Wind Tower Deployments and Pressure Sensor Installation on Coastal Houses Preliminary Data Summary _ Sea Grant Project No.:1020040317 Submitted to: South Carolina Sea Grant Consortium 287 Meeting Street Charleston, SC 29401 Prepared by: David O. Prevatt, Ph.D. Assistant Professor of Civil Engineering WLTF:01-2006 16 March 2006 Wind Load Test Facility Department of Civil Engineering Clemson University Lowry Hall Clemson, SC 29634-0911
TABLE OF CONTENTS LIST OF FIGURES... iii LIST OF TABLES... v ABSTRACT... vi 1. INTRODUCTION...1 2. METHODS...2 3. RESULTS...3 3.1 FULL-SCALE HOUSE DATA...4 3.2 WIND TOWER DEPLOYMENT...5 4. FUTURE WORK...5 5. ACKNOWLEDGEMENTS...6 ii
LIST OF FIGURES Figure 1. Tower deployed for data collection....6 Figure 2. Track of Hurricane Dennis and locations of FCMP houses and wind towers..8 Figure 3. Hurricane Dennis Aerial View Tower TO...9 Figure 4. Hurricane Dennis Aerial View Tower T1...9 Figure 5. Hurricane Dennis Aerial View Tower T2...9 Figure 6. Hurricane Dennis Aerial View Tower T3...10 Figure 7. Hurricane Dennis Aerial View Tower T5...10 Figure 8. Plot of Wind Speed and Direction Collected by T0 during Hurricane Dennis.11 Figure 9. Plot of Wind Speed and Direction Collected by T2 during Hurricane Dennis.11 Figure 10. Plot of Wind Speed and Direction Collected by T3 during Hurricane Dennis.12 Figure 11. Track of Hurricane Katrina and locations of FCMP houses and wind towers.13 Figure 12. Hurricane Katrina Aerial View Tower TO (first location)...14 Figure 13. Hurricane Katrina Aerial View Tower T0 (second location)...14 Figure 14. Hurricane Katrina Aerial View Tower T1...14 Figure 15. Hurricane Katrina Aerial View Tower T2...15 Figure 16. Hurricane Katrina Aerial View Tower T3...15 Figure 17. Hurricane Katrina Aerial View Tower T5...15 Figure 18. Plot of Wind Speed and Direction Collected by T1 during Hurricane Katrina.16 Figure 19. Plot of Wind Speed and Direction Collected by T2 during Hurricane Katrina.16 Figure 20. Plot of Wind Speed and Direction Collected by T3 during Hurricane Katrina.17 Figure 21. Track of Hurricane Rita and locations of FCMP houses and wind towers....18 Figure 22. Hurricane Rita Aerial View Tower TO...19 Figure 23. Hurricane Rita Aerial View Tower T1...19 Figure 24. Hurricane Rita Aerial View Tower T3...19 Figure 25. Hurricane Rita Aerial View Tower T5...20 Figure 26. Plot of Wind Speed and Direction Collected by T0 during Hurricane Rita....21 Figure 27. Plot of Wind Speed and Direction Collected by T1 during Hurricane Rita....21 Figure 28. Plot of Wind Speed and Direction Collected by T3 during Hurricane Rita....22 Figure 29. Plot of Wind Speed and Direction Collected by T5 during Hurricane Rita....22 Figure 30. Track of Hurricane Wilma and locations of FCMP houses and wind towers..23 Figure 31. Hurricane Wilma Aerial View Tower TO...24 Figure 32. Hurricane Wilma Aerial View Tower T1...24 Figure 33. Hurricane Wilma Aerial View Tower T2...24 Figure 34. Hurricane Wilma Aerial View Tower T3...25 Figure 35. Hurricane Wilma Aerial View Tower T5...25 Figure 36. Plot of Wind Speed and Direction Collected by T0 during Hurricane Wilma..26 Figure 37. Plot of Wind Speed and Direction Collected by T1 during Hurricane Wilma..26 Figure 38. Plot of Wind Speed and Direction Collected by T2 during Hurricane Wilma..27 Figure 39. Plot of Wind Speed and Direction Collected by T3 during Hurricane Wilma..27 Figure 40. FL-18 Dimension Drawing...Error! Bookmark not defined. Figure 41. FL-19 Dimension Drawing...Error! Bookmark not defined. Figure 42. FL-23 Dimension Drawing...Error! Bookmark not defined. Figure 43. FL-24 Dimension Drawing...Error! Bookmark not defined. Figure 44. FL-26 Dimension Drawing...Error! Bookmark not defined. Figure 45. East Elevation (front) of FL-18...33 Figure 46. North Elevation (side) of FL-18...33 Figure 47. South Elevation (side) of FL-18...33 iii
Figure 48. West Elevation (back) of FL-18...34 Figure 49. North Elevation (front) of FL-19...34 Figure 50. East Elevation (side) of FL-19...34 Figure 51. West Elevation (side) of FL-19...35 Figure 52. South Elevation (back) of FL-19...35 Figure 53. East Elevation (front) of FL-23...35 Figure 54. North Elevation (side) of FL-23...36 Figure 55. South Elevation (side) of FL-23...36 Figure 56. West Elevation (back) of FL-23...36 Figure 57. West Elevation (front) of FL-24...37 Figure 58. South Elevation (side) of FL-24...37 Figure 59. North Elevation (side) of FL-24...37 Figure 60. East Elevation (back) of FL-24...38 Figure 61. West Elevation (front) of FL-26...38 Figure 62. North Elevation (side) of FL-26...38 Figure 63. South Elevation (side) of FL-26...39 Figure 64. East Elevation (back) of FL-26...39 iv
LIST OF TABLES Table 1. House Identification and Location....7 Table 2. Summary of 2005 near real-time tower data collection....7 Table 3. Hurricane Dennis wind tower summary...8 Table 4. Hurricane Katrina wind tower summary...13 Table 5. Hurricane Rita wind tower summary...18 Table 6. Hurricane Dennis wind tower summary...23 Table 7. FL-18 Summary Plots for Hurricane Wilma....40 Table 8. FL-19 Summary Plots for Hurricane Wilma....43 Table 9. FL-23 Summary Plots for Hurricane Dennis...46 Table 10. FL-24 Summary Plots for Hurricane Dennis...49 Table 11. FL-26 Summary Plots for Hurricane Dennis...52 v
ABSTRACT Limited full-scale data is available on wind-induced loads on low-rise residential buildings. The lack of data from which to develop reliable wind design information may contribute in part to disproportionately high damage occurring to residential construction. This investigation was conducted to collect ephemeral data on wind speeds and wind pressures during land falling hurricanes. This report provides a summary of the raw data results collected during the 2005 hurricane season and it was funded in part by a seed/developmental grant awarded from the South Carolina Sea Grants Consortium. The included summaries represent the unprocessed data collected during Clemson University s ongoing field investigations and collaborative research of wind loads on coastal houses. Research is conducted in conjunction with Florida University and Florida International University in supporting research of the collaborative research project, the Florida Coastal Monitoring Program (FCMP). While the data collected will be instrumental to our increased knowledge and understanding of the wind load/structure interactions that occur during hurricanes, this report does not provide any significant analysis due to the limited scope of the work. Under a related Sea Grant Project titled, Comparing Field Measured Pressures with Wind Tunnel Models Studies of Single-Family Homes in Suburban Areas this data is being used to conduct wind tunnel studies of instrumented houses to further our knowledge of structural behaviors in extreme winds. Using 10 m (33 ft) tall wind towers and several pressure sensors installed on the roofs of five houses in residential neighborhoods, researchers collected wind velocity and wind pressure data in four hurricanes making landfall during 2005. The wind velocity data was posted to the World Wide Web in near real-time for the benefit of other researchers. The roof pressure data from the five houses are currently being analyzed by Clemson University and the University Florida. vi
1. INTRODUCTION Hurricanes remain one of the most costly natural hazards within the United States. Recent hurricane damage in 2005 from Hurricanes Katrina, Rita and Wilma continue to highlight the vulnerability of residential buildings in coastal areas. Damage from high winds disproportionately affects low-rise residential buildings located along vulnerable coastal areas of the Carolinas, Florida and Gulf States. The provision of reliable scientific information that relates damaging wind speeds with failure loads of building components is needed to evaluate the effectiveness of retrofit and existing structural design of houses and to validate current methodologies for boundary layer wind tunnel tests. The timely analysis of time-histories of wind speeds and wind-induced pressures on buildings are critical for post-storm engineering analyses of building damage. However, existing anemometers at regional airports typically do not provide the high-quality data on wind characteristics in a format that is useful to structural engineers and in many cases, these anemometers may be switched off prior to the storm. In addition, the flat, (open country) terrain around the airport anemometers are not representative of the rougher terrain suburban neighborhoods in which most homes are located. To address this shortfall, the Florida Coastal Monitoring Program, a program started in 1998, has conducted field measurements of hurricane wind velocities and wind-induced pressures on residential buildings. The FCMP is university research collaboration among Clemson University, Florida University, and Florida International University whose mission focus is to improve our understanding of the wind loads affecting houses in suburban areas during hurricanes. This field research uses several portable 10 m (33 ft) tall wind towers to measure hurricane wind speeds. In addition, through an instrumentation agreement with homeowners 1
located in coastal areas of Florida, South and North Carolina, the program also collects windinduced pressure data from the roofs of the pre-selected residential buildings. This project has provided for the first time full-scale data on wind loads on houses in suburban areas due to hurricanes. This data now provides researchers with comparative data for model scale wind tunnel experiments being conducted at Clemson s boundary layer wind tunnel to compare fullscale and model-scale wind pressures. The Sea Grant development proposal supports the work of the FCMP through data collection, and analysis and training of graduate and undergraduate students in civil engineering at Clemson University. The deliverables completed under this project include the following: Provided high-fidelity wind velocity data in near-real time through the world-wide website, http://users.ce.ufl.edu/~fcmp/. Expanded the database of ground-level wind velocity data from land falling hurricanes in 2005 through 20 deployments of wind towers. Collected wind pressure data from five houses in the path of land falling hurricane wind events and documented the obstructions and roughness conditions around the instrumented houses. Developed a summary report of the data. The data will be used in the analysis stages on related research projects at Clemson University. 2. DATA COLLECTION METHODS Wind velocity data collection was conducted using wind towers set up in open country (airports and open fields) locations and instrumented single-family residential houses in suburban terrain. The houses had complex roof shapes and architectural features, typical of those in many residential neighborhoods. Wind Anemometer Towers Portable winds towers have instrumentation that is capable of measuring wind velocity at 5 m and 10 m heights (Figure 1). They are used 2
to collect high-resolution wind speed data during a hurricane. Summary wind speed data collected from each tower is uploaded in near real-time to the World Wide Web, http://users.ce.ufl.edu/~fcmp/ for use by the FCMP research team, other researchers and the public. Most of this data is already in the public domain. Wind Pressures on Residential Buildings Pre-selected and pre-wired houses are fitted with pressure sensors just prior to a hurricane landfall. Using battery powered computers and data acquisition systems located in weather-tight strong boxes researchers have obtained data on the pressures induced on the roofs of residential buildings. The house data set includes time histories of wind-induced pressures, from up to 28 pressure transducers, and wind velocity and directional data from one or two anemometers mounted just above the roofs. After the storm, researchers collect the strong boxes, computers and the pressure sensors to perform the data analysis. The researchers also conducted field investigations to record wind damage to structures in the vicinity of the instrumented house. The recorded time history data is downloaded to data storage devices in preparation for further analysis, and is presented here in preliminary form. 3. RESULTS The intent of the project is to utilize wind speed data and the associated wind pressures to determine loads at full-scale buildings located in typical suburban environments. It was decided to use the non-dimensional form of pressure coefficients to compare the data, as this would be easily comparable to wind tunnel test results and wind design guides as currently reported. 3
3.1 Full-Scale House Data In 2005, the FCMP recorded data from five instrumented houses that were affected by hurricanes or tropical storm winds. Pertinent details for the houses are listed in Table 1. From wind tower preliminary wind velocity data, three instrumented houses were affected by hurricane strength winds, one house FL-26 in Navarre, FL during Hurricane Dennis and two houses FL-18 and FL-19 in Naples, FL and Marco Island, FL during Hurricane Wilma. The data includes voltage time histories from each of approximately 28 pressure sensors. Measurements of the wind-induced pressures are required to determine the dimensionless pressure coefficients, which will be compared with wind tunnel derived values. The full-scale pressure sensors use absolute pressure transducers which respond to any atmospheric change in pressure regardless of its source, i.e. the sensors can sense a drop in barometric pressure near the eye of a storm as well as the wind-induced pressures due to wind speed-up near a roof. Therefore, the data analysis consists of a multi-step procedure to normalize all pressure sensors by removing barometric pressure variations in order to isolate the wind-induced pressure changes that occurred during the storm. The data presented here are the voltage changes recorded during the respective wind events and they have not yet been analyzed. The voltage plots shown in Table 7 through Table 11 were collected in 15-minute long data files taken at a sample rate of 100 samples per second. These files were linked together using a MATLAB program to display a near-continuous time-history of voltage output for each sensor, and anemometer. The time-history of a complete storm event lasted for 12 hours or more. 4
3.2 Wind Tower Deployment Four deployment maps are provided (Figures 2, 11, 21, and 30) showing the wind tower locations in the four hurricanes and the locations of FCMP instrumented buildings and other data collection sites that were active during the storms. Once a portable tower is erected and starts collecting data, the data is fed to the FCMP server by cellular telephone and posted to the World Wide Web at 15 min intervals. The summary data reports wind velocity at 10 averaging times including 1 sec, 3 sec, 60 sec, and 15 min periods. Summary data also includes the longitudinal, lateral, and vertical turbulence intensities in addition to an estimate of the roughness lengths (z ) at 5 m and 10 m heights. The summary data report includes temperature, relative humidity, and barometric pressure. Table 2 provides a summary of wind speed data collected by the portable wind towers. 0 4. FUTURE WORK Continuing damage to residential structures suggests there is an urgent need to better understand the wind load generated on low-rise buildings. This will lead to improved building code provisions that address the wind load design requirements for the unique geometries of residential buildings. The data results provided in this report allows ongoing and further research to compare the full-scale and wind tunnel results. It also provides unique opportunities to investigate the effect of full-scale obstructions and terrain on wind-induced pressures. Clemson University and its collaborators in the FCMP using wind towers and instrumented houses have added to the limited database wind loads on low-rise buildings. Our work continues to advance structural analysis and this unique data set was also used by the meteorological researchers at the National Hurricane Center to understand the decay of wind 5
speeds of land falling hurricanes and is currently being used as the basis for wind tunnel studies to improve current modeling techniques. 5. ACKNOWLEDGEMENTS The Principal Investigator and Clemson University wishes to acknowledge the efforts of graduate research students Mr. Russell Carter, Mr. Stephen Furr and Mr. Clay Greene of Clemson University in the preparation of this report. This author acknowledges the generous support provided by the South Carolina Sea Grants Consortium, the Florida Department of Community Affairs, NOAA and the Institute for Business and Home Safety in funding the work. Figure 1. Tower deployed for data collection. 6
Table 1. House Identification and Location. House Identification Number FL-18 FL-19 FL-23 FL-24 FL-26 City, State Marco Island, FL Naples, FL Destin, FL Destin, FL Navarre, FL Hurricane (Peak 3 sec gust from FCMP Tower) Wilma 94 mph Wilma 94 mph Dennis 81 mph Dennis 81 mph Dennis 121 mph Latitude Longitude Hours of Data # of Pressure Taps 25 56 30.4 81 42 53.1 47.25 26 26 15 23.4 81 49 1.0 44 25 30 23 15.2 86 22 4.7 43.25 23 30 23 35.9 86 29 29.2 32.5 26 30 26 2.4 86 52 39.4 37.25 20 Table 2. Summary of 2005 near real-time tower data collection. Wind Peak 3-sec gust Hours Storm Tower wind speed (mph) of Data Dennis T0 121 5.5 T2 96 34.5 T3 81 25.25 Katrina T0 N/A 23 T1 102 26 T2 98 14 T3 93 19.25 T5 N/A 7.25 Rita T0 116 25.5 T1 59 13.25 T3 93 18.5 T5 98 26.25 Wilma T0 94 18.75 T1 105 14.25 T2 109 15.5 T3 96 4 7
Figure 2. Track of Hurricane Dennis and locations of FCMP houses and wind towers. Table 3. Hurricane Dennis wind tower summary. 8
Figure 3. Hurricane Dennis Aerial View Tower TO Figure 4. Hurricane Dennis Aerial View Tower T1 Figure 5. Hurricane Dennis Aerial View Tower T2 9
Figure 6. Hurricane Dennis Aerial View Tower T3 Figure 7. Hurricane Dennis Aerial View Tower T5 10
Figure 8. Plot of Wind Speed and Direction Collected by T0 during Hurricane Dennis. Figure 9. Plot of Wind Speed and Direction Collected by T2 during Hurricane Dennis. 11
Figure 10. Plot of Wind Speed and Direction Collected by T3 during Hurricane Dennis. 12
Figure 11. Track of Hurricane Katrina and locations of FCMP houses and wind towers. Table 4. Hurricane Katrina wind tower summary. 13
Figure 12. Hurricane Katrina Aerial View Tower TO (first location) Figure 13. Hurricane Katrina Aerial View Tower T0 (second location) Figure 14. Hurricane Katrina Aerial View Tower T1 14
Figure 15. Hurricane Katrina Aerial View Tower T2 Figure 16. Hurricane Katrina Aerial View Tower T3 Figure 17. Hurricane Katrina Aerial View Tower T5 15
Figure 18. Plot of Wind Speed and Direction Collected by T1 during Hurricane Katrina. Figure 19. Plot of Wind Speed and Direction Collected by T2 during Hurricane Katrina. 16
Figure 20. Plot of Wind Speed and Direction Collected by T3 during Hurricane Katrina. 17
Figure 21. Track of Hurricane Rita and locations of FCMP houses and wind towers. Table 5. Hurricane Rita wind tower summary. 18
Figure 22. Hurricane Rita Aerial View Tower TO Figure 23. Hurricane Rita Aerial View Tower T1 Figure 24. Hurricane Rita Aerial View Tower T3 19
20 Figure 25. Hurricane Rita Aerial View Tower T5
Figure 26. Plot of Wind Speed and Direction Collected by T0 during Hurricane Rita. Figure 27. Plot of Wind Speed and Direction Collected by T1 during Hurricane Rita. 21
Figure 28. Plot of Wind Speed and Direction Collected by T3 during Hurricane Rita. Figure 29. Plot of Wind Speed and Direction Collected by T5 during Hurricane Rita. 22
Figure 30. Track of Hurricane Wilma and locations of FCMP houses and wind towers. Table 6. Hurricane Dennis wind tower summary. 23
Figure 31. Hurricane Wilma Aerial View Tower TO Figure 32. Hurricane Wilma Aerial View Tower T1 Figure 33. Hurricane Wilma Aerial View Tower T2 24
Figure 34. Hurricane Wilma Aerial View Tower T3 Figure 35. Hurricane Wilma Aerial View Tower T5 25
Figure 36. Plot of Wind Speed and Direction Collected by T0 during Hurricane Wilma. Figure 37. Plot of Wind Speed and Direction Collected by T1 during Hurricane Wilma. 26
Figure 38. Plot of Wind Speed and Direction Collected by T2 during Hurricane Wilma. Figure 39. Plot of Wind Speed and Direction Collected by T3 during Hurricane Wilma. 27
28 Figure 40. FL-18 Dimension Drawing
29 Figure 41. FL-19 Dimension Drawing
30 Figure 42. FL-23 Dimension Drawing
31 Figure 43. FL-24 Dimension Drawing
32 Figure 44. FL-26 Dimension Drawing
Figure 45. East Elevation (front) of FL-18 Figure 46. North Elevation (side) of FL-18 Figure 47. South Elevation (side) of FL-18 33
Figure 48. West Elevation (back) of FL-18 Figure 49. North Elevation (front) of FL-19 Figure 50. East Elevation (side) of FL-19 34
Figure 51. West Elevation (side) of FL-19 Figure 52. South Elevation (back) of FL-19 Figure 53. East Elevation (front) of FL-23 35
Figure 54. North Elevation (side) of FL-23 Figure 55. South Elevation (side) of FL-23 Figure 56. West Elevation (back) of FL-23 36
Figure 57. West Elevation (front) of FL-24 Figure 58. South Elevation (side) of FL-24 Figure 59. North Elevation (side) of FL-24 37
Figure 60. East Elevation (back) of FL-24 Figure 61. West Elevation (front) of FL-26 Figure 62. North Elevation (side) of FL-26 38
Figure 63. South Elevation (side) of FL-26 Figure 64. East Elevation (back) of FL-26 39
Table 7. FL-18 Summary Plots for Hurricane Wilma. 40
Table 7 Continued. FL-18 Summary Plots for Hurricane Wilma. 41
Table 7 Continued. FL-18 Summary Plots for Hurricane Wilma. 42
Table 8. FL-19 Summary Plots for Hurricane Wilma. 43
Table 8 Continued. FL-19 Summary Plots for Hurricane Wilma. 44
Table 8 Continued. FL-19 Summary Plots for Hurricane Wilma. 45
Table 9. FL-23 Summary Plots for Hurricane Dennis. 46
Table 9 Continued. FL-23 Summary Plots for Hurricane Dennis. 47
Table 9 Continued. FL-23 Summary Plots for Hurricane Dennis. 48
Table 10. FL-24 Summary Plots for Hurricane Dennis. 49
Table 10 Continued. FL-24 Summary Plots for Hurricane Dennis. 50
Table 10 Continued. FL-24 Summary Plots for Hurricane Dennis. 51
Table 11. FL-26 Summary Plots for Hurricane Dennis. 52
Table 11 Continued. FL-26 Summary Plots for Hurricane Dennis. 53
Table 11 Continued. FL-26 Summary Plots for Hurricane Dennis. 54