EXPERIMENTAL INVESTIGATION ON EFFECTS OF WIND BARRIER ON AERODYNAMIC STABILITY OF BRIDGE AND VEHICLE ON BRIDGE

Abstract

This research intends to experimentally investigate the effects of the wind barrier on the aerodynamic response of the bridge, the crosswind environment, and the aerodynamic forces of the vehicle on the bridge. The discussion focuses on the wind-barrier section configuration, i.e., Straight-line Type (ST) and Curved-line Type (CT), and the Opening-area Ratio (OR) of the wind barrier, which is the ratio of the area of its total openings to its windward-surface area. A streamline box girder model of side ratio B/D = 9 (B: girder width; D: girder height) with different wind barriers is applied in a series of wind tunnel tests, i.e., the vertical and torsional one-degree-of-freedom (1DOF) free vibration tests, and wind velocity measurement on the girder. The wind barrier of OR = 0% resulted in the vortex-induced vibration and torsional flutter of the girder because it promoted the detachment of the separated flow from the girder, however increasing OR stabilized these aerodynamic instabilities because increasing OR resulted in increasingly strong turbulent flow on the girder. The wind velocity below the vehicle height on the girder was significantly decreased by decreasing OR, while the wind barrier of OR = 50% still reduced the wind velocity by about 50% compared with that without the wind barrier. As a result, based on the measurement of the aerodynamic forces on a simplified vehicle on the girder, enlarging OR increased the drag force coefficient (Cs) of the vehicle, whereas the wind barrier of OR = 50% still reduced Cs by about 50% compared with that without wind barrier.