6-13 已知某对称配筋的矩形截面偏心受压短柱,截面尺寸b×h=400mm×600mm,承受轴向压力设计值N=1500kN,弯矩设计值M=360kN·m,该柱采用的混凝土强度等级为 C25, 纵向受力钢筋为 HRB400 级,试求纵向受力钢筋面积 As=As′=?选择配筋直径,根数,画配筋断面图(箍筋按构造规定选取)。 解:517.0,/360,/9.1122bycmmNfmmNf ,56040600,400'mmhmmaass取 mmNMe24010150010360360,mmmmhea2020,30max, aieee0260mm, η=1,mmaheesi520403002602 kNNkNbhfbc150011.13782.1378115517.05604009.11N01b 为小偏心受压柱 551.0517.0266560016.1476418764807800000004.121884517.05604009.110.1)40560)(517.08.0(5604009.110.143.05201500000517.05604009.110.1101500))((43.023010120101bcsbcbcbhfahbhfNebhfN 220201987)40560(360)55.05.01(55.05604009.1115201500000)()5.01(mmahfbhfNesAAssyc 4 根直径 18mm(As=As′=1018mm2)或 3 根直径 22mm(As=As′=1140mm2) 0.002bh=0.002×400×600=480mm2<1018mm2<1140mm2 0.006 bh=0.006×400×600=1440mm2<2×1018mm2<2×1140mm2 0.05bh=0.05×400×600=12000mm2>2×1140mm2>2×1018mm2 6-14 已知某矩形截面偏心受压柱截面尺寸b×h=350mm×550mm,计算长度 l0=4.80m,承受轴向压力设计值N=1200kN,弯矩设计,M1=220kN·m,M2=250kN·m,采用 C30 混凝土和HRB400 级纵向钢筋,HPB235 级箍筋,,试求按对称配筋钢筋截面面积 As=As′=? 绘配筋图(取 as=as′=40mm) 解:fc=14.3N/mm2,fy=fy’=360N/mm2,ξb=0.517, h0=550-40=510m m , Cm=0.7+0.3(M1/M2)=0.7+0.3*220/250=0.964 1=0.5 fcA/N=0.5×14.3×350×550/1200000=1.14 取1=1 ea=max[550/30,20mm]=20mm, l0/h=4.80/0.55=8.72 13.11172.8)2010120010250(13005101)()(13001236220canshleNMh M= CmηnsM2=0.964×1.13×250=265.22kN·m e0=M/N=265.22×106/1200×103=221.29mm. ei=e0+ea =221.29+20=241.29mm. e=ei+h/2-as’=241.29+550/2-40=476.29mm Nb= fcb h0ξb=14.3×350×510×0.517=1319.668kN >N=1200kN 大偏心 47.05103...