A probabilistic approach to the limit state of centrally loaded thin-walled columns

2001 ◽  
pp. 739-746
Author(s):  
Z. Kala ◽  
J. Kala ◽  
B. Teplý ◽  
M. Škaloud
Keyword(s):  
Limit State ◽  
Probabilistic Approach ◽  
Thin Walled

scholarly journals Comprehensive analysis of the strength and safety of potentially hazardous facilities subject to uncertainties

Dependability ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 47-56
Author(s):  
N. A. Makhutov ◽  
D. O. Reznikov
Keyword(s):  
Human Error ◽  
Human Factor ◽  
Structural Strength ◽  
Limit State ◽  
Probabilistic Approach ◽  
Deterministic Approach ◽  
Target Values ◽  
Load Carrying ◽  
Standard Value ◽  
High Level

Aim. This paper aims to compare the two primary approaches to ensuring the structural strength and safety of potentially hazardous facilities, i.e. the deterministic approach that is based on ensuring standard values of a strength margin per primary limit state mechanisms, and the probabilistic approach, under which the strength condition criterion is the nonexceedance by the target values of probability of damage per various damage modes of the standard maximum allowable values. . The key problem of ensuring the structural strength is the high level of uncertainties that are conventionally subdivided into two types: (1) the uncertainties due to the natural variation of the parameters that define the load-carrying ability of a system and the load it is exposed to, and (2) the uncertainties due to the human factor (the limited nature of human knowledge of a system and possibility of human error at various stages of system operation). The methods of uncertainty mitigation depend on the approach applied to strength assurance: under the deterministic approach the random variables “load” and “carrying capacity” are replaced with deterministic values, i.e. their mathematical expectations, while the fulfillment of the strength conditions subject to uncertainties is ensured by introducing the condition that the relation of the mathematical expectation of the loadcarrying capacity and strength must exceed the standard value of strength margin that, in turn, must be greater than unity. As part of the probabilistic approach, the structural strength is assumed to be ensured if the estimated probability of damage per the given mechanism of limit state attainment does not exceed the standard value of the probability of damage.Conclusions. The two approaches (deterministic and probabilistic) can be deemed equivalent only in particular cases. The disadvantage of both is the limited capability to mitigate the uncertainties of the second type defined by the effects of the human factor, as well as the absence of a correct procedure of accounting for the severity of consequences caused by the attainment of the limit state. The above disadvantages can be overcome if risk-based methods are used in ensuring structural strength and safety. Such methods allow considering uncertainties of the second type and explicitly taking into consideration the criticality of consequences of facility destruction.

Development of Fitness-for-Service Standard for Pressure Equipment With Metal Loss Based on Reliability

2015 ◽  
Author(s):  
Takuyo Kaida ◽  
Shinsuke Sakai
Keyword(s):  
High Pressure ◽  
Structural Integrity ◽  
Limit State ◽  
Probabilistic Approach ◽  
Metal Loss ◽  
Assessment Procedure ◽  
Rational Decision ◽  
Loss Assessment

Concern about probabilistic approach for Fitness-For-Service (FFS) assessment has been growing over the last several years. The FFS assessment based on reliability helps to make a rational decision as to whether to run or repair the equipment. High Pressure Institute of Japan (HPI) formed a committee to develop a HPI FFS standard that can be used for pressure equipment with metal loss. This new standard provides an assessment procedure to evaluate structural integrity of components with metal loss based on reliability. This paper introduces the assessment procedure which is standardized and under preparation for publication, and the technical backgrounds. The standard provides information about limit state of pressure equipment, probabilistic properties of basic variables and target reliability. Probabilistic approach can be applied easily to metal loss assessment by using the standard.

scholarly journals The Evaluation Of Algorithms For Determination Of The Reliability Index

2015 ◽  
Vol 61 (3) ◽  
pp. 133-147 ◽  
Author(s):  
A. Dudzik ◽  
U. Radoń
Keyword(s):  
Reliability Index ◽  
Limit State ◽  
Probabilistic Approach ◽  
Random Variables ◽  
Numerical Procedure ◽  
Vertical Displacement ◽  
Design Parameters ◽  
State Function ◽  
Structural Failure

AbstractThe study deals with stability and dynamic problems in bar structures using a probabilistic approach. Structural design parameters are defined as deterministic values and also as random variables, which are not correlated. The criterion of structural failure is expressed by the condition of non-exceeding the admissible load multiplier and condition of non-exceeding the admissible vertical displacement. The Hasofer-Lind index was used as a reliability measure. The primary research tool is the FORM method. In order to verify the correctness of the calculations Monte Carlo and Importance Sampling methods were used. The sensitivity of the reliability index to the random variables was defined. The limit state function is not an explicit function of random variables. This dependence was determined using a numerical procedure, e.g. the finite element methods. The paper aims to present the communication between the STAND reliability analysis program and the KRATA and MES3D external FE programs.

scholarly journals Limit State Analyses in Design of Thin-Walled Marine Structures: Some Aspects on Length-Scales

2018 ◽  
Author(s):  
Jani Romanoff ◽  
Heikki Remes ◽  
Petri Varsta ◽  
Bruno Reinaldo Goncalves ◽  
Ingrit Lillemäe-Avi ◽  
...  
Keyword(s):  
Limit State ◽  
Plate Thickness ◽  
Length Scale ◽  
Marine Structures ◽  
Structural Element ◽  
Limit States ◽  
Strongly Coupled ◽  
Marine Industry ◽  
Non Linear ◽  
Thin Walled

Present paper gives an overview of the factors that affect the strength and structural design of advanced thin-walled marine structures with reduced plate thickness or alternative topologies to those used today in marine industry. Due to production-induced initial deformations and resulting geometrical non-linearity, the classical division between primary, secondary and tertiary responses becomes strongly coupled. Volume-averaged, non-linear response of structural element can be used to define the structural stress strain relation that enables analysis at the next, larger, length scale. This, today’s standard homogenization process needs to be complemented with localization, where the stresses are assessed at the details, such as welds for fatigue analysis. Due to this, the production-induced initial distortions need to be considered with high accuracy. Another key question is the length-scale interaction in terms of continuum description. Non-classical continuum mechanics are needed when consequtive scales are close. Strain-gradients are used to increase the accuracy of the kinematical description of beams, plates and shells. The paper presents examples of stiffened and sandwich panels covering limit states such as fatigue, non-linear buckling and fracture.

scholarly journals Prediction of actual limit stresses in a thin-walled pipe loaded with internal pressure and axial tension

2021 ◽  
pp. 35-41
Author(s):  
Halyna Kozbur ◽  
Oleh Shkodzinsky ◽  
Oleh Yasniy ◽  
Ihor Kozbur ◽  
Roman Hrom'yak
Keyword(s):  
Internal Pressure ◽  
Limit State ◽  
Physical And Mechanical Properties ◽  
Correct Prediction ◽  
Plastic Deformation Zone ◽  
Limit Values ◽  
Axial Tension ◽  
Thin Walled Pipe ◽  
True Stresses ◽  
Thin Walled

If a thin-walled pipe loaded with internal pressure and tension allows the appearance of plastic trains, then the uniform plastic stability loss with the emergence of a local plastic deformation zone is considered the limit state, the corresponding stresses are considered as the limit. Correct prediction of the stress-strain state at the moment of strain localization requires taking into account the actual size of the loaded pipe and the calculation of true stresses. The article proposes the implementation of the method of predicting the limit values of true stresses that appear in the pipe at different ratios of internal pressure and axial tension. The physical and mechanical properties of the material, the type of stress state and the change in the actual dimensions of the loaded element are taken into account.

scholarly journals Design With SADSF Method and Analyses of Elastic Properties of Torsion-Loaded Double-Tee Section With Torsional Box

2019 ◽  
Vol 24 (1) ◽  
pp. 79-89
Author(s):  
I. Markiewicz
Keyword(s):  
Elastic Properties ◽  
Limit State ◽  
Equivalent Stress ◽  
Stress Fields ◽  
Strength Design ◽  
Torsion Moment ◽  
Load Carrying ◽  
Thin Walled ◽  
Better Than

Abstract The work presents the results of preliminary strength design of a thin-walled structure based on double-tee section loaded with a torsion moment. One of the solutions to this problem is considered, in which the torsional box is introduced in the central part. Then, one constructs a series of solution variants that differ in the torsional box length. In the design one uses the method of statically admissible discontinuous stress fields (SADSF) assuming the condition of equalized equivalent stress in the limit state. The work is complemented with elastic FEM analyses of one of the solution variants. Using this example, one shows good load-carrying properties of structures designed with the SADSF method, and proves that they could be several times better than the properties of structures designed with traditional or intuitive ways.

scholarly journals Reliability analysis of offshore wind turbine foundations under lateral cyclic loading

2020 ◽  
Vol 5 (4) ◽  
pp. 1521-1535
Author(s):  
Gianluca Zorzi ◽  
Amol Mankar ◽  
Joey Velarde ◽  
John D. Sørensen ◽  
Patrick Arnold ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Wind Turbine ◽  
Limit State ◽  
Large Diameter ◽  
Probabilistic Approach ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Foundation Design

Abstract. The design of foundations for offshore wind turbines (OWTs) requires the assessment of long-term performance of the soil–structure interaction (SSI), which is subjected to many cyclic loadings. In terms of serviceability limit state (SLS), it has to be ensured that the load on the foundation does not exceed the operational tolerance prescribed by the wind turbine manufacturer throughout its lifetime. This work aims at developing a probabilistic approach along with a reliability framework with emphasis on verifying the SLS criterion in terms of maximum allowable rotation during an extreme cyclic loading event. This reliability framework allows the quantification of uncertainties in soil properties and the constitutive soil model for cyclic loadings and extreme environmental conditions and verifies that the foundation design meets a specific target reliability level. A 3D finite-element (FE) model is used to predict the long-term response of the SSI, accounting for the accumulation of permanent cyclic strain experienced by the soil. The proposed framework was employed for the design of a large-diameter monopile supporting a 10 MW offshore wind turbine.

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