Study of Spatial Distribution of Wind Speeds at a Bridge Site in a Coastal Open Area

It is very important to determine the reasonable design wind speed at the bridge site in coastal open area for the study of wind resistance performance of long-span bridges. On the engineering background of Hongqimen Grand Bridge in Foshan City, Guangdong Province, first, taking the centre of the main span of the bridge as the circle center, the topographic model of the bridge site with a geometric scale of 1:500 is designed, the terrain, vegetation and buildings within a radius of 1 km are simulated. Then, the wind speed distribution at the bridge site in the coastal open area is studied by using terrain model wind tunnel test. Afterwards, conservatively selecting the mid-span measuring point as the research object, and taking the average surface roughness coefficients of different flow directions as the correction parameters, the design wind speed values of the specification method and the weighted average method are modified. Finally, the concept of landform partitioning is put forward firstly and the practical analysis process is given. According to the weight of geomorphic area and the weight of relative position of measuring point, the influence of nonuniform local landform and its relative position on surface roughness coefficient is studied quantitatively. The result shows that (1) in the coastal open area, the wind speed profiles of different wind directions match well with the specification recommended power exponent law, the distribution of surface roughness coefficients obtained from the fitting test data is relatively concentrated, the correlation is strong, and the surface roughness coefficients under most working conditions do not exceed the class B surface roughness coefficient in Wind-resistant Design Specification for Highway Bridges (JTG/ T 3360-01j2018), indicating that the incoming wind direction and the location of measuring points have little influence on the development of wind speed profile; (2) the corrected wind speed is 1.7% better than the value obtained by conventional method, and the recommended value of design wind speed at the bridge site is given; (3) the geomorphic weight is 16% higher than the position weight. The study result is beneficial to refine the reasonable value of surface roughness in the coastal open area.