Calibration of Partial Safety Factors Through the Inverse FORM Method

2007 ◽  
Author(s):  
Francisco L. Silva-Gonza´lez
Keyword(s):  
Computational Cost ◽  
Calibration Method ◽  
Structural System ◽  
Safety Factors ◽  
Suction Caisson ◽  
Design Point ◽  
Inverse Form ◽  
Partial Safety Factors ◽  
Calibration Techniques ◽  
Form Approach

A calibration method which uses the so-called inverse FORM approach is proposed. The objective is to find the design point on a hypersphere in U-space, whose radius is the target reliability index, which maximizes the response that the structural system must withstand. Once the design point is determined, the safety factors can be calculated. It is demonstrated that the computational cost of the proposed method is less than the computational cost of traditional calibration techniques. The proposed method is illustrated by means of three examples: parabolic, Eurocode and suction caisson design equations.

Corrosion Margins for Redundant Ship Structures

2018 ◽  
Author(s):  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Differential Equation ◽  
Degradation Process ◽  
Step Function ◽  
Order System ◽  
Safety Factors ◽  
Ship Structures ◽  
Degradation Model ◽  
Corrosion Depth ◽  
First Order ◽  
Partial Safety Factors

The work presented here analyses the structural corrosion degradation of two sets of corrosion depth measurements collected with a one-decade difference. The corrosion degradation process is associated to a first order system, subjected to a sudden disturbance, where a step function is used as an input to define the solution of the differential equation of this system leads to the exponential corrosion degradation model as developed earlier. Corrosion margins of redundant ship structures with serious consequences of failure are derived and several conclusions related to the new trend in the ageing structures are presented and discussed. Partial safety factors with respect to the corrosion environment and corrosion margins are developed that can be used in the design, avoiding a complex probabilistic analysis.

scholarly journals Non-destructive Dielectric Measurements and Calibration for Thin Materials Using Waveguide-Coaxial Adaptors

2014 ◽  
Vol 14 (1) ◽  
pp. 16-24 ◽  
Author(s):  
K. Y. You ◽  
Z. Abbas ◽  
M. F. A. Malek ◽  
E. M. Cheng
Keyword(s):  
Calibration Method ◽  
Calibration Procedure ◽  
Reflection Coefficients ◽  
Dielectric Measurements ◽  
Finite Samples ◽  
Open Standard ◽  
Rectangular Waveguides ◽  
Standard Values ◽  
Calibration Techniques ◽  
Non Destructive

Abstract This paper focuses on the calibration of apertures for rectangular waveguides using open-short-load (OSL) standards and transmission-line (TL) approaches. The reflection coefficients that were measured using both calibration techniques were compared with the coefficients acquired using the thru-reflect-line (TRL) method. In this study, analogous relationships between the results of OSL calibration and TL calibration were identified. In the OSL calibration method, the theoretical, open-standard values are calculated from quasi-static integral models. The proposed TL calibration procedure is a simple, rapid, broadband approach, and its results were validated by using the OSL calibration method and by comparing the results with the calculated integral admittance. The quasi-static integral models were used to convert the measured reflection coefficients to relative permittivities for the infinite samples and the thin, finite samples

Partial safety factors for laminated glass

2019 ◽  
Vol 103 (4) ◽  
pp. 2741-2756 ◽  
Author(s):  
Antonio Bonati ◽  
Gabriele Pisano ◽  
Gianni Royer Carfagni
Keyword(s):  
Laminated Glass ◽  
Safety Factors ◽  
Partial Safety Factors

Load and Resistance Factors for Progressive Collapse Resistance Design of Reinforced Concrete Building Structures

2011 ◽  
Vol 255-260 ◽  
pp. 338-344 ◽  
Author(s):  
Ying Wang ◽  
Feng Lin ◽  
Xiang Lin Gu
Keyword(s):  
Reinforced Concrete ◽  
Progressive Collapse ◽  
Building Structures ◽  
Safety Factors ◽  
Ultimate State ◽  
Resistance Factors ◽  
Collapse Resistance ◽  
Load And Resistance Factors ◽  
Load Effects ◽  
Partial Safety Factors

Due to the absence of provision for the load and resistance factors in design codes in China, designers often quote the provisions which are given in criterion or guidance of other countries such as USA. However, the partial safety factors of the load are various in different criterions. Based on the reliability theory, the load and resistance factors for progressive collapse resistance design of building structures were determined in this study. Firstly the simplified format of design expression in the ultimate state was obtained according to the expression in routine structural design. Then the failure probability of a structure during design reference period was taken as the sum of the probability of all incompatible failure events in this period, and the objective reliability index of the structure could be obtained. Finally using trial-and-error procedure and JC method, reliability analysis was performed for structural members to obtain the partial safety factors of load effects and resistance and the coefficient for combination value of load effects in design expression in the ultimate state. In this paper the load and resistance factors for progressive collapse resistance design of reinforced concrete structures subjected to blast was calculated as an example, and the recommendation values were given for the application at last.

Partial Safety Factors Assessment of Pipes With a Circumferential Surface Flaw

2010 ◽  
Author(s):  
Hideo Machida ◽  
Hiromasa Chitose ◽  
Manabu Arakawa
Keyword(s):  
Fracture Resistance ◽  
Design Method ◽  
Limit State ◽  
Surface Flaw ◽  
Flaw Size ◽  
Material Strength ◽  
State Function ◽  
Safety Factors ◽  
Related Parameter ◽  
Partial Safety Factors

This paper describes the evaluation of partial safety factors (PSF’s) for parameters related to flaw evaluation of pipes which have a circumferential surface flaw, and proposes the important matter which should be pay attention in the setup of the safety factors used in flaw evaluation. PSF’s were evaluated considering randomness of flaw size, a fracture resistance curve (J-R curve) and applied loads using load and resistance factor design method (LRFD). The limit state function is expressed by fracture resistance (resistance-related parameter) and applied J integral (load-related parameter). The measure parameters in the reliability assessment are the flaw size and the J-R curve, and PSF’s of them are larger than those of applied loads. Since the material properties used in the flaw evaluation are generally set to the engineering lower limit of their variation (e.g., 95% lower confidence limit), variation of the flaw size is considered to have important role on flaw evaluation. Therefore, when setting up the safely factors used in Rules on Fitness-for-Service (FFS), it is necessary to take into consideration not only the influence of variation of loads or material strength but the influence of variation of flaw size.

Research on Design Reference Period and Structural Design Method

2011 ◽  
Vol 368-373 ◽  
pp. 2364-2368
Author(s):  
Jia Nian He ◽  
Zhan Wang
Keyword(s):  
Structural Design ◽  
Reliability Index ◽  
Design Method ◽  
Structure Design ◽  
Reference Period ◽  
Building Structure ◽  
Safety Factors ◽  
Importance Factor ◽  
Partial Safety Factors

In structure design, for expressions with partial safety factors, partial safety factors and nominal value of loads are calculated based on the presupposition that the design reference period is 50 years. When the design reference period is not 50 years, it would cause unclear reliability of building structure by using expressions with partial safety factors following correlative codes yet. It may lead to hidden dangers in that way. In order to derive expressions with partial safety factors suitable for any design reference period, two useful methods are shown in this paper, modification of partial safety factors and modification of importance factor of structures. From results of analysis, we get the conclusions that it can assure the reliability index of the expression using the method of modification of partial safety factors, and the method of modification of importance factor of structures is very simple, but cannot assure the reliability index of the expression.

Analysis of the Partial Safety Factor Method Using Probabilistic Techniques

2010 ◽  
Author(s):  
B. A. Lindley ◽  
P. M. James
Keyword(s):  
Probabilistic Method ◽  
Probability Of Failure ◽  
Safety Factors ◽  
First Order Reliability Method ◽  
First Order ◽  
Target Probability ◽  
Reliability Method ◽  
Input Parameters ◽  
Partial Safety Factors ◽  
Hand Calculation

Partial Safety Factors (PSFs) are scaling factors which are used to modify the input parameters to a deterministic fracture mechanics assessment in order to consider the effects of variability or uncertainty in the values of the input parameters. BS7910 and SINTAP have adopted the technique, both of which use the First Order Reliability Method (FORM) to derive values for PSFs. The PSFs are tabulated, varying with the target probability of failure, p(F), and the Coefficient of Variance (COV) of the variable. An accurate assessment of p(F) requires a probabilistic method with enough simulations. This has previously been found to be time consuming, due to the large number of simulations required. The PSF method has been seen as a quick way of calculating an approximate, conservative value of p(F). This paper contains a review of the PSF method, conducted using an efficient probabilistic method called the Hybrid probabilistic method. The Hybrid probabilistic method is used to find p(F) at a large number of assessment points, for a range of different PSFs. These p(F) values are compared to those obtained using the PSF method. It is found that the PSF method was usually, and often extremely, conservative. However there are also cases where the PSF method was non-conservative. This result is verified by a hand calculation. Modifications to the PSF method are suggested, including the establishment of a minimum PSF on each variable to reduce non-conservatisms. In light of the existence of efficient probabilistic techniques, the non-conservatisms that have been found in the PSF method, coupled with the impracticality of completely removing these non-conservatisms, it is recommended that a full probabilistic assessment should generally be performed.

Fatigue Design Margin Evaluation for Carbon and Low-Alloy Steels by Reliability-Based Load and Resistance Factor Method

2011 ◽  
Author(s):  
Masahiro Takanashi ◽  
Makoto Higuchi ◽  
Junki Maeda ◽  
Shinsuke Sakai
Keyword(s):  
Applied Stress ◽  
Limit State ◽  
State Function ◽  
Low Alloy Steels ◽  
Limit State Function ◽  
Safety Factors ◽  
Fatigue Data ◽  
Alloy Steels ◽  
Partial Safety Factors ◽  
Two Parameters

This paper discusses the margins of the design fatigue curve in the ASME Boiler and Pressure Vessel Codes Section III from a reliability analysis point of view. It is reported that these margins were developed so as to cover uncertainties of fatigue data scatter, size effect, and surface condition[1], but the reasons for them remain unclear. In order to investigate the physical implications of the design margin, a probabilistic approach is taken for the collected fatigue data of carbon and low-alloy steels. In this approach, these three parameters are treated as random variables, and an applied stress is also taken into consideration as a random variable. For the analysis, to begin with, a limit state function for fatigue is proposed. Next, reliability index contours of the design fatigue curves for carbon and low-alloy steels are obtained based on the proposed limit state function. The contours indicate that the margins 2 on stress and 20 on life do not provide equal reliability. The margin 20 on life is more conservative and the margin became a minimum near intersections of the design curves with margins 2 on stress and 20 on life. For practical applications, the partial safety factors (PSF) for the target reliability are computed for all materials and several levels of coefficients of variation (COV) of the applied stress. A sensitivity analysis of the PSFs clarifies that only two parameters, the strength (or the life) and the applied stress, are predominant. Thus, the partial safety factors for these two parameters are proposed in a tabular form.

A Partial Safety Factor Method for System Reliability Prediction With Outsourced Components

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Zhengwei Hu ◽  
Xiaoping Du
Keyword(s):  
System Reliability ◽  
Joint Probability ◽  
System Level ◽  
Safety Factors ◽  
Component Reliability ◽  
Reliability Method ◽  
Component Supplier ◽  
Partial Safety Factors ◽  
Joint Probability Density ◽  
Probability Density Function Pdf

System reliability is usually predicted with the assumption that all component states are independent. This assumption may not accurate for systems with outsourced components since their states are strongly dependent and component details may be unknown. The purpose of this study is to develop an accurate system reliability method that can produce complete joint probability density function (PDF) of all the component states, thereby leading to accurate system reliability predictions. The proposed method works for systems whose failures are caused by excessive loading. In addition to the component reliability, system designers also ask for partial safety factors for shared loadings from component suppliers. The information is then sufficient for building a system-level joint PDF. Algorithms are designed for a component supplier to generate partial safety factors. The method enables accurate system reliability predictions without requiring proprietary information from component suppliers.

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