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The dynamic behavior of lively footbridge is a complex problem. Recently there were numerous publications and recommendations related to the dynamic nature of footbridge. The complicated procedure which was set in a number of instructions and standards says nothing about actions aimed at avoiding critical frequency range in structure. In the paper, results of dynamic in-situ tests of cable-stayed all-GFRP (Glass Fiber Reinforced Polymer) footbridge are presented. Fiberline Footbridge, located in Kolding city in Denmark, was constructed in 1997 using 12 different pultruded profiles all made of GFRP material. The dynamic characteristics as well as vertical response of the tested footbridge under human excitation are given and discussed. Firstly, in order to estimate the dynamic properties of the footbridge, a series of free-decay responses under human jumping were conducted. The fundamental frequency of the analyzed structure was within a critical range. A methodology for footbridge classification with regard to their dynamic sensitivity was worked out and the correlation between the structure's properties and its dynamic response under pedestrian excitation was formulated. It was found that the analyzed footbridge fulfilled vibration comfort criteria elaborated by technical guide Sétra, however, more restricted acceleration limits suggested by Eurocode were not met.

Abstract. The aim of this paper is to investigate of dynamic characteristics of cable-stayed Fiberline Bridge in Kolding, Denmark, made entirely of Glass Fiber Reinforced Polymer (GFRP) composite. During examination based on in situ free-decay measurements and using accelerometers under human jumping the primary five natural frequencies, corresponding mode shapes and damping ratios of the footbridge were identified. The Peak Picking (PP) and Frequency Domain Decomposition (FDD) approaches were applied to identify the natural frequencies and mode shapes. The corresponding damping ratios were extracted by a linear regression on the extremes of modal decays. The estimated damping ratios were compared with published data for selected footbridges made of various conventional materials. The obtained experimental results provide a relevant data regarding the dynamic response prediction or structural health monitoring of all-GFRP composite footbridges.

The study contributes to the explanation of flow behaviour and the basis of phenomena existing during twodimensional airflow around an ice-accreted cylinder, representing the section model of a bridge cable. The geometrical features and flow characteristics of the near-wake flow patterns of the iced cable were investigated within the Reynolds number range of 2.2⋅10 4-6.4⋅10 4 in low and moderately turbulent flow. The experimental procedure was conducted to create ice accretion on the cylindrical model. The shape of the ice was registered using a photogrammetry method. For the aerodynamic investigations the ice-accreted model was reproduced at a smaller scale by means of 3D printing. Representative snapshots of the flow field behind the stationary horizontal simulated iced cable were digitally analyzed by the Particle Image Velocimetry technique. The flow visualization provided quantitative data about the velocity and the direction of flow streams within both the near-wake and the sidewise regions of distributed flow around the model. Evidence of the existence of the vortex excitation process was obtained at three principal angles of attack. The characteristics of the vortex street and the location of the flow boundary layer separation points were recognized. The obtained results were compared with results for a smooth cylinder.

This paper presents the wind tunnel investigations of the mean aerodynamic coefficients of the stationary iced model in cable-stayed bridges. The investigations were performed in a Climatic Wind Tunnel Laboratory at the Czech Academy of Sciences in Telč. The icing of the inclined cable model was made experimentally. The shape of the iced model was mapped by a photogrammetry method. The new iced cable model was made by using a 3D printer. The aerodynamic drag, lift and moment coefficients were determined with respect to three principal angles of wind attack within the range of the Reynolds number between 2.5•10 4 and 13.6•10 4 at a turbulence intensity of 5 %. It was found that the drag coefficient values of the iced cable model are higher than for a circular smooth cylinder. The obtained results could constitute a basis to formulate a mathematical description of the wind load acting on the iced cables of cable-supported bridges.