International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 310 Seimic Behavior of Concrete Column and Beam Reinforced with Interlocking Spiral Ioanni A. Tego, Theodoro A. Chryanidi, Michail A. Titota Abtract Column of a rectangular cro-ection with interlocking piral are the latet development in bridge-building, where they are applied on pier of high earthquake-reitance requirement. Thi method can be applied alo on oft torie of building, like piloti. Flexural behavior of tructural element with interlocking piral, but mainly their behavior due to hear, mut be further invetigated, both analytically and experimentally. Thi tudy refer to thee problem, compriing an experimental and an analytical part. More preciely in the experimental part, the repone of column and beam with interlocking piral i compared to the repone of conventionally reinforced one. Ueful concluion are drawn on the performance of thee tructural element with the propoed reinforcement arrangement. Index Term Column, confinement, interlocking, pier, reinforced concrete, eimic, piral 1 INTRODUCTION UST like a circular column ection, on account of architec- contruction (paper made formwork), eimic- tandardization, favoring mainly piral reinforcement. Thi The econd advantage can include alo the feaibility of Jtural, reitance, etc. requirement, can be preferred to a quare one, in the ame way a rectangular ection with two interlocking or non-interlocking piral can be ued intead of a correponding kind of piral reinforcement, produced at variou diameter, can, in the opinion of the author of thi tudy, contitute the tandardized olution to a problem, olved until today follow- conventionally reinforced one (Fig. 1a, 1b, 1c). Thi ing an epecially arduou olution. All the more with the figure alo how the advantage of cae (b) over cae (a), in the tandardized olution, it i poible to make good ue of higher cla reinforcing teel for piral, which i more effective cae that eimic-reitance i required only in one principal direction of the ection (economy, higher confining efficiency). than teel clae, ued nowaday, a a rule. Rectangular column with two interlocking piral were for It i noteworthy that depite the mot encouraging experimental and analytical reult of work by Tanaka and Park [5], the firt time propoed (and preferred to the conventional one at that), by the competent U.S. Authority, the California [6], the reearch on the influence of the problem variable on Department of Tranportation, for pier of earthquakereitant bridge [4]. Few cientit throughout the world have remain almot tagnant. Cyclic hear (i.e. eimic type load- the behavior of column ection with interlocking piral, till conducted reearch on the behavior of tructural component reinforced uing interlocking piral [7], [8], [9], [10], [11], [12], [13]. The author of thi tudy are convinced, that ection with interlocking piral can perform jut a well on critical torie, like piloti of building, where concrete confinement requirement are epecially high, due to low value of L/h (L: Column net height, h: Column ection height), which a a rule imply failure due to hear. The following two reaon are the main reaon for thi preference: ing) i of particular importance from a reearch tandpoint in connection with mall hear pan length element. Up to now, the problem of ecure interlock of piral ha been ufficiently reearched and a correponding criterion ha been formulated (Fig. 2). In accordance with the criterion in quetion, the interlock i ecure on condition that the ditance between center of the interlocking piral i not greater than 1.2 time the piral radiu r. It i alo recommended, once more, for the purpoe of enuring the interlock of piral, that at leat four longitudinal bar hould be provided inide the interlocking area of the 1. Increaed ductility a a reult of the higher confining efficiency in circular column ection compared to rectangular one and piral (Fig. 3). It wa acertained that the preence of thee longitudinal reinforcement improve the ability of the tru mechanim to carry hear force. 2. Contruction preference, which nowaday favor the circular column ection, after replacement of traditional wooden formwork by throwaway type paper made one, which can only be applied on circular A known, in the cae of a imple circular ection the expreion giving the hear portion carried by the reinforcement, improved by Prietley [3] i: cro-ection. π b V= Α ( 2f y ) (1) 4 Ioanni Tego i a Profeor at the Department of Civil Engineering of the where Aritotle Univerity of Thealoniki, Greece. A i the ection area of piral bar Theodoro Chryanidi ha received hi mater and Ph.D. degree from the f y i the yield trength of the piral teel Department of Civil Engineering of the Aritotle Univerity of Thealoniki, Greece. He ha alo received a mater degree from Imperial College of i the centre to centre pacing of piral London, UK. E-mail: theodoro_gr@yahoo.com b i taken a equal to the diameter of cro ection core. Michail Titota ha received hi Ph.D. degree from the Department of Civil Engineering of the Aritotle Univerity of Thealoniki, Greece.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 311 Fig. 1 Type of ection: (a) Single ection, (b) Complex-ection with tranvere reinforcement, interlocked and (c) Complex ection with tranvere reinforcement, non interlocked.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 312 It i pointed out that ACI-318 tandard [1], a well a NZS:3101 [2], ue for the ame quantity the familiar relation of the claical tru model: 2Α V= z fy (2) where z i taken a 0.8D, and D i the diameter of the gro area of cro-ection Although Tanaka and Park [5], [6] propoe the equation mentioned below for the hear carried by piral with adequate interlock: V= Α π ( 2f y +2) D A f d y (3) 4 where d i the ditance between center of interlocking piral (Fig. 2) The concept of an enveloping perimeter of a ubtitute ection i introduced in the preent tudy, attempting to correlate the bending reitance and hear reitance of the complex ection conidered with the bending and hear reitance of the ection with an enveloping perimeter propoed (Fig. 4). More concretely, in order to obtain an (approximate) calculation of the ultimate moment reitance of the ection with interlocking piral, a circular enveloping perimeter for the ubtitute ection i propoed with the ame reinforcement (Fig. 4b), until the precie diagram are completed which, in thi phae, have not been fully elaborated. Wherea for etimating the ection reitance to hear and bending, an enveloping rectangle i propoed a perimeter of the ubtitute ection (Fig. 4c). Now, a far a the amount of hear carried by the concrete i concerned, the familiar EC2 form of expreion for rectangular cro-ection i propoed: N V=τ c Rd k 1.2+40 ( ρ +0.15 ) b wd Ac where b w the width of the rectangular ubtitute ection ρ half of the percentage of the longitudinal reinforcement of the ection Wherea for the hear portion carried by the reinforcement, expreion (2) applie with z=0.8h, where h equal the depth of the rectangular ubtitute cro-ection. Naturally, in the cae conidered of complex ection with interlocking piral, for the calculation of ρ, only the longitudinal reinforcement of one ide (piral) mut be conidered, a related to the whole rectangular cro-ection. (4) Fig. 2 Condition for ecure interlock: d>1.2r.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 313 Fig. 3 Deformation of interlocking piral due to diagonal hear cracking. Fig. 4 Propoed ection with enveloping perimeter for an approximate deign of complex ection: (a) Cro-ection to be deigned, (b) Enveloping circle for flexural analyi and (c) Enveloping rectangular for hear analyi.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 314 vertical element in bridge contruction through the utilization of piral reinforcement. 2 RESEARCH SIGNIFICANCE Laboratory of Reinforced Concrete and Maonry Structure ha et out on an experimental but alo analytical reearch into upgrading piral reinforcement in column ection with varying ratio of ection ide. The program include 21 pecimen under monotonic or cyclic loading, whereby the poibilitie of improving the eimic reitance mechanical propertie of element with interlocking piral or with piral farther apart from each other will be invetigated. The econd cope of the reearch, in addition to improving mechanical propertie (trength, tiffne, ductility, energy diipation capacity), i the contructional tandardization of 3 SPECIMENS Three piece of "pilot" pecimen work were contructed, within the overall reearch framework, among which two with interlocking piral and a third one with one plain piral reinforcement ued for comparion purpoe with the preceding one. Cro-ection and geometry of the pecimen are hown in Fig. 5 while detail concerning concrete, reinforcement, material propertie and axial loading are ummarized in Table 1. Fig. 5 Geometrical characteritic of pecimen.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 315 TABLE 1 MECHANICAL PROPERTIES OF SPECIMENS Longitudinal Spiral reinforcement Normalied fc reinforcement Specimen axial load (MPa) Ø fy Ø fy (mm) (MPa) (mm) (mm) (MPa) 1-26.0 14 540 5.5 35 465 2-24.0 14 485 5.5 35 465 3 0.10 22.5 10 480 5.5 35 465 4 TEST SETUP AND INSTRUMENTATION Tet pecimen 1 and 2 were ubjected to monotonic loading a imply upported beam (Fig. 6, 7). Shear pan-to-depth ratio were 3.5 for pecimen 1 and 3.0 for pecimen 2. Specimen 3 with pan-to-depth ratio 2.0 wa ubjected to cyclic lateral loading (Fig. 8). Specifically for pecimen 3, cyclic lateral loading wa applied uing two one-way actuator and wa meaured uing two load cell attached to the pecimen. The data of the load cell were recorded through a digital Wheattone bridge with great preciion. The point load diplacement δ of the cantilever-pecimen were meaured through a pecific potentiometer onto an electronic voltmeter and the control of the actuator diplacement wa carried out by linear variable differential tranducer (LVDT) attached to the actuator cap and connected to the controller. Finally, the axial load wa impoed on pecimen 3 by a hydraulic compreion jack, mounted on moveable cart which could be laterally diplaced together with the laterally loaded free end of the pecimen. Fig. 6 Loading of pecimen 1.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 316 Fig. 7 Loading of pecimen 2. Fig. 8 Loading of pecimen 3.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 317 5 EXPERIMENTAL RESULTS 5.1 Specimen 1 and 2 For pecimen 1 and 2, the progreively-increaing loading wa recorded, and the ultimate load carried wa noted (Fig. 6, 7). In both cae, flexural-hear crack appeared on either ide of the point load with a minimum 45 degree inclination. Thi typical crack pattern wa ucceeded by a typical hear cracking at a 45 degree inclination toward the upport point around the element axi. Finally, in the upport area of the element and at a latter tage of loading, near the ultimate load-carrying capacity, the characteritic tied arch mechanim crack appeared with bigger inclination. It i noteworthy that alo in the cae of pecimen 2 with the complex cro-ection, a uniform crackingconfiguration wa oberved without any ign of eparation of the interlocking piral at any point of the pan length under the ultimate load-carrying capacity. It wa expected that a critical piral diconnection area would come up near the upport due to maximum hear (Fig. 9). According to Fig. 9, the alteration of force in the tenion zone caue hear at the level of overlapping piral of the complex cro-ection equal to the hear on the ame point of the beam. Finally, pecimen 1 failed howing, almot at the ame time, ymptom of ultimate reitance due to bending and hear. The capacity value recorded wa 220 kn. Failure of pecimen 2 took place in the ame manner and the capacity value meaured wa 350 kn. Fig. 10 how ome calculation curve which give, for variou value of the mechanical volumetric ratio of tranvere teel ω, the normalized moment μ. The ame figure alo indicate the value pertaining to: a) the experimental reult of the three pecimen, b) the value calculated on the bai of the propoed ubtitute cro-ection with an enveloping perimeter (Fig. 4). The real trength (reulting from the tet) of pecimen with interlocking piral i equal to 80% of the trength calculated on the bai of pecimen with the ubtitute cyclical cro-ection (Fig. 4b). Fig. 9 Stre inide the interlock area i proportional to the exiting hear of the cro ection. Fig. 10 Diagram for an approximate calculation of ection with interlocking piral on the bai of the propoed ubtitute ection: (a) cyclical (for bending) and (b) rectangular (for bending and hear) cro-ection.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 318 5.2 Specimen 3 The mechanical behavior of pecimen 3 under cyclic lateral loading (eimic type of loading) i hown in Fig. 11 in the form of load veru diplacement hyterei loop. The hape of hyterei loop point out to the following: 1. Specimen trength wa maintained unabated, taking alo into conideration the P-δ effect, even at the ultimate diplacement of 45mm. Due to thi diplacement the inclination of the pecimen axi wa 8%. 2. The influence of lippage of the reinforcement i negligible, taking into account that thi would caue hyterei loop pinching (narrowing of the hyterei loop epecially near the zero diplacement point) in the load veru diplacement diagram of the pecimen. Thi ignifie that the cyclic hear had no deteriorating influence upon the interlock of the two piral. 3. The energy diipation capacity illutrated a the area of the ucceive hyterei loop in the P veru δ diagram i progreively increaing a deformation increae and thi i reckoned to be an important advantage of earthquake-reitant mechanical behavior. A typical flexural failure, a hown in Fig. 8, wa oberved for pecimen 3, a expected, on account of the low percentage of longitudinal reinforcement in comparion to the other two pecimen, with which pecimen 3 had equal amount of tranvere reinforcement (Table 1). During the firt cycle of loading, a paing-through flexural crack wa developed at the fixed ection of the column head. In the ame phae, flexural-hear hairline crack appeared along the column. With increaing cycle of loading, thee flexural-hear crack were minimally widened or developed (longitudinally) in contrat to the main flexural crack which kept increaing all the time (with imultaneou deterioration of the compreed zone). It i noteworthy that the 35 mm pacing between center of piral atifie the minimum requirement of the Greek Concrete Code, which pecifie that the pacing in quetion hould not exceed 20% of the diameter of the cyclical croection core. 6 CONCLUSIONS The tet reult, a well a the analytically derived value of thi tudy which i the "pilot" of a wider Reearch Program, reult to the following concluion: 1. In the cae of enuring the interlock of piral according to the internationally accepted minimum requirement for ecure interlock, the trength of the complex ection wa found to be approximately equal to the um of the trength of the two ingle cyclical overlapped ection. 2. The firt experimental reult confirm the correponding value approximately calculated on the bai of the ubtitute cro-ection, of an enveloping perimeter. 3. Structural element of a rectangular ection with interlocking piral when ubjected to eimic type loading have hown an excellent performance from a mechanical behavior tand point. Fig. 11 Seimic repone diagram of pecimen 3.
International Journal of Scientific & Engineering Reearch, Volume 5, Iue 8,Augut-2014 319 REFERENCES [1] ACI Committee 318, Building Code Requirement for Structural Concrete (ACI 318-99) and Commentary (ACI 318R-99). USA: American Concrete Intitute, 1999. [2] Concrete Deign Committee P3101, NZS 3101:2006, Concrete Structure Standard: Part 1 - The Deign of Concrete Structure. Wellington, New Zealand: Standard Council, 2006. [3] M.J.N. Prietley, Strength and Ductility of Bridge Subtructure. New Zealand: Road Reearch Unit, National Road Board, 1984. [4] American Aociation of State Highway and Tranportation Official, AASH- TO: Standard Specification for Highway Bridge (17th Edition). Wahington D.C.: Aociation General Office, 2002. [5] H. Tanaka, Effect of Lateral Confining Reinforcement on the Ductile Behaviour of Reinforced Concrete Column, PhD diertation, Department of Civil Engineering, Univerity of Canterbury, Chritchurch, New Zealand, 1990. [6] H. Tanaka and R. Park, Strength and ductility of reinforced concrete column with interlocking piral, Proceeding of 10 th World Conference on Earthquake Engineering, Madrid, Spain, 1992. [7] J.F. Correal, M.S. Saiidi, D.H. Sander and S. El-Azazy, Analytical Evaluation of Bridge Column with Double Interlocking Spiral, ACI Structural Journal, vol. 104, no. 3, pp. 314-323, May 2007. [8] H.G. Kwak, C.K. Choi and G.T. Chung, Direct Search Approach to Optimal Spiral Column Deign, Engineering Structure, vol. 18, no. 5, pp. 371-377, May 1996. [9] Q. Li and A. Belarbi, Seimic Behavior of RC Column with Interlocking Spiral under Combined Loading Including Torion, Procedia Engineering, vol. 14, pp. 1281-1291, 2011. [10] D.I. McLean and G.C. Buckingham, Seimic Performance of Bridge Column with Interlocking Spiral Reinforcement, Technical Report WA-RD 357.1, Wahington State Tranportation Center (TRAC), Wahington State Univerity, Pullman, Wahington, Sept. 1994. [11] J.F. Correal, M.S. Saiidi and D.H. Sander, Seimic Performance of RC Bridge Column Reinforced with Two Interlocking Spiral, Technical Report CCEER-04-06, Center for Civil Engineering Earthquake Reearch, Univerity of Nevada, Reno, Nevada, Aug. 2004. [12] G. Benzoni, M.J.N. Prietley and F. Seible, Seimic Shear Strength of Column with Interlocking Spiral Reinforcement, Proceeding of 12 th World Conference on Earthquake Engineering, Auckland, New Zealand, 2000. [13] J. Kim and C. Park, The Behaviour of Concrete Column with Interlocking Spiral, Engineering Structure, vol. 21, no. 10, pp. 945-953, Oct. 1999.