Imperfect Correlation of Vortex-Induced Fluctuating Pressures and Vertical Forces on a Typical Flat Closed Box Deck

Abstract

A wind tunnel test of synchronized pressure measurement on a spring-suspended sectional model of a flat closed box deck at a large scale of 1/20 was carried out by taking Xiangshan Harbour Bridge in China as background. The chordwise correlation of the fluctuating aerodynamic pressures (FAP) on the surface of the box deck was then investigated at both stationary state and vortex-induced resonance (VIR) states of the deck model. Afterwards, an approximate approach was developed for estimating the spanwise correlation coefficients of pure vertical vortex-shedding force (VSF) on the deck under VIR state. On this basis, the spanwise correlation coefficients of both the integrated total vertical fluctuating aerodynamic force (FAF) and the pure vertical VSF on the flat box deck were then studied and compared to each other quantitatively at the stationary state as well as the VIR states at various wind speeds. Finally, the spanwise correlation coefficients of the surface FAP at some typical positions on the deck cross section were calculated and compared with that of the total vertical FAF and the vertical VSF. The results show that the chordwise correlation of the FAP on stationary deck is not strong at most part of the deck surface, however, can be enhanced with the increase of incident wind speed. The chordwise correlation of FAP can also be enhanced quite significantly by the deck oscillation under VIR states, but is still imperfect. Furthermore, the spanwise correlations of FAP at different positions on the deck cross section are clearly different from each other, and much weaker than that of the total vertical FAF, for both the stationary state and the VIR states of the deck. However, they are generally much stronger than that of the pure VSF in cases of notable VIR, and much weaker in the cases of slight VIR, such as near the onset of VIR. The spanwise correlation characteristics of both the pure vertical VSF and the total vertical FAF are hence very different from those of the surface pressures. Moreover, the spanwise correlation of the total vertical FAF on cross sections can be greatly intensified by the VIR because of the existence of a large portion of vortex-induced self-excited force (VISEF). On the other hand, the spanwise correlation of the vertical VSF under the VIR states is much weaker than that of total vertical FAF as well as that of the pure vertical VSF under the stationary state at same wind speeds. Finally, the variations of the spanwise correlation of both the total vertical FAF and the pure vertical VSF with the response displacement of VIR is quite complicated. The most violent VIR, the most correlated total FAF and the most correlated VSF occur generally at different wind speeds.

Full bridge analysis of nonlinear vortex-induced vibration considering incomplete span-wise correlation of vortex-induced force

“…Furthermore, the test results also indicate that the span-wise correlation of the total VIF during VIV will increase as the section configuration evolves from blunt body to streamline body. The phenomena that structural motion may enhance the span-wise correlation of VIF on a similar flat STR girder of about 9.1:1 width-to-depth ratio, a centrally-slotted box girder and a 5:1 width-to-depth ratio REC girder has also been reported by Meng et al (2015), Zhu et al (2017) and Zhang et al (2022), respectively.…”

“…As discussed in Meng et al (2015), the span-wise correlation coefficient of the PVSF ρ VS on the flat box deck, ρ VS , can be expressed by the following equation ( 11):…”

“…The values of C VS of the flat box deck of Xiangshan Hoabour Bridge were determined via pressure measurement wind tunnel tests of sectional model with a large scale of 1/20. The details about the test and results can be found in Meng et al (2015) and the main results of parameter C VS are also provided here for convenience, see Table 2.…”

“…Further noticing that the span-wise correlation coefficients of VIF exceed 0.9, even approach 1.0 for flat STR girders (Meng et al, 2015; Sun et al, 2019) and a centrally-slotted girder (Zhu et al, 2017), it is thus reasonable to regard the SEF component of VIF as fully correlated along the girder span, and to attribute the span-wise incomplete correlation behaviour of VIF to the span-wise incomplete correlation of PSVF. Based on this assumption, Meng et al (2015) extracted the span-wise correlation coefficient of PVSF from that of the total VIF and found that the span-wise of PVSF was rather poor. Therefore, it is better to separately consider the span-wise correlation properties of the SEF and PVSF in full-bridge VIV analysis.…”

Experimental Study on the Spanwise Correlation of Vortex‐Induced Force Using Large‐Scale Section Model

“…Ehsan et al [10] found that the freedom in which the structure oscillated would affect the spanwise correlation of the aerodynamic forces of the main girder with an H section shape and a side ratio of 4. Meng et al [19] investigated the imperfect correlation of vortex-induced fluctuating pressure and the integrated vertical fluctuating force on the flat closed box deck using a large-scale section model and found that it can be greatly enhanced or changed by the deck vibration for most parts of the deck. Xu et al [20] studied the characteristics of torsional VIV and the correlation between the surface pressure and VIF for a streamlined box girder using a small-scale section model.…”