Thuyet Minh Do an BTCT(Dang)New
Transcript of Thuyet Minh Do an BTCT(Dang)New
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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
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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),
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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:
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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= = =
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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)
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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:
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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
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n B tng ct thp GVHD: Th.s Trn Anh Thin
+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
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n B tng ct thp GVHD: Th.s Trn Anh Thin
* 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):
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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
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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'
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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'
'
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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)
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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
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n B tng ct thp GVHD: Th.s Trn Anh Thin
=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
+ += =
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n B tng ct thp GVHD: Th.s Trn Anh Thin
(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
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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):
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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
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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
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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)
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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
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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
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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)
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n B tng ct thp GVHD: Th.s Trn Anh Thin
-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:
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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:
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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 = = =
+Kim tra iu kin hn ch:
-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
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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 = = =
+Kim tra iu kin hn ch:
-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'
'
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n B tng ct thp GVHD: Th.s Trn Anh Thin
' 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
= = =
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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
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n B tng ct thp GVHD: Th.s Trn Anh Thina)i vi on dm bn tri gi B:
+Q=323,47(KN)
+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 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
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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
Theo 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
Theo mt ct nghing c0:
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) ;
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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
+ += =
+Kim tra kh nng chu ng sut nn chnh ca bng dm:
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.
iu kin hn ch: i vi ci
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:
Theo mt ct nghing c1:
1 w 1 w . 11
sin bs s s incM
Q q c R Ac
< + + ;
299,78As.inc1 1,83(cm2)
D kin t 1 thanh ct vai b 28 :As.inc1=6,158(cm2)=> m bo
Theo mt ct nghing c2:
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
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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
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
Tnh 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
380700315640315
P+G
A s.inc2
s.inc1A
CC1=1395
Co=1450
C3=2350
C2=1270
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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
Theo mt ct nghing c0:
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
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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
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n B tng ct thp GVHD: Th.s Trn Anh Thin
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).
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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 :
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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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n B tng ct thp GVHD: Th.s Trn Anh Thin