Prerequesites

This tutorial presents some simple case studies with the purpose of demonstrating functionality in AquaSim.

It is assumed that the user is familiar with the basic principles of modelling and specifying material parameters in AquaEdit, as well as conducting analyses. If you are looking for an introduction to AquaSim we advise you to start with the Basic program tutorials

Introduction

This tutorial presents the variety of possibilities to investigate resonant motions caused by eigen periods in AquaSim. You will be introduced to how these periods can be calculated explicitly, and how they can be investigated in broader sense. Eigen periods are also commonly referred to as natural periods, or eigen frequencies. In this tutorial, we apply the term ‘eigen period’.

These types of periods are important in the sense of understanding the response of structures. It is determined by the distribution of mass and stiffness. Resonant motions can cause significant response in the structure, and in worst case failure of structural integrity.

Construction standards often require eigen periods to be investigated. As an example, the Norwegian standard NS 9415 section 9.2 states that “In order to determine dynamic amplification factors, it is necessary to know the natural frequency of the structure and variations in loads in both time and space.” Further, section 9.4.5.2 states “The risk of natural modes of vibrations in the structure shall be assessed and documented.” Similar requirements are common in other standards as well.