Wave Kinematics Models For Calculation Of Wave Loads On Truss Structures

1994 ◽  
Author(s):  
O.T. Gudmestad ◽  
Daniel Karunakaran
Keyword(s):  
Truss Structures ◽  
Wave Loads ◽  
Wave Kinematics

Second-Order Wave Loads on a LNG Carrier in Multi-Directional Waves

2008 ◽  
Author(s):  
Mathieu Renaud ◽  
Fla´via Rezende ◽  
Olaf Waals ◽  
Xiao-Bo Chen ◽  
Radboud van Dijk
Keyword(s):  
Low Frequency ◽  
Model Tests ◽  
Second Order ◽  
Wave Loads ◽  
Wave Kinematics ◽  
Directional Waves ◽  
Slow Drift ◽  
Wave Directionality ◽  
Offshore Industry ◽  
Cross Waves

Due to the installation of LNG terminals moored in proximity to the coast, the wave kinematics in shallow water and the consequence on the behavior of those terminals have recently became a major concern of the offshore industry. One key issue is the accurate simulation of the low-frequency motions of LNG carriers, specially the surge, for which the vessel presents low damping, in order to perform the design of the mooring system. The present paper focuses on the effect of wave directionality on second-order slow-drift loads and the related response of the vessel. The paper describes results of model tests in regular cross waves — monochromatic but coming from two directions separated by 90 degrees, as well as bichromatic cross waves. The new “middle field” formulation extended to the case of cross waves, is used to compute the wave drift loads and low-frequency Quadratic Transfer Function (QTF). The results are compared with those from the model tests.

Second-Order Random Wave Kinematics and Resulting Loads on a Bottom-Fixed Slender Monopile

2013 ◽  
Author(s):  
Carl Trygve Stansberg ◽  
Andreas Amundsen ◽  
Sebastien Fouques ◽  
Ole David Økland
Keyword(s):  
Second Order ◽  
Offshore Wind ◽  
Random Wave ◽  
Wave Loads ◽  
Random Waves ◽  
Shear Forces ◽  
Traditional Use ◽  
Wave Kinematics ◽  
Drag Forces ◽  
Particle Velocities

The importance of including second-order nonlinear random wave kinematics in the numerical prediction of drag-induced shear forces and moments, at various levels on a bottom-fixed slender monopile in 40m water depth, is investigated. A vertical circular cylinder of diameter 0.5m is considered, representing typical dimensions of members in jacket type foundations of offshore wind turbines. The focus is here on the wave loads only, and wind and a propeller are therefore not included in this study. In particular, the main focus is on the effects from second-order random wave kinematics on the structural quasi-static time-varying loads due to drag forces in heavy storm wave conditions. Comparisons are made to the traditional use of Airy waves with various ways of stretching. An in-house numerical FEM code developed for structural analysis, NIRWANA, is used for this study. Thus one purpose of the present work is also to verify the implementation of the second-order random waves in the code. The results show significant effects, especially in the wave zone. Extreme crests are around 15%–20% increased, free-surface extreme particle velocities increase by around 30%–40%, while the velocities at levels below MWL are, on the other hand, somewhat reduced. The resulting peak shear forces, and in particular the moments, are thereby increased by typically 50%–100% in the upper parts of the column. At the base the peak shear forces are comparable to the traditional methods, while moments are still somewhat higher. Another effect is the generation of more high-frequency load contributions, which may be important to address further with respect to natural frequencies of such towers.

scholarly journals AN EXPERIMENTAL STUDY OF A SOLITARY WAVE IMPACTING A VERTICAL SLENDER CYLINDER

2020 ◽  
pp. 8
Author(s):  
Bing Tai ◽  
Yuxiang Ma ◽  
Guohai Dong ◽  
Marc Perlin
Keyword(s):  
Solitary Wave ◽  
Structural Response ◽  
Equation Of Motion ◽  
Temporal Variations ◽  
Wave Forces ◽  
Wave Loads ◽  
Coastal Structures ◽  
High Wave ◽  
Wave Kinematics ◽  
Structural Responses

Solitary waves can evolve into plunging breakers during shoaling, inducing high wave loads on coastal structures. Meanwhile, plunging waves propagate with rapid spatial-temporal variations both in wave geometry and wave kinematics, causing varying forces on structures for different breaking stages (Chan et al., 1995). Although there have been numerous experiments for wave forces on cylinders, to our knowledge no experiments have studied the forces at different breaking stages of a plunging solitary wave. Thus, in our study, experiments are conducted to investigate the force due to a plunging solitary wave impacting a circular cylinder as a function of the wave's phase. Due to these forces, as expected structural responses are induced (Paulsen et al., 2019); to eliminate the effect of the structural response, the equation of motion is proposed to facilitate extracting only the isolated hydrodynamic forces.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/P07Cdlnxe7s

Gaussian Analysis of an Irregular Wave Impact on Deck

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Ravikiran S. Kota ◽  
Torgeir Moan
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Joint Probability ◽  
Vertical Force ◽  
Wave Loads ◽  
Wave Impact ◽  
Irregular Wave ◽  
Wave Kinematics ◽  
Wetting Process

Level-crossing analysis of long-crested, Gaussian waves in space and time are studied in the context of wave loads on a fixed, horizontal deck-box above mean waterline. Vertical wave loads on decks due to insufficient airgap are a major concern for many in-service platforms. Reliable estimation of magnitude and duration of these loads is important in assessing structural and global response of an offshore platform. In the case of an irregular wave-impact on a flat deck of dimensions comparable to mean wavelength of the incident waves, both temporal and spatial variability of wave-kinematics need to be considered during the deck-wetting process. In the present study, we have used a multidimensional Gaussian formulation of incident wave-kinematics to derive a joint probability density function of deck-wetting (or exceedance) duration and its spatial extent. We have also derived a probability density function for initial slam force on deck. A numerical scheme for simulating wave-impact events on a two-dimensional deck is discussed, results from which are compared against corresponding analytical estimates. Vertical force on deck was estimated using the momentum method, which includes a von Kármán slamming model applied over the wetted-length determined from an undisturbed wave profile.

Various methods of simulating wave kinematics on the structural members of 100-year responses

2017 ◽  
Vol 11 (4) ◽  
pp. 3256-3273
Author(s):  
M.K. Abu Husain ◽  
◽  
N.I. Mohd Zaki ◽  
G. Najafian ◽  
◽  
...  
Keyword(s):  
Structural Members ◽  
Wave Kinematics

The Formability and Elongation of Aluminum Alloys AA5083 and AA3003 for Micro-Truss Sandwiches Manufacturing

2020 ◽  
Vol 38 (9A) ◽  
pp. 1396-1405
Author(s):  
Arwa F. Tawfeeq ◽  
Matthew R. Barnett
Keyword(s):  
Aluminum Alloy ◽  
Strain Rate ◽  
Cost Effective ◽  
Tensile Tests ◽  
Truss Structures ◽  
High Quality ◽  
Trade Off ◽  
Clad Layer ◽  
Higher Temperature ◽  
Different Shapes

The development in the manufacturing of micro-truss structures has demonstrated the effectiveness of brazing for assembling these sandwiches, which opens new opportunities for cost-effective and high-quality truss manufacturing. An evolving idea in micro-truss manufacturing is the possibility of forming these structures in different shapes with the aid of elevated temperature. This work investigates the formability and elongation of aluminum alloy sheets typically used for micro-truss manufacturing, namely AA5083 and AA3003. Tensile tests were performed at a temperature in the range of 25-500 ○C and strain rate in the range of 2x10-4 -10-2 s-1. The results showed that the clad layer in AA3003 exhibited an insignificant effect on the formability and elongation of AA3003. The formability of the two alloys was improved significantly with values of m as high as 0.4 and 0.13 for AA5083 and AA3003 at 500 °C. While the elongation of both AA5083 and AA3003 was improved at a higher temperature, the elongation of AA5083 was inversely related to strain rate. It was concluded that the higher the temperature is the better the formability and elongation of the two alloys but at the expense of work hardening. This suggests a trade-off situation between formability and strength. 

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