Lecture 1 - Introduction to Composite Construction of Buildings
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Transcript of Lecture 1 - Introduction to Composite Construction of Buildings
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I CNG V KT CU LINHP THP - BTCT
CHNG 1
2
- 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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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)
1.5 Cc cng trnh tiu biu
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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
1.5 Cc cng trnh tiu biu
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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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1.9 H s tnh i tng ng
- 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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1.9 H s tnh i tng ng
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1.9 H s tnh i tng ng
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1.9 H s tnh i tng ng
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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