Simulation of non-homogeneous wind processes, comparison between numerical and experimental model of a bridge
Abstract
The scaled aerodynamic model of a bridge is often tested in the boundary layer wind tunnel laboratory (BLWTL). In this study a numerical model of the Baluarte Bridge subjected to wind loading is investigated. The scaled full bridge aerodynamic model was previously studied at the University of Western Ontario, Canada. For the numerical model a finite element model (FEM) is implemented, and the characterization of the buffeting forces are considered on the frequency and time domain. In the former case, the so-called pseudo excitation method is used to characterize the wind load, while in the latter the spectral representation method (SRM) is used to generate the synthetic wind speed field. In both cases, an inhomogeneous stochastic process is generated. The corresponding energy of the wind is formulated in terms of the power spectral density function, and appropriate coherence functions. Apart from the formulation of non-homogeneous wind, the simulation of non-stationary fluctuating winds at multiple points is also considered. Both the frequency domain approach and the time domain approach are used to evaluate the root-mean-square (RMS) displacements, due to the fluctuating horizontal and vertical winds. For the time domain, the lateral RMS displacement obtained from the FEM is similar to the one obtained on the experimental tests. In contrast, for the frequency domain approach the results are on average 20-30% and 2-15% below, for the case of buffeting and self-excited forces, respectively. For the vertical RMS displacement, the values are on average 30% below, with an exception when the wind speed of 45 m/s is considered. In this case, the difference becomes 30% for the frequency and 20% for the time domain. The results indicate that by using the large deformation option on the time domain analysis, the displacements at high wind speed are closer to those ones predicted under the BLWTL. A sensitivity analysis conducted on the decay parameter indicates that the exponential decay coefficients of the coherence could significantly influence the calculated RMS values, particularly for the case of vertical displacements.