What if trees had ? ratings in kN? John Morton Snohomish County SAR Everett Mountain Rescue water-rescue6@scvsar.org ?? ?? ITRS 2015
? John Morton Snohomish Co SAR (WA) & Everett Mountain Rescue Helicopter Rescue Team Lead Rope Rescue instructor Water Rescue Team leader Hovercraft pilot & Rescue Swimmer Instructor for several Tech Rescue specialties …and a little airplane design work “on the side” Engineering References Wind Load on Structure Fluid Dynamics Aerodynamic Turbulence How to Determine Tree Strength U.S. Forest Service and Build Tree Anchors Silvics Manual Audubon Society Rick Weber http://na.fs.fed.us/spfo/pubs/silvics_manual Field Guide to TREES ITRS 2010 Credits & References ITRS 2015
? John Morton Mark Miller Engineering References Wind Load on Structure Fluid Dynamics Aerodynamic Turbulence How to Determine Tree Strength U.S. Forest Service and Build Tree Anchors Silvics Manual Audubon Society Rick Weber http://na.fs.fed.us/spfo/pubs/silvics_manual Field Guide to TREES ITRS 2010 Credits & References ITRS 2015
? Objective: If it can be done responsibly… Define a field- applicable way for rescuers to determine if a “small” tree can be used as a rescue anchor John Morton (water-rescue6@scvsar.org) ITRS 2015
Traditional go/no-go for rescue anchor: helmet sized or larger ? A lot of trees in good locations get bypassed as “too small”
? Diameter Helmet: 28 inch circumference 24” Basketball: 30 in Volleyball: 26 in 2-liter soda bottle: 14 in Tennis ball: 8.5 in Circumference Beer bottle: 7.5 in
? Compression We are worried about pulling on a tree with a rescue system… Shear John Morton (water-rescue6@scvsar.org) ITRS 2015
? We are worried about pulling on a tree with a rescue system… What happens to that Shear same tree during wind? John Morton (water-rescue6@scvsar.org) ITRS 2015
? We are worried about pulling on a tree with a rescue system… What happens to that Shear same tree during wind? Effect of rescue system? John Morton (water-rescue6@scvsar.org) ITRS 2015
? Free Air Wind Speed “Bendiness” of “Aspect ratio” crown varies (height vs spread) among species varies among tree species “Sail area” varies along length of trunk Turbulence reduces wind energy below Bending canopy moment varies along trunk Shear Some tree species root structures are “bending resistant” vs “bending prone” John Morton (water-rescue6@scvsar.org) ITRS 2015
? Effect of Turbulence Free Air Wind Speed Reduces effective wind on smaller trees Turbulence reduces wind energy below canopy Wind- based “rating” on orange cedar is less -- only turbulent wind impacts its sail area
Trees are often in a canopy of mixed species ? approaching North Rim, Grand Canyon Account for Turbulence effects below canopy of mixed tree species (Cheers for USFS Silvics data!)
? Each species has an “aerodynamic profile” Shows 12 ITRS species Profiles shown at SCALED height shown with Circumference=28inch ratings from 65 mph wind
Engineering: wind force acting ? on a cylindrical structure Tree modeled as 20 spindled cylinders supported at a single base Repeat for each tree segment each inch of circumference each wind speed each tree species Magic! Result: tree anchor rating in kN John Morton (water-rescue6@scvsar.org) ITRS 2015
? Results: Anchor ratings per species vs C vs wind (separate HD table) Water_Oak Rating of anchor at 0.6m (kN) C \Wind 35 40 45 50 55 60 65 70 75 80 85 90 16 3.6 4.7 5.9 7.3 8.8 10.5 12.3 14.3 16.4 18.7 21.1 23.7 17 4.3 5.7 7.2 8.9 10.7 12.8 15.0 17.4 20.0 22.7 25.6 28.8 Anchor 18 5.3 6.9 8.7 10.8 13.0 15.5 18.2 21.1 24.2 27.5 31.1 34.9 19 6.3 8.2 10.4 12.8 15.5 18.4 21.6 25.1 28.8 32.8 37.0 41.5 ≥ 32kN 20 7.6 9.9 12.5 15.4 18.7 22.2 26.1 30.2 34.7 39.5 44.6 50.0 21 9.0 11.8 14.9 18.4 22.3 26.5 31.2 36.1 41.5 47.2 53.3 59.7 22 10.5 13.7 17.3 21.4 25.9 30.8 36.2 42.0 48.2 54.8 61.9 69.4 23 12.4 16.2 20.5 25.3 30.6 36.4 42.7 49.5 56.8 64.7 73.0 81.8 24 14.6 19.0 24.1 29.8 36.0 42.9 50.3 58.3 67.0 76.2 86.0 96.4 25 17.0 22.3 28.2 34.8 42.1 50.1 58.8 68.1 78.2 89.0 100 113 26 19.3 25.2 31.9 39.4 47.7 56.8 66.7 77.3 88.7 101 114 128 27 22.3 29.1 36.9 45.5 55.1 65.5 76.9 89.2 102 116 132 147 28 25.1 32.7 41.4 51.1 61.9 73.7 86.4 100 115 131 148 166 Helmet 29 28.6 37.4 47.3 58.4 70.7 84.1 98.7 115 131 150 169 189 30 31.9 41.7 52.8 65.2 78.8 93.8 110 128 147 167 188 211 31 36.1 47.2 59.7 73.7 89.2 106 125 145 166 189 213 239 32 40.0 52.3 66.2 81.7 98.8 118 138 160 184 209 236 265 33 44.8 58.5 74.0 91.4 111 132 154 179 206 234 264 296 34 50.1 65.4 82.8 102 124 147 173 200 230 262 296 331 35 56.1 73.3 92.8 115 139 165 194 225 258 293 331 371 36 61.5 80.3 102 125 152 181 212 246 282 321 362 406 37 69.4 90.6 115 142 171 204 239 277 319 362 409 459 38 75.6 98.7 125 154 187 222 261 302 347 395 446 500 39 84.0 110 139 172 208 247 290 336 386 439 496 556 40 92.4 121 153 189 228 272 319 370 424 483 545 611
? Anchor rating (32kN) vs wind speed (horizontal anchor placed 2ft/0.6m above ground)
? Summary Table with helmet and full-size ratings from trees tested by 65 mph free air wind speed Wind Ratings calculated at Free Air Wind Speed of 65mph 65-ITRS Species Wind Rating @ 28in Wind Rating @ Full Size Wind-rated Anchor Wind-rated High-D Ponderosa_Pine A=59 kN @ C=28in A=17291 kN @ C=119in Anchor: C>23in HD: C>29in W.Red_Cedar A=65 kN @ C=28in A=34862 kN @ C=151in Anchor: C>22in HD: C>29in Bigleaf_Maple A=65 kN @ C=28in A=6368 kN @ C=95in Anchor: C>22in HD: C>29in W.Hemlock A=68 kN @ C=28in A=11730 kN @ C=109in Anchor: C>22in HD: C>28in Smooth_Hickory A=86 kN @ C=28in A=1945 kN @ C=61in Anchor: C>21in HD: C>26in Loblolly_Pine A=91 kN @ C=28in A=15485 kN @ C=102in Anchor: C>20in HD: C>26in Red_Alder A=91 kN @ C=28in A=3254 kN @ C=68in Anchor: C>20in HD: C>26in Douglas_Fir A=94 kN @ C=28in A=72746 kN @ C=153in Anchor: C>20in HD: C>26in Water_Oak A=95 kN @ C=28in A=16979 kN @ C=105in Anchor: C>20in HD: C>26in Engelmann_Spruce A=103 kN @ C=28in A=6013 kN @ C=78in Anchor: C>20in HD: C>25in Quake_Aspen A=214 kN @ C=28in A=412 kN @ C=33in Anchor: C>17in HD: C>21in White_Ash A=230 kN @ C=28in A=1622 kN @ C=46in Anchor: C>17in HD: C>21in John Morton (water-rescue6@scvsar.org) ITRS 2015
? Summary Table with helmet and full-size ratings from trees tested by 85 mph free air wind speed Wind Ratings calculated at Free Air Wind Speed of 85mph 85-ITRS Species Wind Rating @ 28in Wind Rating @ Full Size Wind-rated Anchor Wind-rated High-D Ponderosa_Pine A=101 kN @ C=28in A=29569 kN @ C=119in Anchor: C>20in HD: C>25in W.Red_Cedar A=111 kN @ C=28in A=59616 kN @ C=151in Anchor: C>19in HD: C>24in Bigleaf_Maple A=111 kN @ C=28in A=10890 kN @ C=95in Anchor: C>19in HD: C>24in W.Hemlock A=116 kN @ C=28in A=20058 kN @ C=109in Anchor: C>19in HD: C>24in Smooth_Hickory A=147 kN @ C=28in A=3325 kN @ C=61in Anchor: C>18in HD: C>23in Loblolly_Pine A=156 kN @ C=28in A=26480 kN @ C=102in Anchor: C>17in HD: C>22in Red_Alder A=156 kN @ C=28in A=5565 kN @ C=68in Anchor: C>17in HD: C>22in Douglas_Fir A=161 kN @ C=28in A=124400 kN @ C=153in Anchor: C>17in HD: C>22in Water_Oak A=162 kN @ C=28in A=29036 kN @ C=105in Anchor: C>17in HD: C>22in Engelmann_Spruce A=176 kN @ C=28in A=10283 kN @ C=78in Anchor: C>17in HD: C>22in Quake_Aspen A=367 kN @ C=28in A=704 kN @ C=33in Anchor: C>15in HD: C>18in White_Ash A=394 kN @ C=28in A=2774 kN @ C=46in Anchor: C>15in HD: C>18in John Morton (water-rescue6@scvsar.org) ITRS 2015
? Rules for applying “wind rating” to small trees Tree is healthy, not structurally compromised Symmetrical base & root tops No voids, erosion or other root compromise “Normally” rooted in “normal” forest soil “Normally” (not sand, or clinging to edge of cliff) o Determine tree species (or use limiting species applicable to area) o Measure circumference of tree at 2 feet above ground ?? o Check 2-year table for go/no-go (confirm area and date range) Anchor very low on small trees John Morton (water-rescue6@scvsar.org) ITRS 2015
? Rules for applying “wind rating” to small trees Tree is healthy, not structurally compromised Symmetrical base & root tops No voids, erosion or other root compromise “Normally” rooted in “normal” forest soil “Normally” (not sand, or clinging to edge of cliff) o Determine tree species (or use limiting species applicable to area) o Measure circumference of tree at 2 feet above ground ?? o Check 2-year table for go/no-go (confirm area and date range) Anchor very low on small trees John Morton (water-rescue6@scvsar.org) ITRS 2015
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