B Xy dng

TCXDVN 318: 2004

TCXDVN 318: 2004

B Xy dng--------cng ho x hi ch ngha Vit Nam

c lp - T do - Hnh phc

S: 18/2004/Q-BXD----------

H ni, ngy 29 thng 7 nm 2004

Quyt nh ca b trng B Xy dng

V vic ban hnh TCXDVN 318 : 2004 "Kt cu b tng v b tng ct thp - Hng dn cng tc bo tr "

b trng B Xy dng

- Cn c Ngh nh s 36 / 2003 / N-CP ngy 4 / 4 / 2003 ca Chnh ph quy nh chc nng, nhim v, quyn hn v c cu t chc ca B Xy dng.

- Cn c Bin bn s 808 / BB- HKHKT ngy 3 thng 6 nm 2004 ca Hi ng Khoa hc k thut chuyn ngnh nghim thu tiu chun " Tiu chun bo tr kt cu b tng v b tng ct thp cho cc cng trnh xy dng dn dng v cng nghip".

- Xt ngh ca Vin trng Vin KHCN Xy dng ti cng vn s 656 / VKH-KHKT ngy 9 thng 7 nm 2004 v V trng V Khoa hc Cng ngh

quyt nh

iu 1: Ban hnh km theo quyt nh ny 01 Tiu chun xy dng Vit Nam :

TCXDVN 318 : 2004 "Kt cu b tng v b tng ct thp - Hng dn cng tc bo tr ".

iu 2: Quyt nh ny c hiu lc sau 15 ngy k t ngy ng cng bo

iu 3: Cc ng: Chnh vn phng B, V trng V Khoa hc Cng ngh, Vin trng Vin KHCN Xy dng v Th trng cc n v c lin quan chu trch nhim thi hnh Quyt nh ny ./.

Ni nhn:

- Nh iu 3

- VP Chnh Ph

- Cng bo

- B T php

- V Php ch

- Lu VP&V KHCN

B trng b xy dng

Nguyn Hng Qun

TCXDVN tiu chun xy dng Vit Nam

TCXDVN 318: 2004

Xut bn ln 1

Kt cu b tng v B tng ct thp-

hng dn cng tc bo tr

Concrete and Reinforced concrete Structures -

Guide to Maintenance

H Ni - 2004

Li ni u

Tiu chun TCXDVN 318: 2004 Kt cu b tng ct thp- Hng dn cng tc Bo tr do Vin KHCN Xy dng (B Xy dng) bin son, c s phi hp ca U ban son tho quy chun mu b tng cho chu (the International Commitee on Concrete Model Code for Asia ICCMC), V KHCN B Xy dng trnh duyt, B trng B Xy dng ban hnh theo Quyt nh s 18/2004/Q-BXD ngy 29 thng 7 nm 2004.

Mc lc

Phn1- Tng qut v bo tr................................5

1.1 Nhng vn chung....................................................5

1.1.1 Phm vi p dng...............................................................................5

1.1.2 Ti liu vin dn .............................................................................5

1.1.3 Thut ng v nh ngha ..............................................................6

1.2 Nhng vn c bn ca ca bo tr................................8

1.2.1 Yu cu chung................................................................................8

1.2.2 Ni dung bo tr.............................................................................8

1.2.3 Phn loi bo tr ................................................................................9

1.2.4 Dng h hng ca kt cu.............................................................10

1.2.5 Kim tra cng nng ca kt cu trong qu trnh bo tr .......11

1.2.6 Qun l k thut cng tc bo tr.................................................12

Phn 2- Cng tc kim tra.............................13

2.1 Nguyn tc chung ..................................................................13

2.2 Tay ngh v cng c kim tra ........................................13

2.3 Kim tra ban u.....................................................................13

2.4 Kim tra thng xuyn........................................................14

2.4.1 Nguyn tc chung ...................................................................14

2.4.2 Ni dung kim tra thng xuyn.............................................14

2.4.3 Ghi chp v lu gi h s ....................................................15

2.5 Kim tra nh k ........................................................................15

2.5.1 Nguyn tc chung ......................................................................15

2.5.2 Bin php kim tra nh k .......................................................15

2.5.3 Quy nh v k kim tra .........................................................15

2.5.4 Ni dung kim tra nh k ....................................................15

2.5.5 Ghi chp v lu gi h s........................................................15

2.6 Kim tra bt thng........................................................16

2.6.1 Nguyn tc chung ............................................................16

2.6.2 Bin php kim tra bt thng..................................................16

2.6.3 Ni dung kim tra bt thng...............................................16

2.6.4 Ghi chp v lu gi h s......................................................16

2.7 Theo di...................................................................................16

2.7.1 Nguyn tc chung.....................................................................16

2.7.2 t h thng theo di.............................................................17

2.7.3 Vn hnh h thng theo di ....................................................17

2.7.4 Lu gi s liu o................................................................17

2.8 yu cu i vi kim tra chi tit.......................17

2.8.1 Nguyn tc chung ................................................................17

2.8.2 Bin php kim tra chi tit ......................................................17

2.8.3 Ni dung kim tra chi tit .....................................................17

2.8.4 Ghi chp v lu gi h s..................................................18

Phn 3- Sa cha kt cu.............................

19

3.1 Sa cha kt cu h hng do cc nguyn nhn thuc v thit k, thi cng

v s dng cng trnh .........19

3.1.1 Nguyn tc chung .....................................................19

3.1.2 Kim tra chi tit .............................................................19

3.1.3 nh gi mc h hng v la chn bin php sa cha kt cu.................23

3.1.4 Thit k sa cha, gia cng kt cu .............................................25

3.1.5 Cc phng phap, k thut sa cha, gia cng..............25

3.1.6 Phng php gim ni lc kt cu ...........................................26

3.1.7 Phng php Tng tit din kt cu............................................26

3.1.8 K thut gia cng bc ngoi bng b tng .......................................26

3.1.9 K thut gia cng bc ngoi bng thp hnh .................................28

3.1.10 K thut gia cng dn bn thp .....................................................29

3.1.11 Gia cng bng phng php ULT cng ngoi ............................29

3.1.12 Ghi chp v lu gi h s ............................................................32

3.2 Sa cha kt cu h hng do ln nn mng ...................33

3.2.1 Nguyn tc chung.............................................................33

3.2.2 Kim tra chi tit ..............................................................33

3.2.3 Xc nh c ch v d bo tc xung cp ................36

3.2.4nh gi mc xung cp v la chn bin php khc phc.....37

3.2.5 Ghi chp v lu gi h s....................................42

3.3 Sa cha kt cu h hng do tc ng ca iu kin kh hu nng m ......45

3.3.1 Nguyn tc chung..................................................45

3.3.2 Kim tra chi tit ............................................................................45

3.3.3 Nhn bit c ch xung cp v xc nh hng khc phc.................46

3.3.4 nh gi mc xung cp v la chn bin php sa cha ....................................49

3.3.5 Mt s gii php sa cha c th....................................................51

3.3.6 Ghi chp v lu gi h s.....................................................................53

3.4 Sa cha kt cu h hng do cacbonat ho b mt b tng...54

3.4.1 Phm vi p dng.....................................................................54

3.4.2 Kim tra chi tit .........................................................................54

3.4.3 Nhn bit c ch v xc nh tc xung cp..........................58

3.4.4 Xc nh mc xung cp v la chn bin php khc phc ................59

3.4.5 Sa cha v gia cng kt cu..........................................................62

3.4.6 Ghi chp v lu gi h s...............................................................64

3.5 Sa cha kt cu h hng do tc ng ca mi trng vng bin.....65

3.5.1 Phm vi p dng.................................................................65

3.5.2 Kim tra chi tit ................................................................65

3.5.3 Nhn bit c ch v xc nh tc xung cp ........................68

3.5.4 Xc nh mc xung cp v la chn bin php khc phc........70

3.5.5 Sa cha v gia cng kt cu............................................71

3.5.6 Ghi chp v lu gi h s..................................................74

3.6 Sa cha kt cu h hng do tc ng ca mi trng xm thc cng nghip...75

3.6.1 Phm vi p dng........................................................75

3.6.2 Kim tra chi tit .....................................................75

3.6.3 Xc nh c ch v tc xung cp ca kt cu..................79

3.6.4 Xc nh mc xung cp v la chn bin php khc phc. ........82

3.6.5 Sa cha v gia cng kt cu....................................................83

3.6.6 Ghi chp v lu gi h s.................................................86

Tiu chun xy dng Vit Nam TCxdVN 318: 2004

Xut bn ln 1

Kt cu b tng v B tng ct thp-

Hng dn cng tc bo tr

Concrete and Reinforced concrete Structures

Guide to Maintenance

Phn 1- Tng qut v bo tr1.1 Nhng vn chung

1.1.1 Phm vi p dng

Tiu chun ny p dng cho cng tc bo tr cc kt cu b tng v b tng ct thp trong cng trnh dn dng v cng nghip, nhm m bo chng lun c an ton v lm vic bnh thng trong qu trnh s dng.

i vi cc kt cu thuc chuyn ngnh giao thng, thu li v cc cng trnh chuyn dng c bit khc th khi p dng Tiu chun ny cn tun th nhng quy nh k thut ring khc do cc ngnh ban hnh.

1.1.2 Ti liu vin dn

Tiu chun ny c s dng song hnh cng cc ti liu k thut sau y:

TCXD: 45:1978: Tiu chun thit k nn nh v cng trnh.

TCVN 79:1980: Thi cng v nghim thu cng tc nn mng.

TCVN 197-1985: Kim loi - Phng php th ko.

TCVN 4055: 1985: T chc thi cng.

TCVN 141: 1998: Xi mng phng php phn tch ho hc.

TCXD 162-1987: B tng nng Phng php xc nh cng bng sng bt ny.

TCXD 171-1989: B tng nng Phng php khng ph hu s dng kt hp my o siu m v sng bt ny xc nh cng chu nn.

TCXD 174: 1989: t xy dng Phng php th nghim xuyn tnh.

TCVN 5574: 1991: Kt cu b tng ct thp Tiu chun thit k.

TCVN 5573: 1991: Kt cu gch v gch ct thp.

TCVN 2683: 1991: t xy dng Phng php ly, bao gi, vn chuyn v bo qun mu.

TCVN 3105: 1993: Hn hp b tng nng v b tng nng Ly mu, ch to v bo dng mu th.

TCVN 3113: 1993: B tng nng Phng php xc nh ht nc.

TCVN 3118: 1993: B tng nng Phng php xc nh cng nn.

TCVN 5718-1993: Mi v sn BTCT trong cng trnh Xy dng. Yu cu k thut chng thm nc.

TCVN 5726: 1993: B tng nng Phng php xc nh cng lng tr v mdul n hi khi nn tnh.

TCVN 4453: 1995: Kt cu b tng v b tng ct thp ton khi. Quy phm thi cng v nghim thu.

TCVN 4085: 1995: Kt cu gch . Quy phm thi cng v nghim thu.

TCVN 2737-1995: Ti trng v tc ng- Tiu chun thit k.

TCVN 6084-1995: Bn v nh v cng trnh K hiu cho ct thp v b tng.

TCXD 205: 1998 : Mng cc Tiu chun thit k.

TCXD 226: 1999: t xy dng Phng php xuyn ng ly mu.

TCXD 239-2000: B tng nngCh dn nh gi cng b tng ca kt cu.

TCXD 240-2000: Kt cu b tng ct thpPhng php in t xc nh chiu dy lp b tng bo v, v tr v ng knh ct thp trong b tng.

TCXD 271: 2002: o ln ca cng trnh cng nghip v dn dng bng phng php thu chun hnh hc.

TCXDVN 294: 2003: Kt cu BTCT. Phng php in th kim tra kh nng ct thp b n mn.

TCXDVN 313: 2004: Kt cu b tng v BTCT. Hng dn k thut phng chng nt di tc ng kh hu nng m a phng.BS 1881, Part 120: 83 Method for determination of concrete compressive strength of concrete core.

ASTM 1084: 1997 Test method for Portland cement content of hardened hydraulic cement concrete.

ASTM C 876: 1999 Test method for half-cell potentials of uncoated reinforcing steel in concrete.

BS 1881-part 204: 88 Recommendation on use of electromagnetic covermeter.

ASTM D 5015: 95 Test method for pH of atmospheric wet deposition samples by electrometric determination.

ASTM C 1152: 1994 Test method for acid-soluble chloride in mortar and concrete.

ACI 201. 2R-2002 Guide to Durable concrete.

ACI 224.1R-2002 Cause, Evaluation and Repair of Crack in Concrete Structures.

ASTM D 3963/D 3963M-93a Standard Specification for Epoxy-Coated reinforcing Steel.

ACI 503.2-79 Standard Specification for bonding plastic concrete to hardened concrete with a multi-component system epoxy adhesive.

ASTM C 1509-90 Latex bonding agent for bonding fresh to hardened concrete.

ASTM C 856: 88 Standard practice for petrographic examination of hardened concrete.

ASTM C475: 90 Stadard test method for microscope determination of parameters of the air void system in hardened concrete.

CHu( 2.03.11- 85 (Phin bn ting Nga Matxcva 1986);1.1.3 Thut ng v nh ngha

Mt s thut ng dng trong Tiu chun ny c hiu nh sau:

Bo tr (Maintenance): Mt lot cng vic c tin hnh m bo cho kt cu lin tc gi c chc nng lm vic ca n trong sut tui th thit k.

Bin dng (deformation): Hin tng thay i hnh dng v th tch ca kt cu.Cacbonat ho (Carbonation): Tc ng sinh ra do phn ng gia Hydroxid can xi trong b tng vi kh cacbnic trong mi trng, to ra mt b mt cng do b tng b cacbonat ho v lm gim tnh kim trong phn xy ra phn ng.

Ch s cng nng di hn (Long-term performance index): Ch s xc nh kh nng cn li ca kt cu c th p ng c chc nng thit k trong sut thi gian tui th thit k.

Chc nng (Function): Yu cu m kt cu i hi phi m ng.

Co kh (Dry shringkage): S gim th tch ca b tng do b mt nc trong trng thi ng rn.

Cng nng (Performance): Kh nng (hoc hiu qu) ca kt cu m nhn cc chc nng thit k ca n.

Cng tc sa cha (Remedial action): Cng vic bo tr c thc hin vi mc ch ngn nga hoc lm hn ch qu trnh xung cp ca kt cu, gi vng hoc tng cng thm cng nng ca n, hoc gim nguy c gy hi cho ngi s dng.

Ch s cng nng (Performance index): Ch s nh lng ca cng nng kt cu.

Cng c trng (Characteristic strength): Cng c trng ca vt liu l gi tr cng c xc nh vi xc xut m bo 95% (ngha l ch c 5% cc gi tr th nghim khng tho mn).D on xung cp (Deterioration prediction): S suy on tc suy gim cng nng trong tng lai ca kt cu, da trn kt qu kim tra v cc d liu ghi chp c trong qu trnh thit k v thi cng kt cu.

D on bn lu (Durability prediction): D on v mc xung cp ca kt cu trong tng lai, da trn nhng s liu dng trong thit k.

bn lu (Durability): Mc thi gian kt cu duy tr c cc cng nng thit k.

xung cp (Degree of deterioration): suy gim cng nng hoc mc xung cp ca cng trnh do cc tc ng ca mi trng k t khi xy dng.

tin cy (Reliabilitty): Kh nng mt kt cu c th p ng y nhng yu cu cn thit trong sut tui th thit k.

an ton (Safety): Kh nng kt cu m bo khng gy thit hi cho ngi s dng v ngi vng ln cn di bt c tc ng no.

Gia cng (Strengthening): Cng vic sa cha kt cu nhm gi vng hoc nng cao thm kh nng chu ti ca kt cu n mc bng hoc cao hn mc thit k ban u.

H s hon cng (As- built documents and drawings): Ti liu a vo lu tr sau khi thi cng cng trnh, bao gm cc vn bn php l, bn v thit k, bn v hon cng, thuyt minh thit k v bin php thi cng, nht k thi cng, cc bin bn kim tra,..Khe co (Contraction joint): Khe co dn nhit m khng c chuyn dch b tng ti khe. Ti y b tng c th nt (xem khe co dn nhit m).

Khe co dn nhit m (Hot-humid deformation joint): V tr chia ct kt cu thnh cc phn nh kt cu b tng c th co n d dng theo thi tit nng m.Khe dn (Expansion joint): Khe co dn nhit m cho php chuyn dch u mt b tng ti khe (xem khe co dn nhit m).

Kh nng sa cha (Restorability/reparability): Kh nng mt kt cu c th sa cha bng k thut v kinh t khi b h hi di cc tc ng xem xt.

Kh nng s dng bnh thng (Serviceability): Kh nng kt cu p ng y yu cu s dng hoc chc nng thit k di tc ng ca cc yu t xem xt.

Kho st (Investigation): Cng vic kim tra k lng tnh trng kt cu xc lp c nhng thng s cn thit v mc h hng ca kt cu nhm tm bin php khc phc.

Kim sot h hng (Damage control): Cch tin hnh m bo yu cu trng thi gii hn c tho mn khi sa cha v phc hi kt cu.

Kim tra (Inspection): Qu trnh xem xt tnh trng kt cu v h s cng trnh nhm pht hin cc du hiu xung cp hoc xc nh cc thng s xung cp ca kt cu c bin php sa cha.

Lc c hc (Mechanical forces): Lc hoc nhm lc tp trung hoc phn b tc ng ln kt cu, hoc lc pht sinh do cc bin dng cng bc m kt cu phi chu.

Mc xung cp (Level of deterioration): Tnh trng b xung cp ca kt cu.

Phn tch (Analysis / Assessment): Phng php c chp nhn dng nh gi cc ch s cng nng hoc m t chun xc mt vn chuyn mn.

Sa cha (Repair) : Hot ng c thc hin nhm mc ch ngn nga hoc lm chm qu trnh xung cp ca kt cu, hoc lm gim nguy c gy hi cho ngi s dng.

Tc ng (Action): Lc c hc hoc tc ng ca mi trng m kt cu * (hoc b phn kt cu) phi gnh chu.

Tc ng bt thng (Accidental action): Tc ng xy ra vi xc sut rt thp, nhng c cng cao hn nhiu so vi cc tc ng thng thng khc.

Tc ng mi trng (Environment actions): Tp hp cc nh hng vt l, ho hc v sinh hc lm suy gim cht lng vt liu kt cu. S suy gim ny c th c tc ng bt li n kh nng s dng, kh nng sa cha v an ton ca kt cu.

Tc ng thay i (Variable action): Tc ng sinh ra do s chuyn ng mt vt trn kt cu, hoc do mt ti trng no lun thay i, nh ti trng i li, ti trng sng, p lc nc, p lc t, v ti trng sinh ra do thay i nhit .

Tc ng thng xuyn (Permanent action): Trng lng bn thn ca kt cu k c chi tit i km v cc c, thit b t c nh.

Tm quan trng (Importance): Mc xc nh cho kt cu ch mc phi gii quyt nhng h hng trong qu trnh suy gim cht lng, nhm gi c chc nng ca kt cu nh thit k nh.

Theo di (Monitoring): Vic ghi chp lin tc nhng d liu v s suy gim cht lng hoc cng nng ca kt cu bng nhng thit b thch hp.

Thit k theo bn (Durability design): Vic thit k nhm m bo rng kt cu c th duy tr c cc chc nng yu cu trong sut tui th thit k di cc tc ng ca mi trng.

Tnh cht bin dng (Deformability): Thut ng ch kh nng kt cu c th thay i hnh dng v kch thc.

Trng thi ng rn ca b tng (Hardened state of concrete): Trng thi b tng sau khi t c cng nht nh.

Trng thi gii hn (Limit state): Trng thi ti hn c c trng bi mt ch s cng nng. Khi vt qu ch s ny th kt cu khng cn p ng c yu cu cng nng thit k na.

Trng thi gii hn cc hn (Ultimate limit state): Trng thi gii hn ca s an ton.

Tc xung cp (Rate of deterioration): Mc xung cp ca kt cu theo mt n v thi gian.

Tui th hin cn (Remaining service life): Qung thi gian tnh t thi im kim tra ti khi kt cu c xem nh khng cn s dng c na, hoc cho ti khi n khng p ng c chc nng xc nh t khi thit k.

Tui th thit k (Design service life): Thi gian d nh m kt cu hon ton p ng c mc ch v chc nng ca n, mc d c d tnh trc yu cu bo tr, nhng khng cn thit phi sa cha ln.

Tui th s dng (Service life): di thi gian t khi xy dng xong kt cu cho ti lc n khng s dng c na v khng p ng c chc nng thit k.

Va bm (Grout): Hn hp c chy ln gm ct liu, xi mng vi nc, c hoc khng c ph gia, c thi cng bng bm p lc.

1.2. Nhng vn c bn ca bo tr

1.2.1 Yu cu chung

Mi kt cu cn c thc hin ch bo tr ng mc trong sut tui th thit k. Cc kt cu mi xy dng cn c thc hin bo tr t ngay khi a vo s dng. Cc kt cu sa cha c bt u cng tc bo tr ngay sau khi sa cha xong.

Cc kt cu ang s dng, nu cha thc hin bo tr, th cn bt u ngay cng tc bo tr.

Ch u t cn c mt chin lc tng th v bo tr cng trnh bao gm cng tc kim tra, xc nh mc v tc xung cp, nh gi tnh nguyn vn ca kt cu v thc hin cng vic sa cha nu cn.

1.2.2 Ni dung bo tr

Cng tc bo tr c thc hin vi nhng ni dung sau y:

(1) Kim tra:

Kim tra gm c cc loi hnh sau y:

(a) Kim tra ban u: L qu trnh kho st kt cu bng trc quan (nhn, g, nghe) hoc bng cc phng tin n gin v xem xt h s hon cng pht hin nhng sai st cht lng sau thi cng so vi yu cu thit k. T tin hnh khc phc ngay m bo cng trnh a vo s dng ng yu cu thit k. Kim tra ban u c tin hnh i vi cng trnh xy mi, cng trnh ang tn ti v cng trnh mi sa cha xong.

(b) Kim tra thng xuyn: L qu trnh thng ngy xem xt cng trnh, bng mt hoc bng cc phng tin n gin pht hin kp thi du hiu xung cp. Kim tra thng xuyn l bt buc i vi mi cng trnh.

(c) Kim tra nh k: L qu trnh kho st cng trnh theo chu k pht hin cc du hiu xung cp cn khc phc sm.

Kim tra nh k c thc hin vi mi cng trnh trong chu k kim tra c ch cng trnh quy nh tu theo tm quan trng, tui th thit k v iu kin mi trng lm vic ca cng trnh.

(d) Kim tra bt thng: L qu trnh kho st nh gi cng trnh khi c h hng t xut (nh cng trnh b h hng do gi bo, l lt, ng t, va p, chy, vv..). Kim tra bt thng thng thng i lin vi kim tra chi tit.

(e) Theo di: L qu trnh ghi chp thng xuyn v tnh trng kt cu bng h thng theo di t sn t lc thi cng. H thng theo di thng c t cho cc cng trnh thuc nhm bo tr A v B (bng 1).

(f) Kim tra chi tit: L qu trnh kho st, nh gi mc h hng cng trnh nhm p ng yu cu ca cc loi hnh kim tra trn. Kim tra chi tit cn i lin vi vic xc nh c ch xung cp, nh gi mc xung cp v i n gii php sa cha c th.

Chi tit v cc loi hnh kim tra xem Phn 2.

Quan h gia cc qu trnh kim tra v sa cha c th hin trn s hnh 1.1.

(2) Phn tch c ch xung cp: Trn c s cc s liu kim tra, cn xc nh xem xung cp ang xy ra theo c ch no. T xc nh hng gii quyt khc phc.

(3) nh gi mc v tc xung cp: Sau khi phn tch c c ch xung cp th nh gi xem mc v tc xung cp n u v yu cu i hi phi sa cha n mc no, hoc c th s phi ph d. C s nh gi mc xung cp l cc cng nng hin c ca kt cu.

(4) Xc nh gii php sa cha: Xut pht t mc yu cu phi sa cha thit k gii php sa cha c th.

(5) Sa cha: Bao gm qu trnh thc thi thit k v thi cng sa cha hoc gia cng kt cu.

Tu theo mc , yu cu ca cng tc bo tr, ch cng trnh c th t thc hin nhng ni dung bo tr nu trn hoc thu mt n v chuyn ngnh thit k hoc thi cng thc hin.

1.2.3 Phn loi bo tr

Cng tc bo tr c phn theo cc nhm A, B, C, D tu theo tm quan trng cu kt cu, c im kt cu, tui th thit k, iu kin mi trng, mc tc ng ti xung quanh, d bo tr v gi bo tr. Cc nhm bo tr v yu cu bo tr tng ng c quy nh trong bng 1.1.Bng 1.1. Phn loi bo tr theo cc nhm

N0Nhm bo trLoi cng trnhYu cu thc hin bo tr

1Nhm A-

Bo tr phng nga-Cng trnh c bit quan trng, c lin quan ti an ton quc gia, phng chng chy n v mi trng;

-Cng trnh thng xuyn c rt nhiu ngi lm vic hoc qua li

-Cng trnh khng c iu kin d sa cha

-Cng trnh c tui th thit k n 100 nm hoc lu hn-Thc hin tt c cc ni dung bo tr mc 1.2.2.

-t thit b theo di cng trnh lu di.

-Thc hin cc bin php phng nga ngay t giai on thit k, thi cng (nh bo v b mt, t catt bo v).

2Nhm B-

Bo tr thng thngCc cng trnh dn dng v cng nghip thng thng, c tui th thit k di 100 nm v c th sa cha khi cn-Thc hin tt c cc ni dung bo tr mc 1.2.2.

-C th t h thng thit b theo di lu di.

-Kim tra ban u, thng xuyn, nh k c thc hin ch yu bng mt v cc phng tin n gin.

3Nhm C-

Bo tr quan stCng trnh tm, c nin hn s dng di 20 nm-Bo tr ch yu bng quan st thng xuyn. Khng cn kho st chi tit. Khi cng trnh c du hiu xung cp th hoc l tin hnh sa cha n gin, hoc l ph d.

4Nhm D-

Bo tr khng quan stCng trnh dn khoan ngoi khi, cng trnh ngm di t, cng trnh di nc-Khng tin hnh kim tra thng xuyn v nh k i vi cc chi tit khut. Kim tra chi tit v kim tra t xut c tin hnh khi du hiu h hng cho thy cn phi sa cha.

-C th thc hin bin php phng nga ngay trong giai on thit k v thi cng (nh bo v b mt, t catt bo v)

Hnh 1.1. Quan h cc qu trnh kim tra v sa cha kt cu

1.2.4 Cc dng h hng ca kt cu

(1) Tiu chun ny xem xt cc dng h hng thng thng sau y ca kt cu:

(a) H hng do sai st thuc v thit k, thi cng, s dng cng trnh;

(b)H hng do nguyn nhn ln nn mng;

(c) H hng do tc ng ca cc yu t kh hu nng m;

(d) H hng do cabonat ho b tng;

(e) H hng do tc ng ca mi trng vng bin;

(f) H hng do tc ng ca mi trng xm thc cng nghip;

Vic nhn bit cc loi hnh h hng trn c ch dn phn 3.

(2) T mi loi hnh h hng nhn bit c, ch cng trnh v ngi thit kt cn c chng trnh c th cho cng tc bo tr, bao gm t khu kim tra, nh gi mc h hng n vic sa cha, gia cng, nng cp hoc ph d cng trnh.

1.2.5 Kim tra cng nng ca kt cu trong qu trnh bo tr

(1) Cng nng ca kt cu cn c nh gi li trc v sau khi sa cha. Cc cng nng sau y cn c nh gi:

(a) an ton (kh nng chu ti);

(b)Kh nng lm vic bnh thng;

Vic nh gi cng nng c thc hin thng qua cc ch s cng nng yu cu (Pyc) v ch s cng nng thc t m kt cu t c (Ptt). Tu theo loi hnh v mc h hng ca kt cu, c th xc nh mt hoc mt s ch s cng nng cho mi loi hnh cng nng kim tra.

(2) Kt cu c coi l m bo cng nng khi:

Ptt ( Pyc hoc Pyc ( Ptt , tu theo ch s cng nng c th.

Trong :

Ptt l ch s cng nng thc t t c, xc nh theo thc t kho st kt cu hoc theo gi tr tnh ton;

Pyc: Ch s cng nng yu cu, xc nh theo cc tiu chun quy phm hin hnh hoc theo yu cu ca ngi thit k hay ch cng trnh.

(3) Cc ch s cng nng cn nh gi c ch r trong bng 1.2.

Bng 1.2. Cc ch s cng nng cn nh gi trc v sau khi sa cha kt cu

Cng nng kim traCh s cng nngLoi hnh kt cu

p dng

an ton (kh nng chu ti)Mmen un;

Lc ct;

Lc dc.

Lc xon;

Lc gy sp hoc mt n nh kt cuMi kt cu vi cc dng h hng khc nhau

Kh nng lm vic bnh thng+Theo chc nng kt cu:

-Chng thm (Lng nc thm qua kt cu, mt thm m);

-Cch nhit (Mc truyn nhit qua kt cu);

-Chng chy (Mc chu la ca k/c khi c chy);

-Chng n; bi (Mc n, bi);

-M quan bn ngoi (Mt ru mc);

-Mi (do ru mc).-Kt cu c cc yu cu theo chc nng kim tra;

-Kt cu c yu cu thm m

+Theo tin nghi cho ngi s dng:

-Nghing lch, vng, ln.

-Vt nt (Mt v b rng vt nt).

-Chn rungMi kt cu vi cc dng h hng khc nhau.

+Theo tc ng xu n mi trng xung quanh:

-Kh nng bong ri lp bo v ct thp;

-Mc tc ng xu n mi trng;

-nh hng n cng trnh ln cn.Cc kt cu c nguy c n mn, han r ct thp.

Kt cu thng xuyn tip xc vi cht thi.

Kt cu b ln.

i vi cc kt cu chu tc ng n mn hoc tc ng ca kh hu nng m th ngoi kim tra cng nng cn cn phi kim tra kh nng kt cu gi c bn lu theo yu cu thit k. C th, cc yu t sau y cn phi di mc cho php.

Nng ion Cl- hoc ho cht thm thu;

Chiu dy mc thm ion Cl- hoc ho cht;

Chiu dy cacbonat; pH;

B rng vt nt;

Mc r ct thp;

rng b tng;

Tn tht cng hoc trong lng b tng.1.2.6 Qun l k thut cng tc bo tr

(1) Cn phi c mt chin lc bo tr ngay t khi quyt nh u t xy dng cng trnh. Chin lc ny cn c son tho da trn cc vn bn php quy hin hnh do Nh nc Vit Nam, B Xy dng ban hnh v cc tiu chun k thut cn thit khc.

(2) Sau khi xy dng xong cng trnh, cn tin hnh ngay vic kim tra ban u pht hin cc du hiu khuyt tt lm nh hng xu n cng nng kt cu. Cc khuyt tt ny cn c khc phc ngay trc khi a cng trnh vo s dng.

(3) Trong sut thi gian lm vic ca cng trnh, cng tc bo tr cn c duy tr theo ni dung nu cc iu 1.2.2, 1.2.3, v 1.2.4. Trong trng hp pht hin thy kt cu b h hng n mc phi sa cha th cn tin hnh ngay cng tc kim tra, nh gi mc h hng v ra bin php sa cha.

(4) Vic kim tra, xc nh c ch xung cp, nh gi mc h hng v ra gii php sa cha kt cu phi do cc n v v chuyn gia chuyn ngnh c nng lc ph hp thc hin. Cc gii php sa cha cn c xc nh trn c s cc s liu kim tra trc v c s dng cc bn v thit k, bn v hon cng, cc kt qu kim tra cht lng, vt liu s dng, cc bin bn v s nht k thi cng ca cng trnh. Vic thi cng sa cha, gia cng, nng cp, hoc ph d kt cu b h hng cn phi c cc n v thi cng c nng lc chuyn mn ph hp thc hin.

(5) Mi din bin ca cng tc bo tr cn c ghi chp v lu gi s dng lu di. Ch cng trnh s lu gi cc ghi chp ny cng vi cc bn v v cc ti liu k thut khc lin quan n vic bo tr.

Phn 2. Cng tc kim tra2.1 Nguyn tc chung

Kim tra l cng vic c thc hin i vi mi cng trnh nhm pht hin kp thi s xung cp hoc thay i cng nng kt cu.

Vic kim tra cn c duy tr trong sut thi gian s dng cng trnh.

2.2 Tay ngh v cng c kim tra

Vic kim tra phi do n v v cc c nhn c trnh chuyn mn ph hp thc hin. Thng thng ch cng trnh c th mi n v v chuyn gia t vn thit k v gim st cht lng thc hin cng tc kim tra. Cng c kim tra c th l bng trc quan (nhn nghe), hoc bng nhng cng c thng thng nh thc mt, ba g, knh phng i, vv.. Khi cn c th dng cc thit b nh my kinh v, thit b th nghim khng ph hoi hoc cc thit b th nghim trong phng khc.

Di y l hng dn c th cho mi loi hnh kim tra:

2.3 Kim tra ban u

2.3.1 Nguyn tc chung

(1) Kim tra ban u c thc hin ngay sau khi cng trnh c thi cng xong v bt u a vo s dng. i vi cng trnh sa cha v gia cng th kim tra ban u c thc hin ngay sau khi sa ch v gia cng xong.

i vi nhng cng trnh ang tn ti m cha c kim tra ban u th bt k ln kim tra u tin no cng c th coi l kim tra ban u.

(2) Yu cu ca kim tra ban u l thit lp cc s liu o u tin ca kt cu, pht hin kp thi nhng sai st ban u ca kt cu v khc phc ngay a kt cu vo s dng. Thng qua kim tra ban u suy on kh nng c th xung cp cng trnh theo tui th thit k d kin.

(3) Kim tra ban u do ch u t cng vi cc n v thit k, thi cng v gim st cht lng thc hin.

2.3.2 Bin php kim tra ban u

Kim tra ban u c tin hnh trn ton b kt cu cng trnh hoc mt b phn ca kt cu.

Phng php kim tra ch yu l bng trc quan, kt hp vi xem xt cc bn v thit k, bn v hon cng v h s thi cng (s nht k cng trnh, cc bin bn kim tra c).

2.3.3 Ni dung kim tra ban u

Kim tra ban u gm c nhng cng vic sau y:

(1) Kho st kt cu thu thp s liu v nhng vn sau y:

(a)Sai lch hnh hc ca kt cu;

(b) nghing, ln, bin dng ca kt cu;

(c)Xut hin vt nt;

(d)Tnh trng bong rp;

(e)Tnh trng r ct thp;

(f)Bin mu mt ngoi;

(g)Cht lng b tng;

(h)Cc khuyt tt nhn thy;

(i)S m bo v cng nng s dng (chng thm, cch m, cch nhit vv...).

(j)Tnh trng h thng theo di lu di (nu c). S liu o ca h thng ti thi im kim tra ban u.(2) Xem xt h s hon cng nh gi cht lng phn khut ca kt cu (bn v thit k, bn v hon cng, s nht k cng trnh, cc bin bn kim tra).

(3) Tin hnh th nghim b sung nu cn nhn bit r hn tnh trng cng trnh i vi cng trnh ang tn ti, nay mi kim tra ln u.

(4) X l cc khuyt tt pht hin ra. Trng hp nghi ng c sai st quan trng th tin hnh thm kim tra chi tit v ra bin php x l.

(5) Tin hnh vn hnh h thng theo di ghi s o ban u i vi cc kt cu c gn cc h thng theo di lu di.

(6) Suy on kh nng xung cp kt cu theo tui th cng trnh.

Trn c s cc s liu kho st v sau khi nhng sai st kt cu c khc phc, cn suy on kh nng s xut hin cc khuyt tt kt cu, kh nng bn mi trng (i vi mi trng xm thc v mi trng kh hu nng m), kh nng c th nghing ln tip theo, v kh nng suy gim cng nng.

Tu theo tnh cht v iu kin mi trng lm vic ca cng trnh, ngi thc hin kim tra ban u c th t trng tm cng tc kim tra vo nhng yu t c nh hng quan trng ti bn lu ca cng trnh.

Mc tiu cui cng ca suy on l nh gi xem kh nng kt cu c th dm bo tui th thit k trong iu kin s dng bnh thng hay khng, ng thi xc nh gii php m bo bn lu cng trnh.2.3.4 Ghi chp v lu gi h s

Ton b kt qu kho st, nh gi cht lng kt cu, suy on kh nng lm vic ca kt cu, s o ban u ca h thng theo di lu di cn c ghi chp y v lu gi lu di cng vi h s hon cng ca cng trnh.

Ch cng trnh cn lu gi h s ny s dng cho nhng ln kim tra tip theo.

2.4 Kim tra thng xuyn

2.4.1 Nguyn tc chung

(1) Kim tra thng xuyn c tin hnh nhm theo di, gim st kt cu thng ngy sau kim tra ban u. Ch cng trnh cn c lc lng chuyn trch thng xuyn quan tm n vic kim tra thng xuyn.

(2) Kim tra thng xuyn c thc hin trn ton b kt cu nhng ch c th quan st c. Mc ch l nm c kp thi tnh trng lm vic ca kt cu, nhng s c h hng c th xy ra (c bit l nhng v tr xung yu, quan trng) sm c bin php khc phc, trnh tnh trng h hng ko di dn n ngy cng trm trng hn.

2.4.2 Ni dung kim tra thng xuyn

Kim tra thng xuyn gm cc cng vic sau y:

(1) Tin hnh quan st kt cu thng ngy bng mt, khi c nghi ng th dng bin php g nghe v suy on. Ngi tin hnh kim tra thng xuyn phi c trnh chuyn ngnh xy dng v c giao trch nhim r rng.

(2) Thng ngy quan tm xem xt nhng v tr sau y ca kt cu pht hin sm nhng du hiu xung cp:

(a)V tr c mmen un v lc ct ln; v tr tp trung ng sut

(b)V tr khe co dn;

(c)Ch lin kt cc phn t ca kt cu;

(d)V tr c ngun nc thm, ngun nhit, ngun n, ngun bi;

(e)Nhng ch chu tc ng trc tip ca bc x mt tri;

(f) V tr c tip xc vi mi trng xm thc.

(3) Pht hin nhng vn sau y khi tin hnh kim tra thng xuyn:

(a)S nghing ln,

(b)Bin dng hnh hc ca kt cu;

(c)Xut hin vt nt; st m, gim yu tit din.

(d)Xut hin bong rp;

(e)Xut hin thm;

(f) R ct thp;

(g)Bin mu mt ngoi;

(h)S suy gim cng nng (chng thm, cch m, cch nhit..)

(i)Tnh trng h thng theo di lu di (nu c).

Ch thch: i vi cc kt cu lm vic trong mi trng xm thc th cn thng xuyn quan tm ti du hiu n mn b tng v ct thp.

(4) X l kt qu kim tra:

(a)Trng hp pht hin c s c, h hng nh th c bin php khc phc ngay;

(b)Trng hp pht hin c s c, h hng nng bt thng th t chc kim tra chi tit ti ch h hng v ra gii pht x l kp thi. Trong qu trnh ra gii php x l cn phi nghin cu tnh trng kt cu trong h s kim tra ban u.2.4.3 Ghi chp v lu gi h s

Nhng iu sau y cn c ghi chp y :

(a)Nhng s c hoc h hng pht hin, v tr xy ra cc s liu o nu c;

(b)Bin php khc phc v kt qu khc phc h hng xy ra;

(c)S liu kim tra chi tit nu c;

(d)Gii php v kt qu sa cha sau kim tra chi tit.

(e)Tnh trng kt cu sau khi khc phc h hng.

(f)Nhng ti liu ghi chp nu trn cn c ch cng trnh lu gi lu di cng vi h s kim tra ban u s dng cho nhng ln kim tra sau.

2.5 Kim tra nh k

2.5.1 Nguyn tc chung

(1) Kim tra nh k c tin hnh i vi mi kt cu b tng ct thp.

(2) Kim tra nh k nhm pht hin kp thi nhng du hiu h hng ca kt cu trong qu trnh s dng m vic kim tra ban u v kim tra thng xuyn kh nhn bit c. T c bin php x l sm nhm duy tr tui th cng trnh.

(3) Ch cng trnh cn cng vi ngi thit k xc nh chu k kim tra nh k trc khi a kt cu vo s dng. Quy m kim tra ca mi k s ty theo trng thi c th ca kt cu v iu kin ti chnh quyt nh.

2.5.2 Bin php kim tra nh k

(1) Kim tra nh k c tin hnh trn ton b kt cu. i vi cc kt cu qu ln th c th phn khu kim tra nh k, mi khu vc kim tra mt k.

(2) Ch cng trnh c th mi cc n v v chuyn gia t vn c chuyn mn thuc chuyn ngnh xy dng v c tay ngh thch hp thc hin vic kim tra nh k.

(3) u tin kt cu c kho st trc quan bng nhn v g nghe. Khi nghi ng c h hng hoc suy thoi cht lng th c th s dng thit b th nghim khng ph hy hoc khoan li b tng kim tra.

2.5.3 Quy nh v chu k kim tra

Chu k kim tra nh k kt cu c quy nh nh sau:

(a)Cng trnh c bit quan trng: 2 (3 nm;

(b)Cng trnh thng xuyn c rt ng ngi lm vic hoc qua li: 3 (5 nm

(c)Cng trnh cng nghip v dn dng khc: 5 (10 nm;

(d) Cng trnh thng xuyn chu n mn kh hu bin v n mn ho cht: 1(2 nm.

2.5.4 Ni dung kim tra nh k

Kim tra nh k c tin hnh theo trnh t ni dung ging nh ca kim tra ban u nu trong mc 2.3.3.

2.5.5 Ghi chp v lu gi h s

Ton b kt qu thc hin kim tra nh k cn ghi chp v lu gi theo ch dn mc 2.3.4.

2.6 Kim tra bt thng

2.6.1 Nguyn tc chung

(1) Kim tra bt thng c tin hnh khi kt cu c du hiu h hng do tc ng t ngt ca cc yu t nh bo, l lt, ng t, trt l t, va chm vi tu xe, chy, v.v..

(2) Yu cu ca kim tra bt thng l nm bt c hin trng h hng ca kt cu, v a ra kt lun v yu cu sa cha.

(3) Ch cng trnh c th t kim tra bt thng hoc thu mt n v hoc chuyn gia c nng lc ph hp thc hin.

2.6.2 Bin php kim tra bt thng

(1) Kim tra bt thng c thc hin trn ton b hoc mt b phn kt cu ty theo quy m h hng xy ra v yu cu sa cha ca ch cng trnh.

(2) Kim tra bt thng c thc hin ch yu bng quan st trc quan, g nghe. Khi cn c th dng cc cng c n gin nh thc mt, qu di, v.v..

(3) Ngi thc hin kim tra bt thng cn a ra c kt lun c cn kim tra chi tit hay khng. Nu khng th ra ngay gii php sa cha phc hi kt cu. Nu cn th tin hnh kim tra chi tit v ra gii php sa cha.

2.6.3 Ni dung kim tra bt thng

Kim tra bt thng bao gm nhng cng vic sau y:(1)Kho st bng trc quan, g nghe v dng mt s cng c n gin nhn bit ban u v tnh trng h hng ca kt cu. Cc h hng sau y cn c nhn bit:

(a) Sai lch hnh hc kt cu

(b) Mc nghing ln

(c) Mc nt, gy

(d) Cc khuyt tt nhn thy khc

(e) Tnh trng h thng theo di lu di (nu c).

(2) Phn tch cc s liu phi kho st i n kt lun c tin hnh kim tra chi tit hay khng, quy m kim tra chi tit. Nu cn kim tra chi tit th thc hin theo ch dn mc 2.6. Nu khng th ra gii php sa cha phc hi kt cu kp thi.

i vi nhng h hng c nguy c gy nguy him cho ngi v cng trnh xung quanh th phi c bin php x l khn cp trc khi tin hnh kim tra chi tit v ra gii php sa cha.

(3)Thc hin sa cha

Qu trnh sa cha kt cu b h hng bt thng c thc hin theo ch dn mc 2.6.3(5).2.6.4 Ghi chp v lu gi h s

Mi din bin cng vic ghi trong mc 2.6.3 cn c ghi chp v lu gi.

H s lu tr gm c: Kt qu kho st, phn tch nh gi, thuyt minh gii php sa cha hoc gia cng, nht k thi cng, cc bin bn kim tra, cc bn v. Cc ti liu ny cn c ch cng trnh lu gi lu di cng vi h s ca cc t kim tra trc y.

2.7 Theo di

2.7.1 Nguyn tc chung(1) H thng theo di cn c t cho nhng cng trnh quan trng, c ngha ln v kinh t, chnh tr v an ton sinh mng i vi nhiu ngi (bng 1.1).

(2) Ch cng trnh v ngi thit k cn xc nh mc yu cu trang b h thng theo di, la chn thit b, thit k lp t v hng dn thi cng.

(3) Trc khi a cng trnh vo hot ng, cn phi vn hnh th h thng theo di chng t rng h thng ang hot ng bnh thng. Ln o u tin c tin hnh cng sm cng tt, c th trc thi gian kim tra ban u.

(4) Ch cng trnh cn c lc lng thng xuyn kim tra hot ng ca h thng, theo di v qun l cc s liu o.

2.7.2 t h thng theo di

(1) H thng theo di c t nhng v tr k cu d nhy cm vi nhng vn m ngi thit k yu cu. Nhng v tr cn t cc chi tit ca h thng theo di c th xc nh theo mc 2.4.2 (2).

(2) Cc chi tit ca h thng theo di c t t trong giai on thi cng v phi c bo qun khng b h hng do tc ng c hc v thi tit.

2.7.3 Vn hnh h thng theo di

(1) H thng theo di c t ng ghi chp s liu o theo chu k m ngi thit k v ch cng trnh yu cu. S h tr ca cn b chuyn mn trong qu trnh vn hnh h thng v o c l rt quan trng.

(2) H thng theo di cn c thng xuyn kim tra m bo lun hot ng bnh thng. Cc s liu o ca h thng cn c x l kp thi cng vi cc s liu kim tra thng xuyn v kim tra nh k c nhng tc ng thch hp trc khi s xung cp ca kt cu tr nn nguy hi n s an ton v cng nng ca kt cu.

2.7.4 Lu gi s liu o

S liu o ca h thng sau khi c x l cn c lu gi lu di.

Ch cng trnh lu gi cc s liu o ny cng vi cc s liu kim tra khc.

2.8 Yu cu i vi Kim tra chi tit

2.8.1 Nguyn tc chung

(1)Kim tra chi tit c thc hin sau khi qua cc kim tra ban u, kim tra thng xuyn, kim tra nh k, kim tra bt thng thy l c yu cu cn phi kim tra k kt cu nh gi mc xung cp v ra gii php sa cha.

(2) Ch cng trnh c th t thc hin hoc thu cc n v v c nhn chuyn gia c nng lc ph hp thc hin kim tra chi tit.

2.8.2 Bin php kim tra chi tit

(1)Kim tra chi tit c tin hnh trn ton b kt cu hoc mt b phn kt cu ty theo quy m h hng ca kt cu v mc yu cu phi kim tra.

Ngi kim tra cn nhn bit trc c im ni bt ca xung cp c hng trng tm cho vic kim tra chi tit.

(2) Kim tra chi tit c thc hin bng cc thit b th nghim chuyn dng nh gi lng ha cht lng vt liu s dng v mc xung cp ca kt cu. Phng php th nghim cn c thc hin theo cc tiu chun v quy phm hin hnh.

(3) Ngi thc hin kim tra chi tit phi c phng n thc hin bao gm quy m kim tra, mc kt qu kim tra cn t, thi gian v kinh ph thc hin. Phng n ny phi c ch cng trnh chp nhn trc khi thc hin.2.8.3. Ni dung kim tra chi tit

Kim tra chi tit cn c nhng ni dung sau y:

(1) Kho st chi tit ton b hoc b phn h hng ca kt cu: Yu cu ca kho st l phi thu c cc s liu lng ha v tnh trng h hng ca kt cu. C th l lng ha bng s liu v bng nh nhng vn sau y:

(a)Sai lch hnh hc kt cu v chi tit kt cu;

(b)Mc bin dng kt cu;

(c)Mc nghing, ln;

(d)Vt nt (mt , chiu rng, chiu di, chiu su v hng vt nt);

(e)Vt gy (c im, v tr, mc nguy him)

(f) n mn ct thp (mt r, mc r, tn tht tit din ct thp);

(g)n mn b tng (n mn xm thc, n mn ccbnt, mc n mn, chiu su xm thc vo kt cu, nhim ha cht, v.v.);

(h)Cht lng b tng (cng , c chc, bong rp);

(i) Bin mu mt ngoi;

(j) Cc khuyt tt nhn thy;

(k)S m bo cng nng kt cu (chng thm, cch m, cch nhit, v.v.);

(l)Tnh trng lm vic ca h thng theo di lu di (nu c). S liu o ca h thng ti thi im kim tra chi tit.

CH thch:Cc s liu lng ha nu trn u phi c xc nh trn c s cc tiu chun phng php th hin hnh trong nc hoc quc t.

(2) Phn tch c ch xung cp ca kt cu: Trn c s cc s liu kho st nu trn v cc kt qu kim tra h s lu tr cng trnh, cn phn tch, xc nh c ch to nn mi loi h hng. C th quy np mt s dng c ch in hnh sau y:

(a) Nt gy kt cu: Do vt ti; bin dng nhit m; ln; cht lng b tng.

(b) Suy gim cng b tng: Do c chc b tng; bo dng b tng v tc ng mi trng; xm thc.

(c) Bin dng hnh hc kt cu:Do vt ti; tc ng mi trng; cng kt cu.

(d) R ct thp:Do n mn mi trng xm thc; cacbnat ha b mt b tng; nt b tng; thm nc.

(e) Bin mu b mt:Do tc ng mi trng.

(f) Thm nc:Do cht b tng, nt kt cu, mi ni.

(3) nh gi mc xung cp ca kt cu: Trn c s cc s liu kim tra v c ch xung cp phn tch, cn nh gi xem kt cu c cn sa cha hay khng, v sa cha n mc no.

C s nh gi mc xung cp l cc cng nng ca kt cu c xem xt, theo ch dn mc 1.2.6.

(4) La chn gii php sa cha hoc gia cng: Gii php sa cha hoc gia cng cn c la chn trn c s c ch xung cp c phn tch sng t. Gii php sa cha hoc gia cng ra phi t c yu cu l khi phc c bng hoc cao hn cng nng ban u ca kt cu v ngn nga vic tip tc hnh thnh c ch xung cp sau khi sa cha.

Quy m sa cha ph thuc vo tm quan trng ca kt cu, tui th cn li ca cng trnh, kh nng ti chnh v yu cu ca ch cng trnh.

Chi tit v phng php la chn gii php sa cha xem hng dn Phn 3.

(5) Thc hin sa cha hoc gia cng:

(a)Ch cng trnh c th t thc hin sa cha, gia cng hoc chn mt n v c nng lc ph hp thc hin.

(b)n v thc hin sa cha hoc gia cng cn c k hoch ch ng v vt t, nhn lc, tin v bin php thi cng, gam st cht lng trc khi bt u thi cng.

(c)Vic sa cha hoc gia cng phi m bo nh hng t nht n mi trng xung quanh v n ngi s dng. Nhng th nghim kim tra cht lng cn thit phi c thc hin trong qu trnh thi cng.

(d)Mi din bin ca cng tc sa cha hoc gia cng phi c ghi vo s nht k thi cng v lu gi lu di.2.8.4 Ghi chp v lu gi h s

(1) Mi din bin ca cng tc kim tra chi tit nu trong mc 2.6.3 u phi c ghi chp y di dng bin bn, s nht k, bn v lu gi lu di.

(2) Ch cng trnh lu gi h s kim tra chi tit bao gm: kt qu kho st, phn tch nh gi, thuyt minh gii php sa cha hoc gia cng, nht k thi cng, cc bn v, cc bin bn kim tra. Cc h s ny cn c lu gi lu di cng vi cc h s ca cc t kim tra trc y.Phn 3- Sa cha kt cuPhn ny hng dn cng tc sa cha kt cu theo quy trnh nu Phn 1 v 2.

3.1 Sa cha kt cu h hng do cc nguyn nhn thuc v thit k,

thi cng v s dng cng trnh

3.1.1 Nguyn tc chung

Mc ny hng dn phng php kim tra chi tit, xc nh c ch v mc xung cp, sa cha v gia cng cc kt cu btng ct thp b h hng do cc nguyn nhn thuc v thit k, thi cng v s dng cng trnh, trong ch yu cp ti cc vn nh: ti trng tc ng, kh nng chu lc v kh nng s dng bnh thng ca kt cu t khi xy dng v trong sut qu trnh khai thc. Trc khi sa cha v gia cng kt cu cn tin hnh kim tra chi tit, nh gi mc v phn tch c ch/nguyn nhn gy h hng cng trnh. Ti trng y ch gii hn trong cc tc ng thng thng tc dng ln cng trnh.

C ba loi h hng cng trnh do cc nguyn nhn thuc v kt cu v ti trng bao gm:

(1) Nt kt cu;

(2) Bin dng vt qu gii hn cho php ca cng trnh do cng ca kt cu hoc do cng ngh thi cng khng m bo;

(3) Kh nng chu lc ca kt cu hoc cu kin khng , tuy cha gy ra nt nghim trng hay ph hoi kt cu, nhng li khuyt tt bn trong cn phi gia cng.

H hng v sa cha h hng cng trnh do ln nn mng c trnh by trong mc 3.2.

3.1.2 Kim tra chi tit

Kim tra chi tit c tin hnh nhm xc nh c ch v mc h hng kt cu trc khi a ra gii php sa cha hoc gia cng.

Kim tra chi tit c tin hnh vi nhng cng vic sau y:

3.1.2.1 Kho st hin trng nt kt cu

(1) Gii hn b rng khe nt: Gii hn b rng khe nt trong kt cu btng l mt trong cc ch s cng nng quan trng nh gi kh nng s dng bnh thng ca kt cu. Gii hn b rng khe nt c qui nh trong Tiu chun kt cu btng ct thp hin hnh TCVN 5574:1991, tu thuc vo iu kin lm vic ca kt cu v loi ct thp s dng.

(2) Kho st nt: cn lm sng t nhng vn sau y:

(a) V tr, v c trng phn b vt nt;

(b) Phng v hnh dng vt nt;

(c) Kch thc vt nt (b rng, chiu di v su);

(d) Thi im xut hin vt nt;

(e) S pht trin ca vt nt theo thi gian; v

(f) Cc c trng khc nh b tng b bong rp, b nn v v.v.

Vic kho st nt c th phi tin hnh trong thi gian tng i lu, theo chu k xc nh xem hin tng nt ca kt cu n nh hay cn ang pht trin.

(3) c trng v c ch hnh thnh vt nt do ti trng:

(a) V tr v c trng phn b vt nt: Cc vt nt thng xut hin cc vng d on c ng sut ko ln nht trong kt cu/cu kin.

i vi dm n gin v dm lin tc, cc vt nt vung gc vi trc dm thng pht trin phn di ca gia nhp hoc phn trn gn gi . Cc vt nt xin gn gi hoc gn im t ti trng tp trung. Trong mt s trng hp, c th c cc vt nt xut hin vng chu nn gn ni c m-men un ln nht ca dm. Mt s dng vt nt c th hin hnh 3.1.1.

Hnh 3.1.1 Vt nt do un

Hnh 3.1.2: Vt nt do ct

Hnh 3.1.3: Vt nt do un ct (dm lin tc)

Hnh 3.1.4: Vt nt do nn (ct, qu ti)

(b) Hnh dng vt nt: Vt nt do ko gy ra thng vung gc vi ng sut php, nh chiu vt nt chu ko ca dm chu un lun vung gc vi trc dm, pha di rng, pha trn nh.

Vt nt do ct gn gi, thng xin 450 pht trin ln pha trn v hng vo gia dm (Hnh 3.1.2 v 3.1.3).

Vt nt do lc nn gy ra thng song song vi chiu ca lc nn, phn ln hnh dng ca vt nt l hai u nh, gia rng (Hnh 3.1.4).

Vt nt do m-men xon gy ra c hnh xon c xin, b rng ca khe nt thng khng thay i ln.

Vt nt do xung lc (lc va p) thng pht trin xin 450 vi chiu ca xung lc.

Vt nt do ln nn mng: i vi kt cu b tng ct thp, cc vt nt do bin dng nn thng xut hin tp trung khu vc c cong tng i ln ca ng cong ln. Chiu ca vt nt vung gc vi chiu ca ng sut ko chnh do bin dng nn sinh ra. i vi dm v sn, cc vt nt do ln thng l cc vt nt thng gc vi trc dm v sn. Khi b ln lch hay ln nh hng ca cng trnh ln cn, thng xut hin cc vt nt xin dm (gn lin kt dm-ct), cc vt nt cho gc 450 (trn mt bng sn) cc gc sn.

(c) Kch thc ca vt nt: Vt nt xut hin trong giai on s dng bnh thng ca kt cu ni chung b rng khe nt khng ln. B rng khe nt gim dn t mt ngoi kt cu vo bn trong (chiu su) ca btng.

Khi kt cu vt ti nghim trng hoc t ti trng thi gii hn th b rng khe nt thng tng i ln, vt qu gii hn qui nh trong TCVN 5574:1991.

Tuy nhin, i vi cc vt nt do lc nn dc trc sinh ra, b rng khe nt khng ln, c th nh hn gii hn qui nh trong TCVN 5574:1991, nhng vn l du hiu ca kt cu ti gn trng thi gii hn, cn phi ht sc ch khi kho st v nh gi.

(d) Thi im xut hin vt nt: Vt nt thng xut hin khi ti trng t ngt tng ln, v d: khi tho d cp-pha, lp t thit b, khi cho kt cu chu ti v chu vt ti. Trong kt cu c th xut hin cc vt nt khi b ln khng u vt qua gii hn cho php. Thi im xut hin vt nt khng nht thit l thi im sinh ra nt.

(e) S pht trin vt nt: Vt nt thng pht trin theo s gia tng ca ti trng v thi gian tc ng ko di ca ti trng cng nh s gia tng ln.

(4) Du hiu nt nguy him: Cc du hiu sau l cc du hiu nt nguy him nh hng nghim trng n an ton ca kt cu nu khng c cc bin php x l thch hp:

(a) i vi dm: gia nhp dm: pha di xut hin cc vt nt theo phng vung gc vi trc dm, pht trin ti hn 2/3 chiu cao dm; hoc pha trn (vng chu nn) xut hin nhiu vt nt song song vi trc dm nhn r bng mt thng, lp btng bo v b bong rp, mt di c thm cc vt nt ng (theo phng vung gc vi trc dm).

Gn gi dm xut hin cc vt nt xin nhn r, y l cc vt nt rt nguy him. Khi vt nt ko di ti trn 1/3 chiu cao dm, hoc khi ng thi vi cc vt nt xin, vng chu nn cn xut hin cc vt nt song song vi trc dm th c th lm cho dm ph hoi v nt gy. Trong trng hp ct ai b tr qu t, t s gia khong cch t im t ti trng tp trung n gi ta v chiu cao hu dng ca dm ln hn 3, nu xut hin cc vt nt xin, ng sut trong ct ai s tng nhanh t ti cng chy, vt nt xin pht trin rt nhanh lm dm nt thnh 2 phn v b ph hoi.

Pha trn gn gi dm lin tc xut hin cc vt nt theo phng song song vi trc dm quan st c bng mt thng, pha di ko di ti 1/3 chiu cao dm, hoc pha trn xut hin cc vt nt ng, ng thi pha di xut hin cc vt nt ngang.

Gn u ngm ca cc cng-xn c cc vt nt ng hoc cc vt nt xin nhn r.

(b) i vi bn sn: Xut hin cc vt nt ngang thng gc vi ct thp ch chu ko, ng thi xuyn su ti vng chu nn.

Pha trn gn u ngm ca bn cng-sn xut hin cc vt nt nhn r, vung gc vi ct thp ch chu ko.

Xung quanh pha trn ca sn ti ch c vt nt r rt, hoc pha di c nhng vt nt an nhau.

Du hiu chc thng sn i vi sn phng gi ln ct.

(c) i vi ct: Xut hin vt nt, mt phn lp btng bo v b bong rp, l ct thp chu lc.

Mt bn sinh ra vt nt ngang nhn thy c bng mt thng, pha bn kia btng b nn v, l ct thp chu lc.

Xut hin cc vt nt an nhau r rt.

(d) i vi tng: phn gia ca tng sinh ra cc vt nt an nhau r rt, hoc c thm lp bo v b bong rp.

(e) i vi nt khung: Cc vt nt ng, xin hoc cc vt nt an nhau xut hin nt khung hoc khu vc gn nt khung.3.1.2.2 Kho st bin dng ca kt cuBin dng ca kt cu bao gm vng, gc xoay, gc trt, bin dao ng. Tuy nhin, bin dng kt cu cn phi kho st ch yu l vng. vng ca kt cu v cu kin thng lin quan vi s pht trin vt nt trong kt cu v cu kin.

(1) o vng: i vi cc kt cu nhp ln v trong mt s trng hp c yu cu, c th phi tin hnh o vng/chuyn v khi cho kt cu chu ti (xe chy qua, my mc hot ng, si-l cha y xi-mng, b cha y nc v.v...) hoc cht ti.

Vic cht ti thng thng c th tin hnh t nht theo 4 cp tng ng vi 0%, 25%, 50%, 75% v 100% tng gi tr tiu chun ca hot ti v cc ti trng khc kh d tc dng ln kt cu.

Sau mi cp cht ti, gi ti 60 pht, c s liu ca cc ng h o vng/chuyn v ti cc v tr cn theo di.

Sau khi cht ton b ti, o vng/chuyn v ti cc v tr cn thit trn kt cu. Sau gi ti ti thiu trong vng 24 gi. o tip vng/chuyn v sau khi gi ti c 24 gi.

D ton b ti ra khi kt cu theo 2 cp 50% v 100% ti, c s o chuyn v. Sau 24 gi, c s o mt ln na.

(2) Gii hn ca bin dng ( vng): Gii hn ca bin dng ( vng) c qui nh trong TCVN 5574:1991. C th o vng ca kt cu t khi bt u cho kt cu chu ti (0%) cho n khi chu ti qui nh (100%), vng ban u c th ngoi suy t vng o c khi cht ti vi gi thit s i x ca kt cu giai on trc khi cht ti nm trong giai on n hi.

3.1.2.3 Kho st hin trng kt cu

Khi c yu cu kho st hin trng kt cu, vic kho st s bao gm:

(1) Kch thc v b tr thc t ca cc kt cu, cu kin;

(2) Cu to thc t ca cc lin kt, gi ta;

(3) V tr v khong cch ct thp chu lc ti mt s v tr cn kho st;

(4) Chiu dy lp b tng bo v.

Trong mt s trng hp phi c lp b tng bo v xc nh khong cch, s lng v ng knh ct thp.

3.1.2.4 Xc nh cng thc t ca b tng v ct thp trong kt cu

Ly mu tin hnh th nghim ph hoi trong phng th nghim theo TCXD 239:2000, hoc kim nghim cng thc t ca btng bng cc phng php kim tra khng ph hoi nh sng bt ny, sng siu m theo TCXD 162:1987 v TCXD 171:1989;

Kim tra chng ch v cng ca ct thp s dng khi thi cng ph hp theo TCVN 197:1985.

3.1.2.5 Nghin cu v kim tra h s thit k

Mc ch ca cng tc ny nhm xc nh hay loi tr nguyn nhn gy h hng do thit k, hiu r s chu lc kt cu, la chn v quyt nh bin php sa cha gia cng sau ny. Cc ni dung bao gm:

(1) Kim tra cc bn v thit k dng thi cng v bn v hon cng cng trnh;

(2) Kim tra tnh hp l ca gii php thit k;

(3) Kim tra s , v kt qu tnh ton kt cu, cn thit c th tnh ton li kt cu.

3.1.2.6 Kho st tnh hnh thi cng

Trong qu trnh kho st tnh hnh thi cng, phng php thi cng v lch trnh cng vic s dng c nghin cu k pht hin nhng sai st thi cng v cc li khc. Cng vic kho st gm c:

(1) Phng php thi cng;

(2) S chp hnh cc yu cu, trnh t v tin thi cng c qui nh trong h s thit k v cc qui phm thi cng khc, s gin on/chm tr trong thi cng, thi cng nhanh b qua qui trnh v.v...;

(3) Trong mt s trng hp cn thng k phn tch cc tr s ti trng do thi cng;

(4) Nghin cu kim tra cc bin bn kim tra cht lng v chng ch th nghim vt liu, btng v ct thp.

3.1.2.7 Kho st ti trng v tc ngKho st, iu tra tt c cc loi ti trng v tc ng c th tc dng ln kt cu trong sut thi gian thi cng v s dng cng trnh. Ni dung, ch yu bao gm iu tra v phn tch cc ti trng v hiu ng (ni lc/ng sut, bin dng/ vng) ca cc ti trng ny tc dng ln kt cu, v t hp ca ti trng. Khi c nghi ng v s vt ti trng, tin hnh o thc t tr s ca ti trng tc dng ln cng trnh.

3.1.2.8 Th nghim ti trng

Khi c yu cu, c th tin hnh th nghim ti trng hin trng bng phng php cht ti. Vic th nghim ti trng hin trng c thc hin da vo thit k hoc yu cu s dng, nhm kim tra sc chu ti, kh nng chng nt, bin dng v vng thc t. Qui trnh th nghim ti trng c th tham kho tiu chun b tng Hoa k: ACI 318-2002 (chng 20).

3.1.3 nh gi mc h hng v la chn bin php sa cha kt cu

3.1.3.1 Kim tra, nh gi cng nng v mc h hng ca kt cu

(1) Kim tra an ton (v kh nng chu lc): an ton hay kh nng chu lc ca kt cu c xem l khng m bo khi mt trong cc ch tiu sau y sy ra:

(a) Ch s cng nng v an ton (xem mc con 1.2.6) (Ptt/Pyc) ln hn 1 hay kh nng chu lc ca kt cu khng m bo theo qui nh trong tiu chun TCVN 5574:1991.

(Ptt /Pyc) > 1

(3.1)

trong :

Pyc - gi tr nguy him c th xy ra ca tng ni lc hoc do tc dng ng thi ca mt s ni lc;

Ptt - kh nng chu lc (ng vi tc dng P) ca tit din ang xt ca kt cu khi tit din chu lc t ti trng thi gii hn.

Gi tr Pyc xc nh theo ti trng (thc t hoc theo thit k) tnh ton v c chn trong cc t hp ni lc ng vi cc trng hp nguy him i vi s lm vic ca kt cu, xt c v tr s v c v phng chiu ca ni lc.

Gi tr Ptt c xc nh theo c trng hnh hc (thc t hoc theo thit k) ca tit din v c trng cng (thc t hoc theo thit k) tnh ton ca vt liu. Cc biu thc tnh Ptt cng nh vic c th ho iu kin (3.1) c trnh by trong Chng 3 ca tiu chun TCVN 5574:1991.

(b) Vic kho st, phn tch khng nh l c hin tng nn nt: btng b nn v, lp bo v b bong rp.

(c) Vt nt pht trin khng c du hiu n nh.

(d) Vt nt nh hng ln n cng v tnh tng th (ton khi) ca kt cu.

(e) Cc vt nt nguy him nh trnh by trong khon (4), mc 3.1.2.1.

(2) Kim tra kh nng s dng bnh thng: Kt cu c coi l mt kh nng s dng bnh thng khi mt trong cc ch tiu sau y xy ra:

(a) Ch s cng nng v nt kt cu (att/ayc) ln hn 1 (hay b rng khe nt vt qu gii hn qui nh trong TCVN 5574:1991):

(att/ayc) > 1

(3.2)

trong :

att - b rng khe nt (tnh ton theo l thuyt hoc o thc t) ca btng v tr ngang mc ct thp chu ko,

ayc - b rng gii hn ca khe nt xc nh theo TCVN 5574:1991.

(b) Ch s cng nng v bin dng ca kt cu (ftt/fyc) ln hn 1.0 (hay bin dng vt qu gii hn cho php trong TCVN 5574:1991):

(ftt/fyc) > 1

(3.3)

trong :

ftt - bin dng ca kt cu ( vng, gc xoay, gc trt, bin dao ng) do ti trng tiu chun gy ra,

fyc - tr s gii hn ca bin dng cho trong TCVN 5574:1991.

(c) Mt tnh nng chng thm: C thm m hoc thm chy dng.

(d) Mt nt cao, gy lo s cho ngi s dng. 3.1.3.2 Xc nh nguyn nhn gy h hng kt cuX l kt cu phi cn c vo c ch hay nguyn nhn gy h hng kt cu ngn chn hay loi tr hin tng nt, vng qu gii hn cho php.

Cc nguyn nhn gy nt v h hng kt cu c th l:

(1) Sai st trong thit k kt cu:

(a) Mt ct tit din kt cu/cu kin qu nh, khng khng ch c yu cu v vng, nt hay n nh.

(b) Din tch ct thp chu ko nh, b qua hay xem nh yu cu chng nt v khng ch vng khi tnh ton thit k.

(c) Din tch mt ct btng b, nhng b tr nhiu ct thp lm cho vng chu nn b nt v khi chu ti trng cc hn.

(d) B qua hay khng xt n mt s trng hp ti trng c kh nng xut hin trong qu trnh s dng cng trnh.

(e) Xem nh cc gii php cu to qui nh trong cc tiu chun thuc lnh vc b tng ct thp.

(2) Cng ngh thi cng khng tt:

(a) Cht lng vt liu khng m bo, cp phi btng khng t yu cu.

(b) Vn khun b bin dng, cy chng vn khun b ln, dn n kt cu b vng v ln trc khi chu ti.

(c) Trnh t btng khng tt, tc btng qu nhanh, khng xem xt n iu kin thi tit khi thi cng, xut hin khe nt trong khi thi cng nhng khng x l, bo dng km (nh hin tng nt trong cc b cha loi ln).

(d) Lp bo v ct thp qu ln hoc qu nh.

(e) Gia ti qu sm hoc vt ti khi thi cng (c th sinh ra nt hoc sp kt cu).

(f) Cng ngh trt vn khun khng tt.

(g) Sai st trong b tr ct thp theo mt ct tit din kt cu (v d, nhm tit din ct tng 6 xung tng 4).

(h) B tng khng t cng qui nh.

(i) V cc nguyn nhn khc.

(3) Vt ti:

(a) Vt ti do s dng sai cng nng.

(b) Vt ti do ci ni ci to thm.

(c) Vt ti do c cc trng hp ti trng khng qui nh trong tiu chun hay vt gi tr qui nh trong tiu chun, qui phm (c bit i vi cc cng trnh cng nghip hay cc cng trnh c bit khc).

(4) Cng trnh b ln khng u. 3.1.3.3 La chn gii php sa cha hoc gia cng

Quyt nh bin php x l kt cu phi bt u t phn tch, nh gi mc nguy him v nguyn nhn gy nt, vng cng trnh. Cn phn r ranh gii cc vt nt cn phi sa cha gia cng hay khng cn phi x l. Nm

vng nguyn tc sa cha, gia cng, chn bin php, thi gian, tin v gi thnh thi cng mt cch hp l l nhng iu cn bn ca sa cha, gia cng nhm m bo tui th v cng nng s dng lu di ca kt cu.

3.1.4 Thit k sa cha, gia cng kt cu

3.1.4.1 Nguyn tc chung

Khi kt qu kho st, nh gi khng nh rng kt cu khng m bo an ton hoc kh nng lm vic bnh thng theo mc 3.1.3 th bt buc phi sa cha hay gia cng kt cu.

Cng tc sa cha, gia cng c th tin hnh cho ton b cng trnh hoc ch ti nhng v tr hay cu kin c ch nh, nhng phi tn trng cc nguyn tc sau:

(1) Xc nh ng mc v nguyn nhn ca h hng. i vi cc h hng cha r mc v nguyn nhn, c th theo di v kho st thm, sau khi xc nh ng mc v nguyn nhn mi tin hnh sa cha hay gia cng.

(2) Lm r mc ch sa cha. Da vo tnh cht ca vt nt, vng v yu cu s dng ca cng trnh xc nh mc ch sa cha nh: (i) ch ngn li bo v hay (ii) gia c tng cng.

(3) m bo an ton cho kt cu v ngi s dng trong thi gian kho st, trc khi v trong lc sa cha hay gia cng cng trnh.

(4) p ng yu cu s dng.

(5) m bo bn lu ca vt liu: btng v ct thp.

(6) Tin , tnh kh thi v kinh t ca phng php.

(7) p ng yu cu thit k (v kh nng chu lc), tun theo cc qui nh ca tiu chun kt cu btng ct thp hin hnh.

(8) Tin hnh kim tra cng nng (bt phng trnh (3.1), (3.2) v (3.3)) v bn lu (yu cu cu to theo TCVN 5574:1991)) theo gii php thit k sa cha hoc gia cng. 3.1.4.2 Tnh ton v thit k sa cha, gia cng

(1) Thit k cn kt hp cht ch vi bin php thi cng.

(2) Ti trng v tc ng tc dng ln kt cu c xc nh theo cc qui nh ca tiu chun ti trng v tc ng hin hnh. Ti trng my v cng ngh ly theo s liu cho bi nh cung cp thit b v cng ngh. Khi phi o thc t ti trng th gi tr trung bnh ca ti trng c tnh trn s liu o ti t nht 5 v tr, khi gi tr tiu chun ca ti trng c th ly bng 1.1 ln gi tr trung bnh nhn c.

(3) S tnh ton: S tnh ton kt cu c xc nh cn c vo s tc ng ln kt cu hoc yu cu chu lc thc t. i vi kt cu sa cha, gia cng (bao gm kt cu c v phn gia cng b sung), c th c 2 trng thi chu lc sau:

(a) Trng thi 1: Kt cu c c tnh ton chu phn tnh ti v ti trng thit b c tc dng ln kt cu trc khi sa cha. Cc ti trng ny c gi nguyn v tc dng ln kt cu trong sut qu trnh sa cha v sau sa cha;

(b) Trng thi 2: Kt cu sa cha, gia cng c tnh ton chu phn tnh ti thm, pht sinh do sa cha, thit b t thm, hot ti v ti trng cng ngh.

Ni lc v ng sut trong kt cu c bng tng ca 2 trng thi 1 v 2. Bin dng v ng sut trong phn gia cng b xung ch do trng thi 2 gy ra.

(4) Tit din chu lc ca cu kin phi ly thc t c n c im chu lc, bin dng sau khi sa cha, gia cng v s lm vic ng thi gia phn kt cu c v mi.

(5) Cn thit phi kim tra li kh nng chu lc ca cc kt cu hoc b phn kt cu c lin quan v nn mng cng trnh trong trng hp ti trng pht sinh do sa cha, gia cng l ng k. 3.1.5 Cc phng php, k thut sa cha, gia cng

Phng php sa cha, gia cng kt cu btng ct thp c th l:

(1) Phng php sa cha i vi cc vt nt n nh:

(a) Sa cha b mt: phng php thng dng l c xung quanh vt nt ri trt phng, sn cht kt dnh epoxy, phun va xi mng hoc btng nh, dn vi si thu tinh bng mt-tit epoxy hoc keo epoxy, tng tnh ton khi ca lp mt, neo nt bng bu-lng thp;

(b) Sa cha cc b: cc phng php s dng l phng php p, phng php ng sut trc, c b mt phn btng li;

(c) Phun p lc va xi mng: L phng php ph hp vi cc vt nt n nh c b rng khe nt ln hn 0,5mm.

(2) Gim ni lc kt cu: phng php thng dng c th l gim ti hoc khng ch ti trng s dng (v d: ghi r hot ti ca khu vc l 200 daN/m2 ti cc khu vc s dng), lm kt cu gim ni lc bng cch tng thm gi ta hoc tng thanh chng gim khu ca kt cu.

(3) Tng cng kt cu: Cc phng php thng dng l: (a) tng tit din kt cu (lm sn dy thm, tng chiu cao dm v.v.), (b) k thut bc ngoi bng btng, (c) k thut bc ngoi bng thp hnh, (d) k thut gia cng dn bn thp hoc bn composite, (e) tng cng bng h thng ng sut trc cng ngoi.

(4) Cc phng php khc: tho d lm li, ci thin iu kin s dng kt cu, thng qua th nghim hoc phn tch lun chng khng tin hnh x l.

(5) Phng php sa cha kt cu b nt v xung cp do ln nn mng: Sa cha v gia c nn, mng v gia cng kt cu bn trn c qui nh v ch dn mc3.2. Sau khi hon thnh bin php gia cng nn mng, gim ng k nh hng ca bin dng nn i vi kt cu bn trn, c th p dng phng php (1) phng php sa cha i vi cc vt nt n nh - sa cha kt cu b nt v xung cp do ln nn mng. Trong mt s trng hp c bit, khi mc h hng ca kt cu l nguy him mc d c x l nn mng nhng cn thit phi tng cng kt cu th dng phng php (3). Cc phng php x l do t vn thit k (sa cha) la chn cn c vo hin trng cng trnh, kt qu kim tra v yu cu sa cha ca ch cng trnh.

3.1.6 Phng php gim ni lc kt cuC 2 phng php gim ni lc kt cu l gim ti trng tc dng ln kt cu v tng thm gi .

(1) Gim ti trng:

(a) Gim nh trng lng bn thn kt cu nh: thay tng gch c bng gch rng, mi bng btng ct thp thay bng khung thp nh lp tn hoc fibro ximng, hoc thay b tng nng bng b tng nh,..

(b) Ci thin iu kin s dng cng trnh nh: ngn nga tch nc, thng xuyn qut bi mi nh xng v.v.;

(c) Ci thin cng dng ca cng trnh gim ti nh: chuyn phng lu tr thnh phng lm vic, kho sch thnh phng c sch;

(d) D tng gim ti trng tc dng xung ct v mng.

(2) Tng thm gi : Trong cc cu kin chu un nh dm, sn, vic tng thm ct mi (gi ) l nhm gim khu , ni lc (m men un, lc ct), vng v b rng khe nt trong kt cu. Tuy nhin, cn xem xt v tnh ton li vic b tr ct thp theo thit k gc v theo thc t khi s tnh c tng thm gi .

3.1.7 Phng php tng tit din kt cu

Vic gia cng bng cch tng tit din c thc hin ch yu bng cch t thm ct thp, thm btng lm tng kh nng chu lc ca kt cu, cu kin. Lng ct thp t thm, phn btng thm cn c xc nh bng tnh ton. Cn c bin php thi cng, bin php cu to m bo s lm vic ng thi gia vt liu c v vt liu mi.

3.1.8 K thut gia cng bc ngoi bng btng

K thut ny thng dng gia cng cc kt cu chu nn nh ct nh cng nghip hay dn dng mt hoc nhiu tng. Phng php ny c 3 loi: (a) gia cng bc xung quanh (hnh 3.1.5 (a)), (b) gia cng 1 hoc nhiu mt (hnh 3.1.5 (b) v (c)).

Hnh 3.1.5: Gia cng bc ngoi bng btng

(1) Tnh ton thit k: Gia btng mi v ct thp mi b tr vi kt cu c, tn ti vn ng sut chnh v s chnh bin dng (do btng c chu phn ln tnh ti v c bin dng trc khi gia cng), v vy khi tnh ton kh nng chu lc ca kt cu, phi xem xt tnh hnh c th tnh gim cng ca btng v ct thp thm vo.

Kh nng chu lc cc hn (ti hn) ca ct chu nn dc trc sau khi gia cng c th c kim tra theo cng thc sau:

(3.4)

trong :

N - gi tr tnh ton ca lc nn dc trc tc dng ln ct sau khi gia cng;

( - h s un dc xc nh theo mnh ca ct sau khi gia cng;

fc, Ac - cng tnh ton chu nn v din tch tit din btng c;

fy, As - cng tnh ton v din tch tit din ct thp c;

fcm, Acm - cng tnh ton chu nn v din tch tit din btng mi;

fym, Asm - cng tnh ton v din tch tit din ct thp mi (b xung);

( - h s chit gim cng ca btng mi tng thm v ct thp dc khi btng ca phn gia cng lm vic vi ct c.

Gi tr ca ( c ly nh sau: (a) (=0,8 khi c bin php d ti hon ton cho kt cu/cu kin khi sa cha gia cng (cu kin c v btng mi gn nh cng chu mt ti trng), (b) trong trng hp ch gim ti mt phn no khi thi cng gia cng, phi ly gim gi tr ca (, khi (=0,8 (N/N ((N- phn lc nn tng ln ca phn ti trng tc dng ln kt cu sau khi gia cng).

(2) Yu cu cu to v thi cng: Cn ch cc im sau khi thit k gia cng ct s dng k thut bc ngoi bng btng:

(a) Chiu dy nh nht ca btng mi l 60mm (nu dng btng phun chiu dy nh nht l 50mm);

(b) ng knh ct thp khng nh hn 14mm v khng ln hn 25mm; ng knh ct ai khp kn khng nh hn 8mm;

(c) Khi gia cng bc quanh (4 pha) cn phi t ct ai khp kn. Khi ch gia c mt hoc 2 bn th dng ct ai dng ch U hn vo ct ai c. di ng hn ly bng 10d (nu hn 1 bn) v bng 5d (nu hn 2 bn), trong d l ng knh ct ai. Cng c th dng inh neo chn vo b tng c ca ct ri hn lin kt ct ai ch U vo cc inh neo ny. ng knh inh neo khng nh thua 10mm, su neo gi khng ngn di 10d.

(d) Hai u ct thp chu lc dc trc tng thm phi un m. Khi gia cng ct khung, neo ct thp khng ch ngm vo mng m cn phi c t nht 50% ct thp xuyn qua sn;

(e) Cp cng ca btng mi khng c thp hn mc 200, nn cao hn cng thit k ca btng c. Nn dng loi btng c ct liu b, ng knh ca si khng qu 10mm;

(f) Trc khi thi cng nn d bt ti hoc dng cy chng tm gim phn ti trng tc ng ln kt cu c, sao cho lc dc trong ct (c) ch vo khong 60% sc chu ti ca ct.

(g) c xm b mt cu kin c: li lm ca b mt ct khng nh hn 4mm. Cch mt khong nht nh, thng t 300 n 500mm, trn b mt cu kin c c rnh lm ( su khng t hn 6mm) to thnh lc nm ct gia b tng c v mi;

(h) Lm sch b mt tip gip gia btng c v mi trc khi b tng mi.

3.1.9 K thut gia cng bc ngoi bng thp hnh

Gia cng bc ngoi bng thp hnh cn c s dng gia cng ct b tng.

Gia cng bc ngoi bng thp hnh chia lm 2 loi: gia cng kiu kh (hnh 3.1.6a) v gia cng kiu t (hnh 3.1.6b).

1- kt cu btng hin c; 2- thp hnh gia cng

3- thanh ging;

4- b tng ht nh hoc va

Hnh 3.1.6: K thut gia cng bc ngoi bng thp hnh

Gia cng kiu kh l phng php gia cng bc ngoi bng thp hnh nhng khng c dnh kt vi kt cu btng ct thp c, hoc tuy c nhi va xi mng ct, nhng khng th m bo s truyn lc gia kt cu mi v kt cu c.

Gia cng bc ngoi kiu t l phng php gia cng bc ngoi bng thp hnh m gia thp hnh v kt cu c mt khe h nht nh, c nhi y va xi mng v va epoxy hoc btng nh, dnh kt chng thnh mt khi.

u im ca k thut gia cng bc ngoi bng thp hnh l kch thc cu kin tng ln khng nhiu, nhng c th nng rt cao sc chu ti v tnh do ca kt cu.

tnh ton thit k v yu cu thi cng kt cu gia cng bc ngoi bng thp hnh, c th tham kho cc ti liu k thut chuyn ngnh trong v ngoi nc v vn ny.

3.1.10 K thut gia cng dn bn thp

K thut gia cng dn bn thp l mt phng php dng keo dn dn bn thp hoc bn composite vo mt ngoi chu ko ca dm hay sn btng ct thp (hnh 3.1.7). Keo dn l loi keo epoxy resin c cho thm mt lng nht nh cht c c, cht tng do, tng dai.

Hnh 3.1.7: K thut gia cng dn bn thp hay composite

(1) Tnh ton thit k v yu cu thi cng: Tnh ton thit k v yu cu thi cng dm btng ct thp dn bn thp c th tham kho thm cc ti liu tng t thuc lnh vc ny ca nc ngoi.

(2) Nhng im cn lu khi thc hin gia cng dn bn thp: Phng php dn bn thp c nhng u im ni tri sau:

(a) Tc ng cng ca keo dn nhanh, thi gian thi cng ngn;

(b) Cng ngh n gin, c th thi cng trong khi vn s dng cng trnh (th d i vi cu);

(c) Cng kt dnh ca keo dn cao hn btng v , c th khin cho h gia c v kt cu c hnh thnh mt chnh th tt chu lc ng u, khng sinh ra hin tng ng sut tp trung trong btng;

(d) Bn thp dnh kt chim khng gian nh, hu nh khng lm tng kch thc tit din v trng lng ca cu kin/kt cu b gia cng;

(e) u im ln nht ca bn thp dn l: c th tng rt nhiu kh nng chng nt ca cu kin kt cu (gim b rng khe nt, ngn chn vt nt pht trin), gim vng v nng cao kh nng chu ti;

Tuy nhin, qua nghin cu cho thy, bn thp dn c th to ra hin tng chnh ng sut v bin dng so vi ct thp ch ko ca dm c. Khi thi cng, phn ti tc dng ln cu kin c cng ln, hin tng chnh ng sut v bin dng cng nhiu.

Ngoi ra, cht lng thi cng v cht lng keo dn c nh hng tng i ln i vi hiu qu gia cng. Mc d nhiu th nghim cho thy, khi dm dn bn thp gia cng b ph hoi, bn thp dn c th t n cng chy, nhng cng c mt s th nghim cho thy bn thp dn cha t n cng chy. Nguyn nhn l s ph hoi ca dm do s bong tch gia phn cui bn thp vi btng. Loi ph hoi ny khng c im bo trc r rt, thuc loi ph hoi gin thng trnh khi thit k kt cu.

Hn na, bn thp tng i nng i hi nhiu dn gio khi dn v hin tng n mn bn thp sau gia cng vn cn l cc vn cn nhc hin nay khi s dng k thut ny. Tuy nhin, ngy nay, vi s tin b ca khoa hc vt liu, cc nhc im ca k thut dn bn thp c thay th bi bn composite si carbon, aramid c c tnh: nh, cng v kh nng chng n mn cao.

3.1.11 Gia cng bng phng php ng lc trc cng ngoiNguyn tc ca phng php ny l dng thp thanh, thp hnh (trong mt s trng hp c th dng cp hay b cp) to nn ng lc trc (t y tr i gi l thanh cng ng lc trc), tc dng ngc li vi tc ng ca ngoi lc nhm lm tng kh nng chu lc, gim b rng khe nt v vng ca kt cu. Phng php ny ch yu p dng cho dm n gin hay thanh chu ko ca v ko btng ct thp.

(1) Cng ngh c bn ca thanh cng ng lc trc gia cng dm l:

(a) Thm thanh cng ng lc trc mt ngoi ca vng chu ko cn tng cng;

(b) Neo c nh thanh cng phn u dm;

(c) Ko ng sut trc.

(2) Ko thanh cng ng lc trc: C 2 phng php ko cng thanh cng ng lc trc thng dng trong gia cng dm btng ct thp chu un l:

(a) Phng php ko cng bng kch: Kch tin hnh ko cng t phn u ca thanh cng. Trong trng hp kh t kch ko cng u dm, c th dng kch kiu ko ngoi ko cng phn gia dm (hnh 3.1.8).

1 - dm hin c

2- thp hnh cng gia cng

3 - bu-lng dng cng

4 thanh ph tr

5 - bu-lng cng cao neo

Hnh 3.1.8: K thut gia cng bng phng php cng ngoi (cng sau)

(b) Phng phpko cng bng cc cng c n gin (cl, bulng): y l phng php tc ng theo chiu ngang. Nguyn l ca phng php l khi hai u ca thanh cng gia cng c neo cht vo dm, dng cc cng c n gin nh c-l v bu-lng, cng bc thanh cng t thng bin thnh cong, to ra bin dng v ng sut trc trong thanh cng.

(3) Neo c nh thanh cng ng lc trc: C 4 phng php neo c nh thanh cng ng lc trc:

(a) Neo c nh bng bn thp ch U (hnh 3.1.9): Cc bc tin hnh nh sau:

c b lp btng bo v u dm, qut keo epoxy ln khu vc ny;

Kp cht bn thp hnh ch U c cng chiu rng vi dm trong lp keo epoxy;

Hn u ca thanh ko gia cng vo bn thp ch U.

Hnh 3.1.9: Neo c nh bng bn thp ch U

(b) Ma st bu-lng cng cao kt hp vi keo dn (hnh 3.1.10): Phng php ny c xut trn nguyn tc lm vic ca bu-lng cng cao trong kt cu thp. Cc bc tin hnh l:

Khoan l c cng ng knh vi bu-lng cng cao trn dm c v trn bn thp;

Sau khi qut mt lp keo epoxy hoc h xi-mng cng cao ln bn thp v b mt dm c, dng bu-lng cng cao nn cht bn thp trn dm c nhm to ra lc dnh kt v lc ma st;

Neo c nh thanh cng ng lc trc trn mp li ng hn vi bn thp hoc hn trc tip trn bn thp.

Hnh 3.1.10: Neo c nh s dng bu-lng cng cao

(c) Neo hn: Neo hn l phng php neo c nh hn trc tip thanh thp gia cng trn vng ng sut tng i nh ca ct thp c ca dm (pha trn ca dm n gin, vng gn gi ta, hnh 3.1.11). c rnh trn b mt dm l ct thp c, hn thanh thp ng lc trc vo ct thp c, ng thi dng va epoxy dn thanh thp gia cng vo trong rnh. Khi , khng ch thanh cng ng lc trc c neo m cn tn dng trit c cng ct thp ca dm c.

1- dm hin c, 2- thng cng, 3- cu kin ph tr

Hnh 3.1.11: Neo hn

(d) Neo li dng chi tit chn sn c: nu u dm c gia c cc chi tit chn sn thch hp, hn thanh ko gia cng trn cc chi tit ny c th t c mc ch neo c nh.

(4) Tnh ton dm gia cng: Sau khi kt thc ko cng, thanh cng ng lc trc trn dm gia cng c hai trng thi: (a) thanh cng ng lc trc l ra ngoi, (b) thanh cng ng lc trc v dm c thnh mt khi.

i vi dm c thanh cng ng lc trc l ra ngoi, bin dng ca thanh cng di tc dng ca ti trng bn ngoi nh hn bin dng ca ct thp c chu ko trong dm. Khi tnh ton loi dm ny c th tham kho phng php tnh ton thit k dm btng ng sut trc khng dnh kt.

i vi dm m sau khi kt thc ko cng, nu thm lp btng bo v, hnh thnh mt dm, th thanh ko ng sut trc cng bin dng vi dm c. Tnh ton loi dm ny tng t nh tnh ton cc loi dm btng ct thp thng thng.

3.1.12 Ghi chp v lu gi h s

C 3 h s chnh cn phi lp khi kho st v khi sa cha cng trnh:

(a) Bo co kt qu kim tra chi tit v nh gi hin trng h hng cng trnh,

(b) H s thit k (bao gm thit k k thut v thit k trin khai cc bn v thi cng (t y gi chung l h s thit k k thut)) sa cha hay gia cng kt cu

(c) Cc loi h s v thi cng, nghim thu v bn v hon cng cng trnh.

Bo co kim tra v nh gi hin trng h hng cng trnh phi trnh by r cc ni dung v mc ch kho st qui nh trong cc mc 3.1.2 v 3.1.3. La chn bin php sa cha, gia cng nn c kin ngh trong bo co kim tra. Bo co phi c ch cng trnh hay i din ch cng trnh hoc cp c thm quyn ng chp nhn.

H s thit k k thut sa cha hay gia cng kt cu c thit lp phi th hin r phng n sa cha, gia cng la chn theo cc qui nh ca mc 3.1.5. Cc bn v thit k phi tun theo cc qui nh ca tiu chun TCVN 6084:1995, TCVN 5574:1991 v cc tiu chun lin quan khc. H s thit k k thut phi c ch cng trnh hay i din ch cng trnh hoc cp c thm quyn ph duyt.

Cc loi h s v thi cng, nghim thu v hon cng cng trnh phi c thit lp theo thng l v cc qui nh v xy dng ca Vit Nam.

Tt c cc loi h s trn u c qun l bi ch cng trnh to thun li cho cng tc duy tu, bo tr v nng cp kt cu sau ny. 3.2 Sa cha kt cu h hng do ln nn mng

3.2.1 Nguyn tc chung

Mc ny hng dn phng php kim tra chi tit, xc nh c ch v mc xung cp, v mt s gii php khc phc s xung cp ca cng trnh do nguyn nhn ln nn mng.

3.2.2 Kim tra chi tit

3.2.2.1 Yu cu chung

Kim tra chi tit c thc hin khi pht hin du hiu cng trnh b xung cp do nguyn nhn nn mng. Cng tc kim tra chi tit cn cung cp cc thng tin lin quan n bin dng ca cng trnh v cc yu t c th nh hng n s hnh thnh v pht trin ca bin dng, gm c:

(1) Lch s s dng cng trnh;

(2) iu kin t nn v nc ngm;

(3) H s thit k v hon cng;

(4) Hin trng ca kt cu mng cng trnh;

(5) Hot ng xy dng v hin trng cc kt cu khu vc ln cn.

Vic kim tra chi tit c thc hin theo cng c lp ra vi mc ch nh gi hin trng ca nn mng, khng nh nguyn nhn gy ln v d bo tc xung cp. Trong cng cn nu chi tit khi lng kim tra, phng php thc hin v mc tiu cn t c. Khi xc nh ni dung v khi lng kim tra cn tn dng cc kt qu kim tra c trc.

Ni dung kim tra chi tit gm c:

(1) Kho st a cht cng trnh b sung;

(2) Kho st hin trng mng;

(3) Kho st hin trng h hng kt cu bn trn ;

(4) Kho st hin trng cc cng trnh ln cn ;

(5) Quan trc ln v nghing ca cng trnh;

(6) Quan trc a k thut.

3.2.2.2. Kho st a cht cng trnh b sung

(1) Mc tiu ca kho st a cht b sung l xc nh mt s ch tiu ca t nn m cc kho st trc cha thu thp y . Kho st b sung phi c nh hng theo nhng nhn nh v c ch xung cp ca cng trnh. Phng php, su, s lng v v tr cc im kho st c xc nh theo c im kt cu cng trnh, t nn, c ch v mc xung cp, ...

(2) Cc phng php kho st thng c p dng l:

(a) Khoan ly mu t th nghim trong phng (theo TCVN 2683:1991);

(b) Th nghim xuyn tnh CPT (theo TCXD 174:1989)

(c) Th nghim xuyn tiu chun SPT (theo TCXD 226:1999);

(d) Ct cnh;

(e) Quan trc chuyn v ngang trong t;

(f) Quan trc mc nc ngm v p lc nc l rng, v.v.

Trong kho st nn xc nh cc ch tiu phc v cho tnh ton ln ca t nn theo thi gian.

(3) su kho st c xc nh theo cc yu t:

(a) su nh hng ca ti trng cng trnh: Kch thc v ti trng cng trnh cng ln th su kho st phi tng ln tng ng;

(b) B dy tng t yu: Nn thc hin kho st qua cc lp t yu.

(4) S lng cc im kho st xc nh theo cc yu t:

(a) Qui m ca cng trnh: S lng xc nh trn c s khong cch gia cc im kho st, thng thng bng 15-30 m;

(b) Cc kt qu kho st c: Nu c th s dng s liu kho st c t trc th khi lng kho st b sung c th gim bt;

(c) c im ca hin trng ln: Ngoi cc v tr kho st b tr theo mt li cch u, cn ch tng mt kho st khu vc c bin ng ca iu kin t nn, th hin thng qua s tp trung ca cc vt nt trn kt cu.

(5) V tr ca cc im kho st nn b tr ti:

(a) Cc khe ln, ni c thay i ca ti trng (thay i s tng, thay i ca cng nng,..) v gc ca cng trnh.

(b) Khu vc d kin c bin ng ca iu kin t nn;

(c) Khu vc c thay i ca ln, th hin thng qua mt ca cc vt nt;

(d) Khu vc c ln tuyt i ln nht v nh nht.

(6) Kt qu kho st a cht b sung cn c so snh vi cc kt qu kho st trong nhng giai on trc (nu c). Vic so snh kt qu kho st nhiu giai on cho php nh gi nhng bin ng c th xy ra ca iu kin a cht v pht hin nhng sai st c th xy ra trong qu trnh kho st.

3.2.2.3 Kho st hin trng mng

(1) Vic kho st hin trng mng cn c thc hin khi v mt l do no khng thu thp c h s thit k v hon cng ca cng trnh. i vi trng hp c c cc h s ni trn cng nn kho st ti mt s v tr xung yu, c bit l cc v tr mng ca cng trnh c th b bin dng qu mc. S lng im kho st cn xc nh trong cng, ph thuc vo mc phc tp ca thit k mng v hin trng ca cng trnh.

(2) Cng vic iu tra hin trng mng phi cung cp c cc thng tin:

(a) su chn mng, loi mng, kch thc, ...;

(b) Vt liu mng (cng ca vt liu, b tr ct thp, mc suy thoi ca vt liu,..);

(c) Tnh trng n mn ct thp;

(d) Cc vt nt trn kt cu mng.

(3) Phng php iu tra thng dng l thc hin mt s h o c th trc tip quan st, o c v thc hin kim tra chi tit. H o nn c b tr ti cc v tr:

(a) Di kt cu chu lc chnh;

(b) Ti cc v tr c bin ng t ngt ca ln (th hin thng qua cc vt nt trn kt cu).

3.2.2.4 Kho st hin trng h hng kt cu bn trn

(1) Kho st chi tit hin trng kt cu bn trn gm cc ni dung:

(a) Thu thp v nghin cu h s thit k v hon cng kt cu cng trnh

(b) Quan trc cc vt nt trn kt cu v s pht trin ca vt nt theo thi gian.

(2) Cc quan trc s pht trin ca vt nt c thc hin nh k. Chu k quan trc nn xc nh theo khuyn ngh cho chu k quan trc ln (xem 3.2.2.6).

(3) Cng vic quan trc cc vt nt trn kt cu cn cung cp cc thng tin:

(a) V tr vt nt v hng ca n;

(b) Chiu di vt nt;

(c) B rng vt nt;

(d) su vt nt;

(e) S pht trin ca chiu di, b rng v su ca mt s vt nt tiu biu.

Phng php quan trc cc vt nt trn kt cu c trnh by trong mc 3.1.2.

(4) V tr, hnh dng v chiu di vt nt c th hin trn cc bn v. Kt qu quan trc s pht trin ca vt nt theo thi gian c trnh by di dng biu .

3.2.2.5 Kho st hin trng cc kt cu ln cn

iu tra hin trng khu vc xung quanh cn cung cp cc thng tin phc v cho vic nhn nh nguyn nhn gy xung cp ca cng trnh. Phng php kho st thng p dng l quan st v m t. Cc thng tin cn thu thp khi kho st cc cng trnh ln cn gm:

(1) Lch s xy dng v s dng;

(2) Khong cch n cng trnh;

(3) Qui m v c im kt cu (din tch mt bng, loi kt cu, s tng, mng, cng nng, ...);

(4) Tnh trng ca kt cu: Nu pht hin cc du hiu ca hin tng nghing, ln, nt, v.v., th cn th hin chi tit trn bn v.

Trong trng hp tc nhn gy xung cp cng trnh l h o, xung ng hoc cc ti trng khc th cc c trng ca cc tc nhn ny cn c xc nh trong qu trnh kho st. V d i vi h o th cn xc nh kch thc, su, bin php gi thnh, bin php h mc nc ngm, tc thi cng, v.v.

3.2.2.6 Quan trc ln v nghing ca cng trnh

(1) Yu cu chung

Quan trc ln cho php xc nh ln tuyt i v tc pht trin ca ln ca cng trnh theo thi gian. Tc ln ca cng trnh c theo di bng cch nh k o ln ca cc mc gn trn cng trnh so vi mc chun (c coi l khng ln).

Cng tc quan trc c th c thc hin bng phng php thu chun hnh hc, thu chun lng gic, thu chun thu tnh hoc bng cch chp nh. Trong iu kin thng thng nn p dng phng php ca TCXD 271:2002.

(2) Xc nh cp o ln

Quan trc ln ca cng trnh cn c thc hin lu di vi chnh xc cao, v vy nn la chn chnh xc cp I hoc cp II khi o ln.

(3) Chu k o

Khong thi gian gia 2 ln tin hnh quan trc ln ph thuc vo tc ln v cp o ln. Khi tc ln nh th khong thi gian gia 2 ln o phi ln mi c th xc nh chnh xc ln. Ngc li nu tc ln ln th c th o vi chu k dy hn. Thng thng khong thi gian gia hai ln o bng 1-3 thng.

(4) B tr mc o ln

thc hin quan trc cn cn lp t h mc chun v cc mc o ln.

Mc chun c b tr bn ngoi cng trnh v phi m bo khng b ln trong sut thi gian thc hin quan trc. Trong iu kin c th ca tng cng trnh, cn t 2-3 mc chun. Nn s dng mc chun loi A cho cc cng trnh quan trng hoc loi B cho cc cng trnh thng thng (theo phn loi mc chun ca TCXD 271:2002).

Cc mc o ln c gn trn cng trnh ti cc v tr ph hp c th nh gi c tnh trng ln ca cng trnh ni chung v xc nh c bin dng ca kt cu. V tr gn mc o ln trn mt s loi kt cu thng gp nh sau:

(a) Kt cu tng chu lc:Ti cc v tr giao nhau gia tng ngang v tng dc;

(b) Kt cu khung: Ti cc chn ct;

(c) Cng trnh dng thp (silo, ng khi, ...): B tr ti thiu 4 mc phn b u trn chu vi ca kt cu;

Khong cch gia cc mc o ln khng nn ln hn 15 m. Mc c th c b tr dy hn quanh khe ln v ti cc v tr c bin ng ca iu kin t nn, thay i ti trng cng nh ti cc v tr quan st thy s thay i ca tc ln.

3.2.2.7 Quan trc a k thut

Quan trc a k thut nn c thc hin nh gi v d bo s pht trin ca ln v chuyn v ngang trong t nn. Cc quan trc thng c thc hin l:

(1) Quan trc nc ngm (mc nc, p lc nc l rng,..);

(2) Quan trc s pht trin ca ln trong t;

(3) Quan trc chuyn dch ngang.

S lng im quan trc, v tr cc im v chu k quan trc c xc nh theo qui m, c im cng trnh v tc xung cp.

3.2.3. Xc nh c ch v d bo tc xung cp

3.2.3.1 Xc nh c ch xung cp

(1) Vic xc nh c ch gy ln ca cng trnh cn c thc hin trn c s kt hp cc kt qu tnh ton v kt qu kim tra chi tit;

(2) Cc kt qu quan trc ln v kt qu kho st a cht cn c tp hp c h thng. Nn xc nh quan h (nu c) gia tc ln v c trng ca iu kin a cht (v d b dy tng t yu);

(3) Cc tnh ton cn thc hin phc v cho vic xc nh c ch gy xung cp gm c:

(a) Tnh ton kim tra theo trng thi gii hn th nht: Cng ca t nn (TCXD 45: 1978), sc chu ti ca cc (TCXD 205:1998), kh nng chu ti ca kt cu mng b tng ct thp (TCVN 5574:1991), mng kt cu gch (TCVN 5573:1991);

(b) Tnh ton kim tra theo trng thi gii hn th hai: Tnh ton ln ln tuyt i v ln theo thi gian.

(4) C ch xung cp do nguyn nhn nn mng thng gp c tm tt trong bng 3.2.1.

Bng 3.2.1 Nhn nh c ch xung cp do nguyn nhn nn mng

TTNguyn nhn h hngKt qu kho stC ch

1t nn khng kh nng chu ti- ln ln

- Tc ln cao v khng c du hiu gim dnPh hoi ca t nn

2Kt cu mng khng kh nng chu ti- ln ln

- Tc ln cao v khng c du hiu gim dn

- Nt gy kt cu mng ti cc v tr xung yuPh hoi ca kt cu mng

3 ln tuyt i ln- Tng t yu c b dy ln

- ln ln

- Tc ln gim dn theo thi gianLn c kt

4 ln lch ln- Tng t yu c b dy bin i mnh

- Chnh lch ln ca ti trng cng trnh

- Cc vt nt xin trn kt cuLn lch

5- ln v cc vt nt trn kt cu tng sau khi cng trnh c s dng n nh mt thi gian kh di

- B dy tng t yu kh ln

- Khng c hot ng xy dng mi khu vc ln cn

- Cng trnh nm gn ging khai thc ncH mc nc ngm

6- ln v cc vt nt trn kt cu tng sau khi cng trnh c s dng n nh mt thi gian kh di

- C hot ng xy dng mi khu vc ln cn (h o, nn p, cng trnh mi,... )Ln nh hng

Ch thch bng 3.2.1: Khng c bin ng ng k ca ti trng cng trnh

3.2.3.2 D bo tc xung cp do ln

Tc xung cp ph thuc vo s pht trin ca ln theo thi gian.Vic d bo tc xung cp c th c thc hin theo cc phng php sau:

(1) Tnh ton ln theo thi gian trn c s ti trng cng trnh v cc ch tiu c l ca t nn (TCXD 45-78);

(2) Phn tch kt qu quan trc, t d bo s pht trin ca ln, nghing, nt v s nh hng ca n i vi cng nng v kh nng chu ti v yu cu s dng bnh thng ca cng trnh.

3.2.4. nh gi mc xung cp v la chn bin php khc phc

3.2.4.1 nh gi mc xung cp

(1) Nguyn tc chung: Mc xung cp do nguyn nhn nn mng c nh gi theo cc ch s cng nng:

(a) Cng nng v an ton (kh nng chu ti);

(b) Cng nng s dng bnh thng ca cng trnh: ln tuyt i, ln lch v nghing ca kt cu;

(2) nh gi mc xung cp theo cng nng v an ton: Ti trng truyn ln mng khng c vt qu sc chu ti cho php ca nn:

N2;

(d) Cn ch n ti trng thi cng p cc khi thit k h thng ging mng.

Mng b tng ct thp di cc ct hoc tng BTCT c th l mng n, mng bng hoc mng b. Gii php thit k gia cng cc loi mng ny bng cc thng c s dng l:

(a) i vi mng n: Nu b rng mng tng i nh th c th b tr cc ra pha ngoi mng. Ngc li khi b rng y mng ln th phi khoan dn qua b tng c th p cc;

(b) i vi mng bng: Nu b rng mng tng i nh th c th b tr cc hai bn mng tng t nh trng hp mng di tng chu lc. Nu b rng mng kh ln th phi p dng bin php khoan dn qua b tng bn mng p cc;

(c) i vi mng b: Trong trng hp ny vic khoan dn qua b tng l bt buc. Khi b tr cc cn lu trnh khoan dn vo cc sn mng (nu c).

Neo p cc c th c lin kt vo h thng i ging hoc vo h thng dm thp tm thi c lp t phc v mc ch p cc v c thu hi ngay sau khi kt thc p cc. Cc u im v nhc im ca tng bin php thi cng nu trn nh sau:

Khi s dng h thng neo c nh:

(a) Neo v i ging n nh, d dng p cc thng ng;

(b) V tr p cc kh thay i;

(c) Thi gian t khi thi cng i ging n khi p di (>15 ngy);

(d) Chi ph cao v h thng i ging c thit k chu ti trng thi cng cao hn nhiu so vi ti trng thit k;

(e) Khng thu hi c neo.

Khi s dng h thng dm thp tm thi:

(a) D dng iu chnh v tr p cc cho ph hp vi iu kin thc t, c bit l khi cn b sung cc;

(b) C th bt u p cc ngay sau khi lp t h dm;

(c) Dm c thu hi ngay sau khi p cc;

(d) Km n nh;

(e) D gy h hi kt cu cng trnh c do p cc b ti v tr truyn ti t dm thp sang kt cu.

Hnh 3.2.6 th hin mt v d v cu to h thng i cc s dng trong gia c mng ca kt cu khung. tng cng bm dnh gia h mng mi v c mng, nn c nhm b mt b tng mng c v c th tng cng mt s neo lin kt. Khong cch gia cc neo thp thng thng bng 20 - 30 cm. Nn b sung ging gia cc ct ca cng trnh nu mng c khng c h thng ging hoc h thng ging c khng cng.

Hnh 3.2.6. Gia c mng di ct hoc tng b tng ct thp

3.2.4.5. Sa cha kt cu b h hng do ln nn mng

Vic sa cha kt cu bn trn b xung cp do nguyn nhn ln nn mng c thc hin sau khi hon thnh bin php gia cng nn mng. Mt s phng php sa cha c trnh by trong mc 3.1.4 ca Tiu chun ny.

3.2.5 Ghi chp v lu gi h s

Cc h s v kho st, thit k, v thi cng cn c tp hp v lu tr lu di.

Trong qu trnh thi cng cn thc hin ghi chp v lp h s theo qui nh ca cc tiu chun TCVN 4055:1985; TCXD 79: 1980; TCVN 4453: 1995 v TCVN 4085: 1985.

Bng 3.2.1. ln v nghing gii hn ca cng trnh (theo TCXD 205:1997)

Cng trnh ln lch tng i

nghing

ln trung bnh hoc ln nht (trong ngoc), cm

1. Nh sn xut 1 tng v nh dn dng nhiu tng c khung hon ton bng b tng ct thp

0,002-(8)

2. Nh v cng trnh m trong kt cu khng xut hin ni lc do ln khng u0,006-(15)

3. Nh nhiu tng khng khung vi tng chu lc:

- Bng tm ln

- Bng khi ln hoc th xy gch khng c thp

- Nh trn nhng c thp, trong c ging b tng ct thp0,0016

0,0020

0,00240,005

0,0005

0,000510

10

15

4. Cng trnh thp cha bng kt cu b tng ct thp:

- Nh cng tc v silo, kt cu ti ch lin khi trn cng mt mng b

- Nh trn nhng kt cu lp ghp

- Silo c lp kt cu ton khi ti ch

- Nh trn nhng kt cu lp ghp

- Nh cng tc ng c lp-

-

-

-

-0,003

0,003

0,004

0,004

0,00440

30

40

30

25

5. ng khi c chiu cao H, m:

- H ( 100 m

- 100 ( H ( 200 m

- 200 ( H ( 300 m

- H > 300 m-

-

-

-0,005

1/(2H)

1/(2H)

1/(2H)40

30

20

10

6. Cng trnh cng cao n 100 m, ngoi nhng iu ni im 4 v 5-0,00420

7. Cng trnh lin lc, ng ten:

- Thn thp tip t

- Thn thp pht thanh cch in vi t

- Thp pht thanh

- Thp pht thanh sng ngn

- Thp (block ring r)-

-

0,002

0,0025

0,0010,002

0,001

-

-

-

-20

10

-

-

-

-

8. Tr ng dy ti in trn khng:

- Tr trung gian

- Tr neo, neo gc, tr gc trung gian, tr vng cung, ca chnh ca thit b phn phi kiu h

- Tr trung chuyn c bit0,003

0,0025

0,002-

-

-

Ch thch bng 3.2.1:

(a) Tr gii hn ca vng (vng ln) tng i ca nh ni im 3 ly bng .(b) Khi xc nh ln lch tng i ni im 8, L l khong cch gia 2 trc block mng theo hng ti trng ngang, cn cc tr ko dy - l khong cch gia cc trc ca mng chu nn v neo.(c) Nu nn gm cc lp t nm ngang (vi dc khng qu 0.1) th tr gii hn v ln ln nht v ln trung bnh cho php tng ln 20%.(d) i vi cc cng trnh ni im 2 v 3 c mng dng b th tr gii hn ca ln trung bnh cho php tng ln 1,5 ln.(e) Trn c s tng kt kinh nghim thit k,