Comparative Review of the Established UHB Assessment Methods for Offshore Pipelines

2015 ◽  
Author(s):  
Sajith Kumar ◽  
Daniel Smith ◽  
Hooman Jafari
Keyword(s):  
Survey Data ◽  
Structural Reliability ◽  
Load Resistance ◽  
Design Parameters ◽  
Operational Parameters ◽  
Resistance Factors ◽  
Upheaval Buckling ◽  
Variation Of Parameters ◽  
Comparative Review ◽  
Load And Resistance Factors

Out of straightness upheaval buckling (OOS UHB) assessment considers the pipeline design and operational parameters, post-lay survey data and the properties of back-fill and rock in order to determine load and resistance factors that are applied. The factors allow for the natural variation of all parameters and are ultimately used to determine the download requirements along the route of a pipeline that is susceptible to UHB. Two methods are most commonly used in OOS UHB assessments. The structural reliability analysis (SRA) method is the most established and explicitly considers the variation of parameters in a Monte-Carlo simulation, enabling load and resistance factors to be calculated with a defined reliability level. A more recently developed methodology is documented in DNV-RP-F110 and provides a unified approach to the calculation of safety factors. The approach was calibrated using structural reliability based methods, undertaken with target reliability levels that are compliant with DNV-OS-F101. This paper presents a review of two key components of OOS UHB assessments. These components are the accuracy of post-lay survey data and the load resistance factor calculation method. These components are reviewed in the context of SRA and DNV-RP-F110 based assessments for a range of pipeline sizes, and ranges of soil and operational parameters. This enables characterisation of the differences between the two methodologies for ranges of design parameters that represent the majority of in-field flowlines that are installed in the United kingdom Continental Shelf (UKCS). SRA and DNV-RP-F110 derived load and resistance factors are compared and the effect of survey data smoothing upon rock-dump requirements is also discussed.

Subsea Pipeline UHB OOS Design: Structural Reliability Analysis

2017 ◽  
Author(s):  
M. Liu ◽  
C. Cross
Keyword(s):  
Reliability Analysis ◽  
Survey Data ◽  
Structural Reliability ◽  
Design Parameters ◽  
Load Factor ◽  
Data Sets ◽  
Subsea Pipeline ◽  
Upheaval Buckling ◽  
Structural Reliability Analysis ◽  
Load Factors

Upheaval buckling (UHB) is a major design concern for a trenched and buried subsea pipeline operating at high temperature and pressure. A predictive assessment is necessary during the detailed engineering design and optimisation to evaluate and define any measure that may be utilised for UHB mitigation such as deep trenching, backfilling, blanket or spot rockdumping. A pre-emptive UHB structural reliability analysis (SRA) has to be performed prior to pipeline installation based on the typical trench imperfection out of straightness (OOS) statistics. The SRA results are updated once survey data is made available. A rockdump schedule can be established by incorporating appropriate safety or load factors to address uncertainties in the design parameters and as-built OOS survey measurement accuracy. This paper examines the basis for processing the OOS features from survey data and stochastic distributions assumed for SRA with a view to improving the SRA OOS analysis. A number of OOS issues are considered. To cut conservatism an alternative distribution and interpretation is proposed for the key SRA input parameters with regards to imperfections and survey resolution. The random imperfection height assumption used in the current SRA practice for UHB is thus challenged — the rationale and argument for an alternative approach are constructed through a review of stochastic process theory, additional integrity criteria, a parametric analysis and evaluation of multiple OOS survey data sets. To add to the strength of the argument, a range of engineering issues are discussed in the context of stochastic distributions of imperfections. A worked example and case study is presented leading to a rationally reduced load factor and rockdump volume requirement for OOS UHB mitigation and protection.

scholarly journals Reliability Estimation for Highway Bridges

2020 ◽  
Author(s):  
Nafiseh Kiani
Keyword(s):  
Reliability Index ◽  
Structural Reliability ◽  
Limit State ◽  
Highway Bridges ◽  
Reliability Estimation ◽  
State Function ◽  
Limit States ◽  
Resistance Factors ◽  
Load And Resistance Factors ◽  
Reliability Methods

Structural reliability analysis is necessary to predict the uncertainties which may endanger the safety of structures during their lifetime. Structural uncertainties are associated with design, construction and operation stages. In design of structures, different limit states or failure functions are suggested to be considered by design specifications. Load and resistance factors are two essential parameters which have significant impact on evaluating the uncertainties. These load and resistance factors are commonly determined using structural reliability methods. The purpose of this study is to determine the reliability index for a typical highway bridge by considering the maximum moment generated by vehicle live loads on the bridge as a random variable. The limit state function was formulated and reliability index was determined using the First Order Reliability Methods (FORM) method.

HotPipe JIP: HP/HT Buried Pipelines

2005 ◽  
Author(s):  
Stig Goplen ◽  
Pa˚l Stro̸m ◽  
Erik Levold ◽  
Kim J. Mo̸rk
Keyword(s):  
Survey Data ◽  
Structural Reliability ◽  
Soil Cover ◽  
Cohesive Soil ◽  
Design Criteria ◽  
Functional Requirements ◽  
Upheaval Buckling ◽  
Reliability Methods ◽  
Partial Safety Factors ◽  
Pipeline Design

The HotPipe Project is a Joint Industry Project, whose overall objective is to prepare a DNV Recommended Practice to be used in structural design of high temperature/high pressure pipelines. The developed design criteria are based on the application of structural reliability methods to calibrate the partial safety factors involved. One of the three scenarios covered in this DNV-RP is buried pipes subjected to upheaval buckling which is discussed in this paper. The most significant factor in this scenario is uncertainty in the pipeline configuration and uncertainty in the pipe-soil interaction. The paper presents the background of the proposed soil capacities and the associated uncertainties for both uplift resistance and downward resistance in cohesive and non-cohesive soil. The paper links these soil models with the design requirements to upheaval buckling including: - Functional requirements i.e. survey data accuracy, smoothing of survey data, modeling of the pipeline, design conditions, soil cover etc.; - Trenching technology; - Qualification of the minimum soil cover, natural or artificial, with the aim to guarantee pipeline stability; - Assessment of pipeline response; - Pipe integrity checks and design criteria. The internal confidential project guideline has been completed and is currently in the process of being converted into an official DNV-RP-F110, to be published later this year.

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.

Development of Photocatalytic Pervious Concrete Pavement for Air and Storm Water Improvements

2012 ◽  
Vol 2290 (1) ◽  
pp. 161-167 ◽  
Author(s):  
Somayeh Asadi ◽  
Marwa M. Hassan ◽  
John T. Kevern ◽  
Tyson D. Rupnow
Keyword(s):  
Flow Rate ◽  
Mechanical Performance ◽  
Concrete Pavement ◽  
Pervious Concrete ◽  
Mix Design ◽  
Unit Weight ◽  
Experimental Program ◽  
Design Parameters ◽  
Operational Parameters ◽  
Cleaning Agents

Self-cleaning, air-purifying pervious concrete pavement is a promising technology that can be constructed with air-cleaning agents with superhydrophilic photocatalyst capabilities, such as titanium dioxide. Although this technology has the potential of supporting environment-friendly road infrastructure, its effectiveness depends on a number of design and operational parameters that need to be evaluated. The objective of this study was to evaluate the mechanical, environmental, and mix design parameters that influence the performance and effectiveness of photocatalytic pervious concrete pavement. To achieve this objective, an experimental program was conducted in which the effects of relative humidity level, pollutants' flow rate, and mix design parameters, including void ratio and depth of the photocatalytic layer, were investigated. Mechanical performance tests included porosity, unit weight, permeability, and compressive strength. The environmental efficiency of the samples to remove nitrogen oxides (NOx) from the atmosphere was measured in the laboratory. Results of the experimental program showed that increasing the depth of the photocatalytic layer increased NOx reduction efficiency. In addition, NOx removal efficiency decreased with the increase in the pollutant flow rate and increased with the increase in ultraviolet light intensity.

A LRFD Code Format for Accounting Long-Term Variation of Multiple Load Effects

2002 ◽  
Author(s):  
Paulo Mauricio Videiro ◽  
Luis Volnei Sudati Sagrilo ◽  
Edison Castro Prates de Lima
Keyword(s):  
Extreme Value ◽  
Structural Components ◽  
Short Term ◽  
Resistance Factors ◽  
Term Variation ◽  
Load And Resistance Factors ◽  
Load Effects ◽  
Code Format ◽  
Multiple Load

This paper proposes a Load and Resistance Factors Design (LRFD) code format for structural components of offshore structures under multiple load effects. This code format accounts for the long-term variation of seastate and the actual correlation between dynamic load effects due to environmental actions. Ultimate limit states are formulated in terms of an Interaction Ratio (IR) random variable, such that the long-term extreme value of IR greater than unity means component failure. The long-term distribution of IR is obtained by combining the distribution of each short-term seastate. The short-term response of the generally nonlinear IR is determined by time domain simulation, taking into account partial load and resistance factors. The IR short-term distribution may be fitted, for instance, by using Rayleigh or Weibull distribution. The main advantages of the proposed code format are: • This code format accounts implicitly and correctly for the actual correlation among all dynamic environmental load processes. • Structural designers have used interaction ratios for a long time. Hence, it is straightforward to evolve from a deterministic stage of looking for IR < 1, as in old Working Stress Design codes, to a code format where the aim is to design structural components with long term IR extreme value < 1. The feasibility of the proposed code format is demonstrated by calibrating partial factors for beam-column cylindrical members based on components of a Floating Production System Semi-submersible hull.

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