Effects of wind barriers on VIV performances of twin separated parallel decks for a long-span rail-cum-road bridge

Abstract

Wind barriers are frequently used on the railway bridges to improve operational safety of high-speed trains. However, the effects of wind barriers along the railway on the separated decks' Vortex-induced vibration (VIV) for rail-cum-road bridges are not fully known, whose VIV characteristics are more complicated because of aerodynamic interference effect (AIE). A number of dynamic sectional model wind tunnel tests for VIV performance were carried out. Three different heights (H) varying from 2 m to 4 m and four different ventilation ratios (R) varying from 20% to 50% for wind barriers on railway decks were examined under two opposite incoming flow directions at a fixed spacing. Results indicated that twin separated decks' overall VIV performance are poor when the wind flows from the railway upstream to the highway downstream. The wind barrier on railway deck can weak the remarkable fluctuating wind pressure coefficients, change the correlation coefficients and reduce the contribution coefficients of local distribution aerodynamic forces to the overall aerodynamic forces. It was effective to suppress VIV of the railway deck, and it also had a greater impact on the adjacent highway deck. The VIV-suppress ability of wind barriers is determined by the parameters of H and R. The wind barriers with H = 3 m and R = 30% were recommended to satisfy the requirements of twin decks after a comprehensive evaluation.