EXPERIMENTAL INVESTIGATION OF ECCENTRIC REINFORCED CONCRETE BEAM-COLUMN-SLAB CONNECTIONS UNDER EARTHQUAKE LOADING

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1 13 th World Conferene on Earthquake Engineering Vanouver, B.C., Canada August 1-6, 24 Paper No. 215 EXPERIMENTAL INVESTIGATION OF ECCENTRIC REINFORCED CONCRETE BEAM-COLUMN-SLAB CONNECTIONS UNDER EARTHQUAKE LOADING BURCU BURAK 1 AND JAMES K. WIGHT 2 SUMMARY The inelasti behavior of beam-to-olumn joints has been studied sine 196 s; however, there is still limited information on eentri onnetions, in whih the enterline of the spandrel beam does not oinide with the entroid of the olumn. In this experimental study, the seismi behavior of three 3/4- sale eentri beam-olumn-slab subassemblies was investigated. The main design parameters were seleted as the eentriity, normal beam width, and olumn setion aspet ratio. The eentriity between the enterline of the spandrel beam and entroidal axis of the olumn was seleted as a design variable beause some buildings with eentri spandrel beams exhibited extensive damage during earthquakes and previous tests of planar (two-dimensional) speimens indiated early deterioration of joint shear strength for these types of strutures. The main design variable for the olumn was the setion aspet ratio (width vs. depth) to examine if the entire joint region of the retangular olumn works under applied shear loading as effetively as a square olumn. Eah speimen was tested twie. First, lateral loading was applied in the plane of the spandrel beam, then the speimen was rotated 9 degrees and the loading was applied in the plane of the normal beam that is perpendiular to the spandrel beam. The major design variable for the normal beam was its width, whih was larger than the width of the supporting olumn for the last test speimen, to investigate the onfinement of the joint region provided by the wide normal beams, and the transfer of moment from the wide beam to the olumn by a previously loaded spandrel beam. The experimental results indiated that when exterior onnetions have the floor system with slab and beams spanning in two perpendiular diretions, the influene of the spandrel beam eentriity on the seismi behavior of the joint region hanges signifiantly. When the speimens were ompared to previous tests, it was observed that the damage in the joint region was not as severe, the speimens have full hysteresis urves with high energy dissipation apaities, and the deterioration of joint shear stiffness and strength were delayed due to the additional torsional stiffness resulting from the use of a floor system. 1 Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Mihigan, Ann Arbor, USA, bburak@engin.umih.edu 2 Professor, Department of Civil and Environmental Engineering, University of Mihigan, Ann Arbor, USA, jwight@engin.umih.edu 1

2 INTRODUCTION Eentri onnetions, in whih the axis of the spandrel beam is offset from the axis of the olumn, are used in exterior frames of reinfored onrete buildings due to arhitetural onsiderations. In this type of onnetion, the spandrel beams, whih are narrower than the olumn, are generally flush with the exterior fae of the olumn. The eentriity between the beam and the olumn results in the development of torsion in the onnetion region under lateral loading parallel to the exterior edge of the subassembly. This torsion in the joint produes additional shear stresses and affets the shear apaity of the joint. An experimental investigation was arried out to develop new data and to further study the yli behavior of eentri onnetions. Three 3/4-sale exterior reinfored onrete beam-olumn-slab onnetions were tested under reversed yli loading. The speimens are three-dimensional and onsist of two spandrel beams, a normal beam in the transverse diretion, and a floor slab. Lateral load was applied in two prinipal diretions, one plane at a time, to determine the effet of prior loading on performane of the onnetion. First, a ontrol speimen, designed following the reommendations of ACI-ASCE Committee 352 [1] and ACI [2], was tested. Based on the test results, the other speimens were designed by modifying the eentriity, beam and olumn setion aspet ratios, and the level of joint shear stress to examine their effet on joint behavior. The performane of the eentri onnetions was evaluated by examining the raking pattern, lateral load versus story drift response, beam rotations, energy dissipation apaity, and stiffness deterioration of the speimens. One of the main design variables was seleted to be the eentriity of the spandrel beam with respet to the olumn. Prior tests [3, 4], without a normal beam and a floor slab, have indiated that the eentriity of the spandrel beam leads to unsymmetrial damage in the joint, early deterioration of the joint shear strength, and loss of anhorage for the spandrel beam reinforement. In addition, some buildings with eentri spandrel beams exhibited extensive damage under earthquake loading, while other reinfored onrete buildings in the same area showed very little or no damage [5, 6]. The major design variable for the olumn is taken as the setion aspet ratio (width vs. depth). The experimental program by Raffaelle and Wight [3] indiated that the effetive joint width for resisting shear fore depends on the olumn setion aspet ratio. Therefore, both square and retangular olumns were tested in this experimental program to study the orrelation between the olumn setion aspet ratio and the effetive joint width. The width of the normal beam was hosen as another design variable. The last speimen was built as a wide-beam struture in whih the normal beam width was larger than the olumn width. In a wide-beam struture, some of the beam longitudinal reinforement is anhored in the spandrel beams outside the olumn ore. Wide beam longitudinal reinforement anhored in the olumn ore transfers tension diretly to the olumn. The remaining reinforement anhored in the spandrel beams transfers tension to the olumn through torsion in the spandrel beam. If the spandrel beam is unable to transmit the applied torsion from the wide beam to the olumn, the full moment strength of the wide beam annot be developed. The last speimen provides information on the effet of prior loading on the bond strength of the wide beam reinforement anhored in the spandrel beam. 2

3 EXPERIMENTAL PROGRAM Test Setup and Speimens Three exterior reinfored onrete beam-olumn-slab subassemblies were tested under reversed yli loading. Eah speimen onsists of top and bottom olumns, two spandrel beams, a normal beam, and a floor slab. The spandrel beams are flush with the exterior fae of the olumn, whih results in an eentriity between the enterline of the beam and the entroidal axis of the olumn. The normal beam in the transverse diretion makes a onentri onnetion with the olumn. Columns and beams are pin supported at their mid-heights and mid-spans, where infletion points are likely to our during a seismi event. The speimens were subjeted to quasi-stati yli loading in two prinipal diretions, one plane at a time. They were loaded initially in the spandrel beam diretion (Fig. 1a), then they were rotated 9 degrees and loaded in the normal beam diretion (Fig. 1b). Loading in the spandrel beam diretion gives a diret orrelation between these three-dimensional speimens and the prior testing of planar speimens with no slab and normal beam. Loading in the normal beam diretion enables the determination of the effet of prior loading on performane of the onnetion. (a) (b) Figure 1: Loading of Speimens in (a) Spandrel and (b) Normal Beam Diretions Fig. 2 shows a sketh of the test setup. An axial load of approximately five perent of the axial apaity of the olumn was applied with hydrauli jaks. The lateral load was applied horizontally through the top of the olumn following a predefined displaement history. In eah diretion, twenty yles of lateral displaement was applied to eah speimen, ranging from.5% to 5.% story drifts to simulate the inelasti loading during an earthquake. Eah yle to a new drift level is applied twie to evaluate the loss of strength and stiffness of the speimens during the repeated yles. Some 1.% drift yles were interspersed into the displaement history to evaluate the residual stiffness of the speimens. 3

4 East (-) West (+) 1 kip (45 kn ) Atuator Axial Load Supplied by Post-tensioning Jaks Reation Wall Pin 16 (4.9 m.) Pin Axial Link 8 6 (2.6 m) 7 4 (2.2 m) Axial Link Load Cell Pin Strong Floor Universal Pin Load Cell Pin Figure 2: Test Setup For loading in the spandrel beam diretion, the following equation for the effetive joint width, b j, proposed by the seond author to ACI-ASCE Committee 352, governed in the design of the speimens: b j = b b + Σ m h /2 where, b b = design width of beam, m = slope to define the effetive width of joint transverse to the diretion of shear. For all the speimens, the eentriity between the beam enterline and olumn entroid exeeds b /8; therefore, m =.3, b = width of olumn transverse to the diretion of shear, h = depth of olumn in the diretion of load being onsidered. For loading in the normal beam diretion, the above equation was also heked for the design of the onnetions using m =.5, beause there is no eentriity between the normal beam and the olumn. However, the governing equation turned out to be (b b + b )/2. In the third speimen, whih has a wide normal beam, the effetive joint width was taken as b + (b b - b )/4, beause the equation proposed in the urrent odes is found to be onservative for wide-beam strutures. Design variables and the dimensions of the speimens are given in Table 1. In order to enfore beam plasti hinging rather than joint failure or olumn plasti hinging, the strong olumn-weak beam philosophy (M r > 1.) was used in the design. Minimum shrinkage and temperature reinforement was used in both diretions of the slab. Speimen 1 is designed as a ontrol speimen following the reommendations of ACI-ASCE Committee 352 [1] and ACI [2]. It has a square olumn and spandrel and normal beams with typial dimensions. Other speimens were designed after the first one was tested; the eentriity, beam and olumn setion aspet ratios, and the level of joint shear stress were modified to examine their effet on onnetion performane. For the last two speimens, the spandrel beam eentriity is almost doubled. Moreover, retangular olumns with a setion aspet ratio of 1.5 were used in these speimens to examine the influene of this ratio on the effetive joint width. The dimensions of the spandrel and normal beams were also modified to investigate the effet of beam setion aspet ratio. 4

5 Table 1: Member Dimensions and Design Variables Speimen 1 Speimen 2 Speimen 3 Column Spandrel Beam Normal Beam Joint 14 x14 14 x21 14 x21 Dimensions (356 x 356 mm) (356 x 533 mm) (356 x 533 mm) ρ x15 1 x18 1 x18 Dimensions (23 x 381 mm) (254 x 457 mm) (254 x 457 mm) ρ top ρ bottom M r e 3 (76 mm) 5.5 (14 mm) 5.5 (14 mm) h ol /d b,beam h beam /d b,ol Dimensions 12 x15 (35 x 381 mm) 12 x18 (35 x 457 mm) 3 x12 (762 x 35 mm) ρ top ρ bottom M r h beam /d b,ol ν j-s ν j-n 14.1 f psi (1.2 f MPa) 9.4 f psi (.78 f MPa) 14.4 f psi (1.2 f MPa) 9.1 f psi (.76 f MPa) 14.4 f psi (1.2 f MPa) 13.1 f psi (1.9 f MPa) ρ = Reinforement ratio, M r = Moment strength ratio; slab inluded as ompression flange for positive bending and slab bars inluded as tensile reinforement for negative bending, e = Eentriity between the spandrel beam enterline and the entroidal axis of the olumn, h ol /d b,beam = Ratio of olumn height to beam bar diameter, h beam /d b,ol = Ratio of beam height to olumn bar diameter, ν j-s = Design joint shear stress for loading in the spandrel beam diretion, ν j-n = Design joint shear stress for loading in the normal beam diretion. EXPERIMENTAL RESULTS Crak Development The observed raking pattern at the exterior and interior faes of Speimen 1 at the end of testing in both diretions is given in Fig. 3. During the first test, while loading in the spandrel beam diretion, flexural raks were observed in the spandrel beams at the first yle to.5% drift. Diagonal raks ourred in the joint region at approximately 1% story drift; however, they remained narrow until the end of the test. The number and width of torsional rak formed in the spandrel beam and onnetion region were also less than expeted. This minor damage orrelates well with the maximum measured joint shear deformation of 1.%. Prior tests [3, 4] indiated that the eentriity of the spandrel beam leads to 5

6 unsymmetrial damage in the joint with severe raking on the exterior fae (Fig. 4). However, Speimen 1 showed only minor damage on both joint faes. For loading in the normal beam diretion, flexural raking of the normal beam started at.5% drift for this speimen. Additional diagonal shear raks formed in the joint after 1% story drift. Even at high drift levels, the speimen exhibited good behavior with almost no spalling of onrete in or near the joint region. (a) (b) Figure 3: Craking Pattern at the (a) Exterior and (b) Interior Faes of Speimen 1 (a) (b) Figure 4: Craking Pattern at (a) Exterior and (b) Interior Faes of a Prior Test Speimen [3] In Speimen 2, the number of raks inreased, the raks were wider, and spalling of the over onrete was observed at the exterior fae (Fig. 5). For loading in the spandrel beam diretion, some torsional raks were deteted in the spandrel beam and the joint region. In this speimen, flexural raks opened at the fae of the joint ore region rather than the beam-olumn interfae, whih was the ase for Speimen 1. A similar raking pattern was observed in an existing building with eentri onnetions that was damaged in the 1995 Kobe Earthquake (Fig. 6), whih shows that the testing proedure effetively simulates the earthquake loading. For this speimen, first spandrel beam flexural raks and joint diagonal shear raks formed at approximately.5% story drift. The damage orrelates well with the maximum measured joint shear deformation of approximately 2.5%. For loading in the normal beam diretion, flexural raking of the normal beam and additional diagonal shear raks in the joint were observed after.5% story drift. The raking pattern indiates that the entire joint region of the retangular olumn was working under applied loading. 6

7 (a) (b) Figure 5: Craking Pattern at the (a) Exterior and (b) Interior Faes of Speimen 2 Figure 6: Craking Pattern of a Building Damaged in 1995 Kobe Earthquake [5] The overall raking pattern observed in Speimen 3 (Fig. 7) was similar to that of Speimen 2. However, this speimen exhibited extensive spalling of onrete at the exterior fae of the onnetion region due to the joint geometry. The wide normal beam ould not onfine the joint region as well as a regular normal beam; therefore, the damage was onentrated at the exterior fae of the onnetion. For loading in the spandrel beam diretion, flexural raks opened at the fae of the joint ore region as in Speimen 2. First spandrel beam flexural raks and joint diagonal shear raks formed at approximately.5% story drift. For this speimen, the maximum measured joint shear deformation was 3.%, whih explains the extensive spalling of onrete. For loading in the normal beam diretion, some spalling was observed in the normal beam due to a lak of onfinement reinforement for the wide beam bars that are anhored outside the olumn. In this diretion, flexural raking of the normal beam and additional diagonal shear raks in the joint were observed at 1.% story drift. 7

8 (a) (b) Figure 7: Craking Pattern at the (a) Exterior and (b) Interior Faes of Speimen 3 Lateral Load versus Story Drift Response Previous test results [3, 4] showed that the eentriity of the spandrel beam leads to early deterioration of the joint shear strength and exessive pinhing of the load versus displaement hysteresis urves. However, as shown in Fig. 8a, Speimen 1 maintained its strength until the end of the test without any major pinhing of the hysteresis urves for loading in both diretions. When the behavior of Speimen 1 for loading in the spandrel beam diretion was ompared to a speimen tested by Raffaelle and Wight [3], whih had similar dimensions and reinforement, a lower eentriity level of 51 mm. (2 in.), but no floor slab and normal beam (Fig. 9), it is lear that inluding the floor system signifiantly improves the overall performane of eentri onnetions and delays the deterioration of joint shear stiffness and strength. The maximum joint shear deformation observed in their two-dimensional speimen was 2%, whih is twie the distortion observed in Speimen 1 of this experimental program. After 3% story drift in Speimen 1, when beam flexural deformations dominated the speimen response rather than diagonal raking in the joint region, hysteresis urves beame wider for loading in both diretions, whih shows the exellent energy dissipation apaity of this speimen. There is slight pinhing in the hysteresis urve of Speimen 2 for loading in the spandrel beam diretion (Fig. 8b), and the speimen lost a small perentage of its strength after 4% story drift mainly due to the higher eentriity level. However, the pinhing is still not as severe as in Fig. 9, although the eentriity is signifiantly higher. For loading in the normal beam diretion, pinhing was not observed beause very few additional diagonal shear raks formed in the joint. For loading in the spandrel beam diretion, the lateral load versus story drift response of Speimen 3 (Fig. 8) had more pinhing than that of Speimen 2, due to the lak of onfinement in the onnetion region resulting from the use of a wide normal beam. The total depth of the normal beam was less than threequarters of the total depth of the spandrel beam, whih is the minimum limit in the ode [2]. The strength loss, whih started after 3% story drift, was also higher in this speimen. Some pinhing is observed for this speimen for loading in the normal beam diretion due to the loss of anhorage for the wide beam longitudinal bars. The speimen was loaded to 7% story drift in the normal beam diretion to observe the failure mode; however, it maintained its strength until the end of the test. 8

9 Lateral Load (kn) Lateral Load (kn) Loading in Spandrel Beam Diretion Loading in Normal Beam Diretion Story Drift Loading in Spandrel Beam Diretion Lateral Load (k) Lateral Load (k) Lateral Load (kn) Story Drift Loading in Normal Beam Diretion Story Drift Story Drift Lateral Load (kn) Loading in Spandrel Beam Diretion Story Drift (a) Speimen 1 Lateral Load (k) Lateral Load (kn) (b) Speimen 2 Lateral Load (kn) () Speimen Loading in Normal Beam Diretion Story Drift Lateral Load (k) Lateral Load (k) Lateral Load (k) Figure 8: Lateral Load versus Story Drift Response of Test Speimens 9

10 Figure 9: Pinhed Hysteresis Curve of an Eentri Beam-Column Connetion in a Prior Test [3] Moment versus Beam Plasti Hinge Rotation Response The potentiometer layout on eah fae of the onnetion shown in Fig. 1 enabled the measurement of the beam plasti rotation and the onentrated rotation at the end of the beam. The beam plasti rotation is the rotation over the plasti hinging region aused by the flexural deformation of the beam. The end rotation is the onentrated rotation at the fae of the joint due to the flexural raks formed at the beam-to-olumn interfae, joint shear deformation, and slip of beam reinforement. The potentiometer that is touhing the olumn fae measures the total beam rotation, whih is the sum of the beam plasti rotation and the end rotation. The potentiometer that is onneted to a rod, whih is plaed adjaent to the olumn fae, measures only the beam plasti rotation. Figure 1: Potentiometer Layout to Measure Beam Rotations The moment versus rotation diagrams for Speimen 1 are given in Fig. 11, as an example. The large beam rotations and the wide urves shown in these graphs points out that beam rotations ontributed signifiantly to energy dissipation, espeially at high drift levels. The data obtained from the potentiometers demonstrated that for loading in the spandrel beam diretion, the ontribution of the beam plasti rotation to the total beam rotation was lower than that for loading in the normal beam diretion. The spandrel beam reinforement yielded in all the tests and the nominal moment apaity of the spandrel beams was reahed. Although, the yielding of some normal beam flange bars were at higher drift levels, the measured moment apaity of normal beams were very lose to the design values at the end of eah 1

11 test, exept for Speimen 3, whih had a wide beam as the normal beam. For loading in the normal beam diretion, some of the strain gages that are plaed on the flange bars did not reah the yield strain in all the tests. Detailed information on the spread of yielding is given elsewhere by the authors [7]. The reason for not reahing the yield strain is believed to be prior loading in the spandrel beam diretion, whih softened the joint and lowered the bond strength of the normal beam bars. This also inreased the ontribution of the end rotation to the total beam rotation in the normal beam diretion. Moment at Column Fae (kn-m) Moment at Column Fae (kn-m) Total Beam Rotation (rad) Moment at Column Fae (k-in) (a) Loading in the Spandrel Beam Diretion Total Beam Rotation (rad) Moment at Column Fae (k-in) Moment at Column Fae (kn-m) Moment at Column Fae (kn-m) Beam Plasti Rotation (rad) Beam Plasti Rotation (rad) (b) Loading in the Normal Beam Diretion Figure 11: Moment versus Beam Rotation Curves for Speimen 1 Energy Dissipation The energy dissipated in eah yle was omputed as the area enlosed by the hysteresis loops in the lateral load versus story drift urves. Then, these values were normalized by the energy dissipated during the first yle to 1% story drift to aount for strength differenes of the speimens. Fig. 12 shows the normalized energy dissipation apaity versus story drift response for Speimen 1, as an example. In this figure, the thik lines represent loading in the normal beam diretion, while the thin lines are for loading in the spandrel beam diretion. The solid lines represent the first yles and the dashed lines are for the repeat yles of eah drift level. As an be observed in Fig. 12, the speimen dissipated more energy in the normal beam diretion beause the onentri beam forms a better mehanism than the eentri one for dissipating energy. For the repeat yles, the speimen lost 1 to 3 perent of its energy dissipation apaity from the first yles Moment at Column Fae (k-in) Moment at Column Fae (k-in) 11

12 2 Normalized Energy SPEC 1-N First Cyle SPEC 1-N Repeat Cyle SPEC 1-S First Cyle SPEC 1-S Repeat Cyle Story Drift (%) Figure 12: Normalized Energy Dissipation Capaity per Cyle for Speimen 1 The energy dissipation apaities of all three speimens for eah new yle to a speified drift level are ompared in Fig. 13 for loading in the spandrel beam diretion. Speimen 1, the speimen with the lower eentriity, had the highest energy dissipation apaity. This is also onfirmed with the wide hysteresis urves in lateral load versus story drift response of this speimen, whih did not show any pinhing (Fig. 8a). Speimen 2 experiened some pinhing due to higher eentriity, and thus had a lower energy dissipation apaity. Speimen 3, whih had a lak of onfinement in the joint region due to the use of a wide normal beam, had the lowest energy dissipation apaity. For Speimen 1, the dissipated energy per yle inreased with eah new yle, while for the last two speimens the energy dissipation inreased up to 4.% story drift level, then remained onstant until the end of the test Normalized Energy SPEC 1-S First Cyle SPEC 2-S First Cyle SPEC 3-S First Cyle Story Drift (%) Figure 13: Comparison of the Normalized Energy Dissipation Capaity per Cyle 12

13 Stiffness Deterioration The rate of stiffness deterioration is a measure of seismi performane of the onnetions. The stiffness of the speimens was omputed as a peak-to-peak seant stiffness by using the maximum displaement and orresponding lateral load at eah yle. Then, the average values for stiffness in positive and negative loading diretions were omputed and they were normalized with respet to the average peak-to-peak stiffness of the first yle to 1% story drift to aount for different speimen parameters. Fig. 14 shows the normalized average stiffness versus story drift response of the speimens for loading in the spandrel beam diretion. From this figure, it an be observed that the rate of stiffness deterioration was approximately the same for all speimens and at the end of the tests they had lost 75 to 85 perent of their initial stiffness. Speimen 1, whih had the lower eentriity and minor damage, lost 75 perent of its initial stiffness. Speimen 2, with a higher eentriity, and Speimen 3, with a wide beam, lost higher perentages of their initial stiffness. For loading in the normal beam diretion, the general trend was the same, but the speimens lost only 6 to 7 perent of their initial stiffness beause onentri beams were used instead of eentri ones Normalized Stiffness SPEC 1-S SPEC 2-S SPEC 3-S Story Drift (%) Figure 14: Normalized Average Peak-to-Peak Stiffness versus Story Drift Response of Speimens CONCLUSIONS The effet of eentriity on the seismi behavior of exterior beam-to-olumn onnetions was investigated in this experimental program. Three approximately 3/4-sale exterior reinfored onrete beam-olumn-slab onnetions were tested under reversed yli loading. Two tests were performed on eah speimen, first the lateral load was applied in the spandrel beam diretion, then the speimen was rotated 9 degrees and the load was applied in the normal beam diretion. The major parameters for this investigation are the eentriity of the spandrel beam with respet to the entroidal axis of the olumn, olumn setion aspet ratio, and normal beam width. Speimen 1 was a ontrol speimen designed aording to the ACI ode requirements [1, 2] with a square olumn, regular sized beams, and lower eentriity. Speimen 2 had a higher eentriity and a retangular olumn with regular sized beams. In Speimen 3, a wide normal beam was used with a retangular olumn and the level of joint stress was inreased. 13

14 Experimental results on these eentri beam-olumn-slab speimens demonstrated that inluding the floor system with the slab, spandrel, and normal beams adds onsiderable torsional stiffness to the subassembly and delays the deterioration of the joint shear stiffness and strength. In spite of the high eentriity levels, nominal moment apaity of the spandrel beams was reahed in all the tests. The measured moment apaity of normal beams were very lose to the design values for the first two tests, although the apaity was reahed at higher drift levels due to the redued stiffness of the subassembly resulting from the prior loading in the spandrel beam diretion. The softening of the joint region due to prior loading did not signifiantly affet the joint shear strength. In highly eentri speimens, diagonal shear raks were observed primarily within the ore region of the joint. Therefore, the olumn ore dimension rather than the full olumn width should be taken as the development length for the spandrel beam bars in eentri beam-to-olumn onnetions. For onnetions in wide-beam strutures, additional onfinement reinforement is required to prevent onrete rushing and loss of anhorage for the wide beam bars that are not plaed within the olumn. For joints with retangular olumns, it was observed that as long as the olumn setion aspet ratio (width vs. depth) was kept less than or equal to 1.5, the entire setion of the olumn worked to resist the joint shear stresses applied by the floor system. ACKNOWLEDGEMENT This researh study was sponsored by the National Siene Foundation under the Grant No. CMS The onlusions ontained in this paper are those of the authors and do not neessarily represent the view of the sponsor. REFERENCES 1. ACI-ASCE Committee 352, Reommendations for Design of Beam-Column Connetions in Monolithi Reinfored Conrete Strutures, ACI 352-R1, Amerian Conrete Institute, Farmington Hills, Mihigan, ACI Committee 318, Building Code Requirements for Strutural Conrete, ACI , Amerian Conrete Institute, Farmington Hills, Mihigan, Raffaelle, G.S., and Wight, J.K., Reinfored Conrete Eentri Beam-Column Connetions Subjeted to Earthquake-Type Loading, ACI Strutural Journal, Vol. 92, No. 1, pp , Lawrene, G.M., Beattie, J.H., and Jaks, D.H., Cyli Load Performane of an Eentri Beam Column Joint, Central Laboratories Report , Central Laboratories, Lower Hutt, New Zealand, Arai-Gumi Tehnial Researh Institute, Speial Issue Investigation Report on the 1995 Hyogen- Nambu Earthquake, Arai Tehnial Researh Report, Hyogo, Japan, Ohno, K., and Shibata, T., On the Damage to the Hakodate College by the Tokahioki Earthquake, 1968, Proeedings of the U.S.-Japan Seminar on Earthquake Engineering with Emphasis on the Safety of Shool Buildings, pp , Burak, B., Wight, J. K., Seismi Behavior of Eentri Reinfored Conrete Beam-Column-Slab Connetions under Sequential Loading in Two Prinipal Diretions, Proeedings, ACI Fifth International Conferene on Innovation in Design with Emphasis on Seismi, Wind and Environmental Loading; Quality Control and Innovation in Materials/Hot Weather Conreting, SP 29, Canun, Mexio, pp ,