0KN/m²,风荷载高度变化系数为μZ=1.42,开放式防护架风荷载体型系数为μS=0.087РWK=0.7μS×UZ×W0Р =0.7×0.087×1.42×0.40=0.035KN/m2Р(3)防护架抗倾覆计算(按最不利组合计算)РMNG=Р0.758×6.3+0.831×5.4+1.025×4.5+1.061×3.6+1.101×2.7+1.213×1.8+1.459×0.9Р=4.775+4.487+4.613+3.820+2.973+2.183+1.313Р=24.164KN·mРM风=0.035×1.8×20.7×20.7/2×2/3=8.99KN·mР(4)立杆的稳定性验算Р不考虑风荷载时,立杆的最大轴向压力为:РN=1.2×NG=1.2×1.459=1.751KNР风荷载设计值产生的立杆段弯距MW为:РMW = 0.850×1.4×0.035×0.9×1.72/10=0.011KN·mР不考虑风荷载时,立杆的稳定性计算公式为:Рσ=N/φA≤[ƒ]Р立杆的轴向力设计值为1.751KN;Р立杆的截面回转半径i=1.58cm;Р计算长度附加系数参照规范表5.3.3得:K=1.155;Р当验算杆件长细比时,取块1.0;Р计算长度系数参照规范表5.3.3得:μ=1.50Р计算长度:L0=K×μ×h=1.155×1.50×1.7=2.945mР长细比:L0/i=186Р轴心受压构件的稳定系数φ由长细比209查表得到:φ=0.207Р立杆净截面面积:A=4.89cm2Р立杆净截面模量:W=5.08cm3Рσ=1751/(0.207×489)=17.298N/mm2<[ƒ]=205N/mm2,满足要求!Р考虑风荷载时,立杆的稳定性计算公式Рσ=N/φA +MW/W≤[ƒ]Р =17.298+15000/5080=20.251N/mm2<[ƒ]=205N/mm2 满足要求!
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