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1.
由于钢筋混凝土连续梁的作用荷载、材料、几何特征等具有随机性,使其荷载效应、抗力也具有随机性。针对钢筋混凝土连续梁受弯承载力可靠性,采用Monte-Carlo （蒙特卡洛）法抽样进行计算,定性分析了荷载效应比、材料强度、楼面荷载类型等对钢筋混凝土连续梁受弯承载力可靠度指标的影响。研究结果表明：随荷载效应比增大,连续梁可靠指标减小;随材料强度增加,连续梁的可靠指标变化不明显;楼面活荷载类型对连续梁可靠指标有影响。 相似文献
2.
目的:编制中学教师工作支持量表,并检验其信度和效度。方法:建构中学教师工作支持的理论模型,并依据该模型编制量表。量表的有效样本为275名中学教师,用因子分析和相关分析考察量表的信度和效度。结果:①量表的Cronbach′sα系数为0.858,分半信度为0.716,重测信度为0.831;②因素分析产生4个因子,共解释55.45%的变异;③与工作敬业量表(WES)的相关为0.50(p<0.01)。结论:中学教师工作支持量表具有较好的信效度,可以用于中学教师获得的工作支持的评定。 相似文献
3.
以某砌石重力坝为例,利用结构可靠度计算方法中的JC法和Monte-Carlo法进行可靠度分析,建立结构功能函数,利用MATLAB数学软件分别对JC法和Monte-Carlo法进行编程计算,得到砌石重力坝的失效概率与可靠度指标.运行结果表明运用MATLAB编程计算精度较高,运行速度较快. 相似文献
4.
Evaluation of Dimensionality in the Assessment of Internal Consistency Reliability: Coefficient Alpha and Omega Coefficients 
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下载免费PDF全文 In the lead article, Davenport, Davison, Liou, & Love demonstrate the relationship among homogeneity, internal consistency, and coefficient alpha, and also distinguish among them. These distinctions are important because too often coefficient alpha—a reliability coefficient—is interpreted as an index of homogeneity or internal consistency. We argue that factor analysis should be conducted before calculating internal consistency estimates of reliability. If factor analysis indicates the assumptions underlying coefficient alpha are met, then it can be reported as a reliability coefficient. However, to the extent that items are multidimensional, alternative internal consistency reliability coefficients should be computed based on the parameter estimates of the factor model. Assuming a bifactor model evidenced good fit, and the measure was designed to assess a single construct, omega hierarchical—the proportion of variance of the total scores due to the general factor—should be presented. Omega—the proportion of variance of the total scores due to all factors—also should be reported in that it represents a more traditional view of reliability, although it is computed within a factor analytic framework. By presenting both these coefficients and potentially other omega coefficients, the reliability results are less likely to be misinterpreted. 相似文献
5.
罗纪彬 《湖南广播电视大学学报》2009,(3):46-49
根据混凝土碳化及其引起的钢筋锈蚀的机理,建立了钢筋混凝土构件的劣化模型。利用Monte Carlo模拟方法分别研究了一般运营和密集运营两种荷载模型下钢筋混凝土桥梁的时变可靠性,讨论了保护层厚度、混凝土强度、钢筋锈蚀损失率对混凝土耐久性的影响。研究表明：在服役过程中,由于大气环境的作用,混凝土碳化、钢筋锈蚀、桥梁结构可靠指标不断降低,混凝土的耐久性能不断下降;混凝土保护层厚度和混凝土抗压强度对可靠度指标的影响明显,而钢筋腐蚀率的影响不是很明显。 相似文献
6.
张树忠 《福建工程学院学报》2016,(3):223-226
应用面向对象高级语言C#和SQL Server 2005数据库,采用风险矩阵法、模糊层次分析法、根本原因分析法、综合决策法、逻辑决策法等方法,开发一套基于RCM技术,能够完成港口门座起重机的基础信息管理,以风险为基础,具有良好目标性的维修决策系统,根据用户选择的影响因素来确定其零部件的维修方式和最佳维修周期,以提高机械设备的可靠性和安全性,为企业提供优化、系统、科学的维修决策支持。 相似文献
7.
施工中钢筋混凝土结构可靠度的分析与控制 总被引：3，自引：0，他引：3
根据钢筋混凝土结构在施工期的特点，对结构在施工期内的抗力和荷载效应的影响因素进行了分析，并提出在施工期保证结构可靠性的一些建议。 相似文献
8.
The current situation and difficulties of the structural system reliability analysis are mentioned. Then on the basis of Monte Carlo method and computer simulation, a new analysis method reduced expanding load method (RELM) is presented, which can be used to solve structural reliability problems effectively and conveniently. In this method, the uncertainties of loads, structural material properties and dimensions can be fully considered. If the statistic parameters of stochastic variables are known, by using this method, the probability of failure can be estimated rather accurately. In contrast with traditional approaebes,RELM method gives a much better understanding of structural failure frequency and its reliability index β is more meaningful. To illustrate this new idea, a specific example is given. 相似文献
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10.
A type of hollow cylinder joints connected with H-shaped beams is proposed for spatial structures. Based on von Mises yield
criterion and perfect elasto-plasticity model, a series of finite element models of the joints is established, in which the
effect of geometric nonlinearity is taken into account. Then mechanical behavior and load-carrying capacity of the joints
were investigated, which were subjected to axial load, in- and out-plane bending moments, and their combinations. The results
show that the ultimate loads of the joints are determined by the maximum displacement. Furthermore, the case of one joint
connected with multiple beams was discussed. Experiments on a set of typical full-scale joints were conducted to understand
the structural behavior and the failure mechanism of joint, and also to validate the finite element models. Finally, the practical
calculation method was established through finite elements analysis (FEA) results and numerical fitting. The results show
that the joints are more ductile and materially economical than welded hollow spherical joints, and the practical calculation
method can provide a reference for direct design and the revision of relevant design codes. 相似文献
11.
由于跨海桥梁的环境效应有别于一般桥梁,正常使用极限状态所对应的目标可靠度也必然不同,因此,基于JCSS模式规范建议了目标可靠度指标分别为1.5,2.0和2.3的跨海桥梁基础结构正常使用极限状态三级可靠度水平,并提出了一种可变荷载系数的标定新方法,即通过各类荷载引起的钢筋拉应力对于混凝土裂缝宽度的贡献率不同建立基于钢筋拉应力的正常使用极限状态方程.最后,依据可靠度计算的校准法,结合具体工程进行了基于目标可靠度的可变荷载频遇值系数和准永久值系数的标定,通过设计实践证明所建议的目标可靠度指标值是合理的,采用的标定新方法是可行的. 相似文献
12.
HE Jian CHENG Lin SUN Yuan-zhang 《浙江大学学报(A卷英文版)》2007,8(3):378-383
Operational reliability evaluation theory reflects real-time reliability level of power system. The component failure rate varies with operating conditions. The impact of real-time operating conditions such as ambient temperature and transformer MVA (megavolt-ampere) loading on transformer insulation life is studied in this paper. The formula of transformer failure rate based on the winding hottest-spot temperature (HST) is given. Thus the real-time reliability model of transformer based on oper- ating conditions is presented. The work is illustrated using the 1979 IEEE Reliability Test System. The changes of operating conditions are simulated by using hourly load curve and temperature curve, so the curves of real-time reliability indices are ob- tained by using operational reliability evaluation. 相似文献
13.
The expansion joints are expected to have movement capacity, bearing capacity for static and dynamic loading, water-tightness, low noise emission and traffic safety. In particular, the failure due to impact loading is the main reason for the observed damages. The problem of dynamic behavior of the expansion joints is so complex that we shall focus our attention on the impact factor for vehicle load that is governed by traffic impact. In order to overcome this difficulty, the cantilever-toothed aluminum joint (finger joint) is one of the promising joints under impact loading. In this study, from the viewpoint of design methodology, numerical studies for impact behavior were conducted for aluminum alloy expansion joints with perforated dowels. The design impact factor for the expansion joints with the perforated dowels against traffic impact loading was examined by using numerical simulations. 相似文献
14.
郑冠群 《深圳职业技术学院学报》2014,(1):24-28
表面组装技术（Surface Mount Technology,SMT）中,焊点是组装电路板的可靠性影响因素之一,而焊点的形态决定了其可靠性．文章应用Surface Evolver软件,采用有限元方法,以能量最小原理为理论依据,对表贴翼形引脚及焊点进行了三维模型的预测．选取无铅焊料作为焊点材料,通过建立初始模型,施加边界约束、体积约束、重力势能约束和表面势能约束,完成翼形引脚焊点三维形态预测． 相似文献
15.
研究了开挖对承载力极限状态(ULS) 、正常使用极限状态(SLS) 和系统可靠度(SYS) 的影响,并基于开挖条件下承载力折减系数分别给出 ULS 可靠度指标、SLS 可靠度指标和 SYS 可靠度指标的计算方法. 研究得出 SLS 承载力和 USL 承载力的比值ξ对 SLS 可靠度和 SYS 可靠度有显著影响,并将这一比值的均值μξ当作随机变量,研究了 SLS 可靠度和 SYS 可靠度. 算例分析表明: 开挖深度和开挖直径对承载力折减系数和可靠度指标有显著影响; 随着开挖深度的增大,可靠度指标有很显著的减小; 当开挖深度较大时,开挖直径对可靠度指标的影响较大. 此外,μξ对 SLY 和 SYS 可靠度指标的影响很大,要更精确地估计μξ,需对μξ进行深入的研究. 相似文献
16.
The National Swimming Center built for the 2008Beijing Olympic Games applies the polyhedron spatialframe structure, which is based on the foam physicstheory[1]. Its simple geometry is a square box of 170m×170 m×29 m. It can hold 17 000 people, theroof o… 相似文献
17.
Anne Arnesen Keith Smolkowski Terje Ogden Monica Melby-Lervåg 《Emotional and Behavioural Difficulties》2018,23(1):39-54
This study investigated the psychometric properties of the Elementary Social Behaviour Assessment (ESBA), a teacher-report measure of students’ social skills and academic engagement adapted for use in Norwegian schools. At two times, 8 weeks apart, 151 teachers rated 793 students in Grades 1–6 on the ESBA and the Social Skills Rating System Teacher’s form (SSRS-T). Exploratory factor analysis with the first assessment suggested one or possibly two factors. Confirmatory factor analysis with the second assessment confirmed the one- or two-factor models but did not offer strong evidence for one over the other. The ESBA demonstrated good to excellent reliability. Strong concurrent and predictive correlations with the SSRS-T established criterion validity. The school and teacher levels explained only a limited amount of the total variance in ESBA scores, suggesting that teachers rate students quite similarly. The Norwegian-adapted ESBA paralleled the reliability and validity evidence from US samples. 相似文献
18.
We describe an investigation of the dynamic behavior of a hydraulically driven crane with a freely suspended payload during luffing and slewing motions. To simplify the task, the two movements are considered separately. Taking into account only one motion at a time, the crane is regarded as a three-link kinematic chain with revolute joints. The forward dynamics problem is solved for a crane with three rotational degrees of freedom, two of which describe the load swinging. In both the cases studied, the links are driven by a torque applied via a hydraulic drive, i.e., a linear actuator for the luffing case and a rack and pinion mechanism for the slewing motion. To compose the set of differential equations for the forward dynamics problem, a method based on a general Newton-Euler algorithm is used. From these simulations the time histories of various parameters, namely the swinging angles, hydraulic pressures, and joint forces, are determined. The results obtained via simulations are confirmed experimentally and a good agreement between the two outputs is observed. The results also show that a hydraulic drive system using fast opening flow direction control valves increases the load swing and imposes extensive inertial forces and problems of fatigue and reliability. 相似文献
19.
周天梅 《内江师范学院学报》2009,24(12):63-66
目的检验中文版嘲笑问卷（Teasing Questionnaire-Revised,TQ-R）的效度和信度．方法对英文版TQ-R问卷进行系统的翻译和评价,并用中文版TQ-R对786名中学生进行测量,对测定结果进行效度和信度分析．结果通过对中文TQ-R问卷因子分析得到5个公因子,28个条目负荷值大于0．4,总方差解释率为47．74％,证实了量表的结构效度．总量表a系数为0．90,5个分量表的a系数在0．65以上;总量表与5个分量表呈显著正相关．结论中文TQ-R问卷可以用于评定我国中学生的嘲笑． 相似文献
20.
Bin Rong Rui Liu Zhenyu Li Changxi Feng Guangchao You Fafitis Apostolos 《天津大学学报(英文版)》2017,23(3):258-266
Finite element analysis and parametric studies were performed to investigate the flexural capacity of the panel zone of diaphragm-through joints between concretefilled square steel tubular columns and H-shaped steel beams.Through the comparisons of failure modes,load–displacement curves,and bearing capacity,it was found that the flexural capacity of the panel zone of diaphragmthrough joints was determined by the tensile action and influence of the web of H-shaped steel beams,and the axial load should be taken into account.The steel tube and the diaphragm were the major parts of the joint that resisted the bending moment.The contribution of in-filled concrete had little influence on the flexural capacity of the panel zone of the joint and could be neglected.According to the results of these numerical studies,a formula that considered the influence of the web of H-shaped steel beams and the axial load was developed based on the yield lines in the diaphragm and the steel tube.The results of the proposed formula were in good agreement with the numerical data of this investigation. 相似文献