Simplified calculation of airblast variability and reliability-based design load factors for spherical air burst and hemispherical surface burst explosions

2021 ◽  
pp. 204141962110435
Author(s):  
Mark G Stewart
Keyword(s):  
Blast Loading ◽  
Computer Code ◽  
Regression Equations ◽  
Model Errors ◽  
Simplified Approach ◽  
Design Load ◽  
Reliability Based Design ◽  
Codes Of Practice ◽  
Load Factors ◽  
Hemispherical Surface

There can be significant uncertainty and variability with explosive blast loading. Standards and codes of practice are underpinned by reliability-based principles, and there is little reason not to apply these to explosive blast loading. This paper develops a simplified approach where regression equations may be used to predict the probabilistic model of airblast variability and associated reliability-based design load factors (or RBDFs) for all combinations of range, explosive mass and model errors. These models are applicable to (i) hemispherical surface bursts, and (ii) spherical free-air bursts. The benefit of this simplified approach is that the equations can be easily programed into a spreadsheet, computer code or other numerical methods. There is no need for any Monte-Carlo or other probabilistic calculations. Examples then illustrate how model error, range and explosive mass uncertainty and variability affect the variability of pressure and impulse, which in turn affect the damage assessment of residential construction.

Simplified reliability-based load design factors for explosive blast loading, weapons effects, and its application to collateral damage estimation

2021 ◽  
pp. 154851292097773
Author(s):  
Mark G Stewart
Keyword(s):  
Predictive Accuracy ◽  
Simulation Analysis ◽  
Blast Loading ◽  
Residential Building ◽  
Load Factor ◽  
Collateral Damage ◽  
Model Errors ◽  
Damage Estimation ◽  
Simplified Approach ◽  
Structural Resistance

The paper describes a simplified approach to quantifying a reliability-based design load factor (RBDF) for the variability of explosive blast loading. The user can select range and explosive mass variability and model errors to derive RBDFs for pressure and impulse. These algorithms may be easily programmed into a spreadsheet, computer code, or other numerical method. There is a need by military planners to increase the predictive accuracy of collateral damage estimation (CDE) to ensure maximum damage to the target while minimizing harm to nearby civilians. This present paper uses the CDE damage criterion adopted by the USA and NATO to assess damage and safety risks and recommend safe collateral damage distances. Hence, the present paper utilizes RBDFs to simulate collateral damage risks to a hypothetical reinforced concrete residential building from a 2000 lb bomb using the 99th percentile of blast loads, engineering models, and Monte Carlo simulation analysis that considers variabilities of load and resistance. It was found that CDE is sensitive to airblast model errors and variability of structural resistance. It is recommended that these considerations be incorporated into CDE methodology since existing CDE methodology may be non-conservative, resulting in higher risks of collateral damage.

Study of the Effects of Environment in the Fatigue Analysis on Existing LWR as Proposed in USNRC RG 1.207

2009 ◽  
Author(s):  
Eugene Tom ◽  
Milton Dong ◽  
Hong Ming Lee
Keyword(s):  
Fatigue Life ◽  
Correction Factor ◽  
Environmental Effects ◽  
Environmental Parameters ◽  
Computer Code ◽  
Cyclic Behavior ◽  
Simplified Approach ◽  
Asme Code ◽  
Detailed Computer ◽  
Fatigue Evaluation

US NRC Regulatory Guide 1.207 Rev. 0 provides guidance for use in determining the acceptable fatigue life of ASME pressure boundary components, with consideration of the light-water reactor (LWR) environment. Because of significant conservatism in quantifying other plant-related variables (such as cyclic behavior, including stress and loading rates) involved in cumulative fatigue life calculations, the design of the current fleet of reactors is satisfactory. For new plants under design and current operating plants considering applying for License Renewal, the environment effects may need to be considered in the design. RG 1.207 proposes using an environmental correction factor (Fen) to account for LWR environments by correcting the fatigue usage calculated with the ASME “air” curves. The Fen method is presented in NUREG/CR-6909, “Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials”. By definition, Fen is the ratio of fatigue life of the component material at room temperature air environments to its fatigue life in LWR coolant at operating temperature. To incorporate environmental effects into the fatigue evaluation, the fatigue usage is calculated using provisions set forth in Section III of the ASME Code, and is adjusted by multiplying a correction factor. The calculated Fen values are then used to incorporate environmental effects into ASME fatigue usage factor evaluation. Once the environmental correction factors have been determined, the previously calculated allowable number of cycles for each load set pair based on the current Code fatigue design curve can be adjusted to determine the new fatigue usage factors for environmental effects. This paper presents a study of the effect of the Regulatory Guide if it is to be implemented on the current fleet of LWR. A quick assessment of the sensitivity of the various environmental parameters is also included in this paper. The comparison of environmental effects between the simplified approach in this paper and the results with detailed computer analyses, such as Unisont’s propriety computer code UPIPENB (Ref. 4), will be our next research project to be presented in the future conference.

Inclusion of Model Errors in Reliability-Based Optimization

2006 ◽  
Vol 128 (4) ◽  
pp. 936-944 ◽  
Author(s):  
Sankaran Mahadevan ◽  
Ramesh Rebba
Keyword(s):  
Computational Models ◽  
Approximation Error ◽  
Richardson Extrapolation ◽  
Model Errors ◽  
Form Error ◽  
Reliability Based Design Optimization ◽  
Reliability Based Design ◽  
Model Form ◽  
Reliability Based Optimization ◽  
Richardson Extrapolation Method

This paper proposes a methodology to estimate errors in computational models and to include them in reliability-based design optimization (RBDO). Various sources of uncertainties, errors, and approximations in model form selection and numerical solution are considered. The solution approximation error is quantified based on the model itself, using the Richardson extrapolation method. The model form error is quantified based on the comparison of model prediction with physical observations using an interpolated resampling approach. The error in reliability analysis is also quantified and included in the RBDO formulation. The proposed methods are illustrated through numerical examples.

Response of Armour Plate Subjected to Blast Loading Based on Analytical Model of Second Order Single Degree of Freedom

2015 ◽  
Vol 819 ◽  
pp. 387-392
Author(s):  
Ahmad Zaidi Ahmad Mujahid ◽  
Shah Koslan Md Fuad ◽  
Othman Mohd Zaid
Keyword(s):  
Numerical Simulation ◽  
Blast Loading ◽  
Computer Code ◽  
Small Error ◽  
Second Order ◽  
Degree Of Freedom ◽  
Analytical Prediction ◽  
Reliable Technique ◽  
Single Degree Of Freedom ◽  
Single Degree

The rolled homogeneous armour (RHA) plate is commonly used for armoured vehicle skin. Preliminary predictions of the deflections from RHA plate subjected to blast loading is important for establishing guidelines before it is used in vehicle skin. The goal of this work is a reliable technique for predicting the RHA plate response subjected to blast loading, and the empirical result performed by other researchers will be taken as a reference. Based on selected references, a small number of assumptions lead to the developed Single Degree of Freedom (SDOF) idealised models. This paper provides an analytical prediction for the RHA plate response using SDOF in one dimension (1D) approach. The analytical capability was subsequently verified using the non-linear fluid structure interaction (FSI) numerical simulation and the AUTODYN computer code. The midpoint deflections of the RHA plate were taken as the figure of merit. Based on the small error percentage and the support of strong analytical arguments, the second order SDOF analytical approach and numerical simulation using the AUTODYN computer code can be employed as a method of analysis.

Model Error Assessment of Burst Capacity Models for Defect-Free Pipes

2012 ◽  
Author(s):  
W. Zhou ◽  
G. (Terry) Huang
Keyword(s):  
Structural Reliability ◽  
Prediction Models ◽  
Yield Criterion ◽  
Limit State ◽  
Model Error ◽  
Pressure Vessels ◽  
Strain Hardening Exponent ◽  
Model Errors ◽  
Reliability Based Design ◽  
Von Mises

The model errors associated with 19 burst pressure prediction models for defect-free thin-walled pipes are evaluated using a total of 76 full-scale burst test data of perfect pipes and pressure vessels collected from the literature. The considered models are based on the Tresca yield criterion, the von Mises yield criterion, or the average shear stress yield criterion. The probabilistic characteristics of the model error, i.e. the mean, coefficient of variation and best-fit probability distribution, are obtained based on the test-to-predicted ratios. The applicability of an empirical equation for estimating the strain hardening exponent in the burst capacity models is also evaluated. The model errors obtained in this study can be used in the structural reliability analysis of energy pipelines with respect to the limit state of burst of defect-free pipes and will facilitate the reliability-based design and assessment of pipelines.

Application of Reliability Based Design and Assessment to Seismic Evaluations

2010 ◽  
Author(s):  
Maher Nessim ◽  
Nader Yoosef-Ghodsi ◽  
Doug Honegger ◽  
Joe Zhou ◽  
Shanshan Wang
Keyword(s):  
Finite Element ◽  
Probability Distribution ◽  
Natural Gas ◽  
Finite Element Model ◽  
Element Model ◽  
Soil Liquefaction ◽  
Simplified Approach ◽  
Natural Gas Pipelines ◽  
Reliability Based Design ◽  
Ground Deformations

The application of reliability based design and assessment (RBDA) as a basis for seismic evaluations of natural gas pipelines is explored through analysis of a number of representative pipeline examples. To accomplish this, a simplified approach was developed to generate a representative probability distribution of permanent ground deformations due to soil liquefaction. An idealized pipeline alignment through a liquefiable layer under a river was defined, and a number of cases representing NPS12 and NPS36 pipelines in classes 1, 2 and 3 were analyzed using a finite element model. The probability of exceeding the strain limits for pipe body and girth weld were calculated and compared to the reliability targets. The results were used to identify diameter and class combinations that can meet the reliability targets, and to make preliminary conclusions regarding the viability of using RBDA for seismic evaluations.

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