Abstract

Slamming is a very significant phenomenon that occurs in marine structures operating under extreme conditions. Slamming significantly reduces the design life of floating offshore wind turbines, as well as marine structures, and causes structural damage. Thus, the slamming load should be considered sufficiently during the design phase of the structure, and the results of experiments of good quality should be incorporated. The phenomenon of slamming should be analyzed using peak pressure, width, duration, and dynamic loads that depend on the design and natural frequency of the structure. In the case of a slamming experiment, the deadrise angle shows the greatest pressure between 3° to 10°. In this study, pressure values were compared using a model with a deadrise angle of 10° and a cylinder model most commonly used for the fabrication and installation of offshore structures. The peak pressure of the cylindrical model is greater than those of the flat model and the wedge model with a 10° deadrise angle. Pressure and strain were measured using free drops from heights of 1.0 and 1.7 m from the water surface, and the elastic effects were studied accordingly. Also, the peak pressure due to a slamming impact occurs several times depending on the natural frequency of the structure. In order to understand the behavior of the structure against the elastic effect, the second peak in the experimental results was theoretically and experimentally analyzed. The second pressure peak is greater than the first pressure peak due to the elastic behavior effects based on the natural frequency of models used in the slamming test. Also, a single slamming results in several peak pressures and it greatly deteriorates the fatigue strength. Experiments and simulations were carried out to derive the effects of repeated slamming loads on the structure. In the structural design considering the slamming loads, information on the elastic effect of the structure and accumulated loads is very important. This can be an important variable in the design of the floater and can play an important role in assessing the impact on the floater. These results raise questions as to the extent that slamming pressures are replaced with equivalent hydrostatic pressures in most design rules of the recognized certification society.

Highlights

  • Offshore structures suffer from various types of impulsive pressure loading, such as slamming, sloshing, and green water

  • The second pressure peak is greater than the first pressure peak due to the elastic behavior effects based on the natural frequency of models used in the slamming test

  • Based on the peak pressure, the slamming load is calculated as the equivalent design pressure

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Summary

Introduction

Offshore structures suffer from various types of impulsive pressure loading, such as slamming, sloshing, and green water. Severe pressure due to slamming can be exerted on floating offshore wind turbines and could exacerbate their structural damage and deteriorate their strength. When the of non-dimensional slamming pressure is greater than 1, the behavioral characteristics of duration the structure are determined by the peak pressure. According to recently published papers and case studies, design life in the context of structural damage model during experiments under irregular wave conditions. In the of floating production, storage wind turbines experience bottom slamming, wave run-up slamming, and horizontal slamming Under these conditions, certain combinations of slamming loads can be harmful. In the case of floating production, storage and offloading, all employees are evacuated owing to the damage caused by slamming loads [11].

Experiment Set-Up
Experimental Test Loop
Locations of the Sensors
Pressure Sensors
Strain Gauges
Data Acquisition System with Calibrations
Dimensions of Test Models
Sectional geometry of the cylindrical model with a deadrise angle of 10
Tensile Test
Experimental Results for Model with Deadrise Angle of 10 and Cylindrical
History of pressure and withdeadrise deadrise angle of 10
Methodology
Comparison of Simulation and Experimental Results for the the Accumulative
Results and Discussion
Full Text
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