MÓNG CỌC

GVHD: Ths. Hong Th Thao

NHM MNG CC Trang 1

1.1. S L THUY T 3

1.1.1. CHN CHIU SU CHN MNG Df V KCH THC CC S B: 3

1.1.2. TNH TON SC CHU TI CA CC: 4

1.1.3.TNH TON S B S LNG CC: 12

1.1.4.B TR CC: 12

1.1.5. KIM TRA I CC 13

1.1.6.TNH THP CHO I MNG: 18

1.1.7. KIM TRA SC CHU TI CA CC V NHM CC : 20

1.1.8.KIM TRA N NH CA T NN DI MI CC V LN MNG CC: 21

1.1.9. KIM TRA CC CHU CU LP: 27

1.1.10. NG DNG SAP2000 KIM TRA CC CHU TI NGANG: 28

1.1.11. C S L THUYT KIM TRA CC CHUYN V NGANG: 37

1.1.12. TNH TON NI LC TRONG CC (theo TCXD 205 -1998) 40

2.1.CC D LIU TNH TON: 43

2.1.1.THNG K S LIU A CHT 1B (trch t phn I): 43

2.1.2.S LIU TNH TON: 44

2.1.3.KHAI BO VT LIU: 44

2.2.TRNH T TNH TON V THI T K MNG C C: 44

2.2.1.CHN CHIU SU CHN MNGDfV KCH THC CC S B: 44

2.2.2. TNH TON SC CHU TI CA CC: 45

2.2.3.TNH TON S B S LNG CC: 53


NHM MNG CC Trang 2

2.2.4.B TR CC: 53

2.2.5. KIM TRA I CC 54

2.2.6. KIM TRA SC CHU TI CA CC V NHM CC : 58

2.2.7. TNH THP CHO I MNG: 59

2.2.8.KIM TRA N NH CA T NN DI MI CC V LN MNG CC: 61

2.2.9. KIM TRA CC CHU CU LP: 66

2.2.10.NG DNG SAP2000 KIM TRA CHUYN V NGANG: 67

2.2.11. KIM TRA CC CHU TI NGANG (theo ph lc G TCXD 205 1998): 73


NHM MNG CC Trang 3

: THI T K MNG C C

1.1. S L THUY T

1.1.1. CH N CHIU SU CHN MNG Df V C C S B:

1.1.1a.Chn loi cc thi cng ph hp ( theo TCXD 205:1998 Mc 3.2)

1.1.1b.Chiu su t mng Df phi tha mn cc iu kin sau:

- Nu cng trnh khng c tng hm, xung quanh khng c cng trnh ln cn, a cht

tng i thun li th n gin trong thi cng nh p cc, o thi cng i mng

chiu su t y i t 1,5 3,0m m

- Nu cng trnh c tng hm th cao mt trn ca i trng vi cao mt trn ca sn

tng hm thun tin trong thi cng v c li cho vic chu lc ca sn tng hm.

- Nu cng trnh xy chen (xung quanh gip ranh vi cc cng trnh ln cn) th chiu su

t i khng nn qu su v khi thi cng d nh hng n cc cng trnh ln cn.

- Cng cn lu rng, trong mng cc chng ta khng cn thit phi chn chiu su t i

sao cho tha mn lc ngang tc dng ln mng phi nh hn p lc tc dng ca t nn

v trong mng cc phi xt n cc chu ti trng ngang xc nh ni lc v ct thp

trong cc (s c kim tra phn cc chu ti trng ngang).

1.1.1c. ng ca vt liu lm cc:

- Nhng vn chung: cc BTCT ch to sn phi c thit k c th chu c gi tr ni

lc sinh ra trong qu trnh cu, vn chuyn, lp dng, thi cng h cc v chu ti vi h s

an ton v hp l.

+ ng sut cho php ln nht trong cc khi lm vic khng c vt qu 0.33fc .

+ ng sut cho php ln nht do p cc (c th sinh ra hai loi sng ng sut nn v

ko), khng c vt qu gii hn: 0.85fc (cho trng hp sng nn); 0.70 fy (cho

trng hp sng ko); (fc: cng chu nn khi nn tnh b tng; fy: gii hn do ca

thp).

- Yu cu v b tng: da trn iu kin lm vic ca cc, cp bn ti thiu cho b tng

cc c th ly nh sau:

Bng 1.1 Cp bn ti thiu ca b tng lm cc

iu kin p cc Mc b tng Cp bn ca b tng

tng ng Mc b tng (Mpa)

Cc phi p (ng) n chi rt nh

400 B30

iu kin bnh thng v d p

250 B20


NHM MNG CC Trang 4

- Yu cu v ct thp dc:

+ Ct thp dc phi tha mn cc iu kin quy nh v cht lng ct thp c th

chu c cc ni lc pht sinh trong qu trnh bc d, vn chuyn, cu lp v p lc

ko cc m-men un ca cng trnh bn tc dng vo cc, cng cn xt n tr ng sut

ko c th pht sinh do hin tng nng nn khi p (ng) cc cc tip theo.

+ Ct thp ch yu cn c ko di lin tc theo sut chiu di cc. Trong trng hp

bt buc phi ni ct thp ch, mi ni cn c tun theo quy nh v ni thp v b

tr mi ni ca cc thanh.

+ Trong trng hp cn tng kh nng chu m-men, thp c tng cng phn u

cc, nhng cn b tr sao cho s gin on t ngt ca ct thp khng gy ra hin

tng nt khi cc chu tc ng xung trong qu trnh p (ng) cc.

+ Trong cc trng hp bnh thng th ct thp dc c xc nh theo tnh ton, hm

lng thp khng nh hn 0,8% ng knh khng nn nh hn 14mm.

+ i vi nhng trng hp sau, nht l cc cc cho nh cao tng, hm lng ca ct

thp dc c th nng ln 1 1,2% khi:

Mi cc xuyn qua lp t cng;

mnh ca cc L/d > 60;

S cc trong i t hn 3 cc.

- Yu cu v ct ai:

+ Ct ai c vai tr c bit quan trng chu ng sut ny sinh trong qu trnh p

(ng) cc. Ct ai c dng mc, ai kn hoc xon. Tr trng hp c s dng mi

ni c bit hoc mt bch bao quanh u cc m c th phn b c ng sut gy ra

trong qu trnh p (ng) cc, trong khong cch bng 3 ln cnh nh ca cc ti hai

u cc, hm lng ct ai khng t hn 0,6% ca th tch vng nu trn.

+ Trong phn thn cc, ct ai c tng tit din khng nh hn 0,2% v c b tr vi

khong cch khng ln hn 200mm. S thay i cc vng c khong cch cc ai ct

khc nhau khng nn qu t ngt.

+ Thp gia cng u cc: thng thng u cc khng b b khi p (ng) hoc p

cc th nn dng li thp 6 50a gia cng u cc (thng b tr 4 lp).

1.1.2. TNH TON SC CHU TI CA C C:

n p i t n t c m c .1. V -2012)

- Trng thi gii hn th nht da vo sc chu ti.

- Trng thi gii hn th hai da vo bin dng ( l n, v ng..) gy cn tr vic

s dng nh bnh thng v cng trnh.

1.1.2.1. SC CHU TI CA C EO CA VT LIU: (3.3.2

TCXD 205-1998):

1.1.2.1.a. Cc chu ti trng tc thi khi p cc:


NHM MNG CC Trang 5

- Cng thc tnh ton:

Trong :

R: ng sut trong cc (kN/m2) c tnh nh sau:

+ Vi cc b tng ct thp: R=0.85fc (fc l cp bn ca b tng, kN/m2) - trch

3.3.2 tcxd 205 1998

: din tch tit din ngang ca cc (m2)

: h s un dc ca cc

21,028 0,0000288 0,0016

: mnh ca cc, =lo/r (cc trn hoc cc vung), = lo/b (cc ch nht).

r: bn knh ca cc trn hoc cnh cc vung

b: b rng ca tit din ch nht

l0: chiu di tnh ton ca cc c xc nh nh sau:

+ Khi p (ng) cc:

Hnh 1.1. Trng hp thi cng p (ng)

l0v=1


NHM MNG CC Trang 6

Vi:

v = 1.0 (thin v an ton xem ti v tr ni cc l lin kt khp, ti v tr lc tc dng khi

p cc nh ta n)

l chiu di on cc ln nht khi cha p vo t

1.1.2.1.b. Cc chu ti trng ca cng trnh lu di:

- Cng thc tnh ton:

Trong :

R: ng sut trong cc (kN/m2) c tnh nh sau:

+ Vi cc b tng ct thp: R=0.33fc (fc l cp bn ca b tng, kN/m2) - trch 3.3.2

tcxd 205 1998

: din tch tit din ngang ca cc (m2)

: h s un dc ca cc

21,028 0,0000288 0,0016

: mnh ca cc, =le/r (cc trn hoc cc vung), = le/b (cc ch nht).

r: bn knh ca cc trn hoc cnh cc vung

b: b rng ca tit din ch nht

l0: chiu di tnh ton ca cc c xc nh nh sau:

- Khi chu ti trng cng trnh


NHM MNG CC Trang 7

Hnh 1.2. Trng hp cc lm vic chu ti trng cng trnh

e bdl L Trong :

L - chiu su thc t.

bd :h s bin dng, I/m, xc nh theo cng thc: ( theo ph lc G3 TCXD

205-1998).

5c

bd

b

Kb

E I

Trong :

K - h s t l ly t bng G1 TCXD 205-1998 (ly theo lp t nh hng

di y i).

le


NHM MNG CC Trang 8

bc - Chiu rng quy c ca cc,m

bc=1.5d+0.5 (d=0.4m


NHM MNG CC Trang 9

m: H s iu kin lm vic ca t ln lt mi cc v mt bn cc c k

n nh hng ca phng php h cc n sc chng tnh ton ca t, xc

nh theo bng A.3 (TCXD205:1998)

Trong cng thc trn vic ly tng cng chu ti ca t phi c tin hnh trn

tt c cc lp t m cc xuyn qua. Trong trng hp khi san nn cn gt b hoc c th

b xi tri t i, phi tin hnh ly tng sc chng tnh ton ca tt c cc lp t nm

ln lt bn di mc san nn (gt b hoc di ct xi l cc b khi b l).

1.1.2.2.b. Sc chu ti ca cc t cng t nn:(ph lc B TCXD 205-

1998)

psa

s p

QQQ

FS FS

Trong :

sQ : sc khng hng cc hn (xung quanh cc).

pQ : sc khng mi cc hn.

sFS : h s an ton cho thnh phn ma st bn, ly bng 1,5-2,0.

pFS : h s an ton cho sc chng di mi cc ly bng 2,0-3,0.

Thnh phn chu ti do ma st xung quanh cc:

isis lfuQ

Trong :

u : chu vi cc

sif : thnh phn ma st n v gia cc v lp t th i (kN/m2)

: lc dnh gia cc v lp t th i, vi cc b tng ct thp ly

(kN/m2), trong ci l lc dnh ca t nn;

: gc ma st gia cc v t, cc p (ng) b tng ct thp ly

: ng sut hu hiu trong t theo phng vung gc vi mt bn cc

ca lp t th i (kN/m2)

il : chiu dy lp t th i (m)

Thnh phn sc chu mi ca t di mi cc:

ppp qAQ

Trong :

Ap tit din mi cc

qp sc chu ti n v mi cc

Tnh ton sc chu ti n v mi cc:


NHM MNG CC Trang 10

Trong :

c: lc dnh ca t ti mi cc (kN/m2),

: Dung trng ca t nn ti mi cc (kN/m3),

ng sut hu hiu ti mi cc (kN/m2).

qc ,N,NN : h s sc chu ti, ph thuc vo ma st trong ca t, hnh

dng mi cc v phng php thi cng.

Sc chu ti mi n v theo cng thc Vesic:

'. . .p c q vq cN N d N .

Bng 1.3. Gi tr cc h s sc chu ti theo ca Vesic (1973)

Nq Nc N Nq Nc N

0 1.00 5.14 0.00 24 9.60 19.32 9.44

1 1.09 5.38 0.07 25 10.66 20.72 10.88

2 1.20 5.63 0.15 26 11.85 22.25 12.54

3 1.31 5.90 0.24 27 13.20 23.94 14.47

4 1.43 6.19 0.34 28 14.72 25.80 16.72

5 1.57 6.49 0.45 29 16.44 27.86 19.34

6 1.72 6.81 0.57 30 18.40 30.14 22.40

7 1.88 7.16 0.71 31 20.63 32.67 25.99

8 2.06 7.53 0.86 32 23.18 35.49 30.21

9 2.25 7.92 1.03 33 26.09 38.64 35.19

10 2.47 8.34 1.22 34 29.44 42.16 41.06

11 2.71 8.80 1.44 35 33.30 46.12 48.03

12 2.97 9.28 1.69 36 37.75 50.59 56.31

13 3.26 9.81 1.97 37 42.92 55.63 66.19

14 3.59 10.37 2.29 38 48.93 61.35 78.02

15 3.94 10.98 2.65 39 55.96 67.87 92.25

16 4.34 11.63 3.06 40 64.20 75.31 109.41

17 4.77 12.34 3.53 41 73.90 83.86 130.21

18 5.26 13.10 4.07 42 85.37 93.71 155.54

19 5.80 13.93 4.68 43 99.01 105.11 186.53

20 6.40 14.83 5.39 44 115.31 118.37 224.63

21 7.07 15.81 6.20 45 134.87 133.87 271.75

22 7.82 16.88 7.13 46 158.50 152.10 330.34

23 8.66 18.05 8.20 47 187.21 173.64 403.65


NHM MNG CC Trang 11

2.2.2.2.c. Tnh ton sc chu ti ca t theo cng thc ca Nht Bn t kt qu

TN SPT:

Trong :

h s ph thuc vo phng php thi cng cc:

Cc b tng ct thp thi cng bng phng php p (ng):

Cc khoan nhi:

aN : ch s SPT ca t di mi cc;

sN : gi tr trung bnh ca ch s SPT trong lp t ri;

sL : chiu di phn cc nm trong lp t ri,m;

C : gi tr trung bnh ca s ba lc dnh n v trong lp t dnh,

cL : chiu di phn cc nm trong lp t dnh,m.

um: chu vi cc

2.2.2.2.d. Tnh ton sc chu ti ca t theo cng thc ca Meyerhof (1956) t

kt qu TN SPT: (TCXD 205-1998 mc C.2.2)

1 2u p tb sQ K NA K N A

ua

QQ

FS

Trong :

K1: h s, ly bng 400 cho cc p (ng) v bng 120 cho cc khoan nhi.

K2: h s, ly bng 2 i vi cc p v bng 1 i vi cc khoan nhi

N: ch s SPT trung bnh trong khong 1d di mi cc v 4d trn mi cc.

Ntb: ch s SPT trung bnh dc thn cc trong phm vi lp t ri

Ap: din tch tit din mi cc, m2

As: din tch mt bn cc trong phm vi lp t ri), m2

FS: h s an ton p dng khi tnh ton sc chu ti ca cc theo xuyn tiu

chun ly bng 2,5 3,0

Kt lun: Sc chu ti thit k

Thin v an ton, ti trng thit k phi ly gi tr c tin cy ln nht ca

cc gi tr sc chu ti Qai cho php tnh.( dng phng php bnh phng

cc tiu tnh gi tr c trng ca t nn max min4

6

tbtk

Q Q QQ

)

Ngoi ra, khi thi cng khng b ph hoi cc theo vt liu lm cc, sc

chu ti ca cc theo vt liu lm cc (trong trng hp thi cng cc) phi

ln hn sc chu ti cc hn ca cc theo ch tiu t nn.


NHM MNG CC Trang 12

1.1.2.3. KIM TRA SC CHU TI CA C

Kim tra cc chu ti trng tm thi ( khi p cc):

1

max

2 tkvl

u

QQ

Q

Cc chu ti trng lu di ( khi chu ti trng cng trnh):

2vl tkQ Q

1.1.3. O S B S NG C C: tt

c

tk

Nn

Q

Trong :

ttN : lc dc tnh ton ti chn ct (ngoi lc tc dng ln mng)

aTKQ : sc chu ti thit k ca cc

: h s xt n do moment v lc ngang ti chn ct, trng i v t nn

trn i, ty theo gi tr ca moment v lc ngang m chn gi tr hp l.

Thng = 1.2 1.5 .

nc: ch l s lng cc s b, cn c kim tra cc bc tip theo.

1.1.4.B TR C C:

Thng thng cc cc c b tr theo hng, dy hoc theo li tam gic.

Khong cch gia cc cc (t tim cc n tim cc): S = 3d 6d

(d: ng knh hay cnh cc), nu b tr trong khong ny th cc m bo c sc

chu ti v cc cc lm vic theo nhm.

t b nh hng n sc chu ti ca cc (do cc lm vic theo

nhm), th nn b tr cc ti thiu l 3d.

Khi b tr cc ln hn 6d th nh hng ln nhau gia cc cc c th b

qua, khi xem nh cc lm vic ring l.

Khi ti ng lch tm hoc kch thc i ln c th b tr sao cho phn lc u

cc tng i bng nhau.

Khong cch t mp ngoi ca cc n mp ngoi ca i t d d

3 2

Nn b tr cc sao cho tm ct trng vi trng tm ca nhm cc.


NHM MNG CC Trang 13

1.1.5. KI RA C

1.1.5.1.KIM RA U KIN XUYN TH O

1.1.5.1.a Di tc d ng ca lc dc, chiu cao ca i cc khng cao s b

xuyn thng, khng b xuyn thng hiu cao ca i cc phi tha mn iu kin

sau:

xt cxP P

Pxt lc gy xuyn thng (kN)

Pcx lc chng xuyn thng (kN)

1.1.5.1.b c t ng hp xuyn thng:

Gm hai trng hp xuyn thng nh sau:

ng hp 1: Khi cc cc u nm ngoi y ln ca thp xuyn thng (khi mt bn

ca thp xuyn nghing 1 gc 45o so vi trc thng ng):

Hnh 1.6. Khi mt bn ca thp nn thng nghing 450

bc

hc

h0

hd

h0

45


NHM MNG CC Trang 14

(y thp nn thng khng ph ln cc cc)

ng hp 2: Khi y ln ca thp xuyn 45o bao ph mt phn ca cc

- Trng hp ny thp xuyn thng c xc nh nh sau:

Hnh 1.7. Khi mt bn ca thp nn thng nghing gc nh hn 450

(y thp nn thng ng vi gc xuyn ph ln 1 phn cc)

45

a

bc

hc

h0

hd

c


NHM MNG CC Trang 15

1.1.5.1.c Xc nh lc gy xuyn thng (Pcx)

Lc xuyn thng Pcx ly bng lc tc dng ln thp xuyn thng, tr i phn lc u cc

nm hon ton trong phm vi thp xuyn thp xuyn thng:

( )

tt

xt i xtP N P

Trong :

ttN - lc dc tnh ton ti chn ct (ly t hp maxttN )

( )i xtP - phn lc u cc nm trong phm vi y ln thp xuyn thng.

thin v an ton phn lc u cc ch do lc dc gy ra (khng xt n moment, lc

ngang, trng lng bn thn i v t nn trn i) v c tnh vi h s vt ti n = 0.9.

( ) .0,91.15

ii xt

PP

Khi kim tra xuyn thng t cc ln i, moment v lc ngang khng gy ra xuyn thng, v

vy ch do lc dc ti chn ct gy ra xuyn thng. Ring xuyn thng t cc ln i, thin

v an ton th lc gy xuyn thng t cc ln i c xt n moment, lc ngang, trng lng

bn thn i v t trn i.

1.1.5.1.d Xc nh lc chng xuyn thng

- ng hp 1: Khi i khng t ct thp ai:

0( ) 0. . .cx cx bt mF P P R u h

Trong :

0h - chiu cao lm vic ca tit din (ly t mt trn ca i n trng tm lp di

ct thp ca i).

btR - cng chu ko ca b tng.

- h s, ly theo bng 1.5.

Bng 1.5 Xc nh h s

Loi b tng B tng nng B tng ht nh B tng nh

1,00 0,85 0,80


NHM MNG CC Trang 16

mu - gi tr trung bnh ca chu vi y trn v y di thp y thng hnh thnh khi b

nn thng, trong phm vi chiu cao lm vic ca tit din:

02( 2 )m c cu h b h

Ly sc chng xuyn thc t nhn vi 1 lng 0h

c, khi Pcx c tnh nh sau:

00( ) 0. . . .cx bt m

hP R u h

c

- ng hp 2: Khi i c t ct ai:

Khi trong phm vi thp xuyn thng c t cc ct thp ai thng gc vi mt y i, lc

chng xuyn thng c tnh ton nh sau:

0 0,8cx cx swP P F

cxP - lc chng xuyn ca i khi c t ct ai trong phm vi thp xuyn thng (gi tr ny

ly khng ln hn 2P0(cx).

0cxP - lc chng xuyn ca i khi khng t ct ai (ch do phn b tng chu).

swF - tng ton b lc ct do ct thp ai (ct cc mt bn ca khi thp) chu, c tnh theo

cng thc:

sw sw swF R A

y, swR khng c vt qu gi tr ng vi ct thp CI, A-1.

Khi k n ct thp ngang, Fsw ly khng nh hn 0,5P0(xt).

Khi b tr ct thp ai trn mt phn hn ch gn v tr t ti trng tp trung, cn thc hin

tnh ton b sung theo iu kin (mc 2) cho thp xuyn thng c y trn nm theo chu vi

ca phn c t ct thp ngang.

vng chu xuyn thng, ct thp ngang trong i mng c t vi bc khng ln hn

h/3 v khng ln hn 200mm, chiu rng vng t ct thp ngang khng nh hn 1,5h (vi

h l chiu dy i). Ct thp ngang phi c neo chc chn hai u bng cch hn hoc

kp cht ct thp dc, m bo bn ca lin kt v ca ct thp l tng ng.


NHM MNG CC Trang 17

1.1.5.2. KI RA U KIN C O C:

ng hp 1: lc chng ct ca b tng c tnh n ct ai: (Trch mc 6.2.3.3

TCVN 5574-2012)

2

2 (1 )b f n bt oR bhQ

c

Trong Q khng nh hn 3 0(1 )b f n btR bh

- b3 xt nh hng ca b tng ly nh sau

+ i vi b tng nng v b tng t ong b3 = 0,6

+ i vi b tng ht nh b3 = 0,5

+ i vi b tng nh c mc theo khi lng th tch trung bnh

D 1900: b3 = 0,5

D 1800: b3 = 0,4





D 1900 b2 = 1,9

D 1800: dng ct liu nh c b2 = 1,75

dng ct liu nh rng b2 = 1,5

- f h s xt n nh hng ca cnh chu nn trong tit din ch T, ch I

(f = 1)

- n h s nh hng ca lc dc:

0.1 0.1nbt o bt o

N H

R bh R bh

- c chiu di hnh chiu ca tit din nghing nguy him nht ln mt mng theo

phng ang xt.

ng hp 2 : lc chng ct ca b tng khng tnh ct ai : (Trch mc 6.2.3.4

TCVN 5574-2012)

2

4 (1 )b n bt oR bhQc

Trong :

V phi ca cng thc trn ly khng ln hn 02,5 bR bh v khng nh hn

3 0(1 )b n btR bh (h s b3 ly tng t trng hp 1)






NHM MNG CC Trang 18

D 1900 b4 = 1,2

D 1800: dng ct liu nh c b4 = 1,0

- H s n v c c xc nh nh trng hp 1

Hnh 1.8. Vt nt xin

1.1.6. P O

1.1.6.1. S tnh:

Xem i l bn consol c mt u ngm vo mp ct v u kia t do, vi gi thit

i l tuyt i cng


NHM MNG CC Trang 19

Hnh 1.9. S cc tc dng lc ln i

1.1.6.2. Ngoi lc tc d ng

Ngoi lc tc dng ln i l phn lc u cc trong phm vi ca dm consol.

Thng thng i vi mng nng, khi tnh ton ct thp th ti trng tc dng l

ti trng rng (khng xt n trng lng bn thn mng v t nn trn mng).

Tuy nhin khi tnh i cc, v hu nh tt c cc lc u truyn ln cc cc, c

bit l i cc nm trong lp t yu v vy, phn lc t nn (t yu) khng

kh nng chu c trng lng i v t nn trn i.

V vy, thin v an ton, khi tnh ton ct thp trong i cc, ngoi ngoi lc tnh

ton tc dng ln cc, cn xt n trng lng bn thn i v t nn trn i.

1.1.6. . Xc n m m nt t ng i c c ai p ng)

i iM = P l Trong :

M: moment trong i ti mp ct

Pi : phn lc u cc th i tc dng ln bn consol

li : khong cch t lc Pi n mp mt ngm ca bn consol.

1.1.6.4. Tnh ton ct thp

Tnh thp cho i nh thanh chu un tit din ch nht :

m

b b 0

M =

R bh

m = 1 - 1 - 2

0A R b bss

R bh

R


NHM MNG CC Trang 20

1.1.7. KIM TRA SC CHU TI CA C C V NHM C C :

1.1.7.1. Kim tra sc chu ti ca cc n

Ti trng tc dng ln cc :

max 2 2

tttt tt

y i x i

i i

M xN M yP

n x y

Trong :

n : s lng cc

xi, yi : khong cch t tim cc th i n trc i qua trng tm cc cc ti mt

phng y i

ttxM : tng moment ti y i quay quanh trc x ti trng tm nhm cc

ttyM : tng moment ti y i quay quanh trc y ti trng tm nhm cc

Kim tra sc chu ti ca cc :

max

min 0

aTKP Q

P

Nu Pmin < 0, th phi kim tra cc chu nh:

Qa nh + W > minP

W: trng lng ca cc (ly h s vt ti do trng lng bn thn < 0.9)

Qa nh: sc chu nh an ton ca cc (sc chu ti cho php ca cc do phn ma

st gy ra).

Khi kim tra cc chu nh nn kim tra kh nng chu lc ti cc mi ni cc v kh nng

chu ko ca cc.

Cng cn lu rng, cng thc xc nh phn lc u cc trn c quan nim l i

cc cng tuyt i. V vy, khi i cc c kch thc ln nh mng cc i bng hoc

i b th i khng c xem l cng tuyt i. V vy, khi xc nh ni lc trong i

v phn lc u cc, th cn gii theo phng php phn t hu hn.

1.1.7.2. Kim tra sc chu ti ca nhm cc:

- H s nhm:

21

1221

90

)1()1(1

nn

nnnn


NHM MNG CC Trang 21

Trong :

arctand

s

d : ng knh cc, m

s : khong cch gia cc cc, m

1n : s hng cc

2n : s cc trong mi hng

Sc chu ti ca nhm cc:

nh

a aQ n Q

1.1.8.KIM TRA NH CA T N D V

LN MNG C C:

1.1.8.1. Xc n k c t c khi mng quy c:

D tnh ln ca nhm cc c da trn m hnh mng khi quy c. C ba cch xc

nh mng khi quy c nh sau:

ng hp 1: Cc i qua nn nhiu lp

n 1.1 Mng khi quy c cc i qua nhiu lp t

b

LTB

B D

A C


NHM MNG CC Trang 22

Ranh gii mng quy c

Pha di l mt phng AC i qua mi cc c xem l y mng;

Pha trn l mt t san nn BD, vi AB = l su t mng (t mt t n cao

trnh mi cc);

Pha cnh l cc mt phng ng AB v CD qua mp ngoi cng ca hng cc bin

ti khong cch Ltb tan / 4tb nhng khng ln hn 2d (d: ng knh hoc cnh cc

vung) khi di mi cc c lp st bi vi ch s st IL> 0,6; khi c cc xin th cc mt

phng ng ni trn i qua mi cc xin ny:

i itb

tb

l

L

Trong :

i : gc ma st trong ca lp t c chiu dy li

Ltb: su h cc trong t k t y i, tb iL l .

Ch thch:

Nu trong chiu di ca cc c lp t yu (bn, than bn) dy hn 30 cm th kch

thc y mng quy c gim i bng cch ly Ltc l khong cch t mi cc n y

lp t yu;

Trng lng bn thn ca mng quy c gm trng lng cc v t nm trong phm

vi mng quy c.

ng hp 2: Cc i qua nn ng nht

n 1.11 Mng khi quy c qua nn ng nht.

b

LTB

B D

A C

2/3LTB

1/3LTB

o


NHM MNG CC Trang 23

Ranh gii mng quy c k i t nn l ng nht

Cch xc nh mng quy c tng t cch 1, ch khc l ly gc ma st bng 30o cho

mi loi t k t su 2Ltb/3

Ranh gii ca mng quy c khi cc xuyn qua mt s lp t yu ta vo lp t

cng cch xc nh mng quy c nh m t trong cch 1, ring gc m ly bng 30o k

t su 2L1/3, vi L1 phn cc nm di lp t yu cui cng

Ranh gii ca mng quy c khi t nn nm trong phm vi chiu di cc gm nhiu

lp c sc chu ti khc nhau.

Chiu rng v chiu di bn mng quy c l y hnh khi c cnh m rng so vi

mt ng ca hng cc bin bng cho n su 2Ltb/3, t tr xung n mt

phng mi cc gc m bng 30o.

su t mng quy c l ti mt phng mi cc.

ng sut ph thm phn b trong t nn, di mi cc c th tnh ton theo li gii

Boissinesq vi gi thit bn mng quy c t trn bn khng gian n hi.

ln ca mng quy c c tnh theo phng php quen bit nh i vi mng

nng trn nn thin nhin.

ng hp 3: Cc i qua lp t yu v lp t tt

n 1.1 Cc i qua lp t yu v lp t tt

b

LTB

B D

A C

2/3LTB

1/3LTB

o


NHM MNG CC Trang 24

1.1.8.2. Kim tra n n t nn di y mng k i quy c:

iu kin n nh nn di mng khi quy c l:

tc

tc II

tb qu

qu

Np R

A

max 1.2

tc

tc II

tb qu

qu

Mp p R

W

min 0

tc

tc

tb

qu

Mp p

W

Trong :

tctbp - p lc trung bnh tiu chun di y mng khi quy c.

max

tcp - p lc ln nht di mng khi quy c.

min

tcp - p lc nh nht di y mng khi quy c.

tcN - tng lc dc ti tm y mng khi quy c (bao gm lc dc ti chn ct, trng lng bn thn ca i cc, cc, t trn i v phn t nm trong

mng khi quy c).

tcM - tng moment y mng khi quy c ly bng M ti tm y i

quW - moment chng un ca tit din mng khi quy c (2

6

qu qu

qu

B LW khi moment

quay theo hng Lqu hoc ngc li 2

6

qu qu

qu

L BW khi moment quay theo hng Bm)

Lqu, Bqu- chiu di v chiu rng ca mng khi quy c.

II

quR - sc chu ti ca t nn di y mng khi quy c (tnh ton theo trng thi

gii hn th II, ging nh mng n).

1.1.8.3. Kim t a ln ca mng khi quy c:

gh

S S

ghS - ln gii hn c xc nh theo bng H.2 (TCXD205:1998)

S ln trung bnh ca t nn di y mng khi quy c

Cc bc tnh ln ca mng khi quy c theo phng php tng phn t.


NHM MNG CC Trang 25

Bc 1: Xc nh p lc gy ln

'tc

gl tb i ip p h

'

i ih - ng sut c hiu theo phng ng do trng lng bn thn t nhin ca t nn gy ra ti y mng khi quy c.

tc

tbp - p lc tiu chun trung bnh ca t nn di y mng khi quy c.

Bc 2: Chia lp phn t

Chiu dy ca lp phn t c xc nh theo iu kin sau:

(0.4 0.6)i quh B

Tuy nhin, hin nay v c cc chng trnh tnh ton bng my tnh nn chiu dy lp

phn t nn chia cng nh t c chnh xc cao.

Bc 3: Xc nh ln ca lp phn t th i. chiu dy hi

B3.1. Xc nh 1i : ng sut trung bnh chnh gia lp t th I trc khi c cng

trnh (do trng lng bn thn t nn gy ra (c hiu ))

1 ' 'i v i ih

B3.2. Xc nh 2i : ng sut trung bnh chnh gia lp t th I sau khi c cng

trnh (do trng lng bn thn t nn gy ra v ng sut do pgl gy ra ti chnh gia lp

t th i).

2 1i i zi

zi - ng sut do pgl gy ra ti chnh gia lp t th I, c tnh theo ng sut do ti

trng ngoi phn b u gy ra. 0.zi glk p

k0 ph thuc vo ,qu

qu qu

Lz

B B

c tra bng 1.4:


NHM MNG CC Trang 26

Bng 1.4 Bng xc nh h s k0 (Bng C1 TC N 362)

B3.3. Xc nh ln Si 1 211

i ii i

i

e eS h

e

1ie - h s rng ca t gia lp t th I trc khi c cng trnh, ng vi 1i , c

ni suy t ng cong nn ln (e, ) ca lp t c lp phn t th i.

2ie - h s rng ca t gia lp t th I sau khi c cng trnh, ng vi 2i , c

ni suy t ng cong nn ln (e, ) ca lp t c lp phn t th i.

Bc 4: iu kin tnh ln trong phm vi nn

' 5vi zi

Khi t iu kin trn th t nn c xem l n khng ng k.

Cng lu rng, iu kin trn p dng cho mng nng, nhng i vi mng khi

quy c, mc gim ng sut do ti trng ngoi gy ra gim rt chm theo su, v

vy nn tnh ln cho tt c cc lp n khi no ln Si rt nh so vi tng ln th

dng phn tnh ln.


NHM MNG CC Trang 27

Bc 5: Xc nh tng ln ca nn theo phng php tng phn t

iS S

1.1.9. KIM TRA C C CHU CU LP:

Khi b tr cc mc cu trong cc, nn b tr sau cho moment cn th trn v moment cn th di bng nhau. Mt s trng hp c bit nh sau:

- S mc cu (thng trong iu kin dng cc)

Hnh1.13. S b tr mc cu trong trng hp dng cc

2

1 0.068M qL

- S 2 mc cu (thng trong iu kin cu cc):

0.293L

L

M1

q

0.207L 0.207L

L

M2


NHM MNG CC Trang 28

Hnh 1.14. S b tr mc cu trong trng hp cu cc

2

1 0.0214M qL

Ghi ch: Trong trng hp cc ch b tr 2 mc cu th thng dng mc cu trong

s cu cc dng cc, khi moment ln nht trong cc l 20,068M qL .

ng q: ti trng bn thn ca cc quy v phn b theo chiu di c tnh theo

cng thc: q=K d2 (K=(1.2-2) s ng ph thuc vo phng php vn chuyn cc)

1.1.10. NG D NG SAP2000 KIM TRA C C CHU TI NGANG:

Ti trng ngang tc dng ln cc c tnh bi

Trong :

H: lc ngang tc dng vo i mng (kN).

n: s lng cc

Khi tnh ton cc chu ti ngang, t quanh cc c xem nh mi trng n hi bin dng

tuyn tnh c trng bng h s nn Cz.

Trong :

- K: h s t l, kN/m4, c ly theo bng G1 tiu chun 205-1998:

- z: su v tr cc, m, k t mt t i vi cc i cao, hoc y mng i vi

cc i thp.

y n gin trong qu trnh gn iu kin bin ca h s nn ta chn K, z ti v

tr gia lp cn xt, ri ly cng em gn cho tng lp t.

Ti mt phn cch cc lp t ta tnh ring cc h s n hi ( cng ca l xo khi

khai bo) mang c tnh ca c lp trn v lp di nn ta s tnh ring cc gi tr ti cc lp

phn cch ny).

Ch dn sa d ng SAP2000:

File->New model-> Grid Only->Ok


NHM MNG CC Trang 29

Hnh 1.15. ng dn SAP2000

Hiu chnh li ct: Kch chut chn Edit -> Modify/Show System->OK



NHM MNG CC Trang 30


Hiu chnh li ct vi khong cch l b dy cc lp t (z), cc ct (x,y ).

Khai bo vt liu: Define-> Materials-> Add New Material-> Chn vt liu l

Concrete-> Weight =0 (khng cn xt n trng lng bn thn cc)-> nhp Modul E

vi tng loi b tng->OK


NHM MNG CC Trang 31


.

Khai bo tit din cho cc: Define-> Frame Sections: To cc COCc kch thc l

kch thc ca cc.


Khai bo tit din cho i cc: Define-> Area-> Sections..: To cc COCc kch

thc l kch thc ca cc.


NHM MNG CC Trang 32



NHM MNG CC Trang 33

Dng Draw Frame/Cable Element v cc v Quick Draw Area Element v i cc


Gn tit din b tng vo cc: Chn cc-> Assign-> Frame-> Frame sections->chn

COC.


NHM MNG CC Trang 34


Gn tit din b tng vo i cc: Chn i cc-> Assign->Area->Sections->chn

DAI COC.

Chia 4 cc thnh tng on gn iu kin bin: Chn cc ->Edit ->Edit lines->

Devide Frames-> Nhp s on cn chia vo Devide into Specified Number-> OK.


NHM MNG CC Trang 35


Gn cng l xo cho cc on va mi chia: Chn i tng cn gn-> Assign -

>Joint -> Springs : Nhp cc h s nn Cz va tnh c.(iu chnh h trc ta

sang h trc Global).


Gn ti trng ln cc: Chn trng tm ca i cc-> Assign ->Joint Loads-> Forces

ri nhp ti trng.


NHM MNG CC Trang 36


Chy chng trnh SAP2000: bm F5-> Run Now.

Xem kt qu gii ni lc SAP2000:


Xem chuyn v

Hnh 1.27. ng dn SAP2000 Xem momen


NHM MNG CC Trang 37

1.1.11. S L THUY T KIM TRA C C CHUYN V NGANG:

(Tnh ton theo phng php ca SNIP II 17 77)

Chuyn v ngang v gc xoay ca u cc tha mn iu kin sau:

Trong :

, - nhng gi tr tnh ton tng ng chuyn v ngang (m), v gc xoay (radian)

ca u cc.

, - nhng gi tr tng ng chuyn v ngang (m), v gc xoay (radian) ca u

cc. c quy nh t nhim v thit k nh cng trnh.

Khi tnh ton cc chu ti trng ngang, t quanh cc c xem nh mi trng n hi

bin dng tuyn tnh c trng bng h s nn Cz (kN/m3).

Khi khng c nhng s liu th nghim, cho php xc nh s liu tnh ton ca h s

nn Cz ca t quanh cc theo cng thc:

Trong :

K h s t l (kN/m4) c ly theo bng G1 (TCXD 205:1998).

Z su v tr tit din cc (m ) k t mt t i vi cc i cao, hoc k t mt t

i vi cc i thp.

Bng G1- h s t l K


NHM MNG CC Trang 38

Tt c tnh ton c thc hin theo chiu su tnh i ca v tr tit din cc trong t

v c chiu su tnh i h cc trong t xc nh theo cng thc sau:

Trong :

Z, l chiu su thc t v tr tit din cc trong t v chiu su h cc thc t (mi cc)

trong t tnh t mt t vi cc i cao v t y i vi cc i thp (m).

- h s bin dng (1/m) xc nh theo cng thc:

Trong :

K h s t l (kN/m4)

Eb m un n hi ban u ca b tng cc khi nn v ko (kN/m2), ly theo

tiu chun b tng ct thp.

I momen qun tnh tit din ngang ca cc (m4)

bc chiu rng quy c ca cc (m), c ly nh sau:

Khi d 0.8 th ly bc = d + 1m

Kkhi d < 0.8 th ly bc = 1.5d +0.5m

Tnh ton chuyn v ngang ca cc theo cng thc:


NHM MNG CC Trang 39

Trong :

H v M gi tr tnh ton ca lc ct (kN) v momen un (kNm) ti u cc.

chiu di on cc (m) bng khong cch t y i cc n mt t.

y0, chuyn v ngang (m) v gc xoay ca tit din ngang ca cc (radian)

mt t vi cc i cao, mc y i vi cc i thp v c xc nh nh

sau:

Trong :

H0 gi tr tnh ton ca lc ct (kN), ly H0 = H

M0 gi tr tnh ton ca lc ct (kNm), ly M0 = M + Hl0

chuyn v ngang ca tit din (m/kN) bi lc H0 = 1

chuyn v ngang ca tit din (1/kN) bi momen M0 = 1

gc xoay ca tit din (1/kN) (hoc kNm) bi lc H0 = 1

gc xoay ca tit din (1/kN) (hoc kNm) bi lc M0 = 1

Chuyn v = v v c xc nh theo cng thc:

Trong :

- cc h s khng th nguyn ly theo bng G2 (TCXD 205:1998) ty

thuc vo chiu su tnh i ca phn cc trong t le, khi le nm gia hai gi tr

trong bng G2 th ly theo gi tr gn hn tra bng


NHM MNG CC Trang 40

1.1.12. TNH TON NI LC TRONG C C (theo TCXD 205 -1998)

Khi tnh n nh ca nn quanh cc, phi kim tra iu kin hn ch p lc tnh ton

ln t mt bn ca cc theo cng thc

Trong :

p lc tnh ton ln t (kN/m2) mt bn ca cc ti su z (m) k t mt t cho

cc i cao v t y i cho cc i thp.

khi lng th tch tnh ton ca t (kN/m3)

- ng sut c hiu theo phng thng ng trong t (kN/m2) ti su z.


NHM MNG CC Trang 41

gi tr tnh ton ca gc ma st trong () v lc dnh (kN/m2)

h s, ly bng 0.6 cho cc nhi v cc ng, bng 0.3 cho cc cc cn li

h s, ly bng 1 tr trng hp tnh mng cho cc cng trnh chn ly bng 0.7

h s k n phn ti trng thng xuyn trong tng ti trng, tnh theo cng thc:

momen do ti trng thng xuyn (kNm) tnh ton tit din mng ti mc m cc

momen do ti trng tm thi (kNm)

n h s, ly bng 2.5 tr cc trng hp sau y

a) Nhng cng trnh quan trng

+ khi le 2.5 ly n = 4

+ khi le 5 ly n = 2.5

+ khi le nm gia cc tr s trn th ni suy n

b) Mng mt hng cc chu ti trng lch tm thng ng, nn ly n = 4 khng ph

thuc vo le .

Ch thch:nu p lc ngang tnh ton ln t khng tha mn iu kin trn nhng

lc ny sc chu ti ca cc cha tn dng ht v chuyn v ca cc nh hn tr s cho php

khi chiu su tnh i ca cc le> 2.5 th nn lp li vic tnh ton vi h s t l K gim i

(iu G.2 ca TCXD 205:1998). Vi tr s mi ca K cn kim tra bn ca cc theo vt

liu, chuyn v ca cc cng phi tun theo iu G.14

Khng cn tnh ton n nh t nn quanh cc c b rng tit din d m, vi chiu

di trong t ln hn 10d, tr trng hp cc c h vo bn hoc t st trng thi

chy hoc do chy.

p lc (kN/ ), moment un (kNm), lc ct (kN) trong cc tit din cc c

tnh theo cng thc sau (trch t mc G7 ph lc G ca TCXD 205:1998):

(

)


NHM MNG CC Trang 42

Trong :

K h s t l

, c ngha nh cc cng thc ni phn trc

chiu su tnh i, ty theo su thc t z m xc nh , , .

c ngha nh ni phn trc

A1, A3, A4, B1, B3, B4,C1,C3,C4, D1, D3, D4 cc h s tra bng G3

N ti trng tnh ton dc trc ti u cc.

Momen ngm tnh ton Mng (kNm) khi tnh cc ngm cng trong i v u cc khng b

xoay, tnh theo cng thc sau:


NHM MNG CC Trang 43

y ngha ca cc k hiu u ging nh nh cng thc nu trn. Du m c

ngha l vi lc ngang hng t tri sang phi, momen truyn ln u cc t pha ngm c

hng ngc vi chiu kim ng h.

2.1.CC D LIU TNH TON:

2.1.1.THNG K S LIU A CHT 1B (trch t phn I):

Chn v tr t mng ti h khoan 3 (HK 3) c cc s liu a cht di bng sau:

Bng 2.1:Thng k a cht ti h khoan 3 (HK3).

STT

Lp Dung trng t nhin Dung trng y ni

Lc dnh C (kN/m2) Gc ma st trong (o) (

su m) (kN/m3) (kN/m3)

tc 1 2 tc 1 2 Ctc C1 C2 tc 1 2

1

2a

18,99

9,255

9,542

6,884 8,057

121'

1017' 113'

(-1.3-

>-3.4) 12,2 11,027 1343' 1258'

2

2b

20,033

10,407

18,27

16,148 17,018

1524'

1452' 155'

(-3.4-

>-3.4) 20,386 19,516 1556' 1543'

3

3

19,81

10,04

33,164

21,237 25,886

1440'

1359' 1415'

(-3.4-

>-5.0) 45,09 40,441 1519' 153'

4

4

19,435

19,302 19,357

9,815

9,726 9,762

14,242

12,497 13,164

144'

1323' 1340'

(-5.0-

>-8.6) 19,568 19,514 9,904 9,868 15,987 15,32 1444' 1428'

5

5

19,4

19,264 19,324

9,875

9,761 9,811

7,294

3,807 5,162

1349'

1257' 1317'

(-8.6-

>-

11.0)

19,536 19,476 9,989 9,939 10,782 9,427 1441' 1422'

6

6a

18,508

18,44 18,47

9,301

9,25 9,27

2,739

0,195 1,142

2647'

2614' 2627'

(-11->-

15) 18,58 18,55 9,36 9,34 5,263 4,316 2719' 277'

7

6b

19,248

19,185 19,209

9,901

9,851 9,869

2,943

1,33 1,91

2935'

2915' 2923'

(-15->-

40.7 19,311 19,288 9,951 9,932 4,47 3,89 2954' 2946'

8

7

20,22

20,19 20,202

10,53

10,485 10,504

38,063

33,797 35,424

1647'

1543' 167'

(-40.7-

>-

50.0)

20,25 20,238 10,575 10,556 42,328 41,701 1750' 1726'


NHM MNG CC Trang 44

2.1.2.S LIU TNH TON:

Hnh 2.1 Hnh 2.2

2.1.3.KHAI BO VT LIU:

- B tng B30c Rb=17Mpa=17000kN/m2; B20c Rb=11.5Mpa=11500kN/m

2

- Thp AII c Rs=280Mpa= 280000kN/m2.

2.2.TRNH T TNH TON V THI T K MNG C C:

2.2.1.CH N CHIU SU CHN MNG Df V C C S

B:

- Chn thi cng cc ch to sn, bin php thi cng p cc.

- Chn chiu su t i cc: m 0.2fD

- Chn cc thng s v cc:

Kch thc tit din cc : 0.4m x 0.4m 2m 16.0pA

Chn chiu di cc l : 10m x 3 =30 m

Vi chiu di ca cc nh vy th mi cc s cm vo lp 6b l lp t ct

Chn chiu cao i : 0.8 mdh

on cc ngm vo i : 0.6 m

on cc neo vo i l : m 1.0nl

=> su t y i n mi cc: l=30-0.6=29.4 m

Din tch ct thp (theo tiu chun 205-1998 mc 3.3.3.b):

4 2(0.8% 1.12%) 16 10 (0.8% 1.12%) 1280 1792 mms pA A = =


NHM MNG CC Trang 45

Chn ct dc : 422

Chn din tch thp trong cc : 22

mm 15214

224

sA

Chn ct ai : 10a200

2.2.2. TNH TON SC CHU TI CA C C:

2.2.2.1. SC CHU TI CA C EO CA VT LIU: (3.3.2

TCXD 205-1998):

2.2.2.1.a. Cc chu ti trng tc thi khi p cc:

1vl bQ A R

Trong :

- R: cng chu nn tnh ton ca b tng B30 lc p cc R=30x0.85=25.5 Mpa

- Ab=0.4x0.4=0.16 (m2) din tch tit din ngang ca cc b tng.

- : h s nh hng bi mnh ca cc tnh theo cng thc thc nghim .

=1.028-0.0000288x 2-0.0016x

=l0/r

Khi pcc :0

0

10. 1 10 10( ); 25

0.4

ll l x m

r

(khi p cc xem cc 2 u khp)

=1.028-0.0000288x 252-0.0016x 25=0.97

- Sc chu ti khi p cc:

3

1 0.97 0.16 25.5 10 3957.6( )vl bQ A R x x x kN

2.2.2.1.b. Cc chu ti trng ca cng trnh lu di:

2vl bQ A R

Trong :

- R: cng chu nn tnh ton ca b tng B30lc cc chu ti trng cng trnh lu

di R=30x0.33=9.9Mpa

- Ab=0.4x0.4=0.16 (m2) din tch tit din ngang ca cc b tng.

- : h s nh hng bi mnh ca cc tnh theo cng thc thc nghim .

=1.028-0.0000288x 2-0.0016x


NHM MNG CC Trang 46

=le/r

- Khi chu ti trng cng trnh

e bdl L Trong :

- L=29.4m chiu su thc t.

- bd :h s bin dng,I/m, xc nh theo cung thc:

5c

bd

b

Kb

E I

Trong :

- bc=1.5d+0.5=1.5x0.4+0.5=1.1m (d=0.4mH s bin dng:

- Chiu di cc trong t tnh i:

18.0245.05

0.4

el

r

=1.028-0.0000288x 45.052-0.0016x 45.05=0.897


NHM MNG CC Trang 47

- Sc chu ti khi p cc:

3

2 0.897 0.16 9.9 10 1421.6( )vl bQ A R x x x kN

. . . . X NH SC CHU TI CA T NN: (3.3.2 TCXD 205-1998):

2.2.2.2.a. Sc chu ti ca cc theo ch tiu c l ca t nn (ph lc A-TCXD 205-

1998): tcatc

QQ

K

Trong :

- : 1.6 ( ty thuc vo s lng cc ly theo A1-TCXD 205-1998).

- : sc chu ti tiu chun tnh theo t nn ca cc n.

( )tc R p p f si iQ m m q A u m f l m= 1 (h s iu kin lm vic ph thuc no nc lp t).

mR=1.1 (h s iu kin lm vic ca t di mi cc). (A3-

TCXD205-1998)

mf=1 (h s iu kin lm vic ca t mt bn cc). (A3-TCXD205-

1998)

qp=3800 kN/m2vi su mi cc=29.4m.(A1-TCXD205-1998).

Ap=0.16m2 tit din cc

Bng 2.2:Thng k ma st hng theo ch tiu c l

p z (m)

su t ung b n i

(m)

iu dy t c t cc (m)

ui

(m)

ng t i t

Ma st

hng

n v fs

(T/m2)

s iu kin lm

vic m

a st bn Qsi

2a 2

1.4 1.4

1.6 0.5 1.4 1

3.136 3.4

3 3.4

2.9 1.6

1.6 0.23 4.92 1

12.595 5

4

5 4.6 1.8 1.6 0.3

3.92 0.96 11.290

6.8

6.8 6.4 1.8 1.6 0.39

3.25 0.98 9.360

8.6

5

8.6 7.9 1.2 1.6 0.76

0.88 0.9 1.690

9.8

9.8 9.1 1.2 1.6 0.76

0.88 0.9 1.690

11

6a

11 10.7 2 1.6

Ct mn 4.67 1 14.944

13

13 12.7 2 1.6 4.87 1 15.584


NHM MNG CC Trang 48

15

6b

15 14.7 2 1.6

Ct va n mn

5.07 1 16.224

17

17 16.7 2 1.6

5.27 1 16.864

19

19 18.7 2 1.6

5.47 1 17.504

21

21 20.7 2 1.6

5.67 1 18.144

23

23 22.7 2 1.6

5.87 1 18.784

25

25 24.7 2 1.6

6.07 1 19.424

27

27 26.7 2 1.6

6.27 1 20.064

29

29 28.7 2 1.6

6.47 1 20.704

31

31 29.9 0.4 1.6

6.59 1 4.218

31.4

Qsi 2222.176

( ) 1 (1.1 3800 0.16 2222.176) 2890.976( )tc R p p f si iQ m m q A u m f l kN

Sc chu ti cc theo ch tiu c l 12890.976

1806.86( )1.6

tca

tc

QQ kN

K

2.2.2.2.b. Sc chu ti ca cc t cng t nn:(ph lc B TCXD 205-1998)

2

psa

s p

QQQ

FS FS

Trong :

- sQ : sc khng hng cc hn (xung quanh cc)

- pQ : sc khng mi cc hn

- FSs : h s an ton ca ma st hng (FSs=2)

- FSp: h s an ton ca sc khng mi cc (FSp=3)

Thnh phn chu ti do ma st xung quanh cc:

isis lfuQ

Trong :

- u : chu vi cc


NHM MNG CC Trang 49

- sif : thnh phn ma st n v gia cc v lp t th i (kN/m2)

-

: lc dnh gia cc v lp t th i, vi cc b tng ct thp ly

(kN/m2).

: gc ma st gia cc v t, cc p b tng ct thp ly

: ng sut hu hiu ca lp t th i (kN/m2),

trong bng

thng k.

- il : chiu dy lp t th i (m)

Bng 2.3: Tnh ton thnh phn chu ti do ma st xung quanh cc.

p z (m) li (m) ui(m) i ci

(kN/m2)

'i (kN/m

3)

i (kN/m

2)

si

(kN/m2)

Qsi (kN)

2a 2

1.4 1.6 10.283 6.884 9.255 12.957 6.750 15.120 3.4

3 3.4

1.6 1.6 13.983 21.237 10.04 27.468 20.053 51.336 5

4 5

3.6 1.6 13.383 12.497 9.726 53.006 18.440 106.215 8.6

5 8.6

2.4 1.6 12.95 3.807 9.761 82.226 17.336 66.568 11

6a 11

4 1.6 26.23 0.195 9.25 112.440 31.051 198.728 15

6b 15

16.4 1.6 29.25 1.33 9.851 211.718 61.564 1615.438 31.4

Qs Tng thnh phn chu ti do ma st xung quanh cc 2053.4048

Thnh phn sc chu mi ca t di mi cc:

ppp qAQ

Trong :

-

-

Tnh ton sc chu ti n v mi cc: (TCXD 205-1998):

Trong :

- c: lc dnh ca t ti mi cc (kN/m2), 21.33 kN/mc

- : Dung trng ca t nn ti mi cc (kN/m3), 39.851 kN/m


NHM MNG CC Trang 50

- ng sut hu hiu ti mi cc (kN/m2).

- qc ,N,NN : h s sc chu ti, ph thuc vo ma st trong ca t, hnh dng mi

cc v phng php thi cng.

Bng 2.4: ng sut hu hiu bn thn lp t nn.

z

(m) li (m)

'i (kN/m

3)

i = 'i *li

(kN/m2)

2a 1.3

2.1 9.255 19.436 3.4

3 3.4

1.6 10.04 16.064 5

4 5

3.6 9.726 35.014 8.6

5 8.6

2.4 9.761 23.426 11

6a 11

4 9.25 37.000 15

6b 15

16.4 9.851 161.556 31.4

ng sut hu hiu bn thn t nn ti mi cc 'v

292.496

Bng 2.5: Bng tra cc h s sc chu ti tnh theo cng thc ca Vesic.

Nq Nc N Nq Nc N

0 1.00 5.14 0.00 24 9.60 19.32 9.44

1 1.09 5.38 0.07 25 10.66 20.72 10.88

2 1.20 5.63 0.15 26 11.85 22.25 12.54

3 1.31 5.90 0.24 27 13.20 23.94 14.47

4 1.43 6.19 0.34 28 14.72 25.80 16.72

5 1.57 6.49 0.45 29 16.44 27.86 19.34

6 1.72 6.81 0.57 30 18.40 30.14 22.40

7 1.88 7.16 0.71 31 20.63 32.67 25.99

8 2.06 7.53 0.86 32 23.18 35.49 30.21

9 2.25 7.92 1.03 33 26.09 38.64 35.19

10 2.47 8.34 1.22 34 29.44 42.16 41.06

11 2.71 8.80 1.44 35 33.30 46.12 48.03

12 2.97 9.28 1.69 36 37.75 50.59 56.31

13 3.26 9.81 1.97 37 42.92 55.63 66.19

14 3.59 10.37 2.29 38 48.93 61.35 78.02


NHM MNG CC Trang 51

15 3.94 10.98 2.65 39 55.96 67.87 92.25

16 4.34 11.63 3.06 40 64.20 75.31 109.41

17 4.77 12.34 3.53 41 73.90 83.86 130.21

18 5.26 13.10 4.07 42 85.37 93.71 155.54

19 5.80 13.93 4.68 43 99.01 105.11 186.53

20 6.40 14.83 5.39 44 115.31 118.37 224.63

21 7.07 15.81 6.20 45 134.87 133.87 271.75

22 7.82 16.88 7.13 46 158.50 152.10 330.34

23 8.66 18.05 8.20 47 187.21 173.64 403.65

Ti lp 6b c c=1.33(kN/m2), '= .851 (kN/m3) 029.25 tra bng c:

28.43cN , qN 16.93, 20.105N

Sc chu ti mi n v theo Vesic:

21.33 28.43 292.496 16.93 9.851 0.4 20.105 5069 kN/mpq

20.4 5069 811.04 kNp p pQ A q

Sc chu ti cc hn ca t nn:

2 2053.4048 811.04 2864.44 kNu s pQ Q Q

Sc chu ti c p p t cng t nn:

2

2053.4048 811.041297.05 kN

2 3

psa

s p

QQQ

FS FS

2.2.2.2.c. Tnh ton sc chu ti ca t theo cng thc ca Nht Bn t kt qu

TN SPT:

Trong :

- h s ph thuc vo phng php thi cng cc, i vi phng php p cc

- aN : ch s SPT ca t di mi cc, aN = 15 ba.

- pA

: din tch tit din mi cc, Ap= 0.16 m2

- sN : gi tr trung bnh ca ch s SPT trong lp t ri, ba.

- baN s 7.13

10

151515161391817109

- sL : chiu di phn cc nm trong lp t ri, m 4.20sL


NHM MNG CC Trang 52

- C : gi tr trung bnh ca s ba lc dnh n v trong lp t dnh,

ba 12.45

121314158

C

- cL : chiu di phn cc nm trong lp t dnh: 9.7m 4.26.36.11.2= cL

- um=4x0.4 (m): chu vi cc.

Sc chu ti cc hn tnh theo cng thc Nht Bn:

3 30 15 0.16 0.2 13.7 20.4 12.4 9.7 4 0.4 353.88 3538.8( )uQ T kN

Sc chu ti tnh theo cng thc Nht Bn:

2.2.2.2.d. Tnh ton sc chu ti ca t theo cng thc ca Meyerhof (1956) t kt

qu TN SPT: (TCXD 205-1998 mc C.2.2)

4 1 2

1( 10 )a p tb s c cQ K NA K N A L CA

FS

Trong :

- K1=400 (cc p).

- N=15 ch s SPT ca t di mi cc

- Ap: din tch tit din mi cc, Ap= 0.16 m2

- K2=2 (cc p).

- Ntb gi tr trung bnh ca ch s SPT trong lp t ri, ba.

9 10 17 18 9 13 16 15 15 1513.7

10tbN ba

- As = Ac =4d=4x0.4=1.6 (m): chu vi cc.

- Lc=9m chiu di phn cc nm trong lp t ri.

- Ls=20.4m chiu di phn cc nm trong lp t ri.

- C : gi tr trung bnh ca s ba lc dnh n v trong lp t dnh,

ba 12.45

121314158

C

Sc chu ti cc hn ca t nn tnh theo cng thc Meyerhof:

4 1 2 10

400 15 0.16 2 13.7 1.6 20.4 10 9 12.4 1.6

3639.93( )

u p tb s s c cQ K NA K N A L L CA

kN


NHM MNG CC Trang 53

Sc chu ti tnh theo cng thc Meyerhof:

4 1 2

1( 10 )

1(400 15 0.16 2 13.7 1.6 20.4 10 9 12.4 1.6)

3

1213.31( )

a p tb s s c cQ K NA K N A L L CAFS

kN

Kt lun : Sc chu ti thit k: 4

1 1806.86 1297.05 1179.6 1213.31 1374.205( )4 4

ai

tb

Q

Q kN

Dng phng php bnh phng cc tiu xc nh gi tr c trng ca t nn ( Ti

trng thit k).

max min4 1806.86 4 1374.205 1179.6 1413.88( )6 6

tbtk

Q Q QQ kN

Sc chu ti cc hn ca t nn:

2 3 4max(Q ;Q ;Q ;Q ) max(2890.97;3036.16;3538.8;3639.93)

3639.93

u tc u u uQ

kN

2.2.2.3. KIM TRA SC CHU TI CA C

Cc chu ti trng tm thi ( khi p cc):

1

max

2 2 1413.88 2827.76( )3957.6( )

3639.93

tk

vl

u

Q kNQ kN

Q kN

=>Tha iu kin chu lc tm thi

Cc chu ti trng lu di ( khi chu ti trng cng trnh):

2 1421.6( )) 1413.88( )vl tkQ kN Q kN

=>Tha iu kin chu lc lu di.

2.2.3. O S B S NG C C:

45201.2 3.83

1413.88

tt

tk

Nn

Q

Chn 4 cc

Trong : h s xt n nh hng ca momen v lc ngang. ( )

2.2.4.B TR C C:

- Khong cch 2 cc: (3 6 ) 1.2 2.4( )s d d m

Chn s=1.7m (khong cch trn cng 1 hng)

- Din tch y i cc : 2m 6.25 =5.25.2 = A

- Khong cc t mp cc bin n mp i: mm 200a


NHM MNG CC Trang 54

- Chiu cao i mng hd=0.8m

- B tr cc nh hnh v:

Hnh 2.3:B tr mng cc

2.2.5. KI RA C

2.2.5.1.KI RA U KIN XUYN TH O

- S cc trong thp xuyn thng: 1xtn cc.

- iu kin chng xuyn thng: cxxt PP

- Chn 0.1 ma , chiu cao lm vic ca tit din: 0 0.8 0.1 0.7 mdh h a

- Lc gy xuyn thng: 2

( ) 2

0.9 4520 0.354520 (4 ) 1811.68kN

1.15 4 0.4xt tt i xtP N P

- Kch thc thp xuyn bmxhm= 2x2(m) (0,6+2x0,7=2 (m) ct c kch thc 0,6x0,6m).

- Thp xuyn c xc nh li nh hnh sau:


NHM MNG CC Trang 55

Hnh 2.9: Thp xuyn thng

=>c=0.55m

- Lc chng xuyn thng: 2

00

0.71 900 5.2 4169.45kN

0.55cx bt m

hP = R u h

c

Trong :

1 : H s iu kin lm vic ca b tng

2900 kN/mbtR : Cng chu ct ca b tng B20

mu

: Chu vi trung bnh ca thp xuyn thng,

0.6 0.6 2 2 5.2( )m c c m mu b h b h m

0.55mc : Xc nh nh hnh v. (Khong hnh chiu t mp ct n tm cc).

0 0.8 0.1 0.7 mh : Chiu cao lm vic ca tit din (gi s thp t st trn u

cc)

Nhn thy: 4169.45 kN 1811.68kNcx xtP = P

Vy i cc tha iu kin xuyn thng.


NHM MNG CC Trang 56

2.2.5.2. KI RA U KIN C O C:(Tnh theo tiu chun

6.2.3.4 TCVN 5574-2012)

- iu kin chng ct (khng c ct ai): 2

4 (1 )b n bt oR bhQc

Trong :

b4=1.5 xt nh hng ca b tng (=1.5 i vi b tng nng)

n h s nh hng ca lc dc:

0.1nbt o

N

R bh

c chiu di hnh chiu ca tit din nghing nguy him nht ln mt mng .

24520 22 2 2.5 4795tt tt tb fN N xD xS x x kN

140 114 0.8 231.2tt tt tty y x dM M H xh x kNm

142 123 0.8 240.4tt tt ttx x y dM M H xh x kNm

max max

max/min 2 2

tttt tt

y x

i i

M xN M yP

n x y

Bng 2.6:Ti trng tc dng ln cc cc

c xi yi xi 2 yi

2 xi

2 yi2 Pi(KN)

1 -0.85 0.85 0.7225 0.7225

2.89 2.89

1201.46

2 0.85 0.85 0.7225 0.7225 1337.46

3 -0.85 -0.85 0.7225 0.7225 1060.04

4 0.85 -0.85 0.7225 0.7225 1196.04

Xt theo phng x :

- Lc ct :

2 4 1337.46 1196.04 2533.5Q P P kN

- Lc chng ct ca b tng :

2

4 (1 )b n bt ob

R bhQ

c

Trong :




NHM MNG CC Trang 57

31140.1 0.1 0.1 7.2 10900 2.5 0.7

xn

bt o bt o

HN

R bh R bh

c chiu di hnh chiu ca tit din nghing nguy him nht ln mt mng theo

phng x.


Lc chng ct ca b tng :

2 3 2

4 (1 ) 1.5 (1 7.2 10 ) 900 2.5 0.7

0.55

3028.46( ) 2533.5( )

b n bt ob

R bh xQ

c

kN Q kN

Bn cnh theo iu kin lm vic ca btng ta xt thm :

3 2

3 0

0

(1 ) 0,6.(1 7,2.10 ).900.2,5x 0,7 665.26( )3028.46( )

2,5 2,5.11500.2,5.0,7 50312.5( )

b n bt

b

b

R bh kNQ kN

R bh kN

Tha iu kin chu ct theo phng x.

Xt theo phng y :

- Lc ct :

1 2 1201.46 1337.46 2538.92( )Q P P kN

- Lc chng ct ca b tng :

2

4 (1 )b n bt ob

R bhQ

c


NHM MNG CC Trang 58

Trong :




31230.1 0.1 0.1 7.8 10900 2.5 0.7

y

n

bt o bt o

HN

R bh R bh

c chiu di hnh chiu ca tit din nghing nguy him nht ln mt mng theo

phng x.

Lc chng ct ca b tng :

2 3 2

4 (1 ) 1.5 (1 7.8 10 ) 900 2.5 0.7

0.55

3030.27( ) 2538.92( )

b n bt ob

R bhQ

c

kN Q kN

Bn cnh theo iu kin lm vic ca btng ta xt thm :

3 2

3 0

0

(1 ) 0,6 x(1 7,8.10 ) x 900 x 2.5x 0,7 666.66( )3030.27( )

2,5 2,5 11500 2,5 0,7 50312.5( )

b n bt

b

b

R bh kNQ kN

R bh x x x kN

Tha iu kin chu ct theo phng y.

2.2.6. KIM TRA SC CHU TI CA C C V NHM C C :

2.2.6.1. Kim tra sc chu ti ca cc n

- Ti trng ln nht tc dng ln cc:

24520 22 2 2.5 4795tt tt tb fN N xD xS x x kN

140 114 0.8 231.2tt tt tty y x dM M H xh x kNm


NHM MNG CC Trang 59

142 123 0.8 240.4tt tt ttx x y dM M H xh x kNm

max max

max/min 2 2

tttt tt

y x

i i

M xN M yP

n x y


c xi yi xi 2 yi

2 xi

2 yi2 Pi(KN)

1 -0.85 0.85 0.7225 0.7225

2.89 2.89

1201.46

2 0.85 0.85 0.7225 0.7225 1337.46

3 -0.85 -0.85 0.7225 0.7225 1060.04

4 0.85 -0.85 0.7225 0.7225 1196.04

Pmax=1337.46 kN0 (Tha)

2.2.6.2. Kim tra sc chu ti ca nhm cc:

- H s nhm:

21

1221

90

)1()1(1

nn

nnnn

Trong : o24.137.1

4.0arctanarctan

s

d

d: ng knh cc, d = 0.4 (m)

s=1.7m: khong cch gia cc ccn1: s hng cc: 31 n

n2: s cc trong mi hng 67.12 n

853.02290

2)12(2)12(24.131

Sc chu ti ca nhm cc:

0.853 4 1413.88 4824.16 kN 4795kNnh tta tkQ n Q N

Kt lun: H cc kh nng chu ti.

2.2.7. P O


c xi yi xi 2 yi

2 xi

2 yi2 Pi(KN)

1 -0.85 0.85 0.7225 0.7225

2.89 2.89

1201.46

2 0.85 0.85 0.7225 0.7225 1337.46

3 -0.85 -0.85 0.7225 0.7225 1060.04

4 0.85 -0.85 0.7225 0.7225 1196.04


NHM MNG CC Trang 60

Hnh 2.4: Mt bng mt ct ngm i mng

- Tnh thp t theo phng X:

2 2 4 4 1337.46 0,55 1196.04 0,55 1393.425i iM Pl P l P l kNm

2 2

0

1393.4250,11 0,441

0,9.11500.2,5.0,7m R

b b

M

R bh

1 1 2. 1 1 2 0,11 0,1167m

3 2 20 0,1167.0,9.11500.2,5.0,7 7.55 10 7550280000

b bs

s

R bhA m mm

R

an ton v gim bt chi ph thi cng chn thp 1625 c 27856 mmsA

Khong cch ct thp : 2500 50 2

15016

a mm

- Tnh thp t theo phng Y:

1 1 2 2 1201.46 0,55 1337.46 0,55 1398.056i iM Pl Pl P l kNm

2 2

0

1398.0560,11 0,441

0,9.11500.2,5.0,7m R

b b

M

R bh

1 1 2. 1 1 2 0,11 0,1167m

3 2 20 0,1167.0,9.11500.2,5.0,7 7.55 10 7550280000

b bs

s

R bhA m mm

R


NHM MNG CC Trang 61

an ton v gim bt chi ph thi cng chn thp 1625 c 27856 mmsA

Khong cch ct thp :2500 50 2

150 mm16

a

Vy chn thp b tr theo phng x: 1625 a150mm

B tr thp tng t theo phng y: 1625 a150mm

2.2.8.KIM TRA NH CA T N D V

LN MNG C C:

. .8.1. Xc n k c t c khi mng quy c:

Hnh 2.5: B tr khi

mng


NHM MNG CC Trang 62

Bng 2.9:Gi tr trung bnh ca gc ni ma st (cn ca TTGH II

p z

(m)

hi

(m) i (

o) ihi

2a 2

1.4 11.05 15.47 3.4

3 3.4

1.6 14.25 22.8 5

4 5

3.6 13.667 49.2012 8.6

5 8.6

2.4 13.283 31.8792 11

6a 11

4 26.45 105.8 15

6b 15

16.4 29.383 481.8812 31.4

ng 29.4 707.0316

c ni ma st t ung b n 24.05

- Tnh ton gc nh hng ca mng khi:

24.056.0125

4 4

ootb

2 tan 2.1 2 tan(6.0125 ) 29.4 8.29 moqu quL B X hi

- Din tch y mng quy c:

28.29 8.29 68.72 mqu qu quA L B x

2.2.8.2. Kim t a iu kin n nh ca t nn di y mng quy c:

- Sc chu ti cc hn t nn di y mng quy c:

'1 2 ( * )II qu II II IItc

m mR A B B h D c

k

Trong :

- m1 =1.2 v m2 = 1.3 (ct mn bo ha nc L/HA =1.098; B =5.3865; D =7.78

- cII= 1.91 (kN/m2): Lc dnh ca t su di y mng quy c ly

theo TTGH II.


NHM MNG CC Trang 63

- II*=9.738 (kN/m

3): trng lng ring trung bnh ca lp t nm trn mi

cc theo TTGH II.

- II=9.869 (kN/m

3): trng lng ring trung bnh ca lp t nm di mi

cc theo TTGH II.

- h: su y mng quy c tnh t y mng.

Bng 2.10: Tnh ton gi tr tb.

z

(m) li (m)

'i (kN/m

3)

i = 'i *li

(kN/m2)

2a 1.3

2.1 9.255 19.436 3.4

3 3.4

1.6 10.04 16.064 5

4 5

3.6 9.762 35.143 8.6

5 8.6

2.4 9.811 23.546 11

6a 11

4 9.27 37.080 15

6b 15

16.4 9.869 161.852 31.4

ng sut hu hiu bn thn t nn ti mi cc 'v

293.121

Trng lng ring trung bnh ca lp t nm trn khi mng quy c

tb 9.738

=>Sc chu ti cc hn ca t nn di y mng khi quy c:

21.2 1.3 (1.098 8.29 9.869 5.3865 29.4 9.738 7.78 1.91) 2569.06 kN/m1.0

IIR

- Lc tc dng ln y mng quy c

y

tc

y

x

tc

x

qu

tc

qu

W

M

W

M

A

Np

max

Trong :

452022 2 68.72 68.72 9.738 29.4 4 0.16 29.4 (25 9.738)

1.

15

26915.63kN

tc tc

qu tb f qu qu i coc coc coc bt tbN N D A A h n A L


NHM MNG CC Trang 64

140 114 0.8219.3

1.15 1.15 1.15 1.15

tt ttytc x d

y

M H xh xM kNm

142 123 0.8209.04

1.15 1.15 1.15 1.15

tttty dtc x

x

H xhM xM kNm

- ng sut ln nht ti y mng quy c :

y

tc

y

x

tc

x

qu

tc

qu

W

M

W

M

A

Np

max

2

max 3 3

2

26915.63 219.3 209.046 6 396.18 kN/m 1.2

68.72 8.29 8.29

1.2 2569.06 3082.87 kN/m

IIp x x R

- ng sut nh nht ti y mng quy c :

y

tc

y

x

tc

x

qu

tc

qu

W

M

W

M

A

Np

min

2

max 3 3

26915.63 219.3 209.046 6 387.16 kN/m 0

68.72 8.29 8.29p x x

- ng sut trung bnh ti y mng quy uc :

2 226915.63 391.67kN/m 2569.06 kN/m68.72

tc

qu

tb II

qu

Np R

A

Kt lun: Vy mng tha iu kin n nh.

2.2.8.3. Kim t a ln ca mng khi quy c:

- Kim tra ln mng khi quy c theo phng php tng phn t qua cc bc:

p lc gy ln:

' '

1 1 1 1 2 1

2

( ( ) )

391.67 1.3 18 (9.255 (2 1.3) 9.738 29.4) 122.26 /

gl tb i i tb a f tb cocp p xl xh p h x D h xL

kN m

Pha di khi mng l lp ct ng nht.Chia thnh tng lp 0,5m.

Bng2.11:Mu c kt 3-11

p sut (kN/m2)

25 50 100 200 400 800

s ng

0.769 0.751 0.725 0.69 0.654 0.61


NHM MNG CC Trang 65

ng cong nn ln do cc p lc


NHM MNG CC Trang 66

591.658 665.748 0.635 0.630 0.17

36.9 -5.5 1.327 0.557 68.10 618.798

648.405 716.504 0.631 0.626 0.14

37.4 -6 1.448 0.509 62.23 678.012

710.086 772.316 0.627 0.623 0.12

37.9 -6.5 1.568 0.462 56.48 742.160

Tng l n 3.96

Tng ln S3.96 (cm) Mng tha yu cu ln.

2.2.9. KIM TRA C C CHU CU LP:

Cc b tr 2 mc cu v dng mc cu trong s cu cc dng cc.

q=K d2=1.5x25x0.4

2=6 (KN/m)

- Khi cu cc:

Hnh 2.7: Ni lc khi b tr 2 mc cu

Moment ln nht : M1=0.0214qL2=0.0214x6x10

2=12.84(KNm)

- Khi dng cc:

Hnh 2.8: Ni lc khi b tr 1 mc cu

0.207L 0.207L

L

M2

0.293L

L

M1

q


NHM MNG CC Trang 67

Moment ln nht :M2=0.068qL2=0.068x6x10

2=40.8(kNm)

- M=max(M1;M2)=M2=40.8 (kNm)

- Tnh thp trong cc:

2 2

0

40.80.08 0.441

0.9 11500 0.4 0.35m R

b b

M

R bh x x x

Tha iu kin s dng ct n

1 1 2 1 1 2 0.08 0.084m x

4 2 20.084 0.9 11500 0.4 0.35 4.34 10 4.34280000

b b os

s

R bh x x x xA x m cm

R

Vy thp chn trong cc l 2 22 mi pha (As =7.6 cm2) l tha mn.

2.2.10.NG D NG SAP2000 KIM TRA CHUYN V NGANG:

M hnh ha t xung quanh cc l mi trng n hi tuyn tnh (m hnh

Winkler) bng phn mm SAP2000V14, vi h s nn p dng tiu chun TCXDVN

205:1998 ca cc lp tng ng nh sau:

Bng 2.13: H s t l tra theo bng G1 TVXD 205-1998

Lp hi (m) IL K (kN/m4) Tn lp

2a 1.4 0.5 5000 St pha ct ln t si sn trng thi do mm

3 1.6 0.23 6620 St ln ct trng thi do cng

4 3.6 0.3 6200 St pha ct trng thi do cng

5 2.4 0.76 2500 Ct pha st trng thi do

6a 4 - 4000 Ct mn trng thi bi ri

6b 16.4 - 6000 Ct mn trng thi cht va

- Chia cc theo phng ng thnh tng on nh, mi on cc c chiu di 0.1

mt, chiu rng 0.4 m. Ta c cc h s K quy i nh sau:

Cz1=z*K1=0.05x(0.1/20.45000) =5 kN/m

Cz2 = Cz3 = Cz4 =.= Cz13 = 0.7x(0.10.45000) = 140kN/m

Cz14 = 1.4x(0.10.45000+0.10.46620)/2 = 325.36 kN/m

Cz15 = Cz16=.= Cz29 = 2.2x(0.10.46620)= 582.56 kN/m

Cz30= 3x(0.10.46620+0.10.46200)/2 = 769.2 kN/m


NHM MNG CC Trang 68

Cz31= Cz32 =.=Cz65= 4.8x(0.10.46200)= 1190.4 kN/m

Cz66= 6.6x(0.10.46200+0.10.42500)/2 =1148.4 kN/m

Cz67= Cz68 =.=Cz89= 7.8x(0.10.42500) =3120 kN/m

Cz90= 9x(0.10.42500+0.10.44000)/2 = 1170 kN/m

Cz91= Cz92 =.= Cz129= 11x(0.10.44000 )= 1760 kN/m

Cz130= 13x(0.10.44000+0.10.46000)/2 = 2600kN/m

Cz131= Cz132 =.=Cz293= 21.2x(0.10.46000) = 5088 kN/m

Cz294= 29.4x(0.1/20.46000) = 3528kN/m

cng quy v l xo gn di mi cc:

122.26 68.72265205.404( / )

0.2 4 0.2 0.0396

gl qu

m

lun

p AC kN m

n S

Vt liu:

B tng B30c Rb=17Mpa=17000kN/m2; B20c Rb=11.5Mpa=11500kN/m

2

Thp AII c Rs=280Mpa= 280000kN/m2.


NHM MNG CC Trang 69

. .1 .1. n t p ng x

Bng 2.14: Tng hp ni lc cc the phng x (m hnh 3D)

M hnh t ti ngang Kt qu m men Kt qu lc ct Kt qu

chuyn v

Trn cc c ni lc ln nht

(2D)


NHM MNG CC Trang 70

T kt qu xut ra t SAP2000, ta c cc gi tr m men, lc ct v chuyn v ngang nh

sau:

maxmax

`

max

33.72kNm

28.51 kN

U 0.005 m 5 m

m

zx

x

x

t a i n

Q

gmM

* Kim tra cc chu momen:

max

2 2

33.720.0505 0.432

0.9 14500 0.4 (0.4 0.05)

1 1 2 1 1 2 0.0505 0.05184

1 0.5 1 0.5 0.05184 0.9741

zm R

b o

m

M

R b h

Din tch thp yu cu:

max

4 2 2 2

33.72

0.9741 280000 (0.4 0.05)

3.53 10 m 353 mm =760 mm (2 22)

yc zs

s o

s

MA

R h

A

Vy ct thp trong cc m b iu kin chu lc momen un do ti ngang.

* Kim tra cc chu ct:

max 28.51 kNxQ

Kim tra iu kin tnh ct ai :

0 max0 6 0 6 1050 0.4 0.4 0 05 88.2 kN 28.51 kNbt. R b h = . . = > Q =

Vy cc tha iu kin chu ct.

* Kim tra chuyn v u cc

Chuyn v u cc l Umax = 5 mm < 1%Lcc = 29.4 mm.

Vy tha iu kin bin dng.


NHM MNG CC Trang 71

. .1 . . n t p ng y

Bng 2.15: Tng hp ni lc cc the phng y

M hnh t ti ngang Kt qu m men Kt qu lc ct Kt qu

chuyn v

Trn cc c ni lc ln nht

(2D)


NHM MNG CC Trang 72

T kt qu xut ra t SAP2000, ta c cc gi tr m men, lc ct v chuyn v ngang nh

sau:

maxmax

m

`

ax

36.84kNm

30.76 kN

U 0.0053 m 5 3

. mm

zx

x

x

t a i ngmM

Q

* Kim tra cc chu momen:

max

2 2

36.840.0465 0.432

0.9 17000 0.4 (0.4 0.05)

1 1 2 1 1 2 0.0465 0.0476

1 0.5 1 0.5 0.0476 0.976

zm R

b o

m

M

R b h

- Din tch thp yu cu:

max

4 2 2 2

36.84

0.9760 280000 (0.4 0.05)

3.85 10 m 385 mm =760 mm (2 22)

yc zs

s o

s

MA

R h

A

Vy ct thp trong cc m b iu kin chu lc momen un do ti ngang.

* Kim tra cc chu ct:

max 30.76kNyQ

Kim tra iu kin tnh ct ai :

0 max0 6 0 6 1200 0.4 0.4 0 05 100.8 kN 30.76kNbt. R b h = . . = > Q =

Vy cc tha iu kin chu ct.

* Kim tra chuyn v u cc

Chuyn v u cc l Umax = 5.3mm < 1%Lcc = 29.4 mm.

Vy tha iu kin bin dng.


NHM MNG CC Trang 73

2.2.11. KIM TRA C C CHU TI NGANG (theo ph l c G TCXD 205

1998):

Momen ti chn i chuyn thnh lc dc trong ct, nn cc khng c momen tc

dng.Ch c lc ngang tc dng u cc (tng ng y i).

- Momen qun tnh tit din ngang ca cc:

- Mun n hi ca b tng B30:

- Chiu rng quy c cc:

V nn theo TCXD 205:1998

- H s nn:

Trong K h s t l (kN/

Khi tnh ton cc chu ti trng ngang, thc cht cc ch lm vic vi mt on

cc c chiu di tnh t y i cn gi l chiu su nh hng ca nn t khi

cc chu ti trng ngang

Chiu su nh hng c xc nh t cng thc thc nghim


NHM MNG CC Trang 74

Hnh 2.9: su nh hng ca cc

Bng tra K

Lp hi (m) IL K (kN/m4) Tn lp

2a 1.4 0.5 5000 St pha ct ln t si sn trng thi do mm

3 1.6 0.23 6620 St ln ct trng thi do cng

4 3.6 0.3 6200 St pha ct trng thi do cng

5 2.4 0.76 2500 Ct pha st trng thi do

6a 4 - 4000 Ct mn trng thi bi ri

6b 16.4 - 6000 Ct mn trng thi cht va

4

5000 1.4 6620 1.6 6200 3.6 2500 2.4 4000 4 6000 16.4

29.4

5453( / )

i i

i

k l x x x x x xK

l

kN m

=>H s bin dng:

- Chiu di cc trong t tnh i:


NHM MNG CC Trang 75

- Tra bng G2 ph lc G ca TCXD 205:1998 phn cc ta ln t vi

ta c cc h s nh sau:

- Chuyn v ngang ca tit din cc bi lc n v gy ra:

- Chuyn v ngang ca tit din cc bi lc n v gy ra:

- Gc xoay ca tit din cc bi lc n v gy ra:


NHM MNG CC Trang 76

- Lc ct v momen un ti u cc:

- Chuyn v ngang v gc xoay ca cc ti cao trnh mt t:

- Tnh ton chuyn v ngang v gc xoay ca u cc theo cng thc:

chiu di cc t y i n mt t, cc i thp

Kim tra chuyn v ngang ti u cc:

Nh vy cc tha iu kin v chuyn v ngang

Kim tra chuyn v xoay ti u cc:

Cc gi tr chuyn v ca u cc theo c hai phng u gn bng 0, iu ny

ni rng vic tnh ton lm ng.


NHM MNG CC Trang 77

2.2.12. TNH TON NI LC TRONG C C (theo TCXD 205 1998):

p lc (kN/ ), moment un (kNm), lc ct (kN) trong cc tit din cc c

tnh theo cng thc sau (trch t mc G7 ph lc G ca TCXD 205:1998):

(

)

Trong : ( Xt theo phng chu lc ln hn: phng y trong h chn)

, ,

, - chiu su tnh i, , vi

Cc h s A1, A3, A4, B1, B3, B4, D1, D3, D4 tra bng G3 ph lc G TCXD 205:1998


NHM MNG CC Trang 78

Bng 2.16: Momen dc thn cc

Z s vi y i cc,m )

Ze su quy i t a bng,m )

A3 B3 C3 D3 Mz

(kNm)

0 0 0 0 1 0 -36.84

-0.2 0.1 0 0 1 0.1 -31.82

-0.3 0.2 -0.001 0 1 0.2 -26.86

-0.5 0.3 -0.004 -0.001 1 0.3 -22.00

-0.6 0.4 -0.011 -0.002 1 0.4 -17.37

-0.8 0.5 -0.021 -0.005 0.999 0.5 -12.83

-1.0 0.6 -0.036 -0.011 0.998 0.6 -8.53

-1.1 0.7 -0.057 -0.02 0.996 0.699 -4.54

-1.3 0.8 -0.085 -0.034 0.992 0.799 -0.74

-1.4 0.9 -0.121 -0.055 0.985 0.897 2.72

-1.6 1 -0.167 -0.083 0.975 0.994 5.79

-1.7 1.1 -0.222 -0.122 0.96 1.09 8.66

-1.9 1.2 -0.287 -0.173 0.938 1.183 11.25

-2.1 1.3 -0.365 -0.238 0.907 1.273 13.51

-2.2 1.4 -0.455 -0.319 0.866 1.358 15.45

-2.4 1.5 -0.559 -0.42 0.781 1.437 18.23

-2.5 1.6 -0.676 -0.543 0.739 1.507 18.59

-2.7 1.7 -0.808 -0.691 0.646 1.566 19.81

-2.9 1.8 -0.956 -0.867 0.53 1.612 20.75

-3.0 1.9 -1.118 -1.074 0.385 1.64 21.55

-3.2 2 -1.295 -1.314 0.207 1.646 22.13

-3.5 2.2 -1.693 -1.906 -0.271 1.575 22.86

-3.8 2.4 -2.141 -2.663 -0.941 1.352 22.77

-4.1 2.6 -2.621 -3.6 -1.877 0.917 22.82

-4.4 2.8 -3.103 -4.718 -3.408 0.197 33.19

-4.8 3 -3.541 -6 -4.688 -0.891 20.89

-5.5 3.5 -3.919 -9.544 -10.34 -5.854 13.70

-6.3 4 -1.614 -11.73 -17.919 -15.08 -5.78

Hnh 2.10: Biu momen dc thn cc

-7

-6

-5

-4

-3

-2

-1

0

-60.00 -40.00 -20.00 0.00 20.00 40.00

m n dc t n cc z k m)


NHM MNG CC Trang 79

Bng 2.17: Lc c t dc thn cc

Z s vi y i cc,m )

Z su quy i t a bng,m )

A4 B4 C4 D4 Qz(kN)

0.0 0 0 0 0 1 30.8

-0.2 0.1 -0.005 0 0 1 30.6

-0.3 0.2 -0.02 -0.003 0 1 30.1

-0.5 0.3 -0.045 -0.009 -0.001 1 29.3

-0.6 0.4 -0.08 -0.021 -0.003 1 28.2

-0.8 0.5 -0.125 -0.042 -0.008 0.999 27.0

-1.0 0.6 -0.18 -0.072 -0.016 0.997 25.5

-1.1 0.7 -0.245 -0.114 -0.03 0.994 23.8

-1.3 0.8 -0.32 -0.171 -0.051 0.989 22.1

-1.4 0.9 -0.404 -0.243 -0.082 0.98 20.3

-1.6 1 -0.499 -0.333 -0.125 0.967 18.4

-1.7 1.1 -0.603 -0.443 -0.183 0.946 16.5

-1.9 1.2 -0.716 -0.575 -0.259 0.917 14.7

-2.1 1.3 -0.838 -0.73 -0.356 0.876 12.9

-2.2 1.4 -0.967 -0.91 -0.479 0.821 11.2

-2.4 1.5 -1.105 -1.116 -0.63 0.747 9.5

-2.5 1.6 -1.248 -1.35 -0.815 0.652 8.0

-2.7 1.7 -1.396 -1.613 -1.036 0.529 6.6

-2.9 1.8 -1.547 -1.906 -1.299 0.374 5.4

-3.0 1.9 -1.699 -2.227 -1.608 0.181 4.2

-3.2 2 -1.848 -2.578 -1.966 -0.057 3.1

-3.5 2.2 -2.125 -3.36 -2.849 -0.692 1.4

-3.8 2.4 -2.339 -4.228 -3.973 -1.592 -0.1

-4.1 2.6 -2.437 -5.14 -5.355 -2.821 -1.4

Hnh 2.11: Biu lc c t dc thn cc

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

-5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

c ct Qz k )


NHM MNG CC Trang 80

Bng 2.18: Gi tr p lc ngang

Z su s vi y i,m)

Z su quy i t a bng,m)

A1 B1 C1 D1 k z

(kPa)

0.0 0 1 0 0 0 5000 0.00

-0.2 0.1 1 0.1 0.005 0 5000 1.86

-0.3 0.2 1 0.2 0.02 0.001 5000 3.58

-0.5 0.3 1 0.3 0.045 0.004 5000 5.13

-0.6 0.4 1 0.4 0.08 0.011 5000 6.50

-0.8 0.5 1 0.5 0.125 0.021 5000 7.67

-1.0 0.6 0.999 0.6 0.18 0.036 5000 8.62

-1.1 0.7 0.999 0.7 0.245 0.057 5000 9.36

-1.3 0.8 0.997 0.799 0.32 0.085 5000 9.89

-1.4 0.9 0.995 0.899 0.405 0.121 5000 10.21

-1.6 1 0.992 0.997 0.499 0.167 6620 13.74

-1.7 1.1 0.987 1.095 0.604 0.222 6620 13.68

-1.9 1.2 0.979 1.192 0.718 0.288 6620 13.39

-2.1 1.3 0.969 1.287 0.841 0.365 6620 12.93

-2.2 1.4 0.955 1.379 0.974 0.456 6620 12.32

-2.4 1.5 0.937 1.468 1.115 0.56 6620 11.60

-2.5 1.6 0.913 1.553 1.264 0.678 6620 10.76

-2.7 1.7 0.882 1.633 1.421 0.812 6620 9.86

-2.9 1.8 0.843 1.706 1.584 0.961 6620 8.94

-3.0 1.9 0.795 1.77 1.752 1.126 6620 8.05

-3.2 2 0.735 1.823 1.942 1.308 6200 6.19

-3.5 2.2 0.575 1.887 2.272 1.72 6200 5.40

-3.8 2.4 0.347 1.874 2.609 2.195 6200 4.61

-4.1 2.6 0.033 1.755 2.907 2.724 6200 4.62

-4.4 2.8 -0.385 1.49 3.128 3.288 6200 5.72

-4.8 3 -0.928 1.037 3.225 3.858 6200 7.84

-5.5 3.5 -2.928 -1.272 2.463 4.98 6200 19.63

-6.3 4 -5.854 -5.941 -0.927 4.548 6200 39.63


NHM MNG CC Trang 81

Hnh 2.12: Biu p lc ngang

D = 0.4 m < 0.6 m nn khng cn kim tra iu kin n nh t nn quanh cc

-7.0

-6.0

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

0.00 10.00 20.00 30.00 40.00 50.00

p lc ngang (kPa)

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