1. a 1 Wind Borne Debris/Terrain Research Wind Borne Debris/Terrain Research Florida Building Commission Hurricane Research Advisory Committee December 2008 L. A. Twisdale, Ph.D., P. E. Applied Research Associates, Inc. 8537 Six Forks Road Raleigh, N. C. 27615 919 582-3336

2. a 2 WBD/Terrain Modeling Boundary layer transition is affected by tall trees and influence windspeeds, loads, and WBD environment on one and two story residences Z X Displacement Height Open Open to Suburban Transition Ocean Barrier Island Bay BeachTown Suburban Forests Suburban Residential – Heavily Treed V(z)

3. a 3 Outline I. Wind Tunnel Tests Velocity Profiles Effect of Trees on Pressure Coefficients Treed Terrain II. Wind Borne Debris Research III. Status Summary

4. a I. Wind Tunnel Tests 4

5. a 5 Summary: Light and Medium Tree Terrains We used two of the five tree terrains tested for the damage and loss modeling Extra Light  17 trees/acre Light  34 trees/acre Medium  69 trees/acre Light trees  subdivision with light tree buffer and clear-cut within subdivision Medium trees  subdivision with medium tree buffer and some trees in subdivision Results valued for subdivision  400 ft Tree Type Tree Height (ft) CdA (ft 2 /tree) Tree Density (trees/acre) for Light Trees Terrain Medium Trees Terrain Deciduous7018113 26 Conifer70 6934 68 Deciduous50 7930 60 Conifer50 3960121 Equal Mix 1 - - 34 69 1 Equal mix corresponds to 25% of each tree type and height. 400 ft 800 ft Trees (34/acre) Subdivision with No Trees 800 ft 400 ft Trees (69/acre) Subdivision with 35 Trees/acre Tree Terrain Parameters

6. a Tree Configurations 6

7. a Pressure Coefficients 7 Gradient Height GC p Mean Roof Height GC p

8. a 8 Cp min (Gradient Height) – DTA101

9. a 9 Cp min (Mean Roof Height) – DTA101

10. a 10 Cp min (Gradient Height) – DTA201

11. a 11 Cp min (Mean Roof Height) – DTA201

12. a 12 Cp min (Gradient Height) – DTA301

13. a 13 Cp min (Mean Roof Height) – DTA301

14. a 14 Cp min (Gradient Height) – DTA401

15. a 15 Cp min (Mean Roof Height) – DTA401

16. a 16 Cp min (Gradient Height) – DTA501

17. a 17 Cp min (Mean Roof Height) – DTA501

18. a 18 Cp min (Gradient Height) – A01

19. a 19 Cp min (Mean Roof Height) – A01

20. a 20 Cp min (Gradient Height) – A02

21. a 21 Cp min (Mean Roof Height) – A02

22. a 22 Cp min (Gradient Height) – A03

23. a 23 Cp min (Mean Roof Height) – A03

24. a 24 Cp min (Gradient Height) – A04

25. a 25 Cp min (Mean Roof Height) – A04

26. a 26 Cp min (Gradient Height) – A05

27. a 27 Cp min (Mean Roof Height) – A05

28. a 28 Cp min (Gradient Height) – A06

29. a 29 Cp min (Mean Roof Height) – A06

30. a 30 Cp min (Gradient Height) – A07

31. a 31 Cp min (Mean Roof Height) – A07

32. a 32 Cp min (Gradient Height) – A08

33. a 33 Cp min (Mean Roof Height) – A08

34. a 34 Cp min (Gradient Height) – A09

35. a 35 Cp min (Mean Roof Height) – A09

36. a 36 Cp min (Gradient Height) – A10

37. a 37 Cp min (Mean Roof Height) – A10

38. a 38 Cp min (Gradient Height) – A11

39. a 39 Cp min (Mean Roof Height) – A11

40. a 40 Cp min (Gradient Height) – A12

41. a 41 Cp min (Mean Roof Height) – A12

42. a 42 Cp min (Gradient Height) – A13

43. a 43 Cp min (Mean Roof Height) – a13

44. a 44 Cp min (Gradient Height) –A14

45. a 45 Cp min (Mean Roof Height) – A14

46. a Summary 19 different configurations of trees with various densities tested in boundary layer wind tunnel to obtain vertical profiles of wind speeds and turbulence intensities Pressures on roof of 2 story 4:12 gable roof measured in 5 configurations Results show C&C coefficients on both 4:12 and 7:12 roofs increase with increasing gustiness, even when normalized to the peak gust wind (defined as mean plus three standard deviations) 46

47. a Summary Models developed to reproduce the variation of wind speed with height for all 19 cases Azimuthally varying tree density pressure coefficient adjustment factors equal to slope of regression lines used to adjust model Cp values Factors assumed to be valid for all cases (i.e. hip, gable, 1, 2 or 3 story) Results suggest an average tree density of ~30 fifty ft tall trees/acre is need for “treed terrain” Treed terrain must extend upstream of the site for a distance of not less than 800’. 47

48. a II. Wind Borne Debris 48

49. a 49 WBD Tasks 1. Develop parameters for shingle and tile impact tests conducted by UF. 2. New house and subdivision models. 3. Wind tunnel shingle and tile transport tests 4. WBD simulations for matrix of houses, subdivisions and terrains.

50. a New House Models Developed 50 Four new code house models to supplement previous 6 models (4 one story, 2 1½ story) Two 2-story Two 1-story Livable square feet ranges from 1800 to 2700 Houses are modeled with different roof covers Component wind resistances developed to match FBC 2006 strength requirements in each wind zone.

51. a New Subdivision Model Developed 51 Previous work was based on 3 houses per acre subdivision model New subdivision models developed for 5 and 7 houses per acre The houses in the subdivisions can be swapped in and out to create variety of roof covers and number of stories. Houses are modeled with different roof covers and number of stories Example 5 house per acre Subdivision Model

52. a 52 Missile Transport Testing I.Roof Locations – Gable 4/12 (Note zone locations are at center of ASCE 7-05 Zones) a.Zone/Locationb.Oblique Windc.Normal Wind L W W/2 Wind c b a II.Subdivision Setup a.None – First Rowb.Second Row (duplicates previous pressure test) —Tested at 45° c b a Wind 45  L 2L Model House Wind f e 00 e d f ASCE 7 Zones (7  -27  ) L W f d

53. a 53 UWO Experiment Methodology House Model  2-story gable roof (30ft by 34ft by 19.7ft)  Length scale =1:20 Debris Model  Typical Tile: Mass=11.1 lb and Dim=1.37ft by 1.13ft by 0.11ft  Typical Shingle: Mass=4.06 lb and Dim=3.28ft by 1.12ft by 0.043ft Hold-down Force  Varied the full scale failure pressure for tiles and shingles  Force scale=1:8000 Failure Wind Velocity  Determined by wind tunnel drive voltage as

54. a 54 UWO Experiments Two subdivision configurations  Single- and two-row houses  3 and 6.5 houses/acre 16 cases for shingle and 12 cases for tile (30 tests were conducted in each case) Six roof locations to release debris (Zones A, B, C, D, E, F) Two wind directions (0° and 45°) Open country (zo=0.01m) Mean of peak failure wind speeds  Range from 57 to 149 mph

55. a 55 Simulations with HURMIS Model Full hurricane wind trace Geometric model of subdivision Building envelope modeled for each house Component failures Debris transport Impact energy and momentum

56. a HURMISTrajectory Model 56 Aerodynamics Pseudo 6 DOF with Random Update Frequency

57. a 57 HURMIS Transport Comparisons to Wind Tunnel Experiments Pseudo 6 DOF model with random updating of missile orientation. High update frequency simulated random tumbling flight Medium update frequency simulates rotational flight Low update frequency simulated stabilized flight. Matched shingle and tile weights and dimensions to UWO experiments Use of roof vortex velocity model and wake model Use of new peak pressure coefficients Winds are modeled as constant straight winds to match the wind tunnel z 0 Comparisons of debris transport distances follow.

58. a 58 Observed Flight Patterns Flight Patterns 1. Autorotation 2. 3D Spinning 3. Translational (no significant rotation) 4. Falling Mode 5. No Flight 6. Indeterminate Most common = 3D spinning Videos Shingle Tile

59. a Debris Maps - Shingle Zone A (front corner) in 1-row house subdivision and 6.5 houses/acre 59 Zone D (middle edge) in 2-row house subdivision and 3 houses/acre 45° Tile case center of impacts

60. a Debris Maps – Shingle (cont.) Zone D (middle edge) in 1-row house subdivision and 6.5 houses/acre 60 Zone D (middle edge) in 2-row house subdivision and 6.5 houses/acre 0°

61. a Debris Maps – Shingle (cont.) Zone B (ridge corner) in 1-row house subdivision and 6.5 houses/acre 61 Zone B (ridge corner) in 2-row house subdivision and 6.5 houses/acre 45°

62. a Debris Maps – Shingle (cont.) Zone B (ridge corner) in 2-row house subdivision and 3 houses/acre 62 Zone E (middle ridge) in 1-row house subdivision and 6.5 houses/acre 45° 0°

63. a Debris Maps – Shingle (cont.) Zone E (middle ridge) in 2-row house subdivision and 6.5 houses/acre 63 Zone E (middle ridge) in 1-row house subdivision and 6.5 houses/acre 0°

64. a Debris Maps – Shingle (cont.) Zone E (middle ridge) in 1-row house subdivision and 6.5 houses/acre 64 Zone C (leeward ridge corner) in 1-row house subdivision and 6.5 houses/acre 0° 45°

65. a Debris Maps – Shingle (cont.) Zone F (leeward interior roof) in 1-row house subdivision and 6.5 houses/acre 65 Zone F (leeward interior roof) in 2- row house subdivision and 6.5 houses/acre 0°

66. a Debris Maps – Tile Zone A (front corner) in 1-row house subdivision and 6.5 houses/acre 66 Zone D (middle edge) in 2-row house subdivision and 3 houses/acre 45°

67. a Debris Maps – Tile (Cont.) Zone B (ridge corner) in 1-row house subdivision and 6.5 houses/acre 67 Zone B (ridge corner) in 2-row house subdivision and 6.5 houses/acre 45°

68. a Debris Maps – Tile (Cont.) Zone B (ridge corner) in 2-row house subdivision and 3 houses/acre 68 Zone E (middle ridge) in 1-row house subdivision and 6.5 houses/acre 45° 0°

69. a Debris Maps – Tile (Cont.) Zone E (middle ridge) in 2-row house subdivision and 6.5 houses/acre 69 Zone C (leeward ridge corner) in 1- row house subdivision and 6.5 houses/acre 0° 45°

70. a Debris Maps – Tile (Cont.) Zone F (leeward interior roof) in 1- row house subdivision and 6.5 houses/acre 70 Zone F (leeward interior roof) in 2- row house subdivision and 6.5 houses/acre 45°

71. a 71 Observations Results indicate a complex relationship between: Location on house Failure windspeed Flight Distance Very dependent on location and speed of flow above roof at that location Shingles fly higher and faster than tiles COV of flight speeds greater than turbulence intensity Shingles may fly faster than “failure” or release speed Flight distances and speeds were lower from the leeward side Highest relative flight speed from windward gable end, near ridge Big difference between first row and second row transport distances and speeds

72. a HURMIS Modeled Distances vs. UWO Experimental Distances Shingle 72 Tile Model updating is still underway

73. a 73 Field Data Validation: To Be Updated with Refined Trajectory Model

74. a 74 Transport Comparison Summary Results show that model performs reasonably well We use a zone dependent update frequency Previous results include vortex model Validation with field data very similar to previous work Finalization of parameters to be completed within 2 weeks

75. a III. Status Summary 75

76. a 76 Overview of Approach Hurricane Hazard Simulations Select Locations and Buildings Building Models · WBD Protection · No WBD Protection Physical Damage · WBD Protection · No WBD Protection Losses · WBD Protection · No WBD Protection Model Output Metric · Risks · Benefits · Costs · By Location & Building Benefits · Avoided Losses -Building -Contents -Loss of Use -  Costs · FBC Baseline Additional Costs of WBD Protection

77. a 77 Matrix of Cases Terrains Open Suburban Multiple Treed Terrains Windspeeds 90 to 150 mph zones Subdivision Spacings 3 houses per acre (1 story) 7 houses per acre (2 story) Predominant Roof Coverings Shingle Tile Benefit-Cost 9 houses for each case

78. a 78 Do Benefits Outweigh Costs? Benefits (Loss Reduction) Loss Reduction Differential (Compared to FBC w/o WBD Protection) Avoided Losses = Benefits Building Repair and Reconstruction Contents Loss of Use Cost of WBD Protection Increases Initial Costs Range of Protection Options Permanent In Place Systems that Close Removable Shutters Different Materials Range of Protection Costs must be Considered Depends on Building and Location BenefitsCosts Metrics Physical Damage Performance Reliabilities Average Annual Losses  Aggregate Costs Benefit Cost Ratio  Aggregate Loss Reduction Net Present Value  Public and Private Losses

79. a 79 Visualizing Windspeed and Terrain Criteria Open- Suburban Lt Trees Med Trees Terrain If Windspeed Dependent, results should slice vertically If Terrain Dependent, results should slice horizontally If Windspeed & Terrain Dependent, results should slice diagonally Opening Protection Not Needed Opening Protection Needed

80. a 80 Steel Panel Shutters – Minimum Benefit Parameters BC > 1.0 (40 yrs, I = 6%) Public Cost Multiplier = 1, Salvage Value = 0%, Storm Installation Cost Logical = 1

81. a 81 House 4 Benefit Cost Ratios Minimal Benefit Maximum Benefit 0 5 10 15 20 Benefit/Cost Ratio 110 mph 120 mph 130 mph OSSSLT MT OSSSLT MT OSSSLT MT Steel Panel Plywood IRU OS =Open-Suburban SS =Suburban LT =Light Trees MT =Medium Trees 0 5 10 15 20 Benefit/Cost Ratio 110 mph 120 mph 130 mph OSSSLTMTOSSSLTMTOSSSLT MT

82. a 82 Publications and Follow-On Anticipated Publications--2009 1. Wind tunnel testing of debris transport 2. Transport model validation with wind tunnel and field data 3. Treed terrain velocity profiles and effects on pressure coefficients 4. Impact testing for shingles and tiles 5. WBD Risk Analysis Model 6. WBD Large Missile Terrain Based Criteria 7. Risk Consistent WBD Impact Test Criteria Long Term Follow-On Tree fall on small buildings Field work on hurricane damage/WBD in different terrains Flow modeling for closely-spaced buildings