Bonded PT Slab-Column Connections with and without anwithoutdrop Panel Subjected Panel to Earthquake LoadingPaper Title Line

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1 Bonded PT Slab-Column Connetions with and without anwithoutdrop Panel Subjeted Panel to Earthquake LoadingPaper Title Line U. Prawatwong Suranaree Uniersity of Tehnology, Thailand P. Warnithai & C.H. Tandian Asian Institute of Tehnology, Thailand SUMMARY: Results of tests to failure on two 3/5-sale models of bonded post-tensioned interior slab-olumn onnetions, without and with drop panel, are presented. The study s goals were to: (1) deelop information on the seismi performane of typial bonded post-tensioned interior slab-olumn onnetions; and (2) inestigate the effet of adding drop panel to improe the seismi performane of the interior onnetions. A lateral quasi-stati yli loading routine, simulating earthquake ations, was applied to the models top olumns. Releant design equations suggested by ACI Building Code proisions for preenting stress-indued and deformationindued failures as well as preious similar tests by others were ompared with test results. We found that the presene of a drop panel effetiely and signifiantly enhanes the poor performane of the typial bonded posttensioned interior onnetions. Our study indiates that the existing ACI reommendation an be used for designing the bonded post-tensioned interior onnetions. Keywords: slab-olumn onnetions, drop panel, post-tensioning (PT), punhing shear, bonded tendons 1. INTRODUCTION The use of post-tensioned slabs for building strutural systems has beome inreasingly popular around the globe, but little researh has been onduted on the seismi performane of bonded posttensioned slab-olumn onnetions. It is widely known that slab-olumn onnetions are the most ritial regions in a flat plate system. Under a strong earthquake ground motion, sudden and brittle punhing failure may our at a slab-olumn onnetion region due to a ombination of diret graity shear and eentri shear from exessie earthquake-indued unbalaned moment between slab and olumn. In addition, extensie raks in the onnetion region aused by repeated reersals of large lateral deformation may signifiantly deteriorate the shear strength of the onnetion. The punhing shear failure at one onnetion may, in turn, initiate a progressie ollapse of the entire building strutures as notoriously shown in literatures. Mithell et al. (1986) pointed out that suh failure is the primary mode of failure in ollapses of many waffle-slab and solid-slab during the 1985 Mexio earthquake. Although numerous experimental studies on the seismi performane of slab olumn onnetions hae been arried out oer the past four deades, most of them foused on the seismi response of reinfored onrete (RC) flat plates. A limited number of studies inestigated the seismi apaity of PT flat plates (Hawkins 1981, Fouth et al. 1990, Qaisrani 1993, Martinez Cruzado et al. 1994, Kang and Wallae 2006, Gayed and Ghali 2006). All tested PT speimens were hitherto made to represent unbonded flat plate onnetions. Therefore, the seismi performane of bonded PT slab-olumn onnetions has neer been examined. Few guidelines and little information are aailable to designers. This paper deals with reersed-yli tests to failure on two three-fifth sale models of prototype bonded post-tensioned interior slab-olumn onnetions. The first speimen, named S1, was arefully designed and onstruted to represent a typial PT slab-olumn onnetion with no drop panel

2 designed in Thailand. The seond speimen, named S2, was an improed design of S1 by adding a drop panel. Eah speimen was subjeted to a lateral quasi-stati yli loading routine to inestigate its seismi performane through the elasti and inelasti ranges and finally until failure. The results are ompared with existing design equations suggested by ACI Building Code proisions for preenting stress-indued and deformation-indued failures as well as preious similar tests by others. 2. DESCRIPTION OF TEST PROGRAM 2.1 Prototype Struture and Speimen Design A prototype building, within the range of typial multistory onstrution in Thailand, was used to design the saled down models. The prototype building was 200 mm slab thikness, 8400 mm spans in eah diretion, and 3000 mm story heights. The span/depth ratio was approximately 42, whih is ommonly used in pratie for flat plate strutures. Cross-setional areas of the olumns were designed with 400 x 800 mm. The span dimension (8400 mm) was seleted so that slab boundaries and olumn enter of the saled down models math tie-down loation of the strong floor in the Strutural Engineering Laboratory at Asian Institute of Tehnology (AIT). The relation of the model to the prototype is shown in Fig S1 and S2 were designed as 3/5-sale models of prototype interior slab-olumn onnetions. As eah speimen was deeloped based on the assumption that infletion points in the interior onnetion under earthquake-type loading our at slab mid-span and olumn mid-story, half the total height of an interior olumn aboe and below the slab and half of the slab spans between adjaent olumns on all four sides were modeled. Pin onnetions were attahed to the points of ontra-flexure under lateral loading. This model of onnetion was designed to produe bending moment and shear of the slab omparable to the prototype in the iinity of the olumn where the most damage was expeted. Slab-olumn onnetion 3 m. 3 m. 3 m. 1.8 m. Lateral load Moment diagram 8.4 m. 8.4 m. 8.4 m. 8.4 m. (a) Full sale prototype 5.0 m. (b) Test speimen Figure 2.1. Relation of speimen to prototype struture 5700 N Loading Reation wall MTS Atuator Load ell DT Piot Pin-ended bar Strong floor Hinge 840 Plan iew Dimension in mm Eleation Figure 2.2. Interior slab olumn onnetion speimen with drop panel and its dimensions

3 2.2 Desription of Speimens Eah of the speimens in the series was idential in slab dimension, olumn dimension, tendon layout, and prestressing fores. The speimens were of normal weight onrete, 5700 mm square, 120 mm thik, and 250x mm olumn in the enter of the panel (Fig. 2.2). The speimen S1 without drop panel, whih was used as the ontrol speimen, was modeled after typial onnetions found in most PT flat plate buildings in Thailand. On the other hand, the speimen S2 ommonly followed the typial detail and loading of the speimen S1. The major ariable for S2 was the additional drop panel. The additional drop panel in S2 was 1600 mm square and projeted below the slab 80 mm. The supplementary reinforing bars in S2 were proided and plaed in suh a way that the respetie speimen may hae better seismi performane than that of the speimen without drop panel. Fig. 2.3 and 2.4 show the reinforement details of eah of the speimens x x x550 5x550 Strain gauges 3x S11 S10 S9 S1 S2 S3 S4 S5 S6 S7 S x 290 2x x550 (b) Bottom bonded reinforement (10 mm dia. ribbed bars ) 20 (a) Distribution of prestressing strands (12.7 mm dia.) N 9x80 Anhorage plate 12-DB16 Column top iew 7x h slab 2 + 3h slab () Top bonded reinforement (10 mm dia. ribbed bars 2000 mm long) 120 (d) Column reinforement Prestressing strand f 12.7 mm (0.5 in) 250 RB RB Column main bars 12-DB16 (16 mm. dia. ribbed bars) Figure 2.3. Reinforement for Speimen S1 (dimension in mm) The PT tendons in both models were ASTM A-416, Grade 270, 12.7 mm (1/2 in) diameter, seen-wire stress-relieed strands. Eight tendons were banded in the diretion of loading (N-S diretion) while the other eight tendons were uniformly distributed in the orthogonal diretion (E-W diretion). In eah diretion, there were no tendons passing through the olumn, similar to typial onnetions found in most PT flat plate buildings in Thailand. Eah tendon was inserted into a flat (20 mm in height) galanized dut to preent bonding to the onrete before prestressing. To preent damage due to high onentrations of stresses at the edges of the slab, an edge beam with suffiient reinforing bars was proided on all sides of the slab. Distribution of prestressed tendons and their profile in slab of S1 and S2 are shown in Fig. 2.3a and 2.4a, respetiely. Supplementary reinforement bars in peak negatie moment in the iinity of olumns were proided in the slab of S1 as shown in Fig The top reinforements orresponded to a negatie moment reinforement ratio of within an assumed effetie width of +3h in eah diretion, where is

4 olumn dimension measured in the transerse diretion of the top reinforement, and h is the oerall thikness of the slab. In addition, minimum areas of temperature and shrinkage reinforement were proided in an orthogonal mesh as bottom reinforement bars in the slab as shown in Fig. 2.3b. All bar arrangements were in suh a way that the top and bottom bars in the diretion of loading were plaed at the outmost layer. A nominal lear onrete oer of 10 mm was speified for both top and bottom reinforement x x x x550 Strain gauges Strain gauges 3x S1 S2 S3 S4 S11 S10 S9 S5 S6 S7 S x B1 80 (b) Bottom bonded reinforement (10 mm dia. ribbed bars ) 20 3x275 (a) Distribution of prestressing strands (12.7 mm dia.) 3x275 N 9x200 W drop + 3h slab 160 6x Bottom Layer 100 D Top Layer Column main bars 8-DB25 (25 mm. ribbed bars) Anhorage plate RB 2 RB 8-DB25 Prestressing strand f 12.7 mm (0.5 in) W drop + 3h slab () Top bonded reinforement (10 mm dia. ribbed bars 2800 mm long) 3x200 3x200 0 (d) Drop panel reinforement (10 mm dia. ribbed bars) (e) Column reinforement Figure 2.4. Reinforement for Speimen S2 (dimension in mm) The drop panel in S2 was reinfored with DB10 (10 mm diameter) deformed bars at the bottom fae to ounter tensile stresses aused by positie bending whih might be indued by signifiant unbalaned moment due to lateral yli loading during the test. The reinforement ratio of the drop panel, ρ s, drop = 0.003, was the same in eah diretion. To preent anhorage failure of the bottom reinforing bars in the drop panel, the ertial legs with deelopment length of 40 times bar diameter were extended into the main slab. Fig. 2.4d shows the layout of the reinforing bars within drop panel. S2 also ontained the supplementary top reinforement bars at the top of its slab aording to Setion of ACI building ode similar to those of S1. The supplementary top reinforement bars, whih were the same number of top bars as in S1, were distributed along an assumed effetie support width of W drop +3h in the middle of the olumn in both diretions (Fig. 2.4), where W drop is the width of the drop panel, and h is the total thikness of the slab outside the drop panel. The assumed effetie support width was aording to Setion of ACI building ode. The supplementary top reinforement ratio within the drop panel orresponded roughly to in eah diretion. The top bars were extended into the slab around the drop panel and ut off at a distane of 600 mm from the edge of the drop panel to proide deelopment length as reommended in Setion of ACI 318-

5 08. In addition, two ontinuous bottom bars were plaed oer the olumn in eah diretion aording to Setion and of the ode to preent progressie ollapse in the eent of a onnetion shear failure. In eah of the speimens, suffiient transerse and longitudinal reinforing bars were proided so the olumn would remain elasti without experiening either flexural or shear failure during the test. In addition, ertial prestressing fores of 588 kn were applied to the olumn by four unbonded tendons to simulate the effets of graity loads from the upper floors. The details of reinforement for the olumns in S1 and S2 are gien in Fig. 2.3d and 2.4e, respetiely. Eah of the speimens was ast with ready-mix onrete. The model slabs were prestressed with eight tendons in eah diretion when the onrete slab gained suffiient strength. An effetie fore of kn, orresponding to a stress of 0.80 f pu, was applied to eah tendon to produe the aerage prestress leels shown in Table 2.1. After the tendons were prestressed and the end reesses were filled, all galanized duts were grouted to proide an effetie bond between the tendons and the duts. Table 2.1. Summary of Parameters and Properties of Model Slabs Property (1) Slab S1 (2) Slab S2 (3) 1. Thikness of slab, in mm Drop panel size, in mm None 1600 x 1600 x Column height, in mm Cross-setional area near ritial setion, sq mm 6.84 x x Effetie depth of strands, d p, in mm N-S diretion E-W diretion Conrete strength, in MPa f i at time of stressing f at time of testing 7. Steel strength of strands, in MPa f pu, tensile strength f py, yield strength at 1% elongation 8. Steel strength of DB10, in MPa f u, tensile strength f y, yield strength 20.0 (4 days) 41.1 (43 days) (6 days) 45.9 (43 days) Aerage ompressie stress f p, in MPa P/A in N-S diretion P/A in E-W diretion Testing of Speimens It is well known that a major parameter that influenes the lateral displaement apaity of slab olumn onnetions is the graity shear ratio (V g /V 0 ), where V g is the diret graity shear fore ating on the slab ritial setion and V 0 is the slab punhing strength in the absene of moment transfer as defined in ACI The lateral displaement apaity and dutility generally drops as the magnitude of the onnetion graity shear ratio (V g /V 0 ) inreases (Pan and Moehle 1989, Kang and Wallae 2006). Hene, S1 was loaded by a large number of sand bags on top and below the slab to simulate the graity shear ratio (V g /V 0 ) of 0.28, whih is approximately the aerage alue of those found in slab-olumn frame buildings in Thailand (Warnithai et al. 2004). The same graity loading was also applied to S2. But sine the slab in the onnetion region was thiker due to the presene of drop panel, the graity shear ratio of 0.13 was obtained for this ase. The seismi moement was simulated by applying lateral displaement at the top of the olumn through a MTS sero ontrolled hydrauli atuator as depited in Fig The hydrauli atuator was mounted to a rigid reation wall. A typial displaement ontrolled reersed yli lateral loading test was arried out to both speimens with monotonially inreasing target drifts of 0.25%, 0.50%, 0.75%,

6 1.00%, 1.25%, 1.50%, 2.00%, 2.50%, 3.00%, 4.00%, and so on At eah target drift, two omplete yli displaement loops were onduted. The loading was terminated after the punhing one had formed ompletely. Note that the respetie target drift is defined as the ratio of the lateral displaement of olumn at lateral loading point to the olumn height, whih is 1.8 meter. During the testing of both speimens, all measurement data were reorded at eah loading step. A load ell and a displaement transduer were installed at top of the olumn (Fig. 2.2) to monitor detailed oerall fore-displaement relations of the onnetions throughout the loading history. The strain in some post-tensioning tendons and supplementary reinforing steel were monitored by eletrial resistane type strain gauges installed on the bars prior to asting the speimens on loations as shown in Fig. 2.3 and 2.4. Further details of instrumentation an be found in Pongpornsup (2003) and Tandian (2006). 3. EXPERIMENTAL RESULTS 3.1 Oerall Response Due to spae limitation, only some results are presented in this paper. Fig. 3.1a and 3.1b gie the lateral fore-drift relations of S1 and S2, respetiely. The figures show that both speimens displayed long and narrow hysteresis loops, demonstrating a limited ability to dissipate energy of bonded PT interior slab-olumn onnetions. As the drift leel beame higher, in general, speimen stiffness degraded more and the hysteresis loops were wider. No signifiant pinhing was obsered from the hysteresis loops of either speimen. Both S1 and S2 experiened punhing failure. Punhing failure in eah of the speimens was haraterized by a sudden drop of lateral load-arrying apaity to less than 50% of its maximum fore attained during the tests. S1, without a drop panel, ould only withstand 2.0% drift (Fig. 3.1a). After the maximum lateral load of 107 kn was attained, this speimen suddenly failed in brittle punhing shear and ompletely lost its lateral strength and stiffness while no peak load saturation was pereied in adane. It is likely that the higher graity shear ratio in the first test was a key fator that aused early failure in punhing shear in this speimen. S2 (with drop panel) attained 80% higher lateral load-arrying apaity than the ontrol speimen (S1). As an be seen in Fig. 3.1b, S2 exhibited a saturation of peak load for a drift of 2% to 6%, indiating that flexural yielding took plae long before punhing failure. Until the end of the test, the speimen with the additional drop panel showed muh higher drift apaity at about 6% at punhing failure than the one without the drop panel. Lateral fore (kn) Hystereti response Enelop ure 1 Peak load 1 and maximum drift 2 Punhing failure of slab Speimen drift (%) Ultimate Capaity Lateral Load (kn) (a) Speimen without drop panel Moment (kn.m) Drift (%) Lateral fore (kn) Hystereti response Enelop ure 1 Peak load 2 Maximum drift 3 Punhing failure of slab Speimen drift (%) (b) Speimen with drop panel Ultimate Capaity Lateral Load (kn) Moment (kn.m) Drift (%) Figure 3.1. Lateral fore-drift results

7 3.2 Comparison of Shear Stresses In the following, the ACI model for the design of slab-olumn onnetions as shown in Fig. 3.2 is used to alulate the eentri shear stress due to a graity shear V u and an unbalaned moment M u along the ritial setion at d/2 from the olumn fae. For the speimen with drop panel (S2), two ritial setions as shown in Fig. 3.2a must be inestigated, where d 1 is the aerage effetie depth of the slab within thikened drop panel region and d 2 is the aerage effetie depth of the slab outside drop panel. Drop panel Column (a) d 1/2 Critial setion 1 Critial setion 2 d 2/2 2 + d D C 1 + d Column CD (b) AB A Critial setion d/2 B h Speimen without drop panel b 1 = 1 + d, b 2 = 2 + d C D V u B Column () M u A u( AB) Shear stress V A u u AB M J 1 1/(1 (2 / 3) b1/ b2) Speimen with drop panel Critial setion 1: b 1 = 1 + d 1, b 2 = 2 + d 1 Critial setion 2: b 1 = b 2 = W drop + d 2 Figure 3.2. Critial setions at interior olumn for linear arying shear stress aording to ACI Building Code (a) slab with drop panel; (b) slab without drop panel; () stress distribution along ritial setion. The maximum shear stresses at the ritial setions are expressed by the well-known equation shown below. u( AB) V A u u AB (3.1) M J where A = b 0 d; b 0 = 2(b 1 + b 2 ) = perimeter of ritial setion for shear in slab; d is the effetie depth of the slab; AB is the distane from the entroidal axis of the ritial setion to line AB (Fig. 3.2b); J is a property of the ritial perimeter analogous to the polar moment of inertia; and γ is the fration of the unbalaned moment transferred by eentriity of shear stress and is gien in Fig Eqn. 3.1 shows that the maximum stress is the sum of uniformly distributed graity shear and nonuniform lateral-fore-indued shear. The graity shear V u in eah speimen is omputed from a linear finite analysis, whih may hae some estimated error, but the error is not so important sine the graity shear stress is low when ompared with the lateral-fore-indued shear (Table 3.1). The lateral-fore-indued (or moment-indued) shear is estimated from γ M u. For eah speimen, the unbalaned moment M u an be aurately determined by multiplying the peak lateral fore by the olumn height (1800 mm) of the speimen. Based on the peak unbalaned moment (M u ) and the graity load (V u ) on the test speimens, the maximum shear stresses aording to the ACI model for S1 and S2 were obtained and listed in Columns 7 of Table 3.1. Table 3.1. Ultimate Shear Stresses a V u (kn) (2) M u (kn.m) (3) From diret shear (5) Shear stress, u (MPa) From moment transfer (6) Speimen Total u (1) (4) (7) (8) S S2 (Inner setion) S2 (Outer setion) Notes: a No load fators were used in alulations. / f

8 To apply Eqn. 3.1 to PT slab-olumn onnetions, howeer, some alue must be assumed for the effetie depth d. It is appropriate to take d as the greater of two alues, the atual effetie depth (d) or 0.80h, in aordane with the onepts of ACI For PT slabs in both speimens, all effetie depths were less than 0.8h and therefore the latter alue (0.8h) was used. In Fig. 3.3a, the maximum shear stresses u of S1 and S2 in Table 3.1 are plotted and ompared with shear stress limits expressed by Eqn of ACI and by preious works from other inestigators. The test data from preious works, represented by the blak dots, were summarized by ACI-ASCE Committee 423 (1974). They were mostly obtained from tests onduted for onnetions transferring shear only, and all tested PT speimens were unbonded flat plate onnetions that failed in shear. These test data show learly that though the normalized shear stress at failure generally inreases with the inrease in f p as predited by Eqn of ACI, the stress is signifiantly higher than the ode-speified limit, indiating a built-in safety margin of the ode equation. To determine the true stress limit, an empirial best-fit equation ( u = 0.46 (f ) 1/ f p ) was deried from these test data as depited in Fig. 3.3a. This best-fit equation therefore represents the most likely alue of shear stress at failure in slab-olumn onnetions Best-fit line f f p S1 (without drop panel) S2 (with drop panel) Stress-indued failure predited by the best-fit equation in Fig. 3.3a (for Speimen S2) f S1 S2 f f p (Eqn , ACI ) f mm Shear stress limit by ACI (for Speimen S2) Shear band S2 0.2 PT Unbonded (ACI-ASCE Committee 423 (1974)) 0.1 PT Bonded (This study) f p / f E 550 mm Cut at plane perpendiular to moment axis in S2 at end of test Speimen drift (%) -7 (a) (b) Figure 3.3. (a) Test data of Speimen S1 and S2 ersus ACI equation, (b) ariation of maximum shear stress on ritial setion of the test speimens with speimen drift Fig. 3.3a shows that the shear stresses at failure in S1 and S2 are both higher than the orresponding ode-speified limits, suggesting that the ode equation an be onseratiely used for the design of bonded PT slab-olumn onnetions against stress-indued failure. For S1, where a sudden punhing shear ourred at a low drift leel while the stress was still inreasing (Fig. 3.3b), the stress at failure is ery lose to the alue predited by the best-fit equation. The result of S1 therefore onforms well with those of aailable experimental data where failures belong to stress-indued type. In S2, howeer, the stress at failure was higher than the ode-speified limit but signifiantly lower than the alue predited by the best-fit equation. Moreoer, the shear stress beame saturated at the drift leel of around 2% (Fig. 3.3b), but the punhing shear failure ourred muh later at the drift leel of 6%. S2 obiously showed dutile behaiour as opposed to the brittle behaiour found in S1. The punhing shear failure at the high drift of 6% in S2 was belieed to happen as a result of slab shear strength degradation by flexural raks in the slab ritial region. When the degraded shear strength dropped below the saturated shear stress, punhing shear failure deeloped.

9 3.3 Comparison of Drift Capaity For seismi design, ACI proides guidane for the ealuation of shear reinforement requirements at slab-olumn onnetions and design story drift limit, whih is empirially bilinear as a funtion of graity shear ratio. This limit is based primarily on tests of isolated, RC slab-olumn onnetions subjeted to quasi-stati loading. Fig. 3.4 shows a plot of the graity shear ratio and drift apaity at punhing of both speimens from the urrent study, along with other test results of slab-olumn speimens without shear reinforement. Most of the test results of RC slab-olumn speimens were olleted and ompiled by Pan and Moehle (1989), while those of unbonded PT slab-olumn interior onnetions were tested by Trongtham and Hawkins (1977) and Qaisrani (1993) and summarized by Kang and Wallae (2006). ACI design drift limit for slab-olumn onnetions is also plotted in Fig. 3.4 for referene. Contrary to the results of unbonded PT slab-olumn onnetions, where the drift apaity is more than twie ACI drift limit in eery ase, the results of the two bonded PT slab-olumn onnetions do not show that they always possess higher drift apaity. Instead, the results are more or less onsistent with those of RC speimens, suggesting that ACI design drift limit ould also be used for bonded PT slab-olumn onnetions. Drift apaity (%) S2 S1 RC Slab-Column Connetion PT Unbonded (Trongtham and Hawkins 1977) PT Unbonded (Qaisrani 1993) PT Bonded (This study) ACI Drift limit Graity shear ratio (V g /V 0 ) Figure 3.4. Graity shear ratio ersus drift apaity at punhing for RC and PT slab-olumn onnetions 4. CONUSIONS 1. S1 showed non-dutile behaior under reersed yli loading. A sudden stress-indued punhing shear failure deeloped at a low lateral drift leel of 2%. The shear stress leel at failure mathed well with the aerage stress limit of unbonded PT slab-olumn onnetions, suggesting that the existing ACI s formula for stress limits an also be applied when designing bonded PT slab-olumn onnetions. 2. Adding a drop panel to a bonded PT slab-olumn onnetion effetiely and signifiantly enhanes its oerall seismi performane. S2 exhibited dramati inreases in lateral strength and lateral deformation apaity ompared to those of S1. 3. Dutile behaior in S2 was learly demonstrated by its lateral fore-drift relationship. This was eidently aused by flexural yielding in the slab, leading to shear stress saturation in the slab s ritial region at a leel below shear strength. Stress-indued failure was therefore inhibited. S2 finally failed by punhing shear after a ery high drift leel of 6%, when the degraded shear strength dropped below the saturated shear stress. The results also suggest that ACI s design drift limit ould be used for bonded PT slab-olumn onnetions.

10 ACKNOWLEDGMENTS This experimental work was onduted with funding proided by the Thailand Researh Fund (TRF) and the Siam City Cement Publi Company Limited (SCC). The prestressed strands, duts, and anhors used in the tests were donated by the Conrete Produts and Aggregate Company (CPAC) Limited. Heartfelt gratitude is oneyed to TRF, SCC, and CPAC for supporting this researh program. REFERENCES ACI-ASCE Committee 423 (1974). Tentatie Reommendations for Prestressed Conrete Flat Plates. ACI Journal. 67:2, ACI Committee 318. (1995). Building Code Requirements for Strutural Conrete (ACI ) and Commentary. Amerian Conrete Institute, Farmington Hills, US. ACI Committee 318. (2002). Building Code Requirements for Strutural Conrete (ACI ) and Commentary. Amerian Conrete Institute, Farmington Hills, US. ACI Committee 318. (2008). Building Code Requirements for Strutural Conrete (ACI ) and Commentary. Amerian Conrete Institute, Farmington Hills, US. Fouth D.A., Gamble W.L. and Sunidja H. (1990). Tests of post tensioned onrete slab edge olumn onnetions. ACI Strutural Journal. 87:2, Gayed R.B. and Ghali A. (2006). Seismi resistant joints of interior olumns with prestressed slabs. ACI Strutural Journal. 103:5, Hawkins, N.M. (1981). Lateral load resistane of unbonded post tensioned flat plate onstrution. PCI Journal. 26:1, Kang, T.H.K. and Wallae, J.W. (2006). Punhing of Reinfored and Post-Tensioned Conrete Slab-Column Connetions. ACI Strutural Journal, 103:4, Martinez Cruzado, J.A., Qaisrani, A.N. and Moehle, J.P. (1994). Post tensioned flat plate slab olumn onnetions subjeted to earthquake loading. Fifth U.S. National Conferene on Earthquake Engineering. Vol II: Mithell, D., Adams, J., Deall, H.R., Lo, C.R. and Weihert D. (1986). Lessons from the 1985 Mexian earthquake. Canadian Journal of Ciil Engineering. 13:5, Pan, A. and Moehle, J.P. (1989). Lateral displaement dutility of reinfored onrete flat plates. ACI Strutural Journal. 86:3, Pongpornsup, S. (2003). Seismi Performane of Post-Tensioned Interior Flat Slab-Column Connetions, Master Thesis no. ST 03-18, Asian Institute of Tehnology, Thailand. Qaisrani, A.N. (1993). Interior Post-Tensioned Flat-Plate Connetions Subjeted to Vertial and Biaxial Lateral Loading, Dotoral Dissertation, Department of Ciil Engineering, Uniersity of California-Berkeley, California, US. Trongtham, N. and Hawkins, N.M. (1977). Moment Transfer to Columns in Unbonded Post-Tensioned Prestressed Conrete Slabs, Report SM77-3, Department of Ciil Engineering, Uniersity of Washington- Seattle, Seattle, Washington, US. Tandian, C.H. (2006). Seismi Performane of Bonded Post-Tensioned Interior Flat Slab-Column Connetions with Drop Panel, Master Thesis no. ST 06-16, Asian Institute of Tehnology, Thailand. Warnithai, P., Pongpornsup S., Prawatwong U. and Pimanmas A. (2004). Seismi performane of post tensioned interior flat slab olumn onnetions. Third International Symposium on New Tehnologies for Urban Safety of Mega Cities in Asia Agra, India.