Case study: conservation and restoration of a pair of large diameter English globes

2015 ◽  
Vol 38 (1) ◽  
pp. 77-91
Author(s):  
T.K. McClintock ◽  
Lorraine Bigrigg ◽  
Deborah LaCamera
Keyword(s):  
Large Diameter

Thinning in mature eastern white pine: 43-year case study

2002 ◽  
Vol 78 (4) ◽  
pp. 539-549 ◽  
Author(s):  
Paul D Anderson ◽  
John C Zasada ◽  
Glen W Erickson ◽  
Zigmond A Zasada
Keyword(s):  
Genetic Diversity ◽  
Dna Analysis ◽  
Large Diameter ◽  
White Pine ◽  
Thinning Intensity ◽  
Pine Regeneration ◽  
Volume Production ◽  
Pine Stands ◽  
Over Time

A white pine (Pinus strobus L.) stand at the western margin of the species range, approximately 125 years of age at present, was thinned in 1953 from 33.5 m2 ha-1 to target residual basal areas of 18.4, 23.0, 27.5, and 32.1 m2 ha-1 . Repeated measurement over the following 43-years indicated that the greatest total volume production and the greatest number of large diameter trees occurred in the unit of highest residual density. Over time, the distribution of stems was predominantly random although mortality between 1979 and 1996 resulted in a tendency for clumping in the 23.0 and 27.5 m2 ha-1 treatments. DNA analysis indicated that thinning intensity had little effect on the genetic diversity of residual white pine. This study suggests that mature white pine stands in northern Minnesota may be managed at relatively high densities without loss of productivity. However, regardless of overstory density, there was little or no white pine regeneration occurring in this stand. Key words: thinning, growth, genetic diversity, molecular markers, spatial pattern, regeneration

Probabilistic Fatigue Reliability of Large Diameter Steel Catenary Risers (SCR) for Ultra-Deepwater Operations

2007 ◽  
Author(s):  
U. O. Akpan ◽  
T. S. Koko ◽  
P. A. Rushton ◽  
A. Tavassoli ◽  
M. Else
Keyword(s):  
Fatigue Strength ◽  
Case Studies ◽  
Material Properties ◽  
Large Diameter ◽  
Random Variables ◽  
Fatigue Reliability ◽  
Strength Parameters ◽  
Stress Levels ◽  
Steel Catenary Risers

For deepwater development in the Gulf of Mexico, steel catenary risers (SCRs) supported from both SPAR and semi-submersible platforms have proven to be successful solutions for in-field flowlines, tie-backs, and export systems. It is envisaged that this will continue to be a promising solution in ultra deep-water applications, up to and beyond 10,000 ft. The study, commissioned by the Mineral Management Service (MMS), investigated the reliability of large-diameter SCRs in ultra-deepwater operations. The primary damage mode considered is fatigue failure. A probabilistic methodology for fatigue reliability is developed, which utilizes deterministic cumulative fatigue damage indicators, namely the stress levels and cycles associated with the various sea states and the fatigue strength of the members. Uncertainties in structural load and material properties are accounted for by assigning probability distributions and standard deviations to the deterministic stress levels. Furthermore, fatigue strength parameters, Miner’s indices, and capacities are modeled as random variables. First order reliability method (FORM) is employed for estimating fatigue reliability. The methodology is applied to three deterministic case studies presented by Intec Engineering (2006a, 2006b). The case studies involved either a SPAR or a semi-submersible platform. For the sake of brevity, a case study involving only a SPAR platform is presented in this paper. The effect of uncertainties in parameters on fatigue reliabilities is investigated. It is observed that the fatigue reliability estimates followed similar trends as the deterministic cumulative damage results, and hence can be used to complement deterministic estimates. Additional benefit and insight gained from the probabilistic study, which can be used for design decisions, include information regarding probabilistic importance and probabilistic sensitivity analysis. For case study presented here, it is seen that in general, uncertainty in the fatigue strength exponent (m) has the highest impact on fatigue reliability of SCRs. The second most important random variable is the stress range (S), which captures uncertainties in parameters such as loads and material properties. Parametric sensitivity studies on the fatigue strength parameters indicate that SCR reliability is sensitive to both the standard deviation and probability distribution of the parameters, thus highlighting the need for accurate probabilistic calibration of the random variables.

Long Term Structural Integrity Considerations for Abandoned Pipelines

2016 ◽  
Author(s):  
Shane Finneran ◽  
T. J. Prewitt ◽  
Joel Kaufman
Keyword(s):  
Transmission Lines ◽  
Structural Integrity ◽  
Large Diameter ◽  
Metal Loss ◽  
Finite Element Analyses ◽  
Load Bearing Capacity ◽  
Soil Subsidence ◽  
Structural Capacity

There has been increasing interest across the industry to better understand the possible long term risks associated with out of service pipelines. In Canada, the Canadian Energy Pipeline Association (CEPA), Petroleum Technology Alliance of Canada (PTAC), and the National Energy Board (NEB), have undertaken multiple studies to identify and assess the threats related to pipeline abandonment. [1][2][3] The primary hazards typically identified across industry for pipeline abandonment are associated with long term corrosion degradation, potential for creation of water conduits, possible environmental impacts, and potential for pipeline collapse and associated soil subsidence. Unfortunately, little guidance is presently available to the industry for determining remaining structural capacity of a heavily corroded pipeline to establish likelihood, and possible timeline, of collapse, nor for determining possible subsidence magnitudes associated with large diameter transmission lines. This paper presents a technical case study for an assessment approximating the remaining strength of an abandoned pipeline subject to long term corrosion degradation, considering both general metal loss, and randomized pitting and perforation growth. The work presented used a combination of finite element analyses, and existing industry models for determining load bearing capacity of an abandoned pipeline under varying levels of degradation.

Case study on pile running during the driving process of large-diameter pipe piles

2017 ◽  
Vol 36 (6) ◽  
pp. 709-721 ◽  
Author(s):  
Liqiang Sun ◽  
Yandi Wang ◽  
Wei Guo ◽  
Shuwang Yan ◽  
Jian Chu ◽  
...  
Keyword(s):  
Large Diameter ◽  
Large Diameter Pipe ◽  
Diameter Pipe

Rational Stress Limits and Load Factors for Finite Element Analyses in Pipeline Applications: Part III — Elastic-Plastic Load Factor Development

2016 ◽  
Author(s):  
Rhett Dotson ◽  
Chris Alexander ◽  
Ashwin Iyer ◽  
Al Gourlie ◽  
Richard Kania
Keyword(s):  
Finite Element ◽  
Case Studies ◽  
Large Diameter ◽  
Load Factor ◽  
Pipe Material ◽  
Line Pipe ◽  
Elastic Plastic ◽  
First Case ◽  
Load Factors

In this paper, a methodology is presented to develop load factors for use in elastic-plastic assessments of pipelines and their components. The load factors are based on the pipe material properties and the ASME pipeline code’s design margin for the service and location of the pipeline installation [1, 2]. These codes are recognized by 49 CFR 192 and 195 [3, 4]. Minimum required load factors for internal pressure loads can be derived analytically based on design equations from the ASME B31 piping codes and minimum material requirements for API 5L line pipe [6]. Once the load factor is established for a particular case, the elastic-plastic methodology may be used in the Finite Element Analysis (FEA) of pipelines and related components. This methodology is particularly useful in the assessment of existing systems when linear elastic numerical analysis shows that local stresses may exceed the elastic design limits. Two case studies are presented showing analyses performed with Abaqus [5], a commercial, general purpose FEA software package. The first case study provides an assessment of a large diameter elbow where the stress on the outer fibers of the intrados exceeded the longitudinal stress limits from B31.8. The second case study examines an assessment of a tee connection where the stresses on the ID exceeded the yield strength of the component. In addition to the case studies, the paper also presents the results of a full-scale test that demonstrated what margin was present when the numerical calculations were based on specified minimum properties. This paper is not intended to revise or replace any provision of B31.4 and/or B31.8 [1, 2]. Instead, it provides the means for calculating load factors that can be used with an elastic-plastic analysis approach in a manner that provides the same design margins as the ASME B31 codes. The approach described in this paper is intended for use in the detailed FEA of pipelines and their associated components.

Combined CCTV and leak detection technology for in-service water transmission mains

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
Brian youngpyo Jo ◽  
Jon Boon
Keyword(s):  
Large Diameter ◽  
Leak Detection ◽  
Inspection System ◽  
The Past ◽  
Leak Location ◽  
Detection Technology ◽  
Service Water ◽  
Water Mains ◽  
Water Transmission

The reduction of Non-Revenue Water (NRW) through leakage detection is gaining ever higher significance for well-run water utilities. Tethered leak detection technology has become an essential tool for detecting the presence pinpointing the location as well as estimating the magnitude of leaks in large diameter (300 mm and above) water transmission mains of all pipe materials. For the past 7 years, inline CCTV inspection has also been available for in-service water mains using the Sahara® tethered video inspection system. These two technologies were used independently, which required two surveys for the same pipeline to deliver leak detection and CCTV inspection. This paper introduces Sahara AV, tethered combined leak detection and CCTV inspection technology designed to deliver multi functions such as leak detection, leak location and CCTV inspection through only one deployment for in-service water mains; recently wall thickness assessment has also been added to the list of technologies which can be mounted on the Sahara system. This paper introduces the Sahara AV system along with its specifications and explains the mechanism adopted to introduce the sensor into the live pipeline. The paper also discusses Sahara case study from Asia describing the benefits and return on investment experienced by clients that have engaged with programs involving Sahara technology.

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