An official website of the United States government
Buffeting analysis plays an important role in the wind-resistant design of long-span bridges. While computational methods have been widely used in the study of self-excited forces on bridge sections, there is very little work on applying advanced simulation to buffeting analysis. In an effort to address this shortcoming, we developed a framework for the buffeting simulation of bridge sections subjected to turbulent flows. We carry out simulations of a rectangular bridge section with aspect ratio 10 and compute its aerodynamic admittance functions. The simulations show good agreement with airfoil theory and experimental observations. It was found that inflow turbulence plays an important role in obtaining accurate wind loads on the bridge sections. The proposed methodology is envisioned to have practical impact in wind engineering of structures in the future.
more »
« less
This content will become publicly available on August 1, 2026
Reliability analysis and parametric studies of the buffeting performance of long-span bridges under multiple sets of random variables
Buffeting-induced accelerations and displacements of bridge deck girders commonly drive the bridge design’s comfort, operational, and strength limit states. The scattered nature of the main wind characteristics and bridge responses recorded in multiple monitoring campaigns make deterministic approaches insufficient to assess the bridge’s performance along its life span. This study reports comprehensive sensitivity and reliability studies conducted to unveil the influence of multiple parameters controlling long-span bridges’ buffeting responses. The impact of several sets of random variables on the reliability of the Great Belt Bridge is systematically studied. A detailed treatment of the uncertainty of flutter derivatives consisting of combining their frequency-dependent random definition with their experimentally defined correlation is proposed. Results show the drastic impact of uncertainty in the flutter derivatives, the vertical turbulence intensity, the mean wind velocity, and the definition of the buffeting loads, particularly the slopes of the force coefficients and the aerodynamic admittance, on the buffeting-induced accelerations. The influence of aerodynamic admittance on the results is analyzed in the context of random definitions of mean velocity, turbulent intensities, length scales, structural damping, and aerodynamic characteristics. The computational efficiency of gradient-based reliability methods is discussed, showing its potential to address high-dimensional problems within design frameworks.
more »
« less
- Award ID(s):
- 2503131
- PAR ID:
- 10593543
- Editor(s):
- Stathopoulos, T
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Wind Engineering and Industrial Aerodynamics
- Volume:
- 263
- Issue:
- C
- ISSN:
- 0167-6105
- Page Range / eLocation ID:
- 106112
- Subject(s) / Keyword(s):
- Buffeting Long-span bridges Reliability analysis Random variables Aerodynamic admittance Gradient-based reliability methods
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Wind-sensitive bridges are commonly designed based on their aeroelastic responses under synoptic winds. However, a holistic aero-structural design framework must address all potential wind scenarios along the bridge life cycle, including non-synoptic events and synoptic winds with relevant variations in the mean angle of attack due to wind-induced static deck deformation or complex terrain effects. This requires the evaluation of the aeroelastic responses considering the sensitivity of the fluid-structure interaction parameters to the wind angle of attack. Aiming at properly modeling these effects within design frameworks, this study proposes harnessing a multi-directional aeroelastic Kriging surrogate trained with forced vibration CFD simulations to emulate the flutter derivatives as a function of the deck shape, reduced velocity, and mean angle of attack. A bridge deck with a variable depth ranging from streamlined to bluff configurations is studied in detail, showing drastic changes in relevant flutter derivatives. The deck shape drives the impact of the mean angle of attack in some critical flutter derivatives, including the occurrence of A2* sign flipping, with its implications in the torsional stability. The resulting aeroelastic surrogate is conceived to be integrated into aero-structural optimization frameworks for optimally shaping bridge decks under synoptic and non-synoptic wind scenarios.more » « less
-
The shape design and optimization of bluff decks prone to aeroelastic phenomena require emulating the fluid-structure interaction parameters as a function of the body shape and the oscillation frequency. This is particularly relevant for long- and medium-span bridges equipped with single-box decks that are far from being considered streamlined and for other girder typologies such as traditional truss decks and modern twin- and multi-box decks. The success of aero-structural design frameworks, which are inherently iterative, relies on the efficient and accurate numerical evaluation of the wind-induced responses. This study proposes emulating the fluid-structure interaction parameters of bluff decks using surrogate modeling techniques to integrate them into aero-structural optimization frameworks. The surrogate is trained with data extracted from forced-vibration CFD simulations of a typical single-box girder to emulate the values of the flutter derivatives as a function of the deck shape and reduced velocity. The focus is on deck configurations ranging from streamlined to bluff cross-sections and on low reduced velocities to capture eventual aerodynamic nonlinearities. The girder cross-section geometry is tailored based on its buffeting performance. This design tool is fundamental to finding the optimum balance between the structural and aeroelastic requirements that drive the design of bluff deck bridges.more » « less
-
null (Ed.)Cables of suspension, cable-stayed and tied-arch bridges, suspended roofs, and power transmission lines are prone to moderate to large-amplitude vibrations in wind because of their low inherent damping. Structural or fatigue failure of a cable, due to these vibrations, pose a significant threat to the safety and serviceability of these structures. Over the past few decades, many studies have investigated the mechanisms that cause different types of flow-induced vibrations in cables such as rain-wind induced vibration (RWIV), vortex-induced vibration (VIV), iced cable galloping, wake galloping, and dry-cable galloping that have resulted in an improved understanding of the cause of these vibrations. In this study, the parameters governing the turbulence-induced (buffeting) and motion-induced wind loads (self-excited) for inclined and yawed dry cables have been identified. These parameters facilitate the prediction of their response in turbulent wind and estimate the incipient condition for onset of dry-cable galloping. Wind tunnel experiments were performed to measure the parameters governing the aerodynamic and aeroelastic forces on a yawed dry cable. This study mainly focuses on the prediction of critical reduced velocity 〖(RV〗_cr) as a function of equivalent yaw angle (*) and Scruton number (Sc) through measurement of aerodynamic- damping and stiffness. Wind tunnel tests using a section model of a smooth cable were performed under uniform and smooth/gusty flow conditions in the AABL Wind and Gust Tunnel located at Iowa State University. Static model tests for equivalent yaw angles of 0º to 45º indicate that the mean drag coefficient 〖(C〗_D) and Strouhal number (St) of a yawed cable decreases with the yaw angle, while the mean lift coefficient 〖(C〗_L) remains zero in the subcritical Reynolds number (Re) regime. Dynamic one degree-of-freedom model tests in across-wind and along-wind directions resulted in the identification of buffeting indicial derivative functions and flutter derivatives of a yawed cable for a range of equivalent yaw angles. Empirical equations for mean drag coefficient, Strouhal number, buffeting indicial derivative functions and critical reduced velocity for dry-cable galloping are proposed for yawed cables. The results indicate a critical equivalent yaw angle of 45° for dry-cable galloping. A simplified design procedure is introduced to estimate the minimum damping required to arrest dry-cable galloping from occurring below the design wind speed of the cable structure. Furthermore, the results from this study can be applied to predict the wind load and response of a dry cable at a specified wind speed for a given yaw angle.more » « less
-
Contemporary aero-structural design frameworks for wind-sensitive bridges are mostly based on the assessment of aeroelastic responses under synoptic winds. However, holistic design methodologies must address all potential wind scenarios, such as non-synoptic wind events and variations in the angle of attack due to complex terrains. This requires the evaluation of the aeroelastic responses considering the sensitivity of the fluid-structure interaction parameters with the angle of attack. Hence, this study proposes a Kriging-based multi-directional aeroelastic surrogate to emulate the flutter derivatives of bridge decks as a function of the deck shape, frequency of oscillation of the deck, and the mean incident angles of wind. This design tool is pivotal to properly modeling the nonlinear features of flutter derivatives at low reduced velocities and their sensitivity with the angle of attack. The aeroelastic surrogate will be later integrated into aero-structural design frameworks for the shape optimization of bridge decks under non-stationary winds.more » « less
