Examination of code performance limits for shear walls

Transcription

1 Examination of code erformance limits for shear alls Đ. Kazaz Deartment of Civil Engineering, Atatürk University, Erzurum, Turkey P. Gülkan Deartment of Civil Engineering, Çankaya University, Ankara, Turkey A.Yakut Deartment of Civil Engineering, Middle East Technical University, Ankara, Turkey SUMMARY Recently roosed changes to modeling and accetance criteria in seismic regulations for both flexure and shear dominated reinforced concrete structural alls suggest that a comrehensive examination is required for imroved limit state definitions and their corresonding values. This study utilizes a ell calibrated modeling tool to investigate the deformation measures defined in terms of lastic rotations and local concrete and steel strains at the extreme fiber of rectangular structural alls. We comare requirements in ASCE/SEI 41, Eurocode 8 and the Turkish Seismic Code. This ay, a critical evaluation of the requirements embedded in these documents becomes ossible. It is concluded that the erformance limits must be refined by introducing additional arameters. Significant recommendations are rovided for Eurocode 8 and the Turkish Seismic Code. Keyords: Performance limit, lastic rotation, shear all, codes, analytical resonse. 1. INTRODUCTION Provisions for erformance assessment of reinforced concrete structures, such as FEMA356 (2000), Eurocode 8 (EC8-3, 2005) and ASCE/SEI 41 (2006) include deformation limits for both flexure and shear controlled all members at secific limit states to estimate the erformance of comonents and structures. The criteria are defined in terms of lastic hinge rotations and total drift ratios for the governing behavior modes of flexure (ductile members) and shear (brittle members), resectively. Recently, strain limits are defined for concrete in comression and steel in tension at serviceability and damage-control limit states as a vital comonent of direct dislacement-based design rocedures (Priestley et al., 2007). The recently revised Turkish Seismic Code (TSC-07, 2007) secifies limiting strain values associated ith different erformance levels. On one side deformations are secified in relation to global arameters, and on the other side local damage indicators in terms of strain limits are used to determine the exected erformance. For results of nonlinear ushover analyses to be evaluated according to either of the accetance criteria, hether the local and global resonse ill imly similar erformance states is a matter that must be established. Another criticism raised against the rotations associated ith different limit states is that they may turn out to be loer than the actual rotations exected to develo in reinforced concrete sections, so they are unduly conservative. In this study the adequacy of the limits secified by codes and guidelines is investigated. We emloy nonlinear finite element analysis for reinforced concrete structural alls that has been thoroughly verified by the benchmark roblems in Kazaz (2010). The absence of comrehensive exerimental data due to limitations in the exerimental setus and accuracy of the analytical rocedures in redicting reinforced concrete local resonse under varying stress conditions because of the inherited inadequacy of lane section hyothesis for alls necessities such study. 2. CODE PERFORMANCE LIMITS Fig.1 shos the concetualized force versus deformation curve used in ASCE/SEI 41, TSC-07 and EC8-3 to secify member modeling and accetance criteria for deformation-controlled actions. Three discrete Comonent Performance Levels and to intermediate Comonent Performance Ranges are 1

2 defined as shon in Fig. 1 to identify the erformance level of a member. As indicated in Fig. 1, at the Collase Prevention level (CP) member deformation caacities are taken at ultimate strength or at lateral dislacement demand at hich caacity begins to raidly degrade for rimary comonents. At the Life Safety level (LS), member deformation caacities are reduced by a (safety) factor of 4/3 over those alying at Collase Prevention. For the Immediate Occuancy (IO) to definitions arise in reference to Fig. 1. While ASCE/SEI 41 and TSC-07 anticiate some degree of nonlinear deformation beyond the global yield for the immediate occuancy level and minimum damage, resectively, EC8-3 adots the global yield oint as the limit state for the damage limitation on the member. Abbreviations: ASCE/SEI 41 IO: Immediate Occuancy LS: Life Safety CP: Collase Prevention Eurocode 8 (EC8) DL: Damage Limitation SD: Significant Damage NC: Near Collase TSC-07 MD: Minimum Damage Limit SL: Safety Limit CL: Collase Limit 2.1. ASCE/SEI 41 erformance limits Figure 1. Comonent erformance levels ASCE/SEI 41 basically adots the same erformance limits roosed in the all rovisions of FEMA 356 for the seismic assessment and rehabilitation of existing buildings. For alls deforming inelastically under lateral loading governed by flexure, the rotation (θ ) over the lastic hinging region at the base of member is used. For shear alls hose inelastic resonse is controlled by shear, the deformation limits are exressed in terms of the lateral drift ratios. For multi-story shear alls the drift shall be the story drift. Table 1 gives the ASCE/SEI 41 lastic rotation limits for members controlled by flexure here P/P o is the axial load ratio and v is the maximum average shear stress in the member normalized ith resect to concrete comressive strength f c. Here V max is the maximum shear force carried by the member. ASCE/SEI 41 (2006) adots the ACI (2002) requirements for the definition of a confined boundary Eurocode 8 Table 1. Plastic rotation limits for shear all members controlled by flexure in ASCE/SEI 41 Accetable Plastic Hinge Rotation (radians) Performance Level IO LS CP ' ( As As ) f y + P V m a x ν = Confined ' ' tl fc t L f c boundary (3) * Yes (6) * Yes (3) * Yes (6) * Yes *The values in arentheses are in si The deformation caacity of beam-columns and alls is defined as the chord rotation θ, i.e., the angle beteen the tangent to the axis at the yielding end and the chord connecting that end ith the end of the shear san (L v = M/V = moment/shear), i.e., the oint of contra-flexure. The chord rotation is also equal to the element drift ratio, i.e., the deflection at the end of the shear san divided by the length. The state of damage in a member is defined in EC8-3 by three Limit States. 2

3 Limit State of Near Collase (NC): The value of the lastic art of the chord rotation caacity at ultimate θ um of concrete members under cyclic loading may be calculated from the folloing exression: θ l um max(; ) = γ el max(; ω) h y ' αρsx v ω 0.2 L v f c 100ρd ( ) fc ( ) f (2.1) here γ el = 1.8 for rimary elements and 1.0 for secondary elements, h = deth of cross-section, ν=n/bhf c (b idth of comression zone, N axial force ositive for comression), ω and ω = reinforcement ratio of the longitudinal tension (including the eb reinforcement) and comression reinforcement, resectively, f c is the concrete comressive strength (MPa), ρ sx =A sx /s h b = ratio of transverse steel arallel to the direction x of loading (s h = stirru sacing), ρ d = steel ratio of diagonal reinforcement (if any), in each diagonal direction, α= confinement effectiveness factor. In alls the value given by Eqn. 2.1 is multilied by Limit State of Significant Damage (SD): The chord rotation caacity corresonding to significant damage θ SD may be assumed to be 75% of the ultimate chord rotation θ um given by Eqn Limit State of Damage Limitation (DL): The deformation caacity for this limit is given by the chord rotation at yielding θ y, evaluated for alls using the folloing equation Lv + αvz h db f θ y = φy φ y 3 Lv f c y (2.2) here φ y is the yield curvature and α V z is the tension shift of the bending moment diagram, d b is the (mean) diameter of the tension reinforcement, z is the internal lever arm, taken equal to 0.8L in alls ith rectangular section, α v should be set equal to 1 if shear cracking is exected to recede flexural yielding, otherise α v =0.0. The first term in the above exressions accounts for flexure, the second term for shear deformation and the third for anchorage sli of bars Turkish Seismic Code limit states In a erlexing divergence from either of these to aroaches the Turkish Seismic Code secifies strain limits to evaluate the erformance of reinforced concrete members. Concrete and steel strain limits at the fibers of a cross section for minimum damage limit (MD) are given as (ε cu ) MD = 35 ; (ε s ) MD = 0 (2.3) Concrete and steel strain limits at the fibers of a cross section for safety limit (SL) are (ε cg ) SL = (ρ s /ρ sm ) 35 ; (ε s ) SL = 0 (2.4) and for collase limit (CL) they are secified as (ε cg ) CL = (ρ s /ρ sm ) 8 ; (ε s ) CL = (2.5) In Eqns. 2.3 to 2.5, ε cu is the concrete strain at the outer fiber, ε cg is the concrete strain at the outer fiber of the confined core, ε s is the steel strain and (ρ s /ρ sm ) is the ratio of existing confinement reinforcement at the section to the confinement required by the Code. The limits utilized in TSC-07 are mostly based on the studies and roosals of Priestley et al. (2007), here strain limits for tension and comression in relation to serviceability and damage-control limit states to be used in moment-curvature analysis are listed. 3

4 3. ANALYTICAL FRAMEWORK Idealized cantilever models ere used in the comutations. Instead of an inverted triangular load distribution mimicking the first mode resonse, a oint load alied at the effective height (~2H /3) as used as shon in Fig. 2a. The effective height in such case is also referred as shear san (L v ). Trial analysis of cantilever alls under monotonically increasing uniform and inverted triangular load atterns demonstrated that even hen cracking may extend u to mid-height of the all, significant steel yielding extends over only loer one or to stories. The uer stories can be effectively treated as a cracked beam. Using this analogy the finite element model dislayed in Fig. 2b as develoed in the general urose finite element code ANSYS (2007) to reduce the comutation time. The first to stories of the cantilever all ere discreticized ith solid continuum elements hereas the uer stories are modeled ith Timoshenko beam elements. The nonconformance beteen the nodal degrees of freedom of beam and solid elements as overcome by roviding the transition ith constraint elements. To define the behavior of beam elements generalized nonlinear section roerties ere used. The load deformation behavior of beam elements as assigned in the form of bilinear force-distortion angle (F-γ) and moment-curvature (M-φ) relation. The initial flexural rigidity as taken as 0.5EI. At the solid art of the model, the confined and unconfined stress-strain curves of the concrete are calculated ith Saatcioğlu and Razvi (1992) model. Uniaxial behavior of longitudinal and transverse steels as modeled ith a bilinear isotroic hardening using von Mises yield criterion. Modulus of elasticity of the steel material as taken as MPa. The yield stress and tangent modulus at the strain hardening as taken as 420 MPa and 1500 MPa, resectively. Using a strain hardening stiffness hels achieving a better convergence. Buckling of longitudinal reinforcement in the comression boundary element is modeled according to Dhakal and Maekaa (2002). Further details of the modeling aroach and verification test cases are given in Kazaz (2010). The variables of the arametric study are summarized belo. The arameters are Wall length (L ): 3 m, 5 m and 8 m. Effective shear san (L v ): 5 m, 6 m, 9 m, 15 m, 24 m. Wall boundary element longitudinal reinforcement ratio (ρ b ): 0.5, 1, 2, 4 ercent. Wall axial load ratio at the base (P/f c /A ):,, 0.1, 0.15, 0.5. a) V L L v ρ b P/f c /A Figure 2. a) Illustration of variables of the arametric study; b) Finite element model. The alls ere designed according to TSC-07 secifications. Concrete strength as taken as 25 MPa for all cases. Wall boundary elements ere assumed to extend over a region of 0.2L at the edges according to TSC-07. For any given combination of above arameters, such as all length (L ), ratio of boundary element longitudinal reinforcement area to the boundary region cross section area (ρ b ) and axial load ratio (P/P o ), the all yield moment (M y ) is calculated. In the folloing ste, using the secified shear san length (L v ) the design shear force as calculated (V d =M y / L v ). The ratio of the horizontal and vertical eb reinforcement is assumed to be nominally 25. If the factored shear 4

5 force (V e =λv d ) exceeds the shear safety limit calculated ith V n =A (0.65f ctd +ρ t.f yd ) according to TSC- 07, the required amount of eb horizontal reinforcement is recalculated emloying the same equation. Since codes secify that the amount of vertical reinforcement should not be less than the horizontal reinforcement in the eb, the same steel ratio of eb reinforcement is used in the vertical direction. As transverse reinforcement φ8/100 mm is used at the boundaries. If the ACI had governed the design, φ8 hoos at 85 mm sacing ould have been required as confinement steel at the boundary elements. In conclusion all boundaries can be considered as ell confined for TSC-07 and adequately confined for ACI Obviously confinement should be considered among the variables of the arametric study, but since this ould increase the analysis ermutations significantly, the study ill be limited to confined members. 4. RESULTS OF ANALYSES The method that is emloyed to evaluate the length of the lastic zone, L z, can be described as follos. Curvature rofile comuted from element strains calculated at the same height at the to all ends are used to determine the sread of lasticity along the all. The limiting yield curvature to determine the sread of lasticity along the all as calculated ith the exression φ y =2ε y /L, here ε y is the yield strain of the reinforcement (Priestley et al., 2007). The sketch in Fig. 3a illustrates the calculation of the base section curvature and rotation in a ay that is consistent ith ASCE/SEI 41. The rotations (θ b ), hich are assumed to reresent the rotation of the base section, are calculated just above the lastic zone length by using the vertical dislacements calculated at tensile and comressive edges in the same ro. The base curvature φ b is calculated by fitting a best line to the curvature rofile along the lastic zone length. The intercet of the best fit line equation is adoted as φ b. The resonse quantities of all models are resented at the three damage levels given above namely, global yield, ultimate and an intermediate damage level, i.e. life safety, defined as the ercentage of ultimate. In the analysis the ultimate oint is determined on the basis of one of the criteria defined as the oint on the load-deformation curve here strength dros abrutly or degrades to 85% of the ultimate strength (V max ), or the steel strain at the tension side exceeds ε s = 0.1, or the reinforcing bars at the comression side buckles (accomanied by significant crushing of concrete). On the other hand, the degrading effect of cyclic loading regimes on the stiffness and strength of reinforced concrete as not considered in the analyses carried out in this study. Vallenas et al. (1979) roosed that as a general rule the overall deformation caacity under a realistic ground motion could be exected to be over 75 ercent of the deformation caacity under monotonic loading conditions. Tyical loaddeformation curve validating this assumtion is obtained from analyses of the RW2 all secimen tested by Thomsen and Wallace (1995) as dislayed in Fig. 3b. 75 ercent of the ultimate dislacement caacity of the analytical model analyzed statically agrees quite ell ith the ultimate dislacement caacity of exerimental secimen tested under cyclic loading regime. In conclusion, it is assumed that collase revention erformance level is taken at the 75 ercent of the ultimate oint of the finite element analyses in this study. Curvature rofile Best line fit y = c x + φ b y a) b) φ b x c θ b t θ b = L c t L z Figure 3. a) Schematic descritions of base curvature and rotation calculation, b) Tyical load-deformation curves of analyzed all models Load (kn) Thomsen&Wallace (1996) RW2 Secimen P F Deflection (mm) 0.75 ult Exerimental Cyclic Res. Calculated Cyclic Res. ult Calculated Monotonic Res. 5

6 Figs. 4 to 6 dislay the comarison of the calculated lastic rotation limits ith the limits secified in these documents. Data in each lot is also classified ith resect to axial load ratio as ell. Figs. 4(ab-c) comare ASCE/SEI 41 limits ith the calculated lastic rotation limits. At the immediate occuancy erformance level the ASCE/SEI 41 limits yield conservative estimations for medium and high axial load ratios, but for lo axial load ratios the limits are on the unsafe side. This situation contradicts exectations, yet it is the consequence of utilized rocedure in the calculation of lastic rotations. Analysis results indicate that hile yielding initiates at a concentrated region near the base of the all under lo axial load ratios, it has a distributed attern in alls subjected to high axial load ratios. Consequently the lastic region length is larger in high axial load cases yielding larger lastic rotations. At the collase revention erformance level, ASCE/SEI 41 limits are belo rad yielding conservative estimates. Hoever, it aears that a ca has been alied for greater values. The caed data falls into the region characterized by lo shear stress and flexural resonse. Since φ y =2ε y /L seems to yield good estimation of yield curvature the yield rotation according to ASCE/SEI 41 can be obtained as θ y =(2ε y /L )0.5L =21 rad assuming L =0.5L. ) ASCE 41 1e-2 8e-3 6e-3 4e-3 2e-3 Immediate Occuancy Life Safety Collase Prevention a) P / A f c <= 0.10 b) c) P / A f c = 0.15 P / A f c = e-3 4e-3 6e-3 8e-3 1e-2 Figure 4. Comarison of calculated lastic rotation limits ith the ASCE/SEI 41 limits The rotation limits resented in EC8-3 that are defined in terms of chord rotation differ from the rotations advocated in this study. In this study it is intended to obtain rotation limits that account for the member deformation characteristics ithin a story. The chord rotation cannot be reresentative of base rotation of shear alls under higher mode effects and alls interacting ith frames, esecially ith the strong ones. In order to be consistent ith EC8-3 definitions, chord rotations ere calculated and comared ith EC8-3 limits in Fig. 5. The chord rotation is calculated as the ti drift ratio using the flexural dislacement comonent. EC8-3 adots the yield oint as the damage limitation oint. Fig. 5a dislays the correlation of the yield rotation calculated using Eqn. 2.1 ith the element drift ratio calculated at the ti (roof) of cantilever finite element model. The inference of Fig. 5a is that the yield rotation given by Eqn. 2.1 significantly overestimates the analysis results, esecially as the shear-san-to-all-length ratio increases. No ronounced effect of axial load ratio is observed on the yield rotation. The order of yield rotations calculated according to EC8-3 ranging from 3 to 9 rad is high for stiff shear all elements. The yield rotation limits roosed by EC8-3 are unconservative for shear alls esecially hen the shear-san-to-all-length ratio is high. (θ y ) ECS 1e-2 8e-3 6e-3 4e-3 Damage Limitation Significant Damage Near Collase a) b) P / A f c <= 0.10 c) M/V/L > 3.5 ) ECS P / A f c = 0.15 P / A f c = e-3 0 For damage limitation EC8 uses yield rotation 0 2e-3 4e-3 6e-3 8e-3 1e-2 (θ y Figure 5. Comarison of calculated lastic rotation limits ith the lastic chord rotation limits in EC8-3 6

7 Eqn. 2.2 roosed in EC8-3 used to calculate the ultimate limit state lastic rotation yields conservative, yet unrealistic limits as shon in Fig. 5c. The equations seem to be insensitive to the most of the design arameters, excet the shear-san-to-all-length ratio and axial load ratio. The resulting lastic rotation limits vary beteen 6 rad to 9 rad in average. The lastic rotation limits calculated according to EC8-3 are observed to be smaller than the ones given in ASCE/SEI 41, hich is contrary to the exectations. EC8-3 defines chord rotation ith resect to shear-san (M/V) as oosed to the lastic rotation in ASCE41 defined over the lastic hinge region. The life safety limits are calculated as ¾ of collase revention limits as shon in Fig. 5b. 1e-2 8e-3 Minimum Damage Safety Limit Collase Limit a) b) c) ) TSC 6e-3 4e-3 P / A f c <= e-3 P / A f c = P / A f c = e-3 4e-3 6e-3 8e-3 1e-2 Figure 6. Comarison of calculated lastic rotation limits ith the TSC-07 limits Fig. 6 dislays the correlation of lastic rotation limits calculated according to strain limits given in TSC-07 using section based moment-curvature analysis ith the lastic rotations calculated from the analytical model. The lastic hinge length as taken as 0.5L as roosed by TSC-07 in the calculation of lastic rotations from the curvatures from section analyses. For all damage states (or erformance levels) TSC-07 overestimates the rotation significantly ithout shoing remarkable variation. The horizontally extending trend in Figs. 6(a-b-c) reflects that the given TSC-07 limits fall short of redicting the variation in the rotation due to varying design arameters. As discussed reviously the same is also valid for EC8-3. The average limit curvatures in dimensionless form for serviceability (φ s L ) and damage control (φ dc L ) states ere roosed as 75 and 0.072, resectively, by Priestly et al. (2007). The rocedure imlemented in TSC-07 for the seismic assessment results in rotations as θ MN =0.5φ s L =875 rad for minimum damage and θ GÇ =0.5φ dc L =6 rad for collase limit. These limits are consistent ith hat is resented in Fig. 6, yet insufficient to calculate the actual rotations for a range of alls. 5. DISCUSSION The analysis results suggest that the deformation caacity of structural alls ith confined boundary elements is larger than the limits given in ASCE/SEI 41 rovisions. It is seen that ASCE/SEI 41 yields conservative estimations of the structural erformance. On the other hand, if the strain based erformance criteria defined in TSC-07 or as suggested by Priestley et al. [4] is used in the determination of structural erformance, unconservative estimations of erformance are obtained for reinforced concrete rectangular alls. Equations given in EC8-3 for calculating erformance based rotation limits lead to unconservative values at yield. The lastic rotation limits sho insignificant variation and aear to be inadequate in estimating the finite element results. It is orth noting that similar forms of equations are used for beams, columns and alls desite significant differences in their behavior ithin a structure. Fig. 7 dislays the loer bound lastic rotation limits of the data obtained from analysis at different erformance levels. In this figure, ASCE/SEI 41 limits are also dislayed for comarison. As seen here, the major differences are for limits in the immediate occuancy level and at lo and high shear stress ranges for the other to erformance levels. ASCE/SEI 41 limits are secified at 0.33 f c and 7

8 0.50 f c, here intermediate values can be obtained by linear interolation. Hoever, outside these limits e have little basis about hat the extraolated trend may be. The roosed limits for the lastic rotations of alls controlled by flexure are tabulated in Table 2. These limits are given as alternative values to Table 6.18 of ASCE/SEI 41 for conforming members summarized in Table 1. The limits are derived as a function of normalized shear stress (ν) and axial load level (P/P o ) for different ranges of these variables in order to obtain more accurate reresentation of lastic rotation limits at the secified erformance levels. Limits in relation to mid-range axial load levels (P/P o = 0.15) are also introduced to increase the accuracy of the assessment rocedure. In case the ASCE/SEI 41 format, i.e. numerical limit values at secific ν and P/P o, the under lined number corresonds to the existing ASCE/SEI 41 limit and the left side number is the value roosed by this study. θ This study P/P o <= 0.10 P/P o = 0.15 P/P o = 0.25 ASCE 41 a) b) c) d) e) f) Immediate occuancy θ Life Safety θ g) h) j) V max t L f c V max t L f c V max t L f c Colloase Prevention Figure 7. Loer bound lastic rotation limits at different erformance levels Alternative to limits roosed in Table 2, the loer bound lastic rotation limits can also be exressed ith a more general exonential exression as given in Eqn ν P Po e if P Po (1 3 / ). / 0.10 θ = ( P/ Po ) ν (1 3 P / Po ). e if P / Po > 0.10 (7.1) As seen in Fig. 7 the roosed values corresond to the loer bound limits of the collective results. Using the arameters that govern the resonse of shear alls a general equation is derived to estimate the rotation caacity of shear alls ith moderately confined boundary elements at ultimate. The equation from a regression analysis reads as 8

9 ( ) B ( ). C ν + e DL ( ) θ A ρ σ θ = m here σ ( θ ) b θ if θ rad 25 if 4 rad < θ rad = θ 19 if rad θ 8 rad < 0 if 8 rad < θ (7.2) here A, B, C and D are coefficients defined in Table 3 as a function of axial load ratio. σ ) is the standard deviation of the calculated lastic rotation limits defined as a function of lastic rotation. The folloing set of equations can be emloyed in the calculation of σ ). The limit obtained through Eqn. 7.2 is greater than the limits given in Table 2. The redictions disregarding standard deviation are comared ith the analytical results in Fig. 8. The redicted values agree quite ell ith the comutational results. If the redicted values are reduced by 0.75 the limits for life safety erformance level is obtained. P/Po 0.10 P/Po = 0.15 P/Po 0.25 Table 2. The roosed lastic rotation limits for shear all members controlled by flexure IO LS CP ν < 0.33 ν = ν 8-42ν 15 / 5 / 5-03ν 5 / < ν < ν 47-94ν ν > 0.50 ν = / 4 2-8ν 8 / ν / ν < ν 8-73ν 5-94ν ν = / 43 9 / 87 2 / < ν < ν 48-76ν 6-2ν ν > 0.50 ν = 0.50 ν < 0.33 ν = ν 2 / ν 25 / ν (6 / ν 7 / 6 6-2ν / 83-33ν 9 / < ν < ν 18-09ν 2-9ν ν > 0.50 ν = ν 2 / ν 5 / 3 2 9ν 75 / 5 (This study / ASCE/SEI 41) (underlined values corresonds to ASCE/SEI 41 limits) Table 3. Coefficients of Eqn. 7.2 to calculate the ultimate lastic rotation limit of structural alls P/P o A B C D = = Predicted by Eq R² = FEM rotation, θ SIM Figure 8. Correlation of redicted lastic rotations ith analysis results 9

10 6. CONCLUSIONS Nonlinear static or resonse history analysis rocedures are the tools ith hich the deformation resonse of structural comonents are estimated in dislacement based rocedures. Regardless of the method of analysis emloyed, local and global quantities in terms of internal forces and deformations form the basis of judgment. These are then used to assess erformance of structural assemblies. The most challenging art of the dislacement based assessment rocedures is the determination of the deformation limits that strongly influences the results. Therefore, the rimary objective of the study carried out as to evaluate the limits recommended by the most idely used codes and guidelines. The results of this study that ere obtained from comrehensive arametric analyses of the alls rovide the data to adequately test erformance based deformation limits secified in different documents. Among the documents evaluated, ASCE/SEI 41 limits ere observed to be the most accurate ones yielding conservative results at all levels excet the lo axial load levels. It as shon that neither EC8-3 nor TSC-07 secifies adequately consistent deformation limits. TSC-07 suggests unconservative limits at all erformance levels, and it aears to fall short of caturing the variation reflected in the calculated values. Likeise EC8-3 seems to fall short of reresenting the variation ith unconservative estimations at life safety and collase revention levels. This study rimarily focused on the lastic hinge rotation limits in three different seismic codes. Accurate mathematical exressions defining the lateral drift, base curvature and rotation limits at yield and ultimate damage states can be found in Kazaz et al. (2012). REFERENCES ANSYS R11.0. Sanson Analyses System, Building Code Requirements for Structural Concrete and Commentary. ACI American Concrete Institute, Detroit, Michigan, Dhakal RP, Maekaa K. Modeling for ostyield buckling of reinforcement. Journal of Structural Engineering (ASCE) 2002; 128(9): Eurocode 8: Design of Structures for Earthquake Resistance-Part 3: Assessment and Retrofitting of Buildings. BS EN Comité Euroéen de Normalisation, Brussels, Belgium, 2005, 89. Kazaz I. Dynamic characteristics and erformance assessment of reinforced concrete structural alls. Ph.D. Thesis, Civil Engineering Det., Middle East Technical University, Ankara, Turkey, Kazaz Đ, Gülkan P and Yakut A. Deformation limits for structural alls ith confined boundaries, Earthquake Sectra, (in Press), NEHRP Guidelines for the seismic rehabilitation of buildings. FEMA 356. Federal Emergency Management Agency, Washington DC, Priestley MJN, Calvi GM, Koalsky MJ. Dislacement-based seismic design of structures. IUSS Press, Pavia, Italy, Saatcioglu M, Razvi SR. Strength and ductility of confined concrete. Journal of Structural Engineering (ASCE) 1992; 118(6): Seismic rehabilitation of existing buildings. ASCE/SEI 41. American Society of Civil Engineers, Reston, Virginia, Thomsen JH, Wallace JW. Dislacement-based design of reinforced concrete structural alls: an exerimental investigation of alls ith rectangular and T-shaed cross-sections. CU/CEE-95/06, Det. of Civil and Environmental Engineering, Clarkson University, Potsdam, Ne York, Turkish Seismic Design Code for Buildings, Secification for Structures to be Built in Disaster Areas. TSC-07. Ministry of Public Works and Resettlement, Ankara, Turkey, Vallenas MV, Bertero VV, Poov EP. Hysteretic behavior of reinforced concrete structural alls. EERC Reort 79/20, Earthquake Engineering Research Center, University of California, Berkeley,