Aerodynamics Laboratory Overview

The Aerodynamics Laboratory is used to study the complex interactions between wind and bridges or other highway structures, including design, stability, safety, and performance of highway structures under all combinations of geographical and meteorological wind conditions.

The primary purpose of the laboratory is to evaluate new designs, investigate performance problems of in-service structures, develop effective retrofit solutions, establish the aerodynamic properties of structures and structural components, support the development of new design guides and specifications, develop more effective experimental procedures and simulation methods and explore fundamental wind engineering problems.

Figure 1. Bridge deck model mounted in front of large wind tunnel.

The Aerodynamics Laboratory is the only wind tunnel facility in the United States that is dedicated solely to the study of wind effects on transportation structures. It has the longest continuous history of exploring bridge aerodynamics to ensure the performance and safety of long-span bridges in strong winds and to advance our understanding of wind effects on transportation structures.

The laboratory is federally owned and is staffed by a team of experienced scientists and engineers in the areas of structural engineering, aerodynamics, experimental methods, computational fluid dynamics, and wind engineering.

Figure 2. Setting up test to evaluate pressure-sensitive paint in the small-scale, closed-circuit wind tunnel.

Mission

To advance the state of the art in wind engineering, bridge engineering, and the complex interaction of wind and highway structures while contributing to the continuous development of a modern, technically advanced, and structurally safe transportation system.

History

The dramatic collapse of the Tacoma Narrows Bridge in 1940 sparked a major investigation into the effects of wind on suspension bridges. To coordinate the many activities that were to be undertaken, the Advisory Board on the Investigation of Suspension Bridges was formed. The Board was broadly representative of engineers responsible for specific suspension bridges, research engineers having competence in aerodynamics and suspension bridge theory, and representatives of industry with demonstrated ability and leadership in the fabrication and erection of suspension bridges.

The Bureau of Public Roads (later the Federal Highway Administration), embarked upon a broad research program that involved coordinating national and international wind investigations, sponsoring contract research, conducting laboratory and field studies in-house, and providing technical guidance through committees, panels, or research councils.

The Bureau made a careful survey of existing wind tunnel facilities in the United States to determine if one might be adapted for the purpose of studying the effects of wind forces on suspension bridges. The results of the study determined that it would be more cost effective and expeditious to build its own specialized facility. During the 1950s, the Aerodynamics Laboratory and wind tunnel were designed, constructed, and placed into service at the Turner-Fairbank Highway Research Center (TFHRC) in McLean, Virginia. The facilities, which have evolved from this research program, are unique in the Nation. The Aerodynamics Laboratory is the only wind tunnel specifically designed for and dedicated to ensuring the aerodynamic stability of transportation structures, especially long-span bridges. The wind tunnel, with its relatively large cross section, produces laminar flow and is very stable at low velocities. Its size and velocity range enable both static and dynamic investigations of large-scale section models of structures and structural components. The significance of structural details can be evaluated as well. A computer-driven turbulence simulation system is available to introduce properly scaled gusting into the air flow during testing. This system was the first of its kind in the world. To measure wind forces on sectional models, a high-frequency, dual force-balance system is available. Although other wind tunnels use high-frequency balances, the wind tunnel at TFHRC is unique because it is actually two matched balances in one system and can be used to directly measure unbalanced loads on the structural model.

To complement the research and development activities associated with wind tunnel experiments, the activities of the laboratory were expanded. Over the years, laboratory activity has grown to include more full-scale studies, with many bridges across the United States being instrumented and analyzed. In addition, in recent years, efforts have been under way to develop numerical and computational modeling of fluid and structural behavior interaction, in particular, as applied to long-span bridges.