钢筋混凝土结构基于耐久性劣化度的可靠性分析

结构耐久性的不足将引发其性能的劣化,并导致结构可靠度的降低。根据已建立的两种劣化度模型及极限状态法,以碳化深度和锈胀开裂两种不同的耐久性劣化度为指标,提出了混凝土结构使用寿命全过程可靠度的计算方法。结合工程实例,以荷载作用下的混凝土结构在碳化环境中的劣化问题为例,构建极限状态函数,基于两种劣化度模型,对其运用可靠度理论进行分析,得到了基于耐久性劣化度的结构可靠度求算方法。研究结果表明：可靠度与结构的混凝土保护层厚度及碳化速率的统计数值或钢筋锈蚀量密切相关。计算方法可为分析在役工程的耐久性提供参考。参14     

混凝土结构全寿命安全经济决策研究

由耐久性不足引起的混凝土结构劣化问题给社会带来了越来越严重的经济负担,日益得到各国工程界和经济界的高度重视,保证结构的安全和经济合理是建筑工程决策的主要问题。讨论了混凝土结构全寿命安全和经济分析的方法,提出了基于可靠性的费用分析方法和考虑耐久性的劣化混凝土结构可靠度评估框架,并讨论了提高建设项目长远经济目标的措施和建议。     

单层厂房排架结构体系可靠度分析

本文在构件截面可靠度研究的基础上，充分考虑了结构的塑性性能、失效截面的相关性，分析了单层厂房钢筋混凝土排架结构的体系可靠度。与现有结构体系可靠度分析方法相比较，本文方法简单、准确、可行。     

人工神经网络在嵌岩支护结构可靠度分析中的应用

针对一般地下施工结构可靠度理论方法的不足，提出人工神经网络结合重要性抽样的Monte Carlo可靠度分析方法，并应用于一特大超深基坑的嵌岩支护结构。分析过程与结果表明，所提的可靠度分析方法高效、准确、实用。     

钢筋混凝土结构考虑耐久性的可靠度研究进展

钢筋混凝土结构的耐久性不足将会引起结构性能的劣化 ,从而使结构的可靠度降低。论述了不同耐久性条件下钢筋混凝土结构可靠度分析的国内外研究现状 ,指出了需进一步研究的问题。     

基于Bayes方法的服役结构时变可靠性分析

阐述了结构时不变可靠度的计算方法,在时不变可靠度分析方法的基础上,提出时变可靠度的分析方法,再引进Bayes方法对可靠度进行了分析,并对Bayes方法在结构可靠度分析中的应用进行了论述,从而使结构可靠度预测更符合实际。     

工程结构可靠度分析方法研究

基于可靠度理论，介绍了工程结构点和结构体系可靠度的各种分析方法，并探讨了各种方法的特点，指出结构体系可靠度的研究是今后可靠度发展的方向。     

基于延寿-减碳目标的混凝土结构耐久性控制策略研究

延长结构服役寿命是减少结构全寿命周期碳排放的有效途径。提出了一种综合考虑混凝土结构服役寿命和碳排放的耐久性控制策略分析方法。基于可靠性理论，考虑混凝土结构耐久性能劣化过程三个阶段的规律，研究不同耐久性控制策略对结构可靠度的影响，建立了基于混凝土结构耐久性控制策略的寿命计算模型和碳排放计算模型，提出了描述结构减碳效果的量化指标。通过比较不同耐久性维护和修复方法的延寿效果和碳排放组成，针对工程案例，分别考虑结构的建成状态和既有状态，计算获得不同耐久性控制策略下的服役寿命和年均碳排放量，对比不同策略的延寿和减碳效果。结果表明，耐久性控制策略最高可延长案例结构约22年的服役寿命，并获得8.76%的减碳收益率，在工程实践中应尽早对混凝土结构采取耐久性控制策略以更好地实现结构延寿-减碳目标。     

概率Pushover分析方法及其在结构体系抗震可靠度评估中的应用

本文结合我国现行的抗震规范 (GBJ 11— 89)和地震作用统计参数 ,提出了结构抗震分析的概率Pushover分析方法。根据结构体系可靠度的特点 ,提出了基于概率Pushover分析的结构体系抗震可靠度评估方法 ,并用重要抽样法检验了所提方法的计算精度。理论分析和算例结果表明 :概率Pushover分析方法是评估结构体系抗震可靠度的简便、实用方法。     

铁路隧道衬砌结构可靠度分析

本文提出一个与地面结构相似的铁路隧道衬砌结构可靠度分析方法．此法是根据铁路隧道现行规范和已有的统计数据拟定的．当然它亦可推广到适用其它规范的情况下．目前，国内外尚没有被广泛接受的隧道支护结构可靠度分析方法，故本文所提方法可以认为是一次有益的赏试．     

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.     

Time-variant reliability profiles for steel girder bridges

Evaluation of existing steel bridges becomes more important due to natural aging, increasing load spectra, deterioration caused by corrosion, and other problems. In the result, bridge structures exposed to aggressive environmental conditions are subjected to time-variant changes of resistance. Therefore, there is a need for evaluation procedures for an accurate prediction of the load carrying capacity and reliability of bridge structures, in order to make rational decisions about repair, rehabilitation, and expected life-cycle costs. The objective of this paper is to develop time-variant reliability models for steel girder bridges. Traditional methods based on deterministic analysis do not reveal the actual load carrying capacity of the structure. The proposed approach is based on reliability analysis of components and structural systems. The study involves the selection of representative structures, formulation of limit state functions, development of load models, development of resistance models for corroded steel girders, development of the reliability analysis method, reliability analysis of selected bridges, and development of the time-dependant reliability profiles including deterioration due to corrosion. The results of the study can be used for a better prediction of the service life of deteriorating steel girder bridges, and development of optimal reliability-based maintenance strategies.     

Reliability evaluation in nonlinear analysis of reinforced concrete structures

Modern building codes provide a basis for development of advanced nonlinear models for analysis and design of reinforced concrete (RC) structures. Application of nonlinear models permits direct evaluation of reliability of the whole structure at the stage of a structural analysis. In this paper a probabilistic method for reliability evaluation of plane frame structures with respect to ultimate limit states is proposed. The method is based on a combination of the nonlinear finite element structural model and the first-order reliability method (FORM). Implementation of the FORM for nonlinear analysis of RC structures is considered. Uncertainties associated with the structural model are taken into account and their influence on structural reliability is examined via sensitivity analysis.     

Reliability-based service life assessment for deteriorating reinforced concrete buildings considering the effect of cumulative damage

Most engineering systems used in maintenance strategies must consider deterioration and seismic structural damage. To identify the effects of deterioration and earthquakes simultaneously on structural performance, this study applies an integral simulation method. Compared with that of previous studies, the feature of the proposed method is its analysis of the time-dependent structural capacity of a deteriorating reinforced concrete (RC) building and the simulation of life-cycle earthquake events within a specified service period, while considering cumulative damage induced by deterioration and earthquakes. In addition, the proposed assessment method is applied to derive the reliability-based service life of a deteriorating RC building located in a region with high seismic hazard. Briefly, for deteriorating RC buildings, the proposed reliability-based service life assessment method provides useful information related to maintenance based on both serviceability and safety.     

Lifetime cost optimization of structures by a combined condition–reliability approach

Cost optimization for the determination of the most effective maintenance strategy of deteriorating structures has recently been used by researchers and accepted by experts. The main reasons for this lie in strict requirements of budgetary efficiency and in reliability requirements for structures. Accessible data directly related to structural performance include the condition state, obtained from generally stipulated visual inspections, and the reliability state, derived from the inspection or monitoring programs combined with numerical computations. In this paper, a novel approach to cost models for condition and reliability profiles is described. Global cost optimization can be achieved by means of multi-objective optimization or by means of a Cost-Optimized Condition-Reliability Profile (COCRP) approach. Since the assessment of structures is under uncertainty, it is essential to embed the COCRP concept in a full probabilistic framework. Probabilistic COCRP computations can be performed, even for complex structures, within a reasonable time by using advanced Monte Carlo Methods such as Latin Hypercube Sampling. The proposed COCRP approach allows realistic and efficient treatment of structures that involve uncertainties and detects the parameters having the most significant effects on lifetime cost.     

Application of endurance time method in seismic assessment of steel frames

In this paper, application of a new dynamic procedure called Endurance Time (ET) method in seismic analysis of steel frames is explained. In this method, structures are subjected to gradually intensifying ground shaking and their performance is assessed based on their response considering relevant design criteria at each intensity level. By considerably reducing the number of time history analyses for assessment of structural response at different intensities, this procedure tends to pave a way for practical performance based design of structures. The accuracy of ET method in predicting the response of structures in linear and nonlinear analysis is investigated by considering a set of steel frames. Different material models consisting of elastic-perfectly plastic, stiffness degrading and strength deteriorating models are considered. Application of ET method in assessment of frames that incorporate fluid viscous dampers as seismic mitigation devices is also demonstrated. It is shown that ET analysis can estimate the results of full response history analysis with reasonable accuracy at different excitation levels. ET analysis results are also shown to be reasonably consistent for different material models. Specific issues that should be considered for a successful ET analysis, including the potential loss of accuracy at highly nonlinear excitation levels are discussed. Capability of ET method in predicting collapse capacity of the studied frames is discussed.     

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.     

既有RC桥梁时变可靠性分析

为了研究构件抗力劣化和车辆荷载对既有RC桥梁服役期间的可靠度影响,首先分析讨论了抗力的衰减模型,并将车辆荷载率视为随机变量。在此基础上,分析了不同的抗力衰减模型和车辆荷载对结构可靠性的敏感性。结果表明,行车道板抗弯失效模式的失效概率最大,车辆荷载对结构可靠性影响较大,抗力按不同的规律衰减导致结构的可靠指标降低趋势表现出不同的规律。     

基于ANSYS软件的大型复杂结构可靠度分析

对基于ANSYS软件的大型复杂结构可靠度计算进行了研究。首先 ,针对一次二阶矩法有时不收敛的情况提出了一种改进方法 ,对两点自适应法拟合失效曲面的算法作了修正 ;然后将结构可靠度计算模块连接到ANSYS软件 ,并对大型复杂结构的失效模式作了简要讨论。最后对某大型国家储备粮库筒仓的顶盖和仓壁结构进行了可靠度分析。     

Reliability analysis with nondestructive inspection

Nondestructive inspection tools are commonly used to inspect structures or structural components with resistance deterioration due to defect size growth. The quality of the tools is mainly defined by the rate of detecting a defect with defect size s, (s), and the accuracy in sizing a detected defect. The uncertainty of sizing a detected defect can be incorporated in limit state functions that include defect size, and a reliability evaluation can be carried out with the efficient first-order reliability method (FORM). The rate of detecting a defect can also be incorporated in the reliability evaluation of an inspected structure or structural component. This is done, in this paper, by introducing a standard normally distributed variate, Z, and defining a limit state function as a function of and (s). Advantages of using this limit state function, rather than using a limit state function based on the actual defect size and the critical defect size distributed according to the rate of detection curve, are discussed. It is shown that one only needs to use the mean rate of defect detection curve to consider the uncertainty in the rate of detection. The incorporation of the uncertainty in rate of detection for reliability updating analysis with inspection results, and for reliability-based selection of optimal inspection and maintenance schedule for resistance deteriorating structures are also presented. The proposed approach is illustrated by two examples in evaluating reliability with inspection information and in selecting an optimal inspection and maintenance schedule by minimizing the probability of time to failure before inspection and before the time at the end of remaining service life.