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In the design of modern long-span bridges, inhomogeneous cross sections are increasingly used to meet various requirements, posing challenges in the investigation of vortex-induced vibration (VIV). This paper introduces a nonlinear approach with a focus on amplitude dependency in VIV for inhomogeneous bridges. It presents an inhomogeneous vortex-induced force model with amplitude-dependent parameters to capture spanwise variations in aerodynamics. These parameters are identified through multiple sectional wind tunnel tests. VIV amplitudes are determined by searching for solutions under the zero-damping condition for VIV. An illustrative bridge with an inhomogeneous fairing design is employed as an engineering application. The approach is rigorously validated with experimental data and applied to assess the prototype VIV behavior of the bridge with different fairing lengths. An optimal fairing length, constituting 40% of the main girder length in the mid-span, is identified to strike a balance between VIV performance and material usage. Discussion for the prediction results provides insights into the effects of fairing length inhomogeneity on VIV. In practice, deploying fairings in the large mode shape sections of the main girder achieves VIV mitigation comparable to a full-span installation. [ABSTRACT FROM AUTHOR]

A single-level rail-cum-road bridge is a relatively new type of bridge structure that accommodates both roadway and railway traffic on the same level. The aerodynamic interactions between road vehicles, trains, and the bridge deck under strong crosswind are significant, potentially posing safety risks to both vehicles and trains. This study aims to elucidate the aerodynamic interference between a road vehicle and a train during meeting on a single-level rail-cum-road bridge under crosswind. To achieve this, a three-dimensional, incompressible, unsteady Reynolds averaged Navier–Stokes method is utilized to simulate the meeting process between a van and a train on a prototype single-level rail-cum-road bridge under crosswind. Using an established computational fluid dynamics numerical model, the flow structure and aerodynamic loads of the van–train–bridge system under crosswind are studied. The results show that the auxiliary facilities on the bridge deck (such as pedestrian guardrails and anti-glare barriers) significantly alter the flow field around the van and train, affecting their aerodynamic characteristics. Additionally, the aerodynamic interference between the van and the train during their meeting under crosswind is substantial. The aerodynamic coefficients of the van and train, in terms of both magnitude and fluctuation, increase significantly with their driving speeds during the meeting process under crosswind. Furthermore, this aerodynamic interference intensifies as the lateral distance between the van and the train decreases during the meeting under crosswind. [ABSTRACT FROM AUTHOR]

Bottom-mounted slender structures are often flexible enough to induce hydroelastic effect which could change their dynamic properties and affects the resultant response. This study presents a frequency-domain approach to characterise the hydroelastic response as well as wet dynamic characteristics for offshore bottom-mounted structure with arbitrary geometry. The boundary element method associated with Euler-Bernoulli theory is integrated and coupled. The approaches for wet fundamental period, wet damping ratio and hydroelastic response are validated against a benchmark experiment. Results show that surrounding water has obvious influence on the structural period and damping ratio, particularly on damping ratio. The distribution of added mass grows quickly with depth to about z/d = 0.2 and then gradually decreases whereas added damping mainly concentrates near free surface and drops rapidly with depth. If hydroelastic effect is not considered, it could cause considerable frequency-to-frequency errors from −26% to 52% in responses. [ABSTRACT FROM AUTHOR]

The assessment of wave conditions is a primary task for the design, construction, and structural analysis of sea-crossing bridge. This article presents a numerical simulation and a field measurement to study the wave conditions in the nearshore island area for sea-crossing bridges. Pingtan Strait sea-crossing bridge site was selected as an example of nearshore island area. A 3-day high-energy wave event was measured and simulated using spectral wave model. The parameters of the numerical model were calibrated through the comparison with the field measured wave data. The spatial pattern of wave conditions along the bridge and the wave-breaking zone were analyzed based on the calibrated model. The analytical procedures suggested in the Chinese Code for nearshore wave prediction were finally testified through the comparison with numerical results. The research showed that (1) spectral wave model predicts the wave conditions in bridge site reasonably; (2) seabed terrain and islands significantly influence wave conditions, wave spatial pattern, and breaking wave zones; and (3) analytical wave simulation procedure recommended in the Code is not suitable to island area for sea-crossing bridge. This research allows a better understanding of wave conditions for sea-crossing bridge site and could provide useful reference for engineering practice. [ABSTRACT FROM AUTHOR]