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As the number of long-span bridges continues to grow, wind-induced vibration issues have become increasingly intensified. Among them, flutter is a serious wind-induced vibration that can lead to bridge collapse. To address this problem, this paper proposes inerter-based dampers as a solution for flutter control and compares their performance to traditional tuned mass dampers (TMDs). Firstly, eight distinct inerter-based dampers were proposed, based on various combinations of mass-inerter-spring-damper (MISD) components. Secondly, the equations of motion of the bridge-MISD system were derived based on the two-mode coupled flutter theory and the mechanical impedance analysis method. Thirdly, the flutter control performance of the eight proposed MISDs is examined using a simply supported beam, with the six better-performing dampers further evaluated using the Jiangyin Bridge. The results show that inerter-based dampers can effectively improve the critical flutter wind speed of bridges, with performance sensitive to frequency. Additionally, incorporating an inerter decreases the static displacement of the mass block, while increasing the mass of MISD and the distance between the damper and the section center improves flutter control performance. The optimal spring stiffness ratios for the six MISDs are identified, largely dependent on the damper's inertance and mass. In conclusion, this paper offers a promising solution to addressing flutter in long-span bridges and provides insights into the design and optimization of inerter-based dampers. [ABSTRACT FROM AUTHOR]

In the complex mountain wind environment, especially in the strong wind, fluctuating wind speed is a non-stationary and non-Gaussian random process. With the increase of suspension bridges' span, they are more sensitive to wind-induced vibration response. In this paper, a non-stationary and non-Gaussian buffeting reliability analysis method for long-span bridges is presented. Firstly, the non-stationary wind speed is simulated by the modulation function based on the stationary wind speed model. Secondly, the load is obtained by simulated wind speed, the obtained loads are loaded on the finite element model by ANSYS and the whole bridge time-domain analysis is performed, the time history of displacement response is obtained. Thirdly, based on the first excursion failure criterion of random vibration, the samples of the non-stationary and non-Gaussian displacement time history are transformed into a standard Gaussian process through a modified Fleishman approximation method, and then the non-stationary Poisson distribution method is used for structural reliability analysis. Finally, a mountainous long-span suspension bridge is used as the engineering background, and the proposed reliability analysis method is applied to analyze the reliability of the bridge. The influence of different wind attack angles and modulation functions on the dynamic reliability of the bridge is further studied. The results indicate that the displacement response obtained by the transformation of non-stationary and non-Gaussian random process is less reliable than that obtained by traditional analysis method. Its dynamic reliability is maximum at 1 ∘ wind attack angle, the reliability of negative wind attack angle is lower than that of positive wind attack angle, and decreases with the increase of wind attack angle. The reliability obtained by using different modulation functions is lower than that of traditional method. If the traditional analysis method is still used for reliability analysis, it will produce unsafe consequences and reduce the engineering safety reserve. [ABSTRACT FROM AUTHOR]

• The dynamic model of long-span arch bridges conducted by the cantilever construction method is established. • The proposed method has excellent applicability for planner-free vibration of long-span arch bridges during construction. • The vibration of towers cannot be neglected unless it is sufficiently stiff. • The proposed model and method can be extended to the other multi-cable supported arch structures. The cantilever construction model, which consists of the arch, towers and cables, can be regarded as a cable-stayed system and is widely applied in constructing long-span arch bridges. The vibration induced by this temporary structure's unstable property has a safety risk and deserves to be concerned. Thus, a fully analytical beam-spring-arch model is presented for the cantilever and closure construction states of long-span arch bridges. Subsequently, based on the boundary and continuity conditions, the governing differential equations for in-plane free vibration are derived according to the Hamilton principle and solved using the transfer matrix method to determine frequencies and mode shapes of the system. Meanwhile, the results calculated by the proposed method are verified with the finite element method. Finally, the effects of structural parameter variations during construction on in-plane vibration properties are investigated. The results show that as the length of the erected arch rib gets longer, the system's first six-order frequencies and mode shapes are significantly affected. Moreover, the veering phenomenon is observed. The cables can increase the frequencies of the system to a certain extent. The model that neglects the tower's vibration would overestimate the stiffness of the erection system unless the tower's stiffness is much bigger than the arch. [ABSTRACT FROM AUTHOR]

Although long-span suspension bridges play a vital role in the transportation infrastructure, their resistance to disproportionate collapse resulting from locally induced damage has not yet been adequately investigated. In this study, computational simulation is used to shed light on how a prototype long-span suspension bridge responds to sudden loss of suspenders. Several scenarios were considered, with a focus on the total number of suspenders lost, their locations, and mode of removal. An increasing number of suspenders were removed either sequentially (i.e., one at a time) or simultaneously (i.e., multiple suspenders removed at the same time) until progressive collapse of the bridge was triggered. The simulation results showed that the bridge exhibited increasing levels of damage as the number of removed suspenders increased, and that the most critical location for suspender removal was near the middle of the bridge. It is shown that the sequential loss of a group of suspenders led to bridge responses that are almost identical with the simultaneous loss of the same group of suspenders. It is also argued that suspension bridges like the prototype system under consideration are highly robust. [ABSTRACT FROM AUTHOR]

Long-span concrete-filled steel tubular (CFST) hybrid arch bridge is one of the optimal solutions for large-span bridge construction, where the construction process and long-term sustained loading may affect the structural performance during its life-cycle. The trussed CFST hybrid arch of the Pingnan Third Bridge in China with a main span of 575 m was taken as a benchmark case to numerically determine the life-cycle based structural performance of long-span CFST hybrid arch bridge, and the construction process and long-term service period were considered. The accuracy of the numerical method was validated with the in-situ measured records of the real bridge and a series of available laboratory tests. Thereafter, the life-cycle based working mechanism of the trussed CFST hybrid arch was investigated. Parametric investigations were also carried out to evaluate the influence of key parameters on the load-bearing capacity of the hybrid arch structure. Furthermore, the resistance of the structure was examined using GB/T 51446–2021. It is shown that the simulated results agree well with the in-situ measured and experimental data. The stress redistribution exists in the CFST chord during construction and long-term service phases. The influence of CFST chords is significant to the load-bearing capacity of hybrid arch as the core concrete plays a prominent role, while the effects of the web (brace) strength and web (brace) - to - chord diameter ratio are limited. It is recommended to use GB/T 51446–2021 for resistance prediction of the long-span CFST hybrid arch bridge. • Life-cycle based structural performance of the long-span arch bridge was clarified. • Working mechanism of the trussed CFST hybrid arch was revealed. • Key factors affecting the load-bearing capacity of the structure were identified. • Resistance verification of long-span CFST hybrid arch bridge was conducted using national standard GB/T 51446–2021. [ABSTRACT FROM AUTHOR]

Porous safety fences are increasingly being incorporated into the deck furniture at or near the edges of many long-span bridges, and these tall fences (often 3-4 m high) may become blocked during winter storms. The accretion of ice or snow on these fences decreases the porosity and significantly impacts the air flow around the bridge. Due to the relatively low probability of concurring extreme wind and extreme snow/ice events, a methodology is developed and presented to assess the probability of failure due to flutter in these events using wind tunnel test results. Analysis of these test results also indicates that responses due to vortex-induced oscillation may amplify as the fences become increasingly blocked by snow or ice. Similar trends were observed for both single and parallel bridge configurations, suggesting the need for careful studies focused on these effects for bridges in climatic regions susceptible to snow and ice. The effects of snow and ice accretion on fences are also analyzed in the context of design wind loads; results suggest that the primary concern for these effects is the aerodynamic stability of the bridges rather than the increases in wind loading. [ABSTRACT FROM AUTHOR]

• Probabilistic vortex-induced vibration (VIV) occurrence prediction based on wind tunnel tests. • Prediction of the vortex-induced vibration occurrence using decision tree method. • Considering the effects of structural damping ratio, wind direction and wind speed. • Probabilistic cost-benefit analysis from Aerodynamic countermeasures (ACMs) application. The twin-box girder is a recommendable structural style for long-span cable-supported bridges due to its excellent aeroelastic stability. Vortex-induced vibration (VIV) is a typical wind-induced vibration for this kind of girder with a high occurrence probability associated with wind characteristics, structural properties and aerodynamic configuration under uncertainty. Therefore, probabilistic approaches should be adopted to predict the occurrence of VIV under uncertainty. This paper presents such an approach to predict the VIV occurrence using the decision tree method. Wind tunnel tests on a large-scale section model are conducted to investigate the effects of structural damping ratio and wind speed on VIV performance. Uniform and turbulent wind flow fields under three attack angles of −3°, 0°, and −3° are tested. Moreover, wind direction at the bridge site is determined as a parameter affecting VIV occurrence. As a result, a decision tree considering the effects of structural damping ratio, wind direction and wind speed is formulated to estimate the probability of VIV occurrence. In order to suppress VIV, aerodynamic countermeasures (ACMs) with L-shaped windshields are applied. Furthermore, the probabilistic cost-benefit analysis of the application of ACMs is developed using a decision tree, and the probability of the positive cost-benefit from ACMs application is accordingly estimated. The application of the proposed probabilistic approach is investigated on a long-span cable-stayed bridge with two separated steel boxes. [ABSTRACT FROM AUTHOR]

• A novel aerostatic stability analysis method using a modal formulation is presented. • Convergence to the critical wind velocity is accelerated through a root-finding algorithm in the outer loop. • The proposed method is applied to a cable-stayed bridge considering multiple nonlinear features. • The collapse is driven by stiffness degradation due to stays loss of tension and ultimately stiffness. • The influence of aerodynamic and structural nonlinear features on the critical wind velocity is investigated. An efficient method for analyzing the nonlinear aerostatic stability of long-span bridges using a modal formulation is proposed. First, a simplified linear version defined as modal-based approach is introduced, which evaluates the bridge displacements using the modal properties of the bridge and speeds up the assessment of the critical velocity by applying a root-finding algorithm. Then, this scheme is further developed to identify the instability limit point in nonlinear structures by combining nonlinear FEM analyses with the linear version of the modal-based approach and a root-finding algorithm in an outer loop. The effects of considering the three components of the wind loads, the stays sag effect, structural nonlinearities, aerodynamic nonlinearities, and the initial wind angle of attack, are analyzed and discussed. The computational advantages of the proposed method and its accuracy are demonstrated through three application examples, including a simplified linear 1 DoF system, and linear and nonlinear FEM models of a full cable-stayed bridge. The collapse mechanism of the cable-stayed bridge is driven by the stiffness degradation of the stays caused by the deck vertical upward displacements. It has been found that the influence of the nonlinear aerodynamic features is very low when the structural nonlinearities control the bridge collapse. [ABSTRACT FROM AUTHOR]

Two vortex-induced vibration (VIV) events of the main girder of long-span bridges successively happened on the Yingwuzhou suspension bridge and Humen suspension bridge in China, 2020, and drew public attention. Especially for the Humen suspension bridge, the amplitude of VIV was so notable that the traffic was closed for 10 days. Generally, VIV is sensitive to the structural and ambient issues and large-amplitude VIV is unacceptable for engineering structures as it could result in potential fatigue failure of some key joint components. Therefore, it is of great significance to explore the excitation mechanism of VIV and develop effective methods to mitigate excessive vibration of main-girders. From the perspective of vortex dynamics, we present a selective review of recent progress on the mechanism of VIV occurred in long-span bridges and aerodynamic countermeasures to attenuate the VIV amplitude. Notwithstanding the VIV mechanism of girders has not been thoroughly clarified, it is generally accepted that VIV rises from the unsteady vortex shedding from the main girder. Besides, the flow control methods, which are proposed to manipulate the surrounding flow patterns around the girder, are also focused in this review. Some perspectives are finally presented for future studies in fluid–structure interaction and aerodynamic vibration mitigation of long-span bridges. [ABSTRACT FROM AUTHOR]