p2-Chuong 2 Dam Thep Lien Hop Btct

10.NEOCHNGCT10.1GIITHIU

THIE TKE CA UTHE PTS.NGUYENCA NHTUA N

165/333



166/333

pht trin cng chu un ton phn ca mt cu kin lin hp, lc ctnm ngang phi c tip nhn mt tip xc gia dm thp v bn b tng.

chu lc ct nm ngang ti mt tip xc, cc neo c hn vo bn bintrn ca dm thp v s c lin khi vi bn b tng.

Cc neo chng ct ny c nhng dng khc nhau. ng knh ln hn ca u inh tn trong neo chng ct cho php n chngli lc nh cng nh s trt ngang.

Khng cn phi tnh ton kim tra sc khng nh. Cc nghin cu thc nghim cho thy, cc trng hp ph hoi xy ra c linquan n ct inh neo hoc ph hoi b tng.

Cc inh u hn khng b ko ra khi b tng v c th c coi l khnng chng trt.



167/333



168/333



169/333



170/333



171/333

S liu t cc th nghim c s dng xy dng cc cng thc thcnghim xc nh sc khng ca inh neo u hn.

Cc th nghim cho thy rng, pht trin hon ton sc chu ca inh neo,chiu di ca inh t nht phi bng bn ln ng knh thn ca n.

Do vy, iu kin ny tr thnh mt yu cu trong thit k. Hai TTGH phi c xem xt khi xc nh sc khng ca neo chng ct l miv cng .

TTGH mi c kim tra mc ng sut trong phm vi n hi. TTGH cng ph thuc vo ng x do v s phn phi li lc ct nmngang gia cc neo.



172/333

Cc th nghim c tin hnh bi Slutter v Fisher (1967) cho thy rng: Bin ng sut ct l nhn t quyt nh i vi s lm vic mi ca neo

chng ct.

Cng b tng, tui b tng, hng ca neo, hiu ng kch thc v ngsut nh nht khng c nh hng ln n cng mi.

T , cng mi ca neo chng ct c th c xc nh bi quan h giabin ng sut ct cho php Sr v s chu k ti trng gy mi.

10.NEOCHNGCT10.2TTGHMICHONEOCHNGCT


173/333

Biu theo hm logarit ca cc s liu SN cho hai loi inh 19mm v 22mmc th hin trn hnh v.



174/333

ng sut ct c tnh ton l ng sut trung bnh trn ng knh danh nhca inh neo.

ng cong miu t quan h trn thu c t phn tch kt qu thc nghimc cho bi

trong , Sr l bin ng sut ct (MPa) v N l s chu k ti trng.



0,191065rS N

175/333

Trong tiu chun thit k cu AASHTO LRFD, bin ng sut ct Sr (MPa) trthnh mt lc ct cho php Zr (N) i vi mt chu k ti trng c trng bng

cch nhn Sr vi din tch mt ct ngang ca inh neo, ngha l

vi d l ng knh danh nh ca inh neo (mm).

Tiu chun thit k cu AASHTO LRFD biu din cng thc (1) di dng

trong



2 0,19 28364r r

Z d S N d

2 219,0rZ d d

238 29,5logN

(1)

(2)

(3)

176/333

Cc gi tr ca c so snh trong bng bn di vi cc gi tr tnh t phnbiu thc trong ngoc ca cng thc (1) theo cc gi tr th nghim ca N.

Biu thc i vi trong cng thc (3) l kh gn vi cc kt qu thcnghim.

Ch : hng s trong v phi ca cng thc (2) l bng gi tr 38.0 MPa trongbng 5.1 ti N = 6106 chia cho hai.



N 23829,5logN 836N0,19

2 104

1 105

5 105

2 106

6 106

111.0MPa

90.5MPa

69.9MPa

52.1MPa

38.0MPa

127.0MPa

93.8MPa

69.1MPa

53.1MPa

43.1MPa

177/333

Cc cng thc (2) v (3) c th c s dng xc nh sc khng ct mica mt inh n c ng knh d i vi mt s chu k lp c trng N.

Khong cch gia cc neo ny dc theo chiu di cu ph thuc vo s lngneo trn mt mt ct ngang n v ln ca lc ct Vsr (N) do xe ti thit k mi

tc dng ti mt ct.



178/333

Do mi l quyt nh khi chu ti trng lp nn tiu chun thit k c datrn cc trng thi n hi.

Gi thit c tng tc hon ho, lc ct nm ngang trn mt n v chiu dih (N/mm) c th tnh ton t quan h n hi

trong ,

Q (mm3) l m men (tnh) ban u ca din tch bn tnh i i vi trc trung

ho ca mt ct lin hp ngn hn

I (mm4) l m men qun tnh ca mt ct lin hp ngn hn.



srh

V QI

179/333

Lc ct trn mt n v chiu di c chu bi n neo ti mt mt ct ngangvi khong cch p (mm) gia cc hng:

Khong cch p (mm) c xc nh khi ng nht v phi cc cng thc ca h

n = s lng cc neo chng ct trong mt mt ct ngang

I = mmen qun tnh ca mt ct lin hp ngn hn (mm4)

Q = mmen th nht ca din tch quy i i vi trc trung ha ca mt ct lin hp thi ngn hn

(mm3)

Vsr = phm vi lc ct di LL+ IM xc nh cho trng thi gii hn mi

Zr = sc khng mi chu ct ca mt neo chng ct ring l theo quy nh trong iu 6.10.7.4.2 (N).



rh

nZp

r

sr

nZ IpV Q

(6.10.7.4.1B1)

180/333

Khong cch dc t tim n tim ca cc neo chng ct cn khng ln hn600mm v khng nh hn 6 ln ng knh thn inh.

Cc inh neo chng ct cn c b tr vi khong cch tim n tim theophng vung gc vi trc dc ca cu kin khng nh hn bn ln ng

knh inh.

Khong cch trng gia mp ca bn bin trn ca dm thp v mp ca neochng ct gn nht phi khng c nh hn 25mm.

Chiu dy phn b tng ph bn trn nh neo cn khng nh hn 50mm. Trong nhng vng m khong cch gia nh dm thp v y bn b tng lln th cc neo cn c chn vo trong bn ti thiu 50mm.



181/333

Cc nghin cu thc nghim c tin hnh bi Ollgaard v cng s xcnh cng chu ct ca cc inh neo chng ct c chn trong mt bn b

tng c.

Cc i lng thay i c xem xt trong th nghim l ng knh inh, sinh neo trong mt bn, loi ct liu ca b tng (t trng nh hay t trng thng

thng) v cc thuc tnh ca b tng.

Bn thuc tnh ca b tng c nghin cu: cng chu nn, cng chu ko ch khi tr, m un n hi v t trng.

10.NEOCHNGCT10.3TTGHCNGCHONEOCHNGCT


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C hai dng ph hoi c nhn thy. Hoc l cc inh neo b ct ri khi dm thp v vn c chn trong bn b

tng

Hoc l b tng b ph hoi v cc inh neo b nh khi bn cng vi mtphn b tng.

i khi, c hai dng ph hoi thu c trong cng mt th nghim. Vic phn tch cc kt qu th nghim cho thy rng, sc khng ct danh nh

ca mt neo chng ct Qn l t l thun vi din tch mt ct ngang ca chng

Asc.

ng thi, trong cc bin ca b tng, cng chu nn fc v m un nhi Ec l nhng thuc tnh quyt nh trong xc nh cng chu ct ca

neo.



183/333

Biu thc thc nghim xc nh m un n hi bao hm t trng ca b tngc v, do , nh hng ca loi ct liu (thng thng hay nh), ngha l

vi c l t trng ca b tng (kg/m3) v fc l cng chu nn ca b tng

(MPa).

Vic a vo cng chu ko ca khi tr trong phn tch hi quy khngchng t s ph hp vi cc kt qu th nghim v n c loi b khi cng

thc d on cui cng.



1,5 '0.043c c cE f

184/333

Cui cng, cng thc d on sc khng ct danh nh Qn (N) ca mt inhneo chng ct c chn trong mt bn b tng c

trong

Gii hn trn i vi cng chu ct danh nh ca neo c ly l lc kogii hn ca n.



'0.5n sc c c sc uQ A f E A F

Asc din tch mt ct ngang ca inh neo(mm2),

fc cng chu nn quy nh ca b tng tui 28 ngy (MPa),

Ec m un n hi (MPa),v

Fu cng chu ko nh nht c trng ca mt neochng ct

185/333



r sc nQ Q

Cng thc Qn khi so snh vi cc s liu th nghim cho kt qu kh ph hp. Sc khng c h s ca mt neo chng ct Qr l

vi sc l h s sc khngi

vi neo chng ct, sc = 0.85

186/333

Nu cc neo chng ct c b tr y th cng chu un ln nht camt mt ct lin hp c th c pht trin.

Cc neo chng ct c b tr gia mt im c m men bng khng v imc m men dng ln nht phi chu c lc nn trong bn ti v tr c m men

ln nht.

Sc khng ny c miu t bng cc s cn bng lc cho hai trng hpti trng khc nhau.



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188/333

T cc s ny, iu kin cn bng

hoc

trong



s r hnQ V

hsr

VnQ

ns tng s neochng ct gia im c mmen bng khng v im c mmendng ln nht

Vh lc ct nm ngang danh nh ti mt tip xc m neo phi chu, v

Qr Sc cho ng ca t tnh toan cua inh neo(kN)

Fu sc khng ct c h s ca mt neochng ct

189/333

Khong cch ca cc neo chng ct

Khong cch gia cc neo chng ct dc theo chiu di Ls cn c kim tra. Trong trng hp ti trng tp trung, lc ct thng ng l khng i. do vy, lc ct nm ngang trn mt n v chiu di c tnh t quan h nhi l hng s v khong cch neo s l bng nhau.

Trong trng hp ti trng phn b u, lc ct nm ngang n hi thay itrn mt n v chiu di; do vy, cc neo gn gi cn c b tr gn nhau

hn so vi vng gia nhp.

l nhng ch dn c d on bi l thuyt n hi. TTGH Cng , tnh hnh s khc i nu ng x do cho php phn phi

li lc ct nm ngang.



190/333

TTGH cng khi un ca mt ct lin hp, c th c hai trng thi phnb ng sut nh trong hnh.

Phn vut gia y bn b tng v nh dm thp, vng m neo chng cttruyn lc ct nm ngang t bn b tng sang mt ct thp.



191/333

Trong trng hp th nht, trc trung ho do nm trong bn v lc nn Cnh hn cng ton phn ca bn.

Tuy nhin, s cn bng lc i hi C bng lc ko trong mt ct thp, ngha l

trong

i vi mt ct thp ng nht (trong ti liu ny) cng thc trn n gin l

vi Fy l cng chy (MPa) v As l din tch ton b mt ct thp (mm2).



h yw yt t t yc c cC V F Dt F bt F b t w

Vh lc ct nm ngang danh nhFyw,Fyt,Fyc cng chy ca bn bng, bn bin ko v bn bin nnDvtw chiu cao v chiu dy ca bn bngbt v tt chiu rng v chiu dy ca bn bin ko,vbcvtc chiu rng v chiu dy ca bn bin ko.

h y sC V F A

192/333

Trong trng hp th hai, trc trung ho do nm trong mt ct thp v lcnn C = Vh l cng ton phn ca bn c cho bi

vi

fc : cng chu nn 28 ngy ca b tng (MPa)

Bhh : chiu rng hu hiu ca bn (mm)

ts : chiu dy ca bn (mm)



'0.85h c hh sV f B t

193/333

Mt ct lin hp lin tc

Mt ct lin hp trong vng chu m men m ca dm lin tc, lc ct nmngang danh nh Vh c truyn gia im khng m men v im c m

men ln nht ti mt gi trung gian s l

trong

Ar : din tch ton b ca ct thp dc

(mm2) bn trn gi trung gian trong

phm vi chiu rng bn hu hiu

Fyr : cng chy (MPa) ca ct thp dc



h rV A F yr hsr

VnQ

194/333

Trong cc mt ct lin hp, phi lm cc neo ch U hoc neo inh chng ct mt tip xc gia bn mt cu b tng v mt ct thp chu lc ct mt

tip xc.

Cc cu kin lin hp nhp gin n phi lm cc neo chng ct sut chiu dica nhp.

Cc cu lin hp lin tc thng nn lm cc neo chng ct sut chiu di cu.Trong cc vng un m phi lm cc neo chng ct ni m ct thp dc

c xem l mt phn ca mt ct lin hp. Mt khc, cc neo chng ct

khng cn phi lm trong cc vng un m, nhng phi t cc neo b sung

trong vng ca cc im un tnh ti theo quy nh trong iu 6.10.7.4.3.

Ni m cc neo chng ct c s dng trong cc vng un m, ct thp dcphi c ko di vo vng un dng theo quy nh trong iu 6.10.1.2.

10.NEOCHNGCT10.4YUCUCHONEOCHNGCT(6.10.7.4)


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Cc neo ch U v neo inh chng ct phi c thit k theo cc quy nh caiu ny.

Cc neo chng ct cn thuc mt kiu m kiu cho php khi m k btng th bo m ton b cc b mt ca chng c tip xc vi b tng. Cc

neo phi c kh nng chng li c hai chuyn v thng ng v nm ngang

gia b tng v thp.

T l ca chiu cao vi ng knh ca neo inh chu ct khng cnh hn 4.0.

Cc neo ch U chng ct phi c cc ng hn khng nh hn 5mm t dctheo chn v gt ca thp U.



196/333

TTGHMi Bc neo (6.10.7.4.1b)

Bc ca cc neo chng ct phi c xc nh tha mn trng thi giihn mi theo quy nh trong iu 6.10.7.4.2 v 6.10.7.4.3 khi c th p dng

c.

S lng tnh ra ca cc neo chng ct khng c nh hn s lng yu cu tha mn trng thi gii hn cng nh quy nh trong iu 6.10.7.4.4.

Bc t tim n tim ca cc neo chng ct khng c vt qu 600 mm vkhng c nh hn 6 ln ng knh inh.



197/333

TTGHMi Bc neo (6.10.7.4.1b)

Bc ca cc neo chng ct khng c ln hn:

trong :

n = s lng cc neo chng ct trong mt mt ct ngang

I = mmen qun tnh ca mt ct lin hp ngn hn (mm4)

Q = mmen th nht ca din tch quy i i vi trc trung ha ca mt ct

lin hp ngn hn (mm3)

Vsr = phm vi lc ct di LL+ IM, xc nh cho trng thi gii hn mi

Zr = sc khng mi chu ct ca mt neo chng ct ring l theo quy nh trong

iu 6.10.7.4.2 (N).



r

sr

nZ IpV Q

198/333

TTGHMi Sc khng mi ca cc neo chng ct trong cc mt ct lin hp

Sc khng mi ca neo chng ct ring l, Z, phi c ly nh sau:

trong :

ds = ng knh neo inh (mm)

N = s chu k qui nh trong iu 6.6.1.2.5

nhhngcaneochngctlnsckhngmicabncnhphicnghincubngsdngcc quynhcaiu6.6.1.2.



22 38

2s

r s

dZ d (6.10.7.4.2)238 29.5log N

199/333

Trng thi gii hn cng (6.10.7.4.4)

Sc khng ct danh nh ca mt neo inh chu ct c bc trong bn btng phi c ly nh sau:

trong :



'0.5n sc c c sc uQ A f E A F

Asc din tch mt ct ngang ca inh neo(mm2),

fc cng chu nn quy nh ca b tng tui 28 ngy (MPa),

Ec m un n hi (MPa),v

Fu cng chu ko nh nht c trng ca mt neochng ct

200/333

Trng thi gii hn cng (6.10.7.4.4a)

Sc khng mi ca neo chng ct ring l, Z, phi c ly nh sau:

trong :

Qn = sc khng danh nh theo iu 6.10.7.44c

sc = h s sc khng ca neo chng ct theo iu 6.5.4.2

S lng neo chng ct b tr gia mt ct mmen dng ln nht v miim k mmen 0,0 , hoc gia mi im k mmen 0,0 v tim ca tr

pha trong khng c nh hn:



r sc nQ Q

h

r

VnQ

201/333

Trng thi gii hn cng (6.10.7.4.4b)

Tng lc ct nm ngang, Vh gia im mmen dng ln nht v mi imk ca mmen 0,0 phi:

i vi cc mt ct lin hp nhp lin tc, tng lc ct nm ngang gia miim k ca mmen 0,0 v tim ca gi pha trong phi ly nh sau:



'0.85min h c hh sh

h yw yt t t yc c c

V f B tV

V F Dt F bt F b t w

h rV A F yr

202/333

Khong cch ngang (6.10.7.4.1c)

Cc neo chng ct phi c t theo phng ngang qua bn cnh trn catit din thp v c th t cch khong theo cc c ly u hoc thay i.

Cc neo inh chng ct khng c t gn hn 4 ln ng knh t timn tim theo phng ngang n trc dc ca cu kin ta.

Khong cch tnh gia mp ca bn cnh trn v mp ca neo chng ctgn nht khng c nh hn 25 mm.

Lp ph v chn su (6.10.7.4.1d)

Chiu cao tnh ca lp b tng ph trn cc nh ca cc neo chng ctkhng c nh hn 50 mm.

Cc neo chng ct cn c chn su t nht 50 mm vo trong mt cu.



203/333


THIE TKE CA UTHE PTS.NGUYNCA NHTUA N

204/333

THIE TKE CA UTHE PTS.NGUYENCA NHTUA NV D 7:

Thit k neochng ct cho tit din chu momen dng.

S chu k ti trng lp trong tui th thit k N=372 106

Lc ct Vsr doti trng mi c cho trong bng

S dng inh neoD20

(ds =20mm),hs =100mm,Fu =400(Mpa)

Thep damcoFy =345(Mpa)

B tng ban mat caucofc =28(Mpa)

Chiu di nhp tnh ton L=24m

205/333


V tr Lc ct tiu chunV+(kN)Lc ct tiu chun

V (kN)Lc ct tnh ton

Vsr (kN)

Gi 265 0 198.8

L/8 236 24 195.0

L/6 207 46 189.8

L/4 179 70 186.8

L/2 121 121 181.5

Vng lc ct doti trng gy mi

206/333


1. Kim tra kch thc neo

Chiu cao phn inh neo nm trong bn b tng:

Khong cch t nh neo inh n mp trn bn b tng:

Kim tra t l kch thc ca inh neo:

100 25 75 50neo s hh h d mm mm

100 5.0 420s

hd

(OK)

(OK)

200 25 100 125 50c s h sd t d d mm mm (OK)

207/333


2. TTGHMi

Khong cch neo inh theo phng ngang:

Khong cch t mp ngoi cnh n tim neo inh:120 4 80neo sL mm d mm (OK)

30 25md mm mm (OK)

208/333


2. TTGHMi

Khong cch neo inh theo phng dc:

Tnh ton khong cch neo thit k:

Momen qun tnh ca mt ct lin hp ngn hn:

Momen tnh ca din tch bn mt cu qui i i vi TTH ca mt ct linhp ngn hn:

6 120 600sd mm p mm

r

sr

nZ IpV Q

10 43.13096 10I mm

3124194012

hh s st h

B t tQ y t mmn

209/333


2. TTGHMi

Sc khng mi ca 01 neo inh:

22 385900 7600

2s

r s

dZ d N N

6238 29.5lg 238 29.5lg 372 1014.8

NMpa

=

7600rZ N

210/333


2. TTGHMi

Lc ct tnh ton cho TTGH Mi

Khong cch thit k ca neo inhPhnon Vsr (kN) nneo Ix (mm

4) Q(mm3) Zr (kN)ptt

(mm)ptk

(mm)Kimtra

Gi ~L/8 198.8 3 3.130961010 12419401 7.6 289 200 OK

L/8~L/6 195.0 3 3.130961010 12419401 7.6 295 250 OK

L/6~L/4 189.8 3 3.130961010 12419401 7.6 303 300 OK

L/4~L/2 186.8 3 3.130961010 12419401 7.6 308 300 OK

V tr Lc ct tiu chunV+(kN)Lc ct tiu chun

V (kN)Lc ct tnh ton

Vsr (kN)Gi 265 0 198.8L/8 236 24 195.0L/6 207 46 189.8L/4 179 70 186.8L/2 121 121 181.5

211/333


2. TTGH Cng

S lng neo inh trn 1/2 nhp tnh ton:

Phn on C ly nneo(ngang)ptk

(mm)nneo(dc)

Tng sneo

Gi ~L/8 3000 3 200 45

138L/8~L/6 1000 3 250 12

L/6~L/4 2000 3 300 21

L/4~L/2 6000 3 300 60

212/333


2. TTGH Cng

Sc khng ct danh nh ca 01 neo inh:

Sc khng ct tnh ton ca 01 neo inh:

Lc ct nm ngang danh nh

S lng neo cn b tr chu lc ct trn 1/2 nhp TTGH Cng

2'0.5 0.5 28 27593 138100

4s

n sc c c

dQ A f E N 138.1 141.4n sc uQ kN A F kN (OK)

0.85 138.1 117.4r sc nQ Q kN '0.85 10520

min7375

h c hh sh

h yw yt t t yc c c

V f B t kNV

V F Dt F bt F b t kN w

7375hV kN

7570 63 138117.4

h

r

VnQ

neo neo (OK)213/333

11.SNTNGCNG11.1GIITHIU


214/333



215/333



216/333



217/333



Bn bng ca cc mt ct thp cn nh hnh c kch thc m bo chochng c th t ti ng sut chy khi chu un v khi chu ct m khng b

mt n nh.

iu ny khng xy ra vi nhiu mt ct ch I t hp v ngn nga mt nnh, cc bn bng ca dm phi c tng cng.

C sn tng cng ng v sn tng cng dc u c th c s dng nng cao cng ca bn bng.

Cc sn tng cng ng lm tng sc khng ct trong khi cc sntng cng dc lm tng sc khng mt n nh do un.

218/333

11.SNTNGCNG11.2SNTNGCNGNGTRUNGGIAN


Cc sn tng cng ng khng ngn nga mt n nh ct ca cc khoangphn bn bng nhng chng to ra cc bin ca khoang phn bn bng m

trong mt n nh xy ra.

Cc sn tng cng ny c vai tr nh cc neo cho ni lc trng ko khincho sc khng ct sau mt n nh c th pht trin.

Vic thit k cc sn tng cng ng trung gian bao gm cc xem xt v mnh, cng v cng .

219/333



mnh

Khi chn chiu dy v chiu rng ca mt sn tng cng ng trung gian, mnh ca cu kin nh ra phi c gii hn ngn nga mt n nh

cc b. i vi cc sn tng cng chu nn, ta c cng thc:

trong

bt : chiu rng ca sn tng cng nh ra

tp : chiu dy ca sn tng cng nh ra

k : h s mt n nh ca tm (Bng 6.9.4.2.1)

Fys : cng chy ca sn tng cng

t

p

b Ekt F

ys

220/333



221/333



mnh

i vi cc tm c dc theo mt cnh, k= 0.45 i vi cc cu kin nhra khng phi l mt phn ca thp cn nh hnh.

Trong Tiu chun thit k cu 22TCN 27205, cc yu cu v mnh chosn tng cng ng trung gian c cho bi hai biu thc sau y, trong

gii hn i vi b rng bt ca sn tng cng mi bn phn bn bng

50 0.4830

0.25 16

t p

ys

f t p

d Eb tF

b b t

(6.10.8.1.2)

222/333



cng

Cc sn tng cng ng trung gian xc nh ng bin thng ng cakhoang phn bn bng.

Chng phi c cng khng bin dng ln (vn gi c thngtng i) v cho php bn bng pht trin cng sau mt n nh ca n.

223/333



224/333



cng

Mt quan h l thuyt c th c xy dng khi xem xt cng tng igia mt sn tng cngng trung gian v mt tm bn bng.

Quan h ny c th c biu din bng thng s khng th nguyn

vi

w

stct

EIEI

3

212 1 w

w

EDtEI

23

12 1 tt

IDt w

trong

: h s Pot xng

D : chiu cao phn bn bngtw : chiu dy phn bn bngIt : m men qun tnh ca sn tng cng

ng trung gian225/333



M men qun tnh ca sn tng cngng trung gian ly i vi mp tipgip vi phn bn bng khi b tr sn tng cng n v ly i vi ng

tim phn bn bng trong trng hp sn tng cng kp.

Vi = 0.3 , cng thc trn c th c vit li

i vi mt phn bn bng khng c sn tng cng dc, gi tr ca t m bo rng phn bn bng c th chu c ng sut on ti hn do ct crl xp x

trong , = do/D v mt l mt h s phng i, xt n ng x sau mt n nh

v nh hng bt li ca s khng hon ho (trong ch to).

3

10.92t tDtI w

21 15 6t tm

226/333



Khi ly mt = 1.3 ta c3 312.5 0.7 0.55tI Dt Dt w w

3

t oI d t J w2

2.5 2.0 0.5po

DJ

d

Tiu chun thit k cu 22TCN 27205 a ra yu cu i vi m men quntnh ca mt sn tng cngng bt k bng hai cng thc

trong : do l khong cch gia cc sn tng cng ng trung gian; Dp l

chiu cao bn bng i vi cc bn bng khng c cc g tng cng dc hoc

chiu cao ln nht ca panen ph i vi cc bn bng c cc g tng cng dc

v

Khi thay cng thc trn vi Dp = D v = do/D3 312.5 0.8 0.5t w o wI Dt d t

(6.10.8.1.3)

227/333



Cng Mt ct ngang ca sn tng cngng trung gian phi ln chu c

cc thnh phn thng ng ca ng sut nghing trong phn bn bng.

C s xc nh din tch mt ct ngang cn thit c da trn cc nghincu ca Basler (1961a).

S dng nh ngha C = cr/y, lc nn trong sn tng cngng tr thnh

vi y l cng chy ca khoang phn bn bng.

2

1 12 1s y

F Dt C w

228/333



Cng Cng thc ny c th vit dng khng th nguyn bng cch chia cho

thnh

trong , l t s mnh ca phn bn bng D/tw.

Khi s dng nh ngha y = Fyw/E v k ly bng

biu thc i vi C tr thnh

22 21, 12 1s yFF CD

2

45.34k

2 2 21.57 1.57 45.34

/ yw y

EkCFD t

w229/333



Cng Khi thay cng thc C vo cng thc F(,), ta c

Ni lc ln nht ca sn tng cngng trung gian c th c xc nht php ly vi phn tng phn ca cng thc trn i vi v

Khi cho cc biu thc ny bng 0, v gii hai cng thc ng thi. Kt qu thuc

22 3 21 3.1 1, 4.22 1yF

1.18 6.22 / y

230/333



Cng Khi thay = 1.18 vo cng thc Fs, ni lc ln nht ca sn tng cng

ng trung gian tr thnh

Ni lc ny s l lc dc trc ca sn tng cng nu sc khng ct ln nhtca khoang phn bn bng c khai thc ht, tc l Vu = Vn.

Trong trng hp Vu < Vn, ni lc ca sn tng cng s c gim i t lthun, nh vy,

trong

Fyw = y l cng chy ca phn bn bng.

,max 0.14 1s yF Dt C w

0.14 1 us ywn

VF Dt F CV w

231/333



Cng thc Fs c xy dng cho mt cp sn tng cngng trung gian btr i xng hai bn phn bn bng.

Kiu cu to khc l ch c sn tng cng n mt pha ca phn bnbng.

Basler (1961) cho bit rng, i vi cc sn lm bng tm ch nht, sntng cng mt pha cn phi bng t nht 2.4 ln tng din tch ca sn

tng cng kp.

Cng theo ng, mt thp gc u cnh c s dng l sn tng cng mtpha i hi mt din tch bng 1.8 ln din tch ca mt cp sn.

0.14 1 us ywn

VF BDt F CV w

232/333



Mt phn ca phn bn bng c th c gi thit l tham gia chu lc dctrc thng ng.

Tiu chun thit k cu 22TCN 27205 coi phn bn bng tham gia chu lccng vi sn tng cng vi mt chiu di hu hiu bng 18tw.

Lc nn ca sn tng cng sau khi tr phn tham gia ca phn bn bng

Din tch As ca sn tng cng chu hiu ng trng ko ca phn bnbng c xc nh bng cch chia Fs cho cng ca sn tng cng Fys

vi Vr = Vn, v hng s 0.14 c lm trn ln 0.15.

20.14 1 18us yw ywn

VF BDt F C t FV w w

20.15 1 18 ywusr

FVA BDt C tV F

w w ys(6.10.8.1.4)

233/333

11.SNTNGCNG11.3SNTNGCNGNGTIGI


Sn tng cng chu lc l sn tng cngng c b tr ti v tr cphn lc gi v cc ti trng tp trung khc.

Lc tp trung c truyn qua cc bn bin v c bi s p mt ln usn tng cng.

Cc sn tng cng chu lc c lin kt vi phn bn bng v ng vai trng bin thng ng neo lc ct t hiu ng trng ko.

234/333



Mt ct dm thp cn Sn tng cng chu lc cn thit cho phn bn bng ca dm thp cn ti

cc im c lc tp trung khi lc ct c h s vt qu

vi b l h s sc khng i vi p mt (6.5.4.2), v Vn l sc khng ct danh

nh.

0.75u b nV V (6.10.8.2.11)

235/333



mnh Cc sn tng cng chu lc c thit k l nhng cu kin chu nn chu

lc tp trung thng ng.

Chng thng c cu to bi mt hay nhiu cp tm ch nht b tr ixng hai bn phn bn bng.

Chng chy di trn ton b chiu cao ca phn bn bng v rng gn nh timp ngoi ca cc bn bin.

Cnh nh ra ca sn tng cng chu lc phi m bo yu cu sau v mnh

trong , bt l chiu rng ca cnh nh ra, tp l chiu dy ca cnh nh ra v Fys l

cng chy ca sn tng cng.

0.48tp ys

b Et F (6.10.8.2.21)

236/333



237/333



Cng chu p mt Cc u ca sn tng cng chu lc phi c mi nhn c th p st

vo bn bin m n tip nhn lc, bn bin di ti gi ta v bn bin trn

i vi lc tp trung trung gian.

Nu cc u khng c mi th chng phi c lin kt vi bn bin chulc bng mt ng hn gc thu hon ton.

Din tch chu p mt hu hiu nh hn din tch nguyn ca sn tngcng v u sn tng cng phi c ct vt nhng ch cho ng

hn gc lin tc gia phn bn bng v bn bin (mt ct AA).

238/333



Cng chu p mt Sc khng p mt da trn din tch p mt hu hiu ny v cng chy

Fys ca sn tng cng l

trong , Br l sc khng p mt c h s, b l h s sc khng i vi p mt

(6.5.4.2) v Apn l din tch hu hiu ca phn sn tng cng nh ra.

r b pn ysB A F (6.10.8.2.31)

239/333



Sc khng lc dc trc Sn tng cng chu lc cng vi mt phn bn bng kt hp lm vic nh

mt ct chu lc nn dc trc (mt ct BB).

Din tch hu hiu ca mt ct ct c ly bng din tch ca tt c cc sntng cng cng vi mt di bn bng c chiu rng v mi pha sn tng

cng ngoi cng (nu c nhiu cp) khng ln hn 9tw.

240/333



Do cc sn tng cng chu lc p st vo bn bin nn s s cn tr quay hai u v chiu di ct hu hiu hai u cht kL c th ly bng 0.75D, vi D

l chiu cao ca phn bn bng.

o i vi b phan chnh: kL/r 120

o i vi b phan lin ke t: kL/r 140

M men qun tnh ca mt ct ct c s dng trong tnh ton bn knhqun tnh c ly i vi trc trng tm ca phn bn bng.

Ngi thit k thng, thin v an ton, b qua phn ng gp ca phn bnbng khi tnh m men qun tnh v ly n gin l tng cc m men qun tnh

ca sn tng cng i vi cnh tip gip vi bn bng.

(6.9.3)

241/333



Sc khng lc dc trc c h s Pr c tnh t

vi c l h s sc khng i vi nn (6.5.4.2), v Pn l sc khng nn danh nh

(6.9.4.1).

r c nP P

242/333

11.SNTNGCNG11.3SNTNGDC(6.10.8.3)


ni no yu cu, cc g tng cng dc c th gm hoc tm c hn dcvo mt bn ca bn bng, hoc thp gc bt bulng, v phi c t mt

khong cch 2Dc/5 t pha trong ca bn cnh chu nn.

Dc l chiu cao ca bn bng chu nn mt ct c ng sut un nn ln nht.

243/333



Chiu rng phn cha (6.10.8.3.2) Chiu rng phn cha, bt, ca g tng cng phi tha mn:

trong :

ts = chiu dy ca g tng cng (mm)

Fyc = cng chy nh nht quy nh ca bn cnh chu nn lin k (MPa)

0.48l syc

Eb tF

244/333



Mmen qun tnh (6.10.8.3.3) Cc c trng mt ct ca g tng cng phi cn c trn din tch hiu dng

gm c g tng cng v di trung tm ca bn bng khng vt qu 18tw.

Cc g tng cng dc phi tha mn:

trong :

Il = mmen qun tnh ca g tng cng dc v di bn bng quanh

mp tip xc vi bn bng (mm4)

r = bn knh hi chuyn ca g tng cng dc v di bn bng quanh

mp tip xc vi bn bng (mm)

do = khong cch g tng cng ngang (mm)

Fyc = cng chy nh nht ca bn cnh chu nn lin k (MPa)

2

3 2.4 0.13ol wdI DtD

0.23 yco

Fr d

E

245/333

THITKSN TNGCNGNG S dung sn tng cng mt bn cho tie t dien ch I, d = 1565mm

Khoang cach 02 sn tng cng lien k do = 2032mm

Cng thep sn tng cng Fys = 250Mpa

Ban bung D = 1524mm, cng thep ban bung Fyw = 345Mpa

Lc ca t tnh toan taivitr sn tng cng Vu = 2000kN


246/333

1) mnh sn tng cng Chon kch thc ban au cua sn tng cng

bt = 110mm tp = 10mm

Kiem tra kch thc sn tng cng


50 102 110 0.48 13630 t p ys

d Emm b mm t mmF

0.25 51 110 16 160f t pb mm b mm t mm

(OK)

(OK)

247/333

2) cng sn tng cngMomen quan tnh sn tng cng o i vi mep canh ban bung

Kiem tra momen quan tnh Ban bung khngco sn tng cng doc


3 3 42032 16 0.5 4161536t o wI d t J mm

2

2.5 2.0 0.594 0.5o

DJd

0.5J

(OK)

3 3410 110 4436667

3 3p t

t

t bI mm

248/333

3) Cng Dien tch sn tng cng

Dien tch sn tng cng phai thoa man

Vu = 2000kN, C = 0.75, Vr = 4297 kN (Vd 6)

Sn tng cng am bao chiu lc.Tuy nhin, ban thn ban bung a u sc khang ca t (ban bung day).

Do o, sn tng cngch thie t k cau tao.


2110 10 1100sA mm

20.15 1 18 ywusr

FVA BDt C tV F

w w ys

22000 3450.15 2.4 1524 16 1 0.75 18 164297 250s

A 24949sA mm (OK)

249/333

THITKSN TNGCNGTIGI Cng thep sn tng cng

Fys = 250Mpa

Cng thep ban bung

Fyw = 345Mpa

Phan lc tnh toan taivitr go i

Ru = 3500kN


250/333

1) mnh sn tng cng Chon kch thc ban au cua sn tng cng

bt = 178mm tp = 16mm

Kiem tra kch thc sn tng cng

2) Sc khng ta chu p mt Dien tch to i thieu cua sn tng cng


178 20000011.0 0.48 0.48 13.616 250

t

p ys

b Et F (OK)

r b pn ys uB A F R 3

2

,min

3500 10 140001.0 250

upn

b ys

RA mmF

251/333

2) Sc khng ta chu p mt Neu s dung sn tng cng i hai bn ban bung

3) Sc khng nn dc trc Dien tch cua 01 sn tng cng

Dien tch hu hieu cua toan b sn tng cng


4( 4 ) (18 204)pn t w p w wA b t t t t 2

,min4 (178 64) 16 (18 16 204) 16 15168pn pnA mm A

2178 16 2848s t pA b t mm

4 (18 204)pn s w wA A t t

(OK)

24 2848 (18 16 204) 16 19264pnA mm 252/333

3) Sc khng nn dc trc Momen quan tnh cua STC o i vi truc qua tm ban bung

Ban knh quan tnh cua tie t dien sn tng cng


24 4t o sI I A y 23

416 178 178 164 4 2848 13726600512 2t

I mm

137266005 84.419264

ts

pn

Ir mmA

0.75 0.75 1524 13.54 12084.4s s

kL Dr r

(OK)

253/333

3) Sc khng nn dc trc

Sc khang nen doc truc danh inh cua STC

Sc khang nen doc truc tnh toan cua STC

Vay, s dung loai sn tng cng kp hai pha cua ban bung taivitr go iam bao kha nng chiu lc.


2 213.54 250 0.023 2.25200000

ys

s

FkLr E

0.0230.66 0.66 250 19264 4770193n ys pnP F A N

(OK)

0.9 4770193 4293174 4293r c nP P N kN 3500r uP R kN

254/333

12.LINKT MINI12.1GIITHIU


Trong cu thp hin nay, c hai loi lin kt thng c s dng: lin ktinh v lin kt hn.

inh i din cho inh tn, bu lng, bu lng cng cao, cht Cc loi linkt inh c cp trong chng ny l lin kt bng bu lng thng v lin

kt bng bu lng cng cao.

Lin kt hn c th c dng cho cc mi ni ngoi cng trng nhng nichung, ch yu c s dng ni cc b phn trong nh my.

255/333

12.LINKT12.1GIITHIU


Tu theo trng hp chu lc, cc lin kt c phn chia thnh lin kt ngin, hay lin kt chu lc ng tm, v lin kt chu lc lch tm.

256/333

12.LINKT12.2BULNGTHNG


Bu lng thng c lm bng thp t ccbon ASTM A307 c cng chuko 420 MPa.

Bu lng A307 c th c u dng hnh vung, lc gic hoc u chm. Bu lng thp thng khng c php s dng cho cc lin kt chu mi Bu lng thng, lc p cht do xit bu lng khng c tnh n. Bu lng thng c quy nh trong Tiu chun thit k cu 22TCN 27205 l

bu lng ASTM A307.

257/333

12.LINKT12.3BULNGCNGCAO


Bu lng cng cao phi c cng chu ko nh nht 830 MPa cho ccng knh d = 16 27 mm v 725 MPa cho cc ng knh d = 30 36 mm.

Bu lng cng cao c th dng trong cc lin kt chu ma st hoc lin ktchu p mt.

Lin kt chu p mt chu c ti trng ln hn nhng gy bin dng ln khichu ng sut i du nn ch c dng trong nhng iu kin cho php.

Trong cu, mi ni bu lng chu p mt khng c dng cho cc lin kt chung sut i du.

258/333

12.LINKTTHIE TKE CA UTHE P

TS.NGUYENCA NHTUA N

Lin kt bu lng cng cao chu ma st thng dng trong kt cu cu chuti trng thng xuyn gy ng sut i du hoc khi cn trnh bin dng

trt ca mi ni.

Lin kt bu lng cng cao chu p mt ch c dng hn ch cho cc bphn chu ng sut mt du v cho cc b phn th yu.

Trong xy dng cu, c lin kt bu lng cng cao v lin kt hn u cth c s dng cho cc mi ni ngoi cng trng song lin kt bu lng

cng cao c dng l ch yu.

Lin kt hn ch c s dng trong cc lin kt th yu, khng chu hot ti,dng lin kt cc tmmt cu hoc cc b phn khng chu lc chnh.

12.3BULNGCNGCAO

259/333


TS.NGUYENCA NHTUA N

Trong thc t, thng s dng hai loi bu lng cng cao A325 v A490vi u m v ai c theo tiu chun ASTM.

Bu lng CC A325 c th bng thp chng r.

12.3BULNGCNGCAO

260/333


TS.NGUYENCA NHTUA N

Cc kch c bu lng v ng ren rng c th tham kho theo bng

ng knh bu lng(mm)

Chiu di rendanh inh (mm)

lchren(mm)

Chiu di tngcng ren (mm)

12.7 25.4 4.8 30.215.9 31.8 5.6 37.319.0 35.0 6.4 41.122.2 38.1 7.1 45.225.4 44.5 7.9 52.328.6 50.8 8.6 59.431.8 50.8 9.7 60.535.0 57.2 11.2 69.338.1 57.2 11.2 68.3

12.3BULNGCNGCAO

261/333


TS.NGUYENCA NHTUA N

Cc kch thc l bu lng khng c vt qu cc tr s trong bng

12.3BULNGCNGCAO

262/333


TS.NGUYENCA NHTUA N

Trong cc lin kt bng bu lng cng cao chu ma st, cc bn ni cp vo nhau nh lc xit bu lng.

Lc xit bu lng cn ln khi chu ct, ma st gia cc bn thp khnng chng li s trt.

Lin kt chu ma st yu cu b mt tip xc ca cc bn ni phi c lmsch khi sn, du m v cc cht bn.

Cng c th dng lin kt trong bu lng b p mt, s dch chuyn ca ccbn ni c ngn cn bi thn bu lng.

L qu c c th dng trong mi lp ca lin kt bu lng cng cao chuma st.

Khng dng l qu c trong lin kt kiu p mt.

12.3BULNGCNGCAO

263/333


TS.NGUYENCA NHTUA N

L van ngn c th dng trong mi lp ca lin kt chu ma st hoc p mt. Trong lin kt chu ma st, cnh di l van c dng khng cn ch n

phng tc dng ca ti trng, nhng trong lin kt chu p mt, cnh di l

van cn vung gc vi phng tc dng ca ti trng.

L van di ch c dng trong mt lp ca c lin kt chu ma st v linkt chu p mt.

L van di c th c dng trong lin kt chu ma st khng cn ch nphng tc dng ca ti trng, nhng trong lin kt chu p mt, cnh di l

van cn vung gc vi phng tc dng ca ti trng.

12.3BULNGCNGCAO

264/333


TS.NGUYENCA NHTUA N

Trong xy dng cu, ng knh bu lng nh nht cho php l 16 mm, tuynhin khng c dng bu lng ng knh 16 mm trong kt cu chu lc

chnh.

Vic quy nh khong cch nh nht, khong cch ln nht gia cc bu lngcng nh t bu lng ti mp cu kin nhm nhng mc ch khc nhau.

Khong cch nh nht gia cc bu lng c quy nh nhm m bo khongcch trng gia cc ai c v khng gian cn thit cho thi cng (xit bu lng).

Khong cch nh nht t bu lng ti mp cu kin c quy nh nhm mcch chng x rch thp c bn.

Khong cch ln nht gia cc bu lng cng nh t bu lng ti mp cu kinc quy nh nhm m bo mi ni cht ch, chng m v chng lt bi

cng nh chng cong vnh cho thp c bn.

12.3BULNGCNGCAO

265/333


TS.NGUYENCA NHTUA N

Yu cu v b tr bu lng

Vic quy nh khong cch nh nht, khong cch ln nht gia cc bu lngcng nh t bu lng ti mp cu kin nhm nhng mc ch khc nhau.

Khong cch nh nht gia cc bu lng c quy nh nhm m bo khongcch trng gia cc ai c v khng gian cn thit cho thi cng (xit bu lng).

Khong cch nh nht t bu lng ti mp cu kin c quy nh nhm mc

ch chng x rch thp c bn.

Khong cch ln nht gia cc bu lng cng nh t bu lng ti mp cu kinc quy nh nhm m bo mi ni cht ch, chng m v chng lt bi

cng nh chng cong vnh cho thp c bn.

12.3BULNGCNGCAO

266/333


TS.NGUYENCA NHTUA N

Yu cu v b tr bu lng

Khong cch t tim ti tim ca cc bu lng khng c nh hn 3d. Khong cch t tim l ti mp thanh ni chung, khng c ln hn 8 ln

chiu dy ca thanh ni mng nht v khng c ln hn 125mm.

Khong cch nh nht t tim l ti mp cu kin l hm ca kch thc bulng v dng gia cng mp, c cho trong Bng 6.13.2.6.61.

Khong cch gia cc bu lng v khong cch t bu lng ti mp, k hiutng ng l s v Le.

12.3BULNGCNGCAO

267/333


TS.NGUYENCA NHTUA N

12.3BULNGCNGCAO

268/333


TS.NGUYENCA NHTUA N

Trc khi xem xt cng cc cp c trng ca bu lng, chng ta cnnghin cu cc trng hp ph hoi khc nhau c th xy ra trong lin kt

bng bu lng chu ct.

C hai dng ph hoi ch yu: ph hoi ca bu lng v ph hoi ca b phnc lin kt.

ng sut ct trung bnh trong trng hp ny s l

trong , P l lc tc dng ln mt bu lng, A l din tch mt ct ngang ca bu

lng v d l ng knh ca n.

Lc tc dng c th c vit l:

12.3LINKTBULNGCHUCT:CCTRNGHPPHHOI

2 / 4 vP PfA d

vP f A269/333


TS.NGUYENCA NHTUA N


270/333


TS.NGUYENCA NHTUA N

Mc d lc tc dng trong trng hp nykhng hon ton ng tm nhng lch

tm l nh v c th c b qua.

S phn tch cn bng lc cc phn cathn bu lng cho thy rng, mi din tch

mt ct ngang chu mt na ca ti trng

ton phn, hay, hon ton tng ng,

c hai mt ct ngang tham gia chu ti

trng ton phn.

Trong trng hp ny, ti trng l P = 2fvAv y l trng hp ct kp (ct hai mt).


271/333


TS.NGUYENCA NHTUA N

Lin kt bu lng trong hnh ch vimt mt chu ct c gi l lin kt

chu ct n (ct mt mt).

S tng hn na b dy vt liu tilin kt c th lm tng s mt phng

ct v lm gim hn na lc tc dng

trn mi mt ct.

Tuy nhin, iu ny s lm tng chiudi ca bu lng v khin cho n c th

phi chu un.


272/333


TS.NGUYENCA NHTUA N

Cc tnh hung ph hoi khc trong lin kt chu ct bao gm s ph hoi cacc b phn c lin kt v c chia thnh hai trng hp chnh.

1) S ph hoi do ko, ct hoc un ln trong cc b phn c lin kt.

Nu mt cu kin chu ko c lin kt, lc ko trn c mt ct ngang

nguyn v mt ct ngang hu hiu u phi c kim tra.

Tu theo cu to ca lin kt v lc tc dng, cng c th phi phn tch v

ct, ko, un hay ct khi.

Vic thit k lin kt ca mt cu kin chu ko thng c tin hnh song

song vi vic thit k chnh cu kin v hai qu trnh ph thuc ln nhau.


273/333


TS.NGUYENCA NHTUA N

2) S ph hoi do ko, ct hoc un ln trong cc b phn c lin kt.

S ph hoi ca b phn c lin kt do s p mt gy ra bi thn bu lng.

Nu l bu lng rng hn mt cht so vi thn bu lng v bu lng c gi

thit l nm lng lo trong l th khi chu ti, s tip xc gia bu lng v b

phn c lin kt s xy ra trn khong mt na chu vi ca bu lng.

ng sut s bin thin t gi tr ln nht ti A n bng khng ti B; n

gin ho, mt ng sut trung bnh, c tnh bng lc tc dng chia cho din

tch tip xc, c s dng.


274/333


TS.NGUYENCA NHTUA N

Do vy, ng sut p mt s c tnh l fp =P/(dt), vi P l lc tc dng lnbu lng, d l ng knh bu lng v t l b dy ca b phn b p mt.

Lc p mt c tnh


pP f d t

275/333


TS.NGUYENCA NHTUA N

Vn p mt c th phc tp hn khi c mt mt bu lng gn hoc khi gn mp u cu kin theo phng chu lc.

Khong cch gia cc bu lng v t bu lng ti mp s c nh hng ncng chu p mt.


276/333


TS.NGUYENCA NHTUA N

Cng chu p mt khng ph thuc vo loi bu lng v ng sut c xemxt l trn b phn c lin kt ch khng phi trn bu lng.

Do vy, cng chu p mt cng nh cc yu cu v khong cch bu lng vkhong cch ti mp u cu kin, l nhng i lng khng ph thuc vo

loi bu lng, s c xem xt trc khi bn v cng chu ct v chu ko

ca bu lng.

Cc quy nh ca Tiu chun AISC v cng chu p mt cng nh tt ccc yu cu i vi bu lng cng cao c c s l cc quy nh ca tiu

chun RCSC, 2000 (Hi ng nghin cu v lin kt trong kt cu).

Phn trnh by sau y gii thch c s ca cc cng thc cho cng chup mt trong Tiu chun AISC cng nh AASHTO LRFD.

12.4CNGCHUPMT

277/333


TS.NGUYENCA NHTUA N

Mt trng hp ph hoi c th xy ra do p mt ln l s x rch ti u mtcu kin c lin kt.

Nu b mt ph hoi c l tng ho th ti trng ph hoi trn mt tronghai mt s bng ng sut ph hoi ct nhn vi din tch chu ct, hay

trong

0.6Fu ng sut ph hoi ct ca cu kin c lin kt

Lc khong cch t mp l ti mp cu kin c lin kt

t chiu dy ca cu kin c lin kt

Cng tng cng l

12.4CNGCHUPMT

0.62n

u c

RF L t

2 0.6 1.2n u c u cR F L t F L t (1)278/333


TS.NGUYENCA NHTUA N

12.4CNGCHUPMT

279/333


TS.NGUYENCA NHTUA N

12.4CNGCHUPMT S x rch ny c th xy ra ti mp ca mt cu kin c lin kt, nh trong

hnh v, hoc gia hai l theo phng chu lc p mt. ngn nga bin

dng qu ln ca l, mt gii hn trn c t ra i vi lc p mt c

cho bi cng thc 4.1. Gii hn trn ny l t l thun vi tch s ca din tch

chu p mt v ng sut ph hoi, hay

trong

C hng s

d ng knh bu lng

t chiu dy cu kin c lin kt

n u uR C F C d t F din tch p mt (2)

280/333


TS.NGUYENCA NHTUA N

12.4CNGCHUPMT Tiu chun AISC s dng cng thc (1) cho cng chu p mt vi gii hn

trn c cho bi cng thc (2).

Nu c bin dng ln, m iu ny thng xy ra, th C c ly bng 2.4 Gi tr ny tng ng vi gin di ca l bng khong inch (6.25mm). Nh vy

1.2 2.4n u c uR F L t d t F

281/333


TS.NGUYENCA NHTUA N

12.4CNGCHUPMTSc khng p mt cc l bulng (6.13.2.9)

i vi cc l chun, l qu c, l van ngn chu tc dng lc theo miphng v l van di song song vi phng lc tc dng:

Khi khong cch tnh gia cc l bu lng khng nh hn 2d v khong cch

tnh n u thanh khng nh hn 2d:

Khi khong cch tnh gia cc l bu lng nh hn 2d hoc khong cch

tnh n u thanh nh hn 2d:

2.4n uR d t F

1.2n c uR L t F

282/333


TS.NGUYENCA NHTUA N


i vi cc l van di vung gc vi phng lc tc dng:Khi khong cch tnh gia cc l bu lng khng nh hn 2d v khong cch tnh

n u thanh khng nh hn 2d:

Khi khong cch tnh gia cc l bu lng nh hn 2d hoc khong cch tnh n

u thanh nh hn 2d:

2.0n uR d t F

n c uR L t F Lc khong cch trng, theo phng song song vi lc tc dng, t mp

ca l bu lng ti mp ca l gn k hoc ti mp ca cu kint chiu dy cu kin c lin ktd ng knh bu longFu ng sut ko gii hn ca cu kin c lin kt (khng phi ca bu

lng) 283/333


TS.NGUYENCA NHTUA N


Khi tnh ton cng p mt cho mt bu lng, s dng khong cch t bulng ny n bu lng lin k hoc n mp theo phng lc tc dng vo cu

kin lin kt.

i vi trng hp trong hnh v, lc p mt s tc dng trn phn bn trica mi l.

Do vy, cng cho bu lng 1 c tnh vi Lc bng khong cch gia haimp l v cng cho bu lng 2 c tnh vi Lc bng khong cch ti mp

cu kin c lin kt.

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TS.NGUYENCA NHTUA N


285/333


TS.NGUYENCA NHTUA N


Trong ti liu ny, bin dng c xem xt l trn gc thit k. Cng chu p mt tnh ton ca mt bu lng n, do vy, c th c tnh

bng Rn, vi l h s sc khng i vi p mt ca bu lng ln thp c bn

= 0.75 theo AISC

= 0.80 theo AASHTO LRFD (1998)

286/333


TS.NGUYENCA NHTUA N


Cho cc bu lng gn mp, dng Lc = Le dh/2 Cho cc bu lng khc, dng Lc = s dh

trong

Le khong cch t tm l ti mp

s khong cch tim n tim ca l

dh ng knh l

Khi tnh khong cch Lc, cn s dng ng knh l thc t dh = d + 2mm

287/333


TS.NGUYENCA NHTUA N

12.5CNGCHUCTCABULNG (6.13.2.7) Sc khng ct danh nh ca bu lng cng cao hoc bulng ASTM A307

TTGH cng trong cc mi ni m khong cch gia cc bu lng xa nht o

song song vi phng lc tc dng nh hn 1270 mm c ly nh sau:

Khi ng ren rng khng ct qua mt phng ct

Khi ng ren rng ct mt phng ct

trong :

Ab din tch bu lng theo ng knh danh nh (mm2)Fub cng chu ko nh nht ca bu lng (MPa)Ns s mt phng ct cho mi bu lng

0.48n b ub sR AF N

0.38n b ub sR AF N

(16.3.2.71)

(16.3.2.72)

288/333


TS.NGUYENCA NHTUA N

12.5CNGCHUCTCABULNG (6.13.2.7) Sc khng ct danh nh ca bu lng trong cc mi ni di hn 1270 mm

c ly bng 0.80 ln tr s tnh theo cc cng thc 1 hoc 2.

Sc khng ct danh nh ca bu lng thng ASTM A307 c xc nh theocng thc 2.

Khi b dy bn ni ca mt bu lng A307 ln hn 5 ln ng knh, sckhng danh nh s gim i 1.0% cho mi 1.50 mm ln hn 5 ln ng knh.

Sc khng ct c h s ca bu lng l Rn , vi = 0.65 i vi bu lngthng v = 0.80 i vi bu lng cng cao.

289/333


TS.NGUYENCA NHTUA N

12.5CNGCHUCTCABULNG (6.13.2.7)Ct khi

Vi cc mi ni chu ko thng thng khi tin hnh th nghim ta thy cmt phn hoc mt khi vt liu (ca bn nt hoc ca cu kin chu ko) c

th b x rch.

CT

KO

a b

c290/333


TS.NGUYENCA NHTUA N

12.5CNGCHUCTCABULNG (6.13.2.7) Qu trnh ny khi tnh ton ta s da trn gi thit rng trong hai mt ph

hoi th mt mt s t n cng ph hoi v mt kia t n cng

chy.

iu ny c ngha l nu ph hoi xy ra trn mt chu ct th mt chu ko st n gii hn chy hoc nu ph hoi xy ra trn mt chu ko th mt chu

ct s t n gii hn chy.

C hai mt chu ko v chu nn ny s to nn sc khng ct khi, hay sckhng ct khi l tng sc khng ca hai mt chu ko v chu ct.

291/333


TS.NGUYENCA NHTUA N

12.5SCKHNGPHHOICTKHI(6.13.4) Nu Atn 0.58Avn th ph hoi xy ra trn mt chu ko mt chu ct lc

t n gii hn chy v sc khng ct khi danh nh c tnh nh sau:

Nu Atn < 0.58Avn th ph hoi xy ra trn mt chu ct, mt chu ko lc t n gii hn chy v sc khng ct khi danh nh c tnh nh sau:

Sc khng ct khi tnh ton c tnh nh sau:

0.58nbs y vg u tnP F A F A

0.58nbs u vn y tgP F A F A

rbs bs nbsP P

292/333


TS.NGUYENCA NHTUA N

12.5SCKHNGPHHOICTKHI(6.13.4)Trong :

Pnbs : Sc khng ct khi danh nh

Prbs : Sc khng ct khi tnh ton

bs : H s sc khng ct khi (bs =0.8)

Avg : Din tch nguyn chu ct

Avn : Din tch thc chu ct

Atg : Din tch nguyn chu ko

Atn : Din tch thc chu ko

293/333


TS.NGUYENCA NHTUA N

12.5SCKHNGPHHOICTKHI(6.13.4)

294/333


TS.NGUYENCA NHTUA N

12.5SCKHNGPHHOICTKHI(6.13.4)

295/333


TS.NGUYENCA NHTUA N

12.6SCKHNGTRT(6.13.2.8) Lin kt bng bu lng cng cao c phn loi thnh lin kt chu ma st

hoc lin kt chu p mt.

Mt lin kt chu ma st l lin kt m trong s trt b cn tr, ngha llc ma st phi khng b vt qu.

Trong mt lin kt chu p mt, s trt c th xy ra v s ct cng nh pmt thc s xy ra.

Trong mt s loi kt cu, c bit l kt cu cu, lin kt c th phi chunhiu chu k ng sut i du.

Trong nhng trng hp nh vy, mi ca bu lng c th l quyt nh v sdng lin kt chu ma st l thch hp.

296/333


TS.NGUYENCA NHTUA N

12.6SCKHNGTRT(6.13.2.8) Tuy nhin, trong hu ht cc kt cu, s trt hon ton c chp nhn v

ch cn cu to lin kt chu p mt.

Bu lng A307 ch c s dng trong cc lin kt chu p mt. Vic lp t ng quy cch v s t c lc ko ban u ng quy nh l

cn thit i vi cc lin kt chu ma st.

Cn trong cc lin kt chu p mt, cc yu cu i vi lp t bu lng thc tch l chng c ko cc cu kin lin kt p cht vo nhau.

297/333


TS.NGUYENCA NHTUA N

12.6SCKHNGTRT(6.13.2.8) Quan h ny c phn nh bng cng thc xc nh sc khng trt danh

nh ca mt bu lng cng cao nh sau

trong

n h s s tR K K N P

Ns S mt mast ca mi bu lng (thc t bng s mt ct ca bu lng)

Pt lc ko ti thiu yu cu trong bu lng (Bng 6.13.2.81)

Kh h s kch thc l (Bng 6.13.2.82)

Ks h s iu kin b mt (Bng 6.13.2.83)

298/333


TS.NGUYENCA NHTUA N

12.6SCKHNGTRT(6.13.2.8)

299/333


TS.NGUYENCA NHTUA N

12.6SCKHNGTRT(6.13.2.8)

300/333


TS.NGUYENCA NHTUA N

12.6SCKHNGTRT(6.13.2.8)

301/333


TS.NGUYENCA NHTUA N

12.6SCKHNGTRT(6.13.2.8)

Tiu chun i vi cc loi b mt:Loi A: cc lp cu bn c lm sch, b mt khng sn v c lm sch

bng thi vi lp ph loi A.

Loi B: cc b mt khng sn v c lm sch bng thi vi lp ph loi B.

Loi C: b mt m km nng, c lm nhm bng bn chi st sau khi m.

Sc khng trt tnh ton (c h s) ca bu lng cng cao cng chnh lsc khng trt danh nh ( = 1.0)

r n h s s tR R K K N P

302/333


TS.NGUYENCA NHTUA N

12.7LINKTBULNGCNGCAOCHUKO (6.13.2.10)

Khi lc ko tc dng ln mt bu lng khng c cng trc th lc ko trongbu lng s bng lc tc dng.

Tuy nhin, nu bu lng c ko trc th mt phn ln ti trng tc dngc s dng vo vic lm gim bt lc nn hay lc p gia cc b phn c

lin kt.

Cc bu lng cng cao chu ko dc trc phi c cng n lc quy nhtrong bng 4.3.

Lc tc dng ln lin kt chu ko c xc nh bng tng cng lc do titrng bn ngoi sinh ra v lc do tc ng by ln i vi bu lng.

303/333


TS.NGUYENCA NHTUA N


Theo Tiu chun thit k cu 22 TCN 27205, sc khng ko danh nh ca bulng cng cao, Tn, c lp vi mi lc xit ban u, c tnh bng cng

thc

trong :

Ab : din tch bu lng theo ng knh danh nh (mm2)

Fub : cng chu ko nh nht quy nh ca bu lng (MPa)

0.76n b ubT AF

304/333


TS.NGUYENCA NHTUA N


Tc ng nh ln

Do tc ng by ln gy ra bi s bin dng ca cc cu kin trong lin ktchu ko, bu lng cng cao chu mt lc ko b sung.

305/333


TS.NGUYENCA NHTUA N


Tc ng nh ln

Lc ko do tc ng by c tnh bng33

8 328000u ub tQ Pa

Qu lc nh trn mt bu lng do ti trng c h s, c ly bng khng

khi lc l m (N)

Pu lc ko trc tip trn mt bu lng doti trng c h s (N)

a khong cch t tim bu lng n mp tm (mm)

b khongcchttimbulngnchnnghncacukinlin

kt(mm)

t b dy nh nht ca cc cu kin lin kt306/333


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