Thuyet Minh Do an BTCT(Dang)New

8/4/2019 Thuyet Minh Do an BTCT(Dang)New

1/39

n B tng ct thp GVHD: Th.s Trn Anh Thin

THUYT MINH N MN HC KT CU BTNG CT THP

I) Tm tt nhim v thit k :

Thit k sn B tng ct thp kiu sn sn ton khi c bn loi dm

II) S liu cho trc:

a)S sn:

1b1a 54321

D

C

B

A

6800

6800

6800

750075007500250025002500

H.1:S sn

b)Hot ti tiu chun : P tc = 7,9 (KN/m2)

III) Phn tnh ton thit k:

*)Chn phng n mt sn v kt cu mt sn

+Phng n mt sn:

- S sn (hnh v H.1)

- Kch thc : l1=2,8 (m) , l2=6,4 (m) , dy tng t=34 (cm)

+Kt cu sn:

- Lp va xi mng dy 2(cm) bn trn bn

- Bn btng ct thp

- Lp trt bn di dy 1 (cm) bn di bn- Dm ph btng ct thp 3 nhp


2/39

n B tng ct thp GVHD: Th.s Trn Anh Thin- Dm chnh b tng ct thp 4 nhp

*)Phn tnh ton c th:

1)Chn vt liu v cc ch tiu k thut ca vt liu:

+ B tng cp bn B15 : Rb = 8,5.103(KN/m2)

Rbt= 750 (KN/m2)

+ Ct thp : AI : Rs=Rsc=225.103(KN/m2) ; Rsw= 175.103(KN/m3)

AII : Rs=Rsc=280.103(KN/m2) ; Rsw= 225.103(KN/m3)

2)Tnh ton bn:

2.1)Kim tra phng lm vic ca bn:

Ta c l1=2,5(m) v l2=6,8 (m) >2xl1=5(m) nn bn ch yu lm

vic theo phng cnh ngn , nh vy y l loi sn sn ton khi c bn loi dm ,

cc trc (B),(C) l dm chnh cc trc nh k t s l dm ph ( 1a ; 1b ; 2;... ; 3; ... ; 4; ... ).

2.2)La chn s b kch thc cc b phn:

a) Kch thc bn:

tnh ton bn ta ct mt di bn rng 1m theo phng lm vic ca bn (theo phng l1) ,

chn chiu cao bn theo cng thc : bD

h lm

= ; vi l chiu di nhp bn 1 250( )l l cm = ; D l

h s ph thuc ti trng 0,8 1, 4D = v hot ti tc dng ln bn kh ln P tc = 8,0 (KN/m2)nn ta chn D=1,2 ; m l h s ph thuc vo kt cu ca bn ,m=35 (bn loi dm lin tc).

1,2250 8,57

35bD

h lm

= = = (cm) => chn hb=9(cm)

m bo iu kin min 6( )bh h cm = (i vi nh dn dng )

b)Kch thc dm ph:1

dp dd

h lm

= vi md l h s ph thuc s

dm v ti trng ta chn md=15 (khng ln qu v ti trng ln) ; ld nhp

ca dm ang xt 2 680( )dl l cm = nn:1 1

.680 45,33( )15dp dd

h l cmm

= = = => chn

hdp=50(cm) , b rng dm ph l bdp=20 (cm),


3/39


c)Kch thc dm chnh: tng t1

dc dd

h lm

= vi

13 3 250( )dl l cm = ; md =9 nn =>1 1

750 83, 339dc dd

h lm

= = = (cm)

V vy chn s b hdc=80(cm) ,bdc=30(cm)

2.3) S tnh ton bn:

1 1a 1b 2

90

lllb

t=340t/2

c=hb2

H.2:S bn

+ Chiu di nhp gia:l=l1-bdp=2,5-0,2=2,3 (m)

+ Chiu di nhp bin:lb=l1-bdp/2+hb/2-t/2=2,275(m)

2275 2300 2300

Pb

g

H.3: S ti trng2.4)Ti trng tnh ton bn: (tnh bn theo s khp do)

+Tnh ti:

Cc lp kt cu Tiu chun(KN/m2)H s vt ti

n

Tnh ton

(KN/m2)Va xi mng dy 2 cm c

30 20( / )KN m =

0,4 1,2 0,48

Lp BTCT dy 9 cm c30 25( / )KN m =

2,25 1,1 2,475

Lp va trt dy 1 cm c3

0 18( / )KN m =0,18 1,2 0,216

gb= 3,171

+Hot ti : pb= ptc x n = 8 x 1,2 =9,6 (KN/m2)

+T hp ti trng :q =pb+gb=12,771(KN/m2)

Biu m men theo s khp do:


4/39


2

b1

11ql

111qlb

2

1

16ql

2 2116 ql

2116 ql

H.4:Biu mmen theo s khp do

+ Mmen:

- Cc nhp gia v gi gia: 2 21 1

12,771.2,3 4,222( . )16 16nhg gb

M M ql KN m= = = =

-Cc nhp bin v gi bin: 2 21 1

12,771.2,275 6,009( . )16 11nhb gb b

M M ql KN m= = = =

2.5) Tnh ton ct thp gi v gia nhp bin:

a) S liu c trc:

- B tng cp bn B15 : Rb = 8,5.103(KN/m2)

- Ct thp AI : R s=Rsc=225.103(KN/m2)

- Kch thc tit din : b x h =100 x 9 (cm2)

- Mmen tnh ton : M = 6,009(KN.m)

b) Tnh ton:

Theo TCXD 356-2005: chiu dy lp btng bo v ti thiu trong

bn cho cc kt cu khng nhng ni m t l 10 mm , thp chon l thp

c1

9( )10 b

h mm = , chn thp 8 ,nn chon a =1,5 (cm)

0 9 1,5 7,5( )bh h a cm= = = => 2 3 20

6,0090,126

. . 8, 5.10 .1.(0.075)m b

M

R b h = = =

Kim tra iu kin hn ch :- Vi btng cp bn B15 v ct thp AI th iu kin ph hoi do l

0,446R m = > (ng)

- Tnh ton theo s khp do : 0,126 0, 3m = (ng)

Vy iu hn ch tha mn,

Tac: 0,5(1 1 2 ) 0,932m = + =

23

0

6,009 3.82( ). . 225.10 .0.932.0.075s sMA cm

R h= = =


5/39

n B tng ct thp GVHD: Th.s Trn Anh Thin-Chn thp: Chn 8 => as=0,503 , Nn :

Khong cch:. 0,503.100

13,17( )3,82

s

s

a bs cm

A= = =

Chn cc thanh 8 t cch nhau 130(mm)

- Kim tra gi thit a : c a=10+8/2=14(mm)< gi thit ,Sai s khng ng

k v thin v an ton.

2.6)Tnh ct thp gia nhp gia v gi gia:

a) S liu c trc:

- B tng cp bn B15 : Rb = 8,5.103(KN/m2)

- Ct thp AI : R s=Rsc=225.103(KN/m2)

- Kch thc tit din : b x h =100 x 9 (cm2)

- Mmen tnh ton : M = 4,222(KN.m)

b) Tnh ton:

Theo TCXD 356-2005: chiu dy lp btng bo v ti thiu trong

bn cho cc kt cu khng nhng ni m t l 10 mm , thp chon l thp

c1

9( )10 b

h mm = , chn thp 8 ,nn chon a =1,5 (cm)

0 9 1,5 7,5( )bh h a cm= = =

=> 2 3 20

4,2220,088

. . 8,5.10 .1.(0.075)m b

M

R b h = = =

Kim tra iu kin hn ch :

- Vi btng cp bn B15 v ct thp AI th iu kin ph hoi do l

0,446R m = > (ng)

- Tnh ton theo s khp do : 0, 088 0,3m = (ng)

Vy iu hn ch tha mn,

Tac: 0,5(1 1 2 ) 0,954m = + =

23

0

4,2222.62( )

. . 225.10 .0.954.0.075s s

MA cm

R h= = =

-Chn thp: Chn 6 => as=0,283 (tit din 1 thanh), Nn :

Khong cch:. 0, 283.100

10,8( )

2,62

s

s

a bs cm

A

= = =

Chn cc thanh 6 t cch nhau 105(mm)


6/39

n B tng ct thp GVHD: Th.s Trn Anh Thin- Kim tra gi thit a : c a=10+6/2=13(mm)< gi thit ,Sai s khng ng

k v thin v an ton.

2.7)Tnh chiu di ct thp chu mmen m (trn gi):

Ta c:9,6

3,03 3

3,171

b

b

p

g

= = > ,Nn khong t mp dm ph n mt ct m l

1/ 3l l = ;(=1/3) ,V chiu di nhp bin v nhp gia khng chnh lch nhau nhiu

nn ta c th ly l l chiu di ln hn thin v an ton :l=2,3(m) . Nh vy on di

t mt ct m n trc dm ph l1

.2,3 0,2 / 2 0,87( )3

m+ = on t im un n mp

dm l1 1 1 1

.2,3 .0.2 0,48( )6 2 6 2dp

l b m+ = + = , mc vung di 7cm .

2.8) Ct thp cu to chu mmen m:

a) Ct m theo phng vung gc dm chnh : vng ca ct m cch mp

dm chnh 1/4.l1=1/4.2,3=0,58(m),on mc vung di 7(cm).Chn thp 6 t cch nhau

200(cm) th As=1,41(cm2)>50%As(gianhp)=50%.2,62=1,31(cm2)

v khng t hn 56 trn 1 m di.

b) Ct m ti tng bin : vng ct m cch mp tng 1 on 1/8l1=0,285

(m) , mc vung di 7(cm). Kt hp un thanh 8 gia nhp bin vi khong cch

s=26(cm) un 30o , th :

As=2100 100. .0,503 1.93( )

26sa cm

s= = >50%As(nhb)=1,91(cm2).

2.9)Ct thp phn b - cu to:

Dng cc thanh thp 6 t cch nhau 30(cm) => din tch ct thp trn mt

mp di l As=2100 100

. .0,283 0.94( )30sa cms = = >20%As(gianhp)=0,764(cm2) m bo chu

mmen dng theo phng cnh di (phng l2)

2.10) Hnh v b tr ct thp:


7/39


50

50

5050

50

6060

6 a210

6 a210

6 a210

2500 2500 2500

90

5

6

1

2

3

5

5

58 a260

8 a260

8 a260

6 a210

6 a210

21b1a1

870870

480

360380

30

870870

380380

H.5: S cu to thp trong bn

6 a260

8

90

6 a250

7

575575 300

H.6 :Thp cu to b tr trn dm chnh

3)Tnh ton dm ph:

*)Dm ph k ln dm chnh c b rng bdc=30(cm).Hai u dm ph gi

ln tng vi on k a=22(cm) tha mn quy nh a 20(cm). Chiu dy

tng chu lc t=34(cm).

500

lb=6590

6850

300t=340

a=220

3.1)S tnh ton dm ph:(Theo s khp do )

+ S dm : Dm lin tc 3 nhp .Kch thc b x h =20 x 50 (cm 2)

lb=6590 l=6500 lb=6590


8/39


+Chiu di nhp bin : 2 6,59( )2 2 2dc

b

b t al l m= + =

+Chiu di nhp gia: 2 6,8 0,3 6,5( )dcl l b m= = =

3.2)Ti trng tnh ton:

+Hot ti : 1 9,6 2,5 24( / )dp bp p l KN m= = =

+Tnh ti : 1 0 3,171 2,5 2,255 10,1825( / )dp bg g l g KN m= + = + =

Trong : gb=3,171(KN/m2); l1=2,5(m)

0 ( ) 0,2(0,5 0,09) 25 1,1 2,255( / )dp dp b btct g b h h n KN m= = =

Vi: g0:trng lng bn thn ca dm ph trn 1 n v di

btct: khi lng ring BTCT ly bng 25(KN/m3)

n: h s vt ti n=1,1

A B CD

Pdp=24(KN/m)

Gdp=10,18(KN/m)

6590 6500 6590

+T hp : qdp=gdp+pdp=34,1825(KN/m)

3.3)Tnh ton ni lc:

* Li dng tnh cht i xng ca dm ta ch cn tnh cho 1 na dm

* Theo quy trnh tnh ton kt cu siu tnh bng BTCT c k n s phn phi

li ni lc khi xut hin khp do ca Lin x c cho php tnh mmen i vi dm c nhp

sai khc nhau khng qu 10% cc tit din nh sau:

a) Mmen: Tra bng tnh ton mmen theo s khp do ta c kt qu tnh

ton mmen ln nht v b nht (Mmax) v mmen b nht ti cc tit din:

Bng tra h s min (Bng 10.1, trang 317 Sch kt cu BTCT - Phn cu kin c bn)

Ghi ch :V t s 24 2,3710,1825

dp

dp

pg

= khng c trong bng tra ta dng phng php ni suy.

Tit din max Cng thc Mmax(KN,m) min Mmin (KN.m)0 0

qdplb2

0,001 0,065 96,492 0,090 133,60M 0,091 135,093 0,075 111,344 0,020 29,69

5 0 0,00 -0,0715 -106,146 0,018

qdpl225,95 -0,0322 -46,51

7 0,058 83,76 -0,0112 -16,21N 0,0625 90,26


9/39


* h s( ) 10,1825 24

0,26424

8( ) 8(10,1825 )4 4

g pk

pg

+ += = =

+ + (hnh v)

90,2

6

83,7

6

16,2

1

46,5

1106,1

29,6

9

111,3

4

96,4

9

133,6

135,0

9 25,9

5

0 1 2 M 3 4

5 5 6 7 N

k.l=1,74(m) 0,15lb

H. Biu bao momen dm ph

b)Lc ct:

Tnh ton theo s khp do biu bao ca dm ph (mt na dm) c ly n gin

theo hnh sau vi :

0,4 0,4 34,1825 6,59 90,105( )A dp bQ q l KN = = =

0,6 0,6 34,1825 6,59 135,16( )t

B dp bQ q l KN = = =

0,5 0,5 34,1825 6,5 111,09( )pB dp bQ q l KN = = =

Trong ;t pB BQ Q l lc ct tit din tri ; phi im B

AB

QA

QB

BQ

t

p

3.4)Tnh ton ct thp dc:

Ct thp chu lc AII c Rs=280.103(KN/m2)

Btng cp bn B15 c Rb=8,5.103(KN/m2)

a)Vi tit din chu mmen m (tit din 5- gi B):


10/39

n B tng ct thp GVHD: Th.s Trn Anh Thin+Mmen ln nht : Mmax=106,14(KN.m)

+Cnh nm trong vng chu ko nn khng k n trong tnh ton ,Tit din tnh

ton hnh ch nht vi b = 20 cm ,h = 50 cm gha thit a=4 cm =>

h0 =50-3,5= 46,5 (cm) .(hnh v)

C : 2 3 20

106,14 0,295. . 8,5.10 .0, 2.(0.46)m b

MR b h

= = =

+Kim tra iu kin hn ch:

-Vi Btng cp bn B15 ,ct thp nhm AII suy ra

0,439; 0,650R R = = (Ph lc 8 - Sch kt cu BTCT -

Phn cu kin c bn -2005).

Ta thy : mAs=10,585(cm2)>Astt b tr thnh 2 lp: lp trn

118+216 lp di 216 .

Vi gi thit chn ct thp nh trn ,tnh li gi tr :sA

si iA aa =

vi Asi l din tch ct thpca lp

th i ; ai khong cch t lp ct thp th i mp dm. (hnh v) .Vi trng hp chon ct thp nh

trn ta tnh c a =42,7(mm)>agt=40(mm).V chnh lch b ta c th kim tra li vi h0=h-a=45,73(cm) :

a1

a2

118

416

ho

x

h

b


11/39


2 3 20

106,140,298

. . 8, 5.10 .0, 2.(0.4573)m b

M

R b h = = =

0,5(1 1 2 ) 0,818m = + =

30 0,818.280.10 .0,0010585.0,4573 110,87( . )td s sM R A h KN m= = = >Mmax (m bo),

b)Vi tit din chu mmen dng

Tit din tnh ton c dng ch T vi' 2f cb b S= + ;

trong : { }1min 0,5( );1/ 6 ;9dp fSc l b l h => { }min 1,15;1,08;0,81Sc

Chn Sc=0,81(m)=81(cm);

Nh vy :' 2 20 2.81 182( )f cb b S cm= + = + =

+Vi nhp bin: Mmax=135,09(KN.m) V M

ln nn ta gi thit a=5(cm) suy ra h0=h-a=50-5 = 45

(cm),

Xc nh trc trung ha:

Mf=Rb.b'fh'f(h0-0,5.h'f)=577,8(KN.m)

V M trc trung ha i qua cnh.Nn khi tnh ton ta tnh ton vi tit d in

b'f x h =182x 50 (cm)

2 3 20

135,09 0,043. . 8, 5.10 .1,82.(0.45)m bMR b h

= = =

Tha mn0,439

0,3m R

m d

< = < =

0,5(1 1 2 ) 0,978m = + = =>2

30

135,0910,96( )

. . 280.10 .0,978.0, 45s s

MA cm

R h= = =

Sc=81(cm) Sc=81cm

b

h

h

b

f

f'

'


12/39


Hm lng thp:0

10,961,21%

. 20.45sA

b h = = = >min=0,05% v

As=11,12(cm2)>Astt b tr thnh 2 lp: lp di

218+116 ;lp trn 216 .(hnh v)

Kim tra gi thit :sA

si iA aa =

vi Asi l din tch ct thpca

lp th i ; ai khong cch t lp ct thp th i mp dm.

(hnh v) .Vi trng hp chon ct thp nh trn ta tnh c

a =4,7(cm)m bo (thin v an ton)

+Vi nhp gia: Mmax=90,26(KN.m)

Gi thit a=3,5(cm) suy ra h0=h-a=50-3,5 = 46,5 (cm),

Xc nh trc trung ha: Mf=Rb.b'fh'f(h0-0,5.h'f)=577,8(KN.m)

V M trc trung ha i qua cnh.Nn khi tnh ton ta tnh ton vi tit din b'f x h=182x 50 (cm)

2 3 20

90,260,027

. . 8, 5.10 .1,82.(0.465)m b

M

R b h = = =

Tha mn0,439

0,3

m R

m d

< =

< =

0,5(1 1 2 ) 0,986m = + = =>

23

0

90,267,03( )

. . 280.10 .0,986.0, 465s s

MA cm

R h= = =

Hm lng thp:0

7,030,76%

. 20.46,5sA

b h = = = >min=0,05% v b

hn3

ax 3

8,5.100,629 1,97%

280.10

bm R

S

R

R = = = ;

316

218

116

218

Sc=81(cm) Sc=81cm

b

h

h

b

f

f'

'


13/39

n B tng ct thp GVHD: Th.s Trn Anh ThinChn v b tr ct thp : 218+116 =>As=7,101(cm2)>Astt b tr thnh 1 lp:

Kim tra gi thit : a=2+1,8/2=2,9(cm) m bo ,thin v an ton.

3.5)Tnh ton ct ai:

AB

QA

QB

BQ

t

p

Tnh ton ct ai cho 3 tit din :A,B

t

,B

p

a) Tnh ton ct ai cho tit din Bt:

+QBt=135,18(KN)

+Ct thp ai AI c Rsw=175.103(KN/m2) ;Es=21.104MPa

Btng cp bn B15 c Rb=8,5.103(KN/m2);Eb=23.103MPa

Rbt=0,75.103(KN/m2)

+Chn ct ai 6 khong cch s =150(mm)

+Kim tra kh nng chu ng sut nn chnh ca bng dm:

max 1 1 00,3 w b bQ R bh

Trong : w1: h s xt n nh hng ca ct ai t vung gc vi trc cu kin

ww 511 += =1 5 9,13 0,0019+ =1,086 1,3

b1: h s xt n kh nng phn phi li ni lc ca cc loi btng khc nhau

bb R =11 =1 0,01 8,5 0,91 = 5

Vi: 2 28.3200 150sw

w Abs = = =0,0019 (h s 2 tng ng 2 nhnh)

3

4

1023

1021

==

b

s

E

E = 9,13

Suy ra: 3max 1 1 0135,18 0,3 0,3.1,086.0.915.85.10 .0,2.0.453 228,45( )w b bQ R bh KN = = =

Vy dm khng b ph hoi do ng sut nn chnh .

+Kim tra cng trn tit din nghing theo lc ct:

Tnh Mb: Mb =2

02 )1( bhRbtnfb ++

Trong : b2: H s xt n nh hng ca cc loi btng; b2=2(Btng nng)


14/39


n: H s xt n nh hng ca lc dc trc. n=0Lc dc khng k n)

f: H s xt n nh hng ca cnh tit din ch T v ch I.

f=0 (do ti gi B tit din tnh ton l hnh ch nht).

Suy ra:Mb =2

02 )1( bhRbtnfb ++ =61,56(KN.m)

q1==gdp+pdp/2=10,1825+24/2=22,1825(KN)

-Tnh :Qb1 = 2 1qMb = 2 61.56 22,1825 = 73,9(KN).

Kim tra: Qmax =135,18(KN)6.0

1bQ =123,17(KN) (khng tha mn)

-Tnh: 10

61,5673,9 209,81( )

0,453b

b

MQ KN

h+ = + =

Kim tra: 6.01bQ


15/39


=0,6(1+0+0).0,75.103.0,2.0,453=40,77(KN)

(b3: h s =0,6 i vi btng nng)

qsw=67,63

min

02bQ

h>

=45(KN/m) (tha mn)

Nh vy : Ly q sw=67,63(KN/m)Vi ai 6 hai nhnh ,khong cch khu vc gn gi ta :

s =sw

swsw

q

AR=

3

3

175.10 2 28.3146,5

67,63.10

= (mm)

smax=2 2

4 0(1 ) 1,5(1 0)750.0,2.0,453 342( )ax 135,18

b n bt R bh mmQm

+ += =

(m bo khng xut hin khe nt nghing ct qua b tng)

sct

500167

3 3

h = =

(mm) theo TCXD 356-2005

(m bo yu cu cu to ca ct thp ai gn khu vc gi ta)

sgt=150(mm) (Khong cch gi thit ban u).

Kt lun : chn 6 hai nhnh , s=140 khu vc gn gi ta

chn 6 hai nhnh , s=250 khu vc gia nhp.

Tnh chiu di khu vc gn gi ta:

qsw1=70,69(KN/m) ; qsw2=39,58(KN/m)

q1=22,1825 = =

Theo TCXD 356-2005 yu cu l1

6,591, 65( )

4 4bl m = =

Kt lun : chn l1=1,65(m).b) Tnh ton ct ai cho tit din Bp:

+QBp

=111,09(KN) gim n gin ,ngn gn y khng trnh by li cc bc tnh ton m ch nua kt

qu sau khi tnh (cc bc tnh ton xem phn trn)

Kt qu :qsw=40,65(KN/m)

Vi ai 6 hai nhnh ,khong cch khu vc gn gi ta :

s =sw

swsw

q

AR=

3

3

175.10 2 28.3243

40,65.10

= (mm) smax=

2 24 0(1 ) 1,5(1 0)750.0,2.0,453 342( )

ax 135,18b n bt R bh mm

Qm

+ += =


16/39


(m bo khng xut hin khe nt nghing ct qua b tng)

sct

500167

3 3

h = =

(mm) theo TCXD 356-2005

(m bo yu cu cu to ca ct thp ai gn khu vc gi ta)

sgt=160(mm) (Khong cch gi thit ban u).Kt lun : chn 6 hai nhnh , s=160(mm) khu vc gn gi tachn 6 hai nhnh , s=250 (mm) khu vc gia nhp

l1=1,65(m)

c) Tnh ton ct ai cho tit din A:

+QA=90,105(KN)

Kt qu :qsw=40,65(KN/m)

Kt lun : chn 6 hai nhnh , s=160(mm) khu vc gn gi tachn 6 hai nhnh , s=250 (mm) khu vc gia nhp

l1=1,65(m)

3.6) Tinh ton v v hnh bao vt liu:

Theo TCXDVN 356-2005 : i vi dm b dy lp btng bo v l 20(mm),i vi

bn l 10(mm) .

V vy: nhp: ta ly lp btng bo v l c0=20 (mm) ;

gi : ct ca dm ph nm di ct bn do chiu dy lp btng bo v thc tl :c0= c0bn+ct bn=10+8=18(mm) n gin ly c0=20 (mm) Khong

cch thng thy t0=30(mm).

T chiu dy lp btng bo v v yu cu b tr ct thp tnh ra a =>h 0 (xem thm mc

3.4b)

Ghi ch: Cc phng n tnh ton ct thp y khng cp n m ch cp n

phng n ct thp cui cng - theo cc tnh ton trn. (hnh v)

Kh nng chu lc ca cc tit din: Mtd tnh trong bng sau:

Cc cng thc s dng:S

b 0RSR A

bh = ; 1 0,5 = ; S 0td SM R A h=

Ch : Vi tit din chu mmen dng ly b=b'f :

Tit din S lng As(cm

2

) h0(cm) b(m)

Mtd

(KN.m)Cnh nhp bin 218 + 116 :un 2 7,101 47,1 1,82 0,027 0,986 92,37


17/39

n B tng ct thp GVHD: Th.s Trn Anh Thin(gn gi A) thanh s 3 trc(216)Gia nhp bin 218 + 316 :(H.a) 11,123 45,4 1,82 0,044 0,978 138,26Cnh nhp bin

(gn gi B)

218 + 116 :un 2

thanh s 3 trc(216)7,101 47,1 1,82 0,027 0,986 92,37

Cnh nhp bin 218 5,090 47 1,82 0,020 0,990 66,33Trn gi 18+416 :(H.b) 10,589 45,5 0,2 0,383 0,808 109,05

Cnh gi216+216: ct thanh s

4 (18) 8,044 44,8 0,20,296

0,852 85,98

Cnh gi216: Ct 2 thanh s 3

(216) 4,022 47,2 0,20,140

0,930 49,42

Cn li 2164,022 47,2 0,2

0,140

0,930 49,42

Gia nhp gia 218+16:(H.c) 7,101 47,1 1,82 0,027 0,986 92,37

Cnh nhip gia

gn gi B

218: un thanh s 6 ln

trn gi B5,090 47,1 1,82 0,020 0,990 66,47

12

3

4 5

6

716

218

216

18216

16

218

+

+

4

4

H.a:Gia nhp bin H.b:Gi B H.c:Gia nhp gia

Ghi ch : k hiu+ 4 c ngha l ni vo thanh s 4 .Ta tin hnh un hai thanh s 2 v s 6

ri ni vo thanh s 4 (ni buc).

Hnh bao vt liu c th hin nh sau (trang sau):


18/39


49,4

2

85,9

8

49,4

2

92,37

90,28

106,1

4

66,33

92,37

138,2

6

135,0

992,37 6

6,33

109,0

5

85,9

8

3.7) Tnh ton ct un v ni ct thp dm ph:

a)Ct 2 thanh 16 (hai thanh s 3) bn phi gi B: Tit din ct l thuyt cch mp

phi gi B 1 on theo t l l 122 (cm) , on ko di tnh theo cng thc (khng tnh ct xin):

Theo ti liu trang 116 kt cu BTCT - Phn cu kin c bn

sw

QW= 5

2q

20

d

W d

+

Vi d l ng knh ca thanh d=16(mm)

Bn phi gi ta B s=160(mm)=> qsw= sw swR A

s=

3175.10 2 28.361,9( / )

160KN m

=

Lc ct Q ti tit din cch mp phi gi ta 1 on x c tnh da vo nguyn l tam gic

ng dng :QBp=111,09(KN)

Q=( / 2 )

/ 2pB

l xQ

l

= 69,4 (KN)

Suy ra: sw

QW= 5 0,64( )

2q

20 0,32( )

d m

W d m

+ = =

Vy chn W=0,64(m)

Nh vy on ko di tnh t trc gi ta n mt ct thpz1=b/2+x+W=0,15+1,22+0,64=1,99(m) Ly 2(m)

b)Ct thanh 18: tng t nh vic ct 2 thanh 16 :

Pha tri gi t B : Da vo hnh bao mmen ta xc nh c tit din ct l thuyt

ca thanh 18 (thanh s 4) l x =40,5(cm) =>on ko di W(khng c ct xin pha trc):

sw

QW= 5

2q

20

d

W d

+

Vi Q=(3 / 5 )

3 / 5tb

Bb

l xQ

l

= 121,33 (KN) ; qsw=70,69 (KN/m)

p

QB

B

l/2=3250

x=1220

Q


19/39

n B tng ct thp GVHD: Th.s Trn Anh ThinSuy ra :

sw

QW= 5 0,95( )

2q

20 0,36( )

d m

W d m

+ = =

Vy W=0,95(m) Nh vy on ko di tnh t trc gi t

n mt ct thp z2=b/2+x+W=0,15+0,405+0,95=1,55(m) Ly 1,5(m)

Pha phi gi ta B :(Tng t ct thanh 18) , xc inh c tit din ct l thuyt cch

mp gi ta phi 1 on x=49(cm) Tnh c Q=( / 2 )

/ 2pB

l xQ

l

= 94,34(KN) ;

qsw=61,9(KN/)=>W=0,85(m)=>z 3=b/2+x+W=0,15+0,49+0,85=1,49(m) => ly 1,5(m).

12

3

4 5

6

716

218

216

18216

16

218

+

+

4

4

c) Un cc thanh :

V vic un hai thanh 16 (thanh s 2 v s 6) khng lm ct xin tnh ton v th vic

un hai thanh ny ni vo thanh 18 (ni buc) phi p ng yu cu v cu to v yu cu lm

cn xng biu bao vt liu (tit kim vt liu) v mi ni khng thuc khu vc chu ko qu

nhiu - ta ch dng ni buc ni 2 thp ny vo thanh 18.

Cc yu cu v un khng lm ct xin: im bt u un phi cch tit din trc mt on

ln hn 0,5h0=0,5x470=235(mm) (v pha mmen gim); im kt thc phi nm ra ngoi tit din

sau ; v khng kt hp lm ct xin nn la chn im un sao cho biu bao mmen c cn

xng.

Chi tit on un cc thanh:(Xem hnh v v chi tit trang sau)

K hiuthanh thp

Khuvc

V tr un pha didm

V tr un ph trndm

Chiu dion un

Gcun

Q

t

BQ

AQ

BA

3l/5

2l/5

x=40,5


20/39


S 3

Gi ACch mp gi A

1340(mm)

Cch mp gi A

960(mm)45

Gi BCch mp gi B

1460 (mm)

Cch mp gi B

1080(mm)45

S 2Gi A

Cch mp gi A

330(mm)

Cch mp gi A

770(mm)45

Gi BCch mp gi B

880(mm)

Cch mp gi B

440(mm)45

S 6 Gi BCch mp gi B

2020(mm)

Cch mp gi B

1580(mm)45

Ghi ch: cc khong cch trn suy t biu bao vt liu - biu bao mmen (hinh v)

405675 490 730

330770

1340

960

380

300

440880

1460

1080

1580

2020

380

Chi tit on neo cc thanh c un t pha di ln pha trn:

V mi ni buc hai thanh s 2 v s 6: do vic tnh ton ct thanh 18 khng tnh n mi

ni cho nn yu cu v mi ny ch l yu cu v cu to on ni (tnh theo cng thc neo ct

thp-v bn cht khng phi l mt mi ni thc s) lan :

San an an

b

an an

Rl d

R

l d

= +

;Cc h s an; an ;an tra bng 36-TCXDVN 356-2005

Ta c : d =16(mm) ; an=0,5; an =8;an=12;Rs=280(Mpa);Rb=8,5Mpa

Suy ra:

280(0,5 8)16 390( )

8,5

192( )

San an an

b

an an

Rl d mm

R

l d mm

= + = + =

=

=>ly lan=390(mm)


21/39

n B tng ct thp GVHD: Th.s Trn Anh ThinV on neo ct thp s 2 v 3 khu vc gi ta A (gn tng ) do khng chu ko (thc ra

vn tn ti mmen m nhng b - v lc ct QA=90,105(KN)) ta ly theo yu cu cu to ti thiu

lan=and=192(mm)=> chn 190(mm).

Hnh v b tr ct thp dm ph cui cng:

4)Tnh ton dm chnh:

*) Dm chnh k ln cc ct (cc gi gia) c b rng bc=30(cm) ,Ti gi

bin dm chnh k ln tng chu lc vi on k bng chu dy tng chu lc

t=34(cm)>30(cm)

4.1)S tnh ton dm chnh: (Tnh theo s n hi)

+ S dm: Dm lin tc 4 nhp+ Chiu di nhp gia v nhp bin gn bng nhau v th n gin

tnh ton ta c th coi chng gn bng nhau v bng l=3l1=3.2,5=7,5(m).

4.2)Ti trng tnh ton:

+Hot ti: (K hiu P)

P=Pdp.l2=24.6,8=163,2(KN)

Vi: Pdp: Hot ti phn b trn dm ph Pdp=24 (KN/m)

l2 :Khong cch gia cc dm chnh l2=6,8(m)

+Tnh ti : (K hiu G)

G=gdpl2+G0

Vi : G0: trng lng bn thn dm chnh

G0=b(h-hb)l1. btct .n=0,3.(0,8-0,09).2,5.25.1,1=14,644(KN)

b: b rng dm chnh bng 30 cm

h:chiu cao dm chnh bng 80 cmhb:chiu cao bn bng 9 cm

btct : trng lng ring btng ct thp bng 25 (KN/m3)

n: h s vt ti

gdp:tnh ti phn b u trn dm ph gdp=10,1825(KN/m)

Vy: G=10,1825.6,8+14,644=83,89(KN)

Ghi ch: Trng lng bn thn dm chnh phn phi u nhng dn gin tnh ton

ta em v thnh cc lc tp trung cng tc dng vi G1=gdpl2 t ti v tr cc dm ph.

+S ti trng tc dng ln dm chnh


22/39


4.2) Tnh ton ni lc:

a)Biu bao mmen:

Li dng tnh cht i xng ca s dm chnh ta ch cn xt v v biu

bao cho 1/2 dm bng phng php t hp.

+ t hp ni lc ta cn bit biu (MG) v cc t hp bt li nht ca hot ti

i vi cc tit din: c th v thm 6 biu (Mpi):

PPPP

GGGG G/2

P/2P/2

G/2

P

P P

P

PP

PP

P P

PP

G/2GGGGG/2

a)

b)

c)

d)

e)

f)

g)

(MG)

(Mp1)

(Mp2)

(Mp3)

(Mp4)

(Mp5)

(Mp6)

H : Cc trng hp t hp ni lc bt li

Ghi ch: Cc t hp ni lc bt li trn c suy t cch t hp t cc bi ton trong ti trng chtc dng ln mt nhp ,cc t hp bt li l cc t hp gy cho 1 hoc nhiu tit din ni lc ln nht


23/39

n B tng ct thp GVHD: Th.s Trn Anh ThinDa vo cc bng tra ni lc ta xc nh biu bao momen trong bng sau : (ch cn tnh

cho mt na dm chnh)

G/2

P/2 P/2

G/2G G G G

P P P P

A B C D E1 2 3 4 5 6 7 8

H.:Cc tit din tnh ton.

Cc cng thc tnh MG=Gl ; Mpi=Pl vi l=7,5m

S Tit din 1 2 B 3 4 C

MG 0,238 0,143 -0,286 0,079 0,111 -0,190M 149,74 89,97 -179,94 49,70 69,84 -119,54

Mp1 0,286 0,238 -0,143 -0,127 -0,111 -0,095M 350,06 291,31 -175,03 -155,45 -135,86 -116,28

Mp2 -0,048 -0,095 -0,143 0,206 0,222 -0,095M -58,75 -116,28 -175,03 252,14 271,73 -116,28

Mp3 -0,321 -0,048M -392,90 -58,75

Mp4 -0,031 -0,063 -0,095 -0,286

M -37,94 -77,11 -116,28 -350,06Mp5

-0,19 0,095M -232,56 116,28

Mp6 0,036 -0,143M 44,06 -175,03

T hpMmax 499,81 381,28 -135,88 301,85 341,57 -3,26Mmin 90,99 -26,31 -572,85 -105,74 -66,03 -469,61

Mmax=MG+max(Mpi) ; Mmin=MG+min(Mpi)

Da vo s liu trn ta v c biu bao momen: (trang sau)


24/39


-469,6

1

-66,0

2

341,5

7

-105,7

8

301,8

5

-135,8

8

-572.8

5

-26,3

1

381,2

8

499,8

1

90,9

9

Nhn xt: Qua vic t hp cc trng hp ni lc bt li ta thy rng khi xut hin mmen

cc i gi th gi tr mmen nhp li nh .Nu t ct thp chu lc chu ht mmen

gi ta v mmen cc i nhp theo s n hi s lng ph vt liu v hai gi tr mmen cci khng xut hin cng mt trng hp ti trng . Da vo nguyn l v s phn phi li ni

lc do s xut hin ca khp do (mc 10.2.2 sch Kt cu BTCT - Phn Cu Kin c bn) ta c

th iu chnh biu bao mmen nh sau.

Gim mmen gi ta xung 10% gi tr theo s n hi (lng gim ti a cho php

30% -tuy nhin an ton ta khng nn gim qu nhiu) . Mmen gia nhp vn gi nguyn gi

tr tnh ton theo s n hi.

Ghi ch:Vic gim mmen gi ta l ta chp nhn khi xy ra t hp bt li gi ta th gi

s xut hin khp do , ni lc s phn phi li vo gia nhp (gi tr mmen ny b hn gi tr mmen tnh

ton ln nht theo s n hi). Vic lm ny s c ngha trong vic gim bt ct thp gi ta v

kh dy khi btng.

b) Tnh mmen mp gi:

Vic dng biu bao mmen tnh mmen mp gi th khng chnh xc bi v

ng vi khi cc tit din gi t gi tr cc tr th cc tit din ln cn gi khng t gi tr cc tr ,

tuy nhin vic tnh mmen mp gi theo biu bao mmen li thin v an ton nn ta chn cch

tch ny n gin.

Ghi ch: Nu mun tnh chnh xc hn ta c th tnh mmen mp gi B bng t hp

(MG,Mp3) v dng t hp (MG,Mp4) .

+Ti gi B: Momen mp gi trong ln hn ta tnh cho mp trong

3

3 11

( ) ( 515,56 105,78)( ) 105,78 (2,5 0,15) 491( . )

2 2,5

B c

mgB

M M bM M l KN m

l

+

= + = + =

+Ti gi C:


25/39


4

4 11

( ) ( 422, 65 66, 02)( ) 66,02 (2,5 0,15) 401,25( . )

2 2,5C c

mgC

M M bM M l KN m

l

+= + = + =

Trong : MB,MC,M3,M4 : l mmen ti cc tit din B ,C, 3, 4

l1 :khong cch cc tit din l1=2,5 m

bc : b rng ct bc=0,3 mMmen dng tnh ton ct thp:

nhp bin (tit din 1):Mmax=499,81(KN.m)

nhp gia (tit din 4): Mmax=341,57(KN.m)

gi ta B : Mmax=MmgB=491(KN.m)

gi ta C: Mmax=MmgC=401,25(KN.m)

c) Biu lc bao ct:

Tin hnh tnh ton tng t nh vi biu bao mmen

Ghi ch: Vic tm t hp bt li tin hnh bng cch t hp t cc bi ton trong ti trng ch

tc dng ln mt nhp , biu lc ct ca mi trng hp c th suy t biu mmen ca trng hp

tng ng.

Bng s liu tnh ton:QG=G ; Qpi=P

S onBn phi

A

Gia

nhp bin

Bn tri

B

Bn phi

B

Gia

nhp

Bn tri

C

QG

0,714 -0,286 -1,286 1,095 0,095 -0,905Q 59,90 -23,99 -107,88 91,86 7,97 -75,92

Qp1

0,857 -0,143 -1,143 0,048 0,048 0,048Q 139,86 -23,34 -186,54 7,83 7,83 7,83

Qp2

-0,143 -0,143 -0,143 1,048 0,048 -0,952Q -23,34 -23,34 -23,34 171,03 7,83 -155,37

Qp3

0,679 -0,321 -1,321 1,274 0,274 -0,726Q 110,81 -52,39 -215,59 207,92 44,72 -118,48

Qp4 -0,095 -0,095 -0,095 0,81 -0,1905 -1,191Q -15,50 -15,50 -15,50 132,19 -31,01 -194,37

Qp5

0,81 -0,19 -1,19 0,286 0,286 0,286Q 132,19 -31,01 -194,21 46,68 46,68 46,68

Qp6

0,036 0,036 0,036 -0,178 -0,178 -0,178Q 5,88 5,88 5,88 -29,05 -29,05 -29,05

Qmax 199,76 -18,11 -102,01 299,78 54,65 -29,25Qmin 36,56 -76,38 -323,47 62,81 -23,04 -270,29

Biu bao lc ct c v trang sau:


26/39


199,7

6

76,

38

323,4

7

299,7

8

54,6

5

270,2

9

36,5

6

18,1

1

102,01

23,0

4

29,2

5

B

A

C

Biu bao lc ct

Lc ct dng tnh ton ct thp:

nhp bin (on A1):Q=199,76(KN)

nhp bin (on 2B): Q=323,47(KN)

nhp gia (on B3):Q=299,78(KN)

nhp gia (on 4C):Q=270,29(KN)

* )Ta khng quan tm nhiu n phn biu bao gia nhp v khu vc ny gi tr lc

ct b hn gi rt nhiu.

4.3)Tnh ct thp dc:

Ct thp chu lc AII c Rs=280.103(KN/m2)Btng cp bn B15 c Rb=8,5.103(KN/m2)

a)Vi tit din chu mmen m (gi B):

+Mmen ln nht : Mmax=MmgB=491(KN.m)

+Cnh nm trong vng chu ko nn khng k n trong tnh ton ,Tit din tnh

ton hnh ch nht vi b = 30 cm ,h = 80 cm gi thit a= 8 cm

(do ct thp dm chnh phi t bn di hng trn cng ca ct thp dm ph) =>

h0 =80-8=72 (cm) .

C : 2 3 20

4910,371

. . 8,5.10 .0,3.(0.72)m b

M

R b h = = =


-Vi Btng cp bn B15 ,ct thp nhm AII :

0,439; 0,650R R = =

Ta thy m khng cn phi t ct kp v tha mn xyra trng hp ph hoi do.

ho

x

h

b


27/39

n B tng ct thp GVHD: Th.s Trn Anh Thin(Theo sch Kt cu BTCT - Phn cu kin c bn trang 311 th m>0,225 -nu tnh theo s

c k n s phn phi li ni lc => tha mn)

Suy ra: 0,5(1 1 2 ) 0,754m = + = =>2

30

49132,30( )

. . 280.10 .0,754.0,72s s

MA cm

R h= = =

Hm lng thp:0

32,30 1,5%. 30.72

sAb h

= = = >min=0,05% v b hn

3

ax 3

8,5.100,629 1,97%

280.10

bm R

S

R

R = = = .

b)Vi tit din chu mmen m (gi C):

+Mmen ln nht : Mmax=MmgC=401,25(KN.m)

+Cnh nm trong vng chu ko nn khng k n trong tnh ton ,+Tit din tnh ton hnh ch nht vi b = 30 cm ,h = 80 cm gi thit a= 8 cm

(do ct thp dm chnh phi t bn di hng trn cng ca ct thp dm ph

v c th t nhiu lp) =>h0 =80-8=72 (cm)

C : 2 3 20

401,250,304

. . 8,5.10 .0,3.(0.72)m b

M

R b h = = =


-Vi Btng cp bn B15 ,ct thp nhm AII : 0,439; 0,650R R = =Ta thy :m khng cn phi t ct kp v tha mn xy ra trng hp ph

hoi do.m>0,225

Suy ra: 0,5(1 1 2 ) 0,813m = + = =>2

30

401,2524,48( )

. . 280.10 .0,813.0,72s s

MA cm

R h= = =

Hm lng thp:0

24,481,13%

. 30.72sA

b h= = =

>min=0,05% v b hn

3

ax 3

8,5.100,629 1,97%

280.10

bm R

S

R

R = = = .

b)Vi tit din chu mmen dng

Tit din tnh ton c dng ch T :

Sc=81(cm) Sc=81cm

b

h

h

b

f

f'

'


28/39


' 2f cb b S= + ; : { }2min 0,5( );1/ 6 ;9dc fSc l b l h =>

{ }min 3,25;1,25;0,81Sc

Chn Sc=0,81(m)=81(cm);

Nh vy :' 2 30 2.81 192( )f cb b S cm= + = + = Xc nh trc trung ha:

Mf=Rb.b'fh'f(h0-0,5.h'f)=1006,13(KN.m)

+Vi nhp bin: Mmax=499,81(KN.m)

V M ln nn ta gi thit a=6(cm) ( c th t 2 lp thp)

=> h0=h-a=80-6 = 74 (cm).V Mmax trc trung ha i qua cnh.

Nn khi tnh ton ta tnh ton vi tit din : b'f x h =192x80(cm)

2 3 20

499,810,056

. . 8, 5.10 .1, 92.(0.74)m b

M

R b h = = =

Tha mn 0,439m R < =

0,5(1 1 2 ) 0,971m = + = =>

2

30

499,81

24,84( ). . 280.10 .0,971.0, 74s s

M

A cmR h= = =

Hm lng thp:0

24,841,12%

. 30.74sA

b h= = = >min=0,05% v

h0=h-a=80-5,5 = 74,5 (cm).V Mmax trc trung ha i qua cnh.

2 3 20

341,570,038

. . 8, 5.10 .1, 92.(0, 745)m b

M

R b h = = =

Tha mn 0,439m R < =

0,5(1 1 2 ) 0,981m = + = =>2

3

0

341,5716,692( )

. . 280.10 .0,981.0,745s

s

M A

R h

= = =


29/39


Hm lng thp:0

16,6920,75%

. 30.74,5sA

b h= = = >min=0,05% v

thin

v an ton ta khng cn phi kim tra li .

4.4)Tnh ct thp ngang v ct xin:

Ct thp AII c Rsw=225.103(KN/m2);Es=21.104MPa

Ct thp ai AI c Rsw=175.103

(KN/m2

) ;Es=21.104

MPaBtng cp bn B15 c: Rb=8,5.103(KN/m2);Eb=23.103MPa

Rbt=0,75.103(KN/m2)

Gi thit: Ct ai 8 hai nhnh , vi khong cch s=260(cm)

Kim tra iu kin : s


30/39

n B tng ct thp GVHD: Th.s Trn Anh Thina)i vi on dm bn tri gi B:

+Q=323,47(KN)


max 1 1 00,3 w b bQ R bh

Trong : w1: h s xt n nh hng ca ct ai t vung gc vi trc cu kin

ww 511 += =1 5 9,13 0,0019+ =1,086 1,3

b1: h s xt n kh nng phn phi li ni lc ca cc loi btng khc nhau

bb R =11 =1 0,01 8,5 0,91 = 5

Vi:2 50.27

200 260sw

w

A

bs

= =

=0,0019 (h s 2 tng ng 2 nhnh)

3

4

1023

1021

==

b

s

E

E = 9,13

Suy ra: 3max 1 1 0323,47 0,3 0,3.1,086.0,915.8,5.10 .0,3.0,725w b bQ R bh = = = 551,12(KN)

Vy dm khng b ph hoi do ng sut nn chnh .

Mb =2

02 )1( bhRbtnfb ++ =2750.0,3.0,7252=236,53(KN.m)

qsw= sw swR A

s=

3175.10 2 50.2667, 66( / )

260 KN m

=

0w

236,531,870( )

67,66b

s

Mc m

q= = = =1870(mm)>2h0=1450(mm)

Do ta phi ly c0=1450 tnh kh nng chu ct ca btng v ct ai:2 2

2 0w 0

0

(1 ) 2 750 0,3 0,72567,66.1,45

1,45b f n bt

u s

R bhQ q c

c

+ + = + = + = 261,23(KN)

Ta thy : Qu cn phi b tr ct xin.

Da vo smax; Qu ; v c s kt hp ct dc lm ct xin tnh ton ta b t cc lp ct xinnh sau: (hnh v)

Ghi ch: cc ng nt t l cc mt ct nguy him ta cn phi kim tra cng

iu kin hn ch: i vi ci

ci

20

3

2725 2417( )

0,6b

b

h mm

= =

( Qb>Qbmin)

ci

20

2(1 ) 1 725 580( )

2,5 2,5

bf n h mm

+ + = =

( Qbc0=2h0


31/39

n B tng ct thp GVHD: Th.s Trn Anh ThinTnh ton din tch ct xin:

Theo mt ct nghing c1:

1 w 1 w . 11

sin bs s s incM

Q q c R Ac

< + + ;

323,47As.inc1 3,5(cm2)

D kin t 1 thanh ct vai b 28 :As.inc1=6,518(cm2)=> m bo


2 w 2 w . 22

sin bs s s incM

Q q c R Ac

< + + ;

323,47As.inc2 3,76(cm2)

D kin un 2 thanh 28 t pha di ln : As.inc2=12,316(cm2)=>m bo


0 w 0 w . 20

sin bs s s incM

Q q c R Ac

< + + ;=>As.inc2 3,91(cm2)=>m bo

Trong :

Qi: lc ct u mt phng nghing ci ,v trong trng hp ny Qi=Q=323,47(KN): gc hp bi ct xin v mt phng ngang. =450

380670330640330

C2=1300

C3=2350

Co=1450

C1=1380

B

As.inc1

s.inc2A

P+G

b)i vi on dm bn ph i gi B:(tng t bn tri B)

+Q=299,78(KN) ;


32/39


smax=2 2

4 0(1 ) 1,5(1 0)750.0,3.0,725 592( )ax 299,78

b n bt R bh mmQm

+ += =


Dm khng b ph hoi do ng sut nn chnh do Q< tBQ =323,47(KN)

Mb=2

02 )1( bhRbtnfb ++ =2750.0,3.0,7252=236,53(KN.m)

qsw= sw swR A

s=

3175.10 2 50.2667, 66( / )

260 KN m

= 0

w

236,531,870( )

67,66b

s

Mc m

q= = =

=1870(mm)>2h0=1450(mm)

Do ta phi ly c0=1450 tnh kh nng chu ct ca btng v ct ai:

2 22 0

w 00

(1 ) 2 750 0,3 0,725

67,66.1,451,45

b f n bt

u s

R bh

Q q cc

+ +

= + = + = 261,23(KN)

Qu cn phi b tr ct xin.


ci

20

3

2725 2417( )

0,6b

b

h mm

= =

ci

20

2(1 ) 1 725 580( )

2,5 2,5b

f n h mm

+ + = =

Tt cc ci u tha mn , khng cn tnh cho mt

phng nghing c3 ;

Tnh ton din tch ct xin:


1 w 1 w . 11

sin bs s s incM

Q q c R Ac

< + + ;

299,78As.inc1 1,83(cm2)



2 w 2 w . 22

sin bs s s incM

Q q c R Ac

< + + ;

299,78As.inc2 2,27(cm2)

D kin un thanh 30 t pha di nhp gia ln : As.inc2=7,069(cm2)=>m bo

300 700 300

C1=1350

P+G

As.inc2

s.inc1A

B

Co=1450

C3=2350

C2=1300

380 670


33/39

n B tng ct thp GVHD: Th.s Trn Anh ThinTheo mt ct nghing c0:

0 w 0 w . 20

sin bs s s incM

Q q c R Ac

< + + ;=>As.inc2 2,42(cm2)=>m bo

c)i vi on dm bn tri gi C:(tng t cc phn trn)

+Q=262,602(KN)h0=72,2(cm)=> smax=

2 24 0(1 ) 1,5(1 0)750.0,3.0,725 675( )

ax 262,602b n bt R bh mm

Qm

+ += =

Qu=247(KN)

Q>Qu=> tnh ct xin

Da vo smax; Qu ; v c s kt hp ct dc lm ct xin tnh ton ta b t cc lp ct xinnh sau: (hnh v)

Ghi ch: cc ng nt t l cc mt ct nguy him ta cn phi kim tra cng


ci

20

3

2725 2417( )

0,6b

b

h mm

= =

( Qb>Qbmin)

ci

20

2(1 ) 1 725 580( )

2,5 2,5

bf n h mm

+ + = =

( Qbc0=2h0

Tnh ton din tch ct xin:


1 w 1 w . 11

sin bs s s incM

Q q c R Ac

< + + ;

323,47As.inc1 3,5(cm2)


380700315640315

P+G

A s.inc2

s.inc1A

CC1=1395

Co=1450

C3=2350

C2=1270


34/39

n B tng ct thp GVHD: Th.s Trn Anh ThinTheo mt ct nghing c2:

2 w 2 w . 22

sin bs s s incM

Q q c R Ac

< + + ;

323,47As.inc2 3,76(cm2)

D kin un 2 thanh 28 t pha di ln : As.inc2=12,316(cm2)=>m bo


0 w 0 w . 20

sin bs s s incM

Q q c R Ac

< + + ;=>As.inc2 3,91(cm2)=>m bo

Trong :

Qi: lc ct u mt phng nghing ci ,v trong trng hp ny Qi=Q=323,47(KN)

: gc hp bi ct xin v mt phng ngang. =450

380670330640330

C2=1300

C3=2350

Co=1450

C1=1380

B

As.inc1

s.inc2A

P+G

d)i vi on dm bn phi gi A :(tng t)

+ Qmax=199,76(KN) ; c0=2h0=1480(mm)

2 22 0

w 00

(1 ) 2 750 0,3 0,7467,66.1,48

1,48b f n bt

u s

R bhQ q c

c

+ + = + = + = 266,63(KN);

+Qmax khng cn tnh ct xin

m b tr theo cu to .

4.5)Tnh ton ct treo:

P+G1

Str=900

h=350

bdp=200


35/39

n B tng ct thp GVHD: Th.s Trn Anh Thin ch dm ph giao nhau vi dm chnh phi gia c thm ct ai hoc dng ct vai b lt

ngc chng ph hoi theo mt phng nghing 450 xut pht t mp dm ph (hnh v)

S ct treo ny t trong phm vi

Str=bdp+2h =900(mm)

Din tch cc thanh ct treo cn thit l

01str

s s

P G GPA

R R

+ = =

P1: kc tp trung t dm ph truyn vo dm chnh .(khng k n trng lng

bn thn dm chnh).

Rs: cng tnh ton v ko ca ct thp

P1=163,2+83,89-14,644=232,446(KN)

Dng 2 8 hai nhnh Rs=225.103 =>Astr=10,33(cm2)

S lng nhnh ct treo cn dng:

10,33

2. 2.0,503str

str

An

a= = =10,27 => phi dng 12 thanh, mi bn 6 thanh

Khong cch gia cc thanh : s=6(cm).

4.6)Ct un ct thp v v hnh bao vt liu:

a)Kh nng chu lc ca cc tit din:

B tr cc thanh thp ti cc tit din chnh nh hnh v:

Cc

tit din

chnh:

Tit din Ct thp As(thc t)

(cm2)h0(thc t)

(cm)B rng

(m)Mtd

(KN.m)Nhp bin 228 + 225 + 122 25,935 74 1,92 521,22

Gi B 30+328+222 33,145 72,5 0,3 503,96Nhp gia 30+225 16,887 76 1,92 352,51

Gi C 30+225+222 24,489 73,3 0,3 410,42Cc

tit din

ph sau khi un ,ct :

800

90

12

3

5

4

8

7

910

6

222

228

22522

30

28

225

225

30

222

300 300 300300


36/39


Tit din Ct thpAs(thc t)

(cm2)

h0(thc t)

(cm)

B rng

(m)

Mtd

(KN.m)Nhp bin 225 + 122: 13,619 76,5 1,92 287,26

Bn tri B

*30+228+222:u

n thanh 6 (ct vai b)*30+22: un 2

thanh s 3 (228)

222: ct thanh s 4

26,987

14,671

7,602

73

75

750,3

439,66

275,00

150,76

Bn phi B

*30+228+222:u

n thanh 6 (ct vai b)

*228+222 : un

thanh s 4 (30)

*222 : ct 2 thanh s

3 (228)

26,987

19,918

7,602

73

72

75

0,3

439,66

340,56

150,76

Nh gia 2 25: un thanh s 4 9,818 76 1,92 206,61

Bn tri C

*225+222:unthanh s 9 (30)

*222 :un 2 thanh s10 (228)

17,42

7,602

73

70,3

309,42

150,76

b)Ct ct thp :

- Ct thanh s 4 28 bn tri gi B:

Da vo biu bao mmen (trang sau) ta xc nh c tit din ct l thuyt ca thanh s

4 cch tm gi B1 on x=146 (cm) (tnh theo tam gic ng dng hoc o trc tip trn biu

bao mmen v hnh bao vt liu ) i chiu vi s d kin t ct xin bn tri gi B ta thy mt

ct nm trong vng c ct xin As.inc2 v th on ko di ca thanh s 4 c tnh theo cng thc

sau:

. 5 202

s inc

sw

Q QW d d

q

= + Vi Q l gi tr lc ct ( dc ca biu mmen)

qsw=67,71(KN/m) ;2

1

530,907 41,833203,8( )

2,4BM MQ KN

l

= = =

Qs.inc2=As.inc2.Rsw.sin =12,316.22,5.0,707=195,9

Thay vo biu thc203,8 195,9

5.0,028 0,198 20 0,562.67,71

W m d m

= + = < =

chn W=20d=56(cm) => chiu di thanh thp k t trc gi B n im ct thc t l

z=x+W=1460+560=2020(mm).


37/39

n B tng ct thp GVHD: Th.s Trn Anh ThinMt ct l thuyt thanh s 4 nm vo gia on xin 2 thanh s 3 c th hin trn hnh bao

vt liu bi bc nhy tng ng gia on xin .Tung bc nhy c gi tr bng gim kh

nng chu lc do ct thanh thp :335,428-235,387=100,041(KN.m).

-Ct hai thanh s 5 (228) bn tri gi B : tit din c mmen m bng khng nm bn tri

gi B cch trc tit din 1 on x=336(cm). l tit din ct l thuyt ca 2 thanh s 5 , sau

dng ct cu to lm ct gi .Din tch ct gi ti thiu l 0,1%bh0=0,1%.280.756=2,12(cm2) => ta

dng 2 thanh 12 c As=2,26(cm2).

Khng c ct xin nn on ko di tnh theo cng thc: 5 202 sw

QW d d

q= +

*Q= dc biu mmen =62,806 41,833

43,602,4

+=

(KN)=>W=46(cm)>20d=44(cm)

Vy on ko di ca 2 thanh s 5 k t trc gi B n mt z5=x+W=3360+460=3820(cm).

Hai thanh ct gi (ch hon ton l cu to do on ni chpvo 2 thanh 22 ch cn ly

theo cu to : 10d=10.1,2=12(cm).

-Ct hai thanh s 5 (228) bn phi gi B:

L do : 2 nhp gia c chiu di qu ln 15 m khng th dng mt thanh thp thng c.

-Ct hai thanh s 3 bn phi gi B (hai thanh 28 ):

Tit din ct l thuyt ca hai thanh s 3 cch trc gi B 1 on x=170(cm) ; pha trc tit

ct l thuyt c ct xin v th on ko di W l:

. 5 202

s inc

sw

Q QW d d

q

= + vi Q=

3

1

530,907 112,732174,24

2,4BM M

l

= = (KN)

Qs.inc2=615,8.225.0,707=98(KN)

qsw =67,71

=>

174, 24 98

5.0,028 0,703 20 0,562.67,71W d

= + = > =

Vy on ko di tnh t trc gi B z3=x+W=1700+703=2403(cm).

Mt ct l thuyt 2 thanh s 3 nm vo gia on xin thanh s 4 c th hin trn hnh

bao vt liu bi bc nhy tng ng gia on xin .Tung bc nhy c gi tr bng gim

kh nng chu lc do ct thanh thp :399,87-325,387=164,45(KN.m).

b)Un ct thp :


38/39

n B tng ct thp GVHD: Th.s Trn Anh ThinBn tri gi B: u tin un thanh s 6 (ct vai b) xung lm ct xin . Ct ny c dng

ht kh nng chu lc ti tit din mp gi (tit din trc) v th phi m bo :

ax

0

380 517,6( )

725380 357,5( )

2 2

ms s mm

hs mm

= < =

= > = =

=> Tha mn. ng thi im kt thc un nm ngoi tit

din sau : (tit din sau cch mp gi 1 on 31,5 cm- tnh bng phng php tam gic ng dng ;

im kt thc un cch truc gi 1 on 120 cm ).

Tng t i vi un 2 thanh s 3 (228)

+ tha mn khong cch t im cui ct s 6 n im u ct s 3

=300(mm) h0/2 v im kt thc un ra ngoi

tit din sau.

Bn phi gi B :

+Thanh s 6 tng t nh bn tri gi B (tha mn).

+Thanh s 4 : (tha mn yu cu v smax )

pha trn gi:

-Tit din trc cch mp gi B mt on 31(cm) , im u on un cch

mp gi 135(cm) =>khong cch:=135-31=104(cm) >h0/2.

-Tit din sau , cch mp gi 1 on 91,5(cm) , im cui on un cch mp gi

205(cm) => tha mn nm ngoi tit din sau.

pha di nhp:

- Tit din trc l tit din c M ln nht tng ng vi im 4 , im bt u

un cch tit din trc 280 (cm) >h0/2;

-Tit din sau cch mp gi B mt on 180(cm) ;im kt thc un cch mp gi

135(cm) => nm ngoi tit din sau (tha mn).Ghi ch: Vic tm tit din trc ; tit din sau tin hnh bng phng php v hoc nguyn l tam

gic ng dng v biu mmen l cc on thng - y khng trnh by.

Bn tri gi C:

+ Thanh ct vai b s 9 (tng t thanh ct vai b s 6 bn tri gi B) => tha mn.

+ 2 thanh ct vai b s 6 (tng t un 2 thanh s 3 (228) bn tri B)=>tha mn.


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