Operational Modal Analysis in the Presence of Harmonic Excitations

The dynamic behavior of structures is a primordial factor determining its structural stability, reliability and lifespan. Therefore, in many advanced engineering applications, it has become essential to predict the dynamics of new designs through simulations, to identify the dynamic characteristics of prototypes and finally to monitor systems in...

Identifying Structural Parameters of an Offshore Wind Turbine using Operational Modal Analysis

Optical monitoring and operational modal analysis of large wind turbines

Identification of the dynamic properties and the corresponding structural response of wind turbines is essential for optimizing the energy produced, ensuring safe and reliable operation and increasing the life-time of the system. As the sizes of modern wind turbines increase, their dynamic behaviors get more complicated and it becomes more...

Development of a cutter ladder vibration model

Structural vibrations are a known cause of damage to offshore structures and equipment. A Cutter Suction Dredger (CSD) is a dredge vessel known to vibrate heavily during operation. Primary cause of these vibrations is the cutting process, performed to cut and excavate soil from the seabed. A component prone to damage is the cutter ladder, a...

Structural Health Assessment through Vibration Monitoring on FPSOs

In the offshore oil and gas industry, production takes place at more and more remote locations, with Floating Production Storage Offloading units (FPSO’s) often being selected for field development. These units may remain on station during their entire lifetime while operating under adverse weather conditions. Inspections, which have to be...

Operational modal analysis on a lighthouse structure subjected to ice actions

The sea ice interaction with a structure may cause system changes and affect the feasibility of common approaches to track modal parameters. In this paper, a covariance-driven stochastic subspace identification method is used to identify the natural frequencies from 190 time series of ice actions against a lighthouse structure. The results...

A Benchmark Study on Operational Modal Analysis System Identification Algorithms for Operating Offshore Wind Turbines

Recently, Offshore Wind Turbines (OWT) have attracted great attention in an effort to make a shift from fossil-based energy sources towards an enhanced sustainable and renewable energy production. In order to achieve the renewables targets and reduce the cost of wind energy, OWTs are consistently increasing in size. Therefore, research has...

Damping Identification of Operational Offshore Wind Turbines: An Operational Modal Analysis Approach in the Presence of Harmonics

Offshore Wind Turbine (OWT) structural design can be optimized to reduce structural costs, thereby lowering wind energy costs. Increasing turbine size and further structural cost reduction require more advanced insights into the dynamic system. One practice of analysing these vibrating structures is called Operational Modal Analysis (OMA). OMA...

Operational Modal Analysis on a Tied-Arch Railway Bridge: A case study to determine the natural frequencies and mode shapes from in-situ accelerational measurements

Due to increasingly efficient engineering of the last decades, the design process for civil structures is heading in the direction of optimal solutions. Among other things, the reduction in self-weight enhances the susceptibility to dynamic loads. As the process for the determination of realistic modal parameters from a digital model often...

Modal analysis of an operational offshore wind turbine using enhanced Kalman filter-based subspace identification

Operational modal analysis (OMA) is an essential tool for understanding the structural dynamics of offshore wind turbines (OWTs). However, the classical OMA algorithms require the excitation of the structure to be stationary white noise, which is often not the case for operational OWTs due to the presence of periodic excitation caused by...

Dynamic Characterization of a Real-Scale Prestressed Concrete Beam Tested Until Failure

In this work, dynamic characterization of a simply supported beam is carried out during different steps in a failure load test. The main goal of this work is to evaluate the evolution of the structural dynamic parameters of the beam with different status of damage. Real-scale prestressed concrete beams are tested to investigate its shear...

Hybrid operational modal analysis of an operative two-bladed offshore wind turbine

Two-bladed offshore wind turbines regained interest in finding the most profitable way of generating wind energy. Wind industry companies demand the safe operation of two-bladed offshore wind turbines. To guarantee safe operation, the companies perform operational modal analyses to investigate modal properties variation which might be allocated...