BÀI TẬP LỚN CHUYÊN ĐỀ 1-CHUYÊN ĐỀ 1-HƯỚNG DẪN PHÂN TÍCH VÀ TÍNH TOÁN HỆ CHỊU LỰC CHO CÔNG TRÌNH DÂN DỤNG BẰNG BÊ TÔNG CỐT THÉP

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 1

CHUYÊN ĐỀ 1: “HƯỚNG DẪN PHÂN TÍCH VÀ TÍNH
TOÁN HỆ CHỊU LỰC CHO CÔNG TRÌNH DÂN DỤNG
BẰNG BÊ TÔNG CỐT THÉP”

A. PHN THÂN:
I. Ch c cu kin:
1. Chiu dày bn:
T s gia hai cnh ca bn: L
2
/L
1
n kê 4
cnh. Chiu dày bc chn theo công thc kinh nghi





















  
n chiu dày bn: h
b
= 0.1m = 10cm.
2. Chn tit din dm ph:





















  
n chiu cao dm ph: h
dp
= 0.3m




















  
n chiu rng dm ph: b
dp
= 0.2m
3. Chn tit din dm chính:





















  
n chiu cao dm chính: h
dc
= 0.5m





















  
n chiu rng dm chính: b
dc
= 0.2m
4. Chn tit din ct:
Din tích tit din ct c chn s b theo công thc sau:
F
yc
= k
t
N/R
b
, trong :
 k
t
là h s ph thuc vào mômen un, hàm ng ct thép mnh ca

ct. Chn k
t
= 1.3
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 2

 N là lc nén, tính g nh sau: N = m
s
qF
s
, vi:
 m
s
là s sàn trên tit diang xét(k c sàn mái), m
s
= 4
 q là ti trng tng ng tính trên mi mét vuông mt sàn. Trong
 gm có ti trng thng xuyên và ti trng tm thi lên bn
sàn; trng lng ca dm, tng, cem tính ra phân bu trên
sàn. Theo kinh nghim thit k thìi vi nhà có chiu dày sàn
bé(10÷14 cm), cóít tng, kích thc ct dm bé thìq = 1÷1.4T/m
2

 F
s
là din tích mt sàn truyn ti trng lên cang xét.
 R
b
là c chu nén tính toán ca bê tông. Chn bê tông mác

250(B20) có R
b
= 1150T/m
2


Hình 1. Mt bng tng mt công trình.
 Ct trc A:
F
s
= 3.9x0.5x2.1 = 4.095m
2

N = 4(1÷1.4)4.095 = (16.38÷22.932)T
F
yc
= 1.3(16.38 ÷ 22.932)/1150 = (0.019 ÷ 0.026)m
2
= (190 ÷ 260)cm
2

n kích c tit din ct trc A nh sau: t tng n tng 4
bxh = 20x30cm( F = 600cm
2
)
 Ct trc B:
F
s
= 3.9x0.5(6.6 + 2.1) = 16.965m
2

N = 4(1 ÷ 1.4)16.965 = (67.86 ÷ 95.004)T
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 3

F
yc
= 1.3(67.86 ÷ 95.004)/1150 = (0.077 ÷ 0.107)m
2
= (770 ÷ 1070)cm
2

n kích c tit din ct trc A nh sau: t tng n tng 2bxh
= 20x50cm(F = 1000cm
2
), t tng  n tng 4 bxh = 20x40cm(F =
800cm
2
)
 Ct trc C:
F
s
= 3.9x0.5x6.6 = 12.87m
2

N = 4(1 ÷ 1.4)12.87 = (51.48 ÷ 72.072)T
F
yc
= 1.3(51.48 ÷ 72.072)/1150 = (0.058 ÷ 0.081)m

2
= (580 ÷ 810)cm
2

n kích c tit din ct trc C nh sau: t tng n tng 2
bxh = 20x40cm(F = 800cm
2
), t tng n tng 4 bxh = 20x30cm(F =
600cm
2
)
II. La chn vt liu:
 i vi bê tông: chn bê tông mác 250(B20) có:
R
b
= 1150 T/m
2
, E
b
= 2.7x10
6
T/m
2

 i vi ct thép:
Ct dc dùng nhóm CII có: R
s
= R
sc
= 28000 T/m

2
, E
s
= 2.1x10
7
T/m
2

Cai dùng nhóm CI có: R
s
= R
sc
= 22500 T/m
2
, E
s
= 2.1x10
7
T/m
2

III. nh ti trng:
1. Tnh ti sàntng2,3,4:
Các lớp cấu tạo
Chiều dày(m)
γ (kg/m
3
)
HSVT
q

tt
(kg/m
2
)
Sàn lát gch hoa 200x200
0.02
1800
1.1
39.6
Va lót XM mác 50 dày
0.015
1600
1.2
28.8
Sàn BTCT
0.1
0(máy tính)
1.1
0
Va trát trn XM mác 75
0.015
1800
1.2
32.4
q
tt
=
100.8

2. Tnh ti sàn mái:

Các lớp cấu tạo
Chiều dày(m)
γ (kg/m
3
)
HSVT
q
tt
(kg/m
2
)
Mái lp tôn sóng vuông
4.2x10
-4

7850
1.1
3.627
Xà g thép C
1.8x10
-3

7850
1.1
15.543
Sàn BTCT
0.1
0(máy tính)
1.1
0

Va trát trn XM mác 75
0.015
1800
1.2
32.4
q
tt
=
51.57
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 4

3. ng:
Loại tường
Dày(m)
γ (kg/m
3
)
C.cao(m)
HSVT
q
tt
(kg/m)
Trc 1,7,8
0.2
1800
3.4
1.1
1346.4

Trc 3,5
0.135
1600
3.4
1.1
807.84
Trc A
0.2
1800
1
1.1
396
Trc B
0.135
1600
3.6
1.1
855.36
Trc C
0.2
1800
3.6
1.1
1425.6
ng thu hi
0.135
1600
0.8
1.1
190.08

ng thu hi
0.135
1600
0.35
1.1
83.16
ng cao 1.2m
0.2
1800
1.2
1.1
475.2

4. Bc ging:
Các lớp cấu tạo
Chiều dày(m)
γ (kg/m
3
)
HSVT
q
tt
(kg/m
2
)
Gch hoa 200x200
0.02
1800
1.1
39.6

Va XM mác 50
0.03
1600
1.2
57.6
BT  4x6 mác 50
0.09
2200
1.1
217.8
Cát m k
0.08
1500
1.1
144
q
tt
=
459

Din tích bc ging:
S
bg
= (0.75x3.4) + 0.5(1.35 + 0.75)0.6 + 1.35x1.7 = 5.475m
2

Din tích sàn phòng hc:
S
ph
= (3.9x2  0.1675)(6.6  0.1675) = 49.096m

2

Ti trng bc ging: P
bg
= 459x5.475 = 2513.025kg
Ti trng ca bc ging c quy v ti trng phân b u trên sàn:
q
bg
= 2513.052//49.096 = 51.186kg/m
2

5. Hot ti sàn:
Loại hoạt tải
HSVT
q
tc
(kg/m
2
)
q
tt
(kg/m
2
)
Phòng hc
1.2
200
240
Snh hành lang
1.2

300
360
Mái tole
1.3
30
39

6. Tnh ti cu thang:
Bn thang BTCT: 4.096x1x0.1x2500x1.1 = 1126.4kg
Bc xây gch c: (0.06 + 0.21)x0.3x0.5x1x1600x12x1.1 = 855.36kg
Mt bc láng granito: (0.17 + 0.28)x0.02x1x56x12x1.1 = 6.653kg
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 5

Thành: 0.1x0.9x4.096x1600x1.1 = 648.806kg
 P
ct
= 1126.4 + 855.36 + 6.653 + 648.806 = 2637.219kg
7. Hot ti cu thang:
P
ct
= 350x12x1x0.3x1.2 = 1512kg
8. Hot ti gió:
Công thc tính hot ti gió:W
tt
= 3.9nW
0
kc, vi
 3.9 là chiu cao mi tng ca công trình

 n là h s vt ti, ly n = 1.2
 W
0
làáp lc gió tiêu chun, ph thuc vim khí hu ca tng
vùng. Gi s công trc xây dng vùng Áp lc gió tiêu
chun W
0
= 0.125T/m
2

 k là h s thay iáp lc gió theo  cao, c xnh theo bng sau
z(m)
4.1
8
11.9
15.8
k
0.868
0.966
1.04
1.094

 c là h s khng, ly bng 0.8 i vi giy và 0.6 i vi gió hút.
T, ta có bng tính hot ti gió nh sau:
z(m)
Gió đẩy(T/m)
Gió hút(T/m)
4.1
0.406
0.305

8
0.452
0.34
11.9
0.487
0.365
15.8
0.414
0.31











BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 6

A.  C3:
I. 
1. 




N(T)
M(Tm)
Q(T)
N(T)
M(Tm)
Q(T)
64.812
9.633
3.533
54.01
8.028
2.944

2. 
3. :





(g/cm
3
)



trong 


c(kg/cm

2
)

nhiên
W
nh
W
d


(h=3.7m)
2.7
1.68
26.2
32.2
22.55
16.633°
0.18

4. 



i

i
(kg/cm
2
)

P
1
= 1
P
2
= 2
P
3
= 3
P
4
= 4
e
o

e
1

e
2

e
3

e
4



(h=3.7m)

1.029
0.962
0.921
0.902
0.889

II. 

III.  C3:
1. 
- : R
b
= 11.5 MPa = 1150 T/m
2

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 7

R
bt
= 0.9 MPa = 90 T/m
2

- R
SW
= 175 MPa = 17500 T/m
2

-         

S
= R
SC
= 280 MPa =
28000 T/m
2

2. 




m
= 1.7m
3. 
:












TCXD 45-78:
R

TC
=







m

TC
)

- m
1


1
= 1.2
- m
2

2
= 1.1
- k
tc

- 
A = 0.382 B = 2.522 D = 5.098

- 

3
= 1.68 T/m
3

- c
TC

TC
= 0.18 kg/cm
2
= 1.8
T/m
2

- h
m

m
= 1.7 m
- 
 R
TC
=


( 0.382x2x1.68 + 2.522x1.7x1.68 + 5.098x1.8 ) = 23.315 T/m
2

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 8

      
yc
= axb =















tb

.

yc
/b = 2.759/2 = 1.38

2

> 2.736 m
2
= F
yc

 = 2.2/2 = 1.1
4. 
:


















 













 








 

 











 








e
x

e
y
, e
y
= 0
e
x
=











 0.241 m



= 16.015( 1 + (6x0.241)/2.2 + 0 ) = 26.541 T/m
2

























2


5. 
 [S
gh
] = 8 cm
 







- :

z=0
= 1.68x1.7 = 2.856 T/m
2
= 0.286 kg/cm
2

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 9


z=2.5

= 2.856 + 1.68x2.5 = 7.056 T/m
2
= 0.706 kg/cm
2

- : 
gl
= 16.015  1.68x1.7 = 13.159 T/m
2
= 1.316 kg/cm
2

- 
i

i
= 50 cm
- : 
zi
= k
oi
x
gl
, k
oi


i
 = a/b = 1.1
- 8 


z
= 0.155 kg/cm
2
< 0.2
bt
= 0.192 kg/cm
2


a
= 4m




sâu
zi
(cm)
2zi/b

k0i

zi
kg/cm
2


bt
kg/cm

2

P
1i
kg/cm
2

P
2i
kg/cm
2

e
1i

e
2i

S
i
cm



0
0
0.0
1.1
1.00
0

1.316
0.286
0.328
1.600
1.00
5
0.93
4
1.771
1
50
0.5
1.1
0.93
3
1.228
0.37
0.412
1.500
1
0.93
8
1.550
2
100
1.0
1.1
0.72
1
0.949

0.454
0.496
1.306
0.99
4
0.94
6
1.204
3
150
1.5
1.1
0.51
0
0.671
0.538
0.58
1.151
0.98
8
0.95
4
0.855
4
200
2.0
1.1
0.35
8
0.471

0.622
0.664
1.070
0.98
2
0.95
8
0.605
5
250
2.5
1.1
0.25
9
0.341
0.706
0.748
1.045
0.97
7
0.96
0.430

6
300
3.0
1.1
0.19
3
0.254

0.79
0.832
1.057
0.97
2
0.95
9
0.330
7
350
3.5
1.1
0.14
9
0.196
0.874
0.916
1.092
0.96
7
0.95
7
0.254
8
400
4.0
1.1
0.11
8
0.155

0.958
S = 
6.999


P
1i
= 0.5(





) P
2i
= 0.5(
zi-1
+ 
zi
) + P
1i

P
1i
, P
2i
 e-p
S
i
=




 



 


BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 10


-p


6. :


nghiêng .
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 11

P
cth
< 0.75xR
k

xU
tb
xh
0
(*), trong 
- P
cth
, P
cth
= N
0
- rxF
cth

+ F
cth

F
cth
= a
cth
xb
cth
= (a
c
+2h
0
tg)(b
c
+2h

0
tg) = (a
c
+2h
0
)(b
c
+2h
0
), tg45° = 1


e
x
= (9.633 + 3.533x1.7)/64.812 = 0.241 m ; e
y
= 0
:

max,min
= (64.812/(2.2x2))(1 6x0.241/2.2) =










r
1
= 

+ ((a  0.25(a  a
c
))(



/a) = ((2.2  0.25(2.2 
0.4))(24.412 5.048)/2.2) + 5.048 = 20.451 T/m
2

r
2
= 



0.5 = (24.412 + 5.048)0.5 = 14.73 T/m
2

 r = r
2

- R
k
: R

k
= 90 T/m
2

- U
tb
: U
tb
= 0.5(U
t
+ U
d
)
U
t
= 2(a
c
+ b
c
); U
d
= 2(a
cth
+ b
cth
) = 2(a
c
+ b
c
+ 4h

0
)

tb
= 2(a
c
+ b
c
+ 2h
0
)

328.92(h
0
)
2
+ 98.676h
0
 63.634  0

0
:









0
= 0.55 m, thay h
0

 64.812  14.73(0.4 + 2x0.55)(0.2 + 2x0.55)  0.75x90x2(0.4 + 0.2 +
2x0.55)0.55


0
+ 0.05 = 0.55 + 0.05 = 0.6 m
7. 

- 
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 12

- 
0
, h
0

h
0
= 0.55 m

F
a
= M

td
/0.9h
0
xm
a
xR
a

- m
a

a

a
=
0.9
- R
a

a
= 28000 T/m
2


M
I-I
= 0.125r
1
b(a-a
c

)
2
= 0.125x20.451x2(2.2  0.4)
2
= 16.565 Tm
M
II-II
= 0.125r
2
a(b-b
c
)
2
= 0.125x14.73x2.2(2  0.2)
2
= 13.124 Tm

 -I:
F
a
= 16.565/(0.9x0.55x0.9x28000) = 1.328x10
-3
m
2
= 13.28 cm
2

12( F
12
= 1.131 cm

2
 
12
 
 -II:
F
a
= 13.124/(0.9x0.55x0.9x28000) = 1.052x10
-3
m
2
= 10.521 cm
2

12( F
12
= 1.131 cm
2

12
3 cm = 230 mm
B. 
I. 
1. 


2. 

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 13


N(T)
M(Tm)
Q(T)




12.904
3.532
1.199




10.753
2.943
0.999




73.974
14.309
4.488





61.645
11.924
3.74


:


M/
0
= 0  5.57 + 21.939 12.904a + 73.974b = 0
2.1
:

II. 
1. 
- 
b
= 11.5 MPa = 1150 T/m
2

R
bt
= 0.9 MPa = 90 T/m
2

- 
SW
= 175 MPa = 17500 T/m
2

-         
S
= R
SC
= 280 MPa =
28000 T/m
2

2. 


BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 14



m
= 1.7m
3. 














TCXD 45-78:
R
TC
=







m

TC
)

- m
1


1
= 1.2

- m
2

2
= 1.1
- k
tc

- 
A = 0.382 B = 2.522 D = 5.098
- 

3
= 1.68 T/m
3

- c
TC

TC
= 0.18 kg/cm
2
= 1.8
T/m
2

- h
m

m

= 1.7 m
- 
 R
TC
=


( 0.382x2.2x1.68 + 2.522x1.7x1.68 + 5.098x1.8 ) = 23.484 T/m
2

      
yc
= axb =















tb




yc
/b = 3.667/2.2 = 1.6673 m
3 = 6.6 m
2
>3.667 m
2
= F
yc

 = 3/2.2 = 1.369
4. 
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 15

:


















 












 








 


 










 








e
x
, e
x
= 0
e
y

y
= 0




= 14.706( 1 + 0 + 0 ) = 14.706T/m
2























3x2.2 m
2



5. 
 [S
gh
] = 8 cm








- 

z=0
= 1.68x1.7 = 2.856 T/m
2
= 0.286 kg/cm
2


z=2.5
= 2.856 + 1.68x2.5 = 7.056 T/m
2
= 0.706 kg/cm
2

- 

gl
= 14.706  1.68x1.7 = 11.85 T/m
2
= 1.185 kg/cm
2

- 
i
= (0.2  0.4)b = (44  88
i
= 50 cm
- 
zi
= k
oi
x
gl
, k
oi


i
 = a/b = 1.369
- 9

z
= 0.162 kg/cm
2
< 0.2
bt

= 0.208 kg/cm
2


a
= 4.5 m


BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 16




2zi/b

k0i

zi
(kg/cm
2
)

bt
(kg/cm
2
)
P
1i

(kg/cm
2
)
P
2i
(kg/cm
2
)
e
1i

e
2i

S
i
(cm
)



0
0
0.000
1.364
1.000
1.185
0.286
0.328
1.487

1.00
5
0.93
8
1.671
1
50
0.455
1.364
0.956
1.133
0.370
0.412
1.452
1
0.94
1.500
2
100
0.909
1.364
0.799
0.947
0.454
0.496
1.331
0.99
4
0.94
5

1.229
3
150
1.364
1.364
0.611
0.724
0.538
0.58
1.213
0.98
8
0.95
1
0.931
4
200
1.818
1.364
0.457
0.542
0.622
0.664
1.139
0.98
2
0.95
5
0.681
5

250
2.273
1.364
0.345
0.409
0.706
0.748
1.110
0.97
7
0.95
6
0.531

6
300
2.727
1.364
0.266
0.315
0.790
0.832
1.113
0.97
2
0.95
6
0.406
7
350

3.182
1.364
0.208
0.246
0.874
0.916
1.138
0.96
7
0.95
5
0.305
8
400
3.636
1.364
0.167
0.198
0.958
1
1.180
0.96
2
0.95
3
0.229
9
450
4.091
1.364

0.137
0.162
1.042
S = 
7.482


P
1i
= 0.5(





) P
2i
= 0.5(
zi-1
+ 
zi
) + P
1i

P
1i
, P
2i
-p
S

i
=



 



 


BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 17



6. 




cth
< 0.75xR
k
xU
tb
xh
0


- P
cth

cth
= N
0
- rxF
cth

+ F
cth

F
cth
= a
cth
xb
cth
= (a
c
+2h
0
tg)(b
c
+2h
0
tg) = (a
c
+2h

0
)(b
c
+2h
0
), tg45° = 1

e
x
= 0; e
y
= 0


max,min
= (86.878/(2.2x3))(1 0) =










BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 18


max,min
= r = 13.163 T/m
2

- R
k

k
= 90 T/m
2

- U
tb

tb
= 0.5(U
t
+ U
d
)
U
t
= 2(a
c
+ b
c
); U
d
= 2(a

cth
+ b
cth
) = 2(a
c
+ b
c
+ 4h
0
)

tb
= 2(a
c
+ b
c
+ 2h
0
)

322.652(h
0
)
2
+ 112.928h
0
 85.562 0

0
:










0
= 0.55 m, thay h
0

 86.878  13.163(0.5 + 2x0.55)(0.2 + 2x0.55)  0.75x90x2(0.5 + 0.2 +
2x0.55)0.55
59.499 T < 133.65

0
+ 0.05 = 0.55 + 0.05 = 0.6 m
7. 
 -I:
M
I-I
= 13.163x2.2x0.95
2
x0.5 = 13.068 Tm
F
I-I
= 13.068/(0.9x0.55x0.9x28000) = 1.05x10
-3

m
2
= 10.5 cm
2


12
= 1.131 cm
2


-
 -II:
M
II-II
= 0.125x13.163x3(2.2-0.2)
2
= 19.745 Tm
F
II-II
= 19.745/(0.9x0.55x0.9x28000) = 1.583x10-3 m
2
= 15.83 cm
2


12
= 1.131 cm
2

15.83/1.131 = 13.94 thanh
300-10)/13 = 22.307
 


tb


BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 19




M/
B

A
= 33.096 T
M/
A

B
= 53.381 T
 
M
A
= 28.959*0.2
2

*0,5 = 0.579 Tm
M
B
= 28.959*0.7
2
*0,5 = 7.095 Tm
 
M

= 28.959*1.25
2
*0.5  33.0968*1.05 = -12.127 Tm

F

= 12.127/(0.9*0.55*0.9*28000) = 9.722x10
-4
m
2
= 9.722 cm
2


2

 = 11.4*10
-4
x100%/(0,55*0.2) = 1.036 %
F
max

= 
R
.R
B
.b.h
0
= 0.623*11.5*200*550/280 = 2814.625 mm
2
= 28.146 cm
2


max
= 28,146*10
-4
x100%/(0,55*0.2) = 2.559 %

min
= 0.05 % <  = 1.036 % < 
max
= 2.559 %


F

= 7.095/(0.9*0.55*0.9*28000) = 5.688x10
-4
m
2
= 5.688 cm

2


2

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 20

 = 7.64*10
-4
x100%/(0,55*0.2) = 0.7 %

min
= 0.05 % <  = 0.7 % < 
max
= 2.559 %

C. 
I. 
1. 



N(T)
M(Tm)
Q(T)
N(T)
M(Tm)
Q(T)

46.148
10.15
3.655
38.457
8.458
3.046

2. 
II. 
1. 
- 
b
= 11.5 MPa = 1150 T/m
2

R
bt
= 0.9 MPa = 90 T/m
2

- 
SW
= 175 MPa = 17500 T/m
2

-         
S
= R
SC
= 280 MPa =

28000 T/m
2

2. 

t


m
= 1.7m
3. 













-78:
R
TC
=








m

TC
)

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 21

- m
1


1
= 1.2
- m
2

2
= 1.1
- k
tc

-  
A = 0.382 B = 2.522 D = 5.098

- 

3
= 1.68 T/m
3

- c
TC

TC
= 0.18 kg/cm
2
= 1.8
T/m
2

- h
m

m
= 1.7 m
- 
 R
TC
=


( 0.382x1.8x1.68 + 2.522x1.7x1.68 + 5.098x1.8 ) = 23.145 T/m
2

      
yc
= axb =















tb



yc
/b = 1.982/1.8 = 1.1012.5 m
5x1.8 = 4.5 m
2
>1.982 m
2
= F
yc

 = 2.5/1.8 = 1.389
4. 
:


















 













 








 

 










 









e
x

e
y

y
= 0
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 22

e
x
=











 0.355 m



= 12.286( 1 + (6x0.355)/2.5 + 0 ) = 22.754T/m
2
























5x1.8 m
2


5. 
 [S
gh
] = 8 cm








- 

z=0
= 1.68x1.7 = 2.856 T/m
2
= 0.286 kg/cm
2


z=2.5
= 2.856 + 1.68x2.5 = 7.056 T/m
2
= 0.706 kg/cm
2

- 
gl
= 12.286 1.68x1.7 = 9.43 T/m
2
= 0.943 kg/cm
2

- 
i
= (0.2  0.4)b = (36  72
i
= 50 cm
- 
zi
= k
oi
x
gl
, k
oi


i
 = a/b = 1.389
- 7 

z
= 0.142 kg/cm
2

< 0.2
bt
= 0.175 kg/cm
2


a
= 3.5 m





2zi/b

k0i

zi
(kg/cm
2
)

bt
(kg/cm
2
)
P
1i
(kg/cm
2

)
P
2i
(kg/cm
2
)
e
1i

e
2i

S
i
(cm
)




0
0
0.000
1.38
9
1.000
0.943
0.286
0.328
1.238

1.00
5
0.95
1.372
1
50
0.556
1.38
9
0.931
0.878
0.370
0.412
1.189
1
0.95
2
1.200
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 23

g
2
100
1.111
1.38
9
0.717
0.676

0.454
0.496
1.074
0.99
4
0.95
6
0.953
3
150
1.667
1.38
9
0.509
0.480
0.538
0.58
0.989
0.98
8
0.96
3
0.629
4
200
2.222
1.38
9
0.359
0.339

0.622
0.664
0.956
0.98
2
0.96
5
0.429
5
250
2.778
1.38
9
0.261
0.246
0.706
0.748
0.963
0.97
7
0.96
4
0.329


6
300
3.333
1.38
9

0.196
0.185
0.790
0.832
0.996
0.97
2
0.96
3
0.228
7
350
3.889
1.38
9
0.151
0.142
0.874
S = 
5.139


P
1i
= 0.5(






) P
2i
= 0.5(
zi-1
+ 
zi
) + P
1i

P
1i
, P
2i
-p
S
i
=



 



 




6. 


x
= (10.15 + 3.655*1.7)/46.148 = 0.355 m; e
y
= 0

BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 24


max,min
= (46.148/(2.5x1.8))(1 6x0.355/2.5) =










r
1
= ((a  0.25(a  a
c
))(




/a) + 
min

= ((2.2  0.25(2.5  0.4))(18.992  1.518)/2.5) + 1.518 = 15.322 T/m
2

r
2
= 



0.5 = (18.992 + 1.518)0.5 = 10.255 T/m
2


2

- R
k

k
= 90 T/m
2

- U
tb

tb

= 0.5(U
t
+ U
d
)
U
t
= 2(a
c
+ b
c
); U
d
= 2(a
cth
+ b
cth
) = 2(a
c
+ b
c
+ 4h
0
)

tb
= 2(a
c
+ b
c

+ 2h
0
)

0

P
cth
= 46.148  10.255(0.4 +2*0.55)(0.2 + 2*0.55) = 34.611 T
0.75R
k
U
tb
h
0
= 0.75*90*[2(0.4 + 0.2) + 3*0.55]0.55 = 105.806 T
  
cth
= 34.611 T< 0.75R
k
U
tb
h
0
       
0
 


H

m
= 0.55 + 0.05 = 0.6 m
7. 

- 
- 
0
, h
0

h
0
= 0.55 m

F
a
= M
td
/0.9h
0
xm
a
xR
a

- m
a

a


a
=
0.9
- R
a

a
= 28000 T/m
2


M
I-I
= 0.125r
1
b(a-a
c
)
2
= 0.125x15.322x1.8(2.5  0.4)
2
= 15.203 Tm
BÀI TP L 1 GVHD: Th.S PHC

NHÓM 8 25

M
II-II
= 0.5r
2

a(b-b
c
)
2
= 0.5x10.255 x2.5(1.8 0.2)
2
= 32.816 Tm

 -I:
F
a
= 15.203/(0.9x0.55x0.9x28000) = 1.219x10
-3
m
2
= 12.19 cm
2

12( F
12
= 1.131 cm
2
12.19/1.131 = 10.778
1 thanh 12
180  2x5)/10 = 17 cm = 170 mm
 -II:
F
a
= 32.816/(0.9x0.55x0.9x28000) = 2.631x10
-3

m
2
= 26.31 cm
2

12( F
12
= 1.131 cm
2
 26.31/1.131 = 23.26
24 thanh 12
50  2x5)/23 = 10.43410 cm = 100 mm