CONFINEMENT REINFORCEMENT DESIGN FOR REINFORCED CONCRETE COLUMNS

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1 onfrnsi Nasional Tknik Sipil 3 (ontks 3) Jakarta, 6 7 Mi 2009 CONFINEMENT REINFORCEMENT DESIGN FOR REINFORCED CONCRETE COLUMNS Tavio 1 and Bnn usuma 2 1 Dpartmnt of Civil Enginring, Spuluh Nopmbr Institut of Thnolog (ITS), ITS Campus, Sukolilo, Surabaa tavio@.its.a.id 2 Dpartmnt of Civil Enginring, Spuluh Nopmbr Institut of Thnolog (ITS), ITS Campus, Sukolilo, Surabaa kusumab06@ahoo.om ABSTRACT This papr prsnts a nw st of quations for th dsign of onfinmnt rinformnt for dutil arthquak-rsistant rtangular and irular onrt olumns basd on th masurd prforman in trms of urvatur dmand. Ths quations ar dvlopd from a paramtri stud on a larg numbr of olumns in whih aount for th influn of onrt strngth, axial load lvl, and transvrs onfinmnt rinformnt ild strngth and spatial distribution. Simplifiation of ths quations lads to dsign quations appropriat for dsign od of rinford onrt struturs (th futur SNI ). Ths quations ar thn validatd against a larg st of xprimntal rsults. Th implmntation in th SNI is also xplaind. words: onrt olumn; onfinmnt; dutilit; high strngth onrt; rinford onrt. 1. INTRODUCTION Man prvious rsarhs hav own that inras in th strngth and dutilit of strngth olumns an b signifiantl improvd b providing an fftivl onfind or b using transvrs rinformnt. Transvrs rinformnt provids thr main puporss, naml: (1) to prvnt bukling of longitudinal bars; (2) to avoid ar failur; (3) to onfin th onrt or produing th suffiint dformabilit (dutilit). Th transvrs or onfinmnt rinformnt rquirmnts ar mainl th funtions of th ratio of gross ara of olumn stion to ara of onrt or and th ratio of th spifid omprssiv strngth of onrt and th spifid ild strngth of transvrs rinformnt. Th provision of th numbr of th transvrsal rinformnt has bn rgulatd in th od, SNI , partiularl in Stion In this stion, th od provids rquirmnts for volumtri ratio of spiral hoops rinformnt (ρ s ) and ross-stional ara of rtangular hoop rinformnt (A ). Th objtiv of this papr is to dvlop a nw st of quations, diffrs with th xisting quations in SNI , for th dtrmination of onfinmnt rinformnt for rtangular and irular onrt olumns. Ths quations ar dvlopd from a paramtri stud of a larg numbr of olumns and aount for th influn of onrt strngth, transvrs rinformnt ild strngth, axial load lvl, and transvrs onfinmnt rinformnt spatial distribution. Simplifiation of ths quations lads to dsign quations appropriat for dsign od of rinford onrt struturs (th futur SNI ). 2. EXPERIMENTAL DATA FROM LITERATURE Thr is a larg databas of xprimntal rsults on olumns subjtd to onstant axial load. A total of 47 rtangular olumns and 25 irular olumns wr usd in this stud. Th ompris normal-strngth onrt (NSC) and high-strngth onrt (HSC) ranging from 26 to 110 MPa. Th ild strngth of stl is ranging from 255 to 1000 MPa. Th othr paramtrs onsidrd in this stud ar th olumn dimnsions, th numbr of longitudinal rinformnt, and th spaing of transvrs rinformnt. Various tis onfigurations ar also found in th adoptd olumn spimns for th stud. It ould b notd that th axial load lvl, masurd b th indx P, also varis for th onsidrd olumn spimns. n P o 3. DESIGN EQUATIONS FOR CONFINEMENT REINFORCEMENT Efftiv onfinmnt indx Th modl proposd b Lgron and Paultr (2003) for prditing th uniaxial bhavior of onfind onrt undr omprssion rlats th inras of strngth and dutilit of onrt to th fftiv onfinmnt indx I, whih is dfind as follows: Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta S - 17

2 Tavio and Bnn usuma l I = (1) whr = unonfind onrt strngth; and f l = fftiv onfinmnt prssur at pak strss, whih is masurd from th rstraint applid b th hoops to th latral xpansion of th onfind or undr axial omprssion. For irular olumn, f l is givn b = 1 (2) l 2 h whil, for rtangular olumns is givn b A f h = (3) l s whr = gomtri onfinmnt fftivnss offiint; A = total stion of onfinmnt rinformnt for th st of tis in dirtion ; = ross-stion dimnsion in dirtion, masurd ntr-to-ntr of priphral tis or spiral; s = ntr-to-ntr spaing btwn tis; ρ s = ratio of volum of spiral rinformnt to total volum of or, masurd ntr-to-ntr of spiral; and f h = strss in th onfinmnt rinformnt at th pak strss. Th proposd quation rlats th urvatur dutilit to th fftiv onfinmnt indx I as follows: I = k p µ ϕ (4) Gomtri offiint of onfinmnt fftivnss Shikh and Uzumri (1982) and latr modifid b Mandr t al. (1984) proposd th gomtri offiint of onfinmnt for rtangular olumns, 2 Σwi 1 6 x = s 1 2x ( 1 ρ ) s whr w i = lar horizontal spaing btwn two adjant latrall supportd longitudinal bars; x and = hight of th onfind onrt or masurd ntr-to-ntr of outr hoops in x and dirtion; s = lar spaing btwn two lvls of tis; and ρ = volumtri ratio of longitudinal stl masurd on th onrt or: ρ = As l x, in whih A sl = total ara of stl in th longitudinal dirtion. Th xprssion for th gomtri offiint of onfinmnt fftivnss for rtangular olumns is th produt of two trms: a horizontal arhing offiint h and a vrtial arhing offiint v, whr th horizontal arhing offiint usd in this stud is 2 h = 1 6) whr n l = numbr of th longitudinal rinformnt. Thn, th vrtial arhing offiint is v n l s s 1 1 x 2 2 = ( 1 ρ ) For irular olumns onfind with irular hoops, th gomtri offiint of onfinmnt fftivnss is s 1 2 = 2 ( 1 ρ ) whr = diamtr of th or masurd ntr-to ntr of hoops. Howvr, for irular olumns onfind b spirals, Mandr t al. (1984) proposd th following xprssion: s 1 2 = 0 (9) 1 ρ ( ) 0 (5) (7) (8) S - 18 Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta

3 Confinmnt Rinformnt Dsign for Rinford Conrt Columns Volumtri ratio of spiral or irular hoops rinformnt Th rquirmnt of th volumtri ratio of spiral or irular-hoop rinformnt for irular olumns, ρ s, as follows: ρ = 0. 40k (10) s p h Whras in SNI Stion , th quation to alulat ρ s is givn as follows: A g ρ = 0.45 s 1 A (11) f with th ild strngth of spiral rinformnt, f, is not takn mor than 400 MPa. Cross-stional ara of rtangular hoop rinformnt Th rquirmnt of th ross-stional ara of rtangular transvrs rinformnt for rtangular olumns, A, as follows: k p Ag = 0. 20k pkn (12) Ah Whil in SNI Stion (b), th quations to alulat th A ar givn as follows: and f A g A = (13) f h Ah A = (14) f h 4. COMPARISONS BETWEEN ANALYTICAL AND EXPERIMENTAL RESULTS To ow th aura of th proposd quations, th analtial rsults obtaind from th proposd quations ar validatd against th xprimntal data from litratur. Th omparisons ar also arrid out btwn th xprimntal data and th analtial rsults obtaind from th quations availabl in SNI and th analtial rsults obtaind from th quations suggstd b Paultr and Lgron (2008). From all th omparisons own in Tabls 1 to 6, th authors us th valus of dviation standard and COV from th ratio btwn th xprimntal and analtial A as th main paramtrs to masur th aura of th thr quations availabl in SNI , th quations suggstd b Paultr and Lgron (2008), and th proposd quations b th authors. For rtangular olumns, it an b sn in Tabl 5 th proposd quation givs th lowst valus of dviation standard, i This valu is lss than th valu obtaind from th quations availabl in SNI and th quation suggstd b Paultr and Lgron (2008), i and As to COV, th proposd quation givs lowr valu (0.463) than that obtaind from th quations from SNI (0.497). This valu is also slightl mor than that obtaind from Paultr and Lgron s quation that givs a valu of (th diffrn is onl 0.016). Howvr, it is worth to not that th dviation standards for ah group of spimns tstd in four diffrnt univrsitis (s Tabls 1, 3, and 5) indiats that th proposd quation provids th most aurat prdition ompard with th othr quations for all four groups of spimns. This vidnt provs that th proposd quation. For irular olumns, similar rsults ar found. Tabl 6 ows that th proposd quation givs th lowst valu of dviation standard, i This valu is lowr than th valus obtaind from th quations availabl in SNI and th quation suggstd b Paultr and Lgron (2008), i and 0.440, rsptivl. It an b sn that both valus ar muh gratr than th valus obtaind from th proposd quation. It ould also b notd that for ah group of spimns tstd in four diffrnt univrsitis (s Tabls 2, 4, and 6), th valu of dviation standard obtaind from th proposd quation alwas lowr than thos obtaind from th othr quations. For COV, th proposd quation and th quation suggstd b Paultr and Lgron (2008) giv similar low valus, that is This valu is lss than that obtaind from th quations in SNI , i It ould b notd, howvr, th offiint in Eq. (10) hav bn modifid b th authors from 0.40 to This modifiation also applis in Eq. (12), whr th offiint has also bn modifid from 0.20 to Th valus of 1.40 and 0.35 wr dfind to giv mor aurat prdition to th xprimntal data. Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta S - 19

4 Tavio and Bnn usuma Tabl 1. Comparison of analsis basd on SNI to Exprimntal Data on Rtangular Columns ƒ (mm 2 ) P/Po SNI (mm 2 ) A A SNI Univrsit of Shrbrook : Lgron and Paultr (2000) and Paultr t al. (2001) C100B130N C100B130N C100BN130N C100B60N C100B60N C100B60N C80B60N C120B60N C100BH80N C100BH55N C100B60N C100BH55N Man = Standard Dviation = COV = Univrsit of Toronto : Shikh and hour (1993), Shikh t al. (1994), and Barak and Shikh (1998) FS ES AS AS AS AS AS-3H AS-18H AS-20H AS-5HT AS-6HT AS-7HT ES-8HT ES-1HT AS-2HT AS-3HT AS-4HT Man = Standard Dviation = COV = Univrsit of Nbraska-Linoln : Azizinamimi t al. (1994) D /8-0.2P D60-7-3C-15/8-0.2P D /8-0.2P D C-15/8-0.2P D C-25/8-0.2P D C-15/8-0.2P D60-4-3C-25/8-0.2P D60-4-3C-25/8-0.4P D C-15/8-0.3P Man = Standard Dviation = COV = WP WP WP WP WP WP WP WP WP Man = Standard Dviation = COV = Th avrag of Standard Dviation = Th avrag of COV = Tabl 2. Comparison of analsis basd on SNI to Exprimntal Data on Cirular Columns ƒ P/Po SNI ρ SNI Univrsit of Ottawa : Saatioglu and Baingo (1999) RC RC RC RC RC RC RC RC RC Man = Dviation Standard = COV = WP WP Man = Dviation Standard = COV = s S - 20 Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta

5 Confinmnt Rinformnt Dsign for Rinford Conrt Columns ƒ Tabl 2. (Continud) P/Po SNI SNI Univrsit of California Brkl : Lhman t al. (2004) Man = Dviation Standard = COV = NIST : unnath t al. (1997) A A A A A A A A Man = Dviation Standard = COV = Th avrag of Standard Dviation = Th avrag of COV = Tabl 3. Comparison of analsis basd on proposd quations b Paultr to Exprimntal Data on Squar Columns ƒ (mm 2 ) P/Po proposd b Paultr (mm 2 ) proposdb Paultr Univrsit of Shrbrook : Lgron and Paultr (2000) and Paultr t al. (2001) C100B130N C100B130N C100BN130N C100B60N C100B60N C100B60N C80B60N C120B60N C100BH80N C100BH55N C100B60N C100BH55N Man = Dviation Standard = COV = Univrsit of Toronto : Shikh and hour (1993), Shikh t al. (1994), and Barak and Shikh (1998) FS ES AS AS AS AS AS-3H AS-18H AS-20H AS-5HT AS-6HT AS-7HT ES-8HT ES-1HT AS-2HT AS-3HT AS-4HT Man = Dviation Standard = COV = Univrsit of Nbraska-Linoln : Azizinamimi t al. (1994) D /8-0.2P D60-7-3C-15/8-0.2P D /8-0.2P D C-15/8-0.2P D C-25/8-0.2P D C-15/8-0.2P D60-4-3C-25/8-0.2P D60-4-3C-25/8-0.4P D C-15/8-0.3P Man = Dviation Standard = COV = WP WP WP WP WP WP WP WP WP Man = Dviation Standard = COV = Th avrag of Standard Dviation = Th avrag of COV = Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta S - 21

6 Tavio and Bnn usuma Tabl 4. Comparison of analsis basd on proposd quations b Paultr to Exprimntal Data on Cirular Columns ƒ P/Po proposd b Paultr proposdb Paultr Univrsit of Ottawa : Saatioglu and Baingo (1999) RC RC RC RC RC RC RC RC RC Man = Dviation Standard = COV = WP WP Man = Dviation Standard = COV = Univrsit of California Brkl : Lhman t al. (2004) Man = Dviation Standard = COV = NIST : unnath t al. (1997) A A A A A A A A Man = Dviation Standard = COV = Th avrag of Standard Dviation = Th avrag of COV = Tabl 5. Comparison of analsis basd on proposd quations b Authors to Exprimntal Data on Squar Columns ƒ (mm 2 ) P/Po proposd b Authors (mm 2 ) proposdb Authors Univrsit of Shrbrook : Lgron and Paultr (2000) and Paultr t al. (2001) C100B130N C100B130N C100BN130N C100B60N C100B60N C100B60N C80B60N C120B60N C100BH80N C100BH55N C100B60N C100BH55N Man = Dviation Standard = COV = Univrsit of Toronto : Shikh and hour (1993), Shikh t al. (1994), and Barak and Shikh (1998) FS ES AS AS AS AS AS-3H AS-18H AS-20H AS-5HT AS-6HT AS-7HT ES-8HT ES-1HT AS-2HT AS-3HT AS-4HT Man = Dviation Standard = COV = Univrsit of Nbraska-Linoln : Azizinamimi t al. (1994) D /8-0.2P D60-7-3C-15/8-0.2P D /8-0.2P D C-15/8-0.2P D C-25/8-0.2P D C-15/8-0.2P D60-4-3C-25/8-0.2P D60-4-3C-25/8-0.4P D C-15/8-0.3P S - 22 Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta

7 Confinmnt Rinformnt Dsign for Rinford Conrt Columns ƒ ƒ h Tabl 5. (Continud) A (mm 2 ) P/P o A proposd b Authors (mm 2 ) A proposd b Authors Man = Dviation Standard = COV = WP WP WP WP WP WP WP WP WP Man = Dviation Standard = COV = Th avrag of Standard Dviation = Th avrag of COV = Tabl 6. Comparison of analsis basd on proposd quations b Authors to Exprimntal Data on Cirular Columns ƒ ƒ h ρ s P/P o ρ s proposd b Authors proposd b Authors Univrsit of Ottawa : Saatioglu and Baingo (1999) RC RC RC RC RC RC RC RC RC Man = Dviation Standard = COV = WP WP Man = Dviation Standard = COV = Univrsit of California Brkl : Lhman t al. (2004) Man = Dviation Standard = COV = NIST : unnath t al. (1997) A A A A A A A A Man = Dviation Standard = COV = Th avrag of Standard Dviation = Th avrag of COV = CONCLUSIONS A proposd quations is prsntd to prdit th most aurat of transvrs rinformnt nd of rtangular and irular onfind olumn stion. Ths proposd quations aount for th influn of onrt strngth, transvrs rinformnt ild strngth, axial load lvl, and transvrs onfinmnt rinformnt distribution. Ths quations wr thn validatd against a larg st of xprimntal rsults. It an b onludd from th stud that th proposd quations giv mor aurat rsults than th othr quations, partiularl thos availabl in th xisting od, SNI Hn, th authors rommnds that thir proposd nw st of quations ould b adoptd in th futur SNI Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta S - 23

8 Tavio and Bnn usuma REFERENCES Azizinamimi, A., Baum uska, S. S., Brungardt, P., and Hatfild, E. (1994). Sismi bhavior of squar highstrngth onrt olumns. ACI Strut. J., 91(3), Barak, O., and Shikh, S. A. (1998). Confinmnt rinformnt dsign onsidration for dutil HSC olumns. J. Strut. Eng., 124(9), unnath, S.., El-Bah, A., Talor, A. W., and Ston, W. C. (1997). Cumulativ sismi damag of rinford onrt bridg pirs. Rp. No. NISTIR 6075, National Institut of Standards and Thnolog, Gaithrsburg, Md. Lgron, F., and Paultr, P. (2000). Bhavior of high-strngth onrt olumns undr li flur and onstant axial load. ACI Strut. J., 97(4), Lgron, F., and Paultr, P. (2003). Uniaxial onfinmnt modl for normal and high-strngth onrt olumns. J. Strut. Eng., 129(2), Lhman, D., Mohl, J., Mahin, S., Caldron, A., and Hnr, L. (2004). Exprimntal valuation of th sismi prforman of rinford onrt bridg olumns. J. Strut. Eng., 130(6), Mandr, J. B., Pritsl, M. J. N., and Park, R. (1984). Sismi dsign of bridg pirs. Rp. No. 84-2, Univ. Of Cantrbur, Christhurh, Nw Zaland. Paultr, P. (2001). MNPHI : Usr manual. CRGP Rp. No , Dpt. Of Civil Enginring, Univ. Of Shrbrook, Shrbrook, Canada. Paultr, P., Lgron, F., and Mongau, D. (2001). Influn of onrt strngth and ild strngth of tis on th bhavior of high-strngth onrt olumns. ACI Strut. J., 98(4), Saatioglu, M., and Baingo, D. (1999). Cirular high-strngth onrt olumns undr simulatd sismi loading. J. Strut. Eng., 125(3), Shikh, S. A., and hour, S. S. (1993). Confind onrt olumns with stubs. ACI Strut. J., 90(4), Shikh, S. A., Shah, D. V., and hour, S. S. (1994). Confinmnt of high-strngth onrt olumns. ACI Strut. J., 91(1), Shikh, S. A., and Uzumri, S. M. (1982). Analtial modl for onrt onfinmnt in tid olumns. J. Strut. Div., ASCE, 108(12), Watson, S., and Park, R. (1994). Simulatd sismi load tst on rinford onrt olumns. J. Strut. Eng., 120(6), S - 24 Univrsitas Plita Harapan Univrsitas Atma Jaa Yogakarta