Structural Reliability of Free Spanning Pipelines

2014 ◽  
Author(s):  
F. Van den Abeele ◽  
F. Boël ◽  
J.-F. Vanden Berghe
Keyword(s):  
Soil Properties ◽  
Fatigue Damage ◽  
Structural Reliability ◽  
Flow Direction ◽  
Unit Weight ◽  
Soil Conditions ◽  
Soil Parameters ◽  
Span Length ◽  
Form Analysis ◽  
Reliability Method

When installing subsea pipelines on an uneven seabed, the free spans can be vulnerable to fatigue damage caused by vortex induced vibrations (VIV). Indeed, even moderate currents can induce vortex shedding, alternately at the top and the bottom of the pipeline, at a rate determined by the flow velocity. Each time a vortex sheds, a force is generated in both the in-line and cross-flow direction, causing an oscillatory multi-mode vibration. This vortex induced vibration can give rise to fatigue damage of submarine pipeline spans, especially in the vicinity of the girth welds. Traditional design for VIV is recommended in DNV-RP-F105, which limits the allowable free span length and implies whether (and when) seabed interventions are required. The traditional DNV-RP-F105 design method is based on a semi-empirical approach, where the allowable span length depends on the pipe properties (diameter, wall thickness, coating, steel SN_curves, …), the sea state (current velocity, wave induced velocity and period) and the soil conditions (submerged unit weight, undrained shear strength, bearing capacity,…). All these input parameters, however, exhibit a certain extent of scatter and uncertainty. This paper presents a risk based evaluation of free spans, by applying the principles of structural reliability theory to the problem of long free spanning pipelines subjected to VIV. First, a fully deterministic on-bottom roughness analysis is performed to introduce numerical tools for free span analysis. Then, a sensitivity analysis on soil parameters is presented to show significant influence of soil properties on free span predictions. To study the implications of uncertainty in soil properties, a First Order Reliability Method (FORM) analysis is presented at the end of this paper, where the soil properties are introduced as stochastic variables.

Influence of cross correlation between soil parameters on probability of failure of simple cohesive and c-ϕ slopes

2016 ◽  
Vol 53 (5) ◽  
pp. 839-853 ◽  
Author(s):  
Sina Javankhoshdel ◽  
Richard J. Bathurst
Keyword(s):  
Slope Stability ◽  
Soil Properties ◽  
Cross Correlation ◽  
Friction Angle ◽  
Probability Of Failure ◽  
Unit Weight ◽  
Soil Parameters ◽  
Design Charts ◽  
Soil Slopes ◽  
Cross Correlations

This paper focuses on the calculation of probability of failure of simple unreinforced slopes and the influence of the magnitude of cross correlation between soil parameters on numerical outcomes. A general closed-form solution for cohesive slopes with cross correlation between cohesion and unit weight was investigated and results compared with cases without cross correlation. Negative cross correlations between cohesion and friction angle and positive cross correlations between cohesion and unit weight, and friction angle and unit weight were considered in the current study. The factors of safety and probabilities of failure for the slopes with uncorrelated soil properties were obtained using probabilistic slope stability design charts previously reported by the writers. Results for cohesive soil slopes and positive cross correlation between cohesion and unit weight are shown to decrease probability of failure. Probability of failure also decreased for increasing negative cross correlation between cohesion and friction angle, and increasing positive correlation between cohesion and unit weight, and friction angle and unit weight. Probabilistic slope stability design charts presented by the writers in an earlier publication are extended to include cohesive-frictional (c-[Formula: see text]) soil slopes with and without cross correlation between soil input parameters. An important outcome of the work presented here is that cross correlation between random values of soil properties can reduce the probability of failure for simple slope cases. Hence, previous probabilistic design charts by the writers for simple soil slopes with uncorrelated soil properties are conservative (safe) for design. This study also provides one explanation why slope stability analyses using uncorrelated soil properties can predict unreasonably high probabilities of failure when conventional estimates of factor of safety suggest a stable slope.

scholarly journals Changes in Grassland Chemical Soil Parameters Four Years after Cessation of Different Fertilisation with Compost and Slurry

2018 ◽  
Vol 66 (1) ◽  
pp. 211-218
Author(s):  
Marie Štýbnarová ◽  
Oldřich Látal ◽  
Jan Hladký ◽  
Monika Hradilová ◽  
Jiří Skládanka ◽  
...  
Keyword(s):  
Soil Properties ◽  
Positive Influence ◽  
Point Of View ◽  
Soil Conditions ◽  
Soil Parameters ◽  
Chemical Soil ◽  
Organic Fertilisers ◽  
Small Plot ◽  
Stocking Rates

The aim of this study was to evaluate changes in chemical soil properties of permanent grasslands after the cessation of their regular utilisation and organic fertilisation. A long‑term small plot trial was established in 2004 in locality Rapotín. During 2004 – 2012 the experiment was fertilised with compost and slurry, both with the range of stocking rates 0.9, 1.4, and 2.0 livestock units (LU).ha−1 (corresponding to 54, 84, and 120 kg N.ha−1). It was further observed the unfertilised grassland as control. The plots were cut 2 – 4 times per year depending on given dose of fertiliser. During 2013 –2016 the regular management was ceased and the grasslands were completely abandoned. It was found statistically significant influence of the year and the type of fertiliser almost for all evaluated parameters. The dose of nitrogen was not significant. On the basis of our results we can conclude, that the both types of the organic fertilisers had a positive influence on the chemical soil properties, however, the compost manifested itself as the better fertiliser than the slurry from this point of view. In 2016, four years after the last application of the organic fertilisers, there were found the better chemical soil conditions in the treatments previously fertilised with compost.

Fatigue From Vortex-Induced Vibrations of Free Span Pipelines Using Statistics of Current Speed and Direction

2003 ◽  
Author(s):  
Rune Yttervik ◽  
Carl M. Larsen ◽  
Gunnar K. Furnes
Keyword(s):  
Fatigue Damage ◽  
Current Velocity ◽  
Current Flow ◽  
Flow Direction ◽  
Cross Flow ◽  
Longitudinal Axis ◽  
Current Speed ◽  
Parameter Study ◽  
Span Length ◽  
Vortex Induced Vibrations

A section of a sub sea pipeline that is suspended between two points on an uneven seafloor is often referred to as ‘a free span pipeline’. Pipelines, installed on a seabed with a highly irregular topography, may have to be designed with several free spans. If a free span is exposed to a current flow, vortex-induced vibrations (VIV) of the suspended part of the pipeline may occur. These vibrations may cause unacceptable fatigue damage in the structure. Statistical distributions of current speed and direction close to a small mountain on the seabed (approximately 20 m high and 40 m wide) are established based on full-scale measurements of the current velocity in the area. Some results from recent model tests of VIV in free span pipelines, including some tests in which the flow direction was not perpendicular to the longitudinal axis of the pipe, are shown. These results indicate that it is sufficient to use the component of the current velocity vector that is normal to the pipe when using empirical models for estimating the response due to vortex shedding. An existing empirical model for analysis of VIV [1] is extended such as to include oscillations in the same plane as the current flow (in-line VIV). The effect of including the directional variability of the current when estimating the VIV fatigue damage, using the extended VIV model on a typical free span pipeline, is demonstrated, and found to be of great importance. A parameter study, in which the length of the free span is varied, is also carried out. The conclusion from this study is that a reduction of free span length affects the parameters that govern the accumulation of fatigue damage differently. Stresses are increased, but the number of current conditions capable of inducing VIV is reduced when the length of the span is reduced. It is therefore difficult to predict whether the accumulated damage will increase or decrease when the span length is reduced, and detailed analyses are required for each particular free span and current distribution. The damage from in-line VIV is generally lower than the damage from the cross flow VIV for all but the shortest span lengths.

External Corrosion Growth-Rate From Soil Properties

2010 ◽  
Author(s):  
Khalid A. Farrag
Keyword(s):  
Growth Rate ◽  
Corrosion Rate ◽  
Soil Properties ◽  
Growth Rates ◽  
Soil Conditions ◽  
Soil Parameters ◽  
Time Interval ◽  
Soil Redox Potential ◽  
Corrosion Rates ◽  
External Corrosion

External corrosion growth rate is an essential parameter to establish the time interval between successive pipe integrity evaluations. Actual corrosion rates are difficult to measure or predict. NACE Standard RP0502 [1] recommends several methods including comparison with historical data, buried coupons, electrical resistance (ER), and Linear Polarization Resistance (LPR) measurements. This paper presents a testing program and procedure to validate the use of the LPR and ER methods to enhance the estimation of corrosion growth rates and improve the selection of reassessment intervals of gas transmission pipelines. Laboratory and field tests were performed using the LPR and ER technologies. The evaluation of soil parameters that affect localized corrosion included its type, moisture content, pH, resistivity, drainage characteristics, chloride and sulfite levels, and soil Redox potential. The results show that the LPR device provides instantaneous measurement of corrosion potential and it may be used to reflect the variations of corrosion rates with the changes of soil conditions, moisture, and temperature. However, LPR measurements are more efficient in saturated soils with uncertainty about its validity in partially and totally dry soils. Consequently, seasonal changes in soil conditions make it difficult to estimate total corrosion growth rate. On the other hand, the measurements using the ER method provided consistent estimates for long-term corrosion growth rates. Corrosion growth rates were also evaluated from a previous study by the National Institute of Standards (NIST) [2]. A procedure was developed to correlate soil properties to corrosion rates from the ER measurements and NIST data. The procedure was implemented in a computer program to provide an estimate of corrosion rate based on the soil input data and allows the operator to use the ER probes to improve the reliability of corrosion rate estimates.

scholarly journals Influence of soil properties on the heartwood colour of Juglans mandshurica var. sachalinensis in a cool temperate forest

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Kobayashi Makoto ◽  
Elizaveta Susloparova ◽  
Ikutaro Tsuyama ◽  
Takuya Shimase ◽  
Satoshi Nakaba ◽  
...  
Keyword(s):  
Soil Properties ◽  
Intraspecific Variation ◽  
Temperate Forest ◽  
Temperate Forests ◽  
Local Scale ◽  
Soil Conditions ◽  
Soil Parameters ◽  
Juglans Mandshurica ◽  
Cool Temperate ◽  
Cool Temperate Forest

AbstractHeartwood colour is often an important factor in determining timber prices. However, the determinants of intraspecific variation in heartwood colour, which is useful information for sustainable wood marketing, are little understood, especially at the local scale in cool temperate forests. Because heartwood is produced as a secondary compound and photosynthesis is regulated by nitrogen (N) in cool temperate forests, we hypothesized that (1) soil conditions determine heartwood colour even at a local scale within a tree species and (2) N, specifically, can be an important driver of the intraspecific variation in heartwood colour in the trees of cool temperate forests. To test these hypotheses, we investigated the relationship between the colour values (luminescence, redness, and yellowness) of heartwood from Juglans mandshurica var. sachalinensis and the soil parameters in a cool temperate forest. Among the soil properties, not soil N but soil magnesium (Mg) contents alone had a significant influence on the redness and yellowness of the heartwood. Higher soil Mg contents resulted in increased redness and yellowness of the heartwood in our study, probably due to the increase in phenolics and the colouring of the tannins in the heartwood with Mg. Our results indicate that even at a local scale, soil condition can determine the intraspecific variation in heartwood colour and that forest managers can utilize edaphic information to predict heartwood colour for timber marketing.

Usage of visual and near-infrared spectroscopy to predict soil properties in forest stands

2020 ◽  
Author(s):  
Felix Thomas ◽  
Rainer Petzold ◽  
Carina Becker ◽  
Ulrike Werban
Keyword(s):  
Soil Properties ◽  
Near Infrared ◽  
Soil Survey ◽  
Soil Conditions ◽  
Soil Parameters ◽  
Forest Conversion ◽  
Electromagnetic Spectrum ◽  
Forest Stands ◽  
Site Mapping ◽  
The Impact

<p>There is a high demand for information about soil conditions in forests stands as it is crucial to ensure sustainable management, to maintain ecosystem services, to preserve timber production and establish proper pest management. Nowadays, the main drivers for changes in soil conditions are element input, forest conversion, subsoil liming and changing climate. These drivers influence nutrients and water availability and are challenging current site mapping methods. However, for impact assessment high-resolution and up-to-date information is needed. As laboratory analysis is time consuming and expensive, alternative approaches are preferred.</p><p>The project DIGI-Humus uses methods of reflectance spectroscopy in the visual and near-infrared-region of the electromagnetic spectrum for indirect measurement and prediction of physical and chemical soil properties in forest stands. For this purpose, spectral data were collected under laboratory conditions to build a database of forest soils. We used retained samples from Saxony soil survey, measuring both Oh and Ah horizons. To ensure data quality, we developed our own protocol based on literature review and self-conducted test measurements. The data has been used to successfully calibrate regression models based on different forest types and soil horizons to predict the soil parameters C and N content, C/N ratio and pH-value.</p><p>To improve model performance and test its generalization capability, the created library has been extended with new samples from a field campaign conducted in 2019 at an additional local test site. Using this data, the impact of adding new information to the modelling process and the robustness of the models could be evaluated.</p><p>The results of this research will be used to assess forest sites regarding nutrients availability, as basis for the development of site specific management strategies and to enhance and improve current methods of periodic site mapping of forest stands.</p>

scholarly journals Land Uses, Altitude and Texture Effects on Soil Parameters. A Comparative Study in Two Districts of Nagaland, Northeast India

Agriculture ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 171
Author(s):  
Gaurav Mishra ◽  
Rosa Francaviglia
Keyword(s):  
Soil Properties ◽  
Soil Texture ◽  
Soil Parameters ◽  
Available Phosphorus ◽  
Land Uses ◽  
Management Options ◽  
Available N ◽  
P Content ◽  
Significant Difference ◽  
Soc Stocks

Northeast (NE) India is a typical tropical ecosystem with a luxuriant forest vegetation cover, but nowadays forests are under stress due to exploitation and land use changes, which are known to affect soil health and productivity. However, due to a scarcity of data, the influence of land uses and altitude on soil properties of this peculiar ecosystem is poorly quantified. This study presents the changes in soil properties in two districts of Nagaland (Mon and Zunheboto) in relation to land uses (forest, plantation, jhum and fallow jhum), altitude (<500 m, 500–1000 m, >1000 m) and soil texture (coarse, medium, fine). For this, a random soil sampling was performed in both the districts. Results indicated that soil organic carbon (SOC) stocks and available potassium (K) were significantly influenced by land uses in the Mon district, while in Zunheboto a significant difference was observed in available phosphorus (P) content. SOC stocks showed an increasing trend with elevation in both districts. The influence of altitude on P was significant and the maximum concentration was at lower elevations (<500 m). In Mon, soil texture significantly affected SOC stocks and the available N and P content. The variability in soil properties due to land uses, altitudinal gradients and textural classes can be better managed with the help of management options, which are still needed for this ecosystem.

scholarly journals Time-Dependent Reliability Analysis of Reinforced Concrete Beams Subjected to Uniform and Pitting Corrosion and Brittle Fracture

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1820
Author(s):  
Mohamed El Amine Ben Seghier ◽  
Behrooz Keshtegar ◽  
Hussam Mahmoud
Keyword(s):  
Reinforced Concrete ◽  
Brittle Fracture ◽  
Reliability Analysis ◽  
Pitting Corrosion ◽  
Structural Reliability ◽  
Time Dependent ◽  
State Function ◽  
Rc Beams ◽  
Highly Nonlinear ◽  
Reliability Method

Reinforced concrete (RC) beams are basic elements used in the construction of various structures and infrastructural systems. When exposed to harsh environmental conditions, the integrity of RC beams could be compromised as a result of various deterioration mechanisms. One of the most common deterioration mechanisms is the formation of different types of corrosion in the steel reinforcements of the beams, which could impact the overall reliability of the beam. Existing classical reliability analysis methods have shown unstable results when used for the assessment of highly nonlinear problems, such as corroded RC beams. To that end, the main purpose of this paper is to explore the use of a structural reliability method for the multi-state assessment of corroded RC beams. To do so, an improved reliability method, namely the three-term conjugate map (TCM) based on the first order reliability method (FORM), is used. The application of the TCM method to identify the multi-state failure of RC beams is validated against various well-known structural reliability-based FORM formulations. The limit state function (LSF) for corroded RC beams is formulated in accordance with two corrosion types, namely uniform and pitting corrosion, and with consideration of brittle fracture due to the pit-to-crack transition probability. The time-dependent reliability analyses conducted in this study are also used to assess the influence of various parameters on the resulting failure probability of the corroded beams. The results show that the nominal bar diameter, corrosion initiation rate, and the external loads have an important influence on the safety of these structures. In addition, the proposed method is shown to outperform other reliability-based FORM formulations in predicting the level of reliability in RC beams.

scholarly journals Biochar Improves Maize Growth but Has a Limited Effect on Soil Properties: Evidence from a Three-Year Field Experiment

2021 ◽  
Vol 13 (7) ◽  
pp. 3617
Author(s):  
Agnieszka Medyńska-Juraszek ◽  
Agnieszka Latawiec ◽  
Jolanta Królczyk ◽  
Adam Bogacz ◽  
Dorota Kawałko ◽  
...  
Keyword(s):  
Low Temperature ◽  
Field Experiment ◽  
Soil Properties ◽  
High Efficiency ◽  
Crop Yields ◽  
Temperate Climate ◽  
Soil Conditions ◽  
Maize Growth ◽  
Chemical Soil ◽  
Physical And Chemical

Biochar application is reported as a method for improving physical and chemical soil properties, with a still questionable impact on the crop yields and quality. Plant productivity can be affected by biochar properties and soil conditions. High efficiency of biochar application was reported many times for plant cultivation in tropical and arid climates; however, the knowledge of how the biochar affects soils in temperate climate zones exhibiting different properties is still limited. Therefore, a three-year-long field experiment was conducted on a loamy Haplic Luvisol, a common arable soil in Central Europe, to extend the laboratory-scale experiments on biochar effectiveness. A low-temperature pinewood biochar was applied at the rate of 50 t h−1, and maize was selected as a tested crop. Biochar application did not significantly impact the chemical soil properties and fertility of tested soil. However, biochar improved soil physical properties and water retention, reducing plant water stress during hot dry summers, and thus resulting in better maize growth and higher yields. Limited influence of the low-temperature biochar on soil properties suggests the crucial importance of biochar-production technology and biochar properties on the effectiveness and validity of its application in agriculture.

scholarly journals Research trends of microplastics in the soil environment: Comprehensive screening of effects

2021 ◽  
Author(s):  
Shin Woong Kim ◽  
Matthias C. Rillig
Keyword(s):  
Soil Properties ◽  
Additional Data ◽  
Soil Property ◽  
Dry Weight ◽  
Current Data ◽  
Soil Biota ◽  
Soil Parameters ◽  
Soil Environment ◽  
Soil System ◽  
Sensitivity Distribution

AbstractWe collated and synthesized previous studies that reported the impacts of microplastics on soil parameters. The data were classified and integrated to screen for the proportion of significant effects, then we suggest several directions to alleviate the current data limitation in future experiments. We compiled 106 datasets capturing significant effects, which were analyzed in detail. We found that polyethylene and pellets (or powders) were the most frequently used microplastic composition and shape for soil experiments. The significant effects mainly occurred in broad size ranges (0.1–1 mm) at test concentrations of 0.1%–10% based on soil dry weight. Polyvinyl chloride and film induced significant effects at lower concentrations compared to other compositions and shapes, respectively. We adopted a species sensitivity distribution (SSD) and soil property effect distribution (SPED) method using available data from soil biota, and for soil properties and enzymes deemed relevant for microplastic management. The predicted-no-effect-concentration (PNEC)-like values needed to protect 95% of soil biota and soil properties was estimated to be between 520 and 655 mg kg−1. This study was the first to screen microplastic levels with a view toward protecting the soil system. Our results should be regularly updated (e.g., quarterly) with additional data as they become available.

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