures having large failure consequences, the aim in both cases being to achieve economy together with an appropriate degree of safety. The subject is now sufficiently well developed for it to be included as a formal part of the training of all civil and structural engineers, both at undergraduate and post-graduate levels. Courses on structural safety have been given at some universities for a number of years.
所有的结构工程师都需要了解结构可靠性理论，并把它应用到设计和施工中去，无论是通过规范间接应用它，还是对具有严重破坏后果的特殊结构直接应用它，两者都要达到既经济又具有适当安全度的目的。日前，这门学科正良好地得到充分发展，它已经被列为土木和结构工程师在大学和研究生阶段正式的学习内容。许多年来，一些大学已经开设了结构安全制度课程。
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