单项选择题
某梯形钢屋架跨度21m,端开间柱距5.4m,其余柱距6m。屋架下弦横向支撑承受山墙墙架柱传来的风荷载,下弦横向支撑的结构布置如图所示,钢材为Q235钢。节点风荷载设计值已求出:W1=17.83kN,W2=31.21kN,W3=26.75kN。
A.90×6,A=21.2cm2,i。imin=1.8cm,iy=2.79cm
B.70×5,A=13.75cm2,imin=2.73cm,iy=2.16cm
C.63×5,A=12.3cm2,imin=2.45cm,iy=1.94cm
D.45×5,A=6.9cm2,imin=1.74cm,iy=1.38cm