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1.
传统的蒙特卡罗模拟方法在分析由于参数不确定性修正而引起的可靠度修正问题时效率较低。为此,提出了一种基于蒙特卡罗模拟的高效边坡可靠度修正方法,该方法主要包括2个关键步骤:1)根据参数初始分布利用蒙特卡罗模拟方法计算边坡的失效概率,并输出蒙特卡罗模拟的失效样本;2)利用参数统计特征值修正后的联合概率密度函数和蒙特卡罗模拟失效样本计算修正后边坡的失效概率。以两个边坡问题为例说明了所提方法的有效性。结果表明:所提出的方法在计算修正的失效概率过程中无需重新执行蒙特卡罗模拟,计算过程简单、计算效率高。此外,所提方法能够适用于隐式表达功能函数的边坡可靠度修正问题,并能够有效地解决单变量和多变量修正的边坡可靠度修正问题。  相似文献   

2.
根据车辆荷载效应右截尾分布模型,提出一种基于结构可靠度理论的中、小跨度桥梁限载分析方法。首先以规范规定的车辆荷载效应分布为原始分布,构造右截尾的车辆荷载效应概率密度函数;然后,假定抗力、恒载效应及车辆荷载效应为相互独立的随机变量,建立了考虑车辆荷载效应右截尾分布特征的限载系数反演模型;继而,通过分析车辆荷载效应均值变化对限载系数的影响规律,提出了理想抗力桥梁条件限载系数的确定方法,并讨论了条件限载系数对车辆荷载效应变异系数与分布类型的敏感程度;最后,根据原桥梁规范受弯构件承载能力设计表达式,计算了按原规范设计桥梁的条件限载系数。结果表明,桥梁限载取值仅与设计荷载等级、容许失效概率以及设计采用的活恒载比值有关,而与车辆荷载效应的统计参数关系不大。所提限载分析方法可为中、小跨径桥梁提供具有一致可靠度水平的限载取值。  相似文献   

3.
马君明  李惠  兰成明  刘彩平 《工程力学》2022,39(3):11-22, 63
该文着重研究基于观测信息的结构体系可靠度更新模型及其拒绝抽样算法。基于Bayesian理论建立考虑观测信息的结构体系失效概率更新模型,根据观测信息事件类型建立不等式和等式观测信息条件下随机变量的似然函数并推导其后验概率密度函数;基于观测信息域确定随机变量后验样本的拒绝抽样策略,探究拒绝抽样算法的抽样效率,推导更新后结构体系失效概率估计值及其标准差的计算公式;将上述方法应用于刚架结构发生塑性失效时体系可靠度更新计算。研究表明:考虑观测信息的结构体系条件失效概率更新模型可转化为随机变量后验概率密度在失效域上的积分,构造满足观测信息域的先验样本作为随机变量后验样本的抽样策略是可行的,该抽样策略可以处理多随机变量、多观测信息条件下结构体系可靠度更新;与抗力相关随机变量检测值增大及验证荷载值提高均可以降低更新后结构体系的失效概率,与抗力相关的随机变量还需控制其检测误差的标准差,以降低观测信息的不确定性。  相似文献   

4.
子集模拟法是计算结构动力可靠度的新方法。该文在子集模拟法的基本思想上,适应性的选取子失效域的反应界限,合理的选取建议概率密度函数,应用修正的Metropolis算法产生计算条件失效概率时所需的随机变量样本,给出了所需样本的具体个数,并通过上述关键点总结给出了子集模拟法的具体计算步骤。最后应用子集模拟法首先计算了受平稳高斯白噪声作用的单自由度Duffing体系的失效概率,当确定落入失效域的样本时,需计算结构的非线性反应,该文采用迭代的数值逐步积分法进行计算;随后计算了受平稳高斯白噪声作用的采用三线型恢复力模型的三自由度结构的失效概率,结果表明:子集模拟法计算非线性结构动力可靠度时具有高效及高精度的特点,尤其适用于小失效概率的计算。  相似文献   

5.
灾害荷载下结构体系失效模式的相关性及可靠度计算   总被引:9,自引:0,他引:9  
本文通过引入荷载粗糙度指标,根据有关统计参数讨论了灾害荷载的特性,研究了灾害荷载下结构体系失效模式的相关性及可靠度的近似计算方法,得到了以下结论:灾害荷载下结构体系的失效模式近似完全相关,结构体系可靠度由结构的最弱失效模式决定。  相似文献   

6.
服役桥梁的维修加固需要综合考虑安全和经济的问题,基于服役桥梁的动态可靠度,以后续服役期内收益期望值最大或损失期望值最小为目标函数,对服役桥梁的维修加固决策进行了探讨,利用实际检测数据修正抗力模型,对一座服役期为35年的钢筋混凝土梁桥动态可靠度进行了计算,同时,比较分析了汽车荷载等级的提高和采用不同维护加固措施对后续服役期内动态可靠度的影响。该方法结合工程实际,把失效损失与失效风险相结合,对桥梁结构的维修加固决策有一定的指导作用。  相似文献   

7.
一种高效的结构可靠度近似分析方法   总被引:1,自引:0,他引:1  
李刚  程耿东 《工程力学》2001,(A03):373-378
本文简要讨论了结构的可靠度计算的数值模拟方法,如Monte-Carlo法、响应面和两点近似法;结合结构分析的确定性有限元法及可靠度计算的一次二阶矩法,提出了一种结构可靠度分析的近似方法;算例表明,当荷载的不确定性远大于结构的不确定性时,本文提出的方法满足工程精度要求,从而大大简化了结构可靠度分析过程。  相似文献   

8.
运用随机过程的正交展开方法,将地震动加速度过程表示为由10个左右的独立随机变量所调制的确定性函数的线性组合形式。结合概率密度演化方法和等价极值事件的基本思想,研究了非线性结构的抗震可靠度分析问题。以具有滞回特性的非线性结构为例,对某一多自由度的剪切型框架结构进行了抗震可靠性分析。结果表明:按照复杂失效准则计算的结构抗震可靠度较之结构各层抗震可靠度均低。这一研究为基于概率密度函数的、精细化的抗震可靠度计算提供了新的途径。  相似文献   

9.
钢筋混凝土结构正常使用极限状态可靠性分析   总被引:1,自引:0,他引:1  
唐铁羽  赵国藩 《工程力学》1997,(A02):212-220
本文对钢筋混凝土结构正常使用极限状态(变形、裂缝控制)可靠度分析中的不确定性-随机性、模糊性进行了讨论。对于不同情况,建议了三种可靠度计算模式,指出将失效准则按确定值考虑,实质上是用具有某一阈值λ的水平截集代替模糊子集。正常使用失效准则具有强烈的模糊性,采用“模糊事件概率”来计算失效概率更为合理。  相似文献   

10.
基于模糊综合判定的网壳结构强震失效模式研究   总被引:1,自引:0,他引:1  
为合理判别单层网壳结构在强震下的两类失效模式,指导网壳工程在地震区的实践,该文采用考虑材料损伤累积的荷载域全程分析方法,对单层球面网壳和单层柱面网壳在动力荷载下(包括强震)的响应进行了系统的参数分析。简述了两类失效模式的结构表现及结构响应特征;引入模糊数学中的模糊综合判定理论,确定了网壳结构多项响应因素与模糊失效模式集合的关系,建立了基于模糊综合判定的网壳结构动力失效模式判别模型;通过分析表明:所建立的模型具有准确的判别效果,可对网壳结构在动力荷载下的失效模式进行判别。  相似文献   

11.
This paper presents an assessment of the efficiency of the Kriging interpolation models as surrogate models for structural reliability problems involving time-consuming numerical models such as nonlinear finite element analysis structural models. The efficiency assessment is performed through a systematic comparison of the accuracy of the failure probability predictions based on the first-order reliability method using the most common first- and second-order polynomial regression models and the Kriging interpolation models as surrogates for the true limit state function. An application problem of practical importance in the field of marine structures that requires the evaluation of a nonlinear finite element structural model is adopted as numerical example. The accuracy of the failure probability predictions is characterised as a function of the number of support points, dispersion of the support points in relation to the so-called design point and order of the Kriging basis functions. It is shown with the application problem considered that the Kriging interpolation models are efficient surrogate models for structural reliability problems and can provide significantly more accurate failure probability predictions as compared with the most common polynomial regression models.  相似文献   

12.
为了实现桥梁结构模态参数的智能化在线跟踪识别,提出了一种基于滑窗技术、模糊C均值聚类算法与确定-随机子空间算法的时域识别(SC-CDSI)算法。对桥梁结构的输入信号和输出信号进行加窗划分处理,分析了窗函数、窗口大小及窗口步长的确定标准;将频率、阻尼比及模态振型作为模糊C均值聚类算法的聚类元素完成对稳定图中有效模态的智能化辨识;以某振动台试验桥为参数识别对象,并将所得结果与MIDAS有限元结果作对比分析。结果表明,所提SC-CDSI识别算法可以精确实现桥梁结构频率的在线跟踪智能化识别,且识别的结果具有可靠性。  相似文献   

13.
An essential step in FORM, SORM and importance sampling reliability methods is the determination of the so-called design point. This point is the solution of a constrained optimization problem in the outcome space of the random variables, which is commonly solved by an iterative, gradient-based search algorithm. In solving this problem in the context of non-linear finite element reliability analysis, two serious impediments are encountered: (a) for certain material models, the constraint function may have a discontinuous gradient, leading to failure of the search algorithm to converge. (b) The search algorithm may generate trial points too far in the failure domain, where the finite element code fails to produce a result due to lack of numerical convergence. In this paper, remedying strategies are developed for both impediments. The first impediment is addressed by using smooth or smoothed material models, including a smoothed bi-linear model, a Bouc–Wen model and a generalized plasticity model. This is complemented by a proof that sudden elastic unloading does not give rise to gradient discontinuities. The second impediment is addressed by modifying or introducing search algorithms that prevent the trial points from overshooting into the failure domain. Numerical examples are used to demonstrate the two impediments and effectiveness of the proposed remedies.  相似文献   

14.
A contact algorithm in the context of the combined discrete element (DE) and finite element (FE) method is proposed. The algorithm, which is based on the node-to-surface method used in finite element method, treats each spherical discrete element as a slave node and the surfaces of the finite element domain as the master surfaces. The contact force on the contact interface is processed by using a penalty function method. Afterward, a modification of the combined DE/FE method is proposed. Following that, the corresponding numerical code is implemented into the in-house developed code. To test the accuracy of the proposed algorithm, the impact between two identical bars and the vibration process of a laminated glass plate under impact of elastic sphere are simulated in elastic range. By comparing the results with the analytical solution and/or that calculated by using LS-DYNA, it is found that they agree with each other very well. The accuracy of the algorithm proposed in this paper is proved.  相似文献   

15.
A load space formulation for calculating the failure probability of complex structures for which the limit state functions are implicit is described in this paper. This formulation is used in conjunction with probabilistic finite element (PEE) analysis and employs a directional simulation to calculate the structural reliability. Apart from the advantage that a lower order space is used, the main advantage of the load space formulation proposed in this paper is that the number of inversions of the structural stiffness matrix and/or its gradients with respect to the material property random variables is reduced dramatically when compared with the usual Monte Carlo simulation (MCS) method. When used in a finite element reliability analysis, this procedure can save significant amounts of CPU time. Numerical examples are presented to show the efficiency and accuracy of the proposed approach.  相似文献   

16.
In order to calculate the failure probability of complex structures such as a 2.5D/SiC composites turbine blade and improve the structure safety, a new adaptive model of Response Surface (RS) analysis has been developed in this paper, which can improve the computational efficiency of structural failure problem while ensure the accuracy. The Gaussian Process Regression (GPR) theory was used to establish the RS and reconstruct the performance function of structure. And, an Adaptive Latin hypercube Sampling (ALHS) strategy was adopted in the process of establishing and correcting the RS. Finally the Direct Simulation Monte Carlo(DSMC)was utilized to calculate the failure probability of the performance function replacing the complex structure. Two numerical examples were calculated to validate the accuracy and computational efficiency of the proposed method. Additionally the finite element stress analysis results of 2.5D C/SiC composite turbine blade were used to structural reliability analysis by the proposed method. The approach in this paper provides a new way to evaluate the risk of the complex structures.  相似文献   

17.
模糊结构有限元分析的一种新方法   总被引:11,自引:2,他引:9  
雷震宇  陈虬 《工程力学》2001,18(6):47-53
本文利用信息熵的概念,将模糊变量转变为随机变量,将模糊结构视为随机结构进行处理,从而提出了模糊结构有限元分析的一种新方法。当模糊结构转换的随机变量处于小扰动情况下,利用摄动法得到有限元递归方程组,解之可以得到响应量的均值和方差。  相似文献   

18.
This paper presents a novel methodology for structural reliability analysis by means of the stochastic finite element method (SFEM). The key issue of structural reliability analysis is to determine the limit state function and corresponding multidimensional integral that are usually related to the structural stochastic displacement and/or its derivative, e.g., the stress and strain. In this paper, a novel weak-intrusive SFEM is first used to calculate structural stochastic displacements of all spatial positions. In this method, the stochastic displacement is decoupled into a combination of a series of deterministic displacements with random variable coefficients. An iterative algorithm is then given to solve the deterministic displacements and the corresponding random variables. Based on the stochastic displacement obtained by the SFEM, the limit state function described by the stochastic displacement (and/or its derivative) and the corresponding multidimensional integral encountered in reliability analysis can be calculated in a straightforward way. Failure probabilities of all spatial positions can be obtained at once since the stochastic displacements of all spatial points have been known by using the proposed SFEM. Furthermore, the proposed method can be applied to high-dimensional stochastic problems without any modification. One of the most challenging problems encountered in high-dimensional reliability analysis, known as the curse of dimensionality, can be circumvented with great success. Three numerical examples, including low- and high-dimensional reliability analysis, are given to demonstrate the good accuracy and the high efficiency of the proposed method.  相似文献   

19.
To assess structural system reliability accurately, simulation is often the only feasible method because of dimensionality, highly nonlinear limit states, small failure probability and other factors. However, simulations can be computationally inefficient when the reliability assessment involves finite element analysis and the cost of structural analysis is large. Efficient directional simulation, as well as other simulation techniques, often can be improved in terms of accuracy and efficiency if the sample points are identified by deterministic point sets rather than generated randomly. This article introduces and investigates various deterministic point sets theoretically and experimentally in conjunction with directional simulation, and identifies one particular point set (Fekete point set) as being especially useful in this regard. New test measures are proposed to evaluate the quality and uniformity of point sets, which are essential in preserving the underlying probability distribution. A companion paper presents a point set refinement scheme using neural networks, which is a technique parallel to importance sampling.  相似文献   

20.
This paper presents the stochastic elastic modulus reduction method for system reliability analysis of spatial variance frames based on the perturbation stochastic finite element method (PSFEM) and the local average of a random field. The stochastic responses and reliability index of each element of a structural frame are characterized by the PSFEM and the first-order second-moment method, to properly handle the correlation structures and scale of fluctuation of random fields. A strategy of elastic modulus adjustment for the estimation of system reliability is developed to determine the range and magnitude of elastic modulus reduction, by taking the element reliability index as a governing parameter. The collapse mechanism and system reliability index of a stochastic framed structure are determined through iterative computations of the PSFEM. Compared with the failure mode approaches in traditional system reliability analysis, the proposed method avoids two major difficulties, namely the identification of significant failure modes and estimation of the joint probability of failure modes. The influences of the correlation structure and scale of fluctuation of the random field upon system reliability are investigated to demonstrate the accuracy and computational efficiency of the proposed methodology in system reliability analysis of spatial variance frames.  相似文献   

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