FEA Analysis of Subsea Mooring Suction Anchor Under Operation Condition

2015 ◽  
Author(s):  
Shuqin Wang ◽  
Jiaping Zhang ◽  
Jim Malachowski ◽  
Jubair Hossain ◽  
James Colling
Keyword(s):  
Structural Engineering ◽  
Structural Model ◽  
Limit State ◽  
Strength Analysis ◽  
Soil Parameters ◽  
Soil Reaction ◽  
Soil Pressure ◽  
Operation Condition ◽  
Limit States ◽  
Conservative Result

The analysis of a mooring suction anchor involves both geotechnical and structural engineering. The design starts with the geotechnical analysis of a mooring suction anchor where the design loads are used to determine the size of the mooring suction anchor. Typically, a conservative estimate would be made for the soil strength and analysis would involve several layers of soil with different properties. The mooring suction anchor is then designed using the relevant soil parameters for various limit states under the combined vertical, lateral, torsional, and moment loading. Soil pressures or reactions acting on a rigid steel mooring suction anchor for each limit state are calculated. The calculation results are then provided to structural engineers to perform strength analysis to verify the integrity of the anchor. Therefore, it is important to understand how the soil reactions interact with the suction anchor in the structural model. The current analysis used the soil reaction data developed for an in-place loading condition for a mooring suction anchor. The structure of the mooring suction anchor was modelled using a 3D finite element method. Two studies were performed. The first study performed the regular mapping of the soil pressure to the suction anchor. The second study assumed that all the loads would be applied on the mooring padeye and the bottom of the suction would be fixed. It was presumed that the second study would yield a conservative result. However, the analysis results showed that the second study did not provide a conservative result. Therefore, it is recommended that the care should be taken when making such assumptions in future studies.

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.

scholarly journals Serviceability limit state related to excessive lateral deformations to account for infill walls in the structural model

2015 ◽  
Vol 8 (3) ◽  
pp. 390-426 ◽  
Author(s):  
G. M. S. ALVA ◽  
J. KAMINSKI Jr ◽  
G. MOHAMAD ◽  
L. R. SILVA
Keyword(s):  
Structural Model ◽  
Limit State ◽  
Lateral Loads ◽  
Negative Effects ◽  
Limit States ◽  
Infill Walls ◽  
Practical Procedure ◽  
Interstory Drift ◽  
Diagonal Compression ◽  
Cracking Pattern

Brazilian Codes NBR 6118 and NBR 15575 provide practical values for interstory drift limits applied to conventional modeling in order to prevent negative effects in masonry infill walls caused by excessive lateral deformability, however these codes do not account for infill walls in the structural model. The inclusion of infill walls in the proposed model allows for a quantitative evaluation of structural stresses in these walls and an assessment of cracking in these elements (sliding shear diagonal tension and diagonal compression cracking). This paper presents the results of simulations of single-story one-bay infilled R/C frames. The main objective is to show how to check the serviceability limit states under lateral loads when the infill walls are included in the modeling. The results of numerical simulations allowed for an evaluation of stresses and the probable cracking pattern in infill walls. The results also allowed an identification of some advantages and limitations of the NBR 6118 practical procedure based on interstory drift limits.

Development of geotechnical limit state design

1995 ◽  
Vol 32 (1) ◽  
pp. 128-136 ◽  
Author(s):  
Geoffrey G. Meyerhof
Keyword(s):  
Limit State ◽  
Offshore Structures ◽  
Soil Parameters ◽  
Ultimate Limit State ◽  
Offshore Structure ◽  
Limit States ◽  
Limit State Design ◽  
Earth Structures ◽  
Earth Retaining Structures ◽  
Operational Constraints

The historical development of limit state design in geotechnical engineering is reviewed. Total and partial factors of safety used for the design of land–based and offshore structures are compared. It is found that the factors of safety in different codes for the ultimate and serviceability limit states design of earthworks, earth retaining structures, and land-based and offshore foundations are very similar. Partial factors in the ultimate limit state design are linked to the variability of the loads and soil parameters, the design approximations, and construction tolerances. They influence the nominal probability of failure of the type of structure considered and the seriousness of failure, which differ for land-based and offshore structures. These probabilities are compared with human fatality risks of common experiences. The serviceability limit states are governed by structural and operational constraints and the intended service life of the land-based or offshore structure. The corresponding partial factors are generally taken as unity. Key words : codes, earth structures, foundations, human risks, limit states design, probability of failures, factors of safety.

scholarly journals Elastostatics of Bernoulli–Euler Beams Resting on Displacement-Driven Nonlocal Foundation

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 573
Author(s):  
Marzia Sara Vaccaro ◽  
Francesco Paolo Pinnola ◽  
Francesco Marotti de Sciarra ◽  
Raffaele Barretta
Keyword(s):  
Boundary Conditions ◽  
Structural Engineering ◽  
Beam Deflection ◽  
Soil Reaction ◽  
Differential Problem ◽  
Reaction Field ◽  
Ill Posed ◽  
Elastic Responses ◽  
Benchmark Solutions ◽  
Well Posed

The simplest elasticity model of the foundation underlying a slender beam under flexure was conceived by Winkler, requiring local proportionality between soil reactions and beam deflection. Such an approach leads to well-posed elastostatic and elastodynamic problems, but as highlighted by Wieghardt, it provides elastic responses that are not technically significant for a wide variety of engineering applications. Thus, Winkler’s model was replaced by Wieghardt himself by assuming that the beam deflection is the convolution integral between soil reaction field and an averaging kernel. Due to conflict between constitutive and kinematic compatibility requirements, the corresponding elastic problem of an inflected beam resting on a Wieghardt foundation is ill-posed. Modifications of the original Wieghardt model were proposed by introducing fictitious boundary concentrated forces of constitutive type, which are physically questionable, being significantly influenced on prescribed kinematic boundary conditions. Inherent difficulties and issues are overcome in the present research using a displacement-driven nonlocal integral strategy obtained by swapping the input and output fields involved in Wieghardt’s original formulation. That is, nonlocal soil reaction fields are the output of integral convolutions of beam deflection fields with an averaging kernel. Equipping the displacement-driven nonlocal integral law with the bi-exponential averaging kernel, an equivalent nonlocal differential problem, supplemented with non-standard constitutive boundary conditions involving nonlocal soil reactions, is established. As a key implication, the integrodifferential equations governing the elastostatic problem of an inflected elastic slender beam resting on a displacement-driven nonlocal integral foundation are replaced with much simpler differential equations supplemented with kinematic, static, and new constitutive boundary conditions. The proposed nonlocal approach is illustrated by examining and analytically solving exemplar problems of structural engineering. Benchmark solutions for numerical analyses are also detected.

Combined flexure and torsion of I-shaped steel beams

1989 ◽  
Vol 16 (2) ◽  
pp. 124-139 ◽  
Author(s):  
Robert G. Driver ◽  
D. J. Laurie Kennedy
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Phase Behaviour ◽  
Inelastic Interaction ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Second Phase ◽  
Design Standards ◽  
Limit States ◽  
Interaction Diagram

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members. Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.

Anchor rod forces and maximum bending moments in sheet pile walls using the factored strength approach

1996 ◽  
Vol 33 (5) ◽  
pp. 815-821 ◽  
Author(s):  
A B Schriver ◽  
A J Valsangkar
Keyword(s):  
Water Pressure ◽  
Limit State ◽  
Bending Moment ◽  
Ultimate Limit State ◽  
Sheet Pile ◽  
Limit States ◽  
Working Stress ◽  
Geotechnical Design ◽  
Ultimate Limit State Design ◽  
Sheet Pile Wall

Recently, the limit states approach using factored strength has been recommended in geotechnical design. Some recent research has indicated that the application of limit states design using recommended load and strength factors leads to conservative designs compared with the conventional methods. In this study the influence of sheet pile wall geometry, type of water pressure distribution, and different methods of analysis on the maximum bending moment and achor rod force are presented. Recommendations are made to make the factored strength design compatible with conventional design. Key words: factored strength, working stress design, ultimate limit state design, anchored sheet pile wall, bending moment, anchor rod force.

scholarly journals Probability Calibration Of Load Duration Modification Factor For Timber Roofs In The Polish Mountain Zones

2014 ◽  
Vol 60 (2) ◽  
pp. 195-208
Author(s):  
T. Domański
Keyword(s):  
Limit State ◽  
High Stress ◽  
Life Time ◽  
Probabilistic Methods ◽  
Limit States ◽  
Term Limit ◽  
Load Duration ◽  
Maximum Likelihood Methods ◽  
Short And Long Term

Abstract The resistance parameters of timber structures decrease with time. It depends on the type of load and timber classes. Strength reduction effects, referred to as creep-rupture effects, due to long term loading at high stress ratio levels are known for many materials. Timber materials are highly affected by this reduction in strength with duration of load. Characteristic values of load duration and load duration factors are calibrated by means of using probabilistic methods. Three damage accumulation models are considered, that is Gerhard [1] model, Barret, Foschi[2] and Foshi Yao [3] models. The reliability is estimated by means of using representative short- and long-term limit states. Time variant reliability aspects are taken into account using a simple representative limit state with time variant strength and simulation of whole life time load processes. The parameters in these models are fitted by the Maximum Likelihood Methods using the data relevant for Polish structural timber. Based on Polish snow data over 45 years from mountain zone in: Zakopane – Tatra, Świeradów – Karkonosze, Lesko – Bieszczady, the snow load process parameters have been estimated. The reliability is evaluated using representative short – and long –term limit states, load duration factor kmod is obtained using the probabilistic model.

OPERATIONAL ASSESSMENT OF THE LIMIT STATE OF TRACTOR UNITS WITH THE USE OF INDICATOR COUNTERS

2021 ◽  
Vol 3 (144) ◽  
pp. 12-21
Author(s):  
Nikolay A. Petrishchev ◽  
◽  
Mikhail N. Kostomakhin ◽  
Aleksandr S. Sayapin ◽  
Igor’ M. Makarkin ◽  
...  
Keyword(s):  
Limit State ◽  
Technical Condition ◽  
Point Of View ◽  
Research Purpose ◽  
Diagnostic Tools ◽  
Diagnostic Process ◽  
Technical Documentation ◽  
Limit States ◽  
Limit Condition ◽  
Reliability Indicators

In accordance with GOST 20793-2009, the tractor and its components are subjected to resource diagnostics before maintenance. The technical condition of the components of the tractor or machine should be checked with the use of control and diagnostic equipment. Currently, the criteria for the limit state are significantly outdated and require revision from the point of view of tightening modern requirements for operational and economic characteristics and reliability indicators. (Research purpose) The research purpose is in analyzing the state of the issue and the current regulatory documentation and making proposals for remote monitoring of the criteria for the limit states of individual components and aggregates. (Materials and methods) The article presents an analysis of scientific and technical documentation, State standards of the Russian Federation and scientific papers on the problems of minimizing technological risks, diagnostics and control suitability for determining the maximum technical condition, and staged studies on the possibility of monitoring the operation of individual components and units online. The article notes the need to adjust the criteria for the maximum technical condition in accordance with the new designs of resource-determining units, aggregates and existing technical regulations. (Results and discussion). The article presents the justification of the diagnostic process and identified contradictions in the design of tractors and existing scientific and technical documentation and standards, and proposed option of using meters-identifiers when upgrading tractors as a system of built-in online diagnostic tools. (Conclusions) Timely, automated monitoring of the technical condition of tractors, which is based on comparing data with the criteria of the limit condition, serves as a justification for the effective operation of equipment with built-in devices for diagnostics, which allows minimizing agrotechnological risks.

Study on the Soil Fertility and Mapping in Ramasamudram-1 Microwatershed of Yadgir Taluk and District of Karnataka, India

2021 ◽  
Vol 12 (5) ◽  
pp. 348-360
Author(s):  
Rajendra Hegde ◽  
◽  
Mahendra Kumar ◽  
M. B. Niranjana K. V. ◽  
Seema, K. V. ◽  
...  
Keyword(s):  
Soil Fertility ◽  
Management Practices ◽  
Surface Soil ◽  
Soil Parameters ◽  
Soil Reaction ◽  
Entire Area ◽  
Maximum Area ◽  
Fertility Status ◽  
Major Nutrients ◽  
Soil Fertility Status

An investigation was under taken to study the soil fertility status of major nutrients, micronutrients and mapping in Ramasamudram-1 microwatershed of Yadgir taluk and district of Karnataka, India during the year 2019. Total seventy-four grid wise surface soil samples were collected at 320 m grid interval at 0-15 cm depth to assess the soil parameters (texture, pH, EC, OC, available P, K, S, Zn, Cu, Fe, Mn and B) and prepare the soil fertility maps through GIS using Kriging method. The results of the study indicated that, the texture of the soil varied from loamy sand to sand clay loam in surface. Soil reaction varied from acidic to neutral with non-saline in nature. The distribution of soil organic carbon (32%), available phosphorous (56%) and potassium (47%) status was found to be medium in most of the area of microwatershed. The available sulphur status was found to be low (57%) in maximum area of the microwatershed. The available zinc status was found to be sufficient (46%) in majority area of the microwatershed. The available copper, iron and manganese status of the soils were sufficient (58%) in entire area. Whereas available boron status was found to be low (57%) in maximum area of the microwatershed. Therefore, the study showed that, the soils of the microwatershed were medium in fertility status. There is need of proper fertilizer recommendation and soil management practices can be made productive thereby, increasing the crop yield.

Limit State of Torsion of Ship Hulls with Large Hatch Openings

2001 ◽  
Vol 45 (02) ◽  
pp. 95-102
Author(s):  
Yuren Hu ◽  
Bozhen Chen
Keyword(s):  
Cross Section ◽  
Structural Reliability ◽  
Limit State ◽  
Safety Margin ◽  
Plastic Shear ◽  
Torsional Moment ◽  
Limit States ◽  
Ship Hulls ◽  
Design Values ◽  
Bound Theorem

The limit state of torsion of ship hulls with large hatch openings is studied. A method to determine the distribution of the plastic shear flow on the hull cross section in the limit state by using the lower-bound theorem is presented together with the corresponding linear programming problem. The limit torsional moment of the hull cross section is obtained based on the distribution of the shear stress in the limit state. Three example limit states for typical containerships of different sizes with large hatch openings are calculated. The calculated limit torsional moments are compared with the design values of wave torque calculated by using the equations given by main classification societies in their rules. A rough estimate of the safety margin is obtained. The results show that for large containerships, it is necessary to pay attention to the safety with respect to torsion. The present method can serve as an effective tool in structural reliability analysis of ships with large hatch openings when the failure mode of torsion is taken into account.

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