抗拔桩计算书
排气筒基础抗拔桩计算书
1、 确定桩型、截面尺寸及桩长
选用人工挖孔桩、桩径800,嵌入中风化砂岩3m 承台埋深2m 1.1确定桩的竖向受压承载力
=4μ=πD =0.8π=2.5m A p =πD /4=π0. 8/
2
2
0m . 5
2
扩大头面积:A p 1=πD 1/4=π1.6/4=2m
Q sk =μ∑ψsi q si l i =2.5⨯1⨯(0.8⨯22+95⨯1.4) =376.5KN Q pk =ψp q pk A p =1.0⨯3000⨯2=6000KN
222
基桩受压承载力设计值:R =Q sk /γs +Q pk /γp =376/1.65+6000/1.65=3864KN 1.2确定桩的竖向抗拔承载力
考虑桩扩大头作用,将其视为固结于砂岩内,按桩的强度设计抗拔。
1.3 确定单桩水平承载力
ρg =0. 88% d 0=800-80=
πd 32
[d +2(αE -1) ρg d 0]=
2
2
7m 20m αE =
2
E s E c
=
2. 0⨯103. 0⨯10
24
5
=6. 7
W 0=
0.8π32
[0.8+2(6.7-1) ⨯0.88%⨯0.72]=0.054m
3
4 I 0=W 0d /2=0.054/2=0.022m
I = E I =0. 85E c 0
0. 8⨯5⨯3
7
1⨯00. =022⨯5. 6K 1N m 10
4
-3
52
b 0=0.9(1.5d +0.5) =1.53m 查表5.4.5取 m =100MN /m χoa =6⨯
10m
α=
=
53
=0. 77 m
1
αh =0. 77⨯1=32
查表5.4.2取 νm =0.601 νx =3. 52 6
R h =
αE I νx
3
χoa =
0.771⨯5.61⨯10
3.526
35
⨯6⨯10
-3
=437.5K N
2、 确定桩桩数,及桩的平面布置 2.1桩的平面布置
桩中心距:2.5⨯1.8=2m 取 2m
承台尺寸:4.0x4.0m 承台埋深2m 2.2受压最大时
F k =2900KN F y =-767K N
M
xk
=F y h =767⨯2=1534K N m
n ≥
F +G N
=
1. 25(29+00⨯20⨯4. 64. 6)
=2 取 n =4
2079
2.3 偏心受压验算 N i =
F +G n
±M x y i ∑y i
2
±
M y x i ∑x i
2
=
1. 2⨯5(29+00⨯
4
2⨯2⨯0
4
±
4) ⨯1. 2⨯5
2
15341. 2
4⨯1. 2
=1106±400=
1506606
满足要求 2.4 抗拔验算
4N F k =-2310KN F y =530. K
M
x k
=F y h =
⨯=K N m
N i =
F +G n
±
M x y i ∑y i
2
±
M y x i ∑x i
2
=
-1.25⨯2310+2⨯20⨯4⨯4
4
±
1.25⨯1060.8⨯1.2
4⨯1.2
2
=-562±276=
-286-838
1.25⨯767
4
2.5 水平承载力验算 单桩水平承载力:H 1=满足要求
3、 桩配筋计算
3.1受压时 材料C25混凝土 HRB335级钢筋
N =1506K N
3
N /ψc =1506/0.9=1673KN
5355KN
=240K N γ0H 1
按构造配筋
3.2受拉时
N =838K N N /ψc =838/0=. 9
K 93N 1 A s =
N f y
=
931⨯10002
=3103m m
300
选配A S =4000mm 3.3、 裂缝验算
E S =2.0X105N/mm2 E c =2.8X104N/mm2 A S =4000mm2 σSK =
N K A S
=
952⨯10
3
2
1.25⨯4000
=190.4N /m m
2
A te =A p =0.5m ρte =
f tk
2
A S A te
=
40000.5⨯10
6
=0.8% d eq =
∑n i d i
2
∑n i d i
=20m m
2
ψ=1.1-0.65
ρte σsk
=1.1-0.65⨯
1.780.8%⨯190.4
190.42.0⨯10
5
=0.34
ωmax =αcr ψ
σsk
E s
(1.9c +0.08
d eq
ρte
) =2.7⨯0.34⨯⨯(1.9⨯40+0.08⨯
201.2%
) =0.183m m
ωm
a x