f=0.89×1.93=1.718MPa
N=φfA=0.686×1.718×0.19×103×1000=223.9×103N=223.9kN
4.解：(1)截麵幾何特征。窗間牆截麵麵積
A=0.24×2+0.5×0.49=0.725m2>0.3m2
截麵重心位置
y1=2×0.24×0.12+0.49×0.5×(0.24+0.25)0.725=0.245m=245mm
y2=500+240-245=495mm
截麵慣性矩
I=2×0.24312+2×0.24×(0.245-0.12)2+0.49×0.5312+0.49×0.5×(0.495-0.25)2=0.0296m4
截麵回轉半徑
i=IA=0.02960.725=0.202m=202mm
T形截麵折算厚度
hT=3.5i=3.5×202=707mm
(2)影響係數。偏心矩
e=MN=70600=0.117m=117mm3，取ψ=0。
砌體的局部抗壓強度提高係數
γ=1+0.35A0Al-1=1+0.35×4.47-1=1.650.7
高厚比β=
H0
h
=
3500
370
=9.46205.5kN(4分)
安全。(1分)
4.解：(1)基礎底麵積初估
A≥1.2×
Fk
fa-γGd
=1.2×
650
200-20×1.8
=4.75m2(2分)
取基礎寬b=1.8m，基礎長l=2.7m
則基礎底麵積A=1.8×2.7=4.86m2(2分)
截麵抵抗矩W=
1
6
bl2=
1
6×1.8×2.72=2.18m2(1分)
基底壓應力
pkmax=
Fk+Gk
A
+
Mk
W
=
650+20×1.8×4.86
4.86
+
32
3.187
=184.38kN/m23，所以ψ=0。(2分)
ηγA1f=0.7×235200×1.3=64064N>Nl=60000N(6分)
安全。(2分)