Journal of Fluids and Structures 93 (2020) 102846
Contents lists available at ScienceDirect
Journal of Fluids and Structures
journal homepage: www.elsevier.com/locate/jfs
Experimental investigation of wind-induced vibrations of main cables for suspension bridges in construction phases
Xugang Hua a,lowast;, Chaoqun Wang a, Shengli Li b, Zhengqing Chen a
a Key Laboratory for Wind and Bridge Engineering of Hunan Province, College of Civil Engineering, Hunan University, Changsha 410006, China
b Zhengzhou Key Laboratory of Disaster Prevention and Control for Cable Structure, School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
a r t i c l e i n f o
Article history:
Received 4 August 2019
Received in revised form 3 November 2019 Accepted 17 December 2019
Available online xxxx
Keywords: Suspension bridges Main cables Galloping
Wind tunnel test Vibration mitigation
a b s t r a c t
The main cables of suspension bridges show a changing cross-sectional shape with the evolution of construction phases, and they may suffer from severe wind-induced vibrations at certain conditions. The primary objective of this research was to examine the aerodynamic performance of the main cable in construction phases and to develop appropriate countermeasures to eliminate the potential wind-induced vibrations. Two cross-sections with different shapes of a main cable were chosen, and a series of wind tunnel tests were performed in a reduced wind velocity range of 32–366 using elastically mounted sectional models. Galloping occurred for the two cross-sections under certain wind incidence angles when a critical velocity was reached. No obvious hysteresis phenomenon of galloping was observed in the tests. The steady amplitude of galloping increased linearly with wind velocity and the increasing rate almost kept constant for different structural damping ratios. The aerodynamic nonlinearity, rather than the structural damping nonlinearity, is the main source leading to the limited amplitude oscillation. An empirical expression of galloping amplitudes for the two cross-sections was derived based on the test data. Meanwhile, the critical wind velocity was studied in a Scruton (Sc) number range of 108–4196 (as varied by changing the initial structural damping ratio between 0.093% and 3.62%). Results showed that the Den Hartog criterion was applicable to forecast the possibility of galloping, but not able to estimate the critical wind velocity for the main cable. Linear fitting method can be used to predict the critical velocity based on the experimental data. Finally, three vibration mitigation measures were studied, and a combination of structural and aerodynamic measures was recommended for galloping mitigation of main cables.
copy; 2019 Elsevier Ltd. All rights reserved.
Introduction
Erection of main cables is an essential step for construction of a long-span suspension bridge. During the construction phases, the stiffening girder has not been erected and main cables are suspended on bridge towers independently of other structures. As a result, the rigidity of a main cable is very small, and the cable will be sensitive to wind excitations. Large-amplitude wind-induced vibration of main cables has been observed during the construction phases of the 1650 m
lowast; Corresponding author.
E-mail address: cexghua@hnu.edu.cn (X.G. Hua).
https://doi.org/10.1016/j.jfluidstructs.2019.102846 0889-9746/copy; 2019 Elsevier Ltd. All rights reserved.
Fig. 1. Main cable during construction.
(main span) Xihoumen Bridge (Li and Ou, 2010; An et al., 2016) and the 1480 m (main span) Second Dongting Lake Bridge in China, and the safety of structures as well as the construction workers were seriously threatened.
Generally, the main cable of long-span suspension bridges consists of more than one hundred identical steel strands, and the steel strands are installed one by one (Fig. 1). Consequently, the main cable may experience a number of cross- sectional shapes during construction phases, and its aerodynamic performance can be foreseen to very complex. Main cables during construction may suffer vortex-induced vibration, turbulence-induced buffeting and galloping in wind flow. A certain amount of fundamental work relating to the wind-induced vibration of main cables during construction has been published. Galloping, as the primary source of wind-induced vibrations for main cables, is a kind of aerodynamic instability, and has a strong destructive power on account of the possible divergent amplitude. When a main cable shows a special cross-sectional shape at a certain construction stage, it will have a risk of galloping, and large-amplitude oscillation will occur when the wind velocity reaches a critical value (Li et al., 2017). Both wind tunnel test and numerical simulation have been conducted to study the aerodynamic performance of main cables. Results based on the Den Hartog criterion (Den Hartog, 1932) indicate that galloping may occur on main cables not only erected by the common steepled method (An et al., 2016), but also by the flat-topped method (Li et al., 2017).
Results of previous research provide an academic reference of wind resistance for main cable construction, since several typical cross sections of main cable have bee
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Journal of Fluids and Structures 93 (2020) 102846
Contents lists available at ScienceDirect
Journal of Fluids and Structures
journal homepage: www.elsevier.com/locate/jfs
Experimental investigation of wind-induced vibrations of main cables for suspension bridges in construction phases
Xugang Hua a,lowast;, Chaoqun Wang a, Shengli Li b, Zhengqing Chen a
a Key Laboratory for Wind and Bridge Engineering of Hunan Province, College of Civil Engineering, Hunan University, Changsha 410006, China
b Zhengzhou Key Laboratory of Disaster Prevention and Control for Cable Structure, School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
a r t i c l e i n f o
Article history:
Received 4 August 2019
Received in revised form 3 November 2019 Accepted 17 December 2019
Available online xxxx
Keywords: Suspension bridges Main cables Galloping
Wind tunnel test Vibration mitigation
a b s t r a c t
The main cables of suspension bridges show a changing cross-sectional shape with the evolution of construction phases, and they may suffer from severe wind-induced vibrations at certain conditions. The primary objective of this research was to examine the aerodynamic performance of the main cable in construction phases and to develop appropriate countermeasures to eliminate the potential wind-induced vibrations. Two cross-sections with different shapes of a main cable were chosen, and a series of wind tunnel tests were performed in a reduced wind velocity range of 32–366 using elastically mounted sectional models. Galloping occurred for the two cross-sections under certain wind incidence angles when a critical velocity was reached. No obvious hysteresis phenomenon of galloping was observed in the tests. The steady amplitude of galloping increased linearly with wind velocity and the increasing rate almost kept constant for different structural damping ratios. The aerodynamic nonlinearity, rather than the structural damping nonlinearity, is the main source leading to the limited amplitude oscillation. An empirical expression of galloping amplitudes for the two cross-sections was derived based on the test data. Meanwhile, the critical wind velocity was studied in a Scruton (Sc) number range of 108–4196 (as varied by changing the initial structural damping ratio between 0.093% and 3.62%). Results showed that the Den Hartog criterion was applicable to forecast the possibility of galloping, but not able to estimate the critical wind velocity for the main cable. Linear fitting method can be used to predict the critical velocity based on the experimental data. Finally, three vibration mitigation measures were studied, and a combination of structural and aerodynamic measures was recommended for galloping mitigation of main cables.
copy; 2019 Elsevier Ltd. All rights reserved.
Introduction
Erection of main cables is an essential step for construction of a long-span suspension bridge. During the construction phases, the stiffening girder has not been erected and main cables are suspended on bridge towers independently of other structures. As a result, the rigidity of a main cable is very small, and the cable will be sensitive to wind excitations. Large-amplitude wind-induced vibration of main cables has been observed during the construction phases of the 1650 m
lowast; Corresponding author.
E-mail address: cexghua@hnu.edu.cn (X.G. Hua).
https://doi.org/10.1016/j.jfluidstructs.2019.102846 0889-9746/copy; 2019 Elsevier Ltd. All rights reserved.
Fig. 1. Main cable during construction.
(main span) Xihoumen Bridge (Li and Ou, 2010; An et al., 2016) and the 1480 m (main span) Second Dongting Lake Bridge in China, and the safety of structures as well as the construction workers were seriously threatened.
Generally, the main cable of long-span suspension bridges consists of more than one hundred identical steel strands, and the steel strands are installed one by one (Fig. 1). Consequently, the main cable may experience a number of cross- sectional shapes during construction phases, and its aerodynamic performance can be foreseen to very complex. Main cables during construction may suffer vortex-induced vibration, turbulence-induced buffeting and galloping in wind flow. A certain amount of fundamental work relating to the wind-induced vibration of main cables during construction has been published. Galloping, as the primary source of wind-induced vibrations for main cables, is a kind of aerodynamic instability, and has a strong destructive power on account of the possible divergent amplitude. When a main cable shows a special cross-sectional shape at a certain construction stage, it will have a risk of galloping, and large-amplitude oscillation will occur when the wind velocity reaches a critical value (Li et al., 2017). Both wind tunnel test and numerical simulation have been conducted to study the aerodynamic performance of main cables. Results based on the Den Hartog criterion (Den Hartog, 1932) indicate that galloping may occur on main cables not only erected by the common steepled method (An et al., 2016), but also by the flat-topped method (Li et al., 2017).
Results of previous research provide an academic reference of wind resistance for main cable construction, since several typical cross sections of main cable have bee
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