Reliability-based Methodology Research Articles

Time-Dependent Reliability-Based Methodology for Assessing Fracture Toughness Requirements for Highway Bridges

Time-Dependent Reliability-Based Methodology for Assessing Fracture Toughness Requirements for Highway Bridges

Optimized planning for weather-sensitive offshore construction operations - An application to float-over installation of super-heavy offshore topsides

Float-over method offers an efficient, reliable, and practical installation scenario for large-scale offshore topsides. It is, however, highly sensitive to marine environmental conditions and necessitates comprehensive pre-planning. Conventional deterministic approaches methodologies exhibit shortcomings in achieving a cost-effective and time-efficient float-over design, thereby necessitating a comprehensive reconsideration. This study aims to develop a reliability-based methodology for float-over analysis of super-heavy offshore topsides. Incorporating diverse geometric and mechanical limit state functions, the permissible weather window is determined by use of Monte-Carlo Simulation. This methodology leverages the data set generated based on nonlinear coupled multi-body hydrodynamic simulation of the float-over operations. The presented idea provides a decision-making platform that integrates safety and efficiency considerations. The float-over design is optimized utilizing the developed approach and some recommendations are made to enhance applicable codes and guidelines. To reduce the computational expenses, the application of the importance sampling technique is subsequently proposed. Long-term planning of float-over installation is derived finally, optimizing operational time and cost while keeping risks as low as reasonably practical. In conclusion, it is crucial to establish a reliability-based framework for scheduling weather-sensitive offshore construction projects.

A reliability-based methodology for resilient spare parts planning and control

Geo-political conflicts, financial crises, natural disasters, pandemics, human operational errors, and other disruptive events can affect supply chain integrity with unpredictable consequences. In addition, intermittent demand patterns and strict service requirements enhance the complexity of Spare Parts Supply Chains (SPSCs). SPSC resilience has become a significant challenge in today’s increasingly competitive business environment.This study presents a reliability-based methodology with a customer-oriented perspective to support industrial companies in spare parts planning and control. This original approach provides resilience to SPSCs by defining a statistical variable to study supply chain variabilities and externalities, aiding stockout risk control, and suggesting spare parts management plans. The application of the proposed methodology in a case study of a packaging machine company is illustrated.

Optimal weather window for transportation of large-scale offshore structures

Offshore transportation is recognized as one of the most dominant sources of human and financial loss, among all varieties of maritime and offshore operations. The conventional deterministic approach to address the corresponding risks, therefore, needs to be reconsidered. This study aims at developing a reliability-based methodology for marine transportation analysis of large-scale offshore modules. Taking vessel stability and strength as the limiting criteria, the allowable weather window is extracted by use of Monte Carlo simulation. Comparing the results of conventional deterministic and reliability-based approaches, the efficiency of the proposed methodology is well demonstrated. The importance sampling technique is also proposed subsequently to reduce the computational time and effort. The developed framework is ultimately employed for optimal planning of offshore transportation, aiming to minimize weather-related downtime. The application of the proposed probabilistic approach for planning the installation phase of offshore projects leads to a significant reduction in costs while keeping the risk level as low as reasonably practicable.

Failure assessment of reinforced rock slopes subjected to bolt corrosion considering correlated multiple failure modes

This paper presents a reliability-based methodology for failure assessment of reinforced rock slopes subjected to bolt corrosion. Strength failure of the rock bolt, bond failure between the rock bolt and the grout and bond failure between the rock and the grout are considered and their load effects are treated as stochastic processes. The failure probability of each failure mode was evaluated using first passage probability, in which two auto-correlation functions are considered for the load effect processes. The correlations among failure modes are also considered for system reliability analysis. The application of the proposed methodology is demonstrated by a worked example. Sensitivity analysis is also undertaken to identify most influential parameters on slope failure probability. It is found that the type of auto-correlation functions and the correlation length of the load effect processes significantly affect the failure probability of each individual failure while the correlations among the failure modes considerably influence the system failure probability. It is also found that cohesion and friction angle are most influential on the failure probability for all failure modes while the corrosion model and the initial bond strengths are only influential for the bond failure between the rock bolt and the grout and both bond failures respectively.

Reliability evaluation method for pipes buried in fault areas based on the probabilistic fault displacement hazard analysis

The tectonic fault poses a great threat to buried pipe segments. Buckling or rupture of pipes will ensue due to large strain induced by continuously increasing fault movements. In this study, a reliability-based methodology is conceptually proposed for designing new buried pipes or assessing existing pipes installed in fault areas. Uncertainties associated with the influencing factors of pipe structure and seismic loading (fault displacement) generated by earthquakes are considered. For pipe structural reliability, a developed back-propagation neural network (BPNN)-based surrogate model is utilized for the strain demand term in the limit state function for reliability calculations. Given statistical data for the basic variables including diameter, wall thickness, internal pressure, intersection angle or dip angle, and soil spring resistances, the conditional probability of failure can be obtained at a particular fault displacement by Monte Carlo simulation. Uncertainty of the fault displacement is estimated based on probabilistic fault displacement hazard analysis (PFDHA) having results given as probability of exceeding a certain fault displacement level for a specific site, then the occurrence probability of a specific fault displacement at a specific time can be indirectly obtained. The actual probability of failure (PoF) is calculated as an integral of fault displacement based on the total probability which is the product of the conditional PoF of pipe structure and occurrence probability of the specific fault displacement. This developed methodology is applied to a case study about a pipe project from China. Results show that the probability of failure increases with the elapsed time but stay within the safety margin for the next 30 years. Generally, the result of PFDHA is an essential input parameter in reliability analysis for pipes buried in fault regions. The multidisciplinary combination of structural reliability analysis and fault displacement hazard analysis is of practical significance for the reliability-based study of pipes in fault regions.

Reliability-based assessment of percentage combination rules considering the collapse performance of special concentrically braced frames

In the seismic design of structures, the combinatorial effects of multiple horizontal ground motion components are often determined using the 100/p% percentage rule (i.e. designs based on 100% in one direction and p% in the other). In this study, a reliability-based methodology is developed to explicitly link building collapse caused by percentage-rule-based-underestimation of the design force demands to the adopted p% value. The methodology is applied to three special concentrically braced frame (SCBF) buildings (4, 8, and 12 stories) with corner columns shared by orthogonal frames. Each building case is designed using the 100/30%, 100/65%, and 100/100% percentage rule. Response history analyses using bidirectional and unidirectional loading are performed on nonlinear structural models to obtain the “true” demands and percentage-rule-based demands, respectively. Models constructed with and without considering SCBF column failure are utilized within the overall reliability-based framework to isolate the effect of underestimated design force demands on collapse performance. A quantitative relationship between the adopted p% value and building structural collapse risk is established. The results show that there is a nonlinear relationship between an increase in p% and the benefits in terms of reduced collapse risk. Also, taller buildings are shown to benefit more from conservative (higher) p% values compared to shorter ones.

Investigating an assessment model of system oil leakage considering failure dependence.

Corrosion has made petrochemical infrastructure becomes a significant hazard of the surrounding environment. It is an excellent approach to reduce the risk of environmental pollution by improving the accuracy of determining the leakage probability of the equipment system. In this work, a reliability-based methodology was proposed to assess the system leakage probability with multiple pipe segments under the common cause failure (CCF). Specifically, the existence of FD between the pipe segments was examined under the CCF so that a system leakage assessment model was developed considering the FD. Thereby a novelty corrosion-induced leakage risk management framework was developed. After leakage evaluation for an oil pipeline, it was found that the results obtained were too conservative if ignoring FD, which will develop a wasteful maintenance plan. Overall, the findings in this work may be an opportunity for managers to improve maintenance efficiency.

Impact of environmental variables on the degradation of photovoltaic components and perspectives for the reliability assessment methodology

Backsheet cracking has been a major issue observed in the field; however, standardized qualification tests, such as IEC61215, are inadequate to reliably identify such failures of PV modules due to the lack of the critical weathering factors applied sequentially or in combination, such as those found in the service environments. To address this problem, we investigated the effects of various environmental variables on the degradation and failure behaviors of the polyamide-based backsheet in PV modules retrieved from five different locations, encompassing a variety of climates, including humid subtropical, hot-summer Mediterranean, tropical savanna climate and hot arid. The correlations between the degradation indicators and the weathering variables were further demonstrated by principle components analysis (PCA). We found strong relationships between: carbonyl formation and reflected solar radiation; hydroxyl formation and module temperature; yellowness and NO2 concentration, while no simple correlation could be found between a specific weathering factor and cracking. By introducing additional stress factors to the aged polyamide-based backsheet films with the novel “fragmentation test”, we successfully reproduced the field cracking behaviour. This study has demonstrated that different degradation modes of PV components respond differently to the environmental stresses encountered in service. Thereby, any accelerated laboratory test based on a single set condition or lacking key environmental variables would be inadequate to assess the long-term performance of PV modules and components. A new reliability-based methodology is proposed to quantitatively link laboratory testing with field results for the service life prediction of PV materials.

Transit system resilience: Quantifying the impacts of disruptions on diverse populations

The resilience of a community to disruptions in a public transportation system depends not only on the technical system's ability to maintain service levels, but also on the ability of individuals to cope with and adapt to disruptions. This paper proposes a reliability-based methodology for conceptualizing and evaluating resilience of a socio-technical system in the context of diverse populations of passengers who experience the system differently, but share its resources. Considering a transit network as a socio-technical system induces coupling with other technical systems, such as communication networks and other transportation modes, which support user adaptability in disruption. Extending concepts from fault trees and binary decision diagrams (BDDs), a multi-valued dependency graph framework is developed and used to quantify the resilience of the system. Various notions of resilience are explored. Techniques for identifying which mechanisms, whether technically or socially driven, are critical to the resilience of each population are discussed. Sensitivity to various factors through the study of improvement potential provides practical insight into policies and technical improvements that can increase system or user resilience.

Prediction of Fracture Failure of Steel Pipes With Sharp Corrosion Pits Using Time-Dependent Reliability Method With Lognormal Process

This paper presents a reliability-based methodology for assessing fracture failures of steel pipes with sharp corrosion pits. Based on newly developed models of elastic fracture toughness, the simple criterion of stress intensity factor (SIF) is used to establish the limit state functions for pipes with sharp corrosion pits in the longitudinal and circumferential directions. A stochastic model of load effect is developed and a time-dependent reliability method based on first passage probability for nonstationary lognormal processes is employed to quantify the probability of failure and predict the remaining service life. After applying the methodology to a case study, sensitivity analysis is carried out to identify the most influential variables on the probability of failure. It is found in the paper that the correlation coefficient has a considerable effect on probability of failure of steel pipes with sharp corrosion pits and that the larger the mode I fracture toughness is, the smaller the probability of pipe failure is.

PICA: PIPELINE INTEGRATED CORROSION ASSESSMENT TOOL FOR STRUCTURE INTEGRITY

The paper develops an automated assessment tool specially tailored for corroding steel pipeline used to convey hydrocarbon deposit. The proposed tool named PICA integrates deterministic and reliability method to evaluate the time-variant remaining allowable pressure of steel pipelines subjects to internal and external corrosion based on series of metal loss data. The deterministic assessment method is preferred by pipeline operator due to its simplicity, yet the accuracy is still arguable as the integrity of assessment results is dominantly governed by inherent uncertainties which insufficiently covered even by the introduction of safety factor. Whereas reliability assessment requires systematic data sampling and matching method as well as probabilistic nature of the parameters to give more credible and accurate result especially in estimating the corrosion growth rate. The combination of data sampling, data analysis, structure assessment and integrity prediction both in the form of deterministic and reliability-based methodology has great potential to be developed as robust and potent software. This assessment software covers wide range of options including selection of assessment codes, corrosion models, data sampling techniques, assessment methods and particularly effective to manage the vast amounts of collected data relating to pipeline condition, in a way that enables pipeline operators to monitor the pipeline integrity efficiently. By integrating various stages of pipeline assessment procedure into a unified systematic assessment framework, it can greatly assist pipeline operator to protect the public, financial investment and environment from such devastating effects owing to pipeline failures.

Alternative reliability-based methodology for evaluation of structures excited by earthquakes

In this paper, an alternative reliability-based methodology is developed and implemented on the safety evaluation of structures subjected to seismic loading. To effectively elaborate the approach, structures are represented by finite elements and seismic loading is applied in time domain. The accuracy of the proposed reliability-based methodology is verified using Monte Carlo Simulation. It is confirmed that the presented approach provides adequate accuracy in calculating structural reliability. The efficiency and robustness in problems related to performance-based seismic design are verified. A structure designed by experts satisfying all post-Northridge seismic design requirements is studied. Rigidities related to beam-to-column connections are incorporated. The structure is excited by three suites of ground motions representing three performance levels: immediate occupancy, life safety, and collapse prevention. Using this methodology, it is demonstrated that only hundreds of deterministic finite element analyses are required for extracting reliability information. Several advantages are documented with respect to Monte Carlo Simulation. To showcase an applicability extension of the proposed reliability-based methodology, structural risk is calculated using simulated ground motions generated via the broadband platform developed by the Southern California Earthquake Center. It is validated the accuracy of the broadband platform in terms of structural reliability. Based on the results documented in this paper, a very solid, sound, and precise reliability-based methodology is proved to be acceptable for safety evaluation of structures excited by seismic loading.

Reliability-based assessment of damaged concrete buildings

Damages in concrete structures due to aging and other factors could be a serious and immense matter. Making the best selection of the most viable and practical repairing and strengthening techniques are relatively difficult tasks using traditional methods of structural analyses. This is due to the fact that the traditional methods used for assessing aging structure are not fully capable when considering the randomness in strength, loads and cost. This paper presents a reliability-based methodology for assessing reinforced concrete members. The methodology of this study is based on probabilistic analysis, using statistics of the random variables in the performance function equations. Principles of reliability updating are used in the assessment process, as new information is taken into account and combined with prior probabilistic models. The methodology can result in a reliability index B that can be used to assess the structural component by comparing its value with a standard value. In addition, these methods result in partial safety factor values that can be used for the purpose of strengthening the R/C elements of the existing structure. Calculations and computations of the reliability indices and the partial safety factors values are conducted using the First-order Reliability Method and Monte Carlo simulation.

Assessment of damage and residual load bearing capacity of a concrete slab after fire: Applied reliability-based methodology

For most fires occurring in buildings with a concrete structural frame, the structural elements do not collapse during fire exposure, and further use of the building after fire may be possible. Fire can nevertheless result in a permanent loss of strength and thus a post-fire evaluation of the residual load bearing capacity has to be made to inform decisions on continued use and the need for structural repairs. This evaluation is however particularly difficult due to the many uncertainties associated with both the fire exposure and the characteristics of the structural elements. These uncertainties cannot be neglected when determining the residual capacity since adequate safety is a major societal concern as indicated by the predominance of safety in current design standards and guidance documents. In this paper a comprehensive methodology is presented for the assessment of the residual capacity of concrete structures after exposure to fire. The methodology is introduced through application to a real-life case study of an apartment fire with a focus on the end-span of the affected continuous concrete slab. It results in a reliability-based evaluation of the maximum allowable characteristic value for the imposed load on the slab. The presented methodology is useful to make informed decision about continued use of structures after a fire event.

Failure assessment and safe life prediction of corroded oil and gas pipelines

Failure of in service oil and gas pipelines can result in catastrophic consequences. To avoid the economical, environmental and social impacts due to pipeline collapse, rational methodologies should be employed to predict the safe life of corrosion affected steel pipes and to instigate maintenance and repairs for the corroded pipeline system. The uncertainties in corrosion sizes and pipe characteristics actuate the residual strength model to be a probabilistic model rather than a deterministic one. Therefore, an analytical reliability-based methodology using first passage probability theory for failure assessment of corrosion affected oil and gas pipelines is presented in this paper. The methodology is applied for a defected 1.5km oil pipeline and failure probability is estimated versus time. Sensitivity analysis is also undertaken to identify and evaluate the factors that affect the failure due to the strength loss. It can be quantitatively estimated that how decrease in internal pressure can increase the safe life of the pipeline. The methodology can help pipeline engineers and asset managers in prioritizing pipeline repairs and/or replacements based on their estimated probability of failure.

Calibration of the FRP Resistance Reduction Factor for FRP-Confined Reinforced Concrete Building Columns

AbstractThis paper presents a reliability-based methodology for calibration of the fiber-reinforced polymer (FRP) resistance reduction factor used in the design of FRP-confined RC columns designed ...

Reliability-based Strength Amplification Factors for Structures with Asymmetric Yielding

A reliability-based methodology to estimate strength amplification factors for structures with asymmetric yielding is proposed. The approach is based on structural demand hazard analyses. Nonlinear time-history analyses of tridimensional simplified systems are carried out. The effects of two orthogonal components of the seismic ground motions and soil-structure interaction, are considered. Results show that the expected ductility demand of systems with asymmetric yielding may be much higher than those of symmetric systems. A simplified mathematical expression (which is function of the ratio between the fundamental vibration period of the system and that of the soil, ductility demand, and level of asymmetric yielding) is proposed to estimate the amplification factors. The expression is applied successfully to a 9-story reinforced concrete building exhibiting asymmetric yielding produced by tilting.

Serviceability assessment and sensitivity analysis of cast iron water pipes under time-dependent deterioration using stochastic approaches

Research Article| September 28 2016 Serviceability assessment and sensitivity analysis of cast iron water pipes under time-dependent deterioration using stochastic approaches Mojtaba Mahmoodian; Mojtaba Mahmoodian 1School of Engineering, RMIT, Melbourne, Australia E-mail: mojtaba.mahmoodian@rmit.edu.au Search for other works by this author on: This Site PubMed Google Scholar Chun Qing Li Chun Qing Li 1School of Engineering, RMIT, Melbourne, Australia Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2016) 65 (7): 530–540. https://doi.org/10.2166/aqua.2016.101 Article history Received: August 12 2015 Accepted: August 09 2016 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Mojtaba Mahmoodian, Chun Qing Li; Serviceability assessment and sensitivity analysis of cast iron water pipes under time-dependent deterioration using stochastic approaches. Journal of Water Supply: Research and Technology-Aqua 3 November 2016; 65 (7): 530–540. doi: https://doi.org/10.2166/aqua.2016.101 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Determination of the depth of the corrosion pit is essential to predict the serviceability of corrosion affected pipes and to instigate maintenance and repairs for the pipeline system. In this paper, a reliability-based methodology for serviceability assessment of corrosion affected pipes is presented. The depth of corrosion pit is considered as the critical parameter that causes serviceability failure when it is greater than the wall thickness of the pipe. A stochastic model for corrosion depth of cast iron pipes is developed and a time-dependent method is employed to quantify the probability of serviceability failure so that the time for the pipeline to be unserviceable and hence requiring repairs can be determined. A sensitivity analysis is also undertaken to identify the factors that affect the failure due to corrosion. The methodology presented in this study can be used as a tool for infrastructure managers in different industries such as water distribution systems, oil and gas pipelines, sewer networks, etc. The methodology can help pipeline engineers and asset managers in making decisions with regard to the serviceability of corrosion affected pipelines both for assessment of existing systems and for designing new pipelines. cast iron pipes, corrosion pit, first passage probability, life time prediction, reliability analysis, serviceability failure © IWA Publishing 2016 You do not currently have access to this content.

Efficient Approach for the Reliability-Based Design of Linear Damping Devices for Seismic Protection of Buildings

This paper presents an efficient reliability-based methodology for the seismic design of viscous/viscoelastic dissipative devices in independent and/or coupled buildings. The proposed methodology is consistent with modern performance-based earthquake engineering frameworks and explicitly considers the uncertainties affecting the seismic input and the model parameters, as well as the correlation between multiple limit states. The proposed methodology casts the problem of the dampers’ design for a target performance objective in the form of a reliability-based optimization problem with a probabilistic constraint. The general approach proposed in this study is specialized to stochastic seismic excitations and performance levels for which the structural behavior can be assumed as linear elastic. Under these conditions, the optimization problem is solved efficiently by taking advantage of existing analytical techniques for estimating the system reliability. This analytical design solution is an approximation of the optimal design and can be used as a hot-start point for simulation-based techniques, which can be employed to find the optimal design solution. An efficient correction formula is proposed to obtain an improved design solution that is generally sufficiently close for engineering purposes to the optimal design solution obtained from significantly more-computationally-expensive simulation-based techniques. The proposed design methodology is illustrated and validated by considering two steel buildings modeled as linear elastic multiple-degree-of-freedom systems for different linear damper properties and collocation, for both independent and coupled configurations.