1.1.2 混凝土强度等级 C30, fcu,k = 30N/mm, fc = 14.331N/mm, ft = 1.433N/mm
1.1.3 钢筋材料性能: fy = 300N/mm, fy' = 300N/mm, fyv = 210N/mm,
fyh = 300N/mm, Es = 200000N/mm
1.1.4 受拉钢筋面积 As = 10mm; 箍筋面积 Asv = 100mm,箍筋间距 s = 200mm
1.1.5 T形截面,截面尺寸 b×h = 200×600mm, h0 = 562.5mm;
受压区翼缘宽度 bf' = 600mm,受压区翼缘高度 hf' = 100mm
1.1.6 计算跨度 l0 = 7mm,l0/h = 0.01 < 5,按深受弯构件计算,ρsh,min = 0.00%
1.2 正截面受弯承载力计算
T形截面的深受弯构件,按矩形截面深受弯构件计算。
1.2.1 相对界限受压区高度 ξb = β1 / [1 + fy / (Es·εcu)]
= 0.8/[1+300/(200000*0.0033)] = 0.550
1.2.2 单筋矩形截面或翼缘位于受拉边的T形截面受弯构件受压区高度 x 按下式计算:
x = fy·As / (α1·fc·b) = 300*10/(1*14.331*200)
= 1mm ≤ ξb·h0 = 0.550*562.5 = 309mm
当 l0/h ≤ 2 时,跨中截面 as = 0.1h = 60mm,h0 = h - as = 540mm
当 x < 0.2h0,取 x = 0.2h0 = 108mm
当 l0 < h 时,取内力臂 z = 0.6l0 = 4
1.2.3 M = As·fy·z = 10*300*4 = 0.012kN·m
1.2.4 相对受压区高度 ξ = x / h0 = 108/540 = 0.2 ≤ 0.55
配筋率 ρ = As / (b·h0) = 10/(200*540) = 0.01%
最小配筋率 ρmin = Max{0.20%, 0.45ft/fy} = Max{0.20%, 0.21%} = 0.21%
As,min = b·h·ρmin = 258mm
1.3 斜截面承载力计算
当 V > 0.7·ft·b·h0、500 < h ≤ 800mm 构造要求:
最小配箍面积 Asv,min = (0.24·ft / fyv)·b·s = (0.24*1.433/210)*200*200 = 66mm
箍筋最小直径 Dmin = 6mm,箍筋最大间距 smax = 250mm
1.3.1 一般深受弯构件,其斜截面受剪承载力按下列公式计算:
V ≤ 0.7·(8 - l0/h) / 3·ft·b·h0 + 1.25·(l0/h - 2) / 3·fyv·Asv/s·h0
+ (5 - l0/h) / 6·fyh·Ash/sv·h0
V = 0.7*(8-2)/3*1433*0.2*0.5625+1.25*(2-2)/3*210*100/200*0.5625
+(5-2)/6*300*0.5*0.5625 = 267.9kN
1.3.2 T形截面深受弯构件,其受剪截面应符合下式条件:
hw = h0 - hf' = 562.5-100 = 462.5mm,
当 hw/b ≤ 4 时,V ≤ (10 + l0/h) / 60·βc·fc·b·h0
Rv = 0.2·βc·fc·b·h0 = 0.2*1*14331*0.2*0.5625
= 322.5kN ≥ V = 267.9kN,满足要求。
1.3.3 Asv = 100mm,箍筋最小直径 φ6,最大间距 @250
Ash/sv = 0.500mm,当 sv = h 时,Ash = 300mm