PhD Defence by Randi Nøhr Møller - "Aerodynamic Stability of Long Span Bridges"

With a desire to build even longer bridges, it is of interest to improve the numerical tools for aerodynamic response calculations as well as the flutter limit assessment, and to investigate the possibilities for increasing the stability limit. The work conducted within the field of aerodynamic stability and response of long-span bridges is presented in three parts. The first part describes the conditional mean field wind simulation method as an efficient and flexible alternative to existing wind simulation methods. The mean field method is an auto-regressive process allowing for a stepwise update of the turbulence components based on a relatively compact memory while at the same time representing the statistical properties of the turbulence field with high accuracy. The second part focuses on the representation of aero-elastic forces for bridge response evaluation and flutter assessment. The aero-elastic forces are represented as additional state-variables in a compact first-order state-space form. The model size is reduced by quasi-static condensation and a second order momentum-based time integration procedure is applied. The final part describes a damping system for suspension bridges. The damping system consists of four equally calibrated, symmetrically located devices working on the relative displacement between the pylons and the main suspension cables. The damping system targets the modes of interest for unstable flutter motion and it was found to provide a significant increase of the critical wind speed.



Main Supervisors:
Associate Professor Jan Becker Høgsberg, DTU Mechanical Engineering
Professor Steen Krenk, DTU Mechanical Engineering

Co-supervisor:
Chief Consultant Martin Nymann Svendsen, Rambøll

Examiners:
Associate Professor Jon Juel Thomsen, DTU Mechanical Engineering
Professor Søren R.K. Nielsen, Dept. of Civil Engineering, Aalborg University
Professor Ole Andre Øiseth, NTNU, Dept. of Structural Engineering, Norway

Chairman:
Associate Professor Niels Leergaard Pedersen, DTU Mechanical Engineering 

Tidspunkt

ons 11 sep 19
14:00 - 18:00

Arrangør

DTU Mekanik

Hvor

Building 341, Auditorium 021
Technical University of Denmark