TESTING AND ANALYSIS
MEASUREMENT LOCATIONS
Wind speed measurements were made at 22 selected locations to evaluate pedestrian comfort and safety around the project site. Mean (average) wind speed and turbulence intensity measurements were made at the model-scale equivalent of 5 to 7 ft above the surface for 16 wind directions in 22.5° increments from 0° (north). Wind speeds were measured with CPP 6-hole probes.
The measurement points were chosen to determine the degree of pedestrian comfort or discomfort at commonly frequented locations or locations of interest around the project site where the 651 Gateway project building may have effects on the wind environment. The test locations include locations where relatively severe conditions are frequently found, such as at building corners and on adjacent sidewalks with heavy pedestrian traffic. All the test locations are on the ground level.
WIND CLIMATE
The measured data were normalized to an approach reference wind speed and then combined with a climatological model (wind frequency and direction) derived from data measured at San Francisco International Airport. The climate data were adjusted to the site location using an analytical method to account for the exposure of the project site for each direction. The combination of the wind tunnel data and climatological data produces a cumulative probability distribution of wind speed for the site at each pedestrian measurement location. These results can then be compared to criteria for pedestrian wind comfort and safety.
INTERPRETATION OF RESULTS
The colored spheres presented in the viewer represent the locations that were studied. The color of the sphere and the halo represent the predicted pedestrian comfort and safety (respectively) with respect to the Lawson criteria .
The primary conclusions of the study can be understood by considering the colored ratings at each point, with the following color-coded ratings in mind:
Comfort (sphere color):
Red locations - mitigation designs are generally recommended
Orange and Yellow locations - mitigation may be needed based on intended use of the location
Green and Blue locations - mitigation is not generally required, with the possible exception of outdoor dining areas
Distress (halo color):
Black halo - location passes the distress criterion
Red halo - location fails the distress criterion
Note that the ratings of 'Uncomfortable' and 'Distress' are the words of the author (Lawson) and may not apply directly to any particular project. High wind areas are certainly not unacceptable all the time, just on windier days. The word uncomfortable, in our understanding, refers to acceptability of the site by pedestrians for typical pedestrian use; i.e., on the windiest days, pedestrians will not find the areas 'acceptable' for any kind of normal use, and will tend to avoid such areas if possible. Failure of the distress criterion, as we understand it, indicates some unspecified potential for causing injury to a less stable individual who might be blown over. The likelihood of such an event is not well described in the literature and is likely to be strongly affected by individual differences, presence of water, blowing dust or particulates, and other variables in addition to the wind speed.
All data collection was performed in accordance with the American Society of Civil Engineers (ASCE) Standard 7-16, the ASCE Manual of Practice Number 67 on Wind Tunnel Studies of Buildings and Structures (1999), and the ASCE Standard 49-12 on Wind Tunnel Testing of Buildings and Other Structures (2012).
REFERENCES
American Society of Civil Engineers (1999), Wind Tunnel Studies of Buildings and Structures (ASCE Manual of Practice Number 67).
American Society of Civil Engineers (2012), Wind Tunnel Testing for Buildings and Other Structures (ASCE 49-12).
American Society of Civil Engineers (2017), Minimum Design Loads for Buildings and Other Structures (ASCE 7-16).