1,721,034 research outputs found
Effect of the low-frequency turbulence on the aeroelastic response of a long-span bridge in wind tunnel
Get PDFThe influence of the low frequency turbulence components on the buffeting response of long span bridges was studied through experimental tests performed on a full bridge aeroelastic model in the wind tunnel of the Politecnico di Milano, using an active turbulence generator producing a correlated deterministic harmonic turbulence. The experimental evidence underlined the nonlinear effect of the low frequency incoming turbulence on the dynamic resonant response of the structure at higher frequencies. Numerical simulations are used to explain the bridge behavior considering the variation of the aeroelastic properties of the bridge with the instantaneous angle of attack and reduced velocity. Even though wind tunnel experiment uses an oversimplified wind spectrum with an intentionally high correlation along the main span, it helps to understand the nonlinear interaction between the low frequency and the high frequency buffeting response on a full bridge
Simplified estimation of the train resistance parameters: full scale experimental tests and analysis
Get PDFA CEN standard (EN 14067-4, 2005) describes the methodologies for the
assessment of the running resistance of railway vehicles starting from full-scale test
measurements. According to this standard, the speed dependent terms of the
equation of Davis [1] have to be determined by means of coasting tests. In this
paper, a new method to estimate the running resistance coefficients from a full-scale
coasting test is proposed and compared with the two methods proposed in the CEN
standard (the regression method and the speed history identification method). The
main advantage of this new method is that it does not require the railway line
characteristics to be known and it will be shown that the new method is able to
evaluate the coefficients with an accuracy equivalent to that of the other methods
considered
Experimental investigation of low-frequency turbulence effects on the aeroelastic response of model-scale long span bridge
Get PDFInfluence of local deck vibrations on the evaluation of the maximum acceleration of a steel-concrete composite bridge for a high-speed railway
Get PDFEuropean design standards have established an upper limit on the deck acceleration of the high-speed railway bridges, however the influence of local vibrations of the deck members is rarely considered when modelling the vibrational responses of bridges. To evaluate how the inclusion of local deck vibrations might influence predictions of the maximum acceleration, detailed measurements were taken from a steel-concrete composite box-girder bridge on the Italian high-speed railway, and a numerical model of the system was developed. Deck vibrations were measured during high-speed train passages at the maximum train speed of 374 km/h, and compared against a numerical model of the vehicle-bridge system. This analysis revealed that the maximum deck acceleration is 1.3 times greater than the acceleration of the bridge girders, because of the sixth- and seventh-order resonance between the deck’s local vibration modes and the structure with a train running at high speeds over 300 km/h. Moreover, when considering local deck vibrations in the numerical model, we found that the interaction between transient local rail deformations and the vehicle travelling on the rails can increase the acceleration of the deck through resonance
Numerical-experimental analysis of the slipstream produced by a high speed train
No full textThe recent development of high-speed trains over the last decade led to a growing interest in their aerodynamics. A train at full operational speed generates a strong induced airflow that may damage infrastructures near the trackside and endanger people near the rails. Nowadays the tests required for the train homologation are based on full scale measurements of the airspeed taken in specified positions close to the railway line. An important part of the work was initially dedicated to the data analysis of an extensive experimental campaign performed on the Italian high-speed line, in order to obtain reliable results to be used for comparison with CFD results. These ones have been performed on the full-scale train geometry using an URANS approach with a wall treatment based on wall functions, checking mesh and turbulence models dependencies. The full-scale simulations highlighted the great complexity of the problem being the comparison with the experimental measurements performed close to the shear layer of the train boundary layer. Encouraging results are obtained from the numerical analysis on the full-scale train geometry indicating the ability of the URANS coupled with the SST turbulence model in the prediction of both the train induced flow and the turbulent structures around it
Numerical and Experimental Analysis of the Pressure Signature for different High-Speed Trains
Get PDFThis paper describes a procedure for the validation of numerical codes able to reproduce the pressures in tunnel due to the passage of trains. In the first step, the parameters of the numerical code are set by matching the train-tunnel pressure signature measured during a single-passage of different types of train within the tunnel and in the second step, without changing the parameters, the crossing of two trains is simulated.
Within the paper, the methodology is applied to the numerical mono-dimensional code DB-Tunnel while the experimental data are those collected during an experimental research programme carried out in the tunnel La Fornace, on the Italian high-speed railway from Roma to Firenze. The accuracy of the numerical code estimation is evaluated in terms of the maximum pressure generated in the tunnel by the train passing/crossing because this is the key parameter, according to the TSI standard for railway infrastructures
A case-study of double multi-modal bridge flutter: Experimental result and numerical analysis
No full textExperimental and numerical evaluation of the aerodynamic drag for different configuration of a conventional train
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