Experimental investigation on aerodynamic interference of two kinds of suspension bridge hangers

摘要

In order to study the aerodynamic interference between cables of suspension bridge hangers, two types of cable test models with smooth and rough surfaces, which respectively correspond to parallel wire strand (PWS) and wire rope (WR) hangers, were manufactured, The comparisons between the features of wake-induced vibration of the PWS and WR hangers were carefully investigated by means of wind tunnel tests. First, a series of force measurement tests for the two types of hangers were carried out to measure the mean aerodynamic coefficients of the downstream cable within spatial region of 3 <= X <= 11 and -4 <= Y <= 4 with an interval of Delta X =Delta Y=0.25. The results of the force measurement tests show that obvious differences between the force coefficients of the downstream PWS and WR hangers are found. It seems that the variation amplitude of the force coefficient of the PWS hanger is significantly larger than that of the WR hanger. Moreover, the mean drag and lift coefficients of the downstream PWS hanger for U = 15 m/s are obviously different from those for U = 10 m/s, which indicates that the wake-induced vibration of the hanger might be strongly related to wind velocity (i.e., Reynolds Number). Second, a series of vibration measurement wind tunnel tests for the PWS and WR hangers were carried out to measure the responses of the downstream cables within the spatial region of 2.5 <= X <= 11 and 0 <= Y <= 4 with an interval of Delta X=Delta Y=0.25. The results show that obvious wake-induced vibrations are both observed for the PWS and WR hangers. However, it appears that the unstable region of the WR hanger is significantly less than that of the PWS hanger, which indicates that the WR cable seems to be more suitable than the PWS cable to be used as the hanger of suspension bridge. Parametric studies show that the wake-induced vibration of the PWS hanger is not divergent because the amplitude of the downstream cable stop increasing with the increase of the wind velocity, whereas the oscillation amplitude of the WR hanger keeps increasing with the increase of the wind velocity (up to 18 m/s in the wind tunnel). Moreover, it seems that the structural damping ratio have no significant influence on the critical wind velocity of the wake-induced vibration of the hanger of the suspension bridge. (C) 2019 Elsevier Ltd. All rights reserved.