Limit States Design for Onshore Pipelines: Designing for Hydrostatic Test Pressure and Restrained Thermal Expansion

2014 ◽  
Author(s):  
Riski H. Adianto ◽  
Maher A. Nessim
Keyword(s):  
Thermal Expansion ◽  
Input Parameter ◽  
Local Buckling ◽  
Companion Paper ◽  
Design Rule ◽  
Material Strength ◽  
Safety Factors ◽  
Limit States ◽  
Design Rules ◽  
Test Pressure

Reliability-based design rules have been developed for the key serviceability limit states applicable to onshore pipeline including local buckling due to thermal expansion and excessive plastic deformation under hydrostatic test pressure. The design rules are characterized by three elements: the formulas used to calculate the characteristic demand and capacity; the criteria used to define the characteristic values of the key input parameters to these formulas (such as diameter and material strength); and the safety factors defining the required excess capacity over the demand. The overall methodology used in developing the design rules and the practical implications of applying them are described in a companion paper. This paper describes the process used to calibrate safety factors and characteristic input parameter values that meet the desired reliability levels. The results show that local buckling under restrained thermal expansion is only potentially relevant for a small sub-set of cases and based on this, an explicit design rule was not developed. For excessive deformation under hydrostatic test pressure, two alternate design rules are provided; one stress based and the other strain based. The final design rules are described and an assessment of their accuracy and consistency in meeting the reliability targets is included. Guidance is also provided on the conditions in which each check is used.

Limit States Design for Onshore Pipelines: Design Rules for Operating Pressure and Equipment Impact Loads

2014 ◽  
Author(s):  
Maher A. Nessim ◽  
Riski H. Adianto
Keyword(s):  
Impact Load ◽  
Input Parameter ◽  
Companion Paper ◽  
Material Strength ◽  
Operating Pressure ◽  
Safety Factors ◽  
Limit States ◽  
Design Rules ◽  
Reliability Based Design ◽  
Final Design

Reliability-based design rules have been developed for the key ultimate limit states applicable to onshore pipeline, including burst under operating pressure and failure due to equipment impact. The design rules are characterized by three elements; the formulas used to calculate the characteristic demand and capacity; the criteria used to define the characteristic values of the key input parameters to these formulas (such as diameter, material strength, pressure and impact load); and the safety factors defining the required excess capacity over the demand. The overall methodology used in developing the design rules and the practical implications of applying them are described in a companion paper. This paper describes the process used to calibrate safety factors and characteristic input parameter values that meet the desired reliability levels. The final design rules are described in the paper and an assessment of their accuracy and consistency in meeting the reliability targets is included.

Development of Strain Demand and Capacity Distributions to Use in Limit States Design for Geotechnical Loads

2018 ◽  
Author(s):  
Smitha D. Koduru ◽  
Maher A. Nessim
Keyword(s):  
Design Rule ◽  
Limit States ◽  
Design Rules ◽  
Soil Movement ◽  
Demand Distribution ◽  
Reliability Based Design ◽  
Distribution Parameters ◽  
Applicable Range ◽  
General Guidance ◽  
Demand And Capacity

A limit states design approach for onshore pipelines has been developed as part of a multi-year joint industry project (JIP). As part of this project, reliability-based design rules were developed for geotechnical loads, including landslides, slope creep, seismic loads, frost heave and thaw settlement. In consideration of the modelling complexity of the soil movement mechanisms and pipe-soil interaction, and to allow for flexibility to incorporate future model developments, the design rule formulation is directly based on the distribution parameters of the strain demand and capacity of the pipeline. This paper describes the approach used to develop the strain demand and capacity distributions that are required to apply the design rules, as well as the applicable range of distribution parameters. Slope creep was selected as a basis for demonstrating the proposed process, as this loading mechanism occurs more frequently and the data to characterize the necessary uncertainties is available. General guidance related to the development of the strain demand distribution parameters for other geotechnical loads is also provided.

Determination of Safety Factors for Repair of Buried Nuclear Safety Related Metallic Pipe Using Carbon Fiber Reinforced Polymer

2018 ◽  
Author(s):  
Michael P. H. Marohl ◽  
Rasko Ojdrovic
Keyword(s):  
Carbon Fiber ◽  
Nuclear Safety ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Material Strength ◽  
Fiber Reinforced ◽  
Safety Factors ◽  
Design Rules ◽  
Reinforced Polymer ◽  
Corrosion Mechanisms

Buried piping is subject to unique environmental exposure, loading, and restricted access once put into service. Buried piping is susceptible to various corrosion mechanisms on the outside of the pipe as well as internal corrosion mechanisms similar to other aboveground piping. Inspection, repair and replacement of buried piping to address such issues are inherently difficult and costly due to the access issues. To address such difficulties and avoid excavation, a carbon fiber reinforced polymer (CFRP) repair can be applied to the internal diameter of a buried pipe to provide a structural pressure boundary to strengthen or replace the existing piping over a specified length. Pipe repairs using CFRP have traditionally been designed using a Load and Resistance Factor Design (LRFD) approach for determining the demand and the strength of the repair. However, inclusion of CFRP design rules into allowable stress design (ASD) based Section XI of the ASME Boiler and Pressure Vessel Code, which has not adopted LRFD, requires use of safety factors applied to the strength for the appropriate design rules. Both ASD and LRFD have the same philosophy that the stress from the applied loads must be less than the material strength by a certain factor, and the basic difference between the two approaches is how to determine the appropriate factor of safety to cover all unknown variations in load, material strength, installation, and other. This paper provides a basis for development of safety factors for design of CFRP repairs of nuclear safety related buried metallic piping to meet the required maximum acceptable probability of failure and reliability in accordance with NEI 96-07.

Thermal Expansion by Lateral Buckling: Structural Reliability Analysis for the Penguins Flowline

2004 ◽  
Author(s):  
Ralf Peek ◽  
Ian Matheson ◽  
Malcolm Carr ◽  
Paul Saunders ◽  
Nigel George
Keyword(s):  
Thermal Expansion ◽  
Reliability Analysis ◽  
Structural Reliability ◽  
Pipe Wall ◽  
Local Buckling ◽  
Companion Paper ◽  
Bending Moments ◽  
Global Response ◽  
Structural Reliability Analysis ◽  
Full Scale Tests

The Penguins pipeline is a 60 km PIP system designed to buckle laterally on the seabed. This is an effective way to accommodate thermal expansion. However excessive bending could lead to local buckling or wrinkling of the pipe wall. Existing design criteria based on load-controlled or displacement-controlled conditions are not directly applicable here, because the actual conditions fall somewhere in between. For this reason a structural reliability analysis has been performed for the Penguins flowline, to demonstrate that it is safe to allow the flowline to buckle laterally. Thereby the uncertainties that can affect the peak bending moments and curvatures at the buckles are addressed explicitly i.e. one does not rely on an assumption of load- or displacement control. This paper describes how describes how the various uncertainties are combined to assess the structural reliability. Details of the various inputs, including full-scale tests and finite element analyses addressing both global response and local buckling or wrinkling to develop the capacity and response functions are reported in a companion paper.

Influence of Human Error on Structural Reliability

2017 ◽  
Author(s):  
Eric Brehm ◽  
Robert Hertle ◽  
Markus Wetzel
Keyword(s):  
Human Error ◽  
Structural Reliability ◽  
Failure Modes ◽  
Structural Model ◽  
Limit State ◽  
Design Procedure ◽  
Material Strength ◽  
Limit States ◽  
The Impact

In common structural design, random variables, such as material strength or loads, are represented by fixed numbers defined in design codes. This is also referred to as deterministic design. Addressing the random character of these variables directly, the probabilistic design procedure allows the determination of the probability of exceeding a defined limit state. This probability is referred to as failure probability. From there, the structural reliability, representing the survival probability, can be determined. Structural reliability thus is a property of a structure or structural member, depending on the relevant limit states, failure modes and basic variables. This is the basis for the determination of partial safety factors which are, for sake of a simpler design, applied within deterministic design procedures. In addition to the basic variables in terms of material and loads, further basic variables representing the structural model have to be considered. These depend strongly on the experience of the design engineer and the level of detailing of the model. However, in the clear majority of cases [1] failure does not occur due to unexpectedly high or low values of loads or material strength. The most common reasons for failure are human errors in design and execution. This paper will provide practical examples of original designs affected by human error and will assess the impact on structural reliability.

A Review of the Accuracy of Force- and Deformation-Based Methods in Determining the Seismic Capacity of Rehabilitated RC School Buildings

2019 ◽  
pp. 1090-1113
Author(s):  
Orkun Gorgulu ◽  
Beyza Taskin
Keyword(s):  
Nonlinear Deformation ◽  
Structural Characteristics ◽  
Nonlinear Dynamic Analysis ◽  
Earthquake Hazard ◽  
Material Strength ◽  
School Buildings ◽  
Seismic Capacity ◽  
Limit States ◽  
Infill Wall ◽  
Hazard Level

This chapter focuses on the comparison of the conventional linear force-based method with the advanced nonlinear deformation-based method that are commonly preferred to investigate the seismic performances of the existing RC school buildings. School buildings which have different structural characteristics and RC infill wall index are generated from an existing school's layout plan. During the nonlinear dynamic analysis, seven recorded earthquake motions which are scaled in accordance with the Turkish Earthquake Code are employed. Seismic performances of the school buildings against the two different earthquake hazard level are evaluated considering not only various RC infill wall indexes but also different material strengths and number of stories in terms of limit states specified in the code. In order to determine the most appropriate method related to material strength, floor level and RC infill wall index for the seismic strengthening of the existing RC school buildings, the obtained linear forced and nonlinear deformation based analyses results are compared to each other.

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.

Partial Safety Factors and Characteristic Values for Combined Extreme Wind and Wave Load Effects

2005 ◽  
Vol 127 (2) ◽  
pp. 242-252 ◽  
Author(s):  
Niels Jacob Tarp-Johansen
Keyword(s):  
Probabilistic Approach ◽  
Offshore Wind ◽  
Design Rule ◽  
Storm Event ◽  
Wave Loads ◽  
Wave Load ◽  
Safety Factors ◽  
Characteristic Values ◽  
Rule Method ◽  
Definition Of

Background: The present paper regards the concerted action of wind and wave loads on offshore wind turbines in the extreme storm event. The load combination problem involves the definition of the characteristic loads and safety factors. In wind engineering and offshore engineering well established practices for the definition of characteristic values and safety factors for wind and wave loads separately exist. The aim is to investigate the possibility of making a simple merger of these existing practices into a possibly conservative design rule. Method of Approach: The paper applies a simplified probabilistic approach giving an understanding of how the merging can possibly be established and finally gives first guidance on the choice of characteristic values and safety factors. Results and conclusions: Under the assumptions made herein, it is made probable that a simple combination rule can be established.

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