A Semi Submersible in Combined Extreme Waves and Current: Comparison of Model Tests and Existing Software

2007 ◽  
Author(s):  
Anne Katrine Bratland ◽  
Sverre Haver ◽  
Carl Trygve Stansberg ◽  
Fuwei Zhang ◽  
Joachim Allers ◽  
...  
Keyword(s):  
Production Systems ◽  
Dynamic Loads ◽  
Test Results ◽  
Sea Waves ◽  
Extreme Waves ◽  
Calculation Methods ◽  
Steady Current ◽  
Current Interaction ◽  
Extreme North ◽  
Mean Current

Floating production systems are often exposed to combined waves and current. Normally, the effects from a steady current are neglected in the calculation methods for dynamic loads and motions. In some parts of the world the current velocities can be so large that neglecting wave-current interaction effects is questionable. Computer programs that handle wave-current interaction have been available for decades. However, so far very little results have been documented which validate the theories. Model test results for a semi submersible in extreme North Sea waves are presented, with and without current. The comparison with wave-current interaction computer models shows that the effect is generally over-estimated for the present case with a mean current velocity equal to 1.3 m/sec.

The Response of Defects Containing Water under Dynamic Loads

2011 ◽  
Vol 225-226 ◽  
pp. 933-936 ◽  
Author(s):  
Zhe Ming Zhu
Keyword(s):  
Equation Of State ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Strain Rate ◽  
Difference Method ◽  
Failure Criterion ◽  
Explosive Charge ◽  
Dynamic Loads ◽  
Test Results ◽  
Simulation Results

A crater blasting model of rock with pre-existing defects under blasting loads is established by using finite difference method. The defects are saturated with water and are randomly distributed. The defects include voids, pores and small open joints. A shock equation of state (EOS), obtained from the existing test results, is employed for the granite near the explosive charge, and for the granite far from the charge, a linear EOS is applied. A modified principal stress failure criterion is applied to determining the granite statuses. The granite dynamic strengths, which increase with strain rate, are calculated from the existing test results. The simulation results show that under blasting, the strength of wet rock is lower than that of dry rock.

Solving Decommissioning and Abandonment Problems When Planning to Shear 9 5/8-inch Casing in a 13 5/8-inch × 10k RAM BOP

2021 ◽  
Author(s):  
David Earl Cain ◽  
Keith Albert Klopfenstein ◽  
James Robert McMullan
Keyword(s):  
Calculation Method ◽  
Shear Force ◽  
Statistical Treatment ◽  
The Novel ◽  
Test Results ◽  
Calculation Methods ◽  
Working Pressure ◽  
Lower Shear ◽  
Validation Testing ◽  
Force Pressure

Abstract A decommissioning and abandonment requirement to shear 9 5/8-inch casing in certain circumstances with a 13 5/8-inch × 10,000 psi rated working pressure, RWP, Shear RAM type blowout preventer, BOP, resulted in a need to develop a novel casing shear device and shear calculation method. Results of shear testing, future engineering planning guidance, the new shear calculation method, and comparison to legacy technology are included in this paper. Interaction with the end user to understand requirements, a five-step problem solving procedure, a basis of design process, materials justification, verification analysis, validation testing, and describing an improved shear operator force/pressure calculation are all described. Shear larger casing in the required and restrictive RAM BOP and well bore presented a problematic challenge. Equally, tubular fish size was required to support fishing extraction operations following shear. Validation test results exceeded requirements and resulted in the need for a new approach to the shear calculation method. The novel shear RAM geometry was developed utilizing shear calculation methods which were based on legacy considerations. API 16A shear validation procedures and two legacy shear calculation methods where employed. Shear calculations are used to anticipate the RAM BOP operator pressures required to shear a specific tubular. The larger than historically allowed casing size to be sheared in a 13 5/8-inch × 10,000 psi RAM BOP meant higher operator pressures were anticipated for each operator option. A Novel shear RAM geometry was developed as a design intent to lower shear force/pressure. There was an observation during validation testing that the geometry exceeded expectations to lower shear pressure significantly. This observation led to a conclusion that an improved shear calculation method was required for this application. This novel calculation method description / statistical treatment, test results, RAM design methods, and tabular shear engineering planning information are included in this paper. One additional requirement of the shear RAM geometry was to provide an upper and lower fish deformed surface which could be easily retrieved thru the 13 5/8-inch BOP bore. An additional observation was that the fish width requirement was achieved. The novel shear calculation method allows an engineer to precisely plan for bonnet actuation pressures when larger casing is sheared. The precise calculation of shear force/pressure also assists with BOP operator size and type selection. The engineer will gain casing size versus shear pressure for specific operator options in tabular format. Planners will gain insight into tubular fish deformation estimation allowing mitigation of tubular extraction risk during operations planning.

scholarly journals WAVE-CURRENT INTERACTION OVER SEABEDS WITH DIFFERENT ROUGHNESS: A STATISTICAL ANALYSIS

2017 ◽  
pp. 16
Author(s):  
Carla Faraci ◽  
Pietro Scandura ◽  
Enrico Foti
Keyword(s):  
Gaussian Distribution ◽  
Current Velocity ◽  
Mass Conservation ◽  
Distribution Functions ◽  
Wave Velocities ◽  
Velocity Statistics ◽  
Steady Current ◽  
Wave Effects ◽  
Current Interaction ◽  
Rippled Bed

Wave-current flow over seabeds covered with different roughness has been studied in order to deepen the knowledge on the statistical properties of the near-bed velocity. The results of three different experimental campaigns performed in the presence of a sandy bed, a gravel bed and a rippled bed, carried out superimposing a steady current onto an orthogonal wave, have been analysed. The statistics of the current velocity, including the wave effects on the steady current have been investigated. It has been observed that in the absence of waves, the fluctuations of the near-bed velocities closely follow a Gaussian distribution. When waves are also present, in order to obtain consistent near-bed velocity statistics, it is necessary to decouple the velocity events in the current direction by taking into account the sign of the wave velocities. In the latter case, the nature of the distribution functions is influenced by the mass conservation principle. A Gaussian distribution well describes the turbulent fluctuations obtained by removing the phase averaged velocity from the current velocity.

scholarly journals Comparative Study of Calculation Models for the Fire Resistance of Hollow Steel Columns Filled with Concrete

2020 ◽  
Author(s):  
Farid Fellah
Keyword(s):  
Comparative Study ◽  
Computer Program ◽  
Fire Resistance ◽  
Applied Load ◽  
Computer Code ◽  
Test Results ◽  
Calculation Methods ◽  
Steel Columns ◽  
Design Engineers ◽  
The Comparative Study

Various calculation methods are proposed in codes for the evaluation of fire resistance of hollow steel columns filled with concrete, but the use of some of them may be very tedious for design engineers, and it may be interesting to have more practical tools at their disposal. In the comparative study presented here, three methods based on different procedures are investigated. Kodur’s method is a set of formulas allowing to calculate the fire resistance or the maximum applied load. Potfire is a computer program for which a user’s manual is provided and clean instructions describe how to introduce the data. SAFIR is a non-linear computer code that can simulate the behavior of structures under fire conditions. Comparisons are made between the results obtained by the three methods and test results. The differences are analyzed, and the influence of some parameters is examined. From the results obtained in this comparative study, it is possible to say in which cases each method can be used.

The Base Pressure Problem in Transonic Turbine Cascades

1979 ◽  
Author(s):  
C. H. Sieverding ◽  
M. Stanislas ◽  
J. Snoek
Keyword(s):  
Theoretical Calculations ◽  
Base Pressure ◽  
Test Results ◽  
Pressure Data ◽  
Calculation Methods ◽  
Flow Parameters ◽  
Wide Range ◽  
Pressure Calculation ◽  
Transonic Turbine ◽  
Turbine Cascades

Base pressure data were systematically collected at VKI during recent years on a great variety of cascades operated over a wide range of outlet March numbers. An attempt is made to correlate these data by relating the base pressure to important cascade and flow parameters. Details about the trailing edge flow are obtained by using an enlarged model simulating the overhang section of convergent turbine cascades. The experimental cascade and model test results are compared with theoretical calculations using base pressure calculation methods.

Buckling Strength and Parameter Analysis on Stiffened Flange Plate under Compression

2013 ◽  
Vol 838-841 ◽  
pp. 1159-1164
Author(s):  
Wen Ru Lu ◽  
Jin Di
Keyword(s):  
Highway Bridges ◽  
Parameter Analysis ◽  
Steel Bridge ◽  
Design Codes ◽  
Test Results ◽  
Calculation Methods ◽  
Buckling Strength ◽  
Calculation Results ◽  
Design Theories ◽  
Plate Width

The buckling strength of stiffened flange plate under compression was researched by referring to BS5400, Japanese Specification for Highway Bridges and Eurocode in order to research calculation methods of stiffened flange plate under compression in foreign design codes of steel bridge which were based on different design theories. Test results of ultimate bearing capacity of stiffened flange plate under compression were compared with calculation results according to those codes. The effects of constructive parameters such as the thickness of flange plate, width of subpanel, thickness of plate and width of inclined web plate in rib on buckling strength of stiffened flange plate under compression were researched respectively. The results showed, when increasing the thickness of flange or decreasing the width of plate divided by rib's web, calculation results of buckling strength increased at first and then leveled off according to Japanese Specification for Highway Bridges. However the buckling strength declined slowly according to BS5400 and Eurocode. When increasing the thickness of plate or decreasing the width of inclined web plate of rib, calculation results increased at the beginning and leveled out then. If ribs satisfy the rigidity demands, calculation results of buckling strength would remain the same as the sizes of rib were changed according to Japanese Specification for Highway Bridges.

Settlement Calculation and Analysis of Ground Improved by Dynamic Compaction at RSGT Project

2012 ◽  
Vol 446-449 ◽  
pp. 1426-1431
Author(s):  
Zhi Guang Qin ◽  
Yan Luo ◽  
Ying Xi He
Keyword(s):  
Saudi Arabia ◽  
Coral Reefs ◽  
Red Sea ◽  
Cohesive Soil ◽  
Dynamic Compaction ◽  
Actual Condition ◽  
Test Results ◽  
Calculation Methods ◽  
Settlement Calculation ◽  
Semi Empirical

Red Sea coral reefs in Saudi Arabia were dredged and reclaimed firstly, and then were treated by dynamic compaction as non-cohesive soil ground. Consolidated condition of improved ground within different depth is in different. Calculating settlements for different state ground should consider actual condition. Several semi-theoretical and semi-empirical settlement calculation methods mainly including Terzaghi’s method(1996), Teng’s method(1969), Meyerhof’s method（1956）are applied and analyzed to investigate the actual condition of improved ground according to the RSGT project test results, and the differences are proposed among these three methods.

Pitting Load Capacity of Helical Gears

2007 ◽  
Author(s):  
Bernd-Robert Ho¨hn ◽  
Peter Oster ◽  
Gregor Steinberger
Keyword(s):  
Calculation Method ◽  
Load Distribution ◽  
Load Capacity ◽  
Test Results ◽  
Calculation Methods ◽  
Helical Gears ◽  
Capacity Calculation ◽  
Overlap Ratio ◽  
Tooth Flank

In experimental analyzes the pitting load capacity of case carburized spur and helical gears is determined in back-to-back test rigs. The research program with one type of spur and 8 types of helical gears includes tests for the determination of influences of varying load distribution, overlap ratio and transmission ratio. The test results are presented and evaluated on the basis of the pitting load capacity calculation methods of ISO 6336-2/DIN 3990, part 2. A new DIN/ISO compatible calculation method for pitting load capacity is presented. This new calculation method comprehends helical gears more adequate than ISO 6336-2 / DIN 3990, part 2 and has the possibility to consider tooth flank modifications. The new calculation method is applied on test results and gears of a calculation study. It shows better accordance with the experimental test results than the present ISO 6336-2 / DIN 3990, part 2.

scholarly journals Load of gondola with floor decking at handling operations

2015 ◽  
Vol 2015 (4) ◽  
pp. 45-49
Author(s):  
Владимир Кобищанов ◽  
Vladimir Kobishchanov ◽  
Кирилл Герасимов ◽  
Kirill Gerasimov ◽  
Дмитрий Расин ◽  
...  
Keyword(s):  
Maximum Stress ◽  
The Body ◽  
Dynamic Loads ◽  
Normal Stresses ◽  
Test Results ◽  
Load Drop ◽  
Small Areas ◽  
Car Body ◽  
Deflected Mode ◽  
Solid Type

A gondola with a body of solid type – an eco-nomically effective unit of a rollingstock. Most of the damages of gondola bodies is caused at handling operations with the failure of requirements observance established. In the paper the assessment of deflected mode body in the body at the lump load drop with the mass of 500 kg is carried out. Normal stresses and travels arising at the blow of load in the sections of joints of frame beams between each other, side and end walls are analyzed. The values of stresses three times higher than the foreseen ones with “Standards…” are adopted as reference valuations. It is substantiated by test results and the comparison of material characteristics at deadweight and dynamic loads. As a result of car body multichoice computations on basis of the detailed MCE there was established the following: the closer the place of a lump blow to a supporting longitudinal to the car body end is, the stresses are higher in it. Stresses arising in the supporting longitudinal situated between an end girder and a body bolster beam reach 998 H/mm, at the same time in the middle of the car body of a gondola they do not exceed 450 H⁄mm². If a load lump falls down on the joint of cross-beams and longitudinal ones, then stresses in their sections 10-15 times less, than if the fall were to a strengthening beam. In the main the maximum stress distribution is limited by small areas located between two neighboring crossbeams. The research results have shown, it is necessary that additional bearing elements absorbing a blow should be introduced in a frame.

scholarly journals Extreme waves at Filyos, southern Black Sea

2011 ◽  
Vol 11 (3) ◽  
pp. 659-666 ◽  
Author(s):  
E. Bilyay ◽  
B. O. Ozbahceci ◽  
A. C. Yalciner
Keyword(s):  
Black Sea ◽  
Rayleigh Distribution ◽  
Height Distribution ◽  
Extreme Waves ◽  
Black Sea Region ◽  
Average Value ◽  
Wave Measurement ◽  
Wave Height Distribution ◽  
Current Interaction ◽  
Surface Profiles

Abstract. A wave measurement project was carried out for a new port planned in Filyos, in the Western Black Sea region of Turkey. The measurement at a depth of 12.5 m lasted for a period of two years and 7949 records were obtained. During the analysis, it was noticed that there were 209 records in which H/Hs ratio was higher than 2.0. These higher waves in a record are called extreme waves in this study. Although the purpose of wave measurement is not to investigate extreme waves, it is believed that studying these unexpected waves could be interesting. Therefore, detailed statistical and spectral analyses on the extreme waves were done for the records. The analyses results show that the distribution of surface profiles of the records containing extreme waves deviates from Gaussian distribution with the negative skewness changing between –0.01 and –0.4 and with the high kurtosis in the range of 3.1–4.2. Although the probability of occurrence of the extreme waves is over-predicted by the Rayleigh distribution, a higher ratio of Hs/ηrms indicates that the wave height distribution can be represented by Rayleigh. The average value of the slope of the frequency spectrum at the high frequency range is proportional to f–9 which is much steeper than the typical wind-wave frequency power law, f–4, –5. The directional spreading is measured with the parameter Smax and it is in the range of 5–70 for the extreme wave records. The wave and current interaction was also investigated and it was found that in most cases, extreme waves occur when the wave and the current are almost aligned. Furthermore, it is observed that extreme waves appear within a group of high waves.

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