Martin Nymann Svendsen

Ramboll

Rotating structures, like e.g. wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor–actuator system, governed by a resonant controller. The theory is here demonstrated by an active strut, connecting two cross-section...

This paper presents an assessment of the robustness of a 5200 m straight floating bridge towards aerodynamic instability (flutter). The assessment involves detailed studies of potential flutter mechanisms of the structure which show that critical aeroelastic vibration modes form as combinations of a relatively large number of still-air modes with l...

p>The sensitivities of wind-induced design section forces in the main girder of a suspension bridge with a span greater than 1000m are determined under variation of 20 different wind response calculation parameters. The investigated parameters cover turbulence characteristics such as length scales and correlation decay constants, as well as aerodyn...

The New Storstrøm Bridge in Denmark is a 3800m long concrete girder bridge with 44 standard spans of mostly 80m and two navigational spans of 160m which are stay cable supported. The foundations are constructed as direct pad foundations, i.e. with the ability of the caissons to slide and rotate on gravel beds. The bridge supports two high-speed rai...

A damping system targeting flutter instability motions of long‐span suspension bridges is presented. The damping system consists of four symmetrically located and equally tuned passive devices extracting energy from the structural system, based on the relative displacement between the pylons and the main suspension cables. Each device consists of a...

The design of the lower pylon and the foundation of large balanced cantilever bridges is often dominated by dynamic response to turbulent wind, and capacity verification relies heavily on cross-section analysis considering moment-force relations. This paper proposes a consistent method for general quantification of section force correlation effects...

In the last years, extreme climate events as thunderstorm and downburst are becoming increasingly frequent and widespread. These phenomena could significantly impact on the dynamic response of super long-span bridges since they are typically characterized by a sudden variations of the mean wind speed combined with large vertical angles of attack. T...

Aerodynamic stability and buffeting response due to turbulent wind have a fundamental importance for long-span bridge design. However, there are no benchmark cases that can be used as a reference estimate for an independent validation of the numerical methods and theoretical approximations. Therefore, the IABSE Task Group 3.1 proposal is to fill th...

p>This paper presents the ongoing benchmark results of IABSE Task Group 3.1. The task of this working group is to create benchmark results for the validation of methodologies and software programs developed to assess the stability and the buffeting response of long span bridges. Indeed, accurate estimations of structural stability and response to s...

An efficient computational procedure is developed for time simulation of buffeting and flutter response of suspension bridges. The structural model is reduced by quasi-static condensation leading to a typical 1:5 reduction of the number of dynamic degrees of freedom. The turbulent wind field is represented by a convected fully three-dimensional vel...

IABSE Task Group 3.1 has the mandate to define reference results for the validation of methodologies and programs used to study both stability and buffeting responses of long-span bridges. To this end, the working group set up a benchmark procedure consisting of several steps with increasing complexity to define reference results useful for this va...

IABSE Task Group 3.1 has the mandate to define reference results for the validation of methodologies and programs used to study both stability and buffeting responses of long-span bridges. These tools for the simulation of the aeroelastic behaviour are fundamental in the safe design of bridges and they should be validated. The working group decided...

p>This paper is part of a series of publications aimed at the divulgation of the results of the 3-step benchmark proposed by the IABSE Task Group 3.1 to define reference results for the validation of the software that simulate the aeroelastic stability and the response to the turbulent wind of super-long span bridges. Step 1 is a numerical comparis...

p>The IABSE Task Group 10 (super-long span bridge aerodynamics) has the mandate to create a standard procedure for validation of methodology and software programs applied for stability and buffeting response analyses of super-long span bridges. Precise estimations of structural stability and response to strong winds are critical for the successful...

For long span bridges the wind-induced dynamic response is a design driving factor and therefore continuously a subject for detailed analysis. Traditionally both buffeting and stability calculations have been considered in the frequency domain. However, this yields a limitation in accounting for turbulence when considering the stability limit and f...

The New Varodd Bridge is a 655m concrete girder bridge with four main spans with a maximum length of 260m. The bridge will be located in a very narrow position between the existing Varodd suspension bridge on the southern side and the existing Varodd girder bridge on the northern side. The new bridge will be constructed as a balanced cantilever wit...

The paper describes a direct auto-regressive simulation method for wind fields. It makes use of the correlation of the wind field in the transverse direction to permit a single step multi-component formulation with free distribution of the simulation points in the transverse plane. While the simulated field will typically need a small time step for...

The wind-induced vibrations of super tall buildings become excessive due to strong wind loads, super building height and high flexibility. Tuned mass dampers (TMD) and tuned liquid column dampers (TLCD) have been widely used to control the vibration for super tall buildings for decades. As an economical vibration control option, the fire protection...

In connection with the conceptual design of the New Sotra Bridge the impact of deck wind shields has been investigated. Using computational fluid dynamics it is shown that permeable wind shields generate a significantly improved wind environment on the bridge deck compared to that achieved using fully closed wind shields. Further, it is shown using...

The Forth Replacement Crossing is a large cable-stayed road bridge planned to cross the Firth of Forth estuary close to Edinburgh, Scotland. The cable arrangement is unique for a bridge of this scale and the slender design indicates that the bridge may be sensitive to wind effects. The results of theoretical and experimental buffeting response eval...

Rotors with blades, as in wind turbines, are prone to vibrations due to the flexibility of the blades and the support. In the present paper a theory is developed for active control of a combined set of vibration modes in three-bladed rotors. The control system consists of identical collocated actuator-sensor pairs on each of the blades, and targets...

This thesis presents a framework for structural modeling, analysis and active vibration damping of rotating wind turbine blades and rotors. A structural rotor model is developed in terms of finite beam elements in a rotating frame of reference. The element comprises a representation of general, varying cross-section properties and assumes small cro...

The paper deals with introduction of damping to specific vibration modes of wind turbine blades, using a resonant controller with acceleration feedback. The wind turbine blade is represented by three-dimensional, two-node finite elements in a local, rotating frame of reference. The element formulation accounts for arbitrary mass density distributio...

The present paper deals with addition of damping to a specific vibration mode of a rotating beam using an active resonant controller. A recent general format for controller tuning is adopted and applied in a three-dimensional finite beam element formulation. The effects on controller tuning and performance due to changes in modal properties of a ca...

In this paper, details regarding and the experimental validation of the "response spectrum" methodology for the determination of vertical footbridge response are presented. The methodology is inspired by the well-established response spectrum approach used in the majority of the world's current seismic design codes of practice. A basic outline of t...

Extended Abstract Rotors with blades as e.g. in wind turbines are prone to vibrations due to the fluctuating loading and flexibility of the blades and the support. A theory is developed for active control of a combined set of vibration modes in three-bladed rotors. The control system consists of identical collocated actuator-sensor pairs in the for...