Viscous Damping Modelling of Floating Bridge Pontoons With Heaving Skirt and its Impact on Bridge Girder Bending Moments

2017 ◽  
Author(s):  
Xu Xiang ◽  
Erik Svangstu ◽  
Øyvind Nedrebø ◽  
Bernt Jakobsen ◽  
Mathias Egeland Eidem ◽  
...  
Keyword(s):  
Relevant Literature ◽  
Experimental Studies ◽  
Iteration Process ◽  
Damping Coefficient ◽  
Accurate Estimation ◽  
Bending Moments ◽  
Bottom Part ◽  
Floating Bridge ◽  
Damping Effects ◽  
Offshore Industry

The current floating bridge concepts of Norwegian Public Roads Administration (Statens vegvesen, NPRA) use a flange shape part at the bottom part of the pontoons. The flange is in principle similar to the damping plates used in the offshore industry for SPAR type of structures. The project group initiated the flange part based on the requirement of extra added mass for tuning the bridge system Eigen-modes. Thus, the important modes can be shifted out of the main wave energy zone. The current study will focus on the damping effects of such structure. The damping effects on weak axis bending moment prediction is studied. The modelling of such damping is first proposed according to relevant literature based on both numerical and experimental studies. Since the reference studies were mainly focused on cylindrical structures, it is difficult to obtain an accurate estimation of the damping coefficient for the current bridge pontoon design, which contains a rectangular part between two half-cylindrical parts. In addition, the estimation of pontoon motions needs the input of damping coefficient, which means that the evaluation of damping coefficient is an iteration process. In order to include the uncertainties, a conservative value was adopted to represent the damping effect. The comparison of accounting for the damping effects or not has been given for all the bridge pontoons. The results show that the damping effects are important at the peaks of the responses; in addition, the reduction of the predicted maximum bending moments can be expected around 10–15 percent along different positions of the bridge. However, a further investigation also shows that viscous excitation would increase the bending moments slightly. The comparison also indicates the value of further investigating the effects by CFD or model test methods.

scholarly journals Collective Losses of Low Power Cage Induction Motors—A New Approach

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1749
Author(s):  
Elzbieta Szychta ◽  
Leszek Szychta
Keyword(s):  
Control System ◽  
Experimental Studies ◽  
Complex Problem ◽  
Accurate Estimation ◽  
New Approach ◽  
Water Pumping ◽  
Efficiency Control ◽  
Interacting Systems ◽  
Cage Induction Motor ◽  
Selection Of

Energy efficiency of systems of water pumping is a complex problem since efficiency of two distinct interacting systems needs to be combined: water and power supply. This paper introduces a non-intrusive method of calculating the so-called “collective losses” of a cage induction motor. The term “collective losses”, which the authors define, allows for accurate estimation of motor efficiency. Control system of a pump determines operating point of a pumping station, and thus its efficiency. General estimated performance characteristics of a motor, components of a control system, are assumed to serve selection of a range of pumping speed variations. Rotational speed has a direct effect on motor load torque, pump power and head, and thus on motor performance. Hellwig’s statistical method was used to specify characteristics of estimated collective losses on the basis of experimental studies of 21 motors rated at up to 2.2 kW. The results of simulations and experiments are used to verify validity and efficiency of the suggested method. The method is non-intrusive, simple to use, and requires minimum data.

Experiences From Handling Mooring Line Polyester Fibre Ropes During Installation and Retrieval

2002 ◽  
Author(s):  
Lars Hilmersen
Keyword(s):  
Polyester Fibre ◽  
Mooring Line ◽  
Test Program ◽  
Mooring Lines ◽  
Bottom Part ◽  
Load Bearing ◽  
Hands On ◽  
Large Fibre ◽  
Offshore Industry ◽  
Water Depths

The use of fibre ropes made by synthetic fibres have been used more frequent as the offshore industry is moving towards larger water depths. An important aspect is the effect of handling on the large, but delicate, ropes during installation offshore using tools and equipment that easily can destroy the load bearing capacities of the ropes. In order to get hands on experience in the field large polyester ropes have been used as inserts in catenary mooring lines for Mobile Offshore Units (MODU) working on depths ranging from 80 to 350 meters. The ropes have been integrated in the catenary chain mooring lines both in the suspended part and in the bottom part of the mooring leg thus having been exposed to seafloor clay. Subsea buoy have been attached to the ropes using smaller size fibre ropes in order to lift the mooring lines from the seafloor. The paper will detail how the large fibre ropes have been mobilised and demobilised repeatedly from/to storage drums to/from the installation vessel winch drum. During installation and retrieval the fibre ropes have been installed from the vessels winch drum using regular anchor handling equipment and vessels. When the MODU has been moved between locations some ropes have been retrieved to the vessels winch drums while the others have been used to tow and to keep the units station. Samples of the used ropes are taken and is subjected to a test program in the laboratory in order to document the effect of extensive use and handling and exposure to seabed clay.

Experimental Study on Water Damping Effects of Hybrid Floating Structure

2013 ◽  
Author(s):  
Youn-Ju Jeong ◽  
Young-Jun You ◽  
Du-Ho Lee ◽  
Min-Su Park
Keyword(s):  
Natural Frequency ◽  
Hybrid Model ◽  
Damping Ratio ◽  
Experimental Studies ◽  
Oscillation Period ◽  
Floating Body ◽  
Small Scale ◽  
Floating Structure ◽  
Damped System ◽  
Damping Effects

In this study, in order to evaluate water damping effects of hybrid pontoon system with cylinders, experimental studies were carried out. At first, in order to evaluate oscillatory motions, three small-scale models of hybrid, tapered, and pontoon were fabricated and tested under the still-water condition. Four acceleration gauges were attached on the top edges and acceleration of top edge were measured during the oscillation. Then, oscillatory motions of oscillation period and stabilizing time to steady-state were analyzed. Finally, based on the oscillatory motions, damping properties of the logarithmic decrement, damping ratio, and natural frequency of damped system were calculated and compared with each other. As the results of this study, it was found that hybrid model presented about 3.67 times higher decay rate of amplitude of the oscillatory motion than the pontoon model. Also, hybrid model presented about 3.67 times higher damping ratio than the pontoon model. Whereas the natural frequency of the pontoon and tapered model were nearly same with the natural frequency of undamped system, that of the hybrid model presented some difference with the that of the undamped system. In addition, periods of floating body at the wet mode presented about 1.5∼3.0 times longer periods than the dry mode, and it was expected that there was not possibility for the resonance. Therefore, it was expected that the hybrid model of this study should contribute to improve serviceability and safety of offshore floating structures as decreasing oscillatory motions.

scholarly journals Model study of the influence of multi-joint muscles on the frequency characteristics of the human body

2020 ◽  
Vol 16 (3) ◽  
pp. 267-276
Author(s):  
Vladimir P. Tregubov ◽  
◽  
Nadezhda K. Egorova ◽  
Keyword(s):  
Lumbar Spine ◽  
Degrees Of Freedom ◽  
Experimental Studies ◽  
Biological Tissues ◽  
Chain Structure ◽  
Vertical Vibration ◽  
Damping Coefficient ◽  
Force Characteristic ◽  
Integer Number ◽  
Mass System

It is noted that the Kelvin—Voigt model is unsuitable for describing some polymers and biological tissues. In these cases, a three-component combination of elements, which consists of a spring and damper, connected in parallel and a spring sequentially attached to them, is used. The force characteristic of such a combination includes not only the strain, strain rate, and force, but also the rate of force change. Examples of such systems are the blood vessel wall and the intervertebral disc, which have been given special attention. Since the motion of such systems is described by an ordinary third-order differential equation, they are classified as systems with a non-integer number of degrees of freedom. For a single-mass oscillating system with one and a half degrees of freedom, a transfer function was constructed using the Laplace transform. In addition, the amplitude-frequency response (AFR) was also constructed. Analysis of this characteristic showed that increasing the damping coefficient from zero to infinity first leads to a decrease in its maximum to a certain non-zero value, and then to an increase and reaching infinity with an infinite value of the damping coefficient. The same feature is demonstrated on a two-mass system of chain structure, each link of which has one and a half degrees of freedom. A sequential combination of seven such links was used to model the lumbar spine in the structure of a General body model of a sitting person subject to vertical vibration. Multi-link elastic-viscous joints were used to model the multi-articular muscles of the lumbar spine. Additional experimental studies are needed to determine the numerical values of the parameters of the proposed model.

Hydroelastic Analysis and Validation of an End-Anchored Floating Bridge Under Wave and Current Loads

2019 ◽  
Author(s):  
Xu Xiang ◽  
Arne Løken
Keyword(s):  
Global Analysis ◽  
Model Tests ◽  
Analysis Model ◽  
Global Dynamic ◽  
Analysis Tools ◽  
Hydroelastic Analysis ◽  
Floating Bridge ◽  
Offshore Industry ◽  
Traditional Structures ◽  
Future Work

Abstract Analysis tools used by the offshore industry are applied for prediction of global dynamic behaviour of the extreme floating bridge concepts being evaluated by the Norwegian Public Roads Administration (NPRA). Validation and code-code comparison of these analysis tools are of significant importance when they are applied to such new and non-traditional structures. The current paper focus on validation between numerical modelling and model tests. An end-anchored floating bridge of around 850m length is studied. A hydro-elastic global analysis model was created by considering the bridge as large radiation/diffracting floaters connected by elastic beams. The analysis has been done both in frequency and time domain, by including the hydrodynamic interaction between the pontoons or not. A systematic check of different parameters that may have impact on the analysis was carried out. The numerical results have been compared with the model tests carried out in MARINTEK (1990). The work provides validation of the current analysis tools and guidelines for future work.

scholarly journals Prospects of Antiangiogenic Therapy for Portal Hypertension in Liver Cirrhosis

2018 ◽  
Vol 28 (5) ◽  
pp. 35-45
Author(s):  
D. V. Garbuzenko
Keyword(s):  
Liver Cirrhosis ◽  
Portal Hypertension ◽  
Kinase Inhibitors ◽  
Antiangiogenic Therapy ◽  
Relevant Literature ◽  
Experimental Studies ◽  
Reference List ◽  
Action Mechanisms ◽  
Key Points

Aim.This paper is aimed at reviewing existing literature that investigates the role of angiogenesis in portal hypertension pathogenesis in liver cirrhosis and the possibilities of its antiangiogenic therapy, along with the description of angiogenesis inhibiting drugs and their action mechanisms.Key points. A relevant literature and reference list search was performed using PubMed and RSCI and Google Scholar, and covered the 2000–2017 period. The following keywords were used: liver cirrhosis, portal hypertension, pathogenesis, angiogenesis, antiangiogenic therapy. The inclusion criteria were limited to the antiangiogenic therapy of portal hypertension. Angiogenesis is shown to play an important role in the pathogenesis of liver cirrhosis. Angiogenesis is the basis for the development of associated portal hypertension that causes its characteristic complications. The experimental studies reviewed in this paper investigate the action mechanism of angiogenesis inhibiting drugs and their effect on portal hypertension. It is shown that, so far, only tyrosine kinase inhibitors have been tested in patients with liver cirrhosis as an antiangiogenic therapy for portal hypertension.Conclusion.Antiangiogenic therapy, selectively directed at unusually growing newly-formed vessels, can be a pathogenetically justified method for treating portal hypertension in liver cirrhosis on its subclinical stage. 

scholarly journals RESEARCH OF THE INFLUENCE OF LONGITUDINAL COMPRESSION ON THE STRENGTH OF THE WALL OF TWO-TURNED REINFORCED CONCRETE ELEMENTS WITH A CHARACTERISTIC EPURA BENDING MOMENTS IN THE AREA OF ACTION OF LATERAL FORCES

2021 ◽  
Vol 3 (72) ◽  
pp. 34-37
Author(s):  
A. Abdullaev .
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Compressive Force ◽  
Reinforced Concrete Beams ◽  
Bending Moments ◽  
Shear Forces ◽  
Longitudinal Compression ◽  
Lateral Forces ◽  
Concrete Elements

Experimental studies have been carried out to study the effect of longitudinal compression on the strength of the wall of I-beams of reinforced concrete beams.It has been established that with the central application of a longitudinal compressive force, the strength of the wall of I-beams of reinforced concrete beams with an alternating diagram of bending moments in the zone of action of transverse forces practically depends little on the degree of longitudinal compression.A comparative analysis of the results obtained with the results of similar experimental studies carried out on I-beam reinforced concrete beams with an unambiguous diagram of bending moments in the zone of action of shear forces is carried out.

CFD Simulation of Roll Damping Characteristics of a Ship Mid-Section With Bilge Keel

2016 ◽  
Author(s):  
Mohsin A. R. Irkal ◽  
S. Nallayarasu ◽  
S. K. Bhattacharyya
Keyword(s):  
Fluid Dynamics ◽  
Cfd Simulation ◽  
Experimental Studies ◽  
Ship Hull ◽  
Estimation Methods ◽  
Accurate Estimation ◽  
Roll Motion ◽  
Roll Damping ◽  
Damping Characteristics ◽  
Bilge Keel

The prediction of nonlinear roll motion of ships depends highly on the accurate estimation of roll damping. The nonlinear nature of roll damping arises from the viscous flow and the associated phenomenon of flow separation around the ship hull. Roll damping changes noticeably with a slight change in the ship hull geometry and appendages. The estimation methods employed in industry are highly empirical in nature. These empirical methods were derived from combinations of model tests conducted in wave flumes and basins, and some selected formulae used in fluid dynamics. These methods have limitations and the roll damping prediction show large variation with change in the ship parameters. The advances made in Computational Fluid Dynamics (CFD) in recent times, and validation of the CFD results using experimental studies, can help in predicting roll motion and damping more accurately. The present work uses CFD as a tool to estimate roll damping of a ship mid-section with bilge keel with validation using published experimental results.

Experimental Studies on the Bonding Failure between CFRP and Concrete in RC Two-Way Slabs Strengthened with CFRP Strips

2012 ◽  
Vol 166-169 ◽  
pp. 1530-1533
Author(s):  
Wen Bin Sun ◽  
Jing Zhao ◽  
Yang Jiang
Keyword(s):  
Failure Modes ◽  
Experimental Studies ◽  
Theoretical Studies ◽  
High Shear ◽  
Bending Moments ◽  
Shear Forces ◽  
Bonding Failure ◽  
Externally Bonded ◽  
Cfrp Strip ◽  
Experimental And Theoretical Studies

It is well known that the bonding failure between concrete and externally bonded CFRP strips sets in where high shear forces and high bending moments occur. Despite this knowledge, experimental and theoretical studies had been exclusively focused on the bonding failure modes at the end of the CFRP-strip. This paper deals with strengthening of RC two-way slabs with CFRP strips bonded to the tensile face. It focuses on the bonding failure by dealing with an experimental study. The CFRP-strips strengthened slab test presents a failure mode with debonding of the external CFRP strips from the slab.

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