DIEN DAN KHOA HOC CONG NGHE
CHUYEN Vj Ciic OAI CUA TRU BETONG C 6 T THEP KHONG THEO TIEU CHUAN KHANG CHAN DUdi TAC DONG CUA TAI TRONG D O N G OAT
ULTIMATE DISPLACEMENT OF NON-SEISMICALY DETAILED REINFORCED CONCRETE COLUMNS SUBJECTED TO EARTHQUAKE LOADINGS
T S . T R A N C A O THANH N G Q C B6 mon Ky thuat XSy di/ng, OH au6c t6, OH Quoc gia TRHCIVl
Emal: [email protected], OT 0946464649
Tdm t i t
Bai bdo nay trinh t)cly cac k^ qud nghien cilti thi/c nghiem ufng xS cua trg bgt6ng c6t thep khdng theo ti€u chuan khdng chiin diTiSi tdc ddng cOa tdi trgng ddng 6k. Kk qu^ thi nghiem diTdc ^ n h bay thdng qua ct/dng dd khdng cdt, quan h^ li/c.
Celt chuydn vj ngang, chuyen vi ci/c dai, sd hinh thanh vk ndt Quan trong hdn h ^ thf nghiem nay se tap trung ddnh <gia..
chuyen vj ci/c dai hay dfi Igch tckng cUc dai cua txu BTCT khong theo ti§u chuIn khang chdn. K^t quei chuydn vj ci/c dai ^ u di/0c tjr thf nghigm ndy se di/dc so sdnh vdi cdc md hinh hien c6 d€ ddnh gid tinh chfnh xdc ciia nhiing mo hinh nay.
Abstract
This paper presents an experimental study on the seismic behavior of non-seismically detailed reinforced concrete columns. The experimental program consists of one large-scale non-seismically detailed reinforced concrete column. Quasi static cyclic loading, simulating earthquake actions, was applied. The overall performance of test specimen was°examine4 in terms ot lateral load capacity, cracking, stresses in steel bars. Special focus will be played on the ultimate displacement of the tested specimen. The result will be compared with ttie existing model.
Tir khda: tru betong cot th6p, chuyen vj ci/c dai, ddng dat, tdi trpng ngang.
1 . Dat v a n de
Trong mdt vdi nam gdn ddy, ufng x d cOa k i t cau bdtdng c6t thdp khdng theo tieu chuan khdng chdn dudi tac dung cua tdi trpng ddng ddt dang dupc kha n h i l u cdc nhd khoa hpc trdn t h i gidi quan tam. Mdt sd nghidn cdu thuc nghidm da dupc thi/c hidn tai Nhat, MJ vd Singapore cho try betdng cdt thep khdng theo tidu c h u i n khdng ehan. Cdc cdng trlnh ndy gdm cd cdc cdng bd cua Yoshimura {2000, 2003,2003), Lynn (2001), Sezen (2002), Nakamura (2002), vd Ousalem (2006). Trong ede nghidn cdu nay, tru betdng cdt thdp khdng theo tieu chuan khang c h i n vdi hdm lupng cdt dai thdp dudi tdc dung cua tdi trpng ngang lap ddo c h i l u da dupc nghien cdu chi t i l t . Mdt sd ede b i l n sd anh hudng d i n Lfng xit ciia tru cung dupe nghien ciili thdng qua m d hinh thi/c nghidm, nhir hdm lupng cdt dai, tdi trpng ddng...
Dya vdo k i t qua cua nhung nghien cijfu thi/c nghidm ndy, mdt sd nhd khoa hpc [Elwood 2005] da dua ra m d hinh de tfnh chuyen vj cue dai eho tru bdtdng c i t thdp khdng theo tidu chu^n ddng ddt. Tuy nhidn so vdl k i t edu theo tidu c h u i n khdng chdn, nhiJhg nghidn cilfu ndy vdn cdn khd khiem tdn. Nhdm tdng thdm s d hi^u b i l t v l iing xiJr, cung n h u k i l m chdng dd chfnh xdc eua md hinh e h u y i n vjj:uic dai eua t n j bdtdng d t thdp khdng theo tieu chuan d^ng d i t , bdi bdo ndy trlnh bdy k i t qud cQa nghidn cijfU t h i ^ nghidm v l logi k i t edu ndy.
2 . T h i n g h i 6 m 2.1. Md hinh thf nghl$m
K i t c i u khdng theo tidu chuan khdng chdn khd
ph6 b i l n d cdc nudc cd rui ro xdy ra ddng ddt thdp n h u V i e t N a m , Singapore... Tieu b i l u cho loai k i t cdu nay Id hdm lupng cdt dai thdp. Md hinh thf nghidm cho kdt edu tru khdng theo tidu c h u i n khang chdn phdi the hidn dupc ddc d i l m nay. IVId hinh SC-2.4-0.30 dupc thuti hien trong nghidn cHu nay cd ham IUdng cdt dai thdp, nhd hdn rdt n h i l u ham lupng ydu cdu trong cac tieu c h u i n khdng chdn n h u ACI 318-08 (2008), NZS 3101 (1998), A U (1994) vd ECS (1998).
Cdu tao cu t h i ciia mau thf nghiem S-2.4-0.30
Hinh 1. Sddd vi cdu tao cOa ddi tddng Oii nghiem
NGUdl XAY DI/NG s 6 THANG 11 & 12 - 2015 I
W 1
CHUYEN VI CUC BAI CUA TRU BETONG COT THER..
dupc trlnh bdy tren hinh 1. Luc dirng tac ddng vao tru 0.3 A^e. Cudng dp be tdng dUde sir dung eho md hinh thf nghiem Id 50 MPa.
2.2. Khung gia tai vd tai tong tac ddng He t h i n g gia tai diirng vd ngang dupc the hien nhu hinh 2. Thdng qua he t h i n g gia tai ddng, tai trpng ddng dupc tde dung tang ddn d i n khi da dat dupc gia trj ydu cdu 0.30 AJ^- Gia trj ndy dupc giQ: nguyen trong sudt qud trinh thf nghidm. Vdf muc dfch kiem tra danh gid kha ndng Idm vide dudi tdc dung eua tai trpng ngang dao chidu theo chu ky d l i vdi k i t c l u cdng trlnh, d ddy mdu tru thf nghiem se dupc thuc hien theo cdch tdc dung tdi trpng ngang ddo c h i l u vdi c h u y i n vj tdng ddn thong qua he gia t ^ ngang nhu hinh 2.
-50—-35O—fit)--
r i y ^ ^ f a l f l i ^ ' 2. KtKjng..s^ a lOIMQin ktetulac dung..liK;.di]bi 4.100-ton kfch tdc dung ii/c ngang Hinh Z. Hd thdng gia tai ddng vi ngang 2.3. Cdc thiit bi do vd thu thap dd lieu C h u y i n vj ngang la tham sd quan trpng cdn do va k h i n g c h l gid trj trong qud trlnh tac ddng tai trpng ngang theo ehu k^. O l do gia trj nay, 1 ddu do e h u y i n vj LVDT vdi dd ddi do 0 - 300 mm, dat tai vi trf nhu hinh 2.
Gdc xoay vd b i l n dang chdng cdt tai cac vj tri hai d i u try dupc dc thdng qua eac cap dung eg do chuyen vj dupc sir dyng d l do dp dich chuyen cua 2 d i l m khde nhau trdn ciing mdt t i l t dien khdo s a t Ttr k i t qua do ndy vd quan he hinh hpc ehiing ta ed t h i d l dang tfnh dupe gdc xoay hoac b i l n dang chdng cdt eua cdu kidn. S d dd bd trf t h i l t r \ / 1 ^! LVpT de do gdc xoay L V J vd b i l n dang chdng edt tai I M\ I cdc vj trf hai ddu try dupc f - *' ' - f trinh bay nhu hinh 3. Niiu I ^ trinh bdy d hinh nay, 4 cap LVDT dupc s d dyng de do b i l n dang chdng cat, 4 cap LVDT dupe sir dyng J de do gdc xoay tai cdc vj 260 trf khdc nhau cua 2 ddu
I tm.
^f Bi kiem tra dp b i l n dang cua cdt thep trong qud trinh ttif nghiem, cdc cam b i l n didn trd (strain WaiA Z: Sdddb&W difng cu do gauges) dupe dan vdo gdc xoay vi bidn dang ctidng cSt eac thanh edt thdp dpc
!- IX]
cua 2 dau try tap trung tai cac vi trf md mdmen i 6 n | dat gtd tri Idn nhdt, eiing vdi mdt s i dudC ddn d cdc c ^ J
dai tai 2 vj trf ndy. '^"
3. Ket q u a t h i n g l i i e m
3.1. Quan hS Iwc cat - chuydn vl ngang Quan hd luc cdt e h u y i n - vi ngang cua md hinh thf nghidm S-2.4-0.30 dupc hien thj d hinh 4. Md hinh S- 2.4-0.20 khdng dat d u p t kha ndng tfnh todn V^ (dya tren mdmen cue deu ciia tn^) trong s u i t qud trinh thf nghiem. Trong cd 2 c h i l u day vd kdo, luc cdt Idn nhdt d try dat dupc la 357.1 kN tai dd Idch tilng (DR) 1.15%. Md hinh thf nghidm S-2.4-b.30 b i t ddu suy gidm khd ndng chju lyp edt tai vdng lap thd 2 cOa d$
lech tdng ndy Try bj mdt on cfinh, khdng cd kha ndng chju tai trpng ddng nhu t h i l t k l ban ddu t^i d$ 1 ^ tdng DR 1.76%. Tai thdi diem ndy md hinh ttif nghidm dupc xem nhu da bj phd huy hodn todn.
300 - 200
? 100
i -100
*" -200 -300 -500
T y~:k Ji \M
fe-^_ Jv
^ •
^ ^ Z ^ ~ "
^ ^ ^ 3 - ^ •
^^5^
-
s-2.4-0.30 •
-
-34 -25 5 -17 -8 5 0 8.5 17 25.S 34
.
Lateral Dispbcement (mn)
Hinh 4: Cum h$ IUC cdt - chuydn vj ngang cua md hinh thi nghidm 3.2. Qua trinh hinh thdnh
vitnWt
Khi md hinh 8-2.4-0.20 dupc gia tdi d i n dd lech tdng ±0.40%, mdt sd v i t nut do mdmen udn bdt ddu xudt hidn d cd 2 ddu eua try (Hinh 5). Trong qud trinh gia tai d i n dp Idch tdng ±0.8%, v i t nut xien ddu tien xudt hidn d 2 ddu cua try. Tai dp lech t i n g 1.15%, khd n h i l u v i t nirt xien xudt hien, d i l u ndy ddn d i n khd ndng ehiu tai trpng ngang cua md hinh bi suy gidm. Tai dd Idch tdng nay cac v i t ndt xien dd hinh thdnh trudc cdng dupc m d rdng. Tai dp Ieeh tdng 1.76%, mpt v i t niifl xidn dupc hinh thdnh giCia try, vdt ndt nay Id nguydn nhdn Idm mdt I n djnh d try, Idm cho try phd huy hodn todn.
4. Chuyen vj c i / c dai Kha n h i l u thi nghidm dd d u p t thyc hidn cho tn^ BTCT, tuy nhidn trong hdu h i t cdc thf nghidm ndy cAi\ cb ldc cdt eye
HinhSrSt/fi/n/j/Zianft idt dong qui t
thi nghidm N G U d l X A Y D U N G SO T H A N G 1 1 & 1 2 • 2 0 1 5
CHUYEN V! Cifc OAI CUA TRU BETONG COT THER..
d?i i3i«;« nghiSn cOlu. Kha n nghiftn cilu v« c t i u y i n vj cue d j i duoc thue hi#n. Thf nghiem niiy se tap trung ddnh g i ^ chuyen vj cue dai hay dfi ISch t4ng cue dai oua tru BTCT IshSng theo tiSu c h u i n khSng c h i n . K8t qua chuydn vi cue dai thu dupe tir thf nghiem niiy se duoc so sanh vdi md hinh duoc phat tri^n bcrt Elwood (Elwood 2005).
Elwood (Eiwood 2005) 6h ra phucfng trinh nhi/sau (phuong trlnh 1) d l tfnh da i^ch t i n g cue dai. IVI6 hinh nay ph4t tnen dua tren ly t h u y l t ma sat cua lue c i t nhu hinh 6. Trong m6 hinh n&y 66 i^ch t i n g phu thupc v^o h^m luong cdt dai, gdc cua v i t nurt xien vk tgi trpng dOng tdc dung vdo t m :
4 l + (tang)'
(l).=
100 t a n ^ H (1)Trong dd (A/L)ald dd Idch t i n g cue dai; 9 la gde cua v i t nijft xidn; P la tdi trpng ddng tac ddng vd try; A „ Id hdm lupng thdp dai; s Id khodng each cua thep dai, fy, Id eudng dp chay ddo eua thdp dai; d^ Id c h i l u cao hiju dyng eua try.
,p C h u y i n vj eye dai hay dp Idch tdng thu dUdc t d thf nghidm Id 1.76%, trong khi dd k i t qud tir md hinh eiia Elwood (Elwood 2005) Id 1.14%. So vdi k i t qud thu dupc tdthf nghiem, k i t qua eua md hinh cho gia trj dp Ipch tdng nhd hpn. T i sd gitJia thf nghiem v d m d hinh la 1.278.
Hinh 6: MP hinh chuydn vi cdc d^i cua ^^^^ q ^ ^ g o g ^ ^ h Elwood (Elwood 2005) (,^0 thdy cdn n h i l u hdn nhung nghidn cijfu v l chuyen vj hay dd Idch t i n g cyc d^i de d l ra dupc nhQng md hinh chfnh xdc hon cho bdi todn ndy
5. Ket lu^n
Nghidn eiru ndy trinh bdy k i t qud thf nghipm eua mdt tn^ BTCT khdng theo tidu chuan khdng chdn dudi tdc dung cua tdi trpng ddng ddt. K i t qud thi nghidm dupe trlnh bay thdng qua cudng dp khdng cat, quan h$ lyc e l t e h u y i n vj ngang, c h u y i n vj eye dai, s d hinh thdnh v i t ndt. Thf nghidm tdp tmng di sdu ddnh gid c h u y i n vi cyc dai hay dd l ^ h t i n g cue dai cua t m BTCT khdng theo tidu e h u I n khdng c h i n , yd so sdnh vdi md hinh ly thuylt. Sau ddy Id mdt s l k i t ludn dya trdn k i t qud thyc nghidm da dm^te thyc hidn:
T h i nghidm cho thdy phd hCiy cua tn^ khdng theo tidu c h u i n khdng c h i n Id cho vdt niift xidn hinh thdnh
d gida try.
C h u y i n vj cyc dai hay dp Idch tdng thu dupe t d thf nghiem Id 1.76%, trong khi do k i t qua tir md hinh cua Elwood (Elwood 2005) la 1.14%. So vdi k i t qua thu dude t d thf nghiem, k i t qua cua md hinh eho gia trj dp Idch tdng nhd hon.
K i t ludn thu dupc chl dua tren 1 mdu thf nghiem, edn n h i l u hem nhiing nghidn eijfu thf nghidm cung nhir h? thuydt v l chuyen vj cyc dai ciia loai try ndy de hieu rd hdn dng x d cung nhu dua ra dupc nhQng md hinh ly t h u y l t chfnh xae hon cho try BTCT khdng theo tidu ehuan khdng chdn.
L d i c a m d n
Nghien cdu ndy dupc tdi trp bdi Quy phdt t r i l n khoa hoc vd cdng nghe (NAFOSTED) trong d l tdi m a s d " 1 0 7 . 0 1 - 2 0 1 3 . 1 ^ ' .
Tii lieu tham khao
1. ACI Committee 318 (2008), Building Code Requirements tor Stnictural Concrete (ACI 318-08) and Commentary American Concrete Institute, Farmington Hills, Mich.
2. AU (1994) Design Guidelines lor Ear^quake Resistant Reinforced Concrete Buildings Based on Ultimate Strengffi Concept (Drill) and Commentary, Architectural Institute of Japan, Tokyo, Japan 3. EC8/1/1-3 (1998) Design Provisions for Earthquake Resistance of Stmctures—General and Buildings, ENV1998-1, CEN.
4. Elwood, K. and Moehle, J. R (2005) 'Axial Capacity Model for Shear-Damaged Columns', ACI Structural Journal, Vol. 102, No. 4, pp.578-587.
5 Lynn, A. C. (2001) "Seismic Evaluation of Existing Reinforced Cona-ete Building Columns". Ph,D Thesis, University of California, Berkeley
6. NZS 3101 (1998), Concrete Stnictures Standard: Part 1-The Design of Concrete Stnjcture.
7. Nakamura, T and Yoshimura, M. (2002) "Gravity Load Collapse of Reinforced Concrete Columns wUh Bridie Failure Modes". Joumal of Asian Arcfiitecture and Building Engineering, Vol. 1,No. 1, pp. 2 1 - 27.
8. Ousalem, H. (2006) "Experimental and Anneal Study on Axia} Load Collapse Assessment and Retrofit of Reinforced Concrete CfMnns', Ph.D. Thesis, University of Tokyo. Tokyo.
9. Sezen, H. (2002) 'Seismic Response and Modeling of Reinforced Concrete Building Columns", Pfi.D. Thesis, University of California, Berkeley.
10. Yoshimura. M. and Yamanaka, N. (2000J "Ultimate Limit State ofRC Columns", the 2nd US-Japan Workshop on Performance-Based Earthquake Engineering Mettiodology for Reinforced Concrete Buflding Stmctures, Sapporo, Japan, pp. 313-326.
11. Yoshimura, M. and Nakamura, J. (2003) "Axial Collapse of R^nforced Concrete Short Columns', the 4th US-Japan Workshop on Performance-Based Earthquake Engineering Methodology for Reinforced Concrete Building Structures, Toba, Japan, pp. 187-198
12. Yoshimura, M., Takaine, Y and Nakamura. T. (2003) 'Ct^lapse Dnft of Reinforced Concrete Columns', the 5th US-Japan Woricstwp on Performance-Based Earthquake Engineering Methodology lor Reinforced Concrete Building Structures, Hakone, Japan, pp. 239-253.
N G U d l X A Y DONG s 6 T H A N G 1 1 & 1 2 - 2 0 1 5 1
