wind pressure shall be determined on the basis of the categories of terrain roughness according to the Table 7.2.1. Terrain roughness can be classified into A,B,C and D four categories: -Category A denotes in shore sea surfaces,islands,sea shores,lake shores and deserts; -Category B denotes open fields,villages,forests,hills,sparsely-populated towns and city suburbs: 一Category C denotes uban districts in densely-populated cities -Category D denotes densely-populated cities with high building urban districts. Table 7.2.1 Exposure Factor for Wind Pressure Height above teair Terrain roughness categories ar sea level (m) A B D 1.17 1.00 0.74 而 1.38 1.00 0.74 1.52 0.74 器 1.63 0.84 1.80 10 2.45 2.68 3.12 3.12 2.91 3≥450 3.12 3.12 7.2.2 For the mountainous buildings,besides the exposure factor for wind pressure can be deter- mined on the basis of the categories of terrain roughness according to the Table 7.2.1,that the adjust ment for the topography conditions shall still be considered,the adjustment be adopt- ed in accordance with the following stipulations respectively: 1 For the mountain peak and the mountain slope,the adjustment coefficient at the top B can be adopted according to the following equation: a=-1+eg1-2动] (7.2.2) Where tga-slope on the windward side of the mountain peak or the mountain slope;when tga> 0.3,taking tga=0.3; coefficients,for the mountain peak taking 3.2,for the mountain slope taking 1.4;
H-full height of the mountain peak or the mountain slope (m); height for the calculating position for buildings from the ground,m;when 2.5H,taking :=2.5H. d 4d Fig.7..Sketch map for mountain peak and mountain s For the other parts of the mountain peak and the mountain slope can accord with the Fig.7.2.2, the value 1 can be taken for the adjustment coefficients,then the adjustment coefficients be- tween AB and BC can be determined by the linear interpolation value of. 2 The closed terrain between the mountains,such as basin,valley and etc., 7=0.75-0.85; The mountain valley pass,the mountain pass identical with wind direction, 7=1.20-1.50. 7.2.3 For the buildings or structural constructions on the offshore sea surface,islands,besides the exposure factor for wind pressure can be detemmined by the category A terrain roughness according to the Table 7.2.1,that the adjustment coefficients given in the Table 7.2.3 shall still be considered. Table 7.2.3 Adjustment coefficients for offshore sea surfaces,islands Distance from seashore(km) 7 <40 1.0 40-60 1.0-1.1 60-100 1.1-1.2 7.3 Shape Factor of Wind Load 7.3.1 The shape factor of wind load for a building or a structural construction can be adopted ac- cording to the following stipulations 1 When the shape of a building or a structural construction is same as the shape shown in the Table 7.3.1,that the stipulations of the Table 7.3.1 can be adopted; 2 When the shape of a building or a structural construction is not same as the shape shown in the Table 7.3.1,that the relevant materials can be referenced; 3 When the shape of a building or a structural construction is not only different with the shape shown in the Table 7.3.1,but also in lack of reference materials,then their shape factors may be de- termined by the wind tunnel test; 4 The shape factors for the important and the complicated shaped buildings or structural co structions shall be determined by the wind tunnel test. 2
Table 7.3.1 Shape Factor of Wind Load Item No. Types Shapes and shape factors a4. Enclosed double -05 0 +0.2 the ground 60°+0.8 5 a Ms 06 pitched roof 60+0.8 For medium values calculated by interpolatio f/1u. 0.5 roof on the ground 5+0.6 05 Enclosed arched -0.8 roof +0.6 For me Enclosed 白 monopitched roof Theof windward pitch,the values given in Item No.2 may be adopte 26
(Continued) Item No. Types Shapes and shape factor 6 high-low double pitched roof Theof windward pitch,the values given No.my be adoed Encloeed roof with skylight Theised herein may be adopted forarhed ofwith Enclosed P double span roof Theof windward pitch,the values given in the Item No.2 may be adopted Enclosed double pitched oof wit讪 unequal spar and unequal pich,the vales given in m No.may beadopte height 05g Enclosed triple span double 10 Theof windward pitch,the values given in Item No.2 may be adopted with unequal span and termined by the formula given below: a=0.6(1-2h1/h) When h=h,taking ga =-0.6 27
Item No. Types Shapes and shape factors 11 6-0.3 12 0.2 -0.4 =0.6 Enclosed triple span double 502 pitchedoo with unegual 13 span and. given inm No.may be adopted unequal height, and with skylight and theof the upper part of windard wall le span can be d in middle span termined by the formula given below 4t=0.6(1-2h1/h) When hy =h,taking al =-0.6 -01 -0.2 匠-05 Enclosed double 14 span double pitched roofs with skylight may be adopted: When as4h,taking =0.2 When a>4h,taking=0.6 3 15 parapet wall When the parapet wall is no high,the roof shpe factor of the he a 28