Statistical Approaches to Climate-Resilient Wind Design

Abstract

Design wind speeds under ASCE 7 standards determine the resiliency of buildings across the United States. Previous studies indicate that these design speeds must increase to account for climate change and its impact on tropical cyclones, which generate extreme winds along the Atlantic and Gulf coasts. However, climate-resilient wind speeds can differ depending on if they account for the worst year of risk (the MRI method) or the total lifetime risk (the LEP method) of a structure. This study first verifies the results of previous literature with new tropical cyclone modeling techniques under the SSP5-8.5 climate, then compares the two methods of determining design winds with a new proposed standard: the LEP-AEP method. Risk under the three methods is quantified by calculating the actual lifetime exceedance probabilities, time until the annual exceedance threshold is crossed, and the maximum annual risk over a building’s lifetime. This study culminates in a proposed procedure for determining the design wind speed for a specific location and building type, which can be utilized by structural engineers in a website tool. This study verifies the Emanuel et al. (2006; 2008) approach for modeling tropical cyclones with the PepC model, which results in storm frequencies that do not change linearly over time, requiring further research into interannual variability in the climate. For mid-latitude locations and skyscrapers, it is recommended that structural engineers use a more conservative approach when selecting a non-stationary design wind speed, like the MRI standard. This is due to uncertainties in the models for mid-latitudes and serviceability concerns in tall buildings. The models tend to overestimate extreme winds in inland locations, making the LEP standard a better tool because it is the least conservative method. Buildings in coastal counties with lifespans of 100 years or more and high risk categories tend to have high annual exceedance probabilities near the end of their lifetimes, making their design wind speeds differ by as much as 87 m/s depending on the standard selected. This study finds that the LEP-AEP method is best for these building types because it compromises between high-risk and overly-conservative design. Additionally, maintenance checks should be scheduled depending on the year at which the annual exceedance threshold is first surpassed, which is near 60% of the building’s lifetime in coastal locations. Due to the significant increases in stationary design wind speeds under all of these methods, it is recommended that the website tool and procedure suggested here be implemented as soon as possible to ensure that structures along the U.S. Atlantic and Gulf coasts are resilient to climate change.