Numerical Model Study of Prototype Drop Tests on Cube and Cubipod® Concrete Armor Units Using the Combined Finite–Discrete Element Method

Giulio Scaravaglione,John-Paul Latham,Jiansheng Xiang

doi:10.3390/jmse9050460

Abstract

This paper aims to evaluate the structural strength of unreinforced concrete armor units (CAU), named Cubipod®, used on rubble-mound breakwaters and coastal structures, through a numerical methodology using the combined finite–discrete element method (FDEM). A numerical modeling methodology is developed to reproduce the results of an experimental examination published by Medina et al. (2011) of a free-fall drop test performed on a 15 t conventional Cubic block and a 16 t Cubipod® unit. The field results of the Cube drop tests were used to calibrate the model. The numerically simulated response to the Cubipod® test is then discussed in the context of a validation study. The calibration process and validation study provide insights into the sensitivity of breakage to tensile strength and collision angle, as well as a better understanding of the crushing and cracking damage of this unit under drop test impact conditions.

Highlights

In the last few decades, the coastal engineering profession has promoted solutions for the protection of the areas exposed to severe wave attack through the use of concrete armor units (CAUs) in the armor layers of rubble-mound breakwaters
It is the hydraulic stability, as traditionally predicted with use of a KD or similar stability factor, and the structural integrity that should be taken into consideration for CAU selection [8], because no matter how high the packing density or the placing tolerances achieved, the possibility of a significant number of rocking units under storm conditions cannot be discounted
A new three-dimensional fracture model in the context of the finite–discrete element method (FDEM) method was applied to the investigation of the structural integrity of concrete armor units under dynamic loading conditions

Summary

Introduction

In the last few decades, the coastal engineering profession has promoted solutions for the protection of the areas exposed to severe wave attack through the use of concrete armor units (CAUs) in the armor layers of rubble-mound breakwaters. A recent development in the design of breakwater concrete units has been to prioritize unit shapes that can remove altogether the issue of subjectivity in the CAU armor layer placement and construction quality control. The choice of CAU for a project does not arise by following objective quantitative criteria; the type of block has to be selected at the designer’s discretion, i.e., there is no objective decision tree to follow that leads to the best unit for the job It is the hydraulic stability, as traditionally predicted with use of a KD or similar stability factor, and the structural integrity that should be taken into consideration for CAU selection [8], because no matter how high the packing density or the placing tolerances achieved, the possibility of a significant number of rocking units under storm conditions cannot be discounted. It is likely to be a consequence of stochastic time and space variations in unit stability and the impact loads caused by the unavoidable collisions between CAUs while rocking or rolling under storm conditions

Objectives

Methods

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Discussion

Conclusion