I I I I I KHOA HOC - CONG NGHE
NGHIEN CUU Sir DUNG
DAM LIEN HOP THEP - DE TONG GUIDING DO CAO TRONG CONG TRINH CAU
TS. NGUYEN XUAN HUY ThS. PHAM TH! THANH T H O Y
Dai hgc Giao thdng vgn tdi KS. KIM VAN L V Dai hgc Cdng nghe giao thdng van tai
2. CAU TAO VA DAC DI^M LAM VIEC DAM U 6 N HpT>THEP-BTCT 2.1. Ciu t90
Hinh 1 ttie hi^n d u tao cua mOt kit d u dim lidn hgp thdp - BTCT ndi chung (bd tdng thudng hogc BTCDC), bao gom 3 phin ehfnh:
dam thep, bdn b§ tSng, neo lien ket giiia dim thdp vdi ban be tdng.
Tom tit: Bii bao tap trung phdn tich sy anh huvng cua cir&ng dp be tdng doi ven sy Idm vipe eua dim lidn hgp thdp - BTCT.
Nghidn eOv dwQC tidn hanh bing cich Ipp md hinh md phdng dya trdn phin mem phan t^ hOv h^n. Phan tich cho thiy viPc su dyng BTCDC trong bin chiu nen eOa dim lidn hgp cho phdp tdng kha nSng chju lyc va dp cimg cua dim lin ddng ki. Tuy nhidn, cin thiit ki neo chong cit hgp ly di dam bao SLF lam vipc ding thoi giira dim thep va ban BTCT
Abstract: This paper examines on the influence of the concrete strength for the hybrid reinforced concrete- steel' behaviour The study was performed by modeling simulation based on the finite element software. Analysis showed that the-use of high strength concrete allows to increase significantly the bearing capacity and the stiffness of the beam. However, the shear stud connector must be designed to ensure composite action between the slab and the steel beam
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NhOng uu dilm cua dim lidn hap thep- be tdng cot thep (BTCT) trong cac cong trinh d u da dugc d l cap den trong nhilu tdi lieu khdc nhau. Mdt khoi lugng Idn cdc nghien cuu thyc nghipm vd ly thuylt ve sy Idm viec cua dim lien hgp thep- BTCT da dugc thyc hipn [3-6]. Cd the k l din mOt so uu diem nii trOi cua dim lien hgp nhu kha nang vugt nhjp ldn so vdi eae kit c l u BTCT truyln thong, tilt kipm van khudn thi cdng. ft anh hudng tdi giao thdng.
Tu han mOt thdp kf qua, BTCDC dang ngay cdng duge ung dung rOng rdi tro^ig eac cdng trinh xdy dyng. Vigc ung dung BTCDC trong eac cdng trinh c l u lien hgp
thep - BTCT cd nhung Igi ich nhu Idm tang tinh deo, tang kha nang chong mai mdn, tang sue khdng, vugt nhjp ddi han va lam tang tinh thim my cua cdng trinh. Tuy nhien, uu diem cua dim lien hgp thep - BTCDC vdn chua dugc khai thac hit do v i n cdn hgn c h i trong cdc nghien cdu ca ban va trong cac tieu chuin thiet k l . Do BTCDC cd dgc dilm Idm vipc khac so vdi be tdng cudng dO thdng thudng nen eae quy dinh v l thiet k l dya tren cdc thi nghipm cua be idng thudng khdng the ap dgng mdt cdch thuan tuy cho BTCDC. Npi dung bai bdo ndy se tap trung vao nghien cuu md phong sy lam vigc dim lien hgp thep - BTCDC.
Hinh 1. ciu t^o dim hen h<;/p thdp - BTCT Dam thep cd t h i Id dim djnh hinh hogc dam ghdp cd mat d t chu I.
Trong r l t nhilu trudng hgp, dim thep cd the Id kit d u dgng dim hop, dgng gidn. Dim djnh hinh tilt dien chi> I da duge san xult vdi chilu cao tilt dien len tdi lm co t h i su dgng cho cac d u nhjp vCpa va nhd. Trong trudng hgp muln tang kha nang cua vung keo trong dim thep cd t h i tang cudng them ban thep vao ban bien chju keo.
Ban be tong mgt clu Id mpt dam lien tgc ke len cdc dim dgc chju uln ngang, cd d u tao tuang tg"
nhu ban be tdng cua cdc dgng kit d u c l u khdc. Chilu ddy tii thieu eua ban mgt d u la 175 mm de dam bao dp cdng theo phuang ngang clu.
Neo (hay cdn gpi la neo chong cat) dung d l lien kit giiia dim thep vd ban be tdng cd tae dgng d l chong trugt giiia mgt tilp xuc. Neo chong d t dugc han vdo mgt trdn cua ban bien ndn cua dim thep vd chdn vdo ban betdng. Vi ban cd khuynh hudgg trugt theo cd phuang dung vd phuang ngang, neo chong d t phdi ddm bdo chong trugt theo cd hai phuang.
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KHOA HOC - C O N G NGHf I I I I I
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T n c UW12 boa deoP dugc nghien cuu blng cdch sii dung kit hgp phuang phap phdn tich chia thd phin tii va phuang phdp phan tich ljch su thdi gian.
Hinh 2. So do tinh tren mat eat dim lien hgp 2.2. Dac diem lam viec
Dae dilm Idm vipc cua d i m lien hap thep - be tong phg thuOc vao ung xu cua dam thep, ban be tdng va quan trpng nhlt la kha nang lien kit giua hai bd phan nay. Trong thilt k l dim lien hgp, lien kit giua ban be tdng vd dim thep (neo) phai khdng bj chay trudc khi dim thep hoac bdn bd tdng dgt den gidi han chay. Vipe tinh todn va thilt ke kit d u lien hgp xult phdt tii quan dilm la phin bdn be tdng d vung nen va canh dam thep d vCing keo ddng vai trd ehinh trong viOc chju uon Neu su dgng dim lidn hgp kep thi cac ban be tdng tren va dudi se chju uon, Phan sudn dim thep se ddng vai trd chinh d l ehju d t . O l khai thdc cd hieu qua cac vat lieu thdnh phin, mgt d t nen dugc cau tgo sao eho trge trung hod cua mat c i t di qua hoac d gin mat tilp xuc giua dim thep va ban be tdng (Hinh 2).
Trong trudng hgp trge trung hod nlm d ban cdnh be tdng, phin be tdng nlm d vung chiu keo dugc gia thilt la da nut vd duac bd qua khi tinh toan. Sy phan bo iing suit thye t l trong be tdng viing nen thudng dugc thay the blng khoi ung suit chu nhat vdi dO ldn cua ling suit theo tieu chuin 22 TCN 272-05 [2] Id f^ =^ 0,85//.
3. PHAN TICH A N H HU-dNG CUA CU'6'NG DQ BE TONG D £ N K H A N A N G C H I U Ll/C C O A C A C D A M LIEN HOP THEP-BTCDC Nhlm nghien cuu sy dnh hudng cua cudng dg be tdng den kha
nang chiu lyc eua eae dam lien hgp thep - be tdng COC, phuang phdp md phdng dya tren phin mem PTHH duge su dgng. Mdt md hinh phan tich eg the duge thilt lap dli vdi dim lien hgp thep - BTCT ehju uon. Trudc khi ddnh gia sy anh hudng cua tham s l cudng do be tdng trong dim lien hgp, md hinh se dugc so sdnh vdi kit qua thi nghiem cd sin.
3.1. Doi twgng nghien ciru Ooi tugng nghien cuu Id dim iidn hgp thep BTCDC chju uon bdn dilm duac Ngd Oang Quang va dong nghiep [4] tiln hdnh thi nghiem. BTCDC sii dung cd eudng dp danh djnh f —lOMPa, thep dim eo gidi han chay fy — 250MPa. Dim doi xung cd nhjp dai 2700 mm vdi cac kich thudc chi tilt d hinh 3.
3.2. Mo hinh hoa dim Uen hgp thdp-BTCDC
Md hinh md phdng sy lam viec cua dim lien hgp thep - BTCDC dugc thilt lap tren phan mim MIDAS CIVIL [1]. Ung xu phi tuyin eua kit d u dim lien hgp dudi tai trgng tdp trung, tang din
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Hinh 5. Mat cat dam dugc chia tho Md hinh vat lieu be tdng phd hogi deo vd md hinh vgt lipu thep ket d u nhu tren Hinh 6 dugc lya chpn.
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Hinh 6. Md hinh vat lieu phi tuyen
Hinh 3. Kich thude va so do thi nghiem dim tidn hgp
I So 9 nam 2015
' KHOA HOC - C O N G NGHE
Qun 14 Lvc • 0^ v6no
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0 4 vflng (mm)
Hmh 7. Quan he lye - chuyen vi tai glCra dim [4]
3.3. So sanh mo hinh voi ket qua thuc nghiem
Hinh 7 t h i hien quan he so sanh giua gia tri thi nghidm vd gid trj mo phdng cua quan he lyc tac dung - do vdng giiia dim.
Md hinh phan tich vdi cdc tham so vgt lipu va kit clu neu tren phin mem MIDAS CIVIL cho kit qua md phong kha phu hgp vdi kit qua thi nghiem dac bigt id trong vd ngay sau giai dogn dan hii.
Hinh 8 the hien trang thai lam viec eua mat d t dam tai giai doan cudi cung trudc khi d u kien bi pha hogi.
Kit qua cho thiy, tai giai doan trudc khi pha hoai, cac thd dudi cua mat cit dim thep da bj chay
cua cac dam hen hap cung dugc tinh todn theo Tieu chuin 22 TCN 272 - 05 de so sanh. Neu dilu kien on djnh tong the va cue bp dugc dam bao thi kha ndng chju lye eua dim dugc xac djnh blng mdmen deo cua tilt dien lien hgp.
Cu thi:
Hinh 8. Sy lam vide cua mat cit dam t^i giai doan cuoi cung [4]
3.4. Danh gia anh hudfng cua cuiyng dp be tong t&i sy lam vipc cua dam lien hgp Budc tilp theo cua nghien ctiu Id tien hanh khao sal md phdng su lam viec dim lien hap vdi cdc cudng dp be tdng 80MPa, 90 MPa, 100 MPa. Khd nang chiu lyc
M '• ^sVs + ^tVi + ^ . ^ w + ^ . ^ c trong do F,/^,P^,P lln lugt la cac lyc deo cua ban be tdng, ban cdnh chju keo, ban bgng va ban canh nen cua dim thep.
Bang dudi day cho thay kit qua thi nghipm va mo phong tuang doi tuang thich va Idn han so vdi ket qua tinh toan theo Tieu chuan.
Nlu dam bao lien kit giiia ban be tdng va dim thep la tuyet doi (tuang duang vdi viec neo khdng bj biln dang) thi viec tang cudng dp be tdng se cai thipn ro rgt sue khdng uln cua dim lien hgp.
4. K6T LUAN
Vipc s u dung be tong c u d n g do cao trong ban chju nen eua d i m lien hgp cho phep tang kha nang ehju lyc vd dp Cling cua dam len dang
ke. Cung n h u vdi cdc dam lien hpp s u dung be tdng t h u d n g , s y lam vipc cua d i m lidn hgp b l n g BTCDC bj k h i n g e h l bdi d i l u kipn dO vdng.
Do do giai phap k i t d u Idm t^ng dd Cling eua mgt d t thong qua sy phdn bo hgp ly cae bO phgn mat d t Id d n thiet de tgn dgng cudng dO cao cua vat lieu. Tinh toan theo 22 TCN 272-05 eho k i t qua nhd hon kha nhieu so vdi thi nghipm vd m5 phdng ndn d n xem xdt de xuat each tfnh m d i d l i vdi dam lidn hgp s i i dgng BTCDC. Mdt v i n d l quan trong khac Id vigc b l tri neo c i n d a m bao d l ban be tdng vd dam thep lam viec d i n g thdi n h l m dat tdi s u e khang t h i l t k l •
TAI Lt$U THAM K H A O ^ " ' [1] MIDAS CIVIL reference.
[2\ Bp Giao thong v|in tai (2005), TiSu chuin thilt k l d u 22 TCN 272-05.
[3] Phgm Duy Hiiu, Nguyin Long (2008), B§ tong cudng dg cao vd bS tfing chit lugng cao, Nhd xu^t bdn Giao thdng v|n tdi.
[4j Ngo DSng Quang (2010), Nghlgn Cliu phdt trien mot so dgng kit d u lai nhlm khai thac hgp ly be tdng cudng d$ cao dp dung c^o d c cong frinh d u . Oe tai Bg Gido dye vd ddo tgo, mSsI: 82010-04-107.
[5] B(i\ Thj Thanh Mai (2013),
"Nghien ciiu ddc diem Idm vi$c d a neo trong dam lien hpp thdp- bd tong cudng dO cao blng phu'O'ng phap PTHH'. Tap ch( Giao thfing vdn tai. 863,2013, trang 44-46.
[6] Nguyin Huy Cu-ong, Nguyen Quang Huy, Nguyin Xudn Huy [2014]. "Nghien ciiu iing xir cCia niit khung lien hpp thdp- be tdng d t thdp". Tuyin tgp cong frinh hOi nghj Ca hpc ky thudt todn quic, Vi§n Co hoc- ISBN 978-604-913-235-3, Ha Npi, 09/04/2014, pp. 97-102. ^ .
CuCTng do be tong SOMPa 90MPa lOOMPa
P (Tan) - LLfc tu-ang Lpng mo men deo Theo 22 TCN 272-05
15.56 15.71 15.82
Ma phong PTHH 25 26 26.5
