MODIFIED SCHEME BASED ON SEMI-ANALYTIC APPROACH FOR COMPUTING NON-PROBABILISTIC RELIABILITY INDEX

A new computation scheme proposed to tackle commensurate problems is devel- oped by modifying the semi-analytic approach for minimizing computational complexity. Using the proposed scheme, the limit state equations, usually referred to as the failure surface, are obtained from transformation of an interval variable to a normalized one. In order to minimize the computational cost, two algorithms for optimizing the calculation steps have been proposed. The monotonicity of the objective function can be determined from narrowing the scope of interval variables in normalized infinite space by incorporating the algorithms into the computational scheme. Two examples are used to illustrate the operation and computational efficiency of the approach. The results of these examples show that the proposed algorithms can greatly reduce the computation complexity without sacrificing the computational accuracy. The advantage of the proposed scheme can be even more efficient for analyzing sophistic structures.

Reliability and Validity of Addiction Severity Index in Drug Users with Methadone Maintenance Treatment in Guizhou Province, China

Objective To evaluate the reliability and validity of the Chinese version of addiction severity index （ASI）-5th version （ASI-C-5）, in illegal drug users receiving methadone maintenance treatment （MMT） in China. Methods One hundred and eighty-six heroin addicts （144 men and 42 women） receivihg MMT at three clinics in Guizhou province, southwest China, were recmited. They were all interviewed with a questionnaire of ASI-C-5 and 35 were re-interviewed at an interval of seven days to assess its test-retest reliability. Results Cronbach＇s alpha for internal consistency of CSs varied from 0.60 to 0.81 in all domains. Test-retest reliability of composite scores （CSs） of ASI-C-5 were satisfactory （r=0.38-0.97）. Based on item analysis and expert＇s suggestions, five items were deleted and one item was modified in ASI-C-5. Criterion validity of ASI-C-5 was found acceptable, as compared to addicts＇ self-rating anxiety scale （SAS） and self-rating depression scale （SDS） （r=0.59 and 0.45） except for social support rating scale （SSRS）. Conclusions ASI-C-5 can be used for heroin addicts receiving MMT with acceptable reliability and validity.

A modified method to calculate reliability index using maximum entropy principle

Routine reliability index method, first order second moment (FOSM), may not ensure convergence of iteration when the performance function is strongly nonlinear. A modified method was proposed to calculate reliability index based on maximum entropy (MaxEnt) principle. To achieve this goal, the complicated iteration of first order second moment (FOSM) method was replaced by the calculation of entropy density function. Local convergence of Newton iteration method utilized to calculate entropy density function was proved, which ensured the convergence of iteration when calculating reliability index. To promote calculation efficiency, Newton down-hill algorithm was incorporated into calculating entropy density function and Monte Carlo simulations (MCS) were performed to assess the efficiency of the presented method. Two numerical examples were presented to verify the validation of the presented method. Moreover, the execution and advantages of the presented method were explained. From Example 1, after seven times iteration, the proposed method is capable of calculating the reliability index when the performance function is strongly nonlinear and at the same time the proposed method can preserve the calculation accuracy; From Example 2, the reliability indices calculated using the proposed method, FOSM and MCS are 3.823 9, 3.813 0 and 3.827 6, respectively, and the according iteration times are 5, 36 and 10 6 , which shows that the presented method can improve calculation accuracy without increasing computational cost for the performance function of which the reliability index can be calculated using first order second moment (FOSM) method.

Reliability-Based Load and Resistance Factors Design for Offshore Jacket Platforms in the Bohai Bay:Calibration on Target Reliability Index

The target reliability index has been effectively used as the best solution to deal with the relationship between the structural safety and the optimal economy in any structural design. However, the target reliability index for offshore jacket platforms based on different sea areas in China has never been calibrated. This paper presents an approach for its calibration, and suggests many kinds of associated load cases. The uncertainties of loads and structural resistance are mainly in- vestigated. The target reliability index for structural components, tubular joints and piles of offshore jacket plaffortns are discussed respectively in detail. Finally, through the calibrated results from the offshore jacket platforms of QK18-1, JZ20-2, SZ36-1 and BZ28-1 in the Bohai Bay, it is proposed to adopt 2.8 as the target reliability index of offshore jacket platforms in the Bohai Bay for a 25-year design period. The results provide significant reference for the design of offshore jacket platforms.

Reliability of Chinese web-based ocular surface disease index questionnaire in dry eye patients:a randomized,crossover study

AIM:To assess the reliability of web-based version of ocular surface disease index in Chinese(C-OSDI)on clinically diagnosed dry eye disease(DE)patients.METHODS:A total of 254 Chinese participants(51%male,129/254;mean age:27.90±9.06 y)with DED completed paper-and web-based versions of C-OSDI questionnaires in a randomized crossover design.Ophthalmology examination and DED diagnosis were performed prior to the participants being invited to join the study.Participants were randomly designated to either group A(paper-based first and webbased second)or group B(web-based first and paper-based second).Final data analysis included participants that had successfully completed both versions of the C-OSDI.Demographic characteristics,test-retest reliability,and agreement of individual items,subscales,and total score were evaluated with intraclass correlation coefficients(ICC),Spearman rank correlation,Wilcoxon test and Rasch analysis.RESULTS:Reliability indexes were adequate,Pearson correlation was greater than 0.8 and ICCs range was 0.827 to 0.982;total C-OSDI score was not statistically different between the two versions.The values of mean-squares fit statistics were very low compared to 1,indicating that the responses to the items by the model had a high degree of predictability.While comparing the favorability 72%(182/254)of the participants preferred web-based assessment.CONCLUSION:Web-based C-OSDI is reliable in assessing DED and correlation with the paper-based version is significant in all subscales and overall total score.Webbased C-OSDI can be administered to assess individuals with DED as participants predominantly favored online assessment.

The stability safety factor calibration based on the reliability index

When the bridge structure stability safety factor of the first type is 4, the research that whether the structure reliability index will reach target reliability index under the more-likely-to-happen collapse situation of the second type is necessary. The stability calculations of the first and the second type are made respectively for single layer and single span rigid frame bridge. Based on the critical load obtained from the stability calculation of the first type, the stability safety factor of the first type is taken as 4, and the first order reliability method is used to program and calculate the reliability index. Then, the load effect under the stability reliability index cal- culation of the first type and the critical load of the second type are employed to calculate the reliability index of the second type. The evaluation of structure stability safety factor is discussed according to reliability index. Based on the discussion above, parameter analysis of the stable critical loads of two types is made, and the in- fluence of critical load change on reliability index is researched. The result shows that stability analysis should identify collapse state; when the stability safety factor of the first type is 4, but the structure has the collapse of the second type, the reliability index cannot be ensured to reach the target reliability index under certain condi- tions.

Target reliability index for serviceability limit state of single piles

The objective is to develop an approach for the determination of the target reliability index for serviceability limit state(SLS) of single piles. This contributes to conducting the SLS reliability-based design(RBD) of piles. Based on a two-parameter,hyperbolic curve-fitting equation describing the load-settlement relation of piles, the SLS model factor is defined. Then, taking into account the uncertainties of load-settlement model, load and bearing capacity of piles, the formula for computing the SLS reliability index(βsls) is obtained using the mean value first order second moment(MVFOSM) method. Meanwhile, the limit state function for conducting the SLS reliability analysis by the Monte Carlo simulation(MCS) method is established. These two methods are finally applied to determine the SLS target reliability index. Herein, the limiting tolerable settlement(slt) is treated as a random variable. For illustration, four load test databases from South Africa are compiled again to conduct reliability analysis and present the recommended target reliability indices. The results indicate that the MVFOSM method overestimates βsls compared to that computed by the MCS method. Besides, both factor of safety(FS) and slt are key factors influencing βsls, so the combination of FS and βsls is welcome to be used for the SLS reliability analysis of piles when slt is determined. For smaller slt, pile types and soils conditions have significant influence on the SLS target reliability indices; for larger slt, slt is the major factor having influence on the SLS target reliability indices. This proves that slt is the most key parameter for the determination of the SLS target reliability index.

A Method for Determining the Reliability Index of a Materiel Subsystem

This paper presents a method for determining the reliability index of a subsystem in the materiel demonstration phase-AHP Failure Rate Method. It fully considers the various factors which influence a subsystem reliability index and solves a difficult problem that puzzles the demonstration personnel.

Reliability and Validity of Chinese Version of the Addiction Severity Index among Drug Users in the Community

Objective To assess the reliability and validity of a new Chinese version of the Addiction Severity Index （ASI-C） in drug users in the community. Methods Three hundred and eighty-one drug users in the community in Chengdu, Sichuan province were recruited. They were interviewed with a questionnaire consisting of the ASI-C revised on the basis of the previous Chinese version and 38 were interviewed for the second time at an interval of 7 days to evaluate test-retest reliability. Results Cronbach＇s c~ coefficients for the internal consistency of the scale varied from 0.49 to 0.86. Test-retest correlation coefficients ranged from 0.50 to 0.93. Criterion validity was found acceptable, as compared with the Symptom Checklist 90 （SCL-90）. Conclusion The ASI-C presented acceptable reliability and validity in a sample of drug users in the community.

Genetic Algorithms of Structural Fuzzy Reliability Index

In this paper the simple generation algorithms are improved. According to the geometric meaning of the structural reliability index, a method is proposed to deal with the variables in the standard normal space. With consideration of variable distribution, the correlation coefficient of the variables and its fuzzy reliability index, the feasibility and the reliability of the algorithms are proved with an example of structural reliability analysis and optimization.

Derivation of Reliability Index Vector Formula for Series System and Its Application

In this study, a reliability index vector formula is proposed for series system with two failure modes in term of the concept of reliability index vector and equivalent failure modes. Firstly, the reliability index vector is introduced to determine the correlation coefficient between two failure modes, and then, the reliability index vector of a series system can be obtained. Several numerical cases and an analysis on offshore platform are performed, and the results show that this scheme provided here has better computational accuracy, and its calculation process is simpler for the series systems reliability calculations compared with the other methods. Also this scheme is more convenient for the engineering applications.

Instantaneous Reliability Index of a Typical Repairable System

A two-state system was taken as an example to show the method that we derived for analyzing the instantaneous reliability index,which was an important issue in the field of reliability.The paper first described the system as an abstract Cauchy problem by choosing suitable operators and state spaces.Then,with the TrotterKato theorem and strong continuous semi-group theorem,the method of solving the instantaneous reliability index of the repairable system was constructed.The convergence of the method was also proved in theory in this paper.To show the effectiveness of this method,some numerical examples were given at the end of the paper.

The solution of minimum reliability index for modified weak point of arbitrary curved beam under pure bending

This paper is based on the fundamental loading model of pure bending and the analytical model of a circular beam element with arbitrary initial deflection. The L.W. Guo solution is modified and generalized according to the elastic theory, and the analytical solution for the stress of the beam element with arbitrary initial deflection under pure bending is derived. Using yield theory of edge strength, an expression for the safety margin of one point in the arbitrary curved beam under pure bending （ACPB） is built. This paper modifies the model for weak points of service structures and establishes a foundation for safe design and inspection of imperfect structures. Also, according to the theory of the method of advanced first-order second-moment（AFOSM） , this paper derives an expression for the reliability index of one point in ACPB. Lastly, it modifies the solution for weak points by solving the minimal reliability index.

Reliability Index of Tall Buildings in Earthquake Zones

The paper develops a reliability index approach to assess the reliability of tall buildings subjected to earthquake loading. The reliability index β model measures the level of reliability of tall buildings in earthquake zones based on their response to earthquake loading and according to their design code. The reliability index model is flexible and can be used for: 1) all types of concrete and steel buildings and 2) all local and international codes of design. Each design code has its unique reliability index β as a magnitude and the interaction chart corresponding to it. The interaction chart is a very useful tool in determining the building drift for the desired level of reliability during the preliminary design of the building members. The assessments obtained using the reliability index approach of simulated, tested, and actual buildings in earthquake zones were acceptable as indicators of the buildings reliability.

基于SPI-RRV指数中国气象干旱及其风险时空演变特征研究

为全面揭示变化环境下我国多维气象干旱特征,耦合气象干旱指数(SPI)和可靠性-回弹性-脆弱性(RRV)指数,提出了一种基于SPI-RRV指数的干旱风险评价方法,定量评价了中国气象干旱及其风险的时空演变特征。结果表明:SPI-RRV指数具有特征稳定和时空可比性强的特点,能够较为准确地评估气象干旱风险时空演变特征;南方平均干旱栅格比、干旱月占比和频次大于北方,湿润区和半湿润区干旱历时短、烈度大,半干旱区和干旱区干旱历时长、烈度相对较小;干旱高风险区转移具有显著年代际变化规律,空间上从西北向西南地区转移。

基于广义超椭球模型的结构非概率可靠性指标

非概率凸集合模型仅需获知结构不确定性的范围或界限来度量结构可靠性,因而适用于小样本不确定性结构工程问题.针对广义超椭球模型,对其非概率可靠性度量问题进行了研究.首先,提出了基于广义超椭球模型的简单非概率可靠性指标,定义为结构功能函数的均值与离差之比,并讨论了该可靠性指标的不一致性问题.其次,为克服上述不一致性问题,提出了一种比例因子非概率可靠性指标,定义为不确定域向外扩大或向内收缩时,失效面与不确定域接触的最小比例因子.最后,通过3个工程算例分析验证了所提非概率可靠性指标的有效性和可行性.

多维平行六面体模型非概率可靠性灵敏度分析

可靠性灵敏度能够反映基本变量分布参数对可靠度的影响程度,为可靠性分析与优化设计提供指导。提出了一种基于多维平行六面体模型的非概率可靠性灵敏度分析方法。首先,给出基本变量域完全位于安全域时采用非概率可靠性指标,而基本变量域与安全域有交集时采用非概率失效度作为可靠性度量的原因。其次,推导结构线性系统的可靠性灵敏度解析式,并进一步探讨所提方法对结构非线性系统的适应性问题。最后,通过3个工程算例验证文中方法有效可行。

考虑多重不确定性因素的可靠性指标计算与备用容量优化

在含高比例可再生能源的电力系统中,考虑多重不确定性因素并实现源荷协调的优化调度是电力系统运行的重要问题.为此,构建了基于多场景的概率性旋转备用优化模型,该模型综合考虑了风电和光伏出力预测误差、负荷预测误差及发电机非计划停运等多重不确定性因素对旋转备用容量的影响,将可再生能源弃电、系统切负荷分别作为特殊的备用资源融入发电日前调度计划,以提高电力系统的经济运行效率.改进了系统可再生能源削减期望和电量不足期望值两个可靠性指标的计算方法,减少了与该指标相关的不等式约束条件,用于提升模型的计算性能.该备用优化模型在兼顾场景多样性的同时,实现了多场景下系统的总成本最优.以改进的IEEE-RTS系统作为算例,验证了所提模型的有效性.算例结果表明,改进的可靠性指标计算方法能够有效降低备用优化模型的求解时间;建立的最优旋转备用优化方法能够实现系统日前旋转备用容量的动态配置,提升系统经济运行水平.

基于特征选择和ELM神经网络的轴承可靠性预测

针对滚动轴承可靠性预测问题,提出了基于特征选择和ELM网络的可靠性预测方法。首先,对振动信号提取特征,构成特征参数初选集;其次,引入单调性、相关性、鲁棒性三个特征评价指标对特征参数初选集进行特征评价,并定义了一种新的限制性指标,得到可以反映轴承退化过程的参数,构成退化特征参数集;再次,对退化特征参数集进行维数约简,构成低维特征向量集;最后,以退化特征参数集和特征向量集分别为输入数据和标签带入ELM网络中做可靠性预测。通过西安交通大学轴承振动信号数据集证明了该方法的有效性。

砌体结构地震风险控制决策方法研究

地震等自然灾害作用下生命安全风险的相关决策会对社会公共安全产生重大的影响,因此,工程结构应将风险限制在合理可接受水平,在经济投资、使用效益和生命安全保护方面达到综合最佳。为了解决“多安全才足够安全”这个问题,首先,根据我国2018年基本国情和经济水平确定生活质量指数(life quality index,LQI),并建立基于LQI的风险可接受准则;其次,对新建砌体结构和加固既有砌体结构进行可靠度分析,采用蒙特卡罗法计算地震作用下砌体结构的失效概率;最后,建立砌体结构的地震风险控制决策方法,并通过实例应用提出新建砌体结构的最优设计方案和加固既有砌体结构的最佳加固策略。结果表明:文中提出的方法对新建砌体结构可靠度指标的要求与规范要求基本吻合;地震作用下多层砌体结构的可接受失效概率为0.001~0.010。