Design Wind Speeds for the Caribbean for use with the Wind Load Provisions of ASCE 7 Prepared by Peter J Vickery and Dhiraj Wadhera Applied Research Associates 854 Colonnade Center Drive, Suite 37 Raleigh, NC 27615 Under a special grant from the Office of Foreign Disaster Assistance of the United States Agency for International Development (OFDA/USAID).
Overview Simulation Methodology B and RMW models Sea Surface Drag Coefficient Model Hurricane Boundary Layer Model Model Validation Design Wind Speeds Summary
Simulation Approach and Flow Chart 25 Peak gust Wind Speed (mph) 2 15 1 5 1 1 1 1 1 Return Period (years)
Holland B Parameter 2.5 2. 1.5 1..5. Gradient Balance Wind Speed Holland B Parameter y = -2.237x + 1.732 R 2 =.336.5.1.15.2.25.3.35.4 (ms -1 ) 6 5 4 3 2 1 SQRT(A) B =.75 B = 1 B = 1.3 B = 1.5 1 2 3 4 5 6 7 8 9 1 Distance from Storm Center (r/rmw) B estimates derived from upper level flight data and H*Wind snapshots of hurricane wind fields. B modeled as a function of A where A = R d is the gas constant for dry air, p c is the central pressure, Ts is the sea surface temperature ( C), Δp is central pressure difference, RMW is radius to maximum winds RMW f c Δp 2R T + d s ln 1 pc e Vickery and Wadhera (28), Statistical Models of Holland Pressure Profile Parameter and Radius to Maximum Winds of Hurricanes from Flight Level Pressure and H*Wind data In Press JAMC
RMW Models Atlantic Region 5 2 ln( RMW ) = 3.15 6.291 1 Δp +.337Ψ + ε r 2 =.297,σ lnrmw =.441 Δp is central pressure difference, Ψ is the latitude and ε is the random error term. The error, σ lnrmw, is modeled in the form: σ lnrmw =.448 σ lnrmw = 1.137.792Δp σ lnrmw =.186 Δp 87 hpa 87 hpa Δp 12 hpa Δp >12 hpa Radius to Maximum Winds (km) 15 125 1 75 5 25 Data Model Median +/- 2 Standard Deviations 3 4 5 6 7 8 9 1 11 12 13 Central Pressure Difference (hpa)
Hurricane Boundary Layer Model Boundary Layer Model developed using Dropwindsonde data. 1 9 RMW -3 km Includes the radial variation of BL height Marine Boundary Layer Model given by: u * z z U ( z) = ln( ) a( ) * k zo H Boundary layer Height given by: * 2 H = 343.7 +.26 / I r =.75, σ e = 99m Vickery et al (28), A Hurricane Boundary Layer and Wind Field Model for Use in Engineering Applications, In Press JAMC n Height (m) 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 Mean Wind Speed (m/sec)
Drag Coefficient over the Ocean Powell, 198 Powell, et al, 23 C d open terrain =.471
Sea Surface Drag Coefficient Model Drag Coefficient.7.6.5.4.3.2 RMW 1-3 km, LSF over 2 m - 1 m RMW 1-3 km, LSF over 2 m - 15 m RMW 1-3 km, LSF over 2 m - 2 m Large and Pond (1981) with.19 maximum Drag Coefficient.7.6.5.4.3.2 RMW 3-6 km, LSF over 2 m - 1 m RMW 3-6 km, LSF over 2 m - 15 m RMW 3-6 km, LSF over 2 m - 2 m Large and Pond (1981) with.22 maximum.1.1 1 2 3 4 5 6 Mean Wind Speed at 1m (m/sec). 1 2 3 4 5 6 Mean Wind Speed at 1m (m/sec) Drag Coefficient.7.6.5.4.3.2 RMW 6-1 km, LSF over 2 m - 1 m RMW 6-1 km, LSF over 2 m - 15 m RMW 6-1 km, LSF over 2 m - 2 m Large and Pond (1981) with.25 maximum Drag Coefficient.7.6.5.4.3.2 All RMW - LSF over 2 m - 2 m All RMW - LSF over 2 m - 15 m All RMW - LSF over 2 m - 1 m Large and Pond (1981) with blended maximum.1.1 1 2 3 4 5 6 Mean Wind Speed at 1m (m/sec) 1 2 3 4 5 6 Mean Wind Speed at 1m (m/sec)
Wind Field Model Validation Modeled Peak Gust Wind Speed (mph) 14 12 1 8 6 4 2 All Hurricanes - Land y =.991x Modeled Peak Gust Wind Speed (mph) 14 12 1 8 6 4 2 All Hurricanes - Marine y =.994x 2 4 6 8 1 12 14 2 4 6 8 1 12 14 Observed Peak Gust Wind Speed (mph) Observed Peak Gust Wind Speed (mph) Modeled Peak Gust Wind Speed (mph) 14 12 1 8 6 4 2 All Hurricane - Land and Marine y=.993x 2 4 6 8 1 12 14 Observed Peak Gust Wind Speed (mph)
Modeled and Observed Heading, Translation Speed and Central Pressure
Modeled and Observed Heading, Translation Speed and Central Pressure
Number of Hurricanes with central pressure values 15 Location - 12N & 61W 15 N (All hurricanes) Location - 16N & 65W Number of hurricanes within 25 km of the site 1 5 Np (Hurricanes with Central Pressure values) Number of hurricanes within 25 km of the site 1 5 19 1915 193 1945 196 1975 199 25 Year 19 1915 193 1945 196 1975 199 25 Year 15 Location - 18N & 75W 15 Location - 2N & 85W Number of hurricanes within 25 km of the site 1 5 Number of hurricanes within 25 km of the site 1 5 19 1915 193 1945 196 1975 199 25 Year 19 1915 193 1945 196 1975 199 25 Year
Comparison of observed and Modeled Central Pressures Observed minimum central pressure within 25 km of a location Minimum 5 year modeled central pressure within 25 km of a location
Comparison of 1 Year Modeled Wind Speeds with Values from Georgiou (1986) Wind Speeds are representative of 1-3 minute mean values over marine exposure
Comparison of 1 Year Modeled Wind Speeds with CUBiC Location This Study (ms -1 ) CUBiC (ms -1 ) Trinidad (S) 14.3 29.6 Trinidad (N) 38. 38. Grenada 47.8 47.1 Barbados 5.1 51.2 Saint Vincent 49.6 52.4 Saint Lucia 53.2 53.2 Antigua and Barbuda 59.9 55.5 Montserrat 6.3 55.8 St. Kitts and Nevis 61.7 55.8 Dominica 55.4 56.2 Wind Speeds are representative of 2-3 sec gusts
Basic Non-Wind Speed Definition from ASCE 7 1.8 1.6 1.4 W LF I = 1.6 1.15 = 1.352 1.2 W LF = 1.6 = 1.263 VRP/V5 1.8.6.4.2 5 7 17 1 1 1 1 1 Return Period (years)
Basic Wind Speed Definition from ASCE7 2.5 Jamaica 2 1.73 VRP/V5 1.5 1 1.58.5 5 7 17 1 1 1 1 1.2 1 = 1.6 = 1.263 Return Period (years) VRP/V5 1.8 1.6 1.4 1.8.6 W LF W LF I = 1.6 1.15 = 1.352.4.2 5 7 17 1 1 1 1 1 Return Period (years)
5 Year Wind Speeds for Caribbean 13 12 12 12 11 12 13 11 12 1 9 8 7 11 1 9 6 13 5 4 12 13 3 1 9 Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
7 Year Wind Speeds for Caribbean 18 17 18 17 16 16 16 17 15 14 13 12 11 1 9 19 17 13 14 15 16 8 7 15 14 13 12 Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
1 Year Wind Speeds for Caribbean 13 14 14 13 14 13 13 12 13 11 12 11 1 9 8 7 15 1 12 6 14 15 14 5 12 4 3 11 1 3 Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
17 Year Wind Speeds for Caribbean 19 19 18 17 17 18 17 18 17 16 15 14 13 12 11 1 2 15 19 17 16 9 8 16 15 14 Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
5, 1, 7 and 17 Year Wind Speeds for Cuba Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
5, 1, 7 and 17 Year Wind Speeds for Jamaica Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
5, 1, 7 and 17 Year Wind Speeds for Hispaniola Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
5, 1, 7 and 17 Year Wind Speeds for Puerto Rico Wind speeds are 3 sec gusts at a height of 1m in flat open terrain
2 2 2.75 3.25 4 3.5 3.75 4.25 4.5 4.75 5 5.25 5 7 8 6.5 9 6 1.75 2.5 5.75 1.75 2.25 2.75 5.75 1.75 2.5 6.5 Load Factor (V ( 7 /V 5 ) 2 1.75 2 2 2 3.25 2 2.75 3.25 2.25 2.25 3 4 4.5 4.25 5.25 6 4.75 5 5.25 6 3.75 5.5 3.5 5.5 6.25 6
Summary A hurricane simulation method is used to estimate design wind speeds for the Caribbean region. Wind speed maps for return periods of 5, 1, 7 and 17 year have been developed. The model has been validated through comparisons to the historical observations of central pressure difference, storm heading, translation speed and minimum distance of approach. 7 year and 17 year return period wind speeds are given as design wind speeds for category 2 and Category 3 & 4 structures respectively (with wind load factor=1) Provides design wind speeds for the Caribbean that can be used with ASCE 7 wind provisions
This presentation has been made possible through the financial support of the Division of Humanitarian Assistance, Peace and Security of the Canadian International Development Agency (HAPS/CIDA) and the Office of Foreign Disaster Assistance of the United States Agency for International Development (OFDA/USAID).