lvch-diem

Mc lc

Trang

Danh sch hnh v iii

Danh sch bng v

1 Kho st thc nghim 1

1.1 Gii thiu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Chng trnh th nghim . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.1 Mu th nghim . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.2 Vt liu ch to mu th nghim . . . . . . . . . . . . . . . . . . 4

1.3 M hnh th nghim Single Push Out Test (SPOT) . . . . . . . . . . . 6

1.3.1 Cu to v b tr thit b . . . . . . . . . . . . . . . . . . . . . 6

1.3.2 Nguyn l th nghim Single Push Out Test (SPOT) . . . . . . 9

1.4 Kho st thc nghim . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.4.1 Ch to mu . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.4.2 Qu trnh th nghim . . . . . . . . . . . . . . . . . . . . . . . . 12

1.5 Kt qu th nghim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.5.1 Kh nng khng ct v bin dng trt . . . . . . . . . . . . . . 15

1.5.2 nh hng chiu dy bn b tng . . . . . . . . . . . . . . . . . 16

1.5.3 nh hng cng b tng . . . . . . . . . . . . . . . . . . . 17

1.5.4 nh hng chiu dy lin kt . . . . . . . . . . . . . . . . . . . 18

1.5.5 nh hng ca hm lng ct thp xuyn qua cht b tng . . 18

1.6 M hnh xut kh nng khng ct ca lin kt perfobond . . . . . . 19

1.6.1 So snh kt qu th nghim vi cc m hnh d on kh nngkhng ct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.7 Dng ph hoi ca mu . . . . . . . . . . . . . . . . . . . . . . . . . . 23

1.7.1 Ph hoi bn b tng . . . . . . . . . . . . . . . . . . . . . . . 23

1.7.2 Ph hoi lin kt perfobond . . . . . . . . . . . . . . . . . . . 24

1.8 Kt lun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Ti liu tham kho 29

Ph lc 31

L lch trch ngang 31

i

Danh sch hnh v

1.1 Th nghim POT (a) [? ] v th nghim SPOT (b) [3] . . . . . . . . . . 2

1.2 Hnh dng v kch thc perfobond . . . . . . . . . . . . . . . . . . . . 3

1.3 Chi tit nhm mu S1, S2, S3 . . . . . . . . . . . . . . . . . . . . . . . 4

1.4 Chi tit nhm mu S4, S5 . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.5 Biu ng sut v bin dng ca thp tm perfobond . . . . . . . . . 5

1.6 M hnh th nghim SPOT . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.7 Bn b tng (a) v dm thp T (b) lin kt vi nhau bng lin ktperfobond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.8 Chi tit dm thp T . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.9 Khung thp (c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.10 B khung thp(d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.11 Bn thp tm (f) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.12 Kch thu lc 50T (g), load cell (h) v dy Jack (i) . . . . . . . . . . . 9

1.13 Nguyn l th nghim SPOT . . . . . . . . . . . . . . . . . . . . . . . . 10

1.14 Dm thp T sau khi hn li thp . . . . . . . . . . . . . . . . . . . . . 11

1.15 Dm thp T c t vo vn khun (tri) v mt xp dy 10mm chnvo dm (phi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.16 Mu khi b tng (tri) v mu sau khi tho vn khun (phi) . . . . 12

1.17 Qu trnh th nghim SPOT . . . . . . . . . . . . . . . . . . . . . . . . 13

1.18 Thanh thp ko khung phi cng trc thanh thp c nh dm thp T 13

1.19 V tr lp thit b o bin dng . . . . . . . . . . . . . . . . . . . . . . 14

1.20 S gia ti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.21 Biu quan h gia lc v bin dng trt ca nhm mu S1 S5 . 151.22 So snh mu S1 v S3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.23 So snh mu S3 v S4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.24 So snh mu S4 v S5 . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.25 So snh mu S1 v S2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.26 So snh thc nghim vi cng thc d on kh nng khng ct . . . . 20

1.27 Cht chng ct [? ] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.28 So snh thc nghim vi cng thc d on kh nng khng ct nhmmu S1-S2 (tri), S1-S3 (phi) . . . . . . . . . . . . . . . . . . . . . . . 21

1.29 So snh thc nghim vi cng thc d on kh nng khng ct nhmmu S3-S4 (tri), S4-S5 (phi) . . . . . . . . . . . . . . . . . . . . . . . 21

1.30 Biu kt qu thc nghim v cng thc xut . . . . . . . . . . . 23

1.31 Dng ph hoi b mt bn b tng ca cc mu . . . . . . . . . . . . 24

iii

1.32 Bin dng trt gia dm thp v bn b tng (a), bin dng ca ctthp trong cht b tng(b) . . . . . . . . . . . . . . . . . . . . . . . . . 24

1.33 Biu quan h lc v bin dng b tng ca nhm mu ti v tr LV DT1 25

1.34 Biu quan h lc v bin dng b tng ca nhm mu ti v tr LV DT2 25

1.35 Dng ph hoi ca lin kt . . . . . . . . . . . . . . . . . . . . . . . . . 26

1.36 Th nghim SPOT ca trng i hc Minho, B o Nha (tri) [6] vth nghim ca trng i hc RWTH Aachen, c (phi) [3] . . . . . 27

1.37 Khung thp c t theo phng ngang v c thanh chn thch hpcho tng chiu cao bn b tng . . . . . . . . . . . . . . . . . . . . . . 27

iv

Danh sch bng

1.1 Chi tit cc nhm mu . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Thnh phn cp phi b tng (tnh cho 1m3) . . . . . . . . . . . . . . 5

1.3 Cp bn ca b tng . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.4 c trng vt liu thp . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.5 Tng hp kt qu ca 05 nhm mu . . . . . . . . . . . . . . . . . . . . 15

1.6 Kt qu thc nghim vi cc cng thc d on kh nng khng ct linkt perfobond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.7 Kh nng khng ct ca kt qu thc nghim v cng thc xut . . 23

v

Chng 1

Kho st thc nghim

1.1 Gii thiu

Mc tiu ca kho st thc nghim nh gi nhm ng x ca lin kt perfobond

s c s dng cho dm ch T ngc thng qua xc nh kh nng khng ct,

dai v dng ph hoi ca lin kt khi thay i cc thng s khc nhau ca

m hnh.

Ti thi im hin ti theo ch dn ca EuroCode4 [1], kh nng chu lc ca

lin kt khng ct (shear connector) c nh gi thng qua th nghim nn-

y (Push Out Test-POT). Th nghim POT ang c p dng cho hu ht

cc loi lin kt ct khc nhau nh inh m, perfobond, mng ch C ... trong

nghin cu cng nh ng dng thc t.

Hnh 1.1a nh m t cu to ca mu th nghim POT cho lin kt perfobond

bao gm ??: dm thp, bn b tng, ct thp v tm perfobond. Dm thp bt

buc phi c tit din i xng v lin kt khng ct c hn vo bn cnh

ca dm, hai bn b tng i xng nhau c sau cng lp y cc l lin

kt. Khi th nghim, di tc dng ca lc nn tc dng vo u dm thp lm

cho dm trt tng i vi bn b tng.

Gn y, th nghim m hnh th nghim nn - y n (Single Push Out Test-

SPOT) c ngh bi Hegger v cng s [2] (Hnh 1.1b) cho php xt

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n nh hng ca lc ct theo hng vung gc vi trc dm bn cnh lc ct

dc. iu ny cho php m t mt cch chnh xc hn kh nng lm vic ca

lin kt khng ct, c bit trong trng hp dm tit tin ch T khi lc ct

vung gc l ng k.

Hnh 1.1: Th nghim POT (a) [? ] v th nghim SPOT (b) [3]

Trong phn kho st thc nghim, m hnh th nghim SPOT s c p dng

cho tt c cc nhm mu, cc m t chi tit v nguyn l, cu to cng nh lp

t thit b o cng c cp.

1.2 Chng trnh th nghim

1.2.1 Mu th nghim

kho st nh hng ca cc thng s m hnh n kh nng lm vic ti

hn ca lin kt, cc mu th nghim c chia 05 nhm vi 15 mu. Cc tham

s kho st bao gm chiu cao bn b tng, hm lng ct thp trong cht b

tng, cng b tng v kch thc lin kt c nu chi tit trong bng 1.1.

Cng tc ch to mu, thit b th nghim v qu trnh th nghim c thc

hin ti phng th nghim LAS 516, Cng ty Hong Vinh, a ch 14/2 BuBng, P.13, Q. Tn Bnh, Tp HCM.

2

Bng 1.1: Chi tit cc nhm mu

K hiu B tng Bn sn Tm lin kt S cht Loi perfobondfc (MPa) hs(mm) ts(mm) n

S1 33, 77 90 8 2 AS2 33, 77 90 8 1 AS3 33, 77 120 8 2 BS4 41, 0 120 8 2 BS4 41, 0 120 12 2 B

Trong :

hs: Chiu cao bn b tng (mm)

ts: Chiu dy lin kt (mm)

n: S lng ct thp 12 trong cht b tng.

Bn b tng cho cc mu c cng kch thc chiu di, chiu rng l 400mm,

ring chiu dy c thay i vi hai kch thc 90mm (loi A) v 120mm (loi

B). Lin kt perfobond dng trong thc nghim c dng ch c xut

bi Hi Vinh [? ], theo din tch mt ct ngang ca mt cht b tng l

4490mm2, dng mu perfobond ny c dng chung cho tt c cc nhm mu.

Hnh 1.2 m t kch thc chi tit v hnh dng ca perfobond.

Hnh 1.2: Hnh dng v kch thc perfobond

Trong nghin cu ny c hai cp b tng khc nahau c s dng vi fc =

33, 7MPa v fc = 41.0MPa, ct thp xuyn qua cht b tng dng loi c ng

knh 12 v s lng ct thp l 112 v 212mm. Ngoi ra ct thp trn b

mt lp bo v c ng knh 8mm cng c b tr thm hn ch nt

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trn b mt bn b tng. Tm thp to thnh lin kt perfobond c chiu di

L = 340mm c t nm trong bn b tng vi v tr mt trc ca perfobond

c t bng mt vi bn b tng. Chi tit cc nhm mu S1, S2, S3, S4, S5

th hin Hnh 1.3 v Hnh 1.4.

Hnh 1.3: Chi tit nhm mu S1, S2, S3

Hnh 1.4: Chi tit nhm mu S4, S5

1.2.2 Vt liu ch to mu th nghim

B tng c dng cho cc mu th nghim c cng nn tng ng cp

bn B20 v B40, chi tit thnh phn cp phi b tng c cho Bng 1.2.

4

Cng b tng thc t c xc nh bng th nghim nn mu lp phng

kch thc 150 150 150. T kt qu th nghim nn cho thy, cc nhm muS1, S2, S3 c cng chu nn fc = 33, 7MPa v nhm mu S4, S5 c cng

chu nn fc = 41, 0MPa. Bng 1.3 cung cp kt qu th nghim xc nh cng

nn v m un n hi ca b tng.

Hnh 1.5: Biu ng sut v bin dng ca thp tm perfobond

Bng 1.2: Thnh phn cp phi b tng (tnh cho 1m3)

Thnh phn n v fc(B20) fc(B40)

Ximng Si Gn(PC50) kg 370 410Ct vng kg 450 740 1x2 ( xanh) kg 840 1210Nc sinh hot lt 185 140Ph gia Sika kg 3, 7 4, 1

Bng 1.3: Cp bn ca b tng

Cp bn Cng chu nn fc (MPa) Modul n hi Ec (MPa)

B20 33, 77 29 103B40 41, 0 29 103

Bng 1.4: c trng vt liu thp

Thng s k thut Thp thanh (Vit Nht) Thp hnh CT3

Gii hn chy fy (MPa) 330 370Gii hn bn fu (MPa) 500 450Modul n hi E (MPa) 200 103 200 103Bin dng do y(%) 1, 8 1, 8

Thp c dng cho dm v lin kt perfobond l thp CT3, cc c trng c

hc thc t ca n c xc c xc nh da vo th nghim ko. Kt qu chi

5

tit cung cp 1.4, theo thp c gii hn chy ca c thp thanh v thp tm

u ln hn 330.0MPa, gii hn bn ca thp thanh t 500.0MPa trong khi

thp tm c gii hn bn thp hn vi 450.0MPa. Hnh 1.5 th hin ng cong

quan h gia ng sut v bin dng ca thp vi . Loi thp thanh 12 v 8

dng thp SD290 vi cc thng s c c t th nghim.

1.3 M hnh th nghim Single Push Out Test (SPOT)

1.3.1 Cu to v b tr thit b

M hnh th nghim c m t Hnh 1.6, theo cc thnh phn c bn gm

c: Bn b tng (a), dm thp T (b), khung thp (c), b khung (d), 02 thanh

thp 32 (e) ko khung, bn thp tm (f) c hn vi 318, kch thu lc

(g) v cm bin lc (load cell) (h). Cc cm bin c ni bng dy cp n h

thng thp d liu (i) v kt ni vi my tnh theo di cc thng s trong

sut qu trnh gia ti.

Hnh 1.6: M hnh th nghim SPOT

Bn b tng (a) v dm thp T (b) gn cht vi nhau thng qua lin kt khng

ct perfobond c nu ra Hnh 1.7. Dm thp T c to thnh t bn

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Hnh 1.7: Bn b tng (a) v dm thp T (b) lin kt vi nhau bng lin ktperfobond

thp 16044010 hn trc tip vi lin kt perfobond, gia bn b tng v bnthp c mt khong khng khi chu lc bn b tng v thp khng tip xc

vi nhau nh ng x thc ca dm ch T(Hnh 1.8).

Hnh 1.8: Chi tit dm thp T

Hnh 1.9: Khung thp (c)

7

Khung gia ti (Hnh 1.9) c ch to t thp tm v li hn vi nhau sao cho

c cng ln khng b bin dng di tc dng ca phn lc t mu,

lc ko t xi lanh thu lc khung s tc dng ln mu thng qua h khung ny.

B khung (d) gm c 02 dm thp I (250 200 10 8mm) di 1.3m, haidm ny c gn c nh xung sn cng (strong floor) nh vo 04 bulong neo

ng knh 42mm 350mm. Ngoi ta 02 tr ging b tng c thm vo m bo n nh cho ton h thng th nghim, Hnh 1.10 m t v tr lp t

ca hai khi b tng.

Trong th thng th nghim cn s dng hai thanh thp 32mm 1260mm (e),mt u ca chng c lp cht vi ngang thanh cng v tip xc trc tip

load cell. u cn li lin kt vi khung thp ko khung, khong cch gia

ko ny ln hn 170mm v chiu di ln hn 1200mm m bo hnh trnh

khi mu b bin dng. Dm thp T c gi c nh khi bn b tng chu ko

dng bn thp tm (f), bn thp tm c ch to ri l tm thp 34044012c nh v sn 08 bulong 14 hn c nh 0318 (chiu di 1000) cho Hnh

1.11. Kch thu lc (g) ng vai tr to ra lc ko (F), lc ny s tc dng ln

mu thng h khung v c o bng cm bin lc (h) ni vi thit b o. Ton

b s lp t thit b cho th nghim SPOT c gii thch hnh 1.12.

Hnh 1.10: B khung thp(d)

Nhn thy trong m hnh th nghim SPOT lin kt hon ton chu lc ct dc

v kh nng khng ca mt cht b tng lun c xc nh khng phi ly gi

8

Hnh 1.11: Bn thp tm (f)

Hnh 1.12: Kch thu lc 50T (g), load cell (h) v dy Jack (i)

tr trung bnh nh th nghim POT. Mu th nghim n gin gm dm thp

v 01 bn b tng tit kim thi gian v kinh ph ch to mu.

1.3.2 Nguyn l th nghim Single Push Out Test (SPOT)

Hnh 1.13 m t nguyn l ca th nghim SPOT, theo khi tin hnh th

nghim, lc ko (F) t xi lanh thu lc tc dng vo khung thp v chuyn

9

Hnh 1.13: Nguyn l th nghim SPOT

thnh lc nn tc dng vo mt y bn b tng theo phng nm ngang. Khi

b tng c gi n nh nh vo phn lc (V) ca thanh chn v gi tc

dng ln hai u bn b tng.

Bn b tng lin kt vi dm thp T thng qua lin kt khng ct perfobond,

bn cnh dm thp T c gi c nh. Khi lc ko tc dng ln bn b tng

th lc ny s ng thi tc dng ln tm ferfobond v gy ra phi lc mt

u bnh cnh ca dm T. Trong m hnh th nghim phn lc s c phng

song song vi lc nn tc dng vo bn b tng. T n s to ra moment

M = F H vi H = 0, 086mm v phn lc V = ML = 0, 232 F .

1.4 Kho st thc nghim

1.4.1 Ch to mu

Gia cng thp perfobondTm perfobond c ch to bng my ct CNC ng theo kch thc

nh sn, sau c hn vo tm thp 160mm440mm10mm to thnhdm thp T. Tip theo li thp 12mm t trong cht b tng v li thp

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lp bo v 8mm c hn tip vo dm thp T. Ton b qu trnh gia

cng lp t phn thp v ct thp c th hin trong Hnh 1.14.

Hnh 1.14: Dm thp T sau khi hn li thp

Cng tc vn khun v b tngVn khun c lm t cc tm vn p dy 25mm v c ct theo kch

thc nh sn. Khong h 10mm gia bn cnh dm thp v mt di

bn b tng c to ra bng cch chn mt lp mt xp dy 10mm sau

khi b tng lp xp ny c g b v to ta khe h. Cng tc b

tng c tin hnh cho tng nhm mu, quy trnh lp vn khun v b

tng c m t hnh 1.15. Mu th nghim hon chnh c th thin

Hnh 1.16.

Hnh 1.15: Dm thp T c t vo vn khun (tri) v mt xp dy 10mm chnvo dm (phi)

Trong sut qu trnh b tng cho cc nhm mu th nghim, mi m

trn u ly mu kch thc 150 150 150mm lm th nghim nn xcnh cng . Cc mu SPOT v mu nn c bo dng cng mt iu

11

Hnh 1.16: Mu khi b tng (tri) v mu sau khi tho vn khun (phi)

kin ging nhau m bo chnh xc ca kt qu th nghim SPOT.

V thi gian th nghim b gii hn cho nn trong thnh phn cp phi b

tng c s dng thm ph gia thc y qu trnh pht trin cng .

Cc th nghim nn v SPOT c thc hin ti 14 ngy tui thay v 28

ngy nh cch thng thng.

1.4.2 Qu trnh th nghim

Cng tc lp t khung gia ti v thit b ph tr c thc hin trc, tip

theo mu th nghim c t vo khung gia ti. Sau tin hnh gn cc

thit b o bin dng ln bn b tng v dm thp, kt ni ton b h dy cp

tn hiu vo thit b thu thp d liu v my tnh. Trnh t chi tit c th

hin Hnh 1.17 v 1.19. Trc khi tin hnh th nghim cn phi kim tra ln

cui trong c bit ch 02 thanh thp 32mm ko khung v pha trc phi

cng trc vi 03 thanh thp 18mm c nh dm thp c trnh by trong Hnh

1.18.

Qu trnh gia ti c tin hnh theo ch dn ca EuroCode4 [1], theo ti

trng p t c chia thnh 3 giai on chnh c ch ra hnh 1.20. Theo

giai on 1 ti trng c tng ti ln khong 40%Pmax, sau lp li 2 ln. Giai

on 2, ti trng c lp li 25 ln vi bin dao ng t 10% n 40%Pmax.

Sau khi kt thc giai on ny, ti trng s c tng dn n khi mu b ph

hoi v thi gian tng ti khng di 15 pht. Trong sut qu trnh tng ti,

12

Hnh 1.17: Qu trnh th nghim SPOT

Hnh 1.18: Thanh thp ko khung phi cng trc thanh thp c nh dm thp T

13

Hnh 1.19: V tr lp thit b o bin dng

Hnh 1.20: S gia ti

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cc i c vt l s c ghi li mt cch t ng. Khi ti trng gim xung

cn 80%Pmax th qu trnh th nghim kt thc. Cc s liu th nghim s c

xut ra t thit b o v x l c c kt qu cui cng.

1.5 Kt qu th nghim

1.5.1 Kh nng khng ct v bin dng trt

ng cong quan h gia lc v trt tng i ca 05 nhm mu S1 n S5

c biu din Hnh 1.21, tng hp kt qu th nghim ca chng c trnh

by Bng 1.5.

Bng 1.5: Tng hp kt qu ca 05 nhm mu

Nhm mu Pmax(kN) Puk(kN) Puk1(kN) uk(mm)

S1 186, 1 167, 5 83, 7 10, 745S2 179, 8 161, 8 80, 9 6, 239S3 243, 3 219, 0 109, 5 13, 142S4 262, 7 236, 4 118, 2 18, 054S5 372, 9 335, 6 167, 8 13, 422

Puk,1: Kh nng khng ct ca mt cht b tng

Hnh 1.21: Biu quan h gia lc v bin dng trt ca nhm mu S1 S5

15

C th nhn thy rng, kh nng khng ct ca mt cht b tng trong mu

S5 l ln nht (167, 8kN) trong khi nhm mu S4 c bin dng trt ln nht

(18, 054mm). Cc nhm mu khc c kt qu bin thin theo mt quy lut nht

nh, iu ny cho thy cc thng s chiu dy bn b tng, hm lng ct thp

xuyn qua cht b tng, cng b tng v chiu dy ca lin kt nh hng

n kh nng khng ct v dai ca lin kt.

Quan st hnh 1.21 c th nhn thy, nhm mu S2 (01 thp 12mm xuyn qua

cht b tng) c dai nh nht so vi cc nhm mu c 02 thp 12mm. Nh

vy hm lng ct thp trong cht b tng nh hng n dai ca lin kt.

So snh nhm mu nhm mu S4 v S5 c chiu dy tm perfobond tng ng

l 8mm v 12mm, cho thy nhm S5 c kh nng khng ct ln nht nhng li

c bin dng trt nh hn. iu ny cho thy bin dng ca tm perfobond

nh hng n dai v lc khng ct ti hn ca lin kt, trong trng hp

ny lc khng ct t l nghch vi dai. Cc so snh v tho lun chi tit nh

hng ca tng tham s s c cp phn tip theo.

1.5.2 nh hng chiu dy bn b tng

Hnh 1.22: So snh mu S1 v S3

16

nh hng ca chiu dy sn b tng c thc hin thng qua so snh cc

mu ca nhm S1 v S3 nh Hnh 1.22. C th thy rng kh nng khng ct

ca mu S3 cao hn mu S1 l 23, 51% v bin dng trt cao hn 18, 24%. Nh

vy chiu dy ca bn b tng lm tng kh nng khng ct ca lin kt cng

nh bin dng trt b tng. iu ny c th gii thch khi chiu dy tng ln

th din tch vng chu ct-ko ca cht b tng cng tng ln, do vy tng lc

khng ct v dai ca cht cng s tng.

1.5.3 nh hng cng b tng


So snh nhm mu S3 v S4 nhn thy cng b tng mu S4 cao hn mu

S3 l 17,2%, kh nng khng ct ca mu S4 cao hn mu S3 l 7, 38% v bin

dng trt l 27, 2% th hin hnh 1.23. Nhn thy rng kh nng khng ct

ca lin kt tng khng nhiu, trong khi bin dng trt li tng nhiu, iu

ny c th gii thch trong qu trnh b tng gia cc mu khng c ng

u v khi tch b tng dng trong thc nghim nh vng b tng chu nn t.

17


1.5.4 nh hng chiu dy lin kt

Quan st trn Hnh 1.24 so snh kt qu th nghim ca nhm mu S4 v S5,

kh nng khng ct ca nhm mu S5 cao hn nhm mu S4 l 29,55%, nhng

bin dng trt li gim 25, 66% so vi nhm mu S4. iu ny c th c gii

thch khi chiu dy tm lin kt tng th cng cht b tng cng tng dn

n lm tng kh nng khng ct v bin dng trt s gim i.

1.5.5 nh hng ca hm lng ct thp xuyn qua cht b

tng

Hnh 1.25 biu din ng cong quan h lc-bin dng trt ca hai nhm mu

S1 v S2. C th nhn thy rng nhm S1 cho kh nng khng ct cao hn

khng nhiu so vi S2 vi chnh lch l 3, 39%. Tuy nhin bin dng trt ca

mu S1 li ln hn mu S2 n 41, 94%. Lng ct thp tng s lm tng ng

k n dai ca lin kt.

18


1.6 M hnh xut kh nng khng ct ca lin

kt perfobond

1.6.1 So snh kt qu th nghim vi cc m hnh d on

kh nng khng ct

Bng 1.6: Kt qu thc nghim vi cc cng thc d on kh nng khng ct linkt perfobond

NM TN Tu v Vinh Oguejiofor Jin Hee Ahn Sung Hoon Kim Medberry

S1(kN) 186, 1 292, 662 194, 62 208, 290 148, 811 135, 049S2(kN) 179, 8 208, 663 102, 635 118, 016 79, 427 67, 903S3(kN) 243, 3 292, 662 195, 924 215, 207 149, 128 135, 296S4(kN) 262, 7 293, 089 195, 721 211, 147 149, 845 135, 397S5(kN) 372, 9 329, 934 195, 721 211, 147 149, 845 149, 79

Cc nhm mu th nghim c cu to, c trng hnh hc v vt liu c

cp trong 1.2.1. nh gi yu t quan trng nh hng n kh nng khng

ct ca lin kt tin hnh so snh kt qu th nghim vi cc cng thc trong

mc ?? ng thi da trn kt qu m phng s nhm xut cng thc tnh

kh nng khng ct ca lin kt perfobond. Bng 1.6 v biu nu Hnh 1.26

so snh gia kt qu thc nghim vi cng thc d on ca Oguejiofor dng

19

Hnh 1.26: So snh thc nghim vi cng thc d on kh nng khng ct

cng thc ?? , Jin Hee Ahn ??, Sung Hoon Kim ??, Medberry ??, Tu

v Vinh ??. Cc cng thc c p dng khng tnh thnh phn kh nng chu

nn ca b tng pha trc lin kt l do mu th nghim b tr lin kt bng

mt vi bn b tng. Nhn thy cng thc xut ca Tu v Vinh c chnh

lch vi kt qu thc nghim thp hn so vi cc cng thc khc l do trong

cng thc c xt n nh hng ca chiu dy lin kt n kh nng chu nn

ca thp tm v c xt nh hng ca hm lng ct thp trong bn b tng.

Trong nghin cu ca Tu v Vinh [4] dng b tng c cng siu cao nn

vng chu nn ca b tng c dng hnh chp c nu th hin r trong Hnh

1.27.

Hnh 1.27: Cht chng ct [? ]

20

Hnh 1.28: So snh thc nghim vi cng thc d on kh nng khng ct nhmmu S1-S2 (tri), S1-S3 (phi)

Hnh 1.29: So snh thc nghim vi cng thc d on kh nng khng ct nhmmu S3-S4 (tri), S4-S5 (phi)

Da trn Hnh 1.28 v Hnh 1.29 cho thy gia kt qu thc nghim vi p dng

cc cng thc xut c s chnh lch kh ln v kh nng khng ct cc

nhm mu. Chng hn, khi so snh nh hng ca hm lng ct thp trong

cht b tng th cc cng thc c nh hng ln n kh nng khng ct ca

lin kt vi nhm mu S1 tng trn 40% so vi nhm mu S2 trong khi vi kt

qu thc nghim ch tng 3, 39%. Vi nhm S1 v S3 so snh nh hng chiu

cao bn b tng th vi kt qu thc nghim kh nng khng ct tng 23, 51%

trong khi p dng cc cng thc xut th li khng tng, cho thy vi cc

cng thc xut c xt n nh hng ca kch thc bn b tng nhng gi

tr nh hng rt nh gn nh khng nh hng n kh nng khng ct ca

lin kt c th hin trong Hnh 1.28). nh gi nh hng ca cng b

tng so snh nhm mu S3 v S4 kt qu thc nghim cho thy kh nng khng

ct tng 7, 38% trong khi cc cng thc xut gn nh khng tng. Cng nh

nh gi nh hng chiu dy lin kt gn nh khng c tnh n trong cc

cng thc xut trong khi kt qu thc nghim li tng n 29, 55% c minh

ho trong hnh 1.29.

21

Vi kt qu th nghim v m phng t c cho thy kh nng khng ct ca

lin kt b nh hng ng k bi tham s chiu dy lin kt, din tch cht,

chiu cao bn b tng. Tc gi xut cng thc tnh kh nng khng ct ca

lin kt perfobond da trn cng thc xut ca Oguejiofor [5] ca Tu v

Vinh [4] vi cc tham s kh nng khng ct ca bn b tng, din tch cht

b tng v hm lng ct thp trong bn b tng, nh hng ca chiu dy lin

kt n cng ca thp perfobond, trong cng thc xut khng xt nh

hng kh nng chu nn ca chp b tng v b tng dng trong thc nghim

l b tng thng thng nn chp chng ct rt nh gn nh bng ng knh

cht. Vi cc h s c xc nh nh vo phng trnh hi quy tuyn tnh.

qu = 1Accfck + 2Atrfy + 3Arfy + 4ntscdfya (1.1)

qu = 1q1 + 2q2 + 3q3 + 4q4 (1.2)

vi q1, q2, q3, q4 l kh nng chu ct dc ca b tng, nh hng ca din tch

cht b tng n lin kt perfobond, hm lng ct thp trong cht b tng v

hm lng ct thp trong sn b tng. Xc nh cc h s 1, 2, 3, 4.

1 = 28, 766 2 = 0, 6766 3 = 0, 0041 3 = 1, 5181 (1.3)

Thay cc h s ca 1.3 vo 1.2 ta c cng thc xut sau:

qu = 28, 766Accfck + 0, 6766Atrfy 0, 0041Arfy 1, 5181ntscdfya (1.4)

Hnh 1.30 cho thy tng quan gia cng thc xut v kt qu thc nghim

c h s tng quan R2 = 0, 9916. Qua kt qu cho thy vi mu s S2 khi p

dng cng thc xut th cho kt qu trng vi kt qu thc nghim. iu

ny cho thy c s nh hng r hm lng ct thp (ct thp trong cht b

tng v ct thp trong sn b tng) n kh nng khng ct cng nh bin dng

trt ca lin kt. Tng t nhn thy vi cc nhm mu cn li S1, S3, S4, S5,

c kh nng khng ct thc nghim v cng thc xut b 5%. Bng 1.7 ktqu p dng cng thc xut vi kt qu thc nghim t c.

22

Bng 1.7: Kh nng khng ct ca kt qu thc nghim v cng thc xut

Nhm mu hes(mm) tes(mm) f ck(MPa) Atr(mm2) Pmax(kN) Ppred(kN) PmaxPpred

S1-1(kN) 70 8 33, 7 452, 16 186, 12 179, 49 1, 037S1-2(kN) 70 8 33, 7 452, 16 174, 4 179, 49 0, 972S1-3(kN) 70 8 33, 7 452, 16 171, 9 179, 49 0, 958S2(kN) 70 8 33, 7 226, 08 179, 8 179, 80 1, 000S3-1(kN) 100 8 33, 7 452, 16 291, 8 242, 86 1, 201S3-2(kN) 100 8 33, 7 452, 16 243, 3 242, 86 1, 002S3-3(kN) 100 8 33, 7 452, 16 214, 3 242, 86 0, 882S4-1(kN) 100 8 41, 0 452, 16 258, 3 268, 97 0, 977S4-2(kN) 100 8 41, 0 452, 16 262, 7 268, 97 1, 008S4-3(kN) 100 8 41, 0 452, 16 271, 2 268, 97 0, 960S5-1(kN) 100 12 41, 0 452, 16 332, 1 377, 23 0, 880S5-2(kN) 100 12 41, 0 452, 16 372, 9 377, 23 1, 131S5-3(kN) 100 12 41, 0 452, 16 426, 7 377, 23 0, 989

Hnh 1.30: Biu kt qu thc nghim v cng thc xut

1.7 Dng ph hoi ca mu

1.7.1 Ph hoi bn b tng

Quan st mu trong qu trnh tng ti thy rng, khi ti trng tc dng t 80%

n 90% Pmax th trn b mt bn b tng bt u xut hin cc vt nt ti v

tr ti tc dng sau lan rng n cc v tr dc theo chiu di lin kt. Cc vt

nt cc nhm mu c th hin trn Hnh 1.31 cho thy c lc ct dc xuyn

qua cht b tng lm cho cht b ph hoi dng ko v ct (tension-shear) gy

23

ra bin dng trt gia dm thp v bn b tng lm cho bn b tng v dm

thp b tch thnh hai phn (Hnh 1.32a), ct thp trong cht b tng cng b

bin dng (Hnh 1.32b) chng t ct thp cng tham gia qu trnh chu ct.

Hnh 1.31: Dng ph hoi b mt bn b tng ca cc mu

Hnh 1.32: Bin dng trt gia dm thp v bn b tng (a), bin dng ca ctthp trong cht b tng(b)

Qua v tr o bin dng ca LV DT1 v LV DT2 trn bn b tng nhn thy ti

v tr LV DT1 khi bt u chu ti tc dng bn b tng ti v tr ny chu ko

c ng sut ko pht trin cho n khi mu b ph hoi c cho Hnh 1.33.

Vi v tr LV DT2 ti trng ban u mu chu ng sut nn, khi ti trng tng

thy c vt nt xut hin mu chuyn sang ng sut ko c minh ho Hnh

1.34.

1.7.2 Ph hoi lin kt perfobond

Quan st cc mu sau khi b ph hoi nhn thy cc perfobond u b bin

dng, nht l ti v tr ti tc dng perfobond chu nn v ti v tr xa ti tc

24

Hnh 1.33: Biu quan h lc v bin dng b tng ca nhm mu ti v trLV DT1

Hnh 1.34: Biu quan h lc v bin dng b tng ca nhm mu ti v trLV DT2

dng perfobond chu ko cho thy c s nh hng ln nhau gia cc cht b

tng khi chu lc ct th hin Hnh 1.35.

1.8 Kt lun

Khi c b tr ct thp trong cht b tng th lin kt perfobond l lin ktt v dai theo tiu chun Eurocode 4. in hnh khi hm lng ct

25

Hnh 1.35: Dng ph hoi ca lin kt

thp trong cht b tng c thay i t 112 thnh 212 th dai lin

kt tng ng k ln n 41, 94%.

Khi bn b tng thay i chiu cao 90mm v 120mm dn n lm tngchiu cao ca b tng v tng chiu cao lin kt nm trong b tng, kt

qu kh nng khng ct tng 23, 51% v dai ca lin kt tng 18, 24%.

S gia tng cng b tng khng lm cho kh nng khng ct tng caoch tng 7, 38% trong khi bin dng trt li tng n 27, 2%, u ny

cho thy trong qu trnh b tng khng t nh mong mun.

Cht b tng cng cng th dai cng gim, iu ny th hin trong sthay i chiu dy lin kt. Khi chiu dy lin kt cng tng th kh nng

khng ct tng 29, 55% trong khi bin dng trt li gim n 25, 66%.

ti kho st ng x ca lin kt perobond h dng trong dm lin hp c tit

din T ngc khi s dng b tng thng c cng t 33MPa n 41MPa,

vi nhng iu kin hin c ca phng th nghim m hnh ca ti khc vi

nhng nghin cu trc l khung thp c t theo phng ngang hot ng

nh vo b khung. Vi th nghim SPOT c nghin cu th khung thp

dng cho cc mu c cng chiu cao bn b tng cn vi khung thp ca ti

c th dng cho cc mu c chiu cao bn b tng khc nhau nh vo thanh

chn c iu chnh bng bulong 20 c trnh by Hnh 1.37.

26

Hnh 1.36: Th nghim SPOT ca trng i hc Minho, B o Nha (tri) [6] vth nghim ca trng i hc RWTH Aachen, c (phi) [3]

Hnh 1.37: Khung thp c t theo phng ngang v c thanh chn thch hpcho tng chiu cao bn b tng

27

Ti liu tham kho

[3] Sabine Heinemeyer geb Rauscher. Zum Trag- und Verformungsverhalten von

Verbundtragern aus ultrahochfestem Beton mit Verbundleisten. PhD thesis,

Institute of structural concrete, RWTH Aachen University, Germany, 2011.

[6] Maria Isabel Brito Valente. Experimental Studies on Shear Connection Sys-

tems in Steel and Lightweight Concrete Composite Bridges. PhD thesis, Civil

Engineering Department - School of Engineering University of Minho, Por-

tugal, 2007.

[1] Structural steelwork eurocodes development of a trans-national approach.

[2] Hegger.J, Rauscher.S, and Goral. Push out test on headed studs covered

with uhpc. European Conference on Steel Structures, B:4956, 2005.

[4] Bui Duc Vinh. Behaviour of Steel Concrete Composite beams made of ultra

high performance concrete. PhD thesis, Dessertation, University of Leipzig,

2010.

[5] Oguejiofor and Hosain.M.U. Perfobond rib shear connectors. an experimental

investigation. In International conference on steel and Aluminium structure,

1991.

29

L LCH TRCH NGANG

H v tn: NGUYN TH NGC DIM

Ngy, thng, nm sinh: 26/03/1983

Ni sinh: Long An.

in thoi: 0939.750.579

Email: [email protected]

a ch lin h: 430-Chu Th Kim-Phng 7-Thnh ph Tn An-Long An.

QU TRNH O TO

T 2002 n 2007: Sinh vin trng i hc Dn Lp Vn Lang Tp.HCM chuyn

ngnh Xy Dng Dn Dng V Cng Nghip.

T 2011 n nay: Hc vin cao hc trng i hc Bch Khoa Tp.HCM chuyn

ngnh Xy Dng Dn Dng V Cng Nghip.

QU TRNH CNG TC

T 2007 n 2008: K s xy dng ti Cty TNHH Vit Giai.

T 2008 n nay: K s xy dng ti Ban Qun l D n Thnh ph Tn An,

tnh Long An.

31

Danh sch hnh vDanh sch bng1 Kho st thc nghim1.1 Gii thiu1.2 Chng trnh th nghim1.2.1 Mu th nghim1.2.2 Vt liu ch to mu th nghim

1.3 M hnh th nghim Single Push Out Test (SPOT)1.3.1 Cu to v b tr thit b1.3.2 Nguyn l th nghim Single Push Out Test (SPOT)

1.4 Kho st thc nghim1.4.1 Ch to mu1.4.2 Qu trnh th nghim

1.5 Kt qu th nghim1.5.1 Kh nng khng ct v bin dng trt1.5.2 nh hng chiu dy bn b tng1.5.3 nh hng cng b tng1.5.4 nh hng chiu dy lin kt1.5.5 nh hng ca hm lng ct thp xuyn qua cht b tng

1.6 M hnh xut kh nng khng ct ca lin kt perfobond1.6.1 So snh kt qu th nghim vi cc m hnh d on kh nng khng ct

1.7 Dng ph hoi ca mu1.7.1 Ph hoi bn b tng1.7.2 Ph hoi lin kt perfobond

1.8 Kt lun

Ti liu tham khoPh lcL lch trch ngang

lvch-diem

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