TCXDVN Tiu chun xy dng Vit nam

TCXDVN 375 : 2006

Xut bn ln 1

Thit k cng trnh chu ng t

Design of structures for earthquake resistance

Phn 2: Nn mng, tng chn v cc vn a k thut

H ni - 2006

TCXDVN 375 : 2006

TCXDVN 375 : 2006

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mc lc

li ni u...........................................................................................................................................................1

1 Tng qut ..........................................................................................................................................................3

1.1 Phm vi p dng .................................................................................................................... 3 1.2 Cc ti liu tham kho v tiu chun ..................................................................................... 3

1.2.1 Cc tiu chun tham kho chung................................................................................... 4 1.3 Cc gi thit ........................................................................................................................... 4 1.4 Phn bit gia nguyn tc v quy nh p dng .................................................................... 4 1.5 Cc thut ng v nh ngha................................................................................................... 4

1.5.1 Cc thut ng chung cho ton b Tiu chun................................................................ 4 1.5.2 Cc thut ng b sung c s dng trong Tiu chun ny.......................................... 4

1.6 Cc k hiu............................................................................................................................. 5 1.7 H n v SI............................................................................................................................ 7

2 Tc ng ng t .........................................................................................................................................7

2.1 nh ngha v tc ng ng t............................................................................................7 2.2 Biu din theo thi gian.......................................................................................................... 7

3 Cc tnh cht ca t nn .............................................................................................................................8

3.1 Cc thng s v bn ......................................................................................................... 8 3.2 Cc thng s cng v thng s cn........................................................................... 8

4 Cc yu cu i vi vic la chn v tr xy dng v t nn .............................................................9

4.1 La chn v tr xy dng ......................................................................................................... 9 4.1.1 Tng qut ....................................................................................................................... 9 4.1.2 Vng ln cn t gy cn hot ng.............................................................................. 9 4.1.3 n nh mi dc ........................................................................................................ 9 4.1.4 Cc loi t c kh nng ho lng ............................................................................... 12 4.1.5 ln qu mc ca t di ti trng c chu k.......................................................... 14

4.2 Kho st v nghin cu v nn............................................................................................ 14 4.2.1 Cc tiu ch chung........................................................................................................ 14 4.2.2 nh dng nn t i vi tc ng ng t .............................................................. 14 4.2.3 S ph thuc ca cng v gim chn ca t vo mc bin dng .................... 15

5 H nn mng ..................................................................................................................................................17

5.1 Cc yu cu chung............................................................................................................... 17 5.2 Cc quy nh i vi thit k c s....................................................................................... 17 5.3 Cc hiu ng tc ng thit k.............................................................................................18

5.3.1 Mi quan h trong thit k kt cu ............................................................................... 18 5.3.2 Truyn cc hiu ng ca tc ng ng t ln nn.................................................... 18

5.4 Cc ch tiu kim tra v xc nh kch thc ........................................................................ 19 5.4.1 Mng nng hoc mng chn trong t......................................................................... 19 5.4.2 Cc v tr ..................................................................................................................... 22

6 Tng tc gia t v kt cu ....................................................................................................................24

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7 kt cu tng chn........................................................................................................................................25

7.1 Cc yu cu chung .............................................................................................................. 25 7.2 La chn v nhng iu lu chung v thit k.................................................................. 25 7.3 Cc phng php phn tch ................................................................................................. 25

7.3.1 Cc phng php chung.............................................................................................. 25 7.3.2 Cc phng php n gin ho: phn tch ta tnh...................................................... 26

7.4 Kim tra bn v n nh .................................................................................................. 29 7.4.1 Tnh n nh ca nn t.............................................................................................. 29 7.4.2 Neo .............................................................................................................................. 29 7.4.3 bn kt cu............................................................................................................. 29

ph lc A (tham kho) .................................................................................................................................31

Cc h s khuch i a hnh ......................................................................................................................31

ph lc b (bt buc).....................................................................................................................................32

Cc biu thc nghim phn tch ho lng n gin ho ..........................................................32

ph lc c (bt buc).....................................................................................................................................34

Cc cng tnh u cc...............................................................................................................................34

ph lc d (tham kho)..................................................................................................................................36

Tng tc ng lc gia t v kt cu (ssi). Cc hiu ng chung v tm quan trng ................36

ph lc e (bt buc) .....................................................................................................................................37

Phng php phn tch n gin ha i vi kt cu tng chn ....................................................37

ph lc f (tham kho) ..................................................................................................................................43

sc chu ti ng t ca mng nng .......................................................................................................43

TCXDVN 375 : 2006

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Li ni u

TCXDVN 375:2006: Thit k cng trnh chu ng t c bin son trn c s chp nhn Eurocode 8: Design of structures for earthquake resistance c b sung hoc thay th cc phn mang c th Vit Nam.

Eurocode 8 c 6 phn:

EN1998 - 1: Quy nh chung, tc ng ng t v quy nh i vi kt cu nh; EN1998 - 2: Quy nh c th cho cu;

EN1998 - 3: Quy nh cho nh gi v gia cng khng chn nhng cng trnh hin hu; EN1998 - 4: Quy nh c th cho sil, b cha, ng ng; EN1998 - 5: Quy nh c th cho nn mng, tng chn v nhng vn a k thut; EN1998 - 6: Quy nh c th cho cng trnh dng thp, dng ct, ng khi.

Trong ln ban hnh ny mi cp n cc quy nh i vi nh v cng trnh tng ng vi cc phn ca Eurocode 8 nh sau:

- Phn 1 tng ng vi EN1998 - 1; - Phn 2 tng ng vi EN1998 - 5;

Cc phn b sung hoc thay th cho ni dung Phn 1 gm :

- Ph lc F: Mc v h s tm quan trng - Ph lc G: Phn cp, phn loi cng trnh xy dng - Ph lc H: Bn phn vng gia tc nn lnh th Vit Nam - Ph lc I: Phn vng gia tc nn theo a danh hnh chnh - Ph lc K: Bng chuyn i t nh gia tc nn sang cp ng t

TCXDVN 375 : 2006 do Vin Khoa hc Cng ngh Xy dng bin son, V Khoa hc Cng ngh

trnh duyt, B Xy dng ban hnh theo quyt nh s ngy thng nm 2006.

TCXDVN 375 : 2006

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Tiu chun xy dng vit nam TCXDVN 375 : 2006

3

Xut bn ln 1

Thit k cng trnh chu ng t

Design of structures for earthquake resistance

Phn 2: Nn mng, tng chn v cc vn a k thut

1 Tng qut

1.1 Phm vi p dng

(1)P Phn 2 ca tiu chun thit lp cc yu cu, tiu ch v quy nh v vic chn v tr xy dng v nn mng ca kt cu chu tc ng ng t. N bao gm vic thit k cc loi mng khc nhau, cc loi tng chn v s tng tc gia kt cu v t nn di tc ng ng t. V vy n b sung cho Eurocode 7 - Tiu chun khng bao gm cc yu cu c bit

cho thit k chu ng t.

(2)P Cc iu khon ca Phn 2 p dng cho cc cng trnh dng nh - Phn 1 ca Tiu chun, cng trnh cu (EN 1998-2), thp, ct v ng khi (EN 1998-6), silo, b cha v ng ng (EN 1998-4).

(3)P Cc yu cu thit k c bit cho mng ca cc loi kt cu no , khi cn, c th tm trong cc phn tng ng ca tiu chun ny.

(4) Ph lc B ca tiu chun ny a ra cc biu thc nghim cho vic nh gi n gin ho v kh nng ho lng c th xy ra, Ph lc E a ra quy trnh n gin ho cho php phn tch ng t ca kt cu tng chn.

GHI ch 1: Ph lc tham kho A cung cp cc thng tin v cc h s khuch i a hnh.

GHI ch 2: Ph lc tham kho C cung cp cc thng tin v cng tnh ca cc.

GHI ch 3: Ph lc tham kho D cung cp cc thng tin v tng tc ng lc gia kt cu v t nn.

GHI ch 4: Ph lc tham kho F cung cp cc thng tin v kh nng chu tc ng ng t ca mng nng.

1.2 Cc ti liu tham kho v tiu chun

(1)P Phn 2 ca tiu chun c hnh thnh t cc ti liu tham kho c hoc khng ngy thng v nhng iu khon t cc n phm khc. Cc ti liu tham kho c trch dn ti nhng v tr thch hp trong vn bn tiu chun v cc n phm c lit k di y. i vi cc ti liu c ngy thng, nhng sa i b sung sau ngy xut bn ch c p dng i vi tiu

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chun khi tiu chun ny c sa i, b sung. i vi cc ti liu khng ngy thng th dng phin bn mi nht.

1.2.1 Cc tiu chun tham kho chung

EN 1990 C s thit k kt cu

EN 1997-1 Thit k a k thut Phn 1: Cc quy nh chung

EN 1997-2 Thit k a k thut Phn 2: Kho st v th nghim t

EN 1998-2 Thit k cng trnh chu ng t Phn 2: Quy nh c th cho cu

EN 1998-4 Thit k cng trnh chu ng t Phn 4: Quy nh c th cho kt cu sil,

b cha v ng ng

EN 1998-6 Thit k cng trnh chu ng t Phn 6: Quy nh c th cho cng trnh

dng thp, dng ct, ng khi.

TCXDVN ......:2006 Thit k cng trnh chu ng t Phn 1: Quy nh chung, tc ng

ng t v quy nh i vi kt cu nh

1.3 Cc gi thit

(1)P p dng cc gi thit chung trong 1.3 ca EN 1990:2002.

1.4 Phn bit gia nguyn tc v quy nh p dng

(1)P p dng cc quy nh trong 1.4 ca EN 1990:2002.

1.5 Cc thut ng v nh ngha

1.5.1 Cc thut ng chung cho ton b Tiu chun

(1)P p dng cc thut ng v nh ngha nu trong Ph lc D, Phn 1 ca tiu chun ny.

(2)P p dng 1.5.1 ca tiu chun ny cho cc thut ng chung ca ton b tiu chun.

1.5.2 Cc thut ng b sung c s dng trong Tiu chun ny

(1)P p dng cc nh ngha v t nn nh trong 1.5.2 ca EN 1997-1:2004, cn nh ngha cc thut ng chuyn ngnh a k thut lin quan n ng t, nh ho lng c cho trong ti liu ny.

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(2) Trong Phn 2 ny p dng cc thut ng c nh ngha trong 1.5.2 Phn 1 ca tiu

chun ny.

1.6 Cc k hiu

(1) Cc k hiu di y -c s dng trong tiu chun ny. Tt c cc k hiu trong phn 2 s c nh ngha trong tiu chun khi chng xut hin ln u tin tin s dng. Thm vo l danh sch k hiu c lit k sau y. Mt s k hiu ch xut hin trong ph lc th c nh ngha ch chng xut hin.

Ed H qu tc ng thit k

Epd bn theo phng ngang mt bn ca mng do p lc b ng ca t

ER T s nng lng trong th nghim xuyn tiu chun (SPT)

FH Lc qun tnh thit k theo phng ngang do tc ng ng t

FV Lc qun tnh thit k theo phng thng ng do tc ng ng t

FRd Sc khng ct thit k gia y mng nm ngang v nn t

G Mun ct

Gmax Mun ct trung bnh khi bin dng nh

Le Khong cch ca cc neo tnh t tng trong iu kin ng

Ls Khong cch ca cc neo tnh t tng trong iu kin tnh

MEd Cc tc ng thit k di dng mmen

N1(60) Ch s xuyn tiu chun (SPT) c chun ho theo p lc bn thn t v theo t s nng lng

NEd Lc php tuyn thit k ln y mng nm ngang

NSPT S nht p trong th nghim xuyn tiu chun (SPT)

PI Ch s do ca t

Rd Sc chu ti thit k ca t nn

S H s nn c nh ngha trong mc 3.2.2.2 ca tiu chun ny.

ST H s khuch i a hnh

VEd Lc ct ngang thit k

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W Trng lng khi trt

ag Gia tc nn thit k trn t nn loi A (ag = IagR) agR nh gia tc nn tham chiu trn nn loi A

avg Gia tc nn thit k theo phng thng ng

c Lc dnh din t theo ng sut hu hiu ca t cu Sc khng ct khng thot nc ca t

d ng knh cc

dr Chuyn v ca tng chn

g Gia tc trng trng

kh H s ng t theo phng ngang

kv H s ng t theo phng ng

qu bn chu nn c n hng

r H s tnh ton h s ng t theo phng ngang (Bng 7.1)

s Vn tc truyn sng ct

s,max Gi tr trung bnh ca vs khi bin dng nh (< 10-5)

T s ca gia tc nn thit k trn t nn loi A, ag, vi gia tc trng trng g

Trng lng n v ca t

d Trng lng n v kh ca t

I H s tm quan trng

M H s ring ca tham s vt liu

Rd H s ring ca m hnh

w Trng lng n v ca nc

Gc ma st gia t nn v mng hoc tng chn

Gc ca sc khng ct tnh theo ng sut hu hiu

Khi lng n v

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vo p lc ton phn ca bn thn t, cng nh ng sut ton phn theo phng ng

vo' p lc hu hiu ca bn thn t, cng nh ng sut hu hiu theo phng ng

cy,u Sc khng ct khng thot nc ca t khi chu ti trng c chu k

e ng sut ct khi chu tc ng ng t.

1.7 H n v SI

(1)P S dng h n v SI theo ISO 1000.

(2) Ngoi ra, c th s dng cc n v c khuyn ngh trong 1.7, Phn 1 tiu chun ny.

GHI ch: i vi cc tnh ton a k thut, cn tham kho thm 1.6(2) ca EN 1997-1:2004.

2 tc ng ng t

2.1 nh ngha v tc ng ng t

(1)P Tc ng ng t phi ph hp vi cc khi nim v nh ngha c bn nh nu trong

3.2, Phn 1 ca tiu chun ny, c xt n iu khon trong 4.2.2.

(2)P Cc t hp ca tc ng ng t vi cc tc ng khc phi c tin hnh theo 3.2.4,

Phn 1 ca tiu chun ny.

(3) Cc n gin ha khi la chn tc ng ng t s c nu ti cc im thch hp trong tiu chun ny.

2.2 Biu din theo lch s thi gian

(1)P Nu cc php phn tch theo min thi gian c tin hnh th c th s dng c gin gia tc nhn to v cc gin thc ghi chuyn dch mnh ca t nn. Ni dung lin quan n

gi tr ln nht v tn s phi theo quy nh trong 3.2.3.1, Phn 1 ca tiu chun ny.

(2) Khi kim tra n nh ng lc bao gm cc tnh ton bin dng lu di ca nn, cc kch ng thng bao gm cc gin gia tc ghi c khi ng t xy ra ti a im xy dng, v chng c thnh phn tn s thc t l thp v c tng quan nht nh v thi gian gia thnh phn ngang v thng ng ca chuyn ng. Khong thi gian xy ra chuyn ng

mnh phi c chn theo phng thc ph hp vi 3.2.3.1, Phn 1 ca tiu chun ny.

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3 Cc tnh cht ca t nn

3.1 Cc thng s v bn

(1) Ni chung c th s dng cc thng s bn ca t trong iu kin tnh v khng thot nc. i vi t dnh, thng s bn thch hp l sc khng ct khng thot nc cu, c hiu chnh cho tc gia ti nhanh v suy gim do gia ti lp khi ng t nu vic hiu chnh l cn thit v c kim chng y bng thc nghim thch ng. i vi t ri,

thng s bn thch hp l sc khng ct khng thot nc khi gia ti lp cy,u. Gi tr ny phi tnh n kh nng tch lu p lc nc l rng.

(2) Mt khc, c th s dng cc thng s bn hu hiu vi p lc nc l rng pht sinh khi gia ti theo chu k. i vi , c th s dng bn nn c n hng qu.

(3) Cc h s M i vi cc c trng vt liu cu, cy,u v qu c biu th l cu, cy, qu v i vi tan c biu th l .

GHI ch: Gi tr cu, cy, qu v khuyn ngh l cu = 1,4, cy = 1,25, qu = 1,4 v = 1,25.

3.2 Cc thng s cng v thng s cn

(1) Do nh hng ca n n tc ng ng t thit k, thng s cng chnh ca t nn di ti trng ng t l m un ct G, tnh theo cng thc:

2. sG = (3.1)

trong l khi lng n v v s l vn tc truyn sng ct ca t nn.

(2) Cc tiu ch xc nh s, k c s ph thuc ca chng vo mc bin dng ca t, c cho trong 4.2.2 v 4.2.3.

(3) gim chn c xem nh mt c trng ph ca nn trong trng hp c k n tng

tc gia t nn v kt cu nh c quy nh trong chng 6.

(4) cn bn trong do ng x phi n hi ca t di tc dng ca ti trng c chu k, v cn lan ta do sng ng t lan truyn ra khi mng, phi c xem xt ring bit.

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4 Cc yu cu i vi vic la chn v tr xy dng v t nn

4.1 La chn v tr xy dng

4.1.1 Tng qut

(1)P Cn tin hnh nh gi a im xy dng cng trnh xc nh bn cht ca t nn nhm m bo rng cc nguy c ph hoi, mt n nh mi dc, s ha lng v kh nng b nn cht do ng t gy ra l nh nht.

(2)P Kh nng xy ra cc hin tng bt li ny phi c kho st theo quy nh trong cc mc di y.

4.1.2 Vng ln cn t gy cn hot ng

(1)P Nh thuc tm quan trng cp II, III, IV nh nh ngha trong 4.2.5, Phn 1 ca tiu chun

ny khng c xy dng trong khu vc ln cn cc t gy kin to c xc nhn trong cc vn bn chnh thc do c quan c thm quyn ca Quc gia ban hnh l c hot ng ng t.

(2) Vic khng pht sinh chuyn dch trong giai on hin i ca k T c th c xem l du hiu t gy khng cn hot ng i vi phn ln cc loi kt cu khng gy nguy c cho an ton cng cng.

(3)P Cng tc kho st a cht c bit phi c tin hnh phc v quy hoch th v cho cc kt cu quan trng c xy dng gn cc t gy c th cn hot ng trong cc vng c nguy c xy ra ng t, nhm xc nh ri ro sau ny v s nt v nn t v mc chn

ng ca t nn.

4.1.3 n nh mi dc

4.1.3.1 Cc yu cu chung

(1)P Vic kim tra n nh ca nn phi c tin hnh vi cc kt cu c xy dng trn hoc gn vi mi dc t nhin hoc mi dc nhn to, nhm m bo rng an ton v/hoc kh nng lm vic ca cc kt cu c duy tr di tc dng ca cp ng t thit k.

(2)P Trong iu kin chu ti trng ng t, trng thi gii hn ca mi dc l trng thi m khi vt qu n th s pht sinh chuyn v lu di (khng phc hi) ca t nn ln hn mc cho php trong phm vi chiu su c nh hng i vi kt cu v chc nng ca cng trnh.

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(3) C th khng cn kim tra n nh i vi nhng cng trnh thuc tm quan trng cp I

nu kinh nghim i chng bit cho thy t nn ti a im xy dng l n nh.

4.1.3.2 Tc ng ng t

(1)P Tc ng ng t thit k c gi thit kim tra n nh phi tun theo cc nh ngha

trong 2.1.

(2)P Khi kim tra n nh ca nn ca cc kt cu c h s tm quan trng I ln hn 1 nm trn hoc gn mi dc cn tng lc ng t thit k thng qua h s khuch i a hnh.

ch thch: Mt s hng dn cho cc gi tr ca h s khuch i a hnh c cho trong Ph lc tham kho A.

(3) Tc ng ng t c th c n gin ha nh quy nh trong 4.1.3.3.

4.1.3.3 Cc phng php phn tch

(1)P Phn ng ca sn dc i vi ng t thit k phi c tnh ton hoc l bng cc phng php phn tch c tha nhn ca ng lc hc cng trnh, nh m hnh phn t hu hn hoc m hnh khi cng, hoc l bng phng php ta tnh n gin ho theo cc

gii hn ca cc iu kin (3) v (8) ca iu ny.

(2)P Khi m hnh ho ng x c hc ca t nn, s mm ho ca phn ng khi bin dng tng

v cc h qu do s tng p lc l rng gy ra di tc dng ca ti trng c chu k phi c xt n.

(3) Vic kim tra n nh c th c tin hnh bng phng php ta tnh n gin ho ti nhng ni a hnh b mt v cu to a tng ca t khng xut hin nhng bin ng bt thng.

(4) Cc phng php ta tnh phn tch n nh ging nh cc phng php ch dn trong 11.5 ca EN 1997-1:2004, ngoi tr vic bao gm c cc lc qun tnh ngang v thng ng i vi mi phn ca khi t v i vi ti trng trng trng tc dng trn nh mI dc.

(5)P Cc lc qun tnh do ng t thit k FH v FV tc ng ln khi t, tng ng vi phng ngang v phng thng ng, trong php phn tch ta tnh c tnh nh sau:

FH = 0,5.S.W (4.1)

FV = 0,5FH nu t s avg/ag ln hn 0,6 (4.2)

FV = 0,33 FH nu t s avg/ag khng ln hn 0,6 (4.3)

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trong :

t s ca gia tc nn thit k ag trn nn loi A vi gia tc trng trng g;

avg gia tc nn thit k theo phng ng;

ag gia tc nn thit k cho nn loi A;

S h s nn, ly theo 3.2.2.2, Phn 1 ca tiu chun ny;

W trng lng khi trt.

H s khuch i a hnh cho ag phi c tnh n theo 4.1.3.2(2).

(6)P iu kin trng thi gii hn khi c kim tra cho mt trt c n nh thp nht.

(7) iu kin trng thi gii hn s dng c th c kim tra bng cch tnh ton chuyn v lu di ca khi trt theo m hnh ng lc n gin ho bao gm mt khi cng trt chng li lc ma st trn sn dc. Trong m hnh ny, tc ng ng t phi l i din ca quan h

lch s thi gian theo 2.2 v da trn gia tc thit k m khng dng bt c h s gim no.

(8)P Cc phng php n gin ho nh phng php ta tnh n gin ha nu trong cc

iu t (3) n (6)P ca mc ny khng c s dng cho cc loi t c kh nng pht

trin p lc nc l rng cao hoc c suy gim ng k v cng di tc dng ca ti trng c chu k.

(9) tng p lc l rng phi c nh gi bng cch s dng cc th nghim thch hp. Khi khng c nhng th nghim ny, v thit k s b, c th d tnh thng qua cc tng quan thc nghim.

4.1.3.4 Kim tra an ton bng phng php ta tnh

(1)P i vi t bo ho trong nhng vng m .S > 0,15, cn xem xt kh nng gim bn v tng p lc l rng do ti trng c chu k theo cc gii hn nu trong 4.1.3.3(8).

(2) i vi cc mt trt n nh nhng c nhiu kh nng tip tc trt bi ng t th s dng cc thng s bn ca nn khi bin dng ln. i vi t ri, s gia tng tun hon

ca p lc nc l rng trong phm vi cc gii hn ca 4.1.3.3 c th c k n bng cch

gim sc khng do ma st thng qua h s p lc nc l rng thch hp, t l vi tng

ln nht ca p lc l rng. tng c th c tnh theo ch dn trong 4.1.3.3(9).

(3) Khng cn p dng gim sc khng ct i vi cc loi t ri gin n mnh, nh cc loi ct cht.

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(4)P Vic kim tra an ton ca mi dc phi c tin hnh theo cc nguyn tc trong EN 1997-1:2004.

4.1.4 Cc loi t c kh nng ho lng

(1)P S gim sc chng ct v/hoc cng do tng p lc nc l rng trong cc vt liu ri bo ho nc trong lc c chuyn ng nn do ng t, n mc lm tng ng k bin dng lu di ca t, hoc dn ti iu kin ng sut hu hiu ca t gn bng 0, m t y tr i c coi l ho lng.

(2)P Phi d tnh kh nng ho lng khi nn t di mng bao gm cc lp ct xp phn b trn din rng hoc cc thu knh ct xp dy, c hoc khng c ht bi hoc st, nm di mc nc ngm, v khi mc nc ngm nm nng. Vic d tnh ny phi c tin hnh khu vc trng (cao mt nn, cao nc ngm) xut hin trong sut tui th ca kt cu.

(3)P Cng tc kho st cn thit cho mc ch ny t nht phi bao gm th nghim xuyn tiu chun ti hin trng (SPT) hoc th nghim xuyn tnh (CPT), cng nh vic xc nh cc ng cong thnh phn ht trong phng th nghim.

(4)P i vi th nghim SPT, gi tr o c NSPT, biu th bng s nht p/30cm, phi c chun ho vi ng sut hu hiu biu kin ca bn thn t bng 100kPa v vi t s ca nng lng va p v nng lng ri t do l thuyt bng 0,6. Vi cc su nh hn 3m, cc gi tr o c NSPT phi gim i 25%.

(5) Vic chun ho i vi nh hng ca p lc bn thn t c th c thc hin bng cch

nhn gi tr o c NSPT vi h s 2/1'

vo )(100/ , trong vo' (kPa) l ng sut hu hiu bn thn t ti su v thi im th nghim SPT. H s chun ho

2/1'vo )(100/ phi c

ly khng nh hn 0,5 v khng ln hn 2.

(6) Vic chun ho nng lng yu cu nhn s nht p thu c trong iu (5) ca mc ny vi mt h s ER/60, trong ER l mt trm ln t s nng lng c trng ca thit b th nghim.

(7) i vi nh trn mng nng, vic d tnh kh nng ho lng c th c b qua khi t ct bo ho nc gp cc su ln hn 15m tnh t mt t.

(8) Nguy c ho lng c th c b qua khi .S < 0,15 v t nht mt trong cc iu kin sau phi c m bo:

Ct c hm lng ht st ln hn 20% vi ch s do PI > 10;

TCXDVN 375 : 2006

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Ct c hm lng ht bi ln hn 35% v ng thi s ba SPT sau khi c chun ho vi cc nh hng ca p lc bn thn t v vi t s nng lng 20)06(N1 > .

Ct sch, vi s ba SPT sau khi c chun ho vi p lc bn thn t v vi t s nng lng 30)06(N1 > .

(9)P Nu nguy c ho lng khng th b qua th t nht n phi c nh gi bng cc phng php tin cyca ngnh a k thut, da trn tng quan gia cc quan trc ti hin trng v ng sut ct lp c bit l gy ra ho lng trong nhng trn ng t xy ra.

(10) Cc biu ho lng thc nghim minh ho tng quan hin trng di mt nn ng vi cc o c ti thc a c cho trong Ph lc B. Trong phng php ny, ng sut ct do

ng t e c th c tnh theo biu thc n gin ho sau: e = 0,65.S. vo (4.4)

trong :

vo p lc ton phn do bn thn t, cc bin s khc nh trong cc biu thc t (4.1) n (4.3). Biu thc ny khng p dng cho chiu su ln hn 20m.

(11)P Nu s dng phng php tng quan hin trng th t phi c coi l nhy vi ho lng khi ng sut ct do ng t gy ra vut qu mt phn ca ng sut ti hn c bit l gy ho lng trong cc trn ng t trc .

Ghi ch: Gi tr khuyn ngh l = 0,8, bao gm h s an ton bng 1,25.

(12)P Nu t c thy l d b ho lng v cc hiu ng tip sau c th nh hng n sc chu ti hoc n nh ca mng th cn c bin php m bo tnh n nh ca mng, nh gia c nn v cc ( truyn ti trng xung cc lp khng d b ho lng).

(13) Vic gia c nn chng li ha lng c th l m cht t tng sc khng xuyn vt khi phm vi nguy him, hoc l s dng bin php thot nc gim p lc nc l rng do chn ng nn gy ra.

Ghi ch: Kh nng m cht ch yu c quyt nh bi hm lng hn mn v su ca t.

(14) Vic s dng ch ring mng cc cn c cn nhc cn thn do ni lc ln pht sinh trong cc do mt s chng ca t trong phm vi mt lp hoc nhiu lp t ho lng, v do s thiu chun xc khng th trnh khi khi xc nh v tr v b dy ca lp hoc cc lp .

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4.1.5 ln qu mc ca t di ti trng c chu k

(1)P Tnh nhy ca t nn i vi s nn cht v i vi ln qu mc do ng sut c chu k pht sinh khi ng t phi c xt n khi c cc lp phn b trn din rng hoc cc thu knh dy ca ct xp v bo ho nc gp su nh.

(2) ln qu mc cng c th xy ra trong cc lp t st rt yu do sc khng ct gim theo

chu k lp di rung ko di ca nn.

(3) Kh nng tng cht v ln ca cc loi t nu trn phi c nh gi bng cc phng php hin c ca a k thut cng trnh, nu cn c th da trn th nghim trong phng vi ti trng tnh v ti trng c chu k cho cc mu i din ca vt liu cn nghin cu.

(4) Nu ln do nn cht hoc s suy gim ( bn) theo chu k c kh nng nh hng n n nh ca mng th cn xt n phng php gia c nn.

4.2 Kho st v nghin cu v nn

4.2.1 Cc tiu ch chung

(1)P Vic kho st v nghin cu v vt liu nn mng trong vng ng t phi tun theo cc nguyn tc chung nh i vi vng khng c ng t, nh nh ngha trong phn 3, EN 1997-1:2004.

(2) Tr cc nh thuc tm quan trng cp I, trong kho st hin trng nn c th nghim xuyn tnh, c th o p lc l rng, v n cho php ghi lin tc cc c trng c hc ca t theo su.

(3) Cc kho st b sung vi nh hng khng chn c th c yu cu trong cc trng hp

c ch dn trong 4.1 v 4.2.2.

4.2.2 nh dng nn t i vi tc ng ng t

(1)P Cc s liu a k thut hoc a cht cho hin trng xy dng phi cho php xc

nh loi nn trung bnh v/hoc ph phn ng tng ng, nh nh ngha trong 3.1 v 3.2,

Phn 1 ca tiu chun ny.

(2) Nhm mc ch ny, cc s liu hin trng c th c kt hp vi cc s liu t cc vng ln cn c c im a cht tng t.

(3) Phi tham kho cc bn tiu vng hoc tiu ch ng t sn c, vi iu kin l chng

tun theo (1)P ca iu ny v da trn cc kho st t nn ti a im xy dng cng

trnh.

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(4)P Mt ct vn tc sng ct s trong nn c xem l ng tin cy nht d bo cc c trng ph thuc vo a im do tc ng ng t ti cc a im .

(5) Th nghim hin trng xc nh mt ct vn tc sng ct s bng phng php a vt l trong l khoan nn c s dng cho cc kt cu quan trng nm trong vng ng t mnh, c bit l trong cc dng nn loi D, S1 hoc S2.

(6) i vi tt c cc trng hp khc, khi cc chu k dao ng t nhin ca t cn c xc

nh, mt ct ca s c th c d tnh bng cc tng quan thc nghim khi s dng sc khng xuyn hin trng hoc cc c trng a k thut khc v cn ch n s phn tn ca cc tng quan .

(7) cn bn trong ca t nn c o bng cc th nghim hin trng hoc th nghim trong phng thch hp. Trong trng hp thiu cc php o trc tip, v nu tch s ag.S nh hn 0,1g (hay 0,98m/s2) th t s cn ly bng 0,03. t kt, t ximng ho v mm c th cn c xem xt ring bit.

4.2.3 S ph thuc ca cng v gim chn ca t vo mc bin dng

(1)P S khc nhau gia cc gi tr ca s khi bin dng nh, nh cc gi tr c o trong th nghim hin trng, v cc gi tr ph hp vi mc bin dng do ng t thit k gy ra phi c xt ti trong tt c cc tnh ton lin quan n cc c trng ng lc ca t trong iu kin n nh.

(2) i vi cc iu kin t nn a phng thuc loi C hoc D vi mc nc ngm nng v khng c thnh phn no c ch s do PI > 40, khi thiu cc d liu c th th c th s

dng n cc h s gim s cho trong Bng 4.1. i vi cc a tng cng hn v mc nc ngm su hn th lng gim phi theo t l nh hn (v khong bin thin phi c gim i).

(3) Nu tch s ag.S bng hoc ln hn 0,1g (hay 0,98m/s2 ) th nn dng cc t s cn bn trong

cho trong Bng 4.1, khi khng c cc php o c th.

Bng 4.1 - T s cn trung bnh ca t v cc h s gim

trung bnh ( mt lch tiu chun) cho vn tc sng ct s v m un ct G trong phm vi chiu su 20m.

T s gia tc nn ag.S T s cn max,s

s

maxGG

0,10

0,20

0,30

0,03

0,06

0,10

0,90(0,07) 0,70(0,15) 0,60(0,15)

0,80(0,10) 0,50(0,20) 0,36(0,20)

s, max gi tr s trung bnh khi bin dng nh (

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Gmax mun ct trung bnh khi bin dng nh.

GHI ch: Thng qua vic cng tr mt khong lch tiu chun, ngi thit k c th a vo cc lng khc nhau ca an ton, tu thuc vo cc h s nh cng v phn lp ca t.

V d cc gi tr ca max,s

s

v maxGG

cao hn gi tr trung bnh c th c s dng cho a

tng cng hn, cc gi tr ca max,s

s

v maxGG

di gi tr trung bnh s dng cho a tng mm hn.

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5 H nn mng

5.1 Cc yu cu chung

(1)P Ngoi cc yu cu chung ca EN 1997-1:2004, mng ca kt cu trong vng ng t phi tun theo cc yu cu di y.

a) Cc lc lin quan t kt cu bn trn phi c truyn xung nn m khng gy ra bin

dng lu di ng k theo cc tiu ch trong 5.3.2.

b) Cc bin dng nn do ng t gy ra p ng cc yu cu i vi chc nng c bn ca

kt cu.

c) Mng phi c nhn thc, thit k v xy dng theo cc quy tc ca 5.2 v cc bin php

ti thiu ca 5.4 c gng hn ch cc ri ro gn lin vi s hiu bit cha y v ng

x khng lng trc c ca ng t.

(2)P Cn xt n tnh ph thuc vo mc bin dng ca cc tham s ng lc ca t (xem

4.2.3) v n cc h qu lin quan n bn cht c chu k ca ti trng ng t. Cn xt

n cc tham s ca t gia c ti ch hoc t thay th t nguyn th l cn thit do cht ca chng khng m bo hoc do tnh nhy ca chng i vi hin tng ha lng hoc vi s tng cht.

(3) Khi c l do thch ng (hoc khi cn thit), vt liu nn hoc cc h s bn khc vi cc

h s nu trong 3.1(3) c th c s dng, vi iu kin l chng ph hp vi cng mc

an ton.

GHI ch: V d nh cc h s bn c p dng cho kt qu th nghim gia ti cc.

5.2 Cc quy nh i vi thit k c s

(1)P Trong trng hp cc kt cu khng phi cu hay ng ng, cc dng mng hn hp nh mng cc kt hp vi mng nng ch c s dng nu c s nghin cu ring chng t gii php ny l thch hp. Cc dng mng hn hp c th c s dng cho cc b phn c lp v tnh ng lc trong cng kt cu.

(2)P Trong vic la chn loi mng, cn xt n cc im di y:

a) Mng phi cng truyn cc tc ng cc b t kt cu bn trn xung nn mt cch

ng u.

b) nh hng ca cc chuyn v tng i theo phng ngang gia cc cu kin thng ng phi c xt n khi la chn cng ca mng trong phm vi mt phng ngang ca n.

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c) Nu gi thit bin ca chuyn dch do ng t gim theo chiu su th iu ny phi c chng minh bng mt nghin cu thch hp, v khng c trng hp no t s gia tc

cao nht nh hn mt phn p ca tch s .S ti mt nn.

Ghi ch: Gi tr khuyn ngh l p = 0,65.

5.3 Cc hiu ng tc ng thit k

5.3.1 Mi quan h trong thit k kt cu

(1)P Cc kt cu tiu tn nng lng. Cc hiu ng ca tc ng ng t i vi mng ca kt cu tiu tn nng lng phi da trn vic xem xt kh nng chu lc thit k c tnh n kh nng vt cng . Vic nh gi cc hiu ng nh vy phi tun theo cc iu khon trong cc mc tng ng ca tiu chun ny. Ring i vi cc cng trnh dng nh th p

dng cc yu cu trong 4.4.2.6(2)P, Phn 1 ca tiu chun ny.

(2)P Cc kt cu khng tiu tn nng lng. Cc hiu ng ca tc ng ng t vi mng ca kt cu khng tiu tn nng lng ly t cc kt qu tnh ton/phn tch trong iu kin thit

k ng t khng cn xt n kh nng chu lc thit k. Tham kho thm 4.4.2.6(3), Phn

1 ca tiu chun ny.

5.3.2 Truyn cc hiu ng ca tc ng ng t ln nn

(1)P h mng c th ph hp vi 5.1(1)P(a), cc ch tiu sau phi c chp nhn v truyn

lc ngang v lc php tuyn/mmen un xung nn. i vi cc v tr, cn xt thm cc ch

tiu c quy nh trong 5.4.2.

(2)P Lc ngang. Lc ct thit k theo phng ngang VEd c truyn theo cc c ch sau:

a) Bng sc khng ct thit k FRd gia y theo phng ngang ca mng hoc ca bn mng

vi nn nh m t trong 5.4.1.1;

b) Bng sc khng ct thit k gia cc mt ng ca mng v nn;

c) Bng sc khng thit k do p lc t mt bn ca mng, theo cc gii hn v cc iu

kin nh m t trong 5.4.1.1, 5.4.1.3 v 5.4.2.

(3)P Cho php ly t hp ca sc khng ct vi nhiu nht l 30% sc khng do p lc b ng ca t khi c huy ng hon ton.

(4)P Lc php tuyn v mmen un. Lc php tuyn thit k NEd v mmen un MEd c truyn xung nn theo mt c ch hoc theo t hp cc c ch sau:

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a) Bng tr thit k ca phn lc theo phng thng ng y mng;

b) Bng tr thit k ca cc mmen un c pht trin bi sc khng ct thit k theo phng ngang gia mt bn ca cc cu kin mng su (mng hp, mng cc, ging chm) v nn,

theo cc gii hn v cc iu kin nh m t trong 5.4.1.3 v 5.4.2;

c) Bng tr thit k ca sc khng ct theo phng thng ng gia cc mt bn ca cc cu kin mng chn trong t v mng su (mng hp, mng cc, tr v ging chm) v nn.

5.4 Cc ch tiu kim tra v xc nh kch thc

5.4.1 Mng nng hoc mng chn trong t

(1)P Cc tiu ch v kim tra v v xc nh kch thc sau y c p dng i vi mng nng hoc mng chn trong t t trc tip ln nn bn di.

5.4.1.1 Mng (thit k theo trng thi cc hn)

(1)P Theo cc ch tiu thit k ca trng thi cc hn, mng phi c kim tra sc khng trt v kh nng chu ti.

(2)P Ph hoi do trt. Trong trng hp y mng nm trn mc nc ngm, dng ph hoi ny

c khng li do ma st, v theo cc iu kin quy nh trong (5) ca iu ny, thng qua

p lc ngang ca t.

(3) Khi khng c cc nghin cu c th hn th sc khng do ma st thit k ca mng nm

trn mc nc ngm, FRd, c th c tnh ton t biu thc sau:

Rd Ed

M

tgF N = (5.1)

trong :

NEd lc php tuyn thit k ln y mng nm ngang;

gc ma st gia b mt kt cu v nn ti y mng. Gi tr ny c th nh gi theo 6.5.3 ca EN 1997-1:2004;

M h s ring ca tham s vt liu, ly bng gi tr p dng cho tg (xem 3.1(3)).

(4)P Trong trng hp mng nm di mc nc ngm, sc khng ct thit k phi c nh gi trn c s sc khng ct khng thot nc, theo 6.5.3 ca EN 1997-1:2004.

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(5) Sc khng theo phng ngang thit k Epd do p lc t ln mt bn ca mng c th c

tnh n nh quy nh trong 5.3.2, vi iu kin p dng cc bin php thch hp ti hin

trng, nh lm cht phn t lp li mt hng mng, chn tng mng thng ng vo t, hoc b tng mng p trc tip vo vch t sch v thng ng.

(6)P m bo khng xy ra ph hoi do trt y theo phng ngang, cn tho mn biu thc sau:

VEd FRd + Epd (5.2)

(7) Trong trng hp mng nm trn mc nc ngm v c hai iu kin sau u tho mn:

cc tnh cht ca t khng thay i trong qu trnh ng t;

hin tng trt khng gy nh hng xu i vi cc cng nng ca bt k ng ng huyt mch no (nh ng ng nc, kh, cng hoc ng dy thng tin lin lc) lin kt vi kt cu;

th s trt c th xy ra trong mt phm vi gii hn cho php. Mc trt phi hp l khi ng x tng th ca kt cu c xem xt.

(8)P Ph hoi do vt kh nng chu ti. tho mn yu cu ca 5.1(1)Pa), kh nng chu ti

ca mng phi c kim tra vi t hp cc nh hng ca tc ng NEd, VEd, v MEd.

GHI ch: kim tra kh nng chu ti khi ng t ca mng, c th s dng cc biu thc v ch tiu chung nh a ra trong Ph lc thng tin A. N cho php xt n nghing v

lch tm do lc qun tnh trong kt cu cng nh cc nh hng c th c ca cc lc qun tnh trong chnh nn t chu ti.

(9) Cn ch n thc t l c mt s loi t st nhy c th b gim sc khng ct, v t ri d b nh hng bi p lc nc l rng ng do ti trng c chu k cng nh s tiu tn p lc l rng t cc lp bn di sau khi xy ra ng t.

(10) Vic nh gi kh nng chu ti ca t di ti trng ng t phi tnh n cc c ch gim bn v cng c th xy ra ngay c cc mc bin dng tng i nh. Nu c tnh n cc hin tng ny th cc h s c trng vt liu c th c ly thp i. Nu khng,

nn s dng cc gi tr c k n trong 3.1(3).

(11) Hin tng tng p lc l rng di ti trng c chu k phi c tnh n, hoc bng cch xem xt nh hng ca n i vi sc khng ct khng thot nc (trong php phn tch ng sut ton phn) hoc i vi p lc nc l rng (trong php phn tch ng sut hu hiu).

i vi nhng kt cu vi h s tm quan trng I ln hn 1,0, ng x phi tuyn ca t phi c xt n khi xc nh bin dng lu di c th xy ra trong thi gian ng t.

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5.4.1.2 Cc lin kt theo phng ngang ca mng

(1)P Ging vi 5.2, cc nh hng ca tc ng gy ra trong kt cu bi cc chuyn v tng i

theo phng ngang ca mng phi c nh gi v thc hin cc bin php thch hp iu chnh thit k.

(2) i vi nh, yu cu quy nh trong (1)P ca iu ny c coi l tho mn nu cc mng

c t trn cng mt phng ngang v cc dm ging hoc cc bn mng c b tr cao trnh mng hoc i cc. Cc bin php ny khng cn thit trong cc trng hp sau: a) vi nn loi A, v b) trong cc trng hp kh nng xy ra ng t l thp vi nn loi B.

(3) Cc dm ca tng di ca nh c th c coi l dm ging vi iu kin l chng nm trong phm vi 1,0 m tnh t mt y ca mng hoc i cc. Mt bn mng c th thay th cc dm ging, vi iu kin l n cng c t trong phm vi 1,0m t mt y ca mng hoc i cc.

(4) bn chu ko cn thit ca cc cu kin lin kt ny c th c nh gi bng cc phng php n gin ha.

(5)P Nu khng c cc quy nh hoc phng php chnh xc hn th cc lin kt mng phi

c coi l y khi tt c cc quy nh cho trong (6) v (7) ca iu ny c tho mn.

(6) Dm ging

Nn p dng cc bin php di y:

a) Cc dm ging phi c thit k chu c lc dc, c xt n c lc ko v lc nn, bng:

0,3SNEd i vi nn loi B

0,4SNEd i vi nn loi C

0,6SNEd i vi nn loi D

trong

NEd gi tr trung bnh ca cc lc dc trc thit k ca cc cu kin thng ng c lin kt trong iu kin thit k khng chn;

b) Thp dc phi c neo chc chn vo thn mng hoc vo cc dm ging khc lin kt vi n.

(7) Bn mng

Cc bin php di y phi c p dng:

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a) Cc dm ging phi c thit k chu lc dc trc bng cc gi tr trong (6)a) ca

iu ny.

b) Thp dc ca vng ging phi c neo chc chn vo thn ca mng hoc vo cc bn lin tc.

5.4.1.3 Mng b

(1) Tt c cc iu trong 5.4.1.1 cng c th p dng cho mng b, nhng vi cc iu kin hn

ch sau:

a) Kh nng chu ma st tng th c th c tnh n trong trng hp bn mng n. i vi cc li n gin ca dm mng, mt din tch mng tng ng c th c xt ti mi giao im.

b) Cc dm mng v/hoc bn mng c th c coi nh cc ging lin kt; cc quy nh v kch thc ca chng c th p dng cho chiu rng hiu dng tng ng vi chiu rng ca dm mng hoc chiu rng ca bn bng 10 ln chiu dy ca n.

(2) Mng b cng c th kim tra nh tng trong phm vi mt phng ca n, di tc dng ca cc lc qun tnh ngang ca n v cc lc ngang do kt cu bn trn gy ra .

5.4.1.4 Mng hp

(1) Tt c cc iu khon ca 5.4.1.3 cng c th c p dng cho mng hp. Ngoi ra, kh

nng chu ti ca t mt hng nh quy nh trong 5.3.2(2) v 5.4.1.1(5), c th c xt

n cho tt c cc loi t, theo cc gii hn quy nh.

5.4.2 Cc v tr

(1) Cc v tr phi c thit k chu 2 dng nh hng ca tc ng.

a) Cc lc qun tnh t kt cu bn trn. Nhng lc ny, c t hp vi ti trng tnh, cho cc

gi tr thit k NEd, VEd, MEd nh quy nh trong 5.3.2.

b) Cc lc ng pht sinh t bin dng ca t xung quanh do sng ng t i qua.

(2)P Kh nng chu ti trng ngang ti hn ca cc phi c kim tra theo cc nguyn tc ca

7.7 ca tiu chun ny.

(3)P Cc phn tch xc nh ni lc trong cc, cng nh cc chuyn v v gc xoay ti u cc phi da trn cc m hnh ri rc hay lin tc c th m t li mt cch chn thc (c th l gn ng):

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cng chu un ca cc;

Phn lc ca t dc thn cc, cng vi s xem xt cc nh hng ca ti trng c chu k v mc bin dng trong t;

Cc nh hng do tng tc ng gia cc cc (cn gi l hiu ng ng ca nhm cc);

Bc t do ca gc xoay ti/ca i cc, hoc ca lin kt gia cc v kt cu.

GHI ch: tnh ton cng ca cc, cc biu thc cho trong Ph lc tham kho C c s dng nh hng dn.

(4)P Sc khng mt bn ca cc lp t d ho lng hoc gim bn ng k phi c b qua.

(5) Nu s dng cc cc xin th phi thit k sao cho chng chu c ti trng dc trc cng nh chu un mt cch an ton.

GHI ch: Khng nn dng cc cc xin truyn ti trng ngang ln t.

(6)P Cc mmen un pht trin do tng tc ng hc ch c tnh ton khi tt c cc iu kin sau xy ra ng thi:

Mt ct t nn thuc loi D, S1 hoc S2 v bao gm cc lp lin tip c cng thay i t ngt;

Cng trnh nm trong vng c kh nng xy ra ng t trung bnh hoc cao, ngha l tch s ag.S vt qu 0,10g (hay 0,98m/s2), v kt cu thuc tm quan trng cp III hoc IV.

(7) V nguyn tc cc phi c thit k lm vic trong phm vi n hi, nhng trong mt s trng hp c th cho php pht trin khp do ti nh cc. Cc vng c kh nng hnh

thnh khp do phi c thit k theo 5.8.4, Phn 1 ca tiu chun ny.

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6 tng tc gia t v kt cu

(1)P Cc hiu ng ca tng tc ng lc hc t-kt cu phi c tnh n i vi:

a) Cc kt cu m hiu ng P- (hiu ng bc 2) ng vai tr quan trng;

b) Cc kt cu vi mng khi ln hoc t su nh tr cu, ging chm ngoi khi v silo;

c) Cc kt cu cao mnh nh thp v ng khi, nm trong ni dung ca EN 1998-6:2004;

d) Cc kt cu t trn cc lp t rt mm, vi vn tc sng ct trung bnh s,max (nh nh ngha trong Bng 4.1) nh hn 100m/s, nh cc lp t thuc dng nn S1.

Ghi ch: Thng tin v cc hiu ng chung v tm quan trng ca tng tc ng lc hc gia kt cu v t c cho trong Ph lc tham kho D.

(2)P Cc hiu ng ca tng tc t - kt cu ca cc phi nh gi theo 5.4.2 i vi tt c cc

kt cu.

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25

7 kt cu tng chn

7.1 Cc yu cu chung

(1)P Cc kt cu tng chn phi c thit k thc hin c cc chc nng ca chng trong v sau khi ng t m khng xy ra s h hng kt cu ln no.

(2) Chuyn v khng phc hi, di dng trt v nghing, trong hin tng nghing do cc bin dng khng phc hi ca nn t, c th chp nhn c nu chng ph hp vi cc yu cu v cng nng v/hoc thm m.

7.2 La chn v nhng iu lu chung v thit k

(1)P Vic la chn dng kt cu phi da trn cc iu kin lm vic bnh thng, theo cc nguyn tc chung trong chng 9, EN 1997-1:2004.

(2)P Cn ch rng vic tun theo cc yu cu b sung v ng t c th dn n vic iu

chnh v i khi dn n s la chn dng kt cu thch hp hn .

(3)P Vt liu p sau kt cu phi c chn cp phi v m cht cn thn ti hin trng t c tnh lin tc cng cao cng tt vi khi t nguyn th.

(4)P Cc h thng thot nc pha sau kt cu phi c kh nng chu c cc dch chuyn nht thi v lu di m khng nh hng n cc chc nng ca chng.

(5)P c bit trong trng hp t ri c cha nc, h thng thot nc phi c hiu qu c vi phn di mt ph hoi c th xy ra pha sau kt cu.

(6)P Phi m bo rng khi t c chng c d tr an ton ln chng li s ho lng di tc ng ng t thit k.

7.3 Cc phng php phn tch

7.3.1 Cc phng php chung

(1)P Bt k phng php no c thit lp trn c s cc qu trnh ca ng lc hc kt cu v t, v cng vi cc kinh nghim v cc quan trc, v nguyn tc l c th chp nhn c trong vic nh gi an ton ca kt cu tng chn t.

(2) Cc vn sau y cn c xt n:

a) ng x phi tuyn ni chung ca t trong tng tc ng lc hc vi kt cu tng chn;

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b) Cc hiu ng qun tnh i km vi vi khi lng ca t, ca kt cu, v ca tt c cc ti trng trng lc c th tham gia vo qu trnh tng tc;

c) Cc hiu ng thu ng gy ra bi s c mt ca nc trong t pha sau tng v/hoc bi nc mt ngoi ca tng;

d) S tng thch gia cc bin dng ca t, tng v ging (nu c).

7.3.2 Cc phng php n gin ho: phn tch ta tnh

7.3.2.1 Cc m hnh c bn

(1)P M hnh c bn p dng cho phng php phn tch ta tnh phi bao gm kt cu tng chn v mng ca n, lng th t pha sau kt cu c d kin trong trng thi cn bng gii hn ch ng (nu kt cu mm) cng nh bt k ti trng no tc dng ln lng th t v c th l c khi t chn tng, c xem nh trong trng thi cn bng b ng.

(2) c c trng thi ch ng ca t, mt dch chuyn ln ca tng cn phi xy ra trong sut qu trnh ng t thit k, dch chuyn ny c th c hnh thnh i vi kt cu mm khi b un, v i vi cc kt cu trng lc khi b trt hoc xoay. i vi mc dch chuyn ca tng cn thit pht trin trng thi gii hn ch ng, ngh xem 9.5.3 ca EN 1997-1:2004.

(3) Vi cc kt cu cng, nh tng tng hm hoc tng trng lc nm trn nn hoc trn cc s pht sinh p lc ln hn p lc ch ng, v s l hp l hn nu gi thit t trng

thi ngh nh trnh by E.9. iu ny cng c gi thit cho tng chn c neo v khng

cho php dch chuyn.

7.3.2.2 Tc ng ng t

(1)P Trong phng php ta tnh, tc ng ng t phi c m t bng h cc lc tnh tc dng theo phng nm ngang v phng thng ng, ly bng tch ca lc trng trng v h s ng t.

(2)P Tc ng ng t theo phng thng ng phi c xem xt tc dng hng ln trn hoc hng xung di to ra cc hiu ng bt li nht.

(3) i vi mt vng c ng t, cng ca cc lc ng t tng ng ph thuc vo gi tr chuyn v lu di c th chp nhn c v nm trong gii hn cho php ca gii php kt cu c la chn.

(4)P Khi thiu cc nghin cu c th, cc h s ng t theo phng ngang (kh) v phng ng (kv) nh hng n tt c cc khi lng phi c ly l:

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r S =hk

(7.1)

hv kk 5,0= nu avg/ag ln hn 0,6 (7.2)

kv = 0,33kh cho cc trng hp ngc li (7.3)

trong :

h s r ly cc gi tr trong Bng 7.1, ph thuc vo dng kt cu tng chn. Vi cc tng

khng cao qu 10m, h s ng t c coi nh khng thay i trn sut chiu cao tng.

Bng 7.1 - Cc gi tr ca h s r tnh ton h s ng t theo phng ngang

Dng tng chn r

Tng trng lc vi u tng t do, c th chp nhn mt chuyn v n dr =

300.S (mm) Tng trng lc vi u tng t do c th chp nhn mt chuyn v ln n dr =

200.S (mm) Tng b tng ct thp chu un, tng c neo hoc chng, tng b tng ct thp trn cc thng ng, tng tng hm b hn ch chuyn v v m cu

2

1,5

1

(5) Khi c cc loi t ri bo ho nc v d pht trin p lc nc l rng cao th:

a) H s r ca Bng 7.1 nn ly khng ln hn 1,0.

b) H s an ton chng ho lng khng nn nh hn 2.

GHI ch: Gi tr h s an ton bng 2 thu c t vic p dng 7.2(6)P trong khun kh ca phng php n gin ho 7.3.2.

(6) Vi kt cu tng chn cao trn 10m v vi cc thng tin b sung cho h s r, xem E.2.

(7) Tr tng trng lc, hiu ng ca gia tc theo phng thng ng c th b qua i vi kt cu tng chn.

7.3.2.3 p lc thit k ca t v nc

(1)P Tng lc thit k tc dng ln tng trong trng hp ng t phi c tnh ton c xt

n iu kin cn bng gii hn ca m hnh c m t trong 7.3.2.1.

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(2) Lc ny c th c nh gi theo Ph lc E.

(3) Lc thit k c cp n trong (1)P ca iu ny phi c coi l hp lc ca p lc tnh

v ng ca t.

(4)P Trong trng hp khng c cc nghin cu chi tit v cng tng i, dng dch chuyn v khi lng tng i ca tng chn th im t ca lc do p lc ng ca t nm gia chiu cao ca tng.,

(5) Vi cc tng xoay t do xung quanh chn tng th lc ng c th xem nh t ti cng im vi lc tc dng tnh.

(6)P p lc phn b trn tng do tc ng tnh v ng to vi phng vung gc ca tng mt gc khng ln hn (2/3) i vi trng thi ch ng v bng 0 i vi trng thi b ng.

(7)P i vi t nm di mc nc ngm cn c s phn bit gia cc iu kin d thm nc di ti trng ng, trong nc bn trong c th chuyn ng t do trong ct t, v cc iu kin khng thm nc, trong v c bn khng xy ra thot nc di tc ng ng t.

(8) i vi hu ht cc iu kin thng thng v i vi cc loi t c h s thm nh hn 5.10-4 m/s, nc l rng khng t do di chuyn trong khung t, tc ng ng t xy ra trong iu kin v c bn l khng thot nc v t c th c xem nh mi trng mt pha.

(9)P Vi cc iu kin khng thm thy ng, tt c cc iu khon trc phi c p dng, vi iu kin l khi lng th tch ca t v h s ng t theo phng ngang c iu chnh thch hp.

(10) Cc iu chnh i vi iu kin khng thm thy ng c th c tin hnh theo E.6 v E.7.

(11)P Vi t p thm thy ng, cc hiu ng gy ra bi tc ng ng t trong t v trong nc phi c gi thit l cc hiu ng c lp.

(12) Do , p lc nc thu ng nn c cng vo p lc nc thu tnh theo E.7. im t

ca p lc nc thu ng c th c ly ti mt su di nh ca lp bo ho bng 60% chiu cao ca lp .

7.3.2.4 p lc thu ng ln mt ngoi ca tng

(1)P Bin ng ln nht (tng hoc gim) ca p lc (so vi p lc thu tnh hin hu) do s dao

ng ca nc trn mt h ca tng cn c xt n.

(2) p lc ny c th c nh gi theo E.8.

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7.4 Kim tra bn v n nh

7.4.1 Tnh n nh ca nn t

(1)P Cc kim tra di y cn c thc hin

n nh tng th;

Ph hoi cc b ca t.

(2)P Vic kim tra n nh tng th phi c tin hnh theo cc quy tc trong 4.1.3.4.

(3)P Kh nng chu lc ti hn ca nn phi c kim tra v ph hoi do trt v v mt mt kh

nng chu ti (xem 5.4.1.1).

7.4.2 Neo

(1)P Cc loi neo (bao gm oan cp t do, bu neo, cc u neo v cc c cu kho neo) phi c bn v chiu di m bo s cn bng ca lng th t trong iu kin ng t

(xem 7.3.2.1), ng thi phi c kh nng chu cc bin dng ca nn do ng t gy ra.

(2)P bn ca neo phi c ly theo cc quy nh trong EN 1997-1:2004 ng vi cc trng thi gii hn thit k ng v di hn.

(3)P Cn m bo rng t neo duy tr c bn yu cu theo chc nng neo trong sut qu trnh ng t thit k v c bit phi c d tr an ton chng li hin tng ho lng.

(4)P Khong cch Le gia neo v tng phi vt qu khong cch Ls c yu cu cho cc ti trng phi ng t.

(5) Khong cch Le, vi cc neo ngm trong t c cc c trng tng t vi t pha sau tng v vi cc iu kin v cao mt t, c th nh gi theo biu thc sau:

Le = Ls(1+1,5.S) (7.4)

7.4.3 bn kt cu

(1)P Cn chng t rng, di t hp ca tc ng ng t cng vi cc ti trng khc c th pht sinh, c th t c trng thI cn bng m khng vt bn thit k ca tng v cc cu kin chng .

(2)P t c mc ch , cn xem xt cc trng thi gii hn thch hp cho ph hoi kt cu trong 8.5 ca EN 1997-1:2004.

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(3)P Tt c cc cu kin phi c kim tra m bo rng chng tho mn iu kin sau:

Rd > Ed (7.5)

trong :

Rd gi tr thit k ca bn ca cu kin, c nh gi nh trong cc trng hp khng ng t;

Ed gi tr thit k ca cc hiu ng tc ng, thu c t cc kt qu phn tch trnh by

trong 7.3.

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ph lc A (tham kho)

Cc h s khuch i a hnh

A.1 Ph lc ny a ra mt s h s khuch i n gin ho cho tc ng ng t dng trong

php kim tra n nh mi dc ca t. Cc h s ny, k hiu l ST, l gi tr gn ng ban u c xem xt c lp vi chu k dao ng c bn v do , nhn ln nh mt h s t l

khng i cc to ca ph phn ng thit k n hi c cho trong Phn 1 ca tiu

chun ny. Cc h s khuch i ny phi c u tin p dng cho cc mi dc c s thay

i a hnh bt thng theo 2 chiu, nh cc nh ko di v vch c chiu cao trn 30m.

A.2 Vi cc gc dc trung bnh nh hn 150 th cc hiu ng v a hnh c th b qua, cn trong

trng hp c im a hnh cc b thay i rt bt thng th cn c cc nghin cu ring. Vi cc gc ln hn th p dng hng dn sau:

a) Cc vch v sn dc c lp. S dng gi tr ST 1,2 cho cc v tr gn cnh nh.

b) Cc nh c chiu rng nh hn nhiu so vi chiu rng chn . Nn s dng gi tr ST 1,4

gn nh ca cc mi dc vi gc dc trung bnh ln hn 300 v gi tr ST 1,2 cho cc gc dc nh hn;

c) S tn ti ca cc lp t ri rc trn b mt. Khi xut hin cc lp t ri rc trn b mt,

gi tr nh nht ST cho trong a) v b) nn tng thm t nht 20%;

d) S bin thin khng gian ca h s khuch i. Gi tr ca ST c th c gi thit l gim tuyn tnh theo chiu cao k t vch hoc nh, v c ly bng n v ti chn mi dc.

A.3 Ni chung, s khuch i ng t cng gim nhanh chng theo chiu su trong phm vi

nh. Do , cc nh hng a hnh c tnh n vi cc phn tch n nh l ln nht v hu ht ch l trn b mt dc theo cnh ca nh, v nh hn nhiu trn cc mt trt su, ni m b mt ph hoi i qua gn chn mi dc. Trong trng hp th 2, nu p dng phng php phn tch ta tnh th cc nh hng a hnh c th c b qua.

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ph lc b (bt buc)

Cc biu thc nghim phn tch ho lng n gin ho

B.1 Tng qut.

Cc biu thc nghim dng phn tch ho lng n gin ho trnh by tng quan hin trng gia cc kt qu o hin trng v cc ng sut ct lp c bit l nguyn nhn gy ra hin tng ho lng trong cc trn ng t trc . Trn trc ngang ca cc biu l mt c trng ca t o c ti hin trng, nh sc khng xuyn c

chun ho hoc vn tc truyn sng ct s, cn trn trc ng l ng sut ct lp do ng t e, thng c chun ho vi p lc bn thn hu hiu v0. ng cong gii hn ca sc khng lp c hin th trn tt c cc biu , chia thnh vng khng ho lng (nm pha bn phi) vi vng ho lng c th xy ra (nm pha bn tri v pha trn ca ng cong). i khi c hn mt ng cong c a ra, v d tng ng vi cc loi t c cc thnh phn ht mn hoc c cc cng ng t khc nhau.

Ngoi tr trng hp s dng sc khng xuyn tnh, khng nn p dng cc ch tiu ho lng thc nghim khi kh nng ho lng xy ra trong cc lp hoc cc va t dy khng qu vi chc cm.

Khi hm lng cui si kh cao nhng cc s liu quan trc cn cha thit lp mt biu ho lng ng tin cy th khng th loi tr kh nng ho lng.

B.2 Cc biu da trn ch s SPT

Biu trn Hnh B.1 nm trong s cc biu c s dng rng ri nht cho ct sch v ct bi. Ch s SPT c chun ho vi p lc bn thn t v vi t s nng lng N1(60)

theo cch m t trong 4.1.4.

Ho lng dng nh khng xy ra di mt ngng no ca e , v ng x ca t l n hi v khng c s tch ly p lc nc l rng. V vy ng cong gii hn khng c ngoi

suy v gc to . p dng tiu ch ny cho ng t c cng khc vi SM = 7,5,

trong SM l cng sng mt, th nn nhn cc to ca cc ng cong trong Hnh B.1 vi h s CM nu trong Bng B.1.

Bng B.1 - Cc gi tr ca h s CM

SM CM 5,5 2,86 6,0 2,20 6,5 1,69

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7,0 1,30 8,0 0,67

B.3 Cc biu da trn sc khng xuyn tnh CPT. Da trn nhiu nghin cu v s tng quan gia sc khng xuyn tnh CPT v sc khng ca t i vi hin tng ho lng, cc

biu c dng nh Hnh B.1 c thit lp. Nhng tng quan trc tip nh vy nn

c u tin hn nhng tng quan gin tip s dng mi quan h gia ch s SPT v sc khng xuyn tnh CPT.

B.4 Cc biu da trn vn tc sng ct s. c trng ny ha hn nh mt ch tiu hin trng nh gi kh nng ho lng trong t thuc loi kh ly mu (nh ct bi hoc ct) hoc

kh xuyn qua (nh cui). Gn y c nhng tin b ng k trong vic o s ti hin trng. Tuy nhin, tng quan gia s v sc khng ca t i vi hin tng ho lng vn cn ang trong giai on pht trin v khng nn s dng nu khng c s tr gip ca chuyn gia.

Ghi ch:

e/vo t s ng sut lp

A ct sch

B ct bi

ng cong 1: 35% ht mn

ng cong 2: 15% ht mn

ng cong 3: < 5% ht mn

Hnh B.1 - Quan h gia cc t s ng sut gy ra ho lng v N1(60) cho ct sch v ct bi

i vi ng t Ms = 7,5

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ph lc c (bt buc)

Cc cng tnh u cc

C.1 cng ca cc c nh ngha nh lc (mmen) t ln u cc to ra mt chuyn v

(gc xoay) n v theo cng phng (cc chuyn v/ gc xoay theo cc phng khc bng 0), v c k hiu KHH ( cng theo phng ngang), KMM ( cng chng un) v KHM = KMH ( cng un - dch ngang).

Cc k hiu c s dng trong Bng C.1:

E mun n hi ca t, bng 3G;

EP mun n hi ca vt liu cc;

Es mun n hi ca t ti su bng ng knh cc;

d ng knh cc;

z chiu su h cc.

Bng C.1 - Cc biu thc cng tnh ca cc cc mm h trong 3 loi t

Loi t

s

HH

dEK

s

MM

EdK

3 s

HM

EdK

2

e = Es.z/d 35,060,0

s

p

EE

80,0

14,0

s

p

EE

60,0

17,0

s

p

EE

e = Es d/z 28,0

79,0

s

p

EE

77,0

15,0

s

p

EE

53,0

24,0

s

p

EE

e = Es 21,008,1

s

p

EE

75,0

16,0

s

p

EE

50,0

22,0

s

p

EE

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ph lc d (tham kho)

tng tc ng lc gia t v kt cu (ssi). Cc hiu ng chung v tm quan trng

D.1 T tng tc ng lc gia t v kt cu, phn ng ng t ca kt cu t trn gi mm,

nh kt cu c t trn nn c kh nng b bin dng, s khc vi phn ng ca cng kt cu nhng t trn nn cng (ngm chn) v chu mt kch thch trng t do tng ng, v cc l do sau:

a) Chuyn dch h mng t trn gi mm s khc vi chuyn dch ca trng t do v c th bao gm mt thnh phn dao ng rt quan trng ca kt cu b ngm chn;

b) Chu k dao ng c bn ca kt cu t trn gi mm s ln hn chu k dao ng c bn

ca kt cu b ngm chn;

c) Cc chu k dao ng t nhin, cc dng dao ng v cc h s m hnh tng phn ca kt cu t trn gi mm s khc vi kt cu b ngm chn;

d) gim chn tng th ca kt cu t trn gi mm s bao gm c gim chn bn trong

v bn ngoi xy ra ti b mt gia t v mng, ngoi gim chn ca kt cu bn trn.

D.2 i vi phn ln cc cng trnh nh cng cng, cc hiu ng ca tng tc gia t v kt

cu thng c li bi chng gim mmen un v cc lc ct trong cc cu kin khc nhau

ca kt cu bn trn. i vi cc kt cu c lit k trong chng 6 th cc hiu ng ca

tng tc gia t v kt cu c th l bt li.

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ph lc e (bt buc)

phng php phn tch n gin ha i vi kt cu tng chn

E.1 Theo quan nim, h s r c nh ngha l t s gia gi tr gia tc gy ra chuyn v lu di

ln nht ng vi cc lin kt hin hu, v gi tr gia tc ng vi trng thi gii hn cn bng (bt u chuyn v). Do , i vi nhng tng cho php chu chuyn v ln hn th r c gi tr cao hn.

E.2 i vi cc kt cu tng chn cao hn 10m, c th tin hnh phn tch theo bi ton mt

chiu vi trng t do ca cc sng lan truyn theo phng ng v mt gi tr c c tnh chnh xc hn, s dng trong biu thc (7.1), c th ly bng gi tr trung bnh ca

cc gia tc ln nht ca t theo phng ngang dc theo chiu cao ca kt cu.

E.3 Tng lc thit k tc dng ln tng chn ti lng tng, Ed c cho bi cng thc sau:

( ) wdwsvd EEKHkE ++= 21*2

1 (E.1)

trong :

H chiu cao tng

Ews lc nc tnh;

Ewd lc nc ng (c nh ngha di y);

* trng lng n v ca t (nh ngha sau y trong E.5 ti E.7);

K h s p lc t (tnh v ng);

kv h s ng t theo phng ng (xem biu thc (7.2) v (7.3)).

E.4 H s p lc t c th c tnh ton theo cc cng thc Mononobe v Okabe :

i vi cc trng thi ch ng:

nu 'd

( )( ) ( ) ( )( ) ( )

2

2

2

sin.sin'sin'sin

1sin.sin.cos

'sin

+++

+=

d

dddd

dK

(E.2)

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nu ' > d

( )( )dK sin.sin.cos

sin2

2

+=

(E.3)

i vi cc trng thi b ng (khng xt ma st gia t v tng):

( )( ) ( )( ) ( )

2

2

2

sin.sin'sin'sin

1sin.sin.cos

'sin

++++

+=

dd

dK

(E.4)

Trong cc biu thc trn c s dng cc k hiu sau:

d gi tr thit k ca gc khng ct ca t, ngha l d = 1

'

'tgtg

;

v cc gc nghing ca lng tng v ca b mt lp t p so vi phng ngang, nh trong Hnh E.1.

d gi tr thit k ca gc ma st gia t v tng, ngha l

d = 1

'

tgtg

;

gc c nh ngha trong E.5 n E.7 di y.

Biu thc ca cc trng thi b ng nn c u tin s dng cho b mt tng thng ng

( = 900). E.5 Mc nc ngm nm bn di tng chn H s p lc t

y s dng cc thng s sau:

* khi lng th tch ca t (E.5)

1h

v

ktgk

= (E.6) Ewd = 0 (E.7)

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trong :

kh h s ng t theo phng nm ngang (xem biu thc (7.1)).

Mt khc, c th s dng cc bng v biu p dng cho iu kin tnh (ch c ti trng trng trng) vi cc iu chnh sau:

v1h

Aktgk

= + (E.8) v

v1h

Bktgk

= (E.9)

ton b h thng tng-t c xoay thm mt gc tng ng l A hoc B. Gia tc trng trng c thay th bng gi tr sau:

A

vA

kgg cos

)1( += (E.10)

hoc

B

vB

kgg cos

)1( = (E.11)

E.6 t khng thm nc khi chu ti trng ng nm di mc nc ngm H s p lc t.

y s dng cc thng s sau:

*= - w (E.12)

1h

w v

ktgk

= (E.13) Ewd = 0 (E.14)

trong :

trng lng n v bo ho ca t;

w trng lng n v ca nc.

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E.7 t thm nc khi chu ti trng ng ( thm cao) nm di mc nc ngm H s p

lc t.

y p dng cc thng s sau:

*= - w (E.15)

1d h

w v

ktgk

= (E.16)

Ewd =

2)'(127 Hk wh

(E.17)

trong :

d trng lng n v kh ca t;

H chiu cao mc nc ngm tnh t chn tng

E.8 p lc thu ng ln b mt ngoi ca tng.

p lc q(z) ny c th tnh nh sau:

zhkzq wh .8

7)( = (E.18)

trong :

kh h s ng t theo phng ngang vi r = 1 (xem biu thc (7.1));

h chiu cao mc nc t do;

z ta thng ng hung xung vi gc to ti b mt nc.

E.9 Lc do p lc t tc dng ln cc kt cu cng

i vi cc kt cu cng v c ngm cng, trng thi ch ng khng th pht trin trong t, v i vi mt tng thng ng v t p sau lng tng nm ngang th lc ng do gia s p lc t c th ly bng:

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2.H.S.= dP (E.19)

trong :

H chiu cao tng.

im t lc c th ly trung im chiu cao tng.

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Ch ng B ng

Hnh E.1 - Quy c cho cc gc trong cng thc tnh ton h s p lc t

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ph lc f (tham kho)

sc chu ti ng t ca mng nng

F.1 Biu thc tng qut. n nh chng li s ph hoi v kh nng chu ti ng t ca mt

mng nng dng bng t trn b mt t ng nht c th c kim tra bng biu thc lin h gia bn ca t, cc nh hng ca cc tc ng thit k (NEd, VEd, MEd) ti cao t mng, v cc lc qun tnh trong t nh sau:

( ) ( )( ) ( ) ( ) ( )( ) ( ) 01111 V1 '

'

'

+

dkkc

cc

bkka

cc

NFmN

MFf

NFmN

Fe MMTT

(F.1)

trong :

maxNNN EdRd=

, maxNVV EdRd=

, max.NBMM EdRd=

(F.2)

Nmax kh nng chu lc cc hn ca mng di tc dng ca ti trng ng ng tm,

c nh ngha trong F.2 v F.3;

B chiu rng mng;

F lc qun tnh khng th nguyn ca t c nh ngha trong F.2 v F.3;

Rd h s ca m hnh (cc gi tr cho thng s ny c cho trong F.6).

a, b, c, d, e, f, m, k, k, cT, cM, cM, , l tr ca cc thng s ph thuc vo loi t, c nh ngha trong F.4.

F.2 t dnh thun tu. i vi t dnh thun tu hoc t ri bo ho nc th kh nng chu

lc cc hn di tc dng ca ti trng thng ng ng tm Nmax c xc nh theo cng thc:

( ) BcN

M 2max += (F.3)

trong :

c sc khng ct khng thot nc ca t, cu, i vi t dnh, hoc sc khng ct khng thot nc khi chu ti c chu k, cy,u, i vi t ri;

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M h s ring ca tnh cht vt liu;

Lc qun tnh khng th nguyn ca t F c xc nh theo cng thc:

c

BSaF g

= (F.4)

trong :

khi lng th tch ca t;

ag gia tc thit k ca nn loi A (ag = 1agR);

agR gia tc tham chiu ln nht ca nn loi A;

1 h s tm quan trng;

S h s ca t c nh ngha trong 3.2.2.2, Phn 1 ca tiu chun ny.

Cc iu kin hn ch di y c p dng cho biu thc kh nng chu lc tng qut:

10 < N , 1V (F.5)

F.3 t ri thun tu. i vi t kh v ri hoc t ri bo ha nhng khng pht sinh p lc

nc l rng ng k, kh nng chu ti cc hn ca mng di tc dng ca ti trng thng ng ng tm Nmax c xc nh theo cng thc sau:

NBg

agN v 2max 12

1

=

(F.6)

trong :

g gia tc trng trng;

av gia tc nn theo phng thng ng, c th ly bng 0,5ag.S v

N h s kh nng chu ti, mt hm ca gc khng ct thit k ca t d (gi tr d bao gm h s c trng vt liu M ca 3.1(3), xem E.4).

Lc qun tnh khng th nguyn trong t F cho bi cng thc:

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45

d

g

ga

F'tan. = (F.7)

iu kin hn ch sau c p dng cho biu thc tng qut:

( ) 'kFm1N0 < (F.8) F.4 Tr s ca cc thng s. Cc gi tr ca cc thng s trong biu thc chung biu din kh nng

chu ti i vi cc loi t trong F.2 v F.3, c cho trong Bng F.1.

Bng F.1- Gi tr ca cc thng s dng trong biu thc (F.1)

t dnh thun tu t ri thun tu

a 0,70 0,92

b 1,29 1,25

c 2,14 0,92

d 1,81 1,25

e 0,21 0,41

f 0,44 0,32

m 0,21 0,96

k 1,22 1,00

k' 1,00 0,39

cT 2,00 1,14

cM 2,00 1,01

c'M 1,00 1,01

2,57 2,90 1,85 2,80

F.5 Trong hu ht cc iu kin thng thng F c th ly bng 0 i vi t dnh. i vi t

ri F c th c b qua nu ag.S < 0,1g (ngha l ag.S < 0,98m/s2).

F.6 H s m hnh Rd ly theo cc gi tr cho trong Bng F.2.

Bng F.2- Gi tr ca cc h s m hnh Rd

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Ct cht va n

cht

Ct ri, kh Ct ri, bo ho St khng nhy St nhy

1,00 1,15 1,50 1,00 1,15