Leveraging our experience on hundreds of long-span, flexible, and unique bridges, the BLWTL provides critical aerodynamic insight and guidance, ensuring the development of a safe, efficient, and economical structure.
The BLWTL provides decades of specialized expertise, offering clients proven analysis across all major bridge types, including suspension, cable-stayed, and pedestrian structures, ensuring comprehensive project insight.
We deliver highly accurate, wind-induced load and response estimates for your bridge. Our testing programs integrate the unique geometry, structural dynamics, and project-specific climatic conditions to ensure the reliability of the structural design.
Our flexible test programs enable investigation of a bridge throughout its entire lifecycle, including construction stages and abnormal service conditions like extreme traffic or heavy snow and ice buildup.
We offer preliminary evaluations in the earliest project stages to optimize design efficiency. We provide refined wind loads upfront, allowing them to be most easily and economically incorporated into the structural design.
Our wind tunnel testing programs are designed to assess key wind-induced bridge behaviour under real-world conditions. The objectives of these test programs are to evaluate the safety, stability, and serviceability of the bridge.
Key facets of the BLWTL’s wind tunnel testing and subsequent analyses include:
Aerodynamic Stability Assessment: We determine the critical wind speed limits for catastrophic phenomena like self-excited flutter or galloping (e.g., the 1940 Tacoma Narrows failure). We compare our results against site-specific wind speeds to confirm the long-term stability and safety of the bridge throughout its planned lifespan.
Design Wind Load Prediction: We predict precise wind loads based on the bridge’s geometry, structural properties, and site-specific climatic conditions. These loads, including the mean, background, and resonant forces, are synthesized into highly accurate Equivalent Static Loads (ESLs) for structural design. Our ESLs are more precise than standard design codes, minimizing design uncertainty and allowing for a more efficient and economical structure.
Vortex-Induced Oscillation (VIO) Assessment: We assess the structure’s susceptibility to harmonic cross-wind vibrations induced by wind vortices. VIO can occur at common, lower wind speeds and, while rarely critical for ultimate strength, can lead to fatigue damage and impact user comfort. We rigorously assess the possibility and magnitude of VIO for every structure.
Buffeting Response Prediction: We analyze the dynamic vibrations of the structure under the site-specific winds, predicting the magnitude of buffeting displacements and accelerations of the bridge elements. These predictions are key for ensuring the structure’s long-term serviceability and user comfort.
Mitigation Strategies: If a bridge design fails to meet aerodynamic criteria, we provide clear guidance and expertise to address the issues. Our mitigation strategies range from adjustments to the primary structural design to incorporating specific aerodynamic or mechanical solutions, such as installing wind fairings or damping systems.
Section Model Testing
Section model wind tunnel testing measures the aerodynamic properties of an idealized extruded 2D cross-section. This method is ideal for evaluation of bridge decks, as well as unique pylon and arch designs.
The section model is precisely designed and constructed to match the geometry and mass of the prototype at a smaller scale, typically in the range of 1:20 to 1:60.
The section model is mounted onto testing apparatus and tested under site-specific conditions in our state-of-the-art wind tunnel. We utilize a static testing rig to evaluate aerodynamic force coefficients and a tuned dynamic testing rig to accurately evaluate the structure’s aerodynamic responses.
The comprehensive results from this test program are used to inform the overall assessment of the structure and validate subsequent numerical analyses. Section model testing is suitable for most bridge projects.
Suspension Bridge and Resulting Deck Section Model
Aeroelastic Model Testing
For bridges of innovative design, exceptional size, or unusual siting, aeroelastic model wind tunnel testing serves as the final, most comprehensive confirmation of aerodynamic behavior. This technique uses a flexible, three-dimensional replica of the structure to accurately measure its performance under site-specific wind conditions.
Aeroelastic models are meticulously designed to match the geometry, stiffness, and mass of the entire bridge, including all relevant structural elements like decks, pylons, cables. These scale models (often 1:100 to 1:250) are typically built of machined aluminum spines with ballasted, 3D-printed cladding elements.
These models are tested in the wind tunnel in precisely replicated site conditions including upstream exposures, key topography, and existing structures. The heavily-instrumented model allowing for direct measurement of internal stresses, displacements, and accelerations, providing immediate measurement of the assessment criteria.
Due to the complexity of aeroelastic model testing, it is typically reserved for sensitive and complex structures, such as long-span bridges, as well as unique architectural designs which defy conventional section model testing.
Cable-Stayed Bridge and Resulting Aeroelastic Model
Miniature Section Model Testing
Miniature section model wind tunnel testing offers a rapid and economical method to refine wind load estimates on the proposed bridge in the early stages of the projects. The approximate ESLs developed from these tests include lift and overturning forces not typically captured by standard design code approaches.
The miniature section model is printed to precisely match the geometry of the prototype at a very small scale, typically in the range of 1:60 to 1:200 depending on the size of the bridge. The section model is mounted to a static force balance apparatus and tested under low turbulence flow conditions in our miniature wind tunnel to evaluate the aerodynamic force coefficients.
Miniature Deck Section Model
We assess the project site climate, considering local topography and historical wind measurements. We provide appropriate wind conditions for evaluation of the bridge.
We deploy advanced instrumentation on operational structures to measure real wind-driven responses and provide real-time data on long-term performance and structural integrity.
We numerically evaluate wind-induced cable oscillations (VIO, rain/wind vibration, dry/wake/iced galloping, external excitation). We provide recommended damping levels to control vibrations.
We estimate dynamic wind-induced displacements in the deck, pylon, or cables. We provide the magnitude and frequency of responses for structural fatigue assessments.
We perform wind tunnel testing of model vehicles on the bridge to assess critical overturning wind speeds. We recommend operational procedures such as speed reductions or bridge closure.
We advise on appropriate wind loads on secondary bridge components such as wind-on-live, barriers, light posts, and roadsigns.
Connect with the Boundary Layer Wind Tunnel Laboratory to discuss your bridge’s unique design and challenges.