A Study on the Impact Load Acting on an FPSO Bow by Steep Waves

2014 ◽  
Author(s):  
Sam-Kwon Hong ◽  
Jae-Moon Lew ◽  
Dong-Woo Jung ◽  
Hee-Taek Kim ◽  
Dong-Yeon Lee ◽  
...  
Keyword(s):  
Model Test ◽  
Impact Force ◽  
Impact Load ◽  
Impact Loads ◽  
Return Periods ◽  
Seakeeping Performance ◽  
Wave Heights ◽  
Wave Conditions ◽  
Steep Waves ◽  
The Impact

Among offshore floaters used to develop offshore resources, FPSO and FSO have a storage function whereas semi-submersible, Spar and TLP have only production function. The floaters with the storage function such as FPSO and FSO are designed as the typical ship type concept compared to the other floaters with small water plane area. In order to design the floaters for offshore resource development, it is needed to estimate the seakeeping performance under operating condition and survival conditions and then carry out the structural design based on seakeeping performance results. The environment conditions of 1yr, 10yrs, 100yrs or 1,000 yrs return periods are used based on the metocean data of the installation field to evaluate the seakeeping performance under operating and survival conditions. In general, the wave conditions with the maximum wave heights for each return periods are selected on each wave contour lines in the wave scatter diagram. Then the seakeeping performance is evaluated from the seakeeping model test. However, it was observed that the wave with the pitch forcing period, where the wave length is close to the ship length, is more important than the wave with the maximum wave height after several accidents caused by the green water in Northern North Sea and Norwegian Sea. Therefore, it became a common practice to include not only the wave conditions with maximum wave heights for each return period but also the wave conditions with the pitch forcing period to evaluate the seakeeping performance for offshore development floaters. Ship type floaters such as FPSO are more likely to experience higher impact force due to the large frontal area accompanied by large heave and pitch motions in head sea and bow quartering seas. Recently, it was reported that in an accident in North Sea of UK sector, the damage at the bow of the FPSO is caused due to the steep waves. Afterwards, studies on the steep waves have been made in several institutes such as UK HSE. In this study, the effect of the impact load (so called slapping load) by the steep waves acting on the FPSO bow is investigated throughout the model test. For measurement of the pressure and impact force on the frontal area, a bow-shaped panel was fabricated with the pressure and force sensors, and installed on the bow starboard side of the model FPSO. During the model test campaign, the impact load was investigated using the steep waves with Hw/λ greater than 1/16 in addition to the general wave conditions with maximum wave heights. Consequently, it is confirmed in the model test that the impact loads acting on the FPSO bow are significantly increased with the steep waves (Hw/λ > 1/16) compared to the general wave conditions. Therefore, it is necessary to consider whether the steep waves are additionally included in the wave conditions to estimate the seakeeping performance and how to apply the impact loads acting on the FPSO bow from the steep waves in structure design.

On the Distribution of Wave Impact Loads on Offshore Structures

2017 ◽  
Author(s):  
Thomas B. Johannessen ◽  
Øystein Lande ◽  
Øistein Hagen
Keyword(s):  
Model Test ◽  
Load Distribution ◽  
Impact Load ◽  
Peak Load ◽  
Offshore Structures ◽  
Impact Loads ◽  
Test Results ◽  
Wave Impact ◽  
The Impact ◽  
Crest Height

For offshore structures in harsh environments, horizontal wave impact loads should be taken into account in design. Shafts on GBS structures, and columns on semisubmersibles and TLPs are exposed to impact loads. Furthermore, if the crest height exceeds the available freeboard, the deck may also be exposed to wave impact loads. Horizontal loads due to waves impacting on the structure are difficult to quantify. The loads are highly intermittent, difficult to reproduce in model tests, have a very short duration and can be very large. It is difficult to calculate these loads accurately and the statistical challenges associated with estimating a value with a prescribed annual probability of occurrence are formidable. Although the accurate calculation of crest elevation in front of the structure is a significant challenge, industry has considerable experience in handling this problem and the analysis results are usually in good agreement with model test results. The present paper presents a statistical model for the distribution of horizontal slamming pressures conditional on the incident crest height upwave of the structure. The impact load distribution is found empirically from a large database of model test results where the wave impact load was measured simultaneously at a large number of panels together with the incident crest elevation. The model test was carried out on a circular surface piercing column using long simulations of longcrested, irregular waves with a variety of seastate parameters. By analyzing the physics of the process and using the measured crest elevation and the seastate parameters, the impact load distribution model is made seastate independent. The impact model separates the wave impact problem in three parts: – Given an incident crest in a specified seastate, calculate the probability of the crest giving a wave impact load above a threshold. – Given a wave impact event above a threshold, calculate the distribution of the resulting peak load. – Given a peak load, calculate the distribution of slamming pressures at one spatial location. The development of the statistical model is described and it is shown that the model is appropriate for fixed and floating structures and for wave impact with both columns and the deck box.

Effect of Beam Height on Elastic Impact Load Subjected to Transverse Impact of Bar

2011 ◽  
Vol 462-463 ◽  
pp. 259-264 ◽  
Author(s):  
Jin San Ju ◽  
Min Ding ◽  
Xu Dong Shi ◽  
Song Cen ◽  
Xiu Gen Jiang ◽  
...  
Keyword(s):  
Impact Force ◽  
Impact Load ◽  
Stress Wave Propagation ◽  
Impact Loads ◽  
Transverse Impact ◽  
Load Curve ◽  
Elastic Impact ◽  
Beam Height ◽  
The Impact ◽  
Peak Value

The procedure of beam subjected to transverse impact by bar is simulated using numerical method. The method considers the propagation of the expansion wave and shear wave in beam. The effect of beam height on elastic impact loads with different bar lengths and beam heights are investigated. With condition that the length of beam is longer than or equal to that of bar, the numerical solution shows that: when the bar length is constant, if the length of bar is shorter than the height of beam, the longer the bar, the bigger the peak value of impact force; the impact load curve consists of ascending and descending part basically; When the bar length is longer than or equal to beam height, the peak value of impact force is not related to the bar length and equal to that of bar with the same length as the beam height; the impact load curve is trapezium. The contact time is proportional to bar length and equal to the duration time of stress wave propagation in the bar for once return. If the bar length is constant, when bar length is shorter than beam height, the impact load is not related to beam height; when bar length longer than or equal to beam height, the peak value of impact force increases along with the beam height and approach to that of bar with the same length as the beam height.

scholarly journals Experimental Study on Axial Impact Mitigating Stick-Slip Vibration with a PDC Bit

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Yong Wang ◽  
Hongjian Ni ◽  
Yiliu (Paul) Tu ◽  
Ruihe Wang ◽  
Xueying Wang ◽  
...  
Keyword(s):  
Impact Force ◽  
Impact Load ◽  
Similarity Theory ◽  
Impact Frequency ◽  
Stick Slip ◽  
Axial Impact ◽  
Pdc Bit ◽  
Fluctuation Amplitude ◽  
Rotary Speed ◽  
The Impact

Stick-slip vibration reduces the drilling rate of penetration, causes early wear of bits, and threatens the safety of downhole tools. Therefore, it is necessary to study suppression methods of stick-slip vibration to achieve efficient and safe drilling. Field tests show that the use of downhole axial impactors is helpful to mitigate stick-slip vibration and improve rock-breaking efficiency. However, there are many deficiencies in the study of how axial impact load affects stick-slip vibration of a PDC bit. In this paper, based on the two-degrees-of-freedom spring-mass-damper model and similarity theory, a laboratory experiment device for suppressing stick-slip vibration of a PDC bit under axial impact load has been developed, and systematic experimental research has been carried out. The results show that the axial impact force can suppress the stick-slip vibration by reducing the amplitude of weight on bit and torque fluctuations and by increasing the main frequency of torque. The amplitude of impact force affects the choice of the optimal back-rake angle. The impact frequency is negatively correlated with the fluctuation amplitude of the rotary speed. When the impact frequency is greater than 100 Hz, the fluctuation amplitude of the rotary speed will not decrease.

scholarly journals Effect of Girder Spacing and Depth on the Solitary Wave Impact on Coastal Bridge Deck for Different Airgaps

2019 ◽  
Vol 7 (5) ◽  
pp. 140 ◽  
Author(s):  
Rameeza Moideen ◽  
Manasa Ranjan Behera ◽  
Arun Kamath ◽  
Hans Bihs
Keyword(s):  
Solitary Wave ◽  
Bridge Deck ◽  
Impact Force ◽  
Storm Surges ◽  
Wave Impact ◽  
Wave Condition ◽  
Bridge Damage ◽  
Wave Heights ◽  
The Impact ◽  
Vertical Impact

Coastal bridge damage has become a severe issue of concern in the recent past with the destruction of a considerable number of bridges under the impact of waves during tsunami and storm surges. These events have become more frequent, with waves reaching the bridge deck and causing upliftment and destruction. Past studies have demonstrated the establishment of various theoretical equations which works well for the submerged deck and regular wave types but show much scatter and uncertainty in case of a deck that is above still water level (SWL). The present study aims to generate a solitary wave to represent an extreme wave condition like a tsunami in the numerical wave tank modeled using the open source computational fluid dynamics (CFD) model REEF3D and to study the vertical impact force on the coastal bridge deck. A parametric study is carried out for increasing wave heights, girders spacing and depth for varying airgaps to analyze the effect of these parameters on the peak vertical impact force. It is observed that increasing the girder spacing and girder depth is effective in reducing the peak vertical impact force for the cases considered.

A Case for Avoiding Hydraulic Shock Suppressors (Snubbers) in the Vibratory Environments

2018 ◽  
Author(s):  
Kshitij P. Gawande ◽  
Phillip Wiseman ◽  
Alex Mayes
Keyword(s):  
Dynamic Load ◽  
Impact Load ◽  
Pressure Vessels ◽  
Mechanical Equipment ◽  
Internal Dynamic ◽  
Impact Loads ◽  
Hydraulic Shock ◽  
Dynamic Events ◽  
Piping Systems ◽  
The Impact

Whenever undesirable dynamic events occur within power plant, refinery, or process piping systems, specialty supports and restraints have the task of protecting the mechanical equipment and connecting piping from damaging loads and displacements. The array of components that may be affected include, but are not limited to, piping systems, pumps, valve assemblies, pressure vessels, steam generators, boilers, and heat exchangers. In particular, the dynamic events can be classified into two distinct types that originate from either internal events or external events. The internal dynamic load generating events include plant system start-up and shut-down, pressure surges or impacts from rapid valve closures such as steam and water hammer, boiler detonations, pipe rupture, and operating vibratory displacements that may be either low frequency or high frequency vibrations. The external dynamic load generating events include wind loads, earthquake, airplane impact to supporting structures and buildings, and explosions. Most of the aforementioned dynamic load generating events can be defined quite simply as impact loads, i.e., forces and moments that are applied over very short periods of time, for example, less than one second. While earthquake loads may be applied over a total time period of an hour or so, the peak loads and resulting displacements occur on a more sinusoidal basis of peak-to-peak amplitudes. One of the most common specialty restraint components utilized in the piping industry to absorb and transfer the dynamic load resulting from impact events is the hydraulic shock suppressor, otherwise known as the snubber. The snubber is a formidable solution to protecting plant piping systems and equipment from impact loading while not restricting the thermal displacements during routine operations. In the dynamic events that may be characterized by an impact type loading, snubbers provide an instantaneous, practically rigid, axial connection between the piping or other component to be secured and the surrounding structure whether it be concrete or steel (for example). In this way, the kinetic energy can be transmitted and harmlessly dissipated. In the vibratory environment, however, neither the impact load scenario nor the rapid translations are imposed upon snubbers, thereby presenting the competing intended application of the snubber to protect against impact loads versus, in many cases, the improper selection of the snubber to dampen vibratory (other than seismic) loads. The details of the hydraulic shock suppressor design are reviewed and discussed to exemplify why a case can and should be made against the use of snubbers in piping systems within an operating vibratory environment.

Finite Element Analysis of a Single-Layer Reticulated Dome under Impact Loading

2010 ◽  
Vol 163-167 ◽  
pp. 327-331 ◽  
Author(s):  
Liang Zheng ◽  
Zhi Hua Chen
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Impact Force ◽  
Impact Load ◽  
Residual Deformation ◽  
Time History ◽  
Single Layer ◽  
Element Analysis ◽  
Deformation Stage ◽  
The Impact

Finite element model of both the single-layer Schwedler reticulated dome with the span of 50m and a Cuboid impactor were developed, incorporating ANSYS/LS-DYNA. PLASTIC_KINEMATIC (MAT_003) material model which takes stain rate into account was used to simulate steel under impact load. The automatic point to surface contact (NODES TO SURFACE) was applied between the dome and impact block. Three stages of time history curve of the impact force on the apex of the single-layer Scheduler reticulated dome including the impact stage, stable stalemate stage, the decaying stage were generalized according to its dynamic response. It must be pointed out that the peak of the impact force of the single-layer reticulated dome increase with the increase of the weight and the velocity of the impact block, but the change of the velocity of the impact block is more sensitive than the change of weight of the impact block for the effect of the peak of the impact force, and a platform value of the impact force of the single-layer reticulated dome change near a certain value, and the duration time of the impact gradually increase. Then four stages of time history curve of the impact displacement were proposed according to the dynamic response of impact on the apex of the single-layer reticulated dome based on numerical analysis. Four stages include in elastic deformation stage, plastic deformation stage, elastic rebound stage, free vibration stage in the position of the residual deformation.

scholarly journals Failure Characteristics of Joint Bolts in Shield Tunnels Subjected to Impact Loads from a Derailed Train

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Qixiang Yan ◽  
Zhixin Deng ◽  
Yanyang Zhang ◽  
Wenbo Yang
Keyword(s):  
Impact Load ◽  
Numerical Study ◽  
Design Method ◽  
Shield Tunnel ◽  
Failure Behavior ◽  
Impact Loads ◽  
Fe Model ◽  
Fe Modelling ◽  
Bolt Failure ◽  
The Impact

Impact loads generated by derailed trains can be extremely high, especially in the case of heavy trains running at high speeds, which usually cause significant safety issues to the rail infrastructures. In shield tunnels, such impact loads may not only cause the damage and deformation of concrete segments, but also lead to the failure of segmental joint bolts. This paper presents a numerical study on the failure behavior of segmental joint bolts in the shield tunnel under impact loading resulting from train derailments. A three-dimensional (3D) numerical model of a shield tunnel based on the finite element (FE) modelling strategy was established, in which the structural behavior of the segmental joint surfaces and the mechanical behavior of the segmental joint bolts were determined. The numerical results show that the occurrence of bolt failure starts at the joints near the impacted segment and develops along the travel direction of train. An extensive parametric study was subsequently performed and the influences of the bolt failure on the dynamic response of the segment were investigated. In particular, the proposed FE model and the analytical results will be used for optimizing the design method of the shield tunnel in preventing the failure of the joint bolts due to the impact load from a derailed HST.

Fabrication of Hydraulic Bumper for Anti-Collision in a Vehicle

2015 ◽  
Vol 766-767 ◽  
pp. 499-504 ◽  
Author(s):  
M. Anish ◽  
R. Thamaraikannan ◽  
B. Kanimozhi ◽  
Ham G. Varghese ◽  
Shem G. Varghese
Keyword(s):  
System Design ◽  
Automotive Industry ◽  
Production Cost ◽  
Impact Force ◽  
Impact Load ◽  
Suitable Material ◽  
Fiber Plastic ◽  
The Cost ◽  
The Impact ◽  
Bumper System

Improvement of bumper system is crucial in the automotive industry. The main objectives are to increase the performance of the bumper and also to find a solution to reduce the cost of the bumper thereby facilitating the reduction of production cost. The cost of bumper is high owing to the amount of material used and various processes involved .The new design considers on reducing the amount of material use and adding improved hydraulics instead of normal bumper to give cushioning effect and also assures safety in low speed collision. The new design also improves the ability to absorb more impact load and increase the protection of the front car component. The methodology employed was the study of the front bumper system, design and fabrication. The suitable material that can be used as the bumper in terms of economical but still maintaining the toughness is Plastic-Polycarbonate (Molded) which is not expensive compared to the best material from the analysis of E-Glass Fiber, Plastic-Nylon Type 6/6 and Plastic ABS (Molded). The suitable material to be used for making beam is AISI E52100 Steel. Rearrangement of the mounting positions gives a different effect on the ability to withstand the impact force.

Rigid-plastic analysis of floating ice sheets under impact loads

1981 ◽  
Vol 8 (4) ◽  
pp. 409-415
Author(s):  
John B. Kennedy ◽  
K. J. Iyengar
Keyword(s):  
Impact Load ◽  
Design Method ◽  
Yield Criterion ◽  
Ice Sheets ◽  
Contact Radius ◽  
Impact Loads ◽  
Rigid Plastic ◽  
Deformation Response ◽  
Safe Thickness ◽  
The Impact

The deformation response of floating ice sheets under high intensity, short duration loads is examined. Using a rigid-plastic theory, together with a Tresca yield criterion, expressions are derived for the total time of response and the final deformed configuration of floating ice sheets. The influence of the magnitude of the impact load and the load-contact radius on the various design quantities such as deflection profile and stress distribution is discussed. Based on the results derived, a design method is presented to find the safe thickness of a floating ice sheet to sustain a given impact load. The method is illustrated with a numerical example.

scholarly journals Numerical Simulation of Modified Rubberized Concrete Block Under Impact Loads

2021 ◽  
Vol 1200 (1) ◽  
pp. 012022
Author(s):  
T Y Pei ◽  
S N Mokhatar ◽  
N A N A Mutalib ◽  
S J S Hakim
Keyword(s):  
Energy Absorption ◽  
Impact Load ◽  
Concrete Strength ◽  
Constitutive Models ◽  
Numerical Procedure ◽  
Concrete Block ◽  
Crumb Rubber ◽  
Impact Loads ◽  
Rubberized Concrete ◽  
The Impact

Abstract Rubberized concrete was innovated by many researchers to enhance energy absorption under impact load and by reusing scrap tires. Thus, this research was aims to develop the numerical procedure using the Finite Element Method (FEM) to simulate modified rubberized concrete under impact loads and predict its energy absorption under different impact loads. Three existing constitutive models: Concrete Damage Plasticity (CDP), Drucker-Prager (DP), and Modified Drucker-Prager Cap (MDPC) available in ABAQUS software were used to replicate the rubberized concrete with 10% of Rice Hush Ash (RHA) as cement substitution and different percentages (0%, 5%, 10%, 15%, and 20%) of crumb rubber as sand replacement. All three models produced successful FEM results with reasonable modelling assumption, and the CDP model was more effective in simulating rubberized concrete under impact to predict energy absorption than DP and MDPC models. Further, it was concluded that crumb rubber could enhance the energy absorption of concrete. Generally, the energy absorption of the concrete increased as the crumb rubber increase. However, the strength decreased as the crumb rubber increased, but 10% of RHA in concrete mix can maintain the concrete strength. Overall, this study reveals that FEM incorporated with the CDP model is able to predict the impact response of modified crumb rubber as an application of concrete road barrier.

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