Beam-Column Connections. Joint shear strength - code-conforming joints - Joint damage in previous eq. φ = Force demands on joint

Transcription

1 Beam-Column Connetions Fore demands on joint T s1 = 1.2A s f y C 2 = T s2 V b1 V b2 Dawn Lehman John Stanton and Laura Lowes Uniersity of Washington, Seattle Jak Uniersity of California, Berkeley l M pr V p M pr V p (a) moments, shears, axial loads ating on joint w C 1 = T s2 T s2 = 1.2A s f y (b) internal stress resultants Beam ating on joint l nb T s1 C 2 V u =V j = T s1 + C 1 - () joint shear M pr V Joint shear strength - ode-onforming joints - Current ACI seismi design proisions V u = φ V = φγ n φ =.8 Values of γ (ACI 32) Classifiation /type f b h interior exterior orner ont. olumn j φ V > V n V = γ f ( psi) A n j V u alulated using 1.2f y h /d b > 2 u Column Ties Continuous Through Joint ACI 32 Roof ACI Older-type beam-olumn onnetions Joint damage in preious eq. 1

2 -2. E -1. E+ CSL VL TST CST VC Vj TSR Seismi ealuation proess Seismi ealuation proess: Behaior SELECT PERFORMANCE OBJECTIVE Seismi Hazard Leel + Performane Leel DEMAND ASSESSMENT DEMAND/PERFORMANCE RELATIONSHIPS γ + = Experimental studies of older joints Damage progression Interior joint No joint ties Bars grooed h /d /d b = b 2 2 2/3 of of full sale P/(A g f g f ) =.1.1 Study Parameters Joint Shear Stress Displaement History % Drift 3% Drift % 4 Drift 6 Column Shear (K) Damage at % drift Standard Loading Impulsie Loading Influene of joint shear stress Low Demand Intermediate Demand High Demand PEER-8 PEER-99 PEER-41 Alire, 2

3 Joint shear demand Effet on response Joint shear strength Effet on damage mode and yli apaity Joint Stress (psi) Yield Yield Drift Ratio (%) Joint strength losely linked to beam flexural strength Plasti deformation apaity higher for lower joint shear Alire,.4.3 /f.2 j Alire, Lehman and Stanton Joint Shear Failure Joint failure without yielding near 2. f Failure fored into beams between 8. f and 11 f.1 Beam Hinging/ Beam Bar Slip Λ Damage progression exterior onnetions Exterior joint hook detail hook bent into joint Pantelides, 22 hook bent out of joint Joint behaior exterior onnetions 1 joint f Drift, % 2 Clyde 6 Clyde 4 Clyde Clyde Pantelides 6 Pantelides 6 Hakuto Priestley longitudinal Priestley transerse bidiretional loading Unreinfored Joint Strength FEMA 36 speifies the following: V j joint geometry = γ f bh γ No new data. Probably still alid. Assuming bars are anhored in joint, strength limited by strength of framing members, with upperbound of γ 1. For 1 γ 4, joint failure may our after inelasti response. For γ 4, joint unlikely to fail. Assuming bars are anhored in joint, strength limited by strength of framing members, with upper bound of γ 2. For 2 γ 8, joint failure may our after inelasti response. For γ 8, joint unlikely to fail. 3

4 Seismi ealuation proess: Demand/apaity assessment Ealuation of FEMA-36 model interior onnetions Joint Shear Fator FEMA PEER-14 6 CD1-14 CD PADH-14 PEER-22 2 CD3-22 PADH Joint Shear Strain Alire, Contributions to drift interior onnetions 12 Simulation models: simple spring Perent Contribution Speimen CD1-14 Column Beam Bar Slip Joint Shear Cyle Number Joints shall be modeled as either stiff or rigid omponents. (FEMA 36) Alire, Lehman and Stanton Gse/Gel Seant Shear Modulus of Joint.3 Craking.3 Yielding.2 Spalling Shear Stress Demand (MPa) Suggested enelope relation interior onnetions with ontinuous beam bars Suggested enelope relation exterior onnetions with hooked beam bars joint 2 f stiffness based on effetie stiffness to yield:.3.g strength = beam strength but not to exeed 2 f joint 2 f stiffness based on effetie stiffness to yield strength = beam strength but not to exeed 12 f onnetions with demand less than 4 f hae beam-yield mehanisms and do not follow this model axial-load stability unknown, espeially under high axial loads 4

5 Simulation models: simple spring Simulation models: maro-element Column shear (k) Column shear (k) Column shear (k) Yield of Beam 6 Longitudinal Reinforement Anderson, Lehman and Stanton Yielding Craking PEER 14 Initial Spalling PEER 14 Inelasti Damage Pts Rigid CD3 14 Inelasti Damage Pts eyl Initial Spallin g Joint Shear Stress (ksi) Anderson, Lehman and Stanton Joint Shear Strain (radians) CD1-14 Model Seismi Ealuation Proess: Performane Models Plasti drift apaity (2% loss in lateral strength) DEMAND/PERFORMANCE RELATIONSHIPS TST CST VC joint 3 f 2 2 Interior Exterior γ CSL VL + Vj TSR = plasti drift angle Note: the plasti drift angle inludes inelasti deformations of the beams Methods of repair (MOR) Fragility relations for interior joints MOR1 Repair finishes rak width <.2 in Pagni and Lowes MOR2 Epoxy Injetion rak width.2 in. MOR3 Pathing Spalling < 8% of jt. area MOR4 Replae Conrete Spalling > 8% of jt. area Probability of Requiring a MOR Cosmeti repair MOR Epoxy.3 injetion MOR Pathing 1.2 MOR 2 MOR Replae 3 onrete.1 MOR Replae 4 joint Pagni and Lowes

6 EDP for MOR MOR1 MOR2 MOR3 MOR4 Repair Finishes Epoxy Injetion Pathing Replae Conrete Mean Drift Ratio*.% 1.3% 2.4% 3% * Inludes drift resulting from beam and olumn deformations Pagni and Lowes Summary Typially, strength of sub-assemblage depends on flexural strength of beam or olumn and joint performane is not limited by joint shear stress apaity Inrease in joint shear stress demand leads to derease in deformation apaity: Drift ratios range from 4% (1 f ) to 2.% (2 f ) for interior joints. Drift apaity for exterior joints also depend on the anhorage detail Summary Joints are not rigid. Equialent elasti stiffness alues from G (prior to raking);.3g to.g (yield). Additional flexibility from anhorage ondition (i.e. bar slip) To model yli degradation, adaned hystereti models needed for joint shear and anhorage On aerage, repair of an interior joint needed at the following drift ratios: 1.% : epoxy injetion 2.% : path oer onrete 3.% : replae onrete Referenes Clyde, C., C. Pantelides, and L. Reaeley (2), Performane-based ealuation of exterior reinfored onrete building joints for seismi exitation, Report No. PEER-2/, Paifi Earthquake Engineering Researh Center, Uniersity of California, Berkeley, 61 pp. Pantelides, C., J. Hansen, J. Nadauld, L Reaeley (22, Assessment of reinfored onrete building exterior joints with substandard details, Report No. PEER-22/18, Paifi Earthquake Engineering Researh Center, Uniersity of California, Berkeley, 13 pp. Park, R. (22), "A Summary of Results of Simulated Seismi Load Tests on Reinfored Conrete Beam- Column Joints, Beams and Columns with Substandard Reinforing Details, Journal of Earthquake Engineering, Vol. 6, No. 2, pp Priestley, M., and G. Hart (1994), Seismi Behaior of As-Built and As-Designed Corner Joints, SEQAD Report to Hart Consultant Group, Report #94-9, 93 pp. plus appendies. Walker, S., C. Yeargin, D. Lehman, and J. Stanton (22), Influene of Joint Shear Stress Demand and Displaement History on the Seismi Performane of Beam-Column Joints, Proeedings, The Third US- Japan Workshop on Performane-Based Earthquake Engineering Methodology for Reinfored Conrete Building Strutures, Seattle, USA, August 21, Report No. PEER-22/2, Paifi Earthquake Engineering Researh Center, Uniersity of California, Berkeley, pp Hakuto, S., R. Park, and H. Tanaka, Seismi Load Tests on Interior and Exterior Beam-Column Joints with Substandard Reinforing Details, ACI Strutural Journal, Vol. 97, No. 1, January 2, pp Beres, A., R.White, and P. Gergely, Seismi Behaior of Reinfored Conrete Frame Strutures with Nondutile Details: Part I Summary of Experimental Findings of Full Sale Beam-Column Joint Tests, Report NCEER-92-24, NCEER, State Uniersity of New York at Buffalo, Pessiki, S., C. Conley, P. Gergely, and R. White, Seismi Behaior of Lightly-Reinfored Conrete Column and Beam Column Joint Details, Report NCEER-9-14, NCEER, State Uniersity of New York at Buffalo, 199. ACI-ASCE Committee 32, Reommendations for Design of Beam-Column Connetions in Monolithi Reinfored Conrete Strutures, Amerian Conrete Institute, Farmington Hills, 22. Referenes (ontinued) Fragility funtions: Pagni, C.A. and L.N. Lowes (26). Empirial Models for Prediting Earthquake Damage and Repair Requirements for Older Reinfored Conrete Beam-Column Joints. Earthquake Spetra. In press. Joint element: Lowes, L.N. and A. Altoontash. Modeling the Response of Reinfored Conrete Beam-Column Joints. Journal of Strutural Engineering, ASCE. 129(12) (23): Mitra, N. and L.N. Lowes. Ealuation, Calibration and Verifiation of a Reinfored Conrete Beam- Column Joint Model. Journal of Strutural Engineering, ASCE. Submitted July 2. Anderson, M.R. (23). Analytial Modeling of Existing Reinfored Conrete Beam-Column Joints MSCE thesis, Uniersity of Washington, Seattle, 38 p. Analyses using joint model: Theiss, A.G. Modeling the Response of Older Reinfored Conrete Building Joints. M.S. Thesis. Seattle: Uniersity of Washington (2): 29 p. Experimental Researh Walker, S.*, Yeargin, C.*, Lehman, D.E., and Stanton, J. Seismi Performane of Non-Dutile Reinfored Conrete Beam-Column Joints, Strutural Journal, Amerian Conrete Institute, aepted for publiation. Walker, S.G. (21). Seismi Performane of Existing Reinfored Conrete Beam-Column Joints. MSCE Thesis, Uniersity of Washington, Seattle. 38 p. Alire, D.A. (22). "Seismi Ealuation of Existing Unonfined Reinfored Conrete Beam-Column Joints", MSCE thesis, Uniersity of Washington, Seattle, 2 p. Infrastruture Reiew Mosier, G. (2). Seismi Assessment of Reinfored Conrete Beam-Column Joints. MSCE thesis, Uniersity of Washington, Seattle. 218 p. 6