CHAPTER 6 WIND LOADS6.1 General6.1.1 Scope of application(1) This chapter describes wind loads for the design of buildings that respond elastically in strongwinds.(2) Two different wind loads are described. The first is for the design of structural frames, and thesecond is for the design of components/cladding of buildings.6.1.2 Estimation principle(1) Wind loads for the design of buildings are individually specified for horizontal wind load forstructural frames, roof wind load for structural frames and wind load for components/cladding. The horizontal wind loads for the design of structural frames shall be individually determined in the along-wind, across-wind and torsional directions.(2) For wind load for structural frames, combination of each horizontal wind load and combination ofhorizontal wind load and roof wind load shall be considered according to A6.8. For components of cladding and structural frame or particular joints of cladding and structural frames, combination of horizontal wind load on structural frames and local wind load on cladding shall be considered. (3) The wind loads shall generally be determined from the design wind speed defined for each winddirection given in A6.1.2.(4) The reference height is generally the mean roof height of the building. The wind loads arecalculated from the velocity pressure at this reference height. However, wind loads on lattice type structures shall be calculated from the velocity pressure at each height, as shown in A6.6.(5) The horizontal wind load on structural frames and the roof wind load on structural frames are givenby the product of the velocity pressure given in A6.1, the wind force coefficient given in A6.2, the gust effect factor given in A6.3 and the projected area or subject area as shown in 6.2 and 6.3. (6) The wind load on components/cladding is given by the product of the velocity pressure given inA6.1, the peak wind force coefficient given in A6.2 and the subject area.(7) For relatively flexible buildings with large aspect ratios, the horizontal wind loads on structuralframes in the across-wind and torsional directions given in A6.4 and A6.5 shall be considered. The criteria for this are described in 6.1.3(1).(8) For flexible buildings with very large aspect ratios, the structural safety against vortex-inducedvibration and aeroelastic instability shall be checked. The criteria for this are described in 6.1.3(2).The wind loads on structural frames and members of round sectional shape caused by vortex induced vibration shall be determined by A6.7.(9) For small buildings and structures with large stiffness, a simplified procedure can be used, as givenin A6.11.(10) The increase of wind-induced vibration caused by neighboring buildings shall be considered fromA6.12.(11) The response acceleration for checking the habitability of a building against wind-inducedvibration shall be evaluated from A6.10. For this evaluation, the 1-year-reccurence wind speed canbe obtained from A6.13.(12) When the wind load shielding effects by surrounding topographies or buildings are considered,the future changes shall be confirmed, and the shielding effect shall be investigated by appropriatewind tunnel study or other suitable verification methods.6.1.3 Buildings for which particular wind load or wind induced vibration is taken into account(1) Buildings for which horizontal wind loads on structural frames in across-wind and torsionaldirections are taken into accountFor the buildings that satisfy the following criteria, wind load in the across-wind direction as defined in A6.4 and wind load in the torsional direction as defined in A6.5 shall be checked.3≥BDH (6.1) whereH (m): reference height as defined in 6.1.2(4)B (m): building breadthD (m): building depth(2) V ortex resonance and aeroelastic instabilityFor buildings that satisfy the following criteria, vortex-induced vibration and aeroelastic instabilityshall be checked by the appropriate wind tunnel tests and so on. For buildings with circular section,the wind load is prescribed in A6.7. 1) For buildings with rectangular section4≥BD H and ⎟⎟⎠⎞⎜⎜⎝⎛≥≥*Tcr T H *Lcr L H 83.0 83.0U BD f U or U BD f U (6.2) where H U (m/s): design wind speed as defined in A6.1.2. (wind directionality factor 1D =K )*Lcr U : non-dimensional critical wind speed for aeroelastic instability in across-wind directioncalculated from Table 6.1*Tcr U : non-dimensional critical wind speed for aeroelastic instability in torsional directioncalculated from Table 6.2T L ,f f (Hz): natural frequency for first mode in across-wind and torsional directions 2) For buildings with circular cross-section7m ≥D H and 2.4mL H ≥D f U (6.3)wherem D (m): building diameter at height 3/2HTable 6.1 Non-dimensional critical wind speed for aeroelastic instability in across-wind direction *Lcr UFlat terrain categoriesSide ratio B D /Scruton number L δNote) Critical speed *Lcr UI, II ≤B D /0.8L δ≤0.7 16L δ L δ>0.7 11 0.8<≤B D / 1.5all 1.2L δ+7.3 1.5<≤B D / 2.5L δ≤0.2 2.3 0.2<L δ≤0.8 12 L δ>0.8 15L δ B D />2.5 L δ≤0.4 3.7 L δ>0.4 not necessary to evaluate III, IV , V ≤B D /0.8 all 4.5L δ+6.70.8<≤B D / 1.2all 0.7L δ+8.8 B D />1.2 all 11Note) L δ is the mass damping parameter defined as )3/(L L BDH M ρζδ=, where L ζ is thedamping ratio for the first mode in the across-wind direction, M (kg) is the total building mass, ρ(1.22kg/m 3) is the air density.Table 6.2 Non-dimensional critical wind speed for aeroelastic instability in torsional direction *Tcr USide ratio B D / Scruton number T δNote) Critical speed *Tcr UB D /≤1.5T δ≤0.05 2 0.05<T δ≤0.1 11 T δ>0.1 not necessary to evaluate 1.5<B D /≤2.5T δ≤0.05 2 0.05<T δ≤0.15 4+8T δ T δ>0.15 8.6+7.4T δ 2.5<B D /≤5 T δ≤0.05 2T δ>0.05 5+10.5T δNote) T δ is the mass damping parameter defined as )36/()(2222T T H D B D B M ρζδ+=, whereT ζ is the damping ratio for the first mode in the torsional direction.6.2 Horizontal Wind Loads on Structural Frames6.2.1 Scope of applicationThis section defines the procedures for estimating horizontal wind loads on structural frames in thealong-wind direction.6.2.2 Procedure for estimating wind loadsAlong-wind loads on structural frames are calculated from Eq.(6.4).A G C q W D D H D = (6.4) whereD W (N): along-wind load at height ZH q (N/m 2): velocity pressure as defined in A6.1.1D C : wind force coefficient as defined in A6.2D G : gust effect factor as defined in A6.3.1A (m 2): projected area at height Z6.3 Roof Wind Load on Structural Frames6.3.1 Scope of applicationThis section defines the procedures for estimating roof wind loads on structural frames of buildings.6.3.2 Procedure for estimating wind loadsRoof wind loads on structural frames are calculated from Eq.(6.5)R R R H R A G C q W = (6.5) whereR W (N): wind loadH q (N/m 2): design velocity pressure as defined in A6.1.1R C : wind force coefficient as defined in A6.2R G : gust effect factor for roof wind load as defined in A6.3.2R A (m 2): subject area6.4 Wind Loads on Components/Cladding6.4.1 Scope of applicationThis section defines the procedures for estimating wind loads on components/cladding of buildings.6.4.2 Procedure for estimating wind loadsWind loads on components/cladding of buildings are calculated from Eq.(6.6).CC H C ˆA C q W = (6.6) whereC W (N): wind loadH q (N/m 2): design velocity pressure as defined in A6.1.1CˆC : peak wind force coefficient as defined in A6.2 C A (m 2): subject area of components/claddingA6.1 Wind Speed and Velocity PressureA6.1.1 Velocity pressureThe design velocity pressure, H q (N/m 2), is calculated from:2H H 21U q ρ= (A6.1) whereρ(kg/m 3): air density, assumed to be 1.22H U (m/s): design wind speed, which depends on wind direction and is defined in A6.1.2A6.1.2 Design wind speedDesign wind speed, H U (m/s), is calculated for each wind direction from:rW H D 0H k E K U U = (A6.2)where 0U : basic wind speed (m/s) depending on the geographic location of the construction site,defined in A6.1.3D K : wind directionality factor defined in A6.1.4.H E : wind speed profile factor at reference height H defined in A6.1.5.rW k : return period conversion factor defined in A6.1.7.The 1-year-recurrence wind speed is defined in A6.13 for evaluation of habitability.A6.1.3 Basic wind speedBasic wind speed 0U (m/s) corresponds to the 100-year-recurrence 10-minute mean wind speed over a flat, open terrain at an elevation of 10m. The wind speed is defined in Fig.A6.1 for various locations in Japan.Figure A6.1 Basic wind speed 0U (m/s) Izu Islands, not shown in the map 46Ogasawara Islands, Satsunann Islands,Okinawa Islands, Daitou Islands, Sakishima Islands, not shown in the map50A6.1.4 Wind directionality factorWind directionality factor D K reflects the directional characteristics of the extreme wind, which are influenced by the geographical location and topographic feature of the construction site. It shall be determined as follows, with reference to the wind directionality factors for the 8 cardinal directions shown in Table A6.1.(1) Where the aerodynamic shape factors for each wind direction are known from an appropriate wind tunnel experiment, the wind directionality factor D K , which is used to evaluate the wind loads on structural frames and components/cladding for a particular wind direction, shall take the same value as that for the cardinal direction whose 45 degree sector includes that wind direction.(2) Where the aerodynamic shape factors in A6.2 are used1) When assessing wind loads on structural framesa) Where the aerodynamic shape factors are dependent on wind direction, four wind directions should be considered that coincide with the principal coordinate axis of the structure. If the wind direction is within a 22.5 degree sector centered at one of the 8 cardinal directions, the wind directionality factor D K for this direction shall be adopted. If the wind direction is outside of the 22.5 degree sector, the larger of the 2 nearest cardinal directions shall be adopted.b) Where the aerodynamic shape factors are independent of wind direction, the wind directionality factor D K shall take the same value as that for the cardinal direction whose 45 degree sector includes that wind direction.2) When assessing wind loads on components/cladding1D =KTable A6.1 Wind directionality factor D KWakkanai Kitamiesashi Haboro Omu Rumoi Asahikawa Abashiri Otaru Sapporo Iwamizawa NE 0.95 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.9 E 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 SE 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 11 S 1 0.85 1 0.85 0.85 1 0.85 0.85 1 1 SW 1 1 1 1 0.95 1 0.85 1 0.85 0.85W 0.85 1 1 1 0.95 1 0.95 1 0.95 1NW 0.85 0.85 0.95 0.85 1 0.85 11 1 0.95 N 0.95 0.85 0.85 0.85 1 0.85 0.9 0.85 0.85 0.9Obihiro Kushiro Nemuro Suttsu Muroran Tomakomai Urakawa Esashi Hakodate KutchanNE 0.85 0.85 0.9 0.85 0.85 0.85 0.85 0.85 0.95 0.85 E 0.85 0.9 0.9 0.85 0.85 0.85 0.85 0.85 0.95 0.95 SE 0.85 0.9 0.85 1 0.85 0.85 0.85 0.85 0.85 0.95 S 0.85 0.85 0.85 1 0.85 0.85 0.85 1 1 0.95 SW 0.85 0.85 0.85 0.85 0.85 0.85 0.85 1 1 0.95 W 1 1 0.95 1 1 0.85 1 1 0.95 1 NW 1 0.9 1 1 1 0.9 1 1 0.9 1 N 0.85 0.85 0.95 0.9 0.85 1 0.85 0.85 0.85 0.85KTable A6.1(continued) Wind directionality factor DHachinoheWakamatsu Fukaura Aomori MutsuAkita MombetsuHiroo OfunatoShinjoNE 0.9 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85E 0.9 0.85 0.85 0.85 0.9 0.85 0.85 0.85 0.85 0.85 SE 0.85 0.85 0.85 0.85 0.9 0.85 0.85 0.85 0.85 0.85S 0.85 0.85 0.85 0.85 0.85 1 0.85 0.85 0.85 0.95 SW 1 1 0.85 0.85 0.85 1 1 0.95 1 0.95 W 1 1 0.85 1 1 0.95 1 1 1 1 NW 1 0.85 1 1 1 0.95 0.9 0.85 0.95 1 N 0.9 0.85 0.9 0.85 0.85 0.9 0.85 0.85 0.85 0.85 MoriokaYamagata SendaiIshinomaki Fukushima Shirakawa Onahama Wajima Miyako SakataNE 0.85 0.85 0.85 0.85 0.85 1 0.85 0.85 1 0.9E 0.85 0.85 0.85 0.85 0.85 0.95 0.85 0.85 0.85 0.85 SE 0.85 0.9 0.85 0.85 0.85 0.9 0.85 0.85 0.9 0.85 S 0.85 0.9 0.85 0.9 0.85 0.85 0.85 0.85 0.85 0.9 SW 0.95 0.95 0.9 1 0.85 0.85 0.85 0.85 0.85 1W 1 1 1 1 1 1 1 1 0.95 1 NW 1 0.95 1 0.95 1 1 1 1 1 0.95 N 0.95 0.95 0.85 0.85 0.85 1 0.85 0.95 1 0.95 Aikawa Niigata Kanazawa Fushiki Toyama Nagano Takada Utsunomiya Fukui TakayamaNE 0.85 0.85 0.85 0.9 0.85 0.85 0.85 0.9 0.85 0.85E 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 SE 0.85 0.85 0.85 0.85 0.9 0.85 0.85 0.85 1 0.9S 0.85 0.85 0.9 0.85 1 0.85 0.85 0.85 1 10.85 1 1 1 0.9 1 0.85 0.85 0.850.85 SWW 0.85 1 0.9 0.95 0.9 1 1 0.85 0.85 0.85 NW 1 1 0.85 0.85 0.85 0.9 0.95 0.85 1 0.85N 1 0.9 0.85 0.9 0.85 0.85 0.85 1 1 0.85Kumagai Mito Tsuruga Gifu Nagoya Iida Kofu ChichibuMatsumotoSuwaNE 0.85 0.85 0.85 1 0.85 0.85 0.85 0.95 0.85 0.85E 0.85 1 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85SE 1 1 0.85 0.85 0.85 1 1 0.85 0.85 0.85S 1 0.95 0.85 0.85 0.85 0.95 1 0.85 0.85 0.85SW 0.9 0.85 0.85 0.85 0.85 0.85 0.85 1 0.85 0.85W 0.85 1 0.95 0.9 0.85 0.85 0.85 1 0.85 0.9 NW 0.85 1 1 1 1 0.9 0.85 1 1 1N 0.85 0.85 0.95 1 0.85 0.85 0.85 0.95 1 0.85TokyoOwase Ueno Tsu IrakoChoshiHamamatsu Omaezaki Shizuoka MishimaNE 0.9 0.85 0.85 0.9 0.95 1 0.85 1 0.85 0.85E 0.85 1 1 0.95 0.95 1 0.85 0.85 0.85 0.95 SE 0.85 0.9 1 0.95 0.85 0.85 0.85 0.85 0.85 0.85S 0.85 0.85 0.85 0.9 0.85 0.95 0.95 0.85 0.85 0.85 SW 0.85 0.9 0.85 0.85 0.85 0.95 1 0.85 0.85 0.95W 0.85 0.85 0.95 1 1 1 1 0.85 0.85 1NW 0.95 0.85 0.9 1 1 0.95 0.85 0.85 1 0.95N 1 0.85 0.85 0.85 0.85 0.85 0.85 1 1 0.85KTable A6.1(continued) Wind directionality factor DTateyama Katsuura Oshima Miyakojima Hachijojima Chiba YokkaichiYokohamaIrozaki AjiroNE 0.85 0.95 0.85 0.85 0.85 1 0.85 0.85 0.85 0.85 E 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.9 1 SE 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.9 1S 0.85 0.85 0.85 0.85 1 0.85 0.85 1 0.95 0.85 SW 0.9 1 0.85 0.85 1 0.95 0.85 1 0.95 1 W 1 1 0.85 0.85 0.85 0.9 0.95 0.9 0.85 1 NW 0.85 0.85 1 1 1 0.85 1 0.9 1 0.85 N 0.85 0.95 1 1 0.9 1 1 0.9 1 0.85HamadaToyooka Maizuru HagiTsuyamaYonago TottoriSaigoMatsue SakaiNE 0.9 0.9 0.95 0.85 0.85 0.85 0.85 0.85 0.85 0.85E 0.85 0.85 0.95 0.85 0.85 0.85 0.85 0.85 0.85 0.95SE 0.85 0.85 0.85 0.85 0.85 0.85 1 0.9 0.85 0.95S 0.85 0.85 0.85 0.85 1 0.85 1 0.9 0.85 0.85SW 0.85 0.9 0.95 0.95 0.85 0.85 0.85 0.85 0.9 0.850.85 0.9 1 0.95W 0.85 1 1 1 0.850.85NW 0.85 0.95 0.85 1 0.9 1 1 1 0.85 0.950.85 1 0.9 1 1 1 1 1N 1 0.95Fukuyama Okayama Himeji Kobe OsakaHiroshima KureKyotoHikone ShimonosekiNE 1 0.85 0.85 0.85 1 0.95 0.85 0.85 1 0.9E 0.95 0.85 0.85 0.85 0.85 0.85 0.85 0.85 1 0.85 SE 0.85 0.85 0.85 0.95 0.85 0.85 0.85 1 0.85 0.85S 0.85 0.85 0.85 1 0.9 0.85 0.85 1 0.85 1 SW 0.85 0.85 0.85 1 0.9 0.85 1 0.85 0.85 1W 0.85 0.95 0.85 0.85 0.9 0.85 0.85 0.9 0.85 1 NW 0.95 1 1 0.85 1 0.85 0.85 0.9 1 1N 0.95 0.85 0.95 0.85 1 1 0.85 0.85 1 1Sumoto Wakayama Shionomisaki Nara Yamaguchi Izuhara Hirado Fukuoka Iizuka Sasebo NE 0.85 0.85 0.95 1 0.85 0.85 0.9 0.85 0.85 1E 0.85 0.85 0.95 1 0.9 0.85 0.85 0.85 0.85 0.85 SE 0.9 1 0.85 0.85 1 0.85 0.85 1 0.85 0.85 S 1 1 0.9 0.85 0.85 0.95 0.85 1 0.9 0.85 SW 0.85 0.95 0.95 0.85 0.85 1 0.85 0.85 0.9 0.85 W 0.85 1 1 0.85 0.85 0.9 0.85 1 0.85 0.9 NW 0.85 1 1 0.85 0.85 0.95 0.95 1 1 0.9 N 0.85 0.85 0.85 0.85 0.85 1 1 1 1 1Nagasaki Kumamoto Nobeoka Akune Kagoshima Miyakonojo MiyazakiSaga Hita OitaNE 0.85 0.85 0.85 0.9 0.85 0.85 0.85 0.85 0.85 0.9E 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.9 0.85 SE 0.85 0.85 1 0.85 0.85 0.95 0.85 0.95 1 1S 1 1 0.85 0.9 1 1 1 0.95 1 0.85 SW 0.85 1 0.85 1 1 0.85 0.9 1 0.9 0.85 W 0.85 0.95 0.9 1 0.95 0.85 0.85 0.85 0.85 0.85 NW 0.95 0.85 0.9 0.95 1 0.9 0.85 0.85 0.85 0.85N 0.95 0.85 0.85 0.9 1 0.9 0.85 0.85 0.85 0.9Table A6.1(continued) Wind directionality factor D KMakurazaki Aburatsu Yakushima Tanegashima Ushibuka Fukue Matsuyama Tadotsu Takamatsu Uwajima NE 0.85 0.95 0.85 0.85 0.85 0.85 0.9 0.85 0.9 0.95 E 1 0.9 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.95 SE 1 0.9 0.95 0.95 0.85 0.9 1 0.85 0.85 1 S 1 1 11 0.85 0.95 1 0.85 0.85 1 SW 1 1 1 0.9 0.9 0.95 0.95 1 0.95 0.85W 0.95 0.85 0.85 0.91 0.95 0.95 1 1 0.85 NW 0.95 0.85 0.85 0.85 0.85 1 0.9 0.85 0.9 0.85 N 0.95 0.95 0.85 0.85 0.85 1 0.9 0.85 0.9 0.85Kouchi Tokushima Sukumo Shimizu MurotomisakiNaze Miyakojima Kumejima Naha Nago NE 0.85 0.85 0.85 0.85 1 0.85 0.95 0.85 0.85 0.85E 1 0.85 0.95 0.95 1 0.85 0.85 0.85 0.85 0.85 SE 1 1 0.95 0.9 0.9 0.9 0.85 0.95 0.95 0.9 S 0.85 1 0.9 0.95 0.85 0.85 0.951 1 1 SW 0.85 0.85 1 0.95 0.95 0.85 0.851 1 1 W 0.85 0.85 1 11 0.85 0.95 0.85 1 0.85 NW 0.85 0.85 1 0.85 0.91 1 1 1 0.9 N 0.85 0.85 0.85 0.85 0.851 1 1 1 0.85Okinoerabu MinamidaitojimaNE 0.850.9 E 0.850.85 SE 10.95 S 10.95 SW 0.850.85 W 0.850.85 NW 0.91 N 0.95 1A6.1.5 Wind speed profile factor(1) Wind speed profile factorWind speed profile factor E is calculated from:g r E E E = (A6.3) wherer E : exposure factor for flat terrain categories, defined in (2)g E : topography factor defined in (3)(2) Exposure factor based on flat terrain categoriesThe exposure factor for flat terrain categories is defined in 2), according to the flat terrain categories defined in 1).1) The flat terrain categories of the construction site are defined in Table 6.2. However, if the terrain category changes from smooth to rough in the region of the smaller of 40H (H : reference height) and 3km upwind of the construction site, the terrain category of the construction site is assumed the same as that of the upwind smooth terrain.Table A6.2 Flat terrain categoriesCategory Condition at construction site and upwind region Smooth I Open, no significant obstruction, sea, lake ↑II Open, few obstructions, grassland, agricultural field III Suburban, wooded terrain, few tall buildings (4 to 9-story) ↓IV City, tall buildings (4 to 9-story)Rough VCity, heavy concentration of tall buildings (higher than 10-story)2） The exposure factor based on the flat terrain categories is defined in Eq.(A6.4), according to the terrain categories defined in 1).⎪⎪⎩⎪⎪⎨⎧≤⎟⎟⎠⎞⎜⎜⎝⎛≤<⎟⎟⎠⎞⎜⎜⎝⎛=b G b Gb G r 7.1 7.1Z Z Z Z Z Z Z Z Z E αα(A6.4) whereZ (m): height above groundα,,G b Z Z : parameters determining the exposure factor r E , defined in Table A6.3Table A6.3 Parameters determining r ECategory I II III IV V b Z (m) 5 5 10 20 30 G Z (m)250 350 450 550 650 α0.1 0.15 0.2 0.27 0.35(3) Topography factorTopography factor, which reflects the change of the mean wind speed that occurs as wind passes at right angles over escarpments or ridge-shaped topography, as shown in Figs.A6.2 and A6.3, is defined in Eq.(A6.5). However, when the inclination s θ calculated from Eq.(A6.6) is less than 7.5 degrees, or s s /H X is beyond the range shown in Tables A6.4 and A6.5, it is not necessary to consider the topography factor, i.e., 1g =E .1)(exp 1)()1(3s 23s 21g +⎭⎬⎫⎩⎨⎧−−⎭⎬⎫⎩⎨⎧+−−=C H Z C C H ZC C E and 1g ≥E (A6.5) ss 1s 2tan L H−=θ (A6.6)where321,,C C C : parameters determining the topography factor, are given in Tables A6.4 and A 6.5,and depend on the topography shape, inclination s θ and distance s X (m) from thetop of the topographic feature to the construction site. When the inclination s θ is greater than 60 degrees, the topography factor is assumed to be the same as that at 60 degrees.Z (m): height above ground. It is assumed the same value as b Z when it is smaller than b Z .s H (m): height of the topographys L (m): horizontal distance from the top of topographic feature to the point where the height ishalf the topography height as shown in Figs. A6.2 and A6.3Figure A6.2 EscarpmentsFigure A6.3 Ridge-shaped topographyTable A6.4 Parameters determining g E (escarpments)θs X s /H s−4 −2 −1 −0.50 0.5 1 2 4 8 7.5°C 11.15 1.3 1.5 1.5 1.6 1.45 1.3 1.3 1.2 1.15C 2 0.8 0.8 0.8 0.8 0.8 0.7 0.6 0.6 0.5 0.4 C 3 −2 −2 −2 −2 −2 −2 −2 −2 −2 −2 15°C 1 0.4 1 1.2 1.55 2.1 1.65 1.5 1.3 1.2 1.15C 2 0.9 0 0.650.85 1 0.8 0.7 0.55 0.45 0.35C 3 −2 −2 −2 −2 −2 −2 −2 −2 −2 −2 30°C 1 0.7 −0.5 1.05 1.1 1.3 1.3 1.25 1.2 1.15 1.1 C 2 0.65 1.2 1.65 1.5 1.45 1.3 0.9 0.9 0.85 0.6 C 3 −2 −2 1 0.8 0.3 0.3 0.5 0.7 1.2 1.4 45°C 1 0.8 0 −3.5 1.1 1.2 1.35 1.3 1.2 1.15 1.1 C 2 0.5 1 1.6 2 1.1 1.3 1.3 1.3 0.9 0.55C 3 −2 −2 −2 0.8 0.3 0.2 0.75 1.05 1.4 2 60°C 1 0.6 0.1 −1.8−2.4 1.2 1.4 1.35 1.25 1.15 1.1 C 2 0.65 0.9 1.3 2.6 2 1.8 1.7 1.5 0.85 0.45C 3−2 −2 −2 −1 0.5 0.5 0.8 1.2 1.9 3.1Table A6.5 Parameters determining g E (ridge-shaped topography)θs X s /H s−4 −2 −1 −0.50 0.5 1 2 4 8 7.5°C 1 1.1 1.2 1.35 1.35 1.4 1.3 1.3 1.2 1.1 1 C 2 1 1 1 1 1.5 1.2 1.1 2 1.6 0 C 3 0 0 0 0 0.2 0.2 0.2 0.5 0.9 0 15°C 1 1 1.05 1.2 1.25 1.3 1.4 1.3 1.25 0.35 0.65C 2 0 0 1 1 1 1.5 1.5 2 3 2 C 3 0 0 0 0 0 0.5 0.6 1.1 0.2 0.3 30°C 1 0.75 0.55 0.85 1 1.2 1.3 1.25 1.2 1.1 1.02C 2 1.5 2 2 0 1 2 2 1.6 1.7 1.7 C 3 0 0 0 0 0 1.1 1.3 2.1 2.2 2.8 45°C 1 0.75 0.55 0.2 0.75 1.15 1.2 1.15 1.12 1.1 1.02C 2 1.5 2 2 3 1 2.5 2.5 2 1.6 1.3 C 3 0 0 0 0 0 1.2 1.9 2.2 2.5 3.2 60°C 1 0.75 0.55 0.2 0.2 1.15 1.12 1.15 1.12 1.1 1.02C 2 1.5 1.5 1.8 3 1 2.2 2.5 2 1.6 1.3 C 30 0 0 0 0 1.8 2 2.3 2.6 3.4Note) For a particular inclination s θ and a horizontal location s s /H X , the topography factor iscalculated by interpolating linearly from the values at the nearest inclinations and horizontal locations.A6.1.6 Turbulence intensity and turbulence scaleTurbulence intensity and turbulence scale in A6.2, A6.3 are defined as follows. (1) Turbulence intensity1) Turbulence intensity Z I is defined according to the conditions of the construction site as: gI rZ Z E I I = (A6.7)whererZ I : turbulence intensity at height Z on the flat terrain categories, defined in 2)gI E : topography factor defined in 3)2) Turbulence intensity on flat terrain categoriesTurbulence intensity rZ I on flat terrain categories is defined in Eq.(A6.8) according to the terrain categories.⎪⎪⎩⎪⎪⎨⎧≤⎟⎟⎠⎞⎜⎜⎝⎛≤<⎟⎟⎠⎞⎜⎜⎝⎛=−−−−b 05.0G b Gb 05.0G rZ1.0 1.0Z Z Z Z Z Z Z Z Z I αα (A6.8) whereZ (m): height above groundα,,G b Z Z : parameters determining the exposure factor, defined in Table A6.33) Topography factor for turbulence intensityTopography factor for turbulence intensity for the condition, in which the wind passes at rightangles to the escarpments or ridge-shaped topography, as shown in Figs.A6.2 and A6.3, is defined as:g I gI E EE = (A6.9)where1)(exp 1)()1(3s 23s 21I +⎭⎬⎫⎩⎨⎧−−⎭⎬⎫⎩⎨⎧+−−=C H ZC C H Z C C E and 1I ≥E (A6.10)whereI E : topography factor for the standard deviation of fluctuating wind speed. When theinclination s θ calculated from Eq.(A6.6) is less than 7.5, or the distance from the top of the topographic feature s X (m) is beyond the range of s s /H X in Tables A6.6 and A6.7, it is not necessary to consider the topography factor, i.e., 1I =E . g E : topography factor for mean wind speed, defined in Eq.(A6.5)321,,C C C : parameters determining the topography factor I E , are given in Tables A6.6 andA6.7, and depend on the topography shape, inclination s θ andthe distance s X (m) from the top of the topographic feature to the construction site. When the inclination s θ isgreater than 60 degrees, the topography factor is assumed to be the same as that at 60 degrees.Z (m): height above ground. It is assumed to be the greater of b Z and c Z when it is smallerthan b Z in Table A6.3, or c Z in Tables A6.6 and A6.7sH(m): height of topographysL(m): horizontal distance from the top of the topographic feature to the point where the height is half the topography heightTable A6.6 Parameters determining I E (Escarpments)θsX s /H s−4 −2 −1 −0.50 0.5 1 2 4 87.5° Z c/H s0 0 0 0 0 0 0 0 0 0 C1 1 1 1 1 1 1 1 1 1 1 C2 0 0 0 0 0 0 0 0 0 0 C3 0 0 0 0 0 0 0 0 0 015° Z c/H s0 0 0 0 0 0 0 0 0 0 C1 1 1.05 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 C2 0 0 0.2 0.2 0.3 0.4 0.50.5 0.3 0.3 C3 0 0 0 0 0 0 0 0 0 030° Z c/H s0 0 0 0 0 0 0 0 0 0 C1 1.05 1.05 1.1 1.15 1.2 1.3 2.5 1.8 1.4 1.25 C2 0 0 0 0.7 2 2.5 10 8 4 1.5 C3 0 0.5 1 1 0.5 0 0 0.1 0.2 0.645° Z c/H s0 0 0 0 0 0 0 0.3 0.3 0.2 C1 1.05 1.1 1.15 1.3 1.8 1.5 3 3 1.8 1.5 C2 0 0 0 1.4 1.7 1.6 6 5 3.5 2 C3 0 0 0.5 0 −1 −0.80 0 0.3 0.560° Z c/H s0 0 0 0 0 0 0 0.5 0.7 0.9 C1 1.1 1.15 1.2 1.3 6 8 4 3.5 2.2 1.7 C2 0 0 0 0.7 2.5 5 8 5 3 1.5 C3 0 0 0.3 0.5 −1.3−0.40.20.2 0.4 0.5Table A6.7 Parameters determining I E (Ridge-shaped topography)θsX s /H s−4 −2 −1 −0.50 0.5 1 2 4 8 7.5°Z c /H s 0 0 0 0 0 0 0 0 0 0 C 1 1 1 1 1 1 1 1 1 1 1 C 2 0 0 0 0 0 0 0 0 0 0 C 3 0 0 0 0 0 0 0 0 0 0 15°Z c /H s 0 0 0 0 0 0 0 0.6 0 0 C 1 1 1 1 1 1 3.4 4.2 4 2.8 2 C 2 0 0 0 0 0 19 11 4.6 2 1.6 C 3 0 0 0 0 0 0.1 0.2 0.3 0.6 0.7 30°Z c /H s 0 0 0 0 0 0.6 0.8 1.5 1.6 2.2 C 1 1 1 1 1 1 1.6 1.9 2.2 3.2 2.7 C 2 0 0 0 0 0 5 4 2 1.7 1.3 C 3 0 0 0 0 0 0.4 0.6 1 0.7 0.5 45°Z c /H s 0 0 0 0 0 0.8 1.5 1.7 1.9 2.5 C 1 1 1 1 1 1 1.4 1.7 2.1 2.8 2.8 C 2 0 0 0 0 0 2.6 2.2 1.7 1.4 1.3 C 3 0 0 0 0 0 0.8 1.1 1.2 0.9 0.5 60°Z c /H s 0 0 0 0 0 1.35 1.6 1.8 2 2.6 C 1 1 1 1 1 1 1.6 1.8 2.1 2.9 2.9 C 2 0 0 0 0 0 2 1.6 1.3 1.3 1.2 C 30 0 0 0 0 1 1.2 1.2 0.8 0.6Note) For a particular inclination s θ and a horizontal location s s /H X , the topography factor forfluctuating wind speed is calculated by interpolating linearly from the values at the nearest inclinations and horizontal locations.(2) Turbulence scaleTurbulence scale is defined independently of the terrain categories of the construction site as:⎪⎩⎪⎨⎧≤≤<⎟⎠⎞⎜⎝⎛=m 30 10030m 30100G 5.0Z Z Z Z Z L (A6.11) whereZ (m): height above groundG Z : parameter determining the exposure factor, defined in Table A6.3A6.1.7 Return period conversion factorReturn period conversion factor rW k is calculated from Eq.(A6.12). ()9.39.2ln 163.0U U rW +−−=λλr k (A6.12)where500U U U =λ whereU(m/s): 500-year-recurrence 10-minute mean wind speed at 10m above ground over a flat 500and open terrain, defined in Fig.A6.4U(m/s): basic wind speed, defined in A6.1.3r(year): design return periodFigure A6.4 500-year-recurrence 10-minute mean wind speed at 10m above ground over a flat andopen terrain 500U (m/s)Izu Islands, not shown in the map 52Ogasawara Islands, Satsunann Islands,Okinawa Islands, Daitou Islands, Sakishima Islands, not shown in the map58A6.2 Wind force coefficients and wind pressure coefficientsWind force coefficients and wind pressure coefficients fall into two categories corresponding to the design of the structural frames and components/claddings. The coefficients shall be estimated from wind tunnel experiments or from the following procedure using the wind pressure coefficients (external and internal pressure coefficients) and wind force coefficients provided in this clause.A6.2.1 Procedure for estimating wind force coefficients(1) Wind force coefficients for design of structural frames1) Wind force coefficients D C for estimating horizontal wind loads on structural framesWind force coefficients are given in A6.2.4(1) and A6.2.4(4) or calculated from Eq.(A6.13) using the external pressure coefficients provided in A6.2.2.pe2pe1D C C C −= (A6.13)wherepe1C : external pressure coefficient on windward face pe2C : external pressure coefficient on leeward face2) Wind force coefficients R C for estimating roof wind loads on structural framesWind force coefficients are given in A6.2.5(2) or calculated from Eq.(A6.14) using the externalpressure coefficients provided in A6.2.2 and the internal pressure coefficients provided in A6.2.3.pi pe R C C C −= (A6.14) wherepe C : external pressure coefficient on roof pi C : internal pressure coefficient3) Wind force coefficients D C for estimating horizontal wind loads on lattice structuresWind force coefficients are given in A6.2.4(3) or calculated from the wind force coefficients for individual members provided in A6.2.4(5).(2) Peak wind force coefficients CˆCfor design of components/cladding Peak wind force coefficients C ˆC are given in A6.2.7 or calculated from Eq.(A6.15) using the peak external pressure coefficients provided in A6.2.5 and the factor for the effect of fluctuating internalpressures provided in A6.2.6.pi *peCˆˆC C C−= (A6.15) wherepeˆC : peak external pressure coefficient pi *C : factor for effect of fluctuating internal pressures。