Abstract
An attempt has been made to predict the ice rubble field load on Norströmsgrund lighthouse by using Cohesive Element (CE) formulation. Two sub-load events were selected to validate the numerical and material model used in simulation of interaction of the ice rubble field and lighthouse. A literature review of simulation of rubble field structure interaction methods is also included in order to illustrate the knowledge gaps and highlight shortcomings of existing techniques. A description of chosen ice rubble field load events and signal post processing is added. A linear Mohr-Coulomb material model was used for the bulk element. For the cohesive element formulation, a material model was chosen which is based on three irreversible mixed-mode interaction with an arbitrary normalized traction-separation law governed by a load curve. The elastic modulus and fracture toughness for the ice rubble field were scaled using the ice rubble field porosity. A parametric study was conducted, and effects were documented. The numerical model predicted similar values for maximum total force, but average and standard deviation values of total force were higher than measured. The observed load drops in measured force time histories were reproduced with reasonable accuracy in simulated force time histories.
Highlights
The term ice rubble field can be used as generalised term for ice ridge fields where vast area of sea covered with ice blocks packed together
Numerical simulation methods have an advantage over laboratory and in-situ testing of ice rubble as they offer a greater number of parameters to be tested under controlled conditions
Full-scale measurements of the ice loads at Norstromsgrund light house were obtained in two measurement campaigns, “Validation on Low Level Ice Forces on Coastal Structures” (LOLEIF) and “Measure ments of Structure in Ice” (STRICE) from 1999 to 2003
Summary
The term ice rubble field can be used as generalised term for ice ridge fields where vast area of sea covered with ice blocks packed together. The combined FEM-DEM approach was proposed to eliminate the rigidity issue of bulk element in the simulation of ice rubble structure in teractions, see Polojarvi and Tuhkuri (2009), Paavilainen et al (2011) and Polojarvi and Tuhkuri (2013) In their approach, DEM was used to model the contact interactions and finite elements were used as constitutive relation which dictates the behaviour and the ice fracture. A numerical model is used to simulate the ice rubble field structure interaction process, using Cohesive Element Method (CEM). Ocean Engineering 223 (2021) 108638 special purpose MATLAB (2019) script was written to post process the load event acquired/measured data, as well to create numerical model and post-process the simulation results This numerical model is used in two separate parametric studies to investigate the effect of influential parameters such as cohesive strength, angle of internal friction, fracture toughness and exponential decay coefficient. The numerical results are compared with the load event time series and the conclusions are drawn based on merit and drawbacks of the material model and numerical method
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