Li Xiaozhen

Fluctuating wind velocity spectra of moving vehicle under horizontal crosswind

In order to study the wind speed spectrum of moving vehicles under horizontal crosswind with different vehicle speed/wind speed ratios, the Taylor “frozen” turbulent flow assumption is applied to derive the auto-correlation coefficient function of the moving point. The self-power spectral function of the moving point is solved by the Fourier transform analysis. Based on the existing expression forms of the fluctuating wind speed spectra, the analytical expression of the self-power spectral function of the moving point of which wind speed is perpendicular to the vehicle speed is derived directly by the integral transformation. Research shows: due to the movement of vehicles, the longitudinal fluctuating wind speed spectrum of moving point is shifted to high frequency. With the increase of vehicle speed, the amplitude decreases and then increases gradually. Meanwhile, the amplitude of lateral fluctuating wind speed spectrum of moving point decreases firstly with the increase of vehicle speed, and then increases gradually.

SAFETY ASSESSMENT AND REINFORCEMENT TECHNIQUE FOR DECK STEEL TRUSS BRIDGE UNDER INCREASING SPEED

This paper introduced reinforcement techniques to strength the lateral stiffness of the deck steel truss bridge on an existing railway under increasing train speed.. The 14 reinforcement schemes are optimally studied through comparing their dynamic responses of vehicles and bridges by means of the vehicle-bridge interaction models, which take track irregularities and wheel hunting movement into account. The investigation indicates that the scheme of strengthening horizontal bracing systems, transverse bracing systems and main chord is effective and practical to decrease the lateral decrease the lateral displacement. And all the dynamic properties are within the range of the values regulated in respective Chinese codes, such as natural frequencies, lateral displacement and acceleration, derailment coefficient, wheel-weight decrement ratio, lateral sperling index. After the reinforcement, the lateral stiffness and dynamic properties of the deck truss girder bridge meet the requirements of safety service for freight train at the speed of 80 km·h -1 and for passenger train at the speed of 200 km·h -1 .