Arndt Goldack

Human-induced vibration of steel structures (Hivoss)

The guideline and background documents have been translated into different languages and published on a project web page (www.stb.rwth-aachen.de/projekte/2007/HIVOSS/ download.php) that may be easily found by an Internet search for ‘Hivoss’. At this site the guideline and background documents can be downloaded as a free PDF. This download page has received a lot of interest, resulting in 1 900 downloads of the footbridge guideline and 1 000 downloads of the floor guideline up to 30 March 2009.

Accelerometer-based estimation and modal velocity feedback vibration control of a stress-ribbon bridge with pneumatic muscles

Lightweight footbridges are very elegant but also prone to vibration. By employing active vibration control, smart footbridges could accomplish not only the architectural concept but also the required serviceability and comfort. Inertial sensors such as accelerometers allow the estimation of nodal velocities and displacements. A Kalman filter together with a band-limited multiple Fourier linear combiner (BMFLC) is applied to enable a drift-free estimation of these signals for the quasi-periodic motion under pedestrian excitation without extra information from other kinds of auxiliary sensors. The modal velocities of the structure are determined by using a second Kalman filter with the known applied actuator forces as inputs and the estimated nodal displacement and velocities as measurements. The obtained multi-modal velocities are then used for feedback control. An ultra-lightweight stress-ribbon footbridge built in the Peter-Behrens- Halle at the Technische Universitat Berlin served as the research object. Using two inertial sensors in optimal points we can estimate the dominant modal characteristics of this bridge. Real-time implementation and evaluation results of the proposed estimator will be presented in comparison to signals derived from classical displacement encoders. The real-time estimated modal velocities were applied in a multi-modal velocity feedback vibration control scheme with lightweight pneumatic muscle actuators. Experimental results demonstrate the feasibility of using inertial sensors for active vibration control of lightweight footbridges.

Stress Ribbon Bridges: Mechanics of the Stress Ribbon on the Saddle

AbstractThe most slender and flexible footbridges are stress ribbon bridges. One kind of these elegant and simple bridges consists of two hanging steel ribbons, usually made of steel, which carry concrete deck panels and are anchored between two heavy abutments. At the anchorage and on intermediate supports the ribbons are often supported by saddles that are curved so that the additional bending stresses in the ribbon, which occur there, stay within allowable limits. The magnitude and the distribution of the bending stresses, the transverse pressure the ribbons exert on the saddle, and stress changes in the region of the detachment point caused by live loads are crucial for the dimensioning of these ribbons. A clear understanding of these issues via parametric studies, analytical solutions, and confirmation by finite-element (FE) analyses are provided in this paper. The findings presented here can also be used for other saddle systems, such as those used in cable-stayed and extradosed bridges.

Effect of Relative Displacement of Strands Bent Over Circular Saddles on Fatigue Life Under Fretting Conditions

High strength steel strands are widely used as main supporting elements in cable-stayed and extradosed bridges. Saddle systems have recently been introduced as an alternative to attaching the stays using anchor heads to pylons. As a drawback, strands installed in such systems are subjected, in addition to plain fatigue, to the fretting phenomenon, which accelerates fatigue damage and shortens the fatigue life of the strands.