Lecture 1 - Introduction to Composite Construction of Buildings

7/25/2019 Lecture 1 - Introduction to Composite Construction of Buildings

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I CNG V KT CU LINHP THP - BTCT

CHNG 1

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- Thp v b tng l hai vt liu b sung ln nhau

- B tng hiu qu khi nn, thp chu ko tt

- V b tng c th ngn cn mt n nh ca thp

- B tng chng n mn, cch nhit, chng chy

- Thp lm cho kt cu do dai

- u im ca dm lin hp l c cng v kh nng chu lc cao hn so

vi kt cu thng

- Nh c lin kt c hc gia bn b tng v dm thp nn kt cu lin hp

c s trt gia sn b tng v dm thp b hn so vi kt cu b tng

thp thng thng

1.1 i cng


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a. Kin trc:

- Thit k kt cu lin hp mang li nhiu dng kin trc

- Gim kch thc dm c dp ln, bn mng, ct c mnh b hn

- Linh hot v nhiu la chn thit k

b. Kinh t:

- Chiu cao tng v chiu cao cng trnh gim gim din tch tng bao

che, c th tng s tng vi cng tng chiu cao nh.

- Chi ph gim do kch thc b ( cng ln nn chuyn v nh, nhp ln v

tng chiu cao b)

- Thi gian xy dng nhanh:Tit kim chi ph, sm hon thnh cng trnh, sm a cng trnh vo s

dng

c. Cng nng:

- Chng chy

1.2 Cc phng din s dng kt cu composite

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d. Bo dng v tnh linh hot:

- C th ci to trong thi gian s dng

- C th bo dng m khng xm phm n ngi s dng

- Ci to cc phng tin dch v: trn nh, bn trong sn gi, cc hp chm

trong tng

e. Lp t:

- Sn thi cng l sn thp

- Thanh chng tm thi

- Ct thp ca thp tm nh hnh

- Thi cng nhanh v n gin

- Cht lng v chnh xc

1.2 Cc phng din s dng kt cu composite


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f. So snh

1.2 Cc kha cnh s dng kt cu lin hp

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1.2 Cc kha cnh s dng kt cu lin hp


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1.3 Cc b phn kt cu

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1.3 Cc b phn kt cua. Bn


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1.3 Cc b phn kt cuThp tm nh hnh

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1.3 Cc b phn kt cub. Dm


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1.3 Cc b phn kt cuc. Ct

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1.3 Cc b phn kt cud. Mi ni


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a. Trng thi gii hn ti hn (Ultimate Limit State)

- Thng kim tra kh nng chu lc ca tng cu kin chu lc tc dng, mi

cu kin c xem nh mt thnh phn c lp thit k.

- Kim tra vi ti trng tnh ton

- i vi dm, c th phn tch theo n hi, do, phi tuyn

- Thng cnh trn ca dm thp trong kt cu lin hp c ngn cn mt

n nh nh bn b tng. Tuy nhin khi chu moment m cnh chu nn

khng th ngn cn mt n nh nn phi kim tra mt n nh do xon

ngang

b. Trng thi gii hn s dng (Serviceability Limit State)- Kim tra vng v nt ca b tng

- Phn tch n hi i vi tnh ton theo trng thi gii hn s dng

1.4 Phn tch kt cu

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a. Millennium Tower (Vienna Autria)

- S tng: 55

- Chiu cao: > 202m (k c antenna)

- Din tch mt bng: 1000 m2

- Thi gian xy dng: 8 thng (t thng 5 n thng 12, 1998), 2 ~ 2.5 tng

mt tun

- Chiu dy bn: 19 cm

- n nh theo phng ngang: li thang my v thang b BTCT

- Ct ng composite

- Kinh ph: 145,000,000 Euro

1.5 Cc cng trnh tiu biu


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b. Ngn hng thnh ph Duisburg(Germany)

- S tng: 15

- Chiu cao: 75m

- Din tch mt bng: 14500 m2

- n nh theo phng ngang: li b

tng (thi cng 3m/ ngy)



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c. Bi u xe DEZ (Austria)

- Chiu dy bn: 26 cm

- Ct ng composite: ng knh 35.5cm

- Bi u xe tng 4 vi din tch 60x30m

- Nhp ln nht: 10.58m

- Dm cng sn: 4.80


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a. Tnh ton theo trng thi gii hn ti hn

- Phn tch n hi hoc phn tch do

- Lin quan n kh nng chu lc ca kt cu

- Da vo sc khng ca tng cu kin ring l

- Phi kim tra n nh tng th ca kt cu

- Tnh vi ti trng tnh ton

b. Tnh theo trng thi gii hn s dng

- Phn tch n hi

- Lin quan n vng gii hn v nt ca b tng

- Khng ch dao ng

- Tnh vi ti trng tiu chun

- Khng c gii hn v vng, tnh ton vng c so snh vi gii hn

vng trong EC3

1.6 Phn tch kt cu


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1.7 M hnh kt cua. S lm vic khng gian

n gin ha vic tnh khung khng gian bng cch tnh cc khung phng

b. Khung v lin kt- Khung lin tc: b qua s khng lin tc ca lin kt v xem lin kt l cng

- Khung n gin: xt n tnh khng lin tc ca lin kt, xem lin kt l

khp, khng c kh nng chu moment

- Khung bn lin tc: xem lin kt l na cng

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c. Tng tc gia kt cu v mng

- Trc tin, kt cu c m hnh vi nn c xem l cng, xc nh ti tc

tc dng ln nn v ln.

- ln c tnh vo kt cu di dng bin dng tc dng, t nh gi

nh hng ca ln ln ni lc v moment

- Khi ln nh hng ng k n ni lc, tng tc gia kt cu v mng

phi c xt n bng cch s dng cc lin kt l xo tng ng m

hnh s lm vic ca t nn

d. M hnh khung

- M hnh khung ph hp vi s lm vic thc t ca khung

- Hnh dng c bn ca khung c th hin bng cc ng thng qua tm

cu kin

- B qua s chng nhau ca b rng thc t ca cc cu kin

- C th xt n b rng thc t ca cc cu kin ti cc mi ni cc cu kin

1.7 M hnh kt cu


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nh hng ca Shear lag to ra s phn b ng sut khng u trong bn,

dn n khi nim b rng tnh ton.

1.8 B rng tnh ton

be1 = min(Lo/8; bi),

Lo bng khong cch gia cc im un ngc trong biu moment.

i vi dm t trn hai gi: Lo l nhp dm

i vi nhp gia v gi gia:

beff= be1 + be2

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1.8 B rng tnh ton

i vi dm lin tc: Lo l chiu di ca dm chu moment dng (i vi nhp)v l chiu di ca dm chu moment m (i vi gi) xc nh t hnh 4.

B rng tnh ton c dng kim tra kh nng chu lc ca tit din ngang

v xc nh c trng n hi ca cc tit din ny


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1.8 B rng tnh ton

beff = b0 + ibei

Vii = 0.55 + 0.025Le/bei 1.0

Le l chiu di nhp tng ng ca nhp bin

i vi gi bin:

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1.9 H s tnh i tng nga. Modun n hi ca thp

Modun n hi ca thp (theo EC4) ly bng 210x103 N/mm2

b. Modun n hi ngn hn ca b tng

B tng l vt liu

khng tuyn tnh,

khng n hi nn

modun n hi khng

l hng s (hnh 7), v

duy tr bin dng

thng xuyn khi

gim ti.


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1.9 H s tnh i tng ng

Khi chu ng sut

khng i, bin

dng ca b tng

tng dn theo thi

gian, gi l t bin

(hnh 8). B tng

cng chu s thay

i ca th tch

gy bi co ngt

(hoc phnh ra) v

do nhit thay

i.

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1.9 H s tnh i tng ngModun n hi thay i nh hnh 7.

- Modun tuyn tnh ban u

- Modun tip tuyn tng ng vi ng sut cho trc

- Modun ct tuyn

- Modun dy cung

Modun ph thuc vo ng sut ph thuc vo tc gia ti. Gi tr c s dng

cho thit k l modun n hi ct tuyn tng ng vi tc gia ti c th


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- Khi phn tch n hi, b tng chu nn v thp c xem lm vic n hi

tuyn tnh. Cho php s dng cng chng un khng xt n nt (EI)1, b

tng chu ko c xem khng nt. Ni s dng cng chng un ca tit

din nt (EI)2, th b qua kh nng chu ko ca b tng.

- Trong tnh ton c trng tit din composite trong min n hi, tit din

composite thp b tng c thay th bng tit din thp tng ng. i

vi tit din chu moment dng, din tch cnh b tngAc c thay th bng

din tch cnh thpAc/n, vi n l h s tnh i

- Khi tnh c trng hnh hc, ng sut: n = Ea/Ec

- Khi tnh cc tc ng di hn, chnh xc, s dng modun hu hiu

Ec: n = E a/Ec

Modun hu hiu l modun ngn hn i vi b tng c hiu chnh i vi

tc ng ca t bin

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1.10 Phn loi khung

a. Khung ging v khung khng ging

Khung ging: - c h ging (dn, vch)

- c th phn tch khung v ging ring r:

(khung chu ti ng v h ging chu ti trng ngang, ti ng tc dng ln

ging, tc ng ca nghing ban u v ti trng bn thn h ging)

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1.10 Phn loi khungKhung khng ging: l nhng khung khng c h ging hoc nhng khung c h

ging nhng khng cng. Vi khung khng ging chu ti ng v ti ngang

cng nh nhng nh hng ca s khng hon chnh khc (ng sut tha, hnh

dng cu kin khng chnh xc, khng phng, khng thng, lch tm)

b. Tiu chun phn loi khung ging v khung khng ging

S tn ti h ging trong kt cu khng m bo cho kt cu khung c xem

l khung ging. Ch khi h ging lm gim t nht 80% chuyn v ngang th

khung c xem l khung ging.

- Nu khung khng b tr h ging: khung khng ging

- Khi khung c b tr h ging:

Nu br > 0.2unbr: khung khng gingNu br 0.2unbr : khung ging

Vi br l mm theo phng ngang ca kt cu c h ging

unbr l mm theo phng ngang ca kt cu khng c h ging


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1.10 Phn loi khung

c. Khung khng chuyn v ngang khung chuyn v ngang

Khung khng chuyn v ngang:

- Khung chu ti trng ngang c cng c th b qua s gia tng lc do

chuyn v ngang ca nt gy ra

- Tc ng (nh hng) bc 2 (th cp) c th b qua (b qua nh hng ca

P )

- S dng phn tch bc nht i vi kt cu khung

Khung c chuyn v ngang:

- Khi nh hng bc hai khng th b qua, khung c xem l khung c

chuyn v ngang

1.10 Phn loi khungd. Tiu chun phn loi khung khng chuyn v ngang khung chuyn v

ngang

Phn loi khung (hay h ging) l c chuyn v ngang hay khng chuyn v

ngang da vo t s tng ti trng ng tc dng ln kt cu v ti ti hn n

hi do mt n nh gy ra (ph hoi theo dng c chuyn v).

VSd/ Vcr 0.1 : khung khng chuyn v ngang

VSd/ Vcr > 0.1 : khung c chuyn v ngang

Hay

cr= Vcr/ VSd 10: khung khng chuyn v ngang

cr= Vcr/ VSd < 10: khung c chuyn v ngang

Lecture 1 - Introduction to Composite Construction of Buildings

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