scholarly journals ANALISIS KEANDALAN PADA STRUKTUR RANGKA BATANG MENGGUNAKAN SECOND ORDER RELIABILITY METHOD (SORM)

2018 ◽  
Vol 6 (2) ◽  
pp. 62-67
Author(s):  
Adriyansyah Adriyansyah
Keyword(s):  
Second Order ◽  
Reliability Method ◽  
Reliability Methods

Untuk menghadapi dunia struktur konstruksi yang semaik modern dan permasalahan desain yang semakin kompleks, seorang ahli struktur dituntut untuk lebih rasional dalam menyelesaikan permasalahan. Ketidakpastian dalam geometri, sifat material, maupun pembebanan harus ditangani lebih rasional. Sehingga konsep desain yang semula menggunakan konsep deterministik sekarang beralih menggunakan konsep probabilistik. Salah satu metode probabilistik yang dapat digunakan yaitu Second Order Reliability Methods (SORM).  Second Order Reliability Methods (SORM) merupakan metode untuk menganalisis keandalan dengan menggunakan indeks keamanan β dalam menentukan peluang kegagalan dari desain suatu struktur konstruksi banguanan. SORM menggunakan deret Taylor orde 2 dalam menyelesaikan fungsi kondisi batas. Berdasarkan hasil analisis, profil baja yang memenuhi kriteria desain yaitu 2˪15x15x3 memiliki keandalan yang tinggi dan memiliki risiko kegagalan yang kecil dimana hasil analisis menunjukkan bahwa pf  < 0.1.  

Complementary Intersection Method for System Reliability Analysis

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Byeng D. Youn ◽  
Pingfeng Wang
Keyword(s):  
Reliability Analysis ◽  
System Reliability ◽  
High Efficiency ◽  
Second Order ◽  
Approximation Formula ◽  
Joint Failure ◽  
System Reliability Analysis ◽  
Reliability Method ◽  
Reliability Methods ◽  
Intersection Method

Although researchers desire to evaluate system reliability accurately and efficiently over the years, little progress has been made on system reliability analysis. Up to now, bound methods for system reliability prediction have been dominant. However, two primary challenges are as follows: (1) Most numerical methods cannot effectively evaluate the probabilities of the second (or higher)–order joint failure events with high efficiency and accuracy, which are needed for system reliability evaluation and (2) there is no unique system reliability approximation formula, which can be evaluated efficiently with commonly used reliability methods. Thus, this paper proposes the complementary intersection (CI) event, which enables us to develop the complementary intersection method (CIM) for system reliability analysis. The CIM expresses the system reliability in terms of the probabilities of the CI events and allows the use of commonly used reliability methods for evaluating the probabilities of the second–order (or higher) joint failure events efficiently. To facilitate system reliability analysis for large-scale systems, the CI-matrix can be built to store the probabilities of the first- and second-order CI events. In this paper, three different numerical solvers for reliability analysis will be used to construct the CI-matrix numerically: first-order reliability method, second-order reliability method, and eigenvector dimension reduction (EDR) method. Three examples will be employed to demonstrate that the CIM with the EDR method outperforms other methods for system reliability analysis in terms of efficiency and accuracy.

scholarly journals Second-order reliability methods: a review and comparative study

2021 ◽  
Author(s):  
Zhangli Hu ◽  
Rami Mansour ◽  
Mårten Olsson ◽  
Xiaoping Du
Keyword(s):  
Performance Metrics ◽  
Order Approximation ◽  
Limit State ◽  
Engineering Application ◽  
Second Order ◽  
State Function ◽  
Most Probable Point ◽  
Reliability Method ◽  
Reliability Methods ◽  
Selection Of

AbstractSecond-order reliability methods are commonly used for the computation of reliability, defined as the probability of satisfying an intended function in the presence of uncertainties. These methods can achieve highly accurate reliability predictions owing to a second-order approximation of the limit-state function around the Most Probable Point of failure. Although numerous formulations have been developed, the lack of full-scale comparative studies has led to a dubiety regarding the selection of a suitable method for a specific reliability analysis problem. In this study, the performance of commonly used second-order reliability methods is assessed based on the problem scale, curvatures at the Most Probable Point of failure, first-order reliability index, and limit-state contour. The assessment is based on three performance metrics: capability, accuracy, and robustness. The capability is a measure of the ability of a method to compute feasible probabilities, i.e., probabilities between 0 and 1. The accuracy and robustness are quantified based on the mean and standard deviation of relative errors with respect to exact reliabilities, respectively. This study not only provides a review of classical and novel second-order reliability methods, but also gives an insight on the selection of an appropriate reliability method for a given engineering application.

Extreme Response Predictions for Jack-Up Units in Second Order Stochastic Waves by FORM

2007 ◽  
Author(s):  
Jo̸rgen Juncher Jensen
Keyword(s):  
Second Order ◽  
Sea State ◽  
First Order ◽  
Reliability Method ◽  
Extreme Response ◽  
Stochastic Waves ◽  
Short Time ◽  
Wave Induced ◽  
Jack Up ◽  
Operational Time

The aim of the present paper is to advocate for a very effective stochastic procedure, based on the First Order Reliability Method (FORM), for extreme value predictions related to wave induced loads. All kinds of non-linearities can be included, as the procedure makes use of short time-domain simulations of the response in question. The procedure will be illustrated with a jack-up rig where second order stochastic waves are included in the analysis. The result is the probability of overturning as function of sea state and operational time.

Reliability Methods for Bimodal Distribution With First-Order Approximation1

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Zhangli Hu ◽  
Xiaoping Du
Keyword(s):  
Probability Density ◽  
Order Approximation ◽  
Limit State ◽  
Random Variables ◽  
Random Variable ◽  
State Function ◽  
First Order ◽  
Reliability Method ◽  
Reliability Methods ◽  
Basic Random Variable

In traditional reliability problems, the distribution of a basic random variable is usually unimodal; in other words, the probability density of the basic random variable has only one peak. In real applications, some basic random variables may follow bimodal distributions with two peaks in their probability density. When binomial variables are involved, traditional reliability methods, such as the first-order second moment (FOSM) method and the first-order reliability method (FORM), will not be accurate. This study investigates the accuracy of using the saddlepoint approximation (SPA) for bimodal variables and then employs SPA-based reliability methods with first-order approximation to predict the reliability. A limit-state function is at first approximated with the first-order Taylor expansion so that it becomes a linear combination of the basic random variables, some of which are bimodally distributed. The SPA is then applied to estimate the reliability. Examples show that the SPA-based reliability methods are more accurate than FOSM and FORM.

Second-Order Reliability Method With First-Order Efficiency

2010 ◽  
Author(s):  
Xiaoping Du ◽  
Junfu Zhang
Keyword(s):  
Limit State ◽  
Saddlepoint Approximation ◽  
Quadratic Function ◽  
Second Order ◽  
State Function ◽  
Limit State Function ◽  
First Order ◽  
Reliability Method ◽  
Order Of Magnitude ◽  
Univariate Function

The widely used First Order Reliability Method (FORM) is efficient, but may not be accurate for nonlinear limit-state functions. The Second Order Reliability Method (SORM) is more accurate but less efficient. To maintain both high accuracy and efficiency, we propose a new second order reliability analysis method with first order efficiency. The method first performs the FORM and identifies the Most Probable Point (MPP). Then the associated limit-state function is decomposed into additive univariate functions at the MPP. Each univariate function is further approximated as a quadratic function, which is created with the gradient information at the MPP and one more point near the MPP. The cumulant generating function of the approximated limit-state function is then available so that saddlepoint approximation can be easily applied for computing the probability of failure. The accuracy of the new method is comparable to that of the SORM, and its efficiency is in the same order of magnitude as the FORM.

Reliability of TLP Tethers Using Evolutionary Strategies

2008 ◽  
Author(s):  
Federico Barranco Cicilia ◽  
Alberto Omar Va´zquez Herna´ndez
Keyword(s):  
Limit State ◽  
Evolutionary Strategies ◽  
Economic Losses ◽  
State Function ◽  
Safety Level ◽  
Reliability Method ◽  
Reliability Methods ◽  
New Codes ◽  
Monte Carlo Importance Sampling ◽  
Von Mises

Tether system is a critical component for the TLPs, since its failure may lead to the collapse of the whole structure involving human lives, economic losses and damages to the environment. Due to this fact, reliability methods have been proposed to design TLP tethers and new codes are being developed to increase their safety level. The objective of this paper is to compare the probability of failure for TLP tethers considering the maximum tension limit state obtained with three methods, which are: a methodology based on Evolutionary Strategies and the Monte Carlo Importance Sampling, the First Order Reliability Method, and the Second Order Reliability Method. Von-Mises failure criterion is used as limit state function for the most loaded tether of a TLP submitted to different sea states. Efficiency of the ES algorithm to find design points and probabilities of failure obtained with the reliability methods are discussed.

Reliability Analysis for Inserts in Sandwich Composites

2011 ◽  
Vol 275 ◽  
pp. 234-238 ◽  
Author(s):  
Biswajit Banerjee ◽  
Brian G. Smith
Keyword(s):  
Sandwich Panels ◽  
Failure Surface ◽  
Failure Criteria ◽  
Sandwich Composites ◽  
Stress Concentrations ◽  
Pull Out ◽  
Reliability Method ◽  
Honeycomb Sandwich ◽  
Load To Failure ◽  
Reliability Methods

Inserts are used to transfer localized loads to structures made of sandwich composites. Stress concentrations near inserts are known to cause failures in sandwich panels. Experimental insert pull-out tests show that the load to failure can vary by 20% between batches of sandwich panels. Clearly, uncertainties in the mechanical properties of core and adhesive potting materials have to be accounted for in the optimal design of inserts in sandwich composites. In this paper, we use an one-dimensional computational model of an insert in a homogenized honeycomb sandwich panel to explore the utility of reliability methods in design. We show that the first-order reliability method (FORM) produces accurate estimates of loads that lead to low failure probabilities. We also observe that FORM is sensitive to the failure criteria and may not converge if the failure surface is not smooth and convex.

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